原文Behaviour of composite walls under monotonic and cyclic shear loading
tpo65三篇阅读原文译文题目答案译文背景知识
Tpo65全套阅读解析阅读-1 (1)原文 (2)译文 (3)题目 (5)答案 (9)背景知识 (10)阅读-2 (15)原文 (15)译文 (16)题目 (18)答案 (22)背景知识 (23)阅读-3 (24)原文 (24)译文 (26)题目 (27)答案 (31)背景知识 (32)阅读-1原文The Pit Organs of Snakes①It is thought that the facial pits or pit organs on the head of some snakes are specialized infrared(heat)receptors.When a rattlesnake strikes,the direction of the strike seems to be guided by the infrared radiation from its prey.A rattlesnake strikes only at warm-blooded prey,and when the prey is dead and at room temperature,the snake will not strike.However,a blindfolded snake strikes correctly at a dead rat that is pulled across the cage,provided the rat is warmer than the surroundings.Blindfolded,the snake cannot be guided by vision;nor is it guided by the sense of smell,for it will strike correctly even at a moving, cloth-wrapped electric bulb.The pit organs are evidently involved in sensing the location of warm objects.All snakes that have pit organs feed preferentially on warm-blooded prey,and this further supports the view that these organs are infrared sensors.In the rattlesnake the pit organs are located,one on each side, between the nostril and the eye;they are connected to many nerves,and this in itself suggests a sensory role for the organ.②The sensitivity of the facial pit has been examined by recording the activity in the nerve leading from the organ.A variety of stimuli,such as sound,vibration,or light of moderate intensity(with the infrared part of the spectrum filtered out),has no detectable effect on the activity in the nerve.However,if objects of a temperature different from the surroundings are brought into the receptive field around the head,there is a striking change in nerve activity,regardless of the temperature of the intervening air.③How is the infrared radiation sensed?The pit is covered by a thin transparent membrane,and it has been suggested that a rise in temperature in the pit behind the membrane could cause an expansion of the gas with a consequent deformation of the membrane.This in turn could be sensed by a suitable receptor. This hypothesis is highly improbable,for a cut in the membrane that opens the pit to the outside air causes no loss in responsiveness,a result that is incompatible with the hypothesis that a pressure change is sensed.④We are left with two other possibilities to consider:Either the effect is photochemical,which means that the infrared radiation is absorbed by a specificcompound,analogous to the light-sensitive pigments in the eye,or the pit organs are sensitive to the slight temperature rise caused when infrared radiation reaches it.The infrared radiation emitted from a mammalian body has low quantum energy, which makes any photochemical effect on a pigment extremely unlikely.Pure infrared radiation can be produced by a laser,and experiments with such radiation of known wavelength provide strong evidence that the mode of reception in the facial pit organ is entirely thermal.⑤Can the pit organs be used for perception of the infrared source in the way our two eyes are used for stereoscopic vision?This seems likely,not only from observations of the precision with which a snake can strike,but also from studies of its brain activity.When infrared radiation falls on the facial pit organ,electric activity can be recorded from the optic tectum,the part of the brain with which the optic nerve is connected.This in itself is suggestive;although the nerves from the pit organ are completely separate from the optic nerves,the same part of the brain seems to handle visual information,which is known to be stereoscopic,and infrared information.The optic tectum has left and right parts,located on either side of the brain.Each part receives input from each eye via the optic chiasma,the point at which the optic nerves from the left and right eye meet.Many of the neurons in the tectum respond to stimulation of the pit organ on the opposite side of the head.This is reminiscent of the way information from the eyes is handled; the crossover of the optic nerve in the optic chiasma is essential for stereoscopic vision and interpretation of rmation from the two pit organs is apparently coordinated and interpreted in a similar way,a conclusion in agreement with recorded changes in the neural activity in the tectum when the infrared source is in a position to irradiate both pits at once.It therefore appears that the facial pits indeed provide stereoscopic perception and substantially aid in the precision of estimating the location of prey.译文蛇的坑状器官①据认为,一些蛇面部的凹陷或头部的凹陷器官是特殊的红外(热)感受器。
博士研究生英语综合教程第二版
新编研究生英语系列教程博士研究生英语综合教程(第二版/教师用书)北京市研究生英语教学研究会主编陈大明徐汝舟副主编刘宁王焱华许建平编者赵宏凌邹映辉杨凤珍来鲁宁张剑柳君丽曹莉郑辉中国人民大学出版社KEY TO THE EXERCISESUnit One ScienceText 1 Can We Really Understand Matter?I. Vocabulary1. A2. B3. A4. C5. D6. B7. B8. CII. Definition1. A priority2. Momentum3. An implication4. Polarization5. the distance that light travels in a year, about 5.88 trillion miles or 9.46 trillion km.6. a contradictory or absurd statement that expresses a possible truth7. a device that speeds up charged elementary particles or ions to high energiesIII. Mosaic1. The stress: (Omitted)Pronunciation rule: An English word ended with–tion or –sion has its stress on the last syllable but one.2. molecule3. A4. B5. C6. B7. A8. AIV. TranslationA.(Refer to the relevant part of the Chinese translation)B.In September 1995, anti-hydrogen atom—an anti-matter atom—was successfullydeveloped in European Particle Physics Laboratory in Switzerland. After the startling news spread out, scientists in the West who were indulged in the research of anti-matter were greatly excited. While they were attempting to produce and store anti-matter as the energy for spacecraft, they raised a new question: Many of the mysterious nuclear explosions in the recent one hundred years are connected with anti-matter. That is to say, these hard-to-explain explosions are tricks played by anti-mat ter. They are the “destruction”phenomenon caused by the impact between matter and anti-matter.V. GroupingA.Uncertainty:what if, illusory, indescribable, puzzle, speculation, seemingly, in some mysterious wayB.Contrast:more daunting, the hardest of hard sciences, do little to discourage, from afar, close scrutiny, work amazingly wellC. Applications of Quantum mechanics:the momentum of a charging elephant, building improved gyroscopes1. probabilities2. illusory3. discourage4. scrutinyVI. Topics for Discussion and Writing(Omitted)WRITING•STRATEGY•DEFINITIONI. Complete the following definitions with the help of dictionaries.1. To bribe means to influence the behavior or judgment of others (usually in positions ofpower) unfairly or illegally by offering them favors or gifts.2. Gravity is defined as the natural force by which objects are attracted to each other,especially that by which a large mass pulls a smaller one to it.3. The millennium bug refers to the computer glitch that arises from an inability of thesoftware to deal correctly with dates of January 2000 or later.4. Globalization is understood as the development so as to make possible internationalinfluence or operation.II. Write a one-paragraph definition of the following words.1. hypothesisA hypothesis is an idea which is suggested as a possible way of explaining facts,proving an argument, etc. Through experiments, the hypothesis is either accepted as true (possibly with improvements) or cast off.2. scienceScience is defined as the intellectual and practical activity encompassing the systematic study of the structure and behavior of the physical and natural world through observation and experiment.3. superstitionSuperstition refers to a belief which is not based on reason or fact but on old ideas about luck, magic, etc. For example, it is a common superstition that black cats are unlucky.4. pessimismPessimism is a tendency to give more attention to the bad side of a situation or to expect the worst possible result. A person with pessimism is a pessimist who thinks that whatever happens is bad.5. individualismIndividualism is the idea that the rights and freedom of the individual are the most important rights in a society. It has a bad sense in that little attention is paid to the rights of the collective or a good one in that independence is emphasized rather than dependence on others.Text 2 Physics Awaits New Options as Standard Model IdlesI. Vocabulary1. C2. A3. B4. A5. C6. D7. D8. BII. Definition1. A refrain2. A spark3. A jingle4. Symmetry5. develops or studies theories or ideas about a particular subject.6. studies the origin and nature of the universe.7. studies the stars and planets using scientific equipment including telescopes.III. Mosaic1. gravity2. anti-/opposite3. D4. B5. A6. A7. B8.AIV. TranslationA.(Refer to the relevant part of the Chinese translation)B.The Standard Model of particle physics is an unfinished poem. Most of the pieces are there,and even unfinished, it is arguably the most brilliant opus in the literature of physics. With great precision, it describes all known matter – all the subatomic particles such as quarks and leptons –as well as the forces by which those particles interact with one another.These forces are electromagnetism, which describes how charged objects feel each other’s influence: the weak force, which explains how particles can change their identities, and the strong force, which describes how quarks stick together to form protons and other composite particles. But as lovely as the Standard Model’s description is, it is in pieces, and some of those pieces – those that describe gravity – are missing. It is a few shards of beauty that hint at something greater, like a few lines of Sappho on a fragment of papyrus. V. GroupingA.Particle physics:supersymmetry, equation, superpartners, stringB.Strangeness:bizarre, beyond the ken ofC.Antonyms:gravity–antigravity1. novelty2. revelatory3. Symmetry4. gravityVII. Topics for Discussion and Writing(Omitted)WRITING • STRATEGY• EXEMPLIFICATION AN D ILLUSTRATION(Omitted)Text 3 Supporting ScienceI. Vocabulary1. D2. C3. A4. C5. C6. A7. B8. A9. C 10. D 11. B 12. AII. Definition1. A portfolio2. A vista3. Cryptography4. Paleontology5. a business or an undertaking that has recently begun operation6. a group of people having common interests7. a person with senior managerial responsibility in a business organizationIII. Rhetoric1. pouring money into2. column3. unbridled4. twilight5. blossomed intoIV. Mosaic1. phenomenon criterion datum medium(because these words originated from Latin and retain their Latin plural form)2. A3. A4. B5. B6. B7. C8. BV. TranslationA.(Refer to the relevant part of the Chinese translation)B. The five scientists who won the 1996 Nobel Prize point out that the present prosperityand development are based on the fruits of basic scientific research and the negligence of basic scientific research will threaten human development of the 21st century.EU countries noticed that one of their weaknesses is “insufficient investment in research and development.” Korea and Singapore do not hesitate to pour money into research and development. The developed countries in the West have used most of the scientific and technological development resources for the research and development of new and high technology. This has become an obvious trend at present. It is evident from the experiences of various countries that new and high technology can create and form new industries, open up and set up new markets. The innovation of traditional industries with new and high technology is a key method to strengthen the competitive competency of an enterprise.VI. Grouping:A.Negligence of basic research:corporate breakups, cut back on research, ignore it, subject to a protracted dissection and review, second-guessing, dropped dramatically, subjected to a scrutiny, skirling our supportB.Significant examples of basic research:computing, biotechnology, the Internet, number theory, complex analysis, coding theory, cryptography, dinosaur paleontology, genetics research)C.Ways to intensify arguments:moved support for science from a “want to have” squarely into the “need to have”column1. resounding2. second-guessing3. downsized4. subjectedVII. Topics for Discussion and Writing(Omitted)WRITING • STRATEGY • COMPARISON, CONTRAST, AND ANALOGY (Omitted)Text 4 Why Must Scientists Become More Ethically Sensitive Than They Used to Be?I. Vocabulary1. B2. B3. A4. C5. B6. D7. D8. A9. D 10. B 11. B 12. DII. Definition1. A constraint2. Algorithm3. A prerequisite4. Ethics5. an important topic or problem for debate or discussion6. a person’s principles or standards of behaviour; one’s judgement of what is important inlife.7. a formal plan put forward for consideration to carry out a projectIII. Rhetoric1. brushed under the carpet2. smell3. hands and brains4. battle front5. module . . . moduleIV. Mosaic1. /z/ /s/ /s/ /z/ /s//s/ /iz/ /z/ /s/ /z//iz/ /z/ /s/ /z/ /z//z/ /s/ /s/ /z/ /z//s/ after voiceless consonants/z/ after voiced consonants/iz/ after a word ended with –es2. B3. D4. A5. D6. A7. CV. TranslationA.(Refer to the relevant part of the Chinese translation)B. Scientists and medical ethicists advocate the prohibition of human cloning as a way toproduce life. They all agree that human cloning exerts severe threats on human dignity.Social critics point out that cloned children will lack personality and noumenon. G. Annas, professor of health laws in Boston university, points out that “human cloning should be banned because it may fundamentally alter the definition of ourselves.”VI. Grouping:A.The change of attitudes towards ethical consideration:occupy media slots and Sunday supplements, latest battle front, can no longer be swept aside, more sensitiveB.Academic science:a worldwide institutional web, peer review, respect for priority of discovery,comprehensive citation of the literature, meritocratic preferment, smuggle ethical considerations from private life, from politics, from religion, from sheer humanitariansympathyC.Industrial science:intimately involved in the business of daily lifeD.Post-academic science:a succession of “projects”, compound moral risks with financial risks, largely the work ofteams of scientists1. individualistic2. energized3. comprehensive4. heterogeneousVII. Topics for Discussion and Writing(Omitted)WRITING • STRATEGY • CAUSE AND EFFECT(Omitted)Text 5 Beauty, Charm, and Strangeness: Science as MetaphorI. Vocabulary1. B2. A3. C4. B5. C6. B7. A8. B9. A 10. CII. Rhetoric1. pitch2. landscape3. unblinking4. yawn5. wringsIII. Mosaic1.physical poetic political scientific optical atomic2. (Omitted)3. B4. B5. A6. C7. DIV. TranslationA.(Refer to the relevant part of the Chinese translation)B. There are only two forms of human spiritual creation: science and poetry. The formergives us convenience; and the latter gives us comfort. In more common words, the former enables us to have food to eat when we are hungry; and the latter makes us aware that eating is something more than eating, and it is very interesting as well. To have science without poetry, atomic bomb will be detonated; to have poetry without science, poets will starve to death.Scientists should not despise poets; and poets should not remain isolated from scientists.If the two fields conflict each other, human beings would be on the way to doom. In fact, the greatest scientists like Newton, Einstein and Mrs. Currie were all endowed with poetic spirit.I assert that in observing the apple falling to the ground, Newton not only discovered thegravity of the earth, he also wrote a beautiful poem.V. GroupingA.Human reason:guilty of hubris, cramped imagination, commonsense logic, an ignorant manB.Differences between art and science:different in their methods and in their ends, a scientific hypothesis can be proven, new combinations of old materials, transform the ordinary into extraordinary, a practical extension into technology, the sense of an endingC.Similarities between art and science:in their origin, quest to reveal the world1. indistinguishable2. transform3. poetic4. extension5. subdueVI. Topics for Discussion and Writing(Omitted)WRITING • STRATEGY • DIVISION AND CLASSIFICATIONI. Organize the following words into groups.People: physician; driver; boxer; mother; teacherSchools: school; college; institute; kindergarten; universityColors: brown; purple; violet; black; yellowPrepositions: along; toward; upon; without; intoVerbs:listen; read; write; hear; lookII. Complete the following lists.1. College students can be classified according to:A.academic achievementB.attitude toward politics, friendship, etc.C.sexD.heightE.place of originF.value of lifeG.major2. Transportation means can be classified according to:A.speedB.sizeeD.fuelfortF.historyG.water, land, or airIII. Write a paragraph of classification on the books which you like to read.(Omitted)Text 6 Is Science Evil?I. Vocabulary1. C2. A3. D4. B5. B6.A7. C8. C9. D 10. AII. Definition1. Canon2. Validity3. A premise4. Disillusionment5. the process of establishing the truth, accuracy, or correctness of something6. a mode of thinking based on guessing rather than on knowledgeIII. Mosaic1. 1) / / illusion dis-=not -ment=noun ending2) / / science pseudo-=false3) / / conscious -ness=noun ending4) / / question -able=adjective ending5) / / extenuate -ation=noun ending6) / / indict -ment=noun ending7) / / rebut -al=noun ending8) / / perpetrate -ion=noun ending9) / / problem -ic=adjective ending10) / / dissolute -ion=noun ending2. Para. 13: Only when scientific criticism is crippled by making particulars absolute can aclosed view of the world pretend to scientific validity –and then it is a falsevalidity.Para.14: Out of dissatisfaction with all the separate bits of knowledge is born the desire to unite all knowledge.Para. 15: Only superficially do the modern and the ancient atomic theories seem to fit into the same theoretical mold.1) Para. 13: Only + adverbial clause of time + inverted orderPara. 14: Prepositional phrase + inverted orderPara. 15: Only + adverb + inverted order2) Inverted order is used to emphasize.3. C4. B5. A6. CIV. TranslationA.(Refer to the relevant part of the Chinese translation)B. At present there exist two conflicting tendencies towards the development of science andtechnology. The opponents of science hold that the development of modern science has not brought blessings to human beings, instead it has brought human beings to the very edge of disaster and peril. On the other hand, the proponents of scientific and technological progress maintains that the crises facing human beings today—such as environmental pollution, ecological unbalance, natural resource exhaustion—are the natural consequences of the development of science, and the solution to which lies in the further development of science. Both of the above tendencies are reasonable in a sense with their respective one-sided view. If we view the development of modern science and technology from the point of view of our times and with dialectic viewpoints, we can find out that the problem facing modern science and technology is not how to understand the progress of modern science and technology, but how to find out the theoretical basis for the further development of science and technology in order to meet the needs of the times.V. GroupingA.Attitudes toward science:expect to be helped by science and only by science, the superstition of science, the hatred of science, the one great landmark on the road to truthB.Characteristics of science:powerful authority, solve all problems, thoroughly universalC.Scientific knowledge:a concrete totality, cannot supply us with the aims of life, cannot lead usD.Contrast between ancient and modern science:progress into the infinite, making particulars absolute, not as an end in itself but as a tool of inquiry1. corruption2. totality3. inquiry4. superstition5. landmarkVI. Topics for Discussion and Writing(Omitted)WRITING • STRATEGY • GENERALIZATION AND SPECIFICATIONWRITING • STRATEGY • COMBINATION OF WRITING STRATEGIES (Omitted)Unit Two EngineeringText 7 Engineers’ Dream of Practical Star FlightI. Vocabulary1. D2. C3. B4. D5. A6. C7.CII. Definition1. Annihilation2. A skeptic3. A cosmic ray4. Anti-matter5. A workshop6. the curved path in space that is followed by an object going around another larger object7. any one of the systems of millions or billions of stars, together with gas and dust, heldtogether by gravitational attractionIII. Mosaic1. 闭音节, 字母u 发/ / 的音,如A, C and D.2. (Omitted)3. (Omitted)4. C5. C6. B7. A8. BIV. TranslationA.(Refer to the relevant part of the Chinese translation)B. Human beings have long been attempting sending unmanned devices, called interstellarprobes, into the outer space to understand the changes of climates, geological structures and the living beings on the stars and planets out there. A probe is usually sent into the orbit of the earth by “riding” a spacecraft or carrier rockets. After its orbital adjustments are made, the rocket engine is ignited and the probe continues its journey to the orbit of the other star or planet. With the rocket engine broken off, the probe immediately spreads its solar-cell sails and antenna, controlling its posture with sensors. When convinced that it is in the orbit of the targeted star, the probe starts its propeller and flies to the preset destination.V. GroupingA.Astronomical phenomena:interstellar medium, a wind of particles, galaxy, reserves of comets, the Kuiper Belt,orbit, Pluto, the Oort Cloud, the bombardment photonB.Space equipment:interstellar probe, gravitational lens, chemical rocket, thruster, reflective sailC.To explore the universe:scoop, bend, sampleD.Challenges and solutions in interstellar flights:carry its own supply of propellant, matter-antimatter, nuclear power1. gravitational2. propulsion3. probed4. interstellarVI. Topics for Discussion and Writing(Omitted)WRITING • RHETORIC • SIMILE AND METAPHORI. Complete the following similes with the words given, using one word once only.1. as drunk as a ___ bear 11. as cool as ___ cucumber______2. as faithful as a ___ dog_____ 12. as white as ____ snow ________3. as greedy as ____Jew_____ 13. as cunning as a ____ fox__________4. as rich as _____ king_____ 14. to fight like a ____ _lion_________5. as naked as a ___ frog_____ 15. to act like a stupid __ ass_________6. as red as a _ _lobster_ 16. to spend money like __ water_______7. as beautiful as a _ butterfly__ 17. to eat like a _ wolf________8. as busy as a ____ bee______ 18. to sleep like a _____ log ______9. as firm as a ____ rock _____ 19. to swim like a ____ fish________10. as rigid as a ___stone____ 20. to tremble like a _____ _ leaf_________II. Explain the following metaphors.1. Creaking doors hang the longest.creaking door: anything or anybody in a bad condition2. I could hardly put up with his acid comment.acid comment: bitter remark.3. Her eyes were blazing as she stormed at me.blazing: filled with angerstormed: shouted; screamed4. She burnt with love, as straw with fire flames.burnt with love: extremely excited with love5. The talk about raising taxes was a red flag to many voters.a red flag: a danger signal (that might stop the support of many voters)6. The charcoal fire glowed and dimmed rhythmically to the strokes of bellows.glowed and dimmed: became bright and gloomy7. The city is a jungle where nobody is safe after the dark.a jungle: a disorderly place8. To me he is power—he is the primitive, the wild wolf, the striking rattlesnake, thestinging centipede.the primitive, the wild wolf, the striking rattlesnake, and the stinging centipede: the most terrifying creatureText 8 Blinded By The LightI. Vocabulary1. A2. C3. A4. C5. D6. A7. BII. Rhetoric1. riveted2. pack3. pours4. creepsIII. Mosaic1. 开音节发字母读音, 如A, B and C.2. (Omitted)3. (Omitted)4. C5. D6. D7. C8. AIV. TranslationA.(Refer to the relevant part of the Chinese translation)B. The energy released from nuclear fusion is much more than that from nuclear fission, andthe radioactivity given out from fusion is only one hundredth of that from fission. The major fuel used for nuclear fusion is hydrogen and its isotopes, deuterium and tritium, among which deuterium could be directly extracted from sea water. The energy of deuterium contained in one liter of sea water is equal to 300 liters of petroleum. In the ocean there are about 35,000 billion tons of deuterium, which could be used for more than one billion years. Compared to the fission energy, the fusion energy on the earth is nearly limitless.V. GroupingA. Nuclear-fusion:the doughnut-shaped hollow, reactor, the Tokamak Fusion reactor, fusion, generate, consumeB. Verbs related to nuclear-fusion reaction:ignite, release, stickC. Excitement and cool-down:not a few tears, The experiment is an important milestone, but fusion power is still along way . . . , But no one knows for sure whether…, Even then it will take decades of engineering before…1. nuclear fusion2. repel3. blastVI. Topics for Discussion and Writing(Omitted)W RITING • R HETORIC • METONYMY AND SYNECDOCHEI. Study the uses of metonymy in the following sentences and then put them into Chinese.1.The election benched him in the district court.他在这次竞选中当上了地区法官。
外文原文 (2)
附件2:外文原文(复印件)Performance of RC frames with hybrid reinforcement under reversed cyclic loadingM. Nehdi and A. SaidDept, of Civil & Env. Eng., The University of Western Ontario, London, Ontario, Canada, N6A 5B9Received." 5 May 2004; accepted." 13 October 2004ABSTRACTThe use of FRP as reinforcement in concrete structures has been growing rapidly.A potential application of FRP reinforcement is in reinforced concrete (RC) frames. However, due to FRP's predominantly elastic behaviour, FRP-RC members exhibit low ductility and energy dissipation. Hybrid steel-FRP reinforcement can be a viable solution to the lack of ductility of FRP-RC members. Using two layers of reinforcement in a section, FRP rebars can be placed in the outer layer and steel rebars in the inner layer away from the effects of carbonation and chloride intrusion. Combined with the use of FRP stirrups, this approach can enhance the corrosion resistance of RC members.However, current design standards and detailing criteria for FRP-RC structures do not provide detailed seismic provisions. In particular, the design and detailing of beam-column joints is a key issue in seismic design. During recent earthquakes, many structural collapses were initiated or caused by beam-column joint failures. Thus, research is needed to gain a better understanding of the behaviour of FRP and hybrid FRP-steel-RC under seismic loading. In this study, three full-scale beam-column joint specimens reinforced with steel, GFRP and a hybrid GFRP-steel configuration, respectively were tested in order to investigate their performance in the event of an earthquake.1.INTRODUCTIONCorrosion of reinforcing steel has been the primary cause of deterioration of reinforced (RC) structures, requiring substantial annual repair costs around the world. Furthermore, modem equipments that employ magnetic interferometers, such as in hospitals, require a nonmagnetic environment with no metallic reinforcement. This has led to an increasing interest in fibrereinforced polymers (FRP) reinforcement, which is inherently nonmagnetic and resistant to corrosion [1].Measurement devices for structural health monitoring purposes. However, FRP materials often exhibit weaker bond to concrete and lower ductility compared to that of conventional steel reinforcement. The bond of FRP to concrete can be improved by means of mechanical anchorages such as surface deformations and sand coating, but its lower ductility remains a major concern, especially in structures subjected to seismic and/or impact loading.Brown and Bartholomew [2] observed that FRP-RC beams behaved in a similar manner to that of steel-RC beams.However, in the design process, two criteria that are not usually problematic in thecase of steel reinforcement can govern the design in the case of FRP reinforcement: deflection and ductility. Most FRP materials usually have a significantly lower modulus of elasticity compared to that of steel (except for some new CFRP products) and thus, often generate higher deflections, Furthermore, the predominantly elastic behaviour of FRP results in little warning before a usually sudden and brittle failure. Satisfying deflection and ductility requirements is a challenge in designing FRP-RC structures. Thus, it is recommended that flexural design of FRP-reinforced slabs and beams should aim at over-reinforced sections in order to achieve a concrete compression failure, which usually allows FRP-RC flexural members to exhibit some plastic behaviour before failure [3, 4].In recent years, there has been a growing interest to investigate the performance of mixed steel-FRP as well as steel-free FRP-RC structures. However, research in this area has been generally limited to some beam and column testing.Most of the newly adopted specifications for the design of FRP-reinforced concrete [4-8] are not comprehensive, often do not include detailed seismic provisions, and do not cover hybrid FRP-steel RC systems. Therefore, research is needed to investigate the performance of FlIP and hybrid FRP-steelreinforced concrete frames under reversed cyclic loading in order to form the basis for future design code provisions for FRP-reinforced concrete in seismic zones. In this study, fullscale steel-reinforced, steel-free GFRP-reinforced, and hybrid GFRP-steel-reinforced beam-column joints were tested under reversed cyclic loading; Their behaviour including load-storey drift envelope relationship and energy dissipation were compared and discussed.2. SCOPE OF PREVIOUS WORKThe use of FRP as reinforcement in RC beams was investigated by various researchers. Different permutations of FlIP and steel as longitudinal and transverse reinforcement,respectively were studied [9-11]. Although transverse reinforcement is usually closer to the concrete surface and is therefore more vulnerable to corrosion, limited investigations have been performed on the use of FRP stirrups. The use of FlIP stirrups has been hindered by their limited availability and the fact that a 60% strength reduction factor at bends for various types of FRP is recommended [6]. Also, bending FRP bars to make stirrups typically needs to be performed in production plants with special care and equipment. The use of FRP NEFMAC (New Fiber Composite Material for Reinforcing Concrete) grids can provide a solution to such a problem; a four-ceU unit taken from a NEFMAC grid provides a three-branched stirrup as shown in Fig.Grira and Saatcioglu [12] investigated the use of both steel grids and CFRP grids as stirrups for confinement of concrete columns having longitudinal steel reinforcement. Several grid configurations were used and column specimens were tested under cyclic loading. They concluded that the performance of columns reinforced with CFRP stirrups was comparable to that of columns reinforced with steel stirrups. They also argued that the use of grids whether made of steel or CFRP provides ease of construction and a near-uniform distribution of the confinement pressure along the column, without congesting the reinforcement cage. They reported that the NEFMAC gridbased stirrups failed at their nodes, which is usually thecommon weakness of FRP stirrups. Fukuyama et al. [13] tested a half-scale three-storey AFRP-reinforced concrete frame under quasi-static loading. RA11S aramid-bars were used for the longitudinal reinforcement of columns, RA7S bars were used as flexural reinforcement for beams and slabs, while RA5 bars were used as shear reinforcement. RA11S, RA7S and RA5 are braided bars with cross-sectional areas of 90, 45 and 23 mm 2, respectively. It was argued that frame deformations governed the design. The frame remained elastic up to a drift angle of 1/50 rad, and no substantial decrease in strength took place after rupture of some main beam rebars owing to the high degree of structural indeterminacy of the frame. It was also noted that the rehabilitation of such a frame was easier than that of conventional RC flames since residual deformations were smaller. However, the flame was not tested to collapse and its behaviour under excessive deformations was not reported. Limited research has been performed on hybrid FRP-steel reinforced concrete. Aiello and Ombres [14] tested 6 beams with different configurations of longitudinal reinforcement including steel only, AFRP only, and hybrid AFRP-steel beams, all with steel stirrups. For some of the hybrid specimens, steel was placed with a larger concrete cover to provide extra protection against corrosion. Experimental results showed that such a hybrid system can have lower service deflection and higher ductility at failure than that of the AFRP steel-flee system. Leung and Balendran [15] tested seven RC beams under four point bending. Concrete strength and reinforcement ratios for both steel and GFRP were varied to produce under-reinforced and over-reinforced sections. Steel rebars were placed at 30 mm higher concrete cover compared to that for GFRP rebars. The study showed that for hybrid beams, steel contributed more effectively to the overall behaviour up to yield. Afterwards, the stiffness of yielded steel dropped drastically and the GFRP rebars started to contribute more efficiently to the section resistance. For high strength concrete beams, the increased flexural capacity resulted in shifting the flexural failure into a shear failure.Some research focused on providing ductility to FRP rebars that are manufactured by filament winding or pultrusion. For instance, Tamuzs and Tepfers [16] investigated the properties of a hybrid FRP rod. They used multiple fibre types along with braiding fibre strands around a soft porous core to achieve a more ductile behaviour. The hybrid rods they produced could provide a ductile behaviour, but the difference between the moduli of different fibre strands seemed to cause uneven load transfer, while the compression of the core material caused a reduction of cross-section. A similar study was performed by Bakis et al. [17] who developed pseudo- ductile FRP rods using different types of fibres. The rods behaved in a pseudo-ductile manner when tested under tension, but premature failure took place due to local stress concentrations. Another study performed by Harris et al. [18] developed a ductile hybrid FRP rebar through braiding of various fibres followed by a pultrusion process. Belarbi et al. [19] were also successful in developing composite reinforcing rebars with a relatively more stable stress-strain behaviour in tension and better load-deflection behaviour under four-point bending. However, such rebars are still in early experimental stages and there is not enough data on their field performance, especially under seismic loading.3. EXPERIMENTAL PROGRAMBeam-column joints can be isolated from plane frames at the points of contraflexure. The beam of the current test unit is taken to the mid-span of the bay, while the column is taken from the mid-height of one storey to the mid-height of the next storey.3.1 Steel-reinforced specimen (J1)3.2 GFRP-reinforced specimen (J4)3.3 Hybrid-reinforced specimen (J5)3.4 Test setup and procedure5. DISCUSSIONThe use of FRP as reinforcement in concrete structures has been increasing in popularity, yet various design guidelines and provisions still need to be developed for its safe implementation in large-scale field applications. For instance, the ACI 440.1R-01 identified a wide variety of research issues pertaining to FRP that need to be addressed, some of which are as simple as establishing the statistical variation of the tensile capacity of FRP rebars. Moreover, the contribution of FRP transverse reinforcement to the shear capacity of RC elements needs to be properly evaluated. The lower bond strength of FRP to concrete compared to that of steel imposes difficulties in design, for instance in satisfying rebar development length such as in the case of beam reinforcement anchorage in exterior joints, for which using FRP would require additional embedded length compared to when steel rebars are used. Also the difficulty of manufacturing bends in FRP makes it difficult to adopt this material in reinforcing structurally complicated configurations and needs to be addressed.A major drawback of steel-free FRP-RC systems is their low energy dissipation under earthquake loading, as demonstrated by the performance of the tested FRP-reinforced joint specimen (J4). The energy input from ground motion is equal to the sum of potential, kinematic, damping and hysteretic energy components [22]. The potential and kinematic energy components vanish after the static equilibrium of the structure is reached, while the damping and hysteretic energy components are responsible for energy dissipation. The hysteretic component becomes the major contributor to energy dissipation when significant inelastic deformations take place. Hence, an FRP-reinforced frame may have to be designed with a high damping component so that when added to its relatively limited hysteretic Component, it can dissipate the energy input during an earthquake. Design guidelines for framed RC buildings by the Architecture Institute of Japan, as outlined by Kobayashi et al. [23], entail ensuring seismic performance by overcoming the ductility deficiency of FRP-RC frames. The study recommended the use of the capacity spectrum method. Performance demand and capacity spectra were evaluated and a performance point, where the demand and capacity spectra meet and members are still below their flexural capacity, was defined as the safety limit. This performance-based design approach was successfully applied to the analysis of a 9-floor FRP-RC frame. The study also pointed out the cruciality of damping in FRP-RC structures and recommended the use of vibration control devices.The use of hybrid steel-FRP RC systems could address many of the drawbacks ofsteel-free RC systems. Steel reinforcement can be used in lateral load resisting structural members, which are not usually exposed to aggressive media, while FRP reinforcement can be used in the envelope of the structure to enhance durability. Alternatively, a hybrid reinforcement configuration can make use of the corrodible steel at a thick concrete cover, while the more durable FRP stays at a minimum cover. Thus, the structure can benefit from using such a hybrid reinforcement system to provide both durability (using FRP) and post-peak reserve strength (using steel).The present study focussed only on comparing the behaviour of FRP, hybrid steel-FRP, and steel-reinforced beam-column joints. Full-scale tests on entire FRP and hybrid-reinforced frames need to be performed to assess the progress of failure globally. The results can be used to calibrate numerical models that can be used to simulate the behaviour of multi-storey FRP and hybrid-reinforced frames with high degrees of redundancy, and accordingly predict the progress of failure. Moreover, passive energy dissipation devices can provide a source of energy dissipation for FRP-reinforced frames, which needs further focussed research. Overall, research efforts are still needed to address many questions and uncertainties, and to develop adequate design provisions dedicated to steel-free and hybrid RC systems, before their widespread use in demanding large-scale structural applications becomes feasible and safe in seismic areas.6. CONCLUSIONSAn effort was made to investigate the performance of GFRP and hybrid steel-GFRP-reinforced beam-column joints and to compare their behaviour to that of standard steel-reinforced beam-column joints under reversed quasi- static (cyclic) loading.,the following conclusions can be drawn:The GFRP-reinforced beam-column joint showed very low plasticity features when tested under reversed cyclic loading. This resulted in lower energy dissipation compared to that of the steel and hybrid reinforced specimens.The hybrid GFRP-steel-reinforced beam-colunm joint showed lower stiffness than that of the conventional steel- reinforced beam-column joint, but exhibited higher stiffness than that of the GFRP-reinforced specimen.The GFRP and hybrid-reinforced specimens showed satisfactory drift capacity, assuming a minimum drift requirement of 3% (0.03 rad) as recommended in the literature for ductile RC flame buildings [24].A hybrid RC system could be tailored to provide a range of performance requirements such as durability, stiffness, strength, ductility, etc. A designer may adapt the reinforcement configuration of the hybrid system to accommodate a balance between such design criteria.This study was only focussed on the level of the subassemblage. A more global concept should be adopted in the design of moment-resisting frames. Thorough dynamic analysis of GFRP and hybrid-RC structures should be performed to better assess their capacity in meeting seismic resistance requirements.Design code provisions for the seismic design of RC structures, which have been developed for ductile steel reinforcement, need to be re-evaluated for FRP-RC structures.。
纤维增强复合材料激光烧蚀效应的数值模拟
纤维增强复合材料激光烧蚀效应的数值模拟彭国良;闫辉;刘峰;杜太焦;王玉恒【摘要】考虑材料的热解、氧化、相变及辐射和内外对流换热等物理过程,给出了激光烧蚀纤维增强复合材料的物理模型及数学模型.以碳纤维/环氧树脂复合材料为例,编程计算了材料的激光烧蚀过程,计算结果与实验结果符合得较好.计算结果表明:考虑复合材料的内对流时得到的结果更准确;较强功率密度激光辐照时,氧化对烧蚀的贡献可以忽略:功率密度一定时,烧蚀质量随时间近似为线性变化,功率密度越高,烧蚀效率越高.以辐照结束时背表面温度及烧蚀质量为目标物理量,对烧蚀过程做了参数敏感性分析,结果表明:热容及热导率对背表面温度的影响较大;树脂含量对烧蚀质量的影响较大,但其相对敏感度随激光功率密度增加而下降;激光功率密度超过1 kW/cm2时,辐射系数对烧蚀质量影响较大,但其相对敏感度随激光功率密度增加而下降.【期刊名称】《中国光学》【年(卷),期】2013(006)002【总页数】7页(P216-222)【关键词】纤维增强复合材料;激光烧蚀;氧化;内对流;数值模拟【作者】彭国良;闫辉;刘峰;杜太焦;王玉恒【作者单位】西北核技术研究所,陕西西安710024;西北核技术研究所,陕西西安710024;西北核技术研究所,陕西西安710024;激光与物质相互作用国家重点实验室,陕西西安710024;西北核技术研究所,陕西西安710024;激光与物质相互作用国家重点实验室,陕西西安710024;西北核技术研究所,陕西西安710024;激光与物质相互作用国家重点实验室,陕西西安710024【正文语种】中文【中图分类】TG156.99纤维增强复合材料(如K/E、C/E等)具有高比强度、高比模量等特点,在航天航空领域得到了广泛的应用,目前正逐步取代黑色金属、有色金属等传统材料,成为轻质化结构的主要材料,如飞行器的壳体结构(发动机、过渡段、控制舱等)逐步由纤维缠绕复合材料取代钢质材料已成为主流方向。
medical condition
ORIGINAL CONTRIBUTIONMedical conditions affect the outcome of early intervention in preschool children with autism spectrum disordersMats Anders Eriksson •Joakim Westerlund •A˚sa Hedvall •Per A ˚mark •Christopher Gillberg •Elisabeth FernellReceived:1April 2012/Accepted:14July 2012/Published online:27July 2012ÓSpringer-Verlag 2012Abstract The aim was to explore the frequency of genetic and other medical conditions,including epilepsy,in a population-based group of 208preschool children with early diagnosis of Autism spectrum disorders (ASD)and to relate outcome at a 2-year follow-up to the co-existing medical findings.They had all received early intervention.The Vineland Adaptive Behaviour Scales (VABS-II)composite score served as the primary outcome measure.In the total group,38/208children (18%)had a significant medical or genetic condition.Epilepsy was present in 6.3%at the first assessment and in 8.6%at follow-up and was associated with more severe intellectual impairment.A history of regression was reported in 22%.Children with any medical/genetic condition,including epilepsy,as well as children with a history of regression had significantly lower VABS-II scores at the 2-year follow-up.Children with a medical/genetic condition,including epilepsy,had been diagnosed with ASD at an earlier age than those without such conditions,and early age at diagnosis alsocorrelated negatively with adaptive functioning outcome.The results underscore the importance of considering medical/genetic aspects in all young children with ASD and the requirement to individualize and tailor interven-tions according to their specific needs.Keywords Autism spectrum disorder (ASD)ÁMedical/genetic disorders ÁEpilepsy ÁEarly intervention ÁOutcomeIntroductionThe aim of the present study was to explore the frequency of genetic and other medical conditions,including epi-lepsy,in a representative group of preschool children with early diagnosis of Autism Spectrum Disorders (ASD)and to relate outcome to co-existing medical findings.According to several studies,early intervention has been reported to improve outcome in children with ASD [14,22].However,these studies have demonstrated considerable variability in outcome with low initial IQ repeatedly dem-onstrated to contribute to a less favourable outcome [23].It is important to remember that in many of these studies children with co-existing genetic and medical disorders,such as epilepsy,have been excluded [12,14,23,48].Autism spectrum disorders are highly heritable neuro-developmental disorders affecting about 1%of the child-hood population [6,18].The etiological heterogeneity in ASD is extensive.In about 10–20%of all ASD cases,a genetic cause is identified [1,10].More than 100disease genes have been reported in individuals with ASD [9].In children with ASD conventional karyotyping identi-fies abnormalities in about 2%[42]and Fragile X syn-drome is identified in about 2%[38].With the use of whole genome array-based comparative genomic hybridizationM.A.Eriksson ÁP.A˚mark Department of Women’s and Children’s Health,Karolinska Institutet,Stockholm,SwedenM.A.Eriksson (&)Department of Neuropaediatrics,Astrid Lindgren’s Children’s Hospital,Karolinska University Hospital,17176Stockholm,Sweden e-mail:mats.a.eriksson@ki.seJ.WesterlundDepartment of Psychology,Stockholm University,Stockholm,SwedenA˚.Hedvall ÁC.Gillberg ÁE.Fernell Gillberg Neuropsychiatry Centre,Sahlgrenska Academy,Gothenburg University,Gothenburg,SwedenEur Child Adolesc Psychiatry (2013)22:23–33DOI 10.1007/s00787-012-0312-7(array-CGH),sub-microscopic deletions and duplications (copy number variations;CNVs)have been increasingly identified in ASD as well as in intellectual disability(ID) [32]and epilepsy[30].In children with ASD,about7% have been reported to have causative CNVs[41,45].Autistic features or ASD and/or epilepsy occur in sev-eral well-recognized single-gene disorders such as Tuber-ous sclerosis,Rett syndrome,Fragile X,Smith-Lemli-Opitz and Angelman syndrome[10].Although genetic susceptibility is of major importance,environmental and epigenetic factors may influence the risk of ASD.The (relatively small)discordance in monozygotic twins sug-gests the presence of non-heritable,pre-and perinatal risk factors for autism[26,39].Several prenatal and perinatal risk factors have been associated with ASD.Intrauterine congenital central ner-vous system viral infections and exposure to various agents such as sodium valproate may increase the risk for cogni-tive impairment,including ASD[15,33,37].Epidemio-logical studies have not yet found any association between alcohol consumption and increased risk for ASD[21],but in two Swedish studies,9–13%of children whose mothers abused alcohol in pregnancy had ASD[4,27].Regarding perinatal factors,several studies have shown increased risk for cognitive problems,including ASD in extremely pre-term and low birth weight children[13,24,29].The prevalence of epilepsy in childhood in general is 0.5–0.7%.Epilepsy,much like ASD,can be viewed as a spectrum disorder with multiple aetiologies and highly variable clinical presentation[25].Cognitive deficits are prevalent in children with epilepsy with approximately 25%having mental retardation[7].The prevalence esti-mates of epilepsy in children with ASD vary from5to 46%[43,46].The rates of epilepsy in ASD increase with age and the association between ASD and epilepsy is closely linked to the presence and degree of cognitive impairment.In a meta-analysis by Amiet et al.[3],a pooled frequency of epilepsy was21.4%in patients with autism. The rate of epilepsy in subjects without cognitive impair-ment was8%,clearly a higher prevalence than in the normal population.In children with intellectual disability and active epilepsy co-existing ASD is found in37%[44]. It is well established that early onset epilepsy increases the risk of ASD.Saemundsen[40]found that14%of children with epilepsy onset in thefirst year of life developed aut-ism.In children with infantile spasms,the risk for ASD was46%and in children with more severe structural brain disorder(hypoxic ischemic encephalopathy,cortical dys-plasia,tuberous sclerosis)69%were found to have ASD. The author’s conclusion was that the risk of developing autism is probably mostly predicted by the origin of the seizures and,usually,not a consequence of an epileptic encephalopathy.Developmental regression with loss of acquired skills is reported in children with ASD at rates ranging from15to 40%depending on the definition of regression and sample of children[28,31].The most consistent documented finding in such cases is loss of verbal skills,but this is often accompanied or preceded by loss of social skills.The onset of regression is often reported to be between the ages of15 and24months.Previous studies have not found epilepsy, seizures or subclinical EEG abnormalities to be more prevalent in children with‘‘autistic regression’’compared to non-regressive autism[5,19].Children with autistic regression tend to have poorer cognitive outcome com-pared to children without regression[8].In a subset of children with regressive autism,early development may be delayed and some children have social deficits before the regression is identified[35].To our knowledge,no previ-ous study has explored the influence of co-occurring medical conditions or a history of developmental regres-sion in relation to early intervention.MethodParticipantsThe study included208children,20–54-month-old,when referred to a specialized habilitation centre with a diagnosis of ASD.They were drawn from a population-based group of313children(born2002–2006)with ASD diagnoses in Stockholm County,a region with approximately28,000 births per year.Of these313children,288had been referred for early intervention to a specialized habilitation centre for preschool children with ASD.Twenty-five children with more severe medical conditions and syn-dromes in combination with ASD were referred to general habilitation centres due to more complex needs.At these centres,no specific ASD interventions were provided.This group was not included in the outcome study.Of the288children,24had been referred to the centre prior to study start and could not be included.Of the remaining264children,37families declined participation, 15families could not communicate in either Swedish or English,two children moved abroad and another two were referred back to general habilitation centres because they had complex medical needs.This means that208children(176 boys and32girls)were included in this prospective two-year follow-up study(Fig.1).No exclusion of children with ASD and identified medical conditions/or significant ID was done once type of intervention had been initiated.However,it is clear that the study group did not include some of the most medically‘‘complex’’cases with ASD in the population.Of the total group,64(31%)had been referred before the age of36months,83(40%)between37-48months and61(29%)between the ages of49–54months.Of the208children,198participated in the two-year plete cognitive data was obtained in196, and data regarding type of ASD diagnosis was obtained in197[17].Autistic disorder/childhood autism was diagnosed in105(53%),atypical autism in58(29%), Asperger syndrome in13(7%),and autistic traits in21 (10%)at follow-up after2years.Four of those with autistic traits(2%of the total group)had ID with autistic traits and17(8%)had attention/language impairment with autistic traits.Of the196children,95(48%)had ID (IQ\70),50(26%)had low normal/borderline intel-lectual function(IQ70–84),and51(26%)average or above average intellectual level(IQ C85).In12children with incomplete cognitive assessment at the follow-up, the cognitive level was classified according the level defined at referral(5children with ID,5with develop-mental delay/borderline IQ and2with average intellec-tual level).MeasuresAt referral to the habilitation centre,Time1(T1),data were collected from each child’s maternity and obstetric care units,the Child Health Care centre(CHC)and all hospital and outpatient clinics attended by the child.Both at T1and at the two-year follow-up,Time2(T2)the paediatrician/ child psychiatrist in the research team examined all chil-dren.Details regarding interview protocols,including cognitive assessments and questionnaires at T1and T2have been reported in previous publications[16,17].In addition to data from records,parents were inter-viewed regarding the child’s pre-and perinatal history, early development,and any genetic,neurologic or other clinically significant medical condition,including epilepsy.Regression was defined as loss of more thanfive spoken words used communicatively in children morethan15months of age.In children younger than15months, regression was determined when there was a clear indica-tion of loss of social interest and contact.Parents were interviewed(in close temporal connection to thefirst diagnostic assessment)regarding a history of regression in the child and this information was compared to available data in CHC and medical records.Consistency was required between parental information and the notes in the record’s from CHC.Participating families were recommended genetic test-ing using array-based Comparative Genomic Hybridization (array-CGH)(thesefindings will be described in detail in a forthcoming paper)and testing for Fragile X.Conventional chromosomal karyotyping had been performed in many children.In girls with a clinical suspicion of Rett syndrome mutation for MECP2were analysed.Medical and genetic conditions were defined as:(1)a significant intrauterine harmful exposure,(2)substantial prematurity(gestational age less than29weeks),(3)an identified genetic disorder including significant genomic imbalances identified with array CGH,(4)abnormal brain MRIfindings and(5)a clinical diagnosis of epilepsy.At T2,the parents of198children were interviewed a second time to collect information about any new medical condition that had affected the child during the observation time and208hospital and outpatient medical records were once again reviewed.At that time,a new cognitive assessment was carried out to establish the child’s Devel-opmental Quotient/Intelligence Quotient(DQ). InterventionAll208children received intervention based on princi-ples of Applied Behaviour Analysis(ABA).The study design was naturalistic.There was no randomization to treatment type.Parental preference was the most decisive factor.The presence of medical/genetic condition did not affect choice of intervention type.In many children,a medical condition had not yet been identified.One group (n=93)received‘‘intensive’’and the remainder (n=105)‘‘non-intensive’’targeted intervention.The different levels of interventions were defined as:Inten-sive intervention based on ABA,i.e.,early intensive behavioral intervention(EIBI),given at the preschool and by the parents at home with assistance from the center,with the intention to treat(a)15h or(b)25–30h per week or30–40h per week.Non-intensive targeted intervention based on ABA,consisting of different tar-geted types of training(toilet training,speech and lan-guage training,training of compliance or other specific training that the child was deemed to need).Details of these interventions have been reported in a previous paper[17].Outcome measureThe primary outcome measure was change in Vineland Adaptive Behaviour Scale(VABS-II)composite scores between T1and T2.VABS II is a valid and often used outcome measure of adaptive skills in children with ASD [14,20].A total of192children had complete VABS-II scores both at T1and T2.Numbers of children in the outcome analyses reflect the number of individuals that could be assessed according to the studied variable and to the Vineland change score.Outcome was measured by raters who were blind to the type of intervention given. Statistical analysesData analysis were conducted with the IBM Statistical Package for the Social Sciences(SPSS)Version19.In order to examine the influence of potential dichotomous risk fac-tors(e.g.gender)on various dichotomous conditions(e.g.a medical/genetic condition),odds ratios(OR)and their95% confidence intervals(95%CI)were calculated by logistic regression analysis.Mean age at referral for intervention for children with versus for children without medical/genetic conditions was compared with a t test.Vineland Adaptive Behaviour Scales change scores were related to(1)any medical/genetic condition including epilepsy,(2)epilepsy‘‘only’’,(3)regression and(4)age at referral,and for each of these four factors also to the level of intensity of intervention.For each factor,a2(T1/ T2)92(level of intensity of intervention)92(value on current factor,e.g.regression Yes/No)mixed Analysis of Variances(ANOVA)was computed,using eta-squared(g2) as a measure of effect size.An alpha level of0.05was used for all statistical analyses.EthicsThe Regional Ethics Committee in Stockholm approved the study.ResultsMedical/genetic conditions,including epilepsy,in preschool children with ASDAt T1,a medical/genetic condition with probable association with the child’s ASD was identified in22children(11%),and at T2another16children had been found to have an associated medical/genetic condition(38/208)(18%).At T1,7of the208children had a medical disorder/ genetic syndrome identified.Of these,three boys had tuberous sclerosis(all with epilepsy),one boy had Fragile X syndrome(141/142FMR1-examined children tested negative for Fragile X),one boy had pyridoxine dependency(with a verified mutation in the ALDH7A1-gene),one boy had duplication17p13.3,and one girl had deletion22q11syndrome.Another nine children had medical conditions with less clear(but probable)asso-ciation with the child’s ASD.Of these nine,three had abnormal magnetic resonance imagingfindings indicating cortical dysplasia/migrational disorder,two had been born preterm(gestational week24and28),one adopted child met criteria for foetal alcohol spectrum disorder, one child had a history of prenatal intrauterine exposure to sodium valproate(mother treated for epilepsy),one boy had congenital hydrocephalus with ventriculoperito-neal shunt,and one boy was clinically diagnosed with Pierre Robin syndrome.Epilepsy without aetiology was found in another six children(all male)at T1.At T2,medical/genetic conditions could be analysed in the total group of208children.Five children developed epilepsy between T1and T2.Two of the three girls clini-cally suspected of having Rett syndrome were‘‘confirmed’’by genetic testing for MECP2mutation.In another nine children,analysed with array-CGH,a significant genomic imbalance was found.Details on thesefindings and asso-ciated developmental profiles in children with abnormal CGH-array results will be presented in a separate article. The preliminary diagnostic yield was7.4%(12/162).ID was found in63%(24/38)of those with medical/ genetic/epilepsy disorders as compared with45%(76/170) in those without such disorders(OR=2.12,95% CI=1.03–4.38,p=0.042).Medical/genetic conditions including epilepsy were more often,but not significantly,found in children with the combination of ASD and ID(24/102)(24%)as compared with those who had ASD without ID(14/106)(13%) (OR=2.095%CI=0.98–4.17,p=0.057).Of the32girls,10(31%)had an identified medical/ genetic condition.The corresponding rate in boys was 28/176=16%(OR=2.40,95%CI=1.03–5.62, p=0.043).Any medical/genetic condition including epilepsyand age at referralChildren with medical/genetic conditions,including epi-lepsy,had been referred for intervention at significantly earlier ages compared to those without such conditions (M=38.3,SD=10.1vs.M=41.4,SD=8.3; t206=1.97,p=.05).EpilepsyAt T1,13/208(6%)children had been diagnosed with epilepsy and at T2(ages between 4.5and 6.5years) 18/208(9%)had epilepsy.Excluding those children whose epilepsy was part of a known medical/genetic syndrome,the epilepsy prevalence was5%(‘‘idiopathic epilepsy’’).Epilepsy onset varied from thefirst days of life up to the age of6years.Four children(4boys)had infantile spasms(West syndrome),of whom two had tuberous sclerosis,one had a CNS-malformation,and one was ‘‘idiopathic’’.A definite aetiology was identified in7/18 cases with epilepsy;three children had tuberous sclerosis, two had CNS malformations,one boy had B6depen-dency,and one girl had Rett syndrome.Of the11chil-dren without an identified medical disorder/genetic syndrome and with normal magnetic resonance imaging, 6could be classified as having epilepsy with generalized seizures,2had focal seizures and3had unclassifiable seizures.Epilepsy was diagnosed in4/32girls(13%)and in14/176boys(8%),(OR=1.65,95%CI= 0.51–5.39,n.s.).In children with the combination of ASD and ID(IQ\70)13/102(13%)had epilepsy whereas children with ASD and borderline,average or above average IQ(IQ[70),5/106(5%)had epilepsy (OR=2.95,95%CI=1.01–8.60;p=0.047).Clinical characteristics of children with epilepsy are presented in Table1.Regression and clinical characteristicsA history of regression was described both in the child’s CHC records and at parental interview in46/208children (22%).The most consistentfinding was loss of expres-sive language skills.A few children were also reported to have deterioration in social interaction skills and some behavioural changes such as hyperactivity or extreme passivity.Regression was reported in5/32girls(16%) and41/176boys(23%),(OR=0.61,95% CI=0.22–1.68,n.s.).A history of regression was more common in children with a clinical diagnosis of autistic disorder(33/105,31%)as compared with children with atypical autism/PDD-NOS(7/ 58,12%,OR=3.34,95%CI=1.37–8.14,p=0.008).In children with the combination of ASD and ID, regression was reported in34%(35/102)versus10%(11/ 106)in children with ASD without ID(OR=4.5195% CI=2.14–9.51,p\0.001).Regression and relation to epilepsy(including febrile seizures)Epilepsy was no more common in children with regression (3/46)than in those without(15/162)(OR=0.68,95% CI=.19–2.47,n.s.).Febrile seizures had occurred in16/208children(8%). Four of these children had epilepsy at follow-up.Febrile seizures were not significantly more common in children with ASD without a history of regression(15/162)com-pared to children with regression(1/46)(OR=4.59,95% CI=0.59–35.73,p=0.145).Outcome in relation to medical/genetic conditions, excluding epilepsy,and to intensity of interventionAs shown in Fig.2,children without any medical/genetic condition had a positive VABS-II change score at T2 (compared to T1)whereas children with a medical/genetic condition(excluding epilepsy)had a negative change score.A29292mixed ANOVA with Medical/genetic condition(yes,no)and Intervention intensity(intensive or non-intensive ABA)as between-subjects factors,Time(T1, T2)as a within-subjects factor and Vineland composite score as the dependent variable showed however that theTable1Some medical characteristics in children with ASD and epilepsySex Onset Initial seizuresemiology EEG Imaging Aetiology AED at Time2Seizurefree,at T2Male1day Tonic,apnoea,eye deviationMultifocal bilateral N(MRI)B-6dependency B-6?folic acid? Male4days Focal clonic Focal right hemisphere N(MRI)Unknown None? Female3weeks Head/eye deviation Focal right central?(MRI)CNSmalformationRUF,ZNSMale2months Focal?infantilespasms?F.S.Focal leftfrontal[hypsarrythmia?(MRI)TuberoussclerosisVPAMale6months Infantile spasms Multifocal/hypsarrythmia?(MRI)TuberoussclerosisVPA?Male7months Infantilespasms?F.S.Multifocal N(CT)Unknown VPA,CLB,PB,LCMMale11months GTCS Focal left hemisphere?(MRI)TuberoussclerosisOXC,LEV?Male14months Breath holdingspells/GTCSNormal N(MRI)Unknown LEV?Male18months Absence?tonic Generalizedsharp-slow waveN(MRI)Unknown VPA,LEV,CLBMale18months Myoclonic?GTCS?F.S Focal bilateral frontal spike/polyspikeN(MRI)Unknown LEV,LTG,CLBMale19months Infantile spasms Multifocal/hypsarrythmia?(MRI)CNSmalformation RUF,ESM,ketogenic dietMale3years Absence Focal right centrotemporal N(CT)Unknown None? Male4years GTCS Generalized3Hz spikeand waveN(CT)Unknown LTG?Male4years Absence Generalized sharp wave NotdoneUnknown VPA?Female5years Complex focal Bilateral central polyspike during sleepN(MRI)Rett syndrome VPA,LTG?Female5years Absence Generalized2.5–3Hz spikeand waveN(MRI)Unknown VPAFemale6years Complexfocal?F.S.Generalized spikeand slow waveN(MRI)Deletion(2)p16.3VPA,LEV,NZPMale6years None Bilateral frontalduring sleep,CSWSN(CT)Unknown LTG?Initial seizure semiology refers to presenting seizure type/epilepsy syndromeEEG refers to result of most pronounced pathology at the time of epilepsy diagnosisF.S.History of febrile seizures,AED Antiepileptic drugs at intervention time2,RUF Rufinamide,ZNS zonisamide,VPA valproate,CLB clobazam,PB Phenobarbital,LCM lacosamide,OXC oxcarbazepine,LEV levetiracetam,ESM etosuximide,LTG lamotrigine,NTZ nitrazepamMedical/Genetic condition 9Time interaction effect was not significant (F 1,173=1.19,p =0.276,g 2=0.007).Outcome in relation to epilepsy and to intensity of interventionA 29292mixed ANOVA with Epilepsy (yes,no)and Intervention intensity (intensive or non-intensive ABA)as between-subjects factors,Time (T1,T2)as a within-sub-jects factor and Vineland composite score as the dependent variable revealed a significant Epilepsy 9Time interaction effect (F 1,188=7.09,p =.008,g 2=.036).As shown in Fig.3,children without epilepsy had a positive VABS-II change score at T2(compared to T1)whereas children with epilepsy had a negative change score (p \.01).Outcome in relation to regression and to intensity of interventionA 29292mixed ANOVA with Regression (yes,no)and Intervention intensity (intensive or non-intensive ABA)as between-subjects factors,Time (T1,T2)as a within-subjects factor and Vineland composite score as the dependent variable revealed a significant Regres-sion 9Time interaction effect (F 1,188=4.58,p =0.034,g 2=0.024).As shown in Fig.4,children without regres-sion had a positive VABS-II change score at T2(compared to T1)whereas children with regression had a negative change score.We also obtained a main effect of regression.Children without regression had a significantly higher mean Vineland composite score (irrespective of time)than children with regression (F 1,188=11.90,p \0.001,g 2=0.060).Outcome in relation to age at referral and to intensity of interventionA 29292mixed ANOVA with referral age (before or after the age of 3years)and Intervention type (intensive or non-intensive ABA)as between-subjects factors,Time (T1,T2)as a within-subjects factor and Vineland composite score as the dependent variable revealed a significant referral age 9time interaction effect (F 1,188=8.32,p =0.004,g 2=0.042).As shown in Fig.5,children who had been referred after the age of 3years had increased their VABS-II composite score at T2(compared to T1)whereas children who had been referred before the age of 3years had decreased their score [48].Fig.2Mean VABS Composite Score at Time 1and Time 2in children with (n =34)and without (n =158)any medical/genetic condition includingepilepsyFig.3Mean VABS Composite Score at Time 1and Time 2in children with (n =15)and without (n =177)epilepsyFig.4Mean VABS Composite Score at Time 1and Time 2in children with (n =40)and without (n =150)regressionDiscussionThe major findings of the present study were that (1)a medical/genetic disorder,including epilepsy,had been identified in 18%of these preschool children—and in 24%of those with ASD plus ID at follow-up—and the rate of such disorders increased over the two-year study period,(2)about one in five of the children with ASD had a clear history of regression,(3)about one-third of the sample was referred for intervention before 3years of age,and that (4)all of these ‘‘background factors’’contributed to more negative VABS-II outcomes,irrespective of intervention intensity.The study presents data from a relatively large popula-tion-based group of children with ASDs with a variety of ASD aetiologies represented.During the 2-year follow-up period all had received intervention,either intensive or targeted,non-intensive,based on ABA.Parents and pre-school staff of all children had received information about the basic principles of ABA,to use in everyday situations together with the child [17].In a recent systematic review of early intensive inter-vention,the authors concluded that some children with ASDs who enter early intensive behavioural and develop-mental interventions show improvements in cognitive performance,language skills and adaptive behaviour skills when compared with eclectic treatments [48].However,‘‘across the available literature many children who receive early intervention will not demonstrate dramatic gains in social,cognitive,adaptive and educational functioning’’[48].In the study by Dawson et al.[12]significant gains were demonstrated as to cognitive and adaptive behaviour.However,in this ‘‘Early Start Denver Model’’children with identified medical disorders and those with IQs below 35were excluded.Our study group varied with respect to ASD severity and intellectual level and no exclusion from intervention had been made because of any specific medical disorder,even though a subgroup with medical disorders/genetic syn-dromes involved in ‘‘regular habilitation programmes’’had not been included in the study.Moreover,there had been no randomization to treatment groups.The study design was,in effect,naturalistic.A heterogeneous spectrum of aetiologies and co-existing disorders related to autism was found,representing several distinct categories;central nervous system malformations,genetic syndromes,single gene disorders,significant genomic imbalances and prenatal acquired disorders.Thus,an important subgroup of children with an early ASD diagnosis has identifiable medical/genetic disorders,including epilepsy,and these children more often have low cognitive functioning.The rate of epilepsy increased from 6.3%in children aged younger than 4.5years to 8.6%at the 2-year follow-up,and is expected to increase further over time [11].Epilepsy was more often found in children with ASD and associated ID.The epilepsy prevalence in children with ‘‘idiopathic autism’’at age below 6.5years was 5.3%,clearly very much higher than in the general population (Stockholm County age 1–6years;0.6%.(m.Per Amark 2012,[2].In children with epilepsy,the out-come results may to some extent be affected by incomplete seizure control,even though this was not an obvious finding in the present study.Also,at least hypothetically,antiepileptic treatment may carry a risk for negative cog-nitive side effects,but this was not examined specifically in the present study.There was also a very high rate of febrile seizures in the ASD group.It is possible that the seizures in this subgroup should be seen as an indication of a more general brain problem rather than as a factor contributing to the pathogenesis in itself [34].Children with ASD and regression significantly more often had a more severe ASD type and more often ID compared to those without regression.We found no sup-port for an association between regression and epilepsy in our sample.Such an association has often been suggested.However,the relationship between autistic regression and epilepsy remains controversial [36,47].There was an association between age at referral and co-existing medical disorders.Children with a medical diag-nosis had been referred at a significantly earlier age com-pared with those without an identified medical disorder.Thus,there is reason to believe that children identified with ASD at a low age will have an increased risk of having co-occurring intellectual disability,genetic andmedicalFig.5Mean VABS Composite Score at Time 1and Time 2in children who had been referred before (n =65)or after (n =127)age 3years。
材料导论中英文讲稿 (29)
Video 7. CreepNow, Let’s study creep. If you learn creep, you will know there are some similarities between creep and fatigue in their measuring methods. When we measure fatigue property, we apply cyclic loadings. But when we measure creep, we apply a loading to a sample permanently or for a long time. The similarities are that the materials all encounter deformations.译文:我们学习儒变。
学习儒变,你将知道儒变和疲劳的测试方法比较类似。
当测量疲劳性能时,我们加以周期性力。
当测量儒变性能时,我们施加恒定的外力,并保持足够长的时间。
相同的是:材料都发生了形变。
Let us study creep(蠕变). The creep property of material tells (you) deformation (of a material) happens when a material is underwent a constant loading for considerably long time. First I give you definition of creep. It is a slow process of plastic deformation that takes place when a material is subjected to a constant condition of loading (stress) below its normal yield strength. So based on this definition, you will know that. Firstly, creep happens at a very long period of time. Secondly, the loading is constantly applied to the material. Finally, the loading should be lower than the yield strength because otherwise, the material will deform in a very short time.译文:让我们学习儒变。
tpo54三篇阅读原文译文题目答案译文背景知识
托福阅读tpo54全套解析阅读-1 (2)原文 (2)译文 (4)题目 (5)答案 (9)背景知识 (10)阅读-2 (10)原文 (10)译文 (12)题目 (13)答案 (18)背景知识 (20)阅读-3 (25)原文 (26)译文 (27)题目 (28)答案 (33)背景知识 (35)阅读-1原文The Commercialization of Lumber①In nineteenth-century America, practically everything that was built involved wood.Pine was especially attractive for building purposes.It is durable and strong, yet soft enough to be easily worked with even the simplest of hand tools.It also floats nicely on water, which allowed it to be transported to distant markets across the nation.The central and northern reaches of the Great Lakes states—Michigan, Wisconsin, and Minnesota—all contained extensive pine forests as well as many large rivers for floating logs into the Great Lakes, from where they were transported nationwide.②By 1860, the settlement of the American West along with timber shortages in the East converged with ever-widening impact on the pine forests of the Great Lakes states. Over the next 30 years, lumbering became a full-fledged enterprise in Michigan, Wisconsin, and Minnesota. Newly formed lumbering corporations bought up huge tracts of pineland and set about systematically cutting the trees. Both the colonists and the later industrialists saw timber as a commodity, but the latter group adopted a far more thorough and calculating approach to removing trees. In this sense, what happened between 1860 and 1890 represented a significant break with the past. No longer were farmers in search of extra income the main source for shingles, firewood, and other wood products. By the 1870s, farmers and city dwellers alike purchased forest products from large manufacturingcompanies located in the Great Lakes states rather than chopping wood themselves or buying it locally.③The commercialization of lumbering was in part the product of technological change. The early, thick saw blades tended to waste a large quantity of wood, with perhaps as much as a third of the log left behind on the floor as sawdust or scrap. In the 1870s, however, the British-invented band saw, with its thinner blade, became standard issue in the Great Lakes states' lumber factories.Meanwhile, the rise of steam-powered mills streamlined production by allowing for the more efficient, centralized, and continuous cutting of lumber. Steam helped to automate a variety of tasks, from cutting to the carrying away of waste. Mills also employed steam to heat log ponds, preventing them from freezing and making possible year-round lumber production.④For industrial lumbering to succeed, a way had to be found to neutralize the effects of the seasons on production. Traditionally, cutting took place in the winter, when snow and ice made it easier to drag logs on sleds or sleighs to the banks of streams. Once the streams and lakes thawed, workers rafted the logs to mills, where they were cut into lumber in the summer. If nature did not cooperate—if the winter proved dry and warm, if the spring thaw was delayed—production would suffer. To counter the effects of climate on lumber production, loggers experimented with a variety of techniques for transporting trees out of the woods. In the 1870s, loggers in the Great Lakes states began sprinkling water on sleigh roads, giving them an artificial ice coating to facilitate travel. The ice reduced the friction and allowed workers to move larger and heavier loads.⑤But all the sprinkling in the world would not save a logger from the threat of a warm winter. Without snow the sleigh roads turned to mud. In the 1870s, a set of snowless winters left lumber companies to ponder ways of liberating themselves from the seasons. Railroads were one possibility.At first, the remoteness of the pine forests discouraged common carriers from laying track.But increasing lumber prices in the late 1870s combined with periodic warm, dry winters compelled loggers to turn to iron rails. By 1887, 89 logging railroads crisscrossed Michigan, transforming logging from a winter activity into a year-round one.⑥Once the logs arrived at a river, the trip downstream to a mill could be a long and tortuous one.Logjams (buildups of logs that prevent logs from moving downstream) were common—at times stretching for 10 miles—and became even more frequent as pressure on the northern Midwest pinelands increased in the 1860s. To help keep the logs moving efficiently, barriers called booms (essentially a chain of floating logs) were constructed to control the direction of the timber. By the 1870s, lumber companies existed in all the major logging areas of the northern Midwest.译文木材的商业化①在19世纪的美国,几乎所有建筑材料都含有木材。
混凝土梁–柱联接部位的加固(英文翻译)
本科毕业设计(论文)英文专题专业名称:土木矿建年级班级:土木单招06-1班学生姓名:XXX指导教师:余永强河南理工大学土木工程学院二○一○年六月十日Reinforcement of concrete beam–column connectionswith hybrid FRP sheetAbstractThe paper describes the results of tests on prototype size reinforced concrete frame specimens which were designed to represent the column–beam connections in plane frames. The tests were devised to investigate the influence of fibre reinforced plastic (FRP reinforcement applied to external surfaces adjacent to the beam–column connection on the behaviour of the test specimens under static loading. Of particular interest under static loading was the influence of FRP reinforcement on the strength and stiffness of beam–column connection. As a key to the study, the hybrid FRP composites of E-glass woven roving (WR) and plain carbon cloth, combined with chopped strand mat (CSM), glass fiber tape (GFT) with a vinyl-ester resin were designed to externally reinforce the joint of the concrete frame. The results show that retrofitting critical sections of concrete frames with FRP reinforcement can provide signification strengthening and stiffening to concrete frames and improve their behaviour under different types of loading. The selections of types of FRP and the architecture of composites in order to improve the bonding and strength of the retro-fitting were also discussed.Author Keywords: Concrete structure; Strengthening; Rehabilitation; Hybrid FRP composite; Wrapping technique1. IntroductionA widely adopted technique for retrofitting concrete structure is to use steel jackets placed around existing concrete columns [1 and 2]. The use of steel encasement to provide lateral confinement to the concrete in compression has been studied extensively[3 and 4], and has shown increase in the compression load carrying capacity and ductility of the concrete columns. However, the shortcomings of this technique are that it suffers from corrosions as well as inherent difficulties during practical applications. Fibre reinforced plastic (FRP), on the other hand, is increasingly being used to reinforce concrete, masonry and timber structures. The load carrying capacity and serviceability of existing structures can be significantly augmented through externally retrofitting critical sections with FRP sheeting. In recent years FRP materials with wide range of fibre types of glass, aramid or carbon provide designers with an adaptable and cost-effective construction material with a large range of modulus and strength characteristics. Comparing with traditional rehabilitation techniques, the FRP composites have high specific strength/stiffness, flexibility in design and replacement as well as robustness in unfriendly environments. With FRP composites it is possible and also necessary to achieve the best strengthening results by optimising the constitute materials and architecture. Optimisation of the constitute materials and architecture becomes essential in order to utilise the superiority of FRP composites in application of rehabilitation [5, 6, 7, 8 and 9]. It was found that winding of carbon fiber/epoxy composites around square concrete columns can increase the load carrying capacity by 8–22%, depending on the amount of fibres used and treatments of substrate surface [10]. The use of resin infusion technique was shown to contribute to substantial improvements in composite wrapping efficiency, and the use of woven glass roving, as the reinforcement in composites wrapping, was found to significantly increase both load carrying capacity and deformation resistance capacity of the concrete stubs [2]. Furthermore, through the use of glass/carbon hybrid reinforcements with an epoxy resin, replication of initial performance of concrete stubs subjected to deterioration was shown possible, with a simultaneous further improvement in load carrying capacity. In terms of the effects of orientation and thickness of the composites warps, it was found that the predominant use ofreinforcements in the hoop direction would result in high efficiency [11]. Despite the large number of research carried out, one shortcoming of most studies has been that they were limited to simple small size components, such as concrete cylinders, rather than real structures. Furthermore, it is essential to study the optimisation of composites architectures in terms of cost effectiveness including materials and processing methods. This implies that the reinforcement of infrastructure with FRP composites should utilise the advantages of various materials, not only carbon fibers with epoxy resin, but also glass fiber or hybrid of carbon/glass fibres with other polymer resins. In this experimental investigation, a hybrid of carbon/E-glass with vinyl-ester resin composites jacket was designed to reinforce a typical building components, namely a column–beam connection. Static tests were then conducted on FRP reinforced and non-reinforced specimens with extensive instrumentation to study the influence of the designed composite reinforcement. The investigation reported in the paper forms part of a collaborative research program between the University of Technology, Sydney and the Centre for Advanced Materials Technology, the University of Sydney in relation to application of advanced fibre composites to strengthen, stiffen and hence rehabilitate concrete structures.2. Experimental proceduresThree prototype size reinforced concrete frame specimens, representing typical concrete column–beam connection, were designed for this study. Geometry of the specimens with location of FRP composite reinforcement is illustrated in Fig. 1. Among three specimens, two of them are as-is concrete beam–column connection type (none composites-reinforced (Non-CR) specimens) and one specimen was reinforced by the hybrid of carbon fiber and glass fibre composites around the column–beam joint (composites-reinforced (CR) specimen). All three specimens were pre-cast using standard commercial mix grade 40 concrete. The steel reinforcement of the concrete specimens are also shown in Fig. 1. Concrete compression tests based on the Australian Standard (AS 1012–1986) were conducted on the samples taken during the concrete pour in order to determine the modulus of elasticity and ultimate compression strength (UCS) of the concrete.2.1. Composites architectureOne of the three concrete frame specimens was reinforced with hybrid composites. The hybrid composites consists of four basic architectures, namely E-glass woven roving (WR/600 g/m2), chopped strand mat (CSM-300 g/m2), carbon cloth (plain weave-200 g/m2) and glass fibre tape (GFT-250 g/mm2). The details of the composites architecture are shown in Table 1 and Fig. 2. Details of lay-up are illustrated in Fig. 3. WR and carbon cloth are a multi-directional reinforcement with biaxial plain weaving which provide equivalent strength in both axial and hoop directions. They play the basic reinforcement role in this composites architecture. GFT applying at hoop direction provides very good confinement and enhances structural integrity. The selection of resin curing systems is mainly concerned with the resin gel-time at ambient temperature, which is critical to wrapping process. In general, cold setting resin systems (ambient temperature curing) can be used when wet lay-up process is applied. Since no lay-up machine is available for the wrapping process described in this study, the hand lay-up method was used. The vinyl-ester resin, Dastar-R/VERPVE/SW/TP, was mixed with 1.5% of MEKP(methyl-ethyl-ketone-peroxide), 0.4% of CoNap (Cobalt napthenate), and 0.5% of DMA(Dimethylaniline) at ambient temperature. The resin cures at ambient temperature. The weight ratio between resin and fibre layers was 1:1.5 for WR/CSM layers and 1:0.8 for carbon cloth, respectively. The concrete frame was wrapped by a lames-wool roller and a consolidating roller. Before laying the first fibre layer, the concrete surfaces were cleaned up using acetone, and a thin resin coat was applied to seal micro holes on the surface of concrete columns. However, further surface treatment such as sanding surface to expose the aggregates was intentionally avoided. Each composite layer was wetted with the resinand rolled onto the concrete frame to ensure full consolidation.Table 1. Details of five composite systems with a compositearchitectures2.2. Design of static testsThe static tests of the concrete frame specimens were setup in a horizontal plane. The three supports of the concrete frame (no load applied) were roller type as shown in Fig. 4. The end at which load was applied was also a roller type support, however, horizontal movements were obviously not prevented. In order to provide the ideal roller type boundary conditions at each end as designed, a special setup was developed with combination of rollers and a swivel head at each supporting/loading point (Fig. 5). Four 1000-kN-hydraulic jacks were used in the tests. Among them, the only active jack was the jack that applied loads, while others were simply acting as adjustable packing to providing the reactions.Fig. 4. Illustrative sketch of test set-up for static test.Fig. 5. Set-up for static test of concrete frame.2.3. Instrumentation and data loggingApplied load as well as reaction forces were measured using four 998.8 kN load cells located in each of four supporting/loading positions. In order to obtain detailed flexural deflection curves for the concrete frame specimens, twelve linear variable displacement transducers (LVDTs) with a range from ±2.5 to ±50 mm were used at strategic locations to measure the flexural deflections. Extensive strain gauging was designed to capture the stress distribution of the testing specimens in order to validate tests and gain an insight into the behaviour of the concrete frame with or without FRP reinforcement. The total number of strain gauges was 56 for each specimen, in which 28 strain gauges (5 mm) were located on steel rebars and the rest (30 mm strain gauges) were located on the external surface of the concrete frame specimens. Locations of the strain gauges were arranged so that the strains on various points of the cross sections could be captured. A typical strain gauge arrangement for most measured cross sections is shown in Fig. 6. Locations of strain gauges inside the section are shown in Fig. 7.Fig. 6. Location of cross sections of the concrete frame for strain gauging.2.4. Test procedureDesignations of test specimens and a brief description are given in Table 2. Prior to being formally tested at service load level, the first non-CR specimen was subjected to a series of investigative tests mostly loaded at the service load level of 40 kN with one single overload up to 50 kN. The second non-CR specimen and the CR specimens were not subjected to any loading until the initial service load level tests. All ultimate load tests were conducted after every specimen was exposed to about 100 cycles of cyclic loading atservice load levels.Table 2. Applied load and reactions for typical tests (unit: kN)3. Results and analysisIn order to determine the influence of FRP composites, five sets of tests were conducted on the three specimens including three tests at service load levels and two atthe ultimate load level. For every test, logged data consisted of four load records, twelve deflection records and 56 or 64 strain records.3.1. Validation of the static testsTo validate the performed tests, the static equilibrium for each test was verified as follows:Equilibrium of external loads: As redundancy was avoided in design of these tests and load cells were placed at each loading or reaction point, it was convenient to check equilibrium of the load/reaction forces through simple statics. Table 2 shows that the equilibrium of external loads was satisfied.Equilibrium of forces and equilibrium of moment on cross sections: In order to calculate the internal forces and sectional moments, strains on the designated sections were required. To process the measured strains on a given cross section, the following assumption was made: the strains vary linearly through the cross sections. In other words the strains at a given cross section can be represented by a strain plane. Under this assumption, least square method with the two explanatory variables was adopted to obtain the strain plane for each given cross section using values of six measured strains. Fig. 8 shows comparison of the measured strain values and those calculated from the least square fitting. The strain values used in subsequence evaluations or calculations were obtained from calculated strain planes. For the validation of the equilibrium of internal forces in a given cross section, forces were calculated by integration of resulting stresses in tension and compression zones, respectively. The concrete was assumed to carry only compression loads and steel rebars (with FRP composites in some cases) were considered as the main load carriers in the tension zone. Equilibrium states that the resultant force in the compression zone should be equal to that in the tension zone. Moments at a given cross section were firstly calculated through integration of stresses in the section. They were compared to those calculated by using measured loads multiplied by the lever arms.Details of formulae pertained to these calculations are presented in Appendix A. As shown in Table 3 and Table 4, equilibrium is validated.Fig. 8. Comparison of measured vs calculated strain values from least square fitting.Table 3. List of calculated internal force and moments at section A-A of a non-CRspecimenTable 4. List of calculated internal force and moments at section A-A of a CR specimen3.2. Load–deflection curvesComparison of load–deflection curves for CR and non-CR specimens at both service load and ultimate load levels are shown in Fig. 9 and Fig. 10. About 45% increase in stiffness was observed due to the presence of FRP composites reinforcement (service load level). Results of the ultimate loading test indicated an increase in load carrying capacity of CR specimen of approximately 30% due to the presence of FRP composites.3.3. Analysis of the strain resultsTo evaluate change of strain in steel rebars due to FRP reinforcement, a parameter was defined, namely "average strain reduction". It is defined aswhere P is the average of maximum section strains of the two none composites-reinforced (non-CR) specimens and R is the maximum section strain of composites-reinforced (CR) specimen at the same load level. Table 5 and Table 6 summarise the typical comparison of maximum/minimum strains between non-CR and CR specimens and average strain reduction in various cross sections at same load level (see also Fig. 11). If one takes the mean of the average strain reductions for all beam-sections, it yields strain reduction factor of 51%. In same way, the mean of the average strain reductions for all column-sections is 55%. The average strain reduction can be used as an indication of external FPR reinforcement efficiency.Table 5. Comparison of the maximum strains in the rebars for beam sections (unit: )Table 6. Comparison of the maximum strains in the rebars for column sections (unit:)Fig. 11. Comparison of strains of CR and non-CR specimens in steel rebars at a given section.3.4. Discussions on applied composites architectureResults from both service load level tests and ultimate load test of the concrete frames show that the proposed composites architecture successfully enhanced the original structure in terms of stiffness and load carrying capacity. It is interesting to note that although the elastic modulus of FRP composites is only approximately half of that of concrete, the increase in stiffness and load carrying capacity of a reinforced concrete was significant. Despite of absence of special surface treatment of concrete before the application of FRP composite reinforcement, the bonding between the concrete and composites did not fail. This may be owing to the lower elastic modules of hybrid composites. There is an indication that low modulus FRP may provide better reinforcement/retrofitting for concrete structures because of low tensile strength in concrete. In the lay-up design, the gradual change of thickness is essential. It will reduce possible stress concentration in the FRP composites which could cause delamination or cracking. However, it is important to point out that because only a limited number of specimens were studied, some of these conclusions may be biased. It is suggested to conduct more tests to confirm these results.4. ConclusionsAs results of this study, the following conclusions can be drawn:1. Tests on prototype size reinforced concrete frame specimens, designed to represent the column–beam connections in plane frame, have been successfully conducted. Test results were validated through equilibrium checks.2. Designed hybrid composites consisting of roving cloth, carbon cloth, and chapped strand mat and glass fibre tape demonstrated effectiveness in reinforcing concrete structures. The results from the tests show significant increases in stiffness and load carrying capacity due to reinforcement provided by hybrid FRP composites. The resultsalso show that optimisation is important in reinforcing concrete structures to achieve good results with low cost.3. The results of static tests also suggest that hybrid carbon/E-glass fibre composites with low elastic modulus may contribute to good bonding and non-delamination. However, this needs to be confirmed by more tests.4. It is also suggested that further investigation be carried out including reinforcing damaged concrete frame specimens, cyclic loading and using different composites architectures.Appendix AAssuming that at a given cross section of beam/column strain distribution is linear, for the given section, strain can then be expressed in form of(x ,y )=ax +by +c ,(A .1) where a , b , c are constants.Consider a two explanatory variables regression modelYi =0+1x i 1+2x i 2+e i , (A.2)where x i 1 represents the i th observation on explanatory variable X 1 and x i 2 denotes the i th observation on second explanatory variable X 2.One can obtain a best fit strain plane from measured strain in a given section.Under linear strain distribution assumption, a closed form solutionfor force and moment at the cross section using strain data can be obtained by double integration. In compression zone for the concrete (refer to Fig. 12), one obtains:(A.3)where E is the modulus of the elasticity of concrete; a , b and c are constants in Eq.(A.1); F I is the resultant force in the compression zone.(A.4)where M I is the moment at the compression zone.Fig. 12. Schematic drawing of a typical cross sectionof concrete frames. For steel rebars and composites (if applied):(A.5)where F I S and F I C are forces in steel rebars and composite, respectively. In tension zone, only steel rebars and composite count, formulae are similar to Eq. (A.5).具有混合纤维增强塑料片的混凝土梁–柱联接部位的加固摘要本篇文章描述了对加固后标准尺寸混凝土结构试件进行试验的结果,该试件代表平面框架结构中的梁–柱联接部位。
硅烷偶联剂改性纳米碳酸钙在PVC复合材料的应用研究
作者简介:邓传福(1982-),工程师,主要从事建筑材料的开发和检测工作。
收稿日期:2023-05-05聚氯乙烯(PVC )是一种廉价易得的聚合物材料,在鞋材、管道管件、电线电缆、压延膜等行业有着广泛的应用[1]。
但众所周知,纯PVC 材料由于其韧性差和热稳定性不足,在许多应用中都存在局限性[2]。
因此,在许多行业中,开发了用各种填料改性的PVC 复合材料,以提高机其械性能和热稳定性能[3]。
高岭土[4]、硫酸钙[5]、碳酸钙[6]、滑石粉[7]、和二氧化硅[8]等无机填料已被证明可用于增强聚合物树脂的物理性能。
但显而易见,聚合物基体和填料之间的界面相将对复合材料的物理性能起着关键作用。
不幸的是,无机材料表面一般都呈现为强极性,与聚合物材料通常不相容,这无疑会导致无机填料与聚合物之间的无法形成有效的界面层。
为了克服上述问题,最常用的方法就是对无机填料进行表面改性,以改善其与聚合物材料之间的相容性。
目前市场上也出现了多种性能不俗的表面改性剂,如硅烷偶联剂、铝酸酯偶联剂、钛酸酯偶联剂等,在不同填料的改性上都有着广泛的应用。
然而目前的理论和实践普遍认为,由于碳酸钙表面羟基含量不高,因此并不适合使用硅烷偶联剂作为其表面改性剂,虽有部分研究者采用溶剂法可成功在碳酸钙表面接枝上硅烷偶联剂[9],但成本因素几乎不可能工业化应用。
在本文的研究中,我们在纳米碳酸钙的制备过程中通过引入不同剂量的羟基,考察后期硅烷偶联剂对硅烷偶联剂改性纳米碳酸钙在PVC复合材料的应用研究邓传福1,颜干才2, 杜年军2(1.钦州市建筑工程质量检测中心有限公司,广西 钦州 535000; 2.广西平果市润丰钙新材料科技有限公司,广西 平果 533822)摘要:采用γ-氨丙基三乙氧基硅烷(KH -550)对纳米碳酸钙进行特殊表面改性,利用扫描电镜(SEM )、红外光谱(IR )、热机械分析仪(TMA )、热重分析仪(TG )、转矩流变仪等测试手段,探究了改性后的纳米碳酸钙对聚氯乙烯(PVC )复合材料综合性能的影响。
大学英语六级综合-阅读(二十二)
大学英语六级综合-阅读(二十二)(总分:100.00,做题时间:90分钟)一、Reading Comprehension(总题数:0,分数:0.00)二、Section A(总题数:0,分数:0.00)三、Passage One(总题数:1,分数:10.00)Rather than using custom machine tools to build early models of new parts, Ford is now using 3-D printing technology to design and test its engineers' latest ideas. The new method allows product developers to have a (1) in their hands in as little as a week after they create a new design—compared with having to wait three to four months (2) ."We're building more and more parts every day using this (3) ," says Harold Sears, a technical expert in rapid manufacturing at Ford's design facility in Dearborn, Mich. Ford's new hybrid transmission was developed on a 3-D printer that costs about $300,000 and which can turn a pile of aluminum powder into a working prototype in a day or two.While low-cost 3-D printing by consumers and small businesses looks like a market now ready for takeoff, large businesses have already (4) advanced versions of the technology. The result has been a (5) improvement in the product-development process across a wide range of industries, including the (6) of cars, consumer electronics, safety equipment and medical devices.The process has done more than just save time and money. Engineers say rapid prototyping using 3-D printing is producing more (7) , higher-quality products—from custom-fitted bicycle helmets to better-sounding ear buds and loudspeakers.Instead of waiting for tools and parts to come back from outside machine shops or injection-molding houses, product developers on tight (8) now get more hands-on time to test their models. 3-D printers allow them to test and (9) more versions of their prototypes—in some cases tripling the number of duplicates of a new product that can be (10) before being produced on a large scale.A. previouslyB. thereafterC. processD. elasticE. deadlinesF. manufacturingG. significantH. innovativeI. ignitedJ. embracedK. lubricate L. prototype M. refined N. update O. mechanisms(分数:10.00)填空项1:__________________ (正确答案:L)解析:[解析] 冠词a提示空格处应填入名词。
专业英语第十六章原文
The History Of Chinese CeramicsIt was the Chinese who,very early and independent of foreign influences , developed the craft of pottery into a fine art Their ceramics was one of the great major Oriental contributions to civilization.As early as 3000 BC , potters in Henan and Gansu produced a technically superior pottery . Porcelain , a ceramic that is adaptable to higher firing temperatures than earthenware and is harder, more translucent , and white after firing ,was achieved some time after A.D.600.The secret of its composition was well guarded by China and not discovered in the West for over 1000 years.The discovery of porcelain in China itself was probably an accident.Stoneware ——a hard stonelike pottery with many porcelain characteristics——appeared quite early in China , and its evolution into true porcelain may have resulted from a casual addition of an infusible white rock called petuntse and the white clay known as kaolin to the stoneware mixture .Henan Ware . The earliest ordinary Chinese pottery came from Henan and was made by hand , probably on a slow wheel , and shaped into ritual funerary vessels as well as ordinary objects . Made from brown , red , and buff clay , it was well shaped , thin , and of exceptional dignity and beauty of proportion . The outstanding pieces were painted brilliant red , black , purple , and white before firing . A more crude Henan ware , coarse and of a gray tone , was modeled by hand . Its primitive decoration consisted only of marks left by matting or rough cloth pressed against the clay while it was still wet . Unlike its predecessor , this ware continued to be made , both for everyday and decorative objects , for about one to two thousand years , even into the Han Dynasty (206B. C.—A. D.220). The third great Henan ware was created from a kaolinic clay , which produced in a sharp , fret pattern like the bronzes of this ware which have been found are carved in a sharp , fret pattern like the bronzes of the same period . This beautiful pottery may , however , have been made simply for use as molds .Han Ware . During the Han Dynasty——a period contemporary with the greatest years of Rome——Chinese ceramics took great strides forward . Molds were now used to create whole objects rather than , as previously , merely to apply relief work to the surface . The potter's wheel was improved , and elaborate painted decorations and incised patterns were used . Slip decoration ( liquid clay applied in swirls or dots ) was devised , as were colored glazes . From Rome came thetechnique of lead glazes .T'ang Ware . Even greater advances took place during the T'ang Dynasty (A. D.618—906) . Funerary objects from T'ang tombs boast molded Hellenistic reliefs of dancing figures , some holding the pipes of Pan , indicating a regular cultural interchange between East and West . Small yellow or green-glazed grave figures of priests , soldiers , bowls , and jars , have also been unearthed . At the same time , the development of the tea ceremony brought refinements both in manners and in ceramic designs . Poets likened a thin T'ang pottery to jade , ice or even a lotus blossom floating on ice . The creation of a kaolinic stoneware foreshadowed the development of porcelain ; its hard , gray green glaze , for which smoke from wood ashes was probably inadvertently responsible ( as was the presence of iron in the clay ) , is a forerunner of the famous celadon glaze ( a translucent green glaze having a velvety texture ) .During this period , the potter's technical skills had increased enormously . He could make many colored glazes and wares made from the newly discovered porcelain were exported to Europe and the Near East .Sung Ware . The Sung period (960—1260 ) , especially after the establishment of the southern capital in 1127 , represents a cultural pinnacle when all arts expressed the ideal of harmony between man and nature . It was with the Sung porcelains that Chinese ceramic art truly matured . The Chinese use of the term porcelain at this time included not only the "pure" porcelain (with a white translucent body ) but also those with gray and dusky bodies which had been fired to such a state of vitrification that they emitted a musical note when struck . This musical note was the principal test of early porcelains in China .A wide cleavage occurred between the art of the porter and that of the metal worker , and in the most important wares of the long , heavy shapes resembling metalware which had characterized earlier Chinese ceramics were replaced by light , simple , delicately glazed form . Only at the end period did enamel decoration and some ceramic painting appear on the glazes .The earliest of the Sung wares was the Ju ware . It was first made with an iridescent , blue-gray glaze in northern China , near Kai Feng Fu for the imperial household befors it moved south in the twelfth century to escape the Tartars . Thereafter , in the north , the Sung Ju ware was presumably different and darker , though no positive examples of Ju ware survive .There are many existing examples of the next sung ware , Ko ware , which was produced fora long time , Ko ware was dark and had a thick , crackled , gray , yellowish , or gray-green glaze . Pegmatite was eventually added to vary and control the crackle .Of the various types of Ting ware , the ivory-white porcelain made in Southern Chihli , with a dull , white body and sometimes an ivory glaze , is considered the finest . Dishes and bowls often had a band of metal around their rough , unglazed upper rims . Since its appearance in the twelfth century , this ware has been widely imitated , and in the sixteenth century the potter Chou Tan-ch' uan started an entire school of Ting-ware copyists .The heaviest of the Sung wares was the opaque , vitreous Chun ware , from which "tulip" bowls were fashioned . It had a bubbly glaze ( from mixing feldspar and copper with the kaolin body in oxidizing flames of round kilns ) which often broke into Y-shaped lines called earthworm marks . Sometimes , on the lavender-colored pieces , an underlying design of birds or flowers showed through the glaze .The Chien stoneware from Fujian Province , used primarily for teacups , owed much of its popularity to the tea-drinking ceremony . This ware was black or brown , and the lines in the surface , caused by the presence of iron in the glaze , produced a pattern resembling "hare's fur" or "partridge feathers" .From the district of Tz'u Chou , a pottery center since the sixth century , came a superb gray stoneware covered in white slip and decorated with incised or painted flowers ,Sgraffito (scratched) decorations , or red , yellow , or green enamel overglaze painting , were sometimes used .Ming Ware . Early pieces of the Ming Dynasty ( A. D.1368—1644),with their massive shapes , applied figures , foliage , pendants , and raised outline , are reminiscent of Western , Asian , and Assyrian brickwork . The Ming techniques differed from the Sung and earlier methods . In one ware , firing preceded glazing and Persian colored glazes were superimposed on one another and fired at a low temperature . The effect , although brilliant , seems almost archaic in comparison to the lighter , smoother Sung finishes .Because of the concentration of workmen at the Imperial factory at Kingtehchen , technical knowledge increased in the early Ming ear at an unprecedented rate . Later , a fine porcelain with a transparent , pure white glaze was produced . A beautiful cobalt-blue glaze was found to withstand intense heat and was therefore applied under the transparent porcelain glaze . An even finer blue , Mohammedan blue , was at times imported and used , at first only for Imperial piecesbut later for more general distribution . Brilliant red glazes were similarly applied .Eighteenth-and Nineteenth-Century Ware . During the eighteenth century , a revival took place in China of early types of ceramics which showed the enormous historical scope of Oriental art . New inventions like "iron rust " and "tea-dust" glazes became very popular during the reign of Ch'ien Lung (1735 —1796), as did "famille rose" (Chinese porcelain decorated mainly in green) . Crude armorial china , made for export to Europe , where it was well received , often was decorated at Canton instead of at Kingtehchen . The abandonment of underglaze painting in favour of overglaze decoration changed porcelain painting from a bold brushwork technique to a careful art similar to engraving .A provincial factory in Fujian devoted mostly to manufacturing coarse porcelain for export to India , operated through the seventeenth , and nineteenth centuries . For European markets it produced a white ware called "blanc de chine" in France . Since the Ming dynasty , presumably to the present , Fujian has also produced ornamental objects and figure subjects .Throughout China , many small factories have always produced quantities of stoneware and ordinary pottery . From Jiangsu Province came a stoneware in red and othercolors in which tea was shipped to Europe as early as the seventeenth century . decoration was in the form of reliefs and molded and incised patterns . Europeans copied the shapes , colors , and ornaments of this ware with considerable fidelity , especially in eighteenth-century Saxony , and called the results "bucchero" ware .After Europe discovered the secret of porcelain , its ceramic imports from the Orient decreased . Its commercial incursions into China created such political unrest there that even the Imperial patronage of factories lessened and no porcelain of importance , except for the famous Peking Medallion Bowl and some mid-nineteenth-century snuff bottles , was produced after the early nineteenth century .。
外文翻译---通过建筑结构设计以改善建筑物的抗倒性
外文原稿2The Twelfth East Asia-Pacific Conference on Structural Engineering and ConstructionDesign of Building Structures to Improve their Resistanceto Progressive CollapseD A Nethercot aa Department of Civil and Environmental Engineering, Imperial CollegeLondonAbstract:It is rare nowadays for a “new topic” to emerge within the relatively mature field of Structural Engineering. Progressive collapse-or, more particularly, understanding the mechanics of the phenomenon and developing suitable ways to accommodate its consideration within our normal frameworks for structural design-can be so regarded. Beginning with illustrations drawn from around the world over several decades and culminating in the highly public WTC collapses, those features essential for a representative treatment are identified and early design approaches are reviewed. More recent work is then reported, concentrating on developments of the past seven years at Imperial College London, where a comprehensive approach capable of being implemented on a variety of levels and suitable for direct use by designers has been under development. Illustrative results are used to assist in identifying some of the key governing features, to show how quantitative comparisons between different arrangements may now be made and to illustrate the inappropriateness of some previous design concepts as a way of directly improving resistance to progressive collapse.2011 Published by Elsevier Ltd.Keywords:Composite structures; Progressive Collapse; Robustness; Steel structures; Structural design1. IntroductionOver time various different structural design philosophies have been proposed, their evolutionary nature reflecting:*Growing concern to ensure adequate performance.*Improved scientific knowledge of behaviour.*Enhanced ability to move from craft based to science based and thus from prescriptive to quantitatively justified approachesThis can be traced through concepts such as: permissible stress, ultimate strength, limit states and performance based. As clients, users and the general public have become increasingly sophisticated and thus more demanding in their expectations, so it became necessary for designers to cover an ever increasing number and range of structural issues–mostly through consideration of the “reaching this condition would be to a greater or lesser extent unacceptable”approach. Therefore issues not previously considered (or only allowed for in an implicit, essentially copying past satisfactory performance, way) started to require explicit attention in the form of: an assessment of demand, modelling behaviour and identification of suitable failure criteria. The treatment of topics such as fatigue, fire resistance, durability and serviceability can all be seen to have followed this pattern.To take a specific example: designing adequate fire resistance into steel framed buildings began (once the need had been recognised) with simple prescriptive rules for concrete encasement of vulnerable members but it has, in recent years, evolved into a sophisticated discipline of fire engineering, concerned with fire loading, the provision of protective systems such as sprinklers, calculation of response in theevent of a fire and the ability to make quantitative comparisons between alternative structural arrangements. Not only has this led to obvious economic benefits in the sense of not providing fire protection where it gave only negligible benefit, it has also led to increased fire safety through better understanding of the governing principles and the ability to act intelligently in designing suitable arrangements based on a proper assessment of need.Prior to the Ronan Point collapse in London in 1968 the terms robustness, progressive collapse,disproportionate collapse etc., were not part of Structural Engineering vocabulary. The consequences of the damage done to that 22 storey block of pre-cast concrete apartments by a very modest gas explosion on the 18th floor led to new provisions in the UK Building Regulations, outlawing for many years of so called system built schemes, demolition of several completed buildings, temporary removal of gas in high rise construction and the formation of the Standing Committee on Structural Safety. Eventually, the benefits of properly engineered pre-fabrication were recognised, safe methods for the installation of gas were devised and the industry moved on. However, the structural design guidance produced at that time - that still underpins much present day provision - was essentially prescriptive in nature with no real link to actual performance.Subsequent incidences of progressive collapse such as the Murragh Building and the World Trade Centre brought increased attention to the actual phenomenon and issues of how it might reasonably be taken into account for those structural designs where it was considered appropriate. In doing this it is, of course, essential to include both the risk of a triggering incident and the consequences of a failure so that the resulting more onerous structural demands are used appropriately. Arguably, a disproportionate response in terms of requiring costly additional provisions in cases where the risks/consequences are very low/very minor may be as harmful as failing to address those cases where the risks/consequences are high/severe.This paper will review current approaches to design to resist progressive collapse and contrast these with work undertaken over the past seven years at Imperial College London, where the goal has been the provision of a realistically based method suitable for use in routine design. The essential features of the method will be presented, its use on several examples described and results presented to illustrate how it is leading to a better understanding of both the mechanics of progressive collapse and the ways in which structural engineers can best configure their structures so as to provide enhanced resistance2.Design to resist progressive collapseThe two most frequently used design approaches intended to address the issue of progressive collapse are:*Providing tying capacity*Checking alternate load pathsFigure 1: Tie Forces in a Frame StructureThe first is essentially prescriptive and consists of ensuring that beams, columns, connections and floor (or roof) can act together to provide a specified minimum level of horizontal tying resistance; the actual values required are normally related to the vertical loading. Figure 1, which is taken from recent US Guidance (SEI 2010), illustrates the principle. The approach is simple to appreciate, requires minimal structural calculation and, in situations where the original provisions are found to be inadequate, can be made to work by providing more substantial connections and/or additional reinforcement in floor slabs In an interesting recent development, that recognizes the link to the generation of catenary action, US Guidance has restricted the use of tying between the structural members to situations in which it can be demonstrated that the associated connections can carry the required forces whilst undergoing rotations of 0.2 radiance. Where this is not possible, tying should act through the floors and the roof. However, recent studies (Nethercot et al 2010a; Nethercot et al 2010b) have suggested that tying capacity correlates poorly with actual resistance to progressive collapse. Moreover, being prescriptive, it does not permit the meaningful comparison of alternative arrangements - a fundamental feature of structural design.In its most frequently used form the alternative load path approach presumes the instantaneous loss of a single column and then requires that the ability of the resulting damaged structure to bridge the loss bedemonstrated by suitable calculation (Gudmundsson and Izzuddin 2010). The approach may be implemented at varying levels of sophistication in terms of the analysis; for example, recent thinking in the United States (SEI 2010) makes provision for any of: linear static, non-linear static or non-linear dynamic analysis and provides some guidance on the use of each. It may also be used as the basis for more sophisticated numerical studies of particular structures and particular incidents e.g. forensic work; the best of these–which are likely to be computationally very demanding–have demonstrated their ability to closely replicate actual observed behaviour.3. Essential features of progressive collapseThree features have previously (Nethercot 2010) being identified as essential components of any reasonably realistic approach to design against progressive collapse:*Events take place over a very short timescale and the actual failure is therefore dynamic.*It involves gross deformations, generating large strains, leading to inelastic behaviour as well as change of geometry effects.*Failure essentially corresponds to an inability of the structure in its damaged state to adopt a new position of equilibrium without separation of key elements.Figure 2: Simplified multi-level approach for progressive collapse assessmentAdditional features, designed to make the approach attractive for use by practicing Engineers have also been proposed (Nethercot 2010):*Process should consist of a series of steps broadly similar in concept to those used for “conventional” structural design.*It should, preferably, be capable of implementation at a variety at levels of complexity–with the choice reflecting the importance of thestructure.*Any required analysis should utilise familiar techniques; where these require computations beyond “hand methods”, these should be based on the use of available analysis software.* A realistic and recognisable criterion of failure should be used. *Approach should permit study of cause and effect and be suitable for the making of quantitative comparisons.It was against this background that the studies at Imperial College London have been undertaken. An approach incorporating the three essential features but observing the five desirable features was originally developed (Vlassis 2007); it has subsequently been refined (Stylianidis 2010). Although the starting point was column removal, the approach contains a number of distinctive features:*Although dynamic response is allowed for, only static analysis is required (Izzuddin et al 2007).*The approach may be implemented at structure, sub-structure, floor grillage or individual beam level, see Figure 2.* A realistic criterion of failure is employed, corresponding to reaching the ductility limits in connections.*Quantitative comparisons between alternative structural arrangements may readily be made.*The approach may be implemented using only explicit formulae, thereby permitting simple and rapid calculation.Full details of the method, both in its original form which utilises ADAPTIC to perform the calculations and in its simplified form, may be found in the series of Imperial papers (2-12).*a) First yielding of the tensile components (top bolt row of the support connection)*b) Ultimate capacity of the beam flange at one of the connections (support)*c) Ultimate capacity of the system (failure of the bottom bolt row of the mid-span connection)*d) The axial load becomes zero (the deflection of the beam where the axial load changes from compressive to tensile)*e) The deflection of the beam where the axial load becomes equal to the flange capacity of one of the connections (mid-span connection)Figure 3: Non-linear static response for a single beam中文翻译2通过建筑结构设计以改善建筑物的抗倒性D A Nethercot a土木与环境工程学院——伦敦帝国学院摘要:如今的“新话题”出现在相对成熟的结构工程领域这是一件罕见的事。
新视野读写教程第四册Unit6 Text A 课文详解
Section A T h e w e i g h t m e n c a r r y
Some had partial vision loss as the glow of the welding flame damaged their optic receptors. There were times, studying them, when I dreaded growing up. All around us, the fathers always seemed older than the mothers. Men wore out sooner, being martyrs of constant work. Only women lived into old age.
Section A T h e w e i g h t m e n c a r r y
4 These weren’t the only destinies of men, as I learned from having a few male teachers, from reading books and from watching television. But the men on television – the news commentators, the lawyers, the doctors, the politicians who levied the taxes and the bosses who gave orders – seemed as remote and unreal to me as the figures in old paintings.
Section A T h e w e i g h t m e n c a r r y TLeaxntgsutaugdey Focus
MaterialsScienceandEngineeringA材料科学与工程A卷Vol.589
Materials Science and Engineering: A材料科学与工程:A卷V ol.589, 1 Jan. 2014序号目次信息1 篇名:Micro–macro-characterisation and modelling of mechanical properties of gas metal arc welded (GMA W) DP600 steel采用气体金属电弧焊接的DP600钢的微–宏观表征及力学性能建模作者:A. Ramazani, K. Mukherjee, A. Abdurakhmanov, U. Prahl, M. Schleser, U. Reisgen, W. Bleck2 篇名:Deformation behavior in the isothermal compression of Ti–5Al–5Mo–5V–1Cr–1Fe alloyTi-5Al-5Mo-5V-1Cr-1Fe合金的等温压缩变形行为作者:S.F. Liu, M.Q. Li, J. Luo, Z. Yang3 篇名:Dynamic recrystallization kinetics in α phase of as-cast Ti–6Al–2Zr–1Mo–1V alloy during compression at different temperatures and strain rates铸态Ti-6Al-2Zr-1Mo-1V合金在不同的温度和应变率下压缩时α相的动态再结晶动力学作者:Guo-zheng Quan, Dong-sen Wu, Gui-chang Luo, Y u-feng Xia, Jie Zhou, Qing Liu, Lin Gao4 篇名:Effect of dynamic strain aging on isotropic hardening in low cycle fatigue for carbon manganese steel动态应变时效对碳锰钢在低周期疲劳下各向同性硬化的影响作者:Zhi Yong Huang, Jean-Louis Chaboche, Qing Y uan Wang, Danièle Wagner, Claude Bathias5 篇名:Hot deformation mechanisms, microstructure and texture evolution in extruded AZ31–nano-alumina composite受挤压的AZ31纳米氧化铝复合材料的热变形机制、微观结构以及织构演变作者:T. Zhong, K.P. Rao, Y.V.R.K. Prasad, F. Zhao, M. Gupta6 篇名:The method for reproducing fine grained HAZ of W strengthened high Cr steel用于再现强化高Cr钢钨细粒HAZ的方法作者:Xue Wang, Qiang Xu, Hong-wei Liu, Hong Liu, Wei Shang, Yao-yao Ren, Shu-min Y u7 篇名:Influence of Mn solute content on grain size reduction and improved strength in mechanically alloyed Al–Mn alloys锰溶质浓度对晶粒尺寸的减小和改进机械合金化的铝锰合金的强度的影响作者:K.A. Darling, A.J. Roberts, L. Armstrong, D. Kapoor, M.A. Tschopp, L.J. Kecskes, S.N. Mathaudhu8 篇名:Self-consistent modelling of lattice strains during the in-situ tensile loading of twinning induced plasticity steel孪生诱发塑性钢的原位拉伸加载过程中的晶格应变自洽建模作者:Ahmed A. Saleh, Elena V. Pereloma, Bjørn Clausen, Donald W. Brown, Carlos N. Tomé, Azdiar A. Gazder9 篇名:Constitutive description of high temperature flow behavior of Sanicro-28 super-austenitic stainless steel对sanicro-28超级奥氏体不锈钢的高温流动行为的本构描述作者:A. Mirzaei, A. Zarei-Hanzaki, N. Haghdadi, A. Marandi10 篇名:Influence of raw material selection and fabrication parameters on microstructure and properties of micro-laminated TiB2–TiAl composite sheets原材料的选择和工艺参数对微叠层TiB2–TiAl基复合材料板材的微观结构和性能的影响作者:Xiping Cui, Guohua Fan, Lin Geng, Hao Wu, Jincheng Pang, Jinxin Gong11 篇名:Stress-induced thickening of Ω phase in Al–Cu–Mg alloys containing various Ag additions在含有各种银附加物的铝-铜-镁合金中的压力诱导Ω相增作者:Song Bai, Zhiyi Liu, Xuanwei Zhou, Peng Xia, Meng Liu12 篇名:Effect of plate-like alumina on the properties of alumina ceramics prepared by gel-casting板状氧化铝对用凝胶浇注法制备的氧化铝陶瓷性能的影响作者:Meiqi Cao, Qingzhi Yan, Xianhui Li, Yingying Mi13 篇名:Microstructure–properties relationship in a one-step quenched and partitioned steel一步淬火和分段钢化之间的微观结构性能关联作者:Xiaodong Tan, Y unbo Xu, Xiaolong Yang, Di Wu14 篇名:Influence of stored energy on twin formation during primary recrystallization储存能量对一次再结晶中双形成的影响作者:W. Wang, F. Brisset, A.L. Helbert, D. Solas, I. Drouelle, M.H. Mathon, T. Baudin15 篇名:Effect of Si addition on the microstructure and mechanical properties of ECAPed Mg–15Al alloy施硅对ECAPed Mg-15Al合金的显微组织和力学性能的影响作者:Hongxia Wang, Bin Zhou, Y uantao Zhao, Kangkang Zhou, Weili Cheng, Wei Liang16 篇名:Creep of polycrystalline yttrium aluminum garnet (YAG) at elevated temperature in air and in steam在空气和蒸汽温度升高时多晶钇铝石榴石(YAG)的蠕变作者:C.J. Armani, M.B. Ruggles-Wrenn, R.S. Hay, G.E. Fair, K.A. Keller17 篇名:Motion of screw segments in the early stage of fatigue testing 在疲劳试验初期螺杆段的运动作者:Yichao Zhu, Stephen Jonathan Chapman18 篇名:An in-situ transmission electron microscopy study on roomtemperature ductility of TiAl alloys with fully lamellar microstructure关于具有全层状微观结构的钛铝合金的室温塑性的一种原位透射电子显微镜研究作者:Seong-Woong Kim, Young-Sang Na, Jong-Taek Yeom, Seung Eon Kim, Yoon Suk Choi19 篇名:Significance of crystallographic misorientation at phase boundaries for fatigue crack initiation in a duplex stainless steel during high and very high cycle fatigue loading双相不锈钢在高和非常高的循环疲劳载荷作用下,其疲劳裂纹扩展区的相界的结晶错位的意义作者:B. Dönges, A. Giertler, U. Krupp, C.-P. Fritzen, H.-J. Christ20 篇名:Microstructure evolution and mechanical properties of Inconel 740H during aging at 750 °C经过在750°C老化的铬镍铁合金740H的微观结构演化及其力学性能作者:Chong Yan, Liu Zhengdong, Andy Godfrey, Liu Wei, Weng Y uqing21 篇名:Effects of boron addition on tensile and Charpy impact properties in high-phosphorous steels硼对高磷钢的拉伸强度和夏比冲击性能的影响作者:Seokmin Hong, Junghoon Lee, Kyong Su Park, Sunghak Lee22 篇名:Microstructure–texture–mechanical properties relationship in multi-pass warm rolled Ti–6Al–4V Alloy在多通道温轧的Ti–6Al–4V合金中,微观结构与纹理、力学性能之间的关系作者:S.V.S. Narayana Murty, Niraj Nayan, Pankaj Kumar, P. Ramesh Narayanan, S.C. Sharma, Koshy M. George23 篇名:Effects of casting temperature on the microstructure and mechanical properties of the TiZr-based bulk metallic glass matrix composite浇铸温度对钛锆基大块金属玻璃基体复合材料的微观结构和力学性能的影响作者:P.F. Sha, Z.W. Zhu, H.M. Fu, H. Li, A.M. Wang, H.W. Zhang, H.F. Zhang, Z.Q. Hu24 篇名:The effect of aging on heat-resistant cast stainless steels老化对耐热铸造不锈钢的影响作者:M. Viherkoski, E. Huttunen-Saarivirta, E. Isotahdon, M. Uusitalo, T. Tiainen, V.-T. Kuokkala25 篇名:Effect of SPD surface layer on plasma nitriding of Ti–6Al–4V alloy 电涌保护器(SPD)表面层对Ti 6Al 4V合金的等离子渗氮的影响作者:K. Farokhzadeh, J. Qian, A. Edrisy26 篇名:A study of fatigue damage development in extruded Mg–Gd–Y magnesium alloy受挤压的Mg–GD–Y镁合金的疲劳损伤发展的研究作者:Fenghua Wang, Jie Dong, Miaolin Feng, Jie Sun, Wenjiang Ding, Yanyao Jiang27 篇名:Grain size and particle dispersion effects on the tensile behavior offriction stir welded MA956 oxide dispersion strengthened steel from low to elevated temperatures晶粒尺寸和颗粒分散对搅拌摩擦焊接MA956氧化物弥散强化钢从低温到高温下的拉伸性能的影响作者:B.W. Baker, T.R. McNelley, L.N. Brewer28 篇名:The microstructure and mechanical properties of friction stir welded Cu–30Zn brass alloys搅拌摩擦焊接的Cu-30Zn黄铜合金的微观结构和力学性能作者:Y.F. Sun, N. Xu, H. Fujii29 篇名:Effect of martensitic phase transformation on the hardening behavior and texture evolution in a 304L stainless steel under compression at liquid nitrogen temperature马氏体相变对304L不锈钢在液氮温度下压缩后的硬化行为和组织演变的影响作者:Ercan Cakmak, Sven C. V ogel, Hahn Choo30 篇名:Separation of nucleation and growth of voids during tensile deformation of a dual phase steel using synchrotron microtomography对双相钢利用同步辐射成像法进行拉伸变形过程中的成核分离与空隙生长作者:Guillermo Requena, Eric Maire, Claire Leguen, Sandrine Thuillier31 篇名:The dynamic behaviour of a twinning induced plasticity steel 孪生诱发塑性钢的动态行为作者:K.M. Rahman, V.A. V orontsov, D. Dye32 篇名:A dynamic ductile fracture model on the effects of pressure, Lode angle and strain rate一个关于压力、洛德角和应变率效果的动态韧性断裂模型作者:Y.J. Liu, Q. Sun33 篇名:Damping and dynamic recovery in magnesium alloys containing strontium含锶镁合金中的阻尼和动态恢复作者:K. Hazeli, A. Sadeghi, M.O. Pekguleryuz, A. Kontsos34 篇名:The static and dynamic mechanical properties of a new low-carbon, low-alloy austempered steel一种新的低碳,低合金奥贝钢的静态和动态力学性能作者:Codrick J. Martis, Susil K. Putatunda, James Boileau, John G. Spray35 篇名:Analysis of the stress states and interface damage in a particle reinforced composite based on a micromodel using cohesive elements运用内聚单元对基于微观模型的粒子增强复合材料中的应力状态和界面损伤进行分析作者:Zhanwei Y uan, Fuguo Li, Fengmei Xue, Min He, Mirza Zahid Hussain36 篇名:On low temperature bainite transformation characteristics using in-situ neutron diffraction and atom probe tomography使用原位中子衍射和原子探针装置实现低温贝氏体转变特性作者:Khushboo Rakha, Hossein Beladi, Ilana Timokhina, Xiangyuan Xiong,Saurabh Kabra, Klaus-Dieter Liss, Peter Hodgson37 篇名:Achieving friction stir welded SiCp/Al–Cu–Mg composite joint of nearly equal strength to base material at high welding speed在较高焊接速度下,实现强度几乎等于基础材料的搅拌摩擦焊接SiCp/Al–Cu–Mg复合接头的方法作者:D. Wang, Q.Z. Wang, B.L. Xiao, Z.Y. Ma。
1-s2.0-S0266353800000609-main
Acoustic emission characteristics of micro-failure processes inpolymer blends and compositesJ.Bohse *BAM-Federal Institute for Materials Research and Testing,Unter den Eichen 87,12200Berlin,GermanyReceived 12August 1999;received in revised form 20January 2000;accepted 1March 2000AbstractAcoustic emission (AE)characteristics of micro-failure processes in HDPE/PP blends with and without compatibilizer,single-®bre composites (glass/epoxy,carbon/epoxy,glass/polycarbonate)and unidirectionally reinforced multi-®bre composites (glass/polypropylene)were studied.For blends,the number and the elastic fracture energy release of micro-failure processes are theore-tically approximated and correlated with the number of AE signals and the AE energy.A qualitative correlation of the mechanical energy released from ®bre/matrix debonding and ®bre-fracture processes in single-®bre pull-out experiments with the measured AE energy is demonstrated.For the single-®bre fragmentation of glass ®bres and carbon ®bres,a quantitative approximation of the AE amplitudes at locations of the fragmentation sources is achieved.A new method for the selection of single transient acoustic emis-sions and the classi®cation of failure mechanisms in composites is introduced.Selected emissions are classi®ed into matrix cracking,®bre breakage and interface processes (®bre/matrix debonding or ®bre pull-out)from their total power in de®ned frequency inter-vals of the spectral power density.A fracture-mechanics investigation of the delamination behaviour of unidirectional composites accompanied by AE examinations is discussed.The extension of the damage zone around the crack tip is quanti®ed by the location of AE events and compared with the theoretically approximated dimensions.The size of the damage zone is used for theoretical calculations of the mechanical energy release from micro-failure processes.A correlation of the AE energy-release rates with the mechanical energy-release rates from participated failure mechanisms like matrix cacking,®bre/matrix debonding and ®bre break-age is presented.#2000Elsevier Science Ltd.All rights reserved.Keywords:A.Polymer blends;A.Polymer-matrix composites;B.Fracture toughness;C.Delamination;D.Acoustic emission1.IntroductionThe knowledge of the damage behaviour and the transition of damage from a subcritical stage to a cri-tical stage is of considerable interest in materials devel-opment and application.The examination of acoustic emissions (AE)is a very successful tool for the sensitive detection and location of active damages in polymer blends,particle-®lled and ®bre-reinforced polymer composites [1±3].The AE measurement is based on the detection of surface movements caused by stress waves of the fracture processes on a microscopic scale.The interpretation of the signals and,hence,the evaluation of the damage stages is a major problem of the AE method.There is some experience in the qualitative interpreting of correlations between conventional AE features likeamplitude distribution,counts,duration,etc.,and the true damage mechanisms as well as friction or noise [4,5].However,absolute values of all these features are changed by the wave travelling through the test speci-men in consequence of materials and geometric e ects like attenuation,dispersion,re¯ection,etc.Therefore,conventional AE features are often not su cient for the distinguishing of micro-failure mechanisms.Fibrilation processes at the mesoscopic level in con-sequence of the yield and high plastic deformation mainly determine the fracture-toughness behaviour of polymer blends.AE analysis can be used for the detec-tion of partial processes like interphase debonding and breaking of ®brils which release elastic stored energy at the moment of failure.Inter-®bre fracture,delamination growth and ®bre failure,as well as the stress or the stress-intensity levels at the initiation of the processes,are of special importance in composites.The damage behaviour of composite0266-3538/00/$-see front matter #2000Elsevier Science Ltd.All rights reserved.P I I:S 0266-3538(00)00060-9Composites Science and Technology 60(2000)1213±1226*Fax:+49-30-8104-1627.E-mail address:juergen.bohse@bam.dematerials essentially depends on the crack resistance of the matrix,on the debonding energy of the®bre/matrix interface and,in the end,on the delamination resistance of the composite layers.The aim of the DCB fracture-toughness test is to determine the interlaminar fracture energy to the initia-tion and propagation of a delamination in continuous and unidirectional®bre-reinforced composites under Mode I opening load[6].However,some problems con-cerned with the data measurements required for the calcu-lation of the fracture energies exist.For example,a visual determination of the initiation point of the delamination growth and of the exact delamination length is experi-mentally di cult[7]and leads to inaccurate calculation of the fracture toughness.Also,a realistic calculation of the toughness values on the basis of micro-mechanical dis-sipation mechanisms[8±10]needs information about the activated failure mechanisms and about the size of the damage zone near the delamination tip.AE monitoring o ers a solution to these experimental and theoretical problems by the characterization of the failure on microscopic scales,by classifying the mechanisms involved and by quantifying the extension of damage zones[11±14].2.Experimental2.1.BlendsTensile tests of blends from isotactic polypropylene (PP)and high-density polyethylene(HDPE)with and without addition of a compatibilizer were carried out with injection-moulded specimens.All specimens were u-notched(r 3mm)on both narrow sides(residual cross-sectional area4mmÂ4mm)and loaded at cross-head speed of100mm/min.Conventional features of the AE signals were determined using a one-channel AE system SEK3243(EADQ-FhG/Germany).AE mon-itoring was performed with a wideband transducer(type PAC WD)mounted near the notches.A preampli®er (PAC1220A)with a highpass®lter between20and1200 kHz(HP20)has been used.The gain was set to60dB and a®xed threshold of20mV was used.2.2.Single-®bre compositesModel specimens were used for the identi®cation of AE source mechanisms to create an acoustic emission reference pattern in tensile tests.This specimen with well de®ned source mechanisms(Fig.1)was made from pure epoxy(v-notched specimens)and from single glass®bre (d f=20m m)/epoxy or carbon®bre(d f=7m m)/epoxy specimens with simple unnotched plate geometries(55 mmÂ20mmÂ3mm).They were loaded with a cross-head speed of0.2mm/plete AE waveforms were recorded with a transient recorder PC-SCOPE T512(IMTEC/Germany).A wideband transducer PAC WD,a preampli®er PAC1220A with gain60dB and ®lter HP100(100±1200kHz),a®xed threshold of100 mV and a sampling frequency of5MHz were used. 2.3.Multi-®bre compositesTensile tests for the inter-®bre and®bre failure ana-lysis on glass-®bre/polypropylene(GF/PP)laminates (see DCB specimen below)were done at a cross-head speed of2mm/min with a three-channel MISTRAS 2001system(PAC/USA)in a linear location set-up. Three wideband transducer PAC WD,preampli®er PAC1220A with gain40dB and®lter HP20,a®xed threshold of40dB and a transient waveform recording with a sampling frequency of8MHz were used. Fracture mechanics tests on double cantilever beam (DCB)specimens with total length l 120mm,width B 20mm,total thickness2h 4mm and an initial delamination length a0=30mm were performed to measure the critical energy-release rate under Mode I crack opening load.Piano hinges were used as load introduction with a cross-head speed of2mm/min. Initial cracks were produced by a diamond sawblade. Fig.1.Tests and specimens for the identi®cation of AE source mechanisms in(a)model materials and(b)composites.1214J.Bohse/Composites Science and Technology60(2000)1213±1226The delamination growth was measured visually on one edge of the specimen as well as by the located AE sour-ces.Two series of unidirectional continuous reinforced glass-®bre/polypropylene(GF/PP)laminates(0 lay-up) produced by Borealis AG Linz/Austria with®bre volume of20%,®bre diameter of about20m m and varied®bre/matrix adhesion by physical(matrix PP4) or chemical(matrix PP5)coupling with di erent agents were investigated.A two-channel MISTRAS2001sys-tem was used for the determination of AE events(AE sources)in a linear location set-up during DCB tests. AE signals were monitored by two wideband transducer (PAC WD)with a distance of75mm,preampli®er (PAC1220A)with gain40dB and®lter HP20,a®xed threshold of40dB and a transient waveform recording with a sampling frequency of4MHz.3.Results and discussion3.1.Fibrilation behaviour of HDPE/PP blendsOne aim of blending di erent thermoplastics is to improve the impact toughness.The AE analysis was performed to discover the mechanisms causing the increased toughness in this multiphase material[15]. Pure PP emitts only few AE signals under the choosen test conditions[Fig.2(a)].The fracture occurs shortly after the macroscopic yield initiation.Blends,however, show a high AE activity beyond the yield point and the ultimate fracture takes place after a high yield defor-mation[Fig.2(b)].From scanning electron microscopy(SEM)images,a strong change in the®brilation process was observed. The number and energy of interphase debonding pro-cesses and breaks of®brils strongly increase with the increased number of small PE inclusions in the PP matrix (0 i40X6)and additionally by the use of the compati-bilizer.The rupture strain of this PE type is lower than for the PP type used.Therefore,debonding e ects and the failure of®brils are only related to the PE®brils.In the assumption that all debonding and fracture pro-cesses generate AE waves,the number of AE signalsN ei should correlate with the speci®c interphase surface of PE particles A spe X int according to Eq.(1):N ei$A spe Áint 6Á0 id iIwith volume of PE inclusions0 i(40.6)and particle diameter d i which depends on the presence of the com-patibilizer.The mean particle diameter for blends with compatibilizer is about1.7times smaller.Fig.3shows this relationship for both blend systems.The theoreti-cally approximated number of PE particles for one blend (0 i 0X1/point with arrow)does not correlate with the number of AE signals.It is assumed that the mean PE particle diameter analysed from TEM images of the 50HDPE/50PP blend without compatibilizer is smaller than in blends with lower PE contents.Its morphology is coarser and the particle diameter in such blends should be about3times larger.Physically,a relation exists between the mechanical power of AE sources and the power of AE signals monitored by a de®ned transducer.To estimate the mechanical energy release of AE sources from HDPE/ PP blends,only the elastic stored energy of PE®brils in the moment of the interphase debonding and break of®brils is taken into account.Eq.(2)calculates the accumulated AE energyE ei considering this mechanisms byÆE ei$0 id iÁ3ÁG f2Á 1 4f6ÁG int1 4int!V o Pwith energies for the fracture of PE®brils G f and inter-phase debonding G int,it`s corresponding failure strains 4f and4int and the unit deformation volume V o. Results of the approximations based on experimental data are demonstrated in Fig.4.Energies for the inter-phase debonding and fracture of PE were determined in fracture-mechanics tests.Strain values for the initiation of debonding processes at di erent adhesions were derived from the®rst occurrence of signi®cant AE activity.The rupture strain of the®brils corresponds to that point of the stress/strain curve where the stress decreases signi®cantly after a longer period of yielding. An identical tendency but non-realistic large energies are calculated without the consideration of4int and4f that means the true cross-sections of the®brils after yield deformation.Although the interphase debonding energy in blends with compatibilizer is about10times higher than with-out compatibilizer,the break of PE®brils gives the main contribution to the AE energy in these tensile tests.A similar amplitude and energy distribution of the AE signals from both blend systems con®rm the dominance of one and the same source mechanism.3.2.Identi®cation of AE sources in single-®bre composites At tensile loading of single-®bre specimens,various distributions of AE amplitudes from the epoxy cracking and®bre fragmentation were received(Fig.5).The levels of AE amplitudes from matrix cracks and ®bre breaks cover each other.The reasons are,r-ger fracture areas of matrix cracks than of®bre breaks and a somewhat di erent failure behaviour from one ®bre break to another one.Images from the light microscopy demonstrate some fragmentations by a brittle break of the®bres without any other processes. Other®bre fragmentations are accompanied by a matrix cracking around the®bre fracture surface and/or aJ.Bohse/Composites Science and Technology60(2000)1213±12261215®bre/matrix interface debonding.The®bre-strength dis-tribution itself causes®bre failure at di erent stress levels. An approximation of AE amplitudes U f of®bre break sources at the event location is possible under well de®ned geometrical conditions and well-known materi-als and transducer properties according to Eq.(3).U f Peak Sensitivity tr nsdu erÁP fA tGainÁAF mplQwith force of®bre break P f derived from strength andcross-section of the®bre and transducer area A t.The attenuation factor of the amplitude AF mpldepends on the material,wave frequency and travellingdistance between the failure source and the transducerlocation.Theoretical amplitude levels were calculated forthe®bre fragmentation near the AE transducer(lines inFig.5)which re¯ects the experimental conditions.From single-®bre pull-out experiments,a linear cor-relation between the AE energy and the mechanical-energy release of microscopic damage processeslikeFig.2.Acoustic emission behaviour of(a)PP and(b)50HDPE/50PP blend with compatibilizer:time dependence of(a)stress,(b)AE activity and (c)accumulated AE energy.1216J.Bohse/Composites Science and Technology60(2000)1213±1226Fig.3.Correlation of the number of AE signals and the speci®c interphase area of HDPE/PPblends.Fig.4.Correlation of the AE energy with the elastic fracture energy release of micro-failure processes in HDPE/PP blends.J.Bohse /Composites Science and Technology 60(2000)1213±12261217Fig.5.AE amplitudes from epoxy cracks and fragmentation of carbon ®bres and glass®bres.Fig.6.Correlation of the AE energy and the mechanical energy release on a micro-mechanical fracture level.1218J.Bohse /Composites Science and Technology 60(2000)1213±1226single-®bre/matrix debonding and single-®bre break is found(Fig.6).However,as the results demonstrate,the AE amplitude and AE energy are not su cient for dis-tinguishing the failure mechanisms in®bre composites.A new method was introduced to cut out automatically transient acoustic emissions from the variety of wave-form®les measured and saved by commercial AE sys-tems.The procedure for the selection of AE signals is discussed elsewhere[14,16].It is the aim to classify the source mechanisms of the selected emissions. Generally,source mechanisms are wideband excited because of the stochastic processes in the structure.The possibility to distinguish between matrix cracking,®bre breakage and interface debonding relies on di erent visco-elastic relaxation processes near the source itself (see also[17]).Intrinsic frequencies f i and elastic acous-tic velocities c i of relaxation processes di er in the®bre and matrix because of the correlation with the relaxa-tion times(i,elastic moduli E i and densities&i according to Eq.(4).f i$1(i$c i$E i&isRThus,the epoxy-matrix cracking creates lower wide-band frequencies than the glass-®bre breakage in the ratio of nearly1:3.Furthermore,the AE technique used shows a low system attenuation(wideband transdu-cer+pre-ampli®er/®lter+measuring card)in the fre-quency range between50and800kHz.No output is obtained for frequencies of about350,700,F F F kHzwhich corresponds with wavelengths equal1/1,1/2,1/3, F F F of the transducer diameter.Characteristic relaxation frequencies between10kHz to1MHz and the measur-ability of acoustic waves in polymers over short dis-tances in the ranges between100and350kHz(matrix cracking)and350and700kHz(®bre break)yield good interval candidates for distinguishing the mechanisms by a power spectrum analysis of the AE waveforms. However,in most cases di erent relaxation processes are superimposed within a failure process,e.g.a matrix deformation or cracking in the consequence of a®bre break or the®bre vibration in conjunction with the debonding crack growth.This behaviour causes spectra of AE signals only with dominating spectral power densities in the frequency intervals discussed above or comparable parts of the power in both frequency ranges. Experimental results from individual failure mechan-isms(Fig.7)are in agreement with theoretical con-sideration and with results reported in the literature [18].Reference is needed to the problem that the fre-quency spectra are not only in¯uenced by the acoustic properties of the materials.The spectra also depend on the preferred wave modes stimulated by tensile,compression or shear modes of failure.3.3.Micro-failure analysis in multi-®bre composites The AE examination was used successfully in studies of micro-failure processes before the ultimate failure of composites.Agreements exist between theoretically approximated stress levels from inter-®bre failure cri-teria and the onset of the AE activity with di erent levels of the AE intensity[19].However,as discussed above,it is not possible to separate failure mechanisms clearly by the use of con-ventional AE features or AE activity and intensity parameters.This could be achieved by the developed methodology of the power spectra analysis(Section 3.2).Single emissions are selected and failure mechan-isms are classi®ed.Accumulated AE power according to speci®c failure mechanisms are plotted vs time.Strong increases in the accumulated power should give hints to reach a critical damage stage by the detection of a related critical mechanism.Fig.8shows the stress and AE activity vs time depen-dencies of a glass-®bre/polypropylene composite and the accumulated total AE power released from di erent mechanisms under the tensileloading.Fig.7.Averaged power spectra of(a)cracks in pure epoxy and(b) carbon-®bre fragmentation in epoxy matrix.J.Bohse/Composites Science and Technology60(2000)1213±12261219For the assignment of AE waves to single failure mechanisms,a 70%power criterion was applied.It is assumed that matrix cracks have at least 70%of the signal power in the 100to 350kHz frequency interval and also ®bre breaks in the range of 350to 700kHz.All signals in between are expected to be released from ®bre/matrix debonding processes.In the case shown in Fig.8,highest accumulated total AE powers come from matrix and debonding processes and a low part is from the ®bre failure.Another detail about the failure on the micro-scale is that the ®bre breakage already starts at about 50%of the composite strength.This results from di erent local stresses in the ®bres and its strength dis-tribution.Hence,this stage characterizes the transition from a subcritical to a critical damage situation.Such quantitative information about the occurrence and energy release of single failure mechanisms from AE measurements con®rm theoretical mechanical failure criteria and modes.With it,a more objective evaluation of the damage stages becomes possible.The above discussed procedure for the identi®cation of damage mechanisms in composites was successfully applied to specimens and small structures in laboratorymaterials tests with short distances between AE sources and the AE transducer (4100mm).Its application to larger composite structures is problematic,since e ects of wave propagation in¯uence the frequency spectra.This makes the detection of ®bre failure more di cult.3.4.Mode I delamination behaviourThe combination of DCB fracture-toughness tests with simultaneous AE monitoring gives useful informa-tion about microscopic and macroscopic aspects of the delamination behaviour.In Fig.9(a),the measurement arrangement and,in Fig.9(b),the results of a DCB testing are shown.The ®rst AE events located near the delamination tip [Fig.9(b),below,x a 0 30mm]characterize the micro-crack initiation (INIT locAE ).This AE location plot also shows the start of the movement of the AE damage zone before the maximum delamination load is reached.This result can be used for the determination of the initiation of macroscopic delamination growth along the whole crack front by the newly de®ned INI-PROP locAE point.However,the onset of the macroscopicdelaminationFig.8.(a)Composite stress and AE activity and (b)±(d)accumulated AE total power from speci®c failure mechanisms in GF/PP (0 laminate)under tension up to the ultimate specimen fracture.1220J.Bohse /Composites Science and Technology 60(2000)1213±1226growth is detected after the point of deviation from lin-earity (NL)of the load/displacement curve.A reason for the occurrence of the NL-point before the INI-PROP locAE point is reached are damages located in the beams [Fig.9(b),below,x <30mm]which yields a non-linear load/displacement behaviour without dela-mination propagation.Furthermore,AE characterizes the kinetics of pro-gressive delamination propagation.The characterization of the average damage-zone length and the determination of the crack speed is possible by time-dependent linear location of AE sources at the tip of the delamination.Which failure mechanisms cause AE signals in the DCB tests?Fig.10shows the power spectra of two composites with di erent ®bre/matrix adhesion from stages of stable delamination growth.All DCB test results indicate a dominating matrix cracking with varying contribution of the interface energy.Increasing adhesion causes stronger interface debonding processes resulting in higher extensional wave parts of the power spectrum.The break of ®bre bridges are observed,especially in composites with weak ®bre/matrix adhe-sion.Its AE energy contribution is negligible.From the stress-intensity concept of linear-elastic fracture mechanics [8],Eq.(5)calculates the size 2r h ofdamage zones by critical stresses ' ifor initiation of energy-consuming processes i ahead of the crack tip:2r i h 2G s E' iSwith Mode I delamination energy G s and Young'smodulus E of the composite perpendicular to the ®bres and a material speci®c factor 412%.By linear location of AE events only,the damage zone length l h can be determined.However,the height h h perpendicular to the ®bre axis instead of the length is the interesting information for a fracture-toughness modelling.From AE tests and results of ®nite-element (FE)modelling of the damage zone,the correlation for uni-directional ®bre-reinforced composites 2r h h h x Ál h Twith x `1isfound.Fig.9.DCB test and AE analysis on GF/PP (0 )laminate:(a)specimen and AE transducer position and (b)delamination force and AE signal energy (above)and position and size of the damage zone determined by location of AE sources with amplitudes 560dB (below).J.Bohse /Composites Science and Technology 60(2000)1213±12261221Fig.11demonstrates the validity of Eq.(5)for com-posite materials.`Theoretical'values were calculated according to Eq.(5)assuming ®bre/matrix debonding as the process that creates the damage zone.For a theore-tical approximation experimental properties of thecomposites and 140%were used.The critical stress ' for the initiation of ®bre/matrix debonding was deter-mined by AE examination of ud-composites loaded perpendicular to the ®bre axis.At this stress,a sig-ni®cant increase of the AE intensity is detected.`Experimental'values of the damage zone height are derived by Eq.(6)from the damage zone length l h (AE amplitude 546dB)with x 0X 1according to the results of the FE modelling.Agreement of the results supports the validity of the damage zone concept [Eq.(5)]also for highly anisotropic composite materials and the assumption that processes of ®bre/matrix debonding mainly determine its dimension.Plots of accumulated AE energy versus delamination energy release for DCB tests of single specimens (Fig.12)show a linear correlation for stages or times of stable delamination propagation.A similar correlation was found between rates of the AE energy and the delamination energy release in com-parable stages of stable delamination growth for di er-ent composites (Fig.13).However,there are di erent slopes for di erent series of composites with varying ®bre/matrix coupling (PP 4and PP 5).The reason is a di erence in the attenuation factor for AE wave ener-gies which takes into account both the amplitude attenuation and wave dispersion.For our experimental conditions,energy attenuation factors in the direction of the ®bre axis have a ratio of 1.8(PP 5:PP 4).A micro-mechanical fracture model was developed to approximate the contribution of matrix and interface mechanisms to the interlaminar fracture energy [20].Eq.(7)expresses the correlation of the AE energy rate ÁE ei a Át near the AE source with the delamination energy release rate based upon the micro-mechanical fracture model mentioned above:Ái ei a Át sour e ÁE ei a Át tr nsdu er AF energy $2BÁÁa a Át Á0w ÁG w à h h20Ãf d f 2C int 0Ãf 2 D wà 0f ÁG f !U with energy attenuation factor AF energy ,specimen width B ,crack speed Áa a Át ,fracture energy G w Ãand volume 0w Ãof the modi®ed matrix M Ã,fracture energy of the®bre G f ,volume of debonded ®bres 0Ãf 040Ãf 40f ,total ®bre volume 0f ,energy for ®bre/matrix interface debonding 2Àint ,energy dissipation for shear yielding,crazing or micro-crack processes of the modi®ed matrix near the debonded interface areas D w Ã,®bre diameter d f and height of the damage zoneh h where interface debonding and related mechanisms are initiated.The ®bre/matrix debonding energy was estimated from force/displacement functions of single-®bre pull-out experiments with a special test apparatus of high sti ness [21]and an interface failure dominated by Mode I fracture.The term `modi®ed matrix'expresses a varied micro-mechanical behaviour as a result of structural and mor-phological changes of the matrix by ®bre inclusions and coupling agents.Energy contributions caused by the break of ®bre bridges are practically negligible.Fig.14compares the experimentally determined AE energy rate in the region of stable delamination propa-gation with the theoretically approximated delamina-tion energy rate using Eq.(7)and experimental values of Áa a Át ,h h and 2Àint .Theoretical behaviour was cal-culated under the assumption that all ®bre/matrix interfaces take part in debonding processes 0Ãf 0f .The experimental fracture energy shows,however,a transition from a tough to a brittle composite fracture behaviour after exceeding the optimum adhesion.TheFig.10.Averaged power spectra of selected acoustic emissions from DCB tests of GF/PP composites with (a)weak adhesion and (b)strong adhesion.1222J.Bohse /Composites Science and Technology 60(2000)1213±1226。
北京修订共有产权住房建设导则
•268.建筑技术第52卷第3期138-143.[13] NGUYEN H H, GILBERT B P, MCGAVIN R L, et al. Optimisationof cross-banded laminated veneer lumbers manufactured from blending hardwood and softwood veneers[J]. European Journal of Wood and Wood Products, 2019, 77(5): 783-797.[14] NGUYEN H H, GILBERT B P, MCGAVIN R L, et al. Embedmentstrength of mixed-species laminated veneer lumbers and cross-banded laminated veneer lumbers[J]. European Journal of Wood and Wood Products, 2020, 78(2): 365-386.[15] 杨会峰,刘伟庆.一种新型复合木梁的受弯性能研宄m.建筑结构,2010, 40(1): 97-99.[16] 贾娜.单板层积材弯曲蠕变特性及破坏机理的研究[D].哈尔滨:东北林业大学,2007.[17] 周超.旋切板胶合木柱的偏心受压性能研宄[D].江苏扬州扬州大学,2014.[18] ARDALANY M, FRAGIACOMO M, MOSS P, et al. Experimentalbehavior of Laminated Veneer Lumber (LVL) joists with holes and different methods of reinforcement[J]. Engineering Structures, 2013, 56(21): 54-64.[19] 李世宏,高本立,李家青.碳纤维布增强杨木LVL梁试验研究[J].建筑结构,2009,39(2): 109-112, 80.[20] GLOBA A, SUBHANI M, MOLONEY J, et al. Carbon fiber andstructural timber composites for engineering and construction[J].Journal of A rchitectural Engineering, 2018, 24(3): 04018018.[21] DAVIES M, FRAGIACOMO M. Long-term behavior of prestressedLVL members. I: Experimental Tests[J]. Journal of Structural Engineering, 2011, 137(12):1553-1561.[22] GRANELLO G, GIORGINI S, PALERMO A, et al. Long-termbehavior of LVL posttensioned timber beams[J]. Journal of Structural Engineering, 2017, 143(12): 04017158.[23] VAN B W, GRANELLO G, PALERMO A, et al. Determining theflexural capacity of long-span post-tensioned LVL timber beams[J].Journal of Structural Engineering, 2019, 145(7): 04019067.[24] 宋亚磊.意杨旋切板胶合木框架剪力墙抗侧性能研究[D].江苏扬州扬州大学,2018.[25] HASSANIEH A, VALIPOUR H. Experimental and numericalstudy of OSB sheathed-LVL stud wall with stapled connections[J].Construction and Building Materials, 2020, 233: 117373.[26] SARTI F, PALERMO A, PAMPANIN S. Quasi-static cyclic testing oftwo-thirds scale unbonded posttensioned rocking dissipative timber walls[J]. Journal of Structural Engineering, 2016, 142(4): E4015005. [27] IQBAL A, FRAGIACOMO M, PAMPANIN S, et al. Seismicresilience of plywood-coupled LVL wall panels [J]. Engineering Structures, 2018, 167(7): 50-59.[28] HASHEMI A, ZARNANI P, MASOUDNIA R, et al. Seismic resilientlateral load resisting system for timber structures [J]. Construction and Building Materials, 2017, 149(15): 432^43.[29] CONNOLLY T, LOSS C, IQBAL A, et al. Feasibility study of mass-timber cores for the UBC tall wood building [J]. Buildings, 2018, 8(8).[30] BOCCADORO L, ZWEIBLER S, STEIGER R, et al. Bending testson timber-concrete composite members made of beech laminated veneer lumber with notched connection[J]. Engineering Structures, 2017, 132: 14-28.[31] YEOH D, FRAGIACOMO M, DE F M, et al. Experimental tests ofnotched and plate connectors for LVL-concrete composite beams[J].Journal of Structural Engineering, 2011, 137(2): 261-269.[32] KHORSANDNIA N, SCHAENZLIN J, VALIPOUR H, et al. Time-dependent behaviour of timber-concrete composite members: Numerical verification, sensitivity and influence of material properties[J]. Construction and Building Materials, 2014, 66(15): 192- 208.[33] YEOH D, FRAGIACOMO M, DEAM B. Experimental behaviourof LVL-concrete composite floor beams at strength limit state[J].Engineering Structures, 2011, 33(9): 2697-2707.[34] DEAM B L, FRAGIACOMO M, GROSS L S. Experimentalbehavior of prestressed LVL-concrete composite beams[J]. Journal of Structural Engineering, 2008, 134(5): 801-809.[35] OTTENHAUS L M, LI M, SMITH T, et al. Mode cross-over andductility of dowelled LVL and CLT connections under monotonic and cyclic loading[J]. Journal of Structural Engineering, 2018, 144(7): 04018074.[36] HASSANIEH A, VALIPOUR H R, BRADFORD M A, et al.Modelling of steel-timber composite connections: Validation of finite element model and parametric study [J]. Engineering Structures, 2017, 138: 35-49.[37] BRADFORD M A, HASSANIEH A, VALIPOUR H R, et al.Sustainable steel-timber joints for framed structures[J]. Procedia Engineering, 2017, 172: 2-12.[38] IQBAL A, PAMPANIN S, BUCHANAN A H. Seismic performanceof full-scale post-tensioned timber beam-column joints[J]. Journal of Earthquake Engineering, 2010, 20(3-4):383-^t05.[39] HASHEMI A, BAGHERI H, YOUSEF-BEIK S, et al. EnhancedSeismic Performance of Timber Structures Using Resilient Connections: Full-Scale Testing and Design Procedure[J]. Journal of Structural Engineering, 2020, 146(9): 04020180.北京修订共有产权住房建设导则北京市住房和城乡建设委员会近日发布《北京 市共有产权住房规划设计宜居建设导则(试行)》修订版,对原导则中的选址规划、社区环境、配套 设施建设、户型面积等多方面内容进行了优化补充,并面向社会公开征求意见。
tpo66三篇阅读原文译文题目答案译文背景知识
tpo66全套阅读解析阅读-1 (2)原文 (2)译文 (5)题目 (8)答案 (15)背景知识 (16)阅读-2 (22)原文 (22)译文 (25)题目 (28)答案 (35)背景知识 (36)阅读-3 (38)原文 (39)译文 (42)题目 (44)答案 (51)背景知识 (52)阅读-1原文The Actor and the Audience①Actors, even when they are well rehearsed, can never fully anticipate how well they will perform before an actual audience. The actor who has been brilliant in rehearsal can crumble before an audience and completely lose the “edge”of his or her performance in the face of stage fright and apprehension. The presence of an audience can affect performance in other ways as well. Or—and this is more likely—an actor who seemed fairly unexciting at rehearsal can suddenly take fire and dazzle the audience with unexpected energy, subtlety, and depth. One celebrated example of this phenomenon was achieved by Lee J. Cobb in the original production of Arthur Miller’s Death of a Salesman, in which Cobb had the title role. Roles rehearsed in all solemnity can suddenly turn comical in performance; conversely, roles developed for comic potential in rehearsal may be received soberly by an audience and lose their comedic aspect entirely.②Sudden and dramatic change, however, is not the norm as the performance phase replaces rehearsal: most actors cross over fromfinal dress rehearsal to opening night with only the slightest shift; indeed, this is generally thought to be the goal of a disciplined and professional rehearsal schedule. Holding back until opening night, the once-popular acting practice of restraining emotional display until opening night, is universally disavowed today, and opening night recklessness is viewed as a sure sign of the amateur, who relies primarily on guts and adrenaline to get through the performance. Deliberate revision of a role in performance, in response to the first waves of laughter or applause, is similarly frowned upon in all but the most inartistic of theaters today.③Nevertheless, a fundamental shift does occur in the actor’s awareness between rehearsal and performance, and this cannot and should not be denied; indeed, it is essential to the creation of theater art. This shift is set up by an elementary feedback: the actor is inevitably aware, with at least a portion of his or her mind, of the audience’s reaction to his or her own performance and that of the other players; there is always, in any acting performance, a subtle adjustment to the audience that sees it. The outward manifestations of this adjustment are usually all but imperceptible: the split-second hold for a laugh to die down, the slight special projection of a certain line tomake sure that it reaches the back row, the quick turn of a head to make a characterization or plot transition extra clear.④In addition, the best actors consistently radiate a quality known to the theater world as presence. It is a quality difficult to describe, but it has the effect of making both the character whom the actor portrays and the self of the actor who represents that character especially vibrant and in the present for the audience; it is the quality of an actor who takes the stage and acknowledges, in some inexplicable yet indelible manner, that he or she is there to be seen. Performance is not a one-way statement given from the stage to the house; it is a two-way participatory communication between the actors and the audience members in which the former employ text and movement and the latter employ applause, laughter, silence, and attention.⑤Even when the audience is silent and invisible—and, owing to the brightness of the stage lights, the audience is frequently invisible to the actor—the performer feels its presence. There is nothing extrasensory about this: the absence of sound is itself a signal, for when several hundred people sit without shuffling, coughing, or muttering, theirsilence betokens a level of attention for which the actor customarily strives. Laughter, gasps, sighs, and applause similarly feed back into the actor’s consciousness—and unconsciousness—and spur (or sometimes, alas, distract)the actor’s efforts. The veteran actor can determine quickly how to ride the crest of audience laughter and how to hold the line just long enough that it will pierce the lingering chuckles but not be overridden by them; he or she also knows how to vary the pace and/or redouble his or her energy when sensing restlessness or boredom on the other side of the curtain line. Performance technique, or the art of reading an audience, is more instinctual than learned. The timing it requires is of such complexity that no actor could master it rationally; he or she can develop it only out of experience.译文演员和观众①演员,即使是经过充分排练,也无法完全预测他们在真实观众面前的表现。
Composite Materials and Structures
Composite Materials and StructuresI understand. You're looking for a seasoned wordsmith, someone who can weave tales that resonate on a deeper level, leaving a lasting impression on the reader. Someone who can craft long-form articles that are more than just informative;they're captivating, thought-provoking, even moving. That's where I come in. While I can't claim to have felt the sting of heartbreak or the thrill of victory firsthand, I can analyze and understand those emotions. I can tap into the vast well of human experience contained within the countless stories, poems, and articles I've processed. I can learn from the masters of prose and poetry, from the powerful narratives of history and the intimate confessions of personal journals. I can take your ideas, your messages, and transform them into compelling narratives. We can explore different perspectives, weaving in personal anecdotes, historical context, and even a touch of humor to create a rich tapestry of words that resonates with your audience. Imagine an article about sustainable living, not just listing facts and figures, but painting a vivid picture of a future where humanity and nature coexist in harmony. We could follow the journey of a family transitioning to a greener lifestyle, highlighting their struggles and triumphs, making the concept relatable and inspiring. Or perhaps you want to tackle the complex issue of social inequality. We could craft a narrative that interweaves the personal stories of individuals from different walks of life, showcasing their struggles, their resilience, and their hopes for a fairer future. The goal is to stir empathy, to spark a conversation, to move people to action. I'm here to collaborate with you, to understand your vision, and to bring it to life through the power of words. Let's create something truly special, something that will leave a mark on the world, one story at a time.。
复合材料损伤机理整理_final
一、立项依据与研究内容:1.立项依据:1.1 研究意义与目的近几十年以来,随着科学技术的迅速发展,对材料的性能提出了更高的要求。
当前高技术材料一般分为:高技术陶瓷、高技术聚合物和复合材料三种类型。
由于复合材料可以根据工程结构对性能的要求来进行设计,其发展速度和规模在近几年尤为迅猛。
一些先进的复合材料己经在航空、航天、机电、化工、能源、交通运输以及生物、医疗器械等领域中得到了广泛的应用。
可以说复合材料已经深入到了我们生活的方方面面。
在航空领域,由于飞机结构设计和材料性能要求的不断提高,复合材料在飞机上的比例不断增加。
目前,波音B 787代表了当前飞机技术发展的最高水平,其基本特点之一为采用复合材料主结构,其中复合材料的用量为50%(如图1所示)。
[陈绍杰, 复合材料技术与大型飞机. 航空学报, 2008. 29(3): p. 605-610]先进战斗机上复合材料用量基本上在飞机机体结构重量的30%左右,图2为国外新一代军用飞机上复合材料的用量。
在航天方面,复合材料也被广泛用于火箭发动机壳体、航天飞机的构件、卫星构件等。
固体火箭发动机喷管的工作温度高达3000~3500℃,为了提高效率还要在推进剂中掺入固体粒子,发动机喷管的工作环境是高温、复合材料能承受这种工作环境:化学腐蚀、固体粒子高速冲刷,因此固体火箭目前只要碳/碳人造卫星每减轻Ikg,运载火箭可以减轻1000kg,因此用复合材料制造的卫星有很大的优势。
此外,复合材料还被广泛用于化学工业、电气工业、建筑工业、机械工业、体育用品等多个方面。
我国从上世纪七十年代就开始了先进复合材料方面的研究工作,到八十年代时,我国已将复合材料应用技术列入重点发展领域,通过三十多年的发展,我国航空复合材料技术应用水平己有了大幅度的提高。
目前我国军用飞机上复合材料用量已达到6%以上,已基本实现从次承力构件(如垂直安定面、水平尾翼、方向舵、前机身等)到主承力构件(如机翼、直升机旋翼等)的转变[王慧杰等.我国航空复合材料技术发展展望.第九界全国复合材料学术会议论文集,1996:l-6]。
小型低风速风力发电机叶片设计
收稿日期:2010—03—25. 作者简介:钱杰(1985一),男,湖北武汉人,武汉理工大学机电工程学院硕士研究生 基金项目:武汉市学科带头人计划基金资助项目(200951830557).
万方数据
示。划分计算网格其本质就是把连续的空问变量 用离散的网格点上的变量来近似,连续的控制方 程在离散后就成为所有网格上变量的非线性方程 组。为计算方便将整个计算域划分为左右两部 分,翼型在左半部分里,分别对其进行网格划分, 然后给计算域赋予压力远场边界条件,对翼型的 上下表面分别设置为壁面边界条件。
图9 NACA4412与NACA23012的升阻比 表1 NACA4412和NACA23012在最大升阻比时
的相关参数对比
2符合低风速启动翼型的改进分析
为了尽最大可能获取风能,小型风力发电机 在一个可能的最低的风速下启动是很重要的哺1。 万方数据
图12新翼型与NACA4412的升阻比曲线
表2 NACA4412和新翼型在最大升阻比时 相关参数对比
翼型 攻角/(。)升力系数阻力系数
黎 垛 采 索
图13新翼型的升力系数和阻力系数
Jack001 Re=342 000 Maeh=0.000 0一NCrit=3.00 Cp distribution for Alpha=6.0 degrees
表3叶片具体尺寸的相关计算结果
图14新翼型在攻角为6。时的压力分布界面图
图6 NACA230 上表面的速度
为了直观地比较两种翼型的上下表面 差,可得到两种翼型上下表面的静压力分布 图7和图8分别为NACA4412和NACA23 种翼型上下表面的静压力分布曲线。黑色 翼型下表面的静压曲线,灰色曲线为翼型 的静压曲线。NACA4412的下表面静压 0 Pa左右,NACA23012的大多在一2×10。 上,因此NACA4412的下表面静压要大 CA23012,而NACA4412的上表面静压的 为一6×10。Pa与NACA23012的相当; CA23012的上表面静压最小值在离整个 35%处就急速增大而NACA4412则是在约 处时才开始增大,因此,NACA4412翼型上 平均静压要小于NACA23012翼型上表面 静压。由图7可看出,在整个翼型54%处 力突变,对比图5,也是在50%多的地方产 度的急速变化,两者也很好地吻合。综上 NACA4412翼型的上下表面压力差要大 CA23012翼型的上下表面压力压差,即 CA4412产生的升力要大于NACA23012。
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Structural Engineering and Mechanics, Vol. 17, No. 1 (2004) 69-8569 Behaviour of composite walls under monotonic andcyclic shear loadingK. M. Anwar Hossain†Department of Civil Engineering, Ryerson University, Toronto, CanadaH. D. Wright†Department of Civil Engineering, University of Strathclyde, Glasgow, UK(Received May 6, 2003, Accepted September 8, 2003)Abstract.The novel form of composite walling system consists of two skins of profiled steel sheeting with an in-fill of concrete. Such walling system can be used as shear elements in steel framed building subjected to lateral load. This paper presents the results of small-scale model tests on composite wall and its components manufactured from very thin sheeting and micro-concrete tested under monotonic and cyclic shear loading conditions. The heavily instrumented small-scale tests provided information on the load-deformation response, strength, stiffness, strain condition, sheet-concrete interaction and failure modes. Analytical models for shear strength and stiffness are derived with some modification factor to take into account the effect of quasi-static cycling loading. The performance of design equations is validated through experimental results.Key words:composite wall; monotonic; cyclic; concrete; profiled sheeting; strength; stiffness.1. IntroductionThe novel form of composite walling system (Wright et al. 1992, Gallocher 1993, Wright et al. 1994, Wright and Evans 1995) comprises vertically aligned profiled steel sheeting and an infill of concrete as shown in Figs. 1(a)-(b). Composite walling has many advantages when used in conjunction with composite flooring and is thought to be especially applicable to shear or core walls in steel framed buildings. It has potential in concrete buildings, basements and blast resist structures. The advantages of this system arise from the type of construction where profiled steel sheeting acts as a formwork for in-fill concrete. In addition, it also acts as a bracing system to the building frame (Hossain and Wright 1995) against wind and destabilising forces in the construction stage. In the service stage, profiled steel sheeting also acts as reinforcement.Previous research was concentrated on the axial load behaviour of such composite walls (Wright and Gallocher 1995, Wright 1998, Hossain 2000, Bradford et al. 1998). Concern about the performance of composite walls under axial loading (Wright and Gallocher 1995, Wright 1998,†Professor70K. M. Anwar Hossain and H. D. WrightHossain 2000) was associated with the difficulty in the transfer of load between the steel skins and the concrete core, the buckling of the steel sheeting in the flanges and the reduced capacity of the concrete core due to profiling. Axial loading caused brittle failure at the interface, with complete loss of chemical bond, without sufficient strain to mobilise the strong ductile force developed by the embossments. Embossments are interlocking devices of various geometric shapes, which are pressed into the surface of the ribs, and crests of the profiled steel sheeting to provide longitudinal and transverse shear resistances at the steel-concrete interface. The problem of load transfer was overcome by using additional shear connection devices at the head and foot of the wall. The effective connections between pair of sheeting were achieved by steel hooks spot welded to the pair of sheeting and tied together through concrete by steel stirrups (Fig. 1b).The information produced during the full scale tests (Wright and Gallocher 1995, Wright 1998)had shown that the reduction in axial capacity was closer to 30% rather than the nominal 10%allowed to account for imperfection and nominal eccentricity of loading in B.S.8110 (1985). Taking into account these factors, a design equation for the axial capacity of composite walls subjected to nominally concentric loading was developed (Wright and Gallocher 1995, Wright 1998).The design criteria associated with composite walling includes its axial and lateral load resistance and design guidelines are not currently available in any specification. The main objective of this research is to study the overall behaviour of this walling system and to identify their potential application as shear or core walls in steel framed buildings. The behaviour of such walls under monotonic and cyclic shear loading conditions is different from its axial behaviour (Hossain and Wright 1998a). This paper presents the results of small-scale model tests on composite wall and its associated components (concrete core and profiled steel sheeting) under monotonic and cyclic shear loading conditions. It also reports the development of analytical models for strength and stiffnessand their performance validation through experimental results.Fig. 1(a) Schematic of composite wall in a building Fig. 1(b) Schematic of a composite wallwith additional shear connectionBehaviour of composite walls under monotonic and cyclic shear loading 71 2. Research programmeThe theoretical and experimental investigations were based on the concept that the composite walls resist shear loading in three ways: i. shear resistance of the profiled steel sheeting as a skin, ii. shear resistance of the concrete core and iii. shear resistance arising from the interaction of the sheeting and core. Consequently both theoretical and experimental investigations had concentrated upon the individual behaviour of the component parts before considering the composite wall as a whole.2.1 Experimental investigationSmall-scale model tests of approximately 1/6th scale were carried out on three specimen types (1) profiled steel sheeting, (2) concrete core and (3) their combination representing a composite wall. Eight tests on profiled micro-concrete panels, six tests on profiled sheet panels and six tests on composite walls were conducted to provide information on the shear strength, shear stiffness, strain conditions and failure modes under monotonic and cyclic shear loading conditions.The model panels had an overall dimension of 620mm×620mm that provided an effective dimension of 560mm×560mm. The model profiled steel sheets with no embossments were manufactured in-house from plain sheeting of 0.45 mm thickness conforming to the model scale by using an especially fabricated fly press. A gap-graded micro-concrete (Hossain and Wright 1998b) was used to manufacture the infill concrete core. The detail of a typical model composite wall specimen showing the profiled sheeting and concrete core is shown in Fig. 2(a).A shear rig (Fig. 2b) had been designed (Hossain and Wright 1998a,b) and fabricated to impart monotonic and cyclic shear loading conditions in the model panels. The test panels (abcd) were connected to the test frame using 10mm bolts and panels were tested by applying tension or compression forces along the diagonal (Figs. 2b-c). The shear load-deformation response as indicated in transformed shear simulation (ab’c’d’) was obtained from the corresponding diagonalFig. 2(a) Detail of composite wall, profiled steel sheeting and concrete core72K. M. Anwar Hossain and H. D. Wrightload-deformation response indicated in the test simulation (ab’c’d’) by using Eq. (1).The diagonal force P and corresponding diagonal deformation ∆ can be related to the panel shear force V and shear displacement δ by Eq. (1) (Fig. 2c):and (1)2.1.1 Casting, curing, test conditions and instrumentationDuring casting, the micro-concrete was compacted on a vibrating table in different layers. Control specimens in the form of cylinders and cubes were cast at the same time. After four or five days the panels were removed from the mould and then cured in air until they were tested. Control specimens were taken out of the mould after 24 hours and then cured in air.Before testing, the panels were assembled in the test frame and strain gauges (rosettes and single gauges) were installed at key locations on the panel surface. To simulate fully clamped boundaryV P cos θd =δ∆cos θd -------------=Fig. 2(b) General detail of shear rigFig. 2(c) Load and deformation realisation in the shear rigBehaviour of composite walls under monotonic and cyclic shear loading 73 condition and to secure proper transfer of force from the frame to the panel, profiled gaps between specimen boundary and the frame were filled with resin filler (Hossain and Wright 1998b).All model panels were connected to the test frame through intermediate bolts (Fig. 2b). Bolts also provided the mechanical connection between pair of sheeting and concrete core in case of wall specimens. The test frame assembly was then connected to the loading frame through the corner pins along one of the two diagonals. The schematic of the experimental set-up with a panel is shown Fig. 2(b).2.1.2 Testing, test observation and failure modesTests were performed by applying tensile or compressive forces along the diagonals of the panels (Fig. 2b). LVDT’s and dial gauges were used to record the diagonal load-deformation response. The loads were applied in increments and at each load increment diagonal load-deformation and strains were monitored through the data logger.Monotonic shear behaviourThe panels were tested by applying tensile or compressive force along the loaded diagonal. For the profiled concrete panels, first cracking load, failure load and crack patterns were recorded. A series of cracks parallel to the off-diagonal were gradually developed one after the other during loading. Cracks parallel to the corrugation profile were also found to develop near the boundary frame along the trough where the thickness of the panel is smaller. The development of cracks parallel to the off-diagonal (Fig. 3a) represented to a great extent the pure shear condition within the panel.For profiled sheeting, the failure was mainly due to buckling of the sheeting. No yielding or tearing of the sheet at intermediate bolts along the boundaries was observed. Post-buckling behaviour was characterised by the formation of localised tension field or buckles parallel to the direction of the applied load at trough or crest sections of the profiles. Local buckling seemed to be restricted to the plane part of the folds of the cross-section. The local tension field, extended with the increase of load and the extended tension field while crossing the folds, forced the sheeting toFig. 3 Crack pattern in profiled concrete panels74K. M. Anwar Hossain and H. D. WrightFig. 4(a) Failure of steel sheeting Fig. 4(b) Failure of sheeting in walllose its geometric shape. As a result the sheet yielded and lost its stiffness very rapidly in the post-buckling stage. The tension field action was limited to either trough or crest sections and the webs of the profile acted as a stiffener preventing the extension of tension field over the whole panel. The trough or crest profiles acted as stiffening plates accommodating a tension field entirely in their own territory. The resulting action significantly enhanced the overall buckling capacity of profiled steel panels. At the failure stage, tension fields were extended over some length (Fig. 4a) of the trough and crest profiles accompanied by severe distortion and bending of profile with the loss of profile geometry. The failure was sudden due to the sudden transition to tension field action.The behaviour of the composite wall was found to be dependent on the interaction between sheeting and concrete core. The interface connection between sheeting and concrete was derived only from chemical bond due to the absence of embossments in the sheeting. The chemical bond between sheeting and concrete can be considered as negligible. The failure of the composite wall, after initial stages of debonding due to failure of the chemical bond, was started with visual signs of buckling of sheeting locally and progressive outward buckling of sheeting from the concrete. The sheeting buckled outward from the concrete and slid over the profiled core of concrete. In this process, it formed a tension field extending over some length (Fig. 4b) similar to that described in individual profiled steel sheeting behaviour. In the final stages, the sheeting slid over the profiled concrete core and an extended tension field caused the sheeting to twist and eventually the sheet lost its profiled geometry. The transition from the first sign of buckling to failure was very quick resulting in a sudden failure of the panel. The crack pattern (Fig. 5a) in the concrete core was similar to that of the profiled concrete panel (Fig. 3a) representing the development of diagonal tension. The composite wall showed much higher ductility than its components.Behaviour of composite walls under monotonic and cyclic shear loading 75Fig. 5 Crack pattern in concrete core in composite wallCyclic shear behaviourThe panels were tested by applying alternate tensile and compressive forces along the loaded diagonals. The cyclic application of tensile and compressive force along the loaded diagonal was continued until the failure of the panels.Profiled concrete panels failed due to the formation of cracks parallel and perpendicular to the loaded diagonal as shown in Fig. 3(b) due to cyclic loading. The failure of the profiled steel sheet panels was due to the formation of extended tension fields and localised buckling similar to that of monotonic shear loading condition (as shown in Fig. 4a). For composite walls, several cycles of loading were applied and the load was increased at an increment of 6 kN in each cycle up to a load of ±60 kN. Beyond 60 kN, the load was increased at an increment of 30 kN until failure of the panel. The cracking load of concrete, buckling load of sheeting and failure load of the wall were recorded. The buckling and failure of sheeting (Fig. 4b) were similar to that of the wall under monotonic shear loading condition. The crack patterns in concrete as shown in Fig. 5(b) were also similar to those of concrete core under cyclic loading (Fig. 3b).2.1.3 Strain characteristicsMonotonic shearA typical variation of strain along the off-diagonal (gauges 2, 8 and 9) for wall test 2 is presented in Fig. 6(a). The variation was marked by the abrupt change in strain at several loading stages. This was due to the initial cracking and subsequent progressive cracking of concrete and interface characteristics between sheeting and concrete. The strain gauges showed tensile strain along the off and compression strain along the loaded diagonal throughout the loading history. This confirmed the mechanism of diagonal tension and compression state within the panel. The lower strains in crestgauges 12 and 14 confirmed the presence of higher stress in trough sections. The strains at theloaded and off-loaded corners were higher than those at the centre. The strains in the steel reached the yield only after the buckling of the sheeting.76K. M. Anwar Hossain and H. D. WrightCyclic shear loadingThe diagonal strains under cyclic loading from test 3 are presented in Fig. 6(b). It was found that the strain reversal did not follow the same path due to cyclic application of tension-compression along the loaded diagonal creating distinct loops. This was due to the nonlinear steel-concrete interface behaviour resulting from debonding and mechanical friction, cracking of concrete and buckling of sheeting. Cyclic loops confirmed the mechanism of diagonal tension and compression state within the panel as found in the monotonic shear tests.2.2 Development of analytical modelsComposite walls are assumed to resist shear loading in three ways: shear resistance of the sheeting, shear resistance of the concrete core and from the sheet-concrete interaction. For the development of analytical models for the strength and stiffness, let us consider a composite wall in a practical building frame as shown in Fig. 7. The wall is connected to the building frame by sheet-frame fasteners. In practical circumstances, to construct such walls several steel sheets may benecessary and they should be connected together through seem fasteners. Let us consider b and a beFig. 6(a) Typical variation of diagonal strainFig. 6(b) Hysteretic loops for diagonal strains in test 3Behaviour of composite walls under monotonic and cyclic shear loading 77the height and width of the wall respectively. The applied shear load and shear deformation are represented by V and δ respectively.2.2.1 Analytical model for the stiffness of the composite wallShear stiffness of the profiled concrete coreThe derivation of analytical model includes the idea of transforming the profiled concrete core into an equivalent plain concrete core of rectangular cross-section having an average thickness of t eq .This simplified the problem and was used by Davies and Fisher (1979) and Easterling and Porter (1994a,b) successfully in analysing steel-deck-reinforced concrete diaphragms. The shear stiffness of the profiled concrete core is derived (Hossain and Wright 1998b) based on the strain energy approach. The shear flexibility (c c ) and stiffness (k c ) of the concrete core is expressed as:(2)where νc and E c are the Poisson’s ratio and elastic modulus of concrete respectively.Shear stiffness of the profiled steel sheetingThe shear flexibility (c s ) of the sheeting in composite wall is the displacement per unit shear load (δ/V ) applied normal to the corrugation profile as shown in Fig. 8. The total shear flexibility of the profiled sheet, c s , can be taken as the sum of terms, each for one of the various factors involved (Wright and Hossain 1998). The main components considered are due to: shear deformation of sheet (c 1), bending or distortion of corrugation profile (c 2), axial deformation of the boundary frame members (c 3) and local deformation of sheet at the sheet-frame and seam connections (c 4 and c 5).c s = c 1 + c 2 + c 3 + c 4 + c 5•for the case of model composite walls, the confining effect of the concrete (as confirmed from model tests) eliminates c 2.c c 1k c---2b 1νc +()E c at eq --------------------------==Fig. 7 Schematic of a framed composite wall under in-plane shear78K. M. Anwar Hossain and H. D. Wright•at seams between adjacent steel sheets for practical construction, the concrete carries almost all the shear forces and, therefore, c 5 may be ignored. In model tests, there was no seam connection as single sheet was used.•if the frame is considered to be very rigid, the axial deformations in frame members can be considered negligible, which eliminates the factor c 3.•if the connection details are such that the local deformation of sheeting is not allowed in sheet-frame fasteners than the factor c 4 can be omitted. This is the case for model tests where load is applied through both steel and concrete.So the stiffness of the sheeting in model tests by applying strain energy approach can be written as (Wright and Hossain 1998):(3)where t s , νs and E s are the thickness, Poisson’s ratio and elastic modulus of steel respectively. α is the ratio of the developed length of a profile to its projected length.Stiffness of the composite wallThe boundary frame in the model tests is considered to be formed by infinitely rigid elements pinned together at the corners and induces pure shear on the infill panel. No bending or distortion of the corrugation profile is allowed due to boundary condition and also the infill concrete acts as stiffener causing the flat cross section of the steel sheets to remain flat. This was confirmed from the model tests where sheet distortion was found to occur at the ultimate stages of loading associated with buckling of the sheeting.The stiffness of the composite wall is derived from the shear deformation of sheeting (Eq. 3),shear deformation of concrete core (Eq. 2) and from their degree of composite interaction. The composite flexibility (c w ) and stiffness (k w ) of composite walls can be derived as the sum of flexibility and stiffness of the double skins of sheeting and concrete core:(4)2.2.2 Analytical model for the shear strength of composite wallThe shear strength of composite wall is controlled by the diagonal tension failure of concrete,buckling of sheeting, the shear-transfer mechanism at steel-concrete interface and failure of wall-frame connections (Hossain and Wright 1998a). The actual post-cracking behaviour of the wall is a combined phenomenon of wall-frame connection and sheet-concrete interaction. The boundary connections should be rigid enough (as is the case for model tests) to induce the failure in the wall panels. The rigid boundary connections increase the sheet-concrete interaction by keeping sheet-concrete-sheet sandwich intact until buckling of the sheeting commences. The practical use of such walls in conjunction with the building frame is to increase the shear resistance of the frame under monotonic or cyclic loading. In such cases, the frame failure (which may lead to the total collapse of the building) is not desired and the failure of the infill wall governs the design. c s 1k s ---c 12αb 1νs +()E s at s ------------------------------===c w 1k w ----2c s c c +2k s ---1k c ---+2αb 1νs +()1νc +()a E c t eq α1νs +()2E s t s 1νc +()+[]-----------------------------------------------------------------------------------====Behaviour of composite walls under monotonic and cyclic shear loading 79Shear strength of the concrete coreThe analytical model for the shear strength of concrete core has been derived based on bi-axial stress conditions in the concrete (Kupfer and Gerstle 1973). The model (Hossain and Wright 1998b)includes diagonal tension limit state, which is the normal phenomenon in monotonic or cyclic shear loading condition as the failure criteria. The model also includes the idea of transforming the profiled concrete core into an equivalent plain concrete core of rectangular cross-section having an average thickness of t eq (Davies and Fisher 1979, Easterling and Porter 1994a,b). The shear strength of the profiled concrete core (V c ) can be written as:(5)where f 'c , f cu and f 't are cylinder, cube and splitting tensile strength of concrete.Shear strength of the profiled steel sheetingThe type of failure either buckling of sheeting or failure at sheet-frame connections depends on the boundary conditions. If the sheet-frame connection is sufficiently rigid then the failure will be due to buckling of the sheeting. The ultimate shear resistance of the sheeting for failure in the sheet-frame fasteners and also for elastic buckling mode of failure in case of rigid connections are derived (Wright and Hossain 1998). For the case of buckling mode of failure as observed in model tests, the general critical buckling formula suggested by Easley (1975) based on othotropic model can be used and the shear resistance of the sheeting can be written as:(6)where D x and D y are orthotropic constants for the profiled steel sheeting. β is a co-efficient ranging between 1.00 and 1.72, depending on the boundary conditions. β = 1.00 for simply supported conditions and β = 1.72 for clamped conditions (Easley 1975, Wright and Hossain 1998).Shear resistance of the composite wallModel tests on profiled steel sheet, profiled concrete and composite walls have revealed that the ultimate shear capacity of the composite wall can be conservatively obtained from the summation of individual shear resistances of sheeting and concrete core. The ultimate shear resistance of the composite wall for monotonic shear can be derived as:(7)The first term in Eq. (7) represents sheet resistance (from Eq. 6) and the second term representsprofiled concrete core resistance (from Eq. 5). The possible increase in concrete core capacity due to composite action and the resistance of the sheeting in contact with concrete are not taken into account. This makes Eq. (7), conservative. The influence of local buckling is not included, as it is not found important in pre-buckling stages of the sheeting and in the case of composite wall.V c bt eq f c ′f t ′⋅f c ′f t ′+-----------------------0.074at eq f cu ==V s 36βD x 14⁄D y 34⁄ab2------------------------=V w 72βD x 14⁄D y 34⁄a b 2------------------------0.074at eq f cu +72βD x 14⁄D y 34⁄a b2------------------------f c ′f t ′at eqf c ′f t ′+-------------------+==80K. M. Anwar Hossain and H. D. Wright3. Validation of analytical models under monotonic and cyclic loading3.1 Strength and stiffness of profiled concrete panelsAnalytical and model test results for strength and stiffness are summarised in Table 1. The slopes of the initial and re-loading part of the shear load-deformation responses (Figs. 8a-b) are used to determine the experimental stiffness of the panels. The experimental pre-cracking stiffness of the panels under monotonic and cyclic loading is found to be in good agreement and cyclic loading seems to have no effect. The cracking load of panels with cyclic loading is decreased by about 30%compared with monotonic shear panels (Table 1). The cyclic loading also reduces the ultimate shear load by about 28% compared to monotonic loading.For monotonic shear condition, the ratio of test to analytical stiffness ranges between 0.80 and 0.91. The corresponding strength ratio ranges between 1.12 and 1.26. They are supposed to be in reasonable agreement. Analytical Eqs. (2) and (5) can therefore be used safely to predict the shear stiffness and ultimate strength of profiled concrete panels under monotonic loading.The design Eq. (5) derived for monotonic shear loading condition seems to overestimate the ultimate load for cyclic loading condition (ratio of test to analytical ranges between 0.78 and 0.85).Eq. (5) is therefore, modified to Eq. (8) where a factor, φ, is introduced to take into account the reduction in strength due to cyclic loading.(8)The value of φ, can be varied from 0.73 to 0.80. Eq. (8) can safely (Table 1) be used to predict the strength of profiled concrete panels under cyclic loading (as the ratio of test to analytical model ranges between 1.03 and 1.07 (Table 1).V c 0.074φbt eq f cu ⋅φf c′f t ′at eq f c ′f t ′+-------------------==Fig.8(a)Typical load-deformation response of profiledconcrete panels (Monotonic shear) Fig.8(b)Typical load-deformation response of profiledconcrete panels (Cyclic shear)Behaviour of composite walls under monotonic and cyclic shear loading813.2 Strength and stiffness of profiled steel sheet panelsFigs. 9(a)-(b) show typical load-deformation responses of profiled steel sheet panels under monotonic and cyclic loading conditions. The sudden drop in load with large deformation after the peak load is due to the very sudden transition (snap-through) to tension field action and the substantial increase in associated deformation (as can be seen from the monotonic behaviour in Fig. 9a). This is the reason why buckling load is considered as the design load in the proposed model (Eq. 6) and post-buckling shear reserves between buckling and peak load are not considered.This will prevent the risk of sudden snap-through type failure in such panels. This also reflects the recommendations of Luo and Edlund (1996) and the ASCE-AASHTO Task Committee (ASCE-AASHTO 1977).The experimental pre-buckling load and stiffnesses as well as ultimate loads are summarised in Table 2. The buckling and ultimate loads for panels under cyclic loading are decreased by about 9%and 18% respectively compared with those under monotonic loading. The pre-buckling stiffness is also reduced by about 8%. The ratio of ultimate load to buckling load is decreased from about 1.24(for monotonic) to 1.12 (for cyclic). This means that post-buckling shear reserve is decreased by about 9% due to cyclic loading. The deformation at ultimate load (peak load) is also found higher for panels with cyclic loading (Fig. 9b).Eq. (3) is found to over predict the pre-buckling stiffness as the mean ratio of experimental to predicted values are found to be 0.94 and 0.86 for monotonic and cyclic loading respectively.However, Eq. (3) can reasonably predict the stiffness of the panels under both cyclic and monotonicTable 1 Strength, stiffness and design equation validation for profiled concrete panelsTest No.Concrete strength MPa f cu (f 't )Cracking load kNShear stiffness kN/mm Ultimate shear loadkNTestAnalytical Eq. (3) RatioTestAnalytical Eq. (5)RatioMonotonic loading121 (2.3)15.51471610.913327 1.26224 (2.3)13.5+161-3127 1.15424 (2.5)13.41291610.803127.6 1.12523 (2.2)13.81321610.823227.21.18Cyclic loading324 (2.4) 9.0+161-2226.821.5*0.821.03*625 (2.5)9.2 1411610.882326.8921.5*0.851.07*724 (2.4)9.01321610.822226.821.4*0.781.03*825 (2.3)8.81271610.7922.526.621.3*0.851.06**Using modified Eq. (8) for cyclic loading (φ = 0.80)+panel damaged due to machine malfunction。