结构力学英文
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(1)Geometrically stable system
Under the action of the loads, the system still maintains its shape and remains its location if the small deformations of the members are neglected as shown in Fig.2.1
2.2 the concept of degrees of freedom and restraints
In the analyzing geometric construction of structures, it is very feasible to consider one part of the members or joints of a system as an object which possesses degrees of freedom, whereas other part of the members or joints of the system as restraints which restricts the movement of the object. The relationship of these two parts are then analyzed and whether or not the system will be determined. Accordingly, the concept of degrees of freedom and restraints of a system is discussed first of all
(2)Geometrically unstable system Under the action of the loads, the system will change its shape and its location if the small deformations of the members are neglected as shown in fig,2.2 Corresponding to geometrically stable and unstable system, there are internally stable and unstable systems as well. A structure is considered to be internally stable, or rigid, if it maintains its shape and remains a rigid body when detached from the supports
For simplicity we call a structure as a system, For instance, framed structures are named framed systems.
According ttheir members, framed systems can be classified into two categories:
Geometric construction analysis o2f.1sptururpcotusereof analyzing geometric construction of structures,
stable and unstable structural systems
in order to withstand and transmit load, the geometric shape of a structure system is variable under loads, the structural system cannot be used as a structure.
Conversely , a structure is termed internally unstable if it cannot maintain its shape and may undergo large displacements under small disturbances when not supported externally.
it should be realized that all physical bodies deform when subjected to loads; the deformation in most engineering structures under service conditions are so small that their effect on the geometric construction analysis of the structures can be neglected.
Purpose of analyzing geometric construction of structures is as following: (1) To estimate whether or not a system is geometrically stable, so as
to determine whether the system can be used as a structure or not; (2) To discuss geometric construction rules of stable systems.
2.2.1the degrees of freedom
The degrees of freedom of a system are the numbers of independent movements which are required to locate the system fully.obviously, arigid body has three degrees of freedom in a planar coordinate system(six degrees of freedom in a three dimensional coordinate system),e.g., the position of member AB may be determined by three parameters Xa, Ya and
Under the action of the loads, the system still maintains its shape and remains its location if the small deformations of the members are neglected as shown in Fig.2.1
2.2 the concept of degrees of freedom and restraints
In the analyzing geometric construction of structures, it is very feasible to consider one part of the members or joints of a system as an object which possesses degrees of freedom, whereas other part of the members or joints of the system as restraints which restricts the movement of the object. The relationship of these two parts are then analyzed and whether or not the system will be determined. Accordingly, the concept of degrees of freedom and restraints of a system is discussed first of all
(2)Geometrically unstable system Under the action of the loads, the system will change its shape and its location if the small deformations of the members are neglected as shown in fig,2.2 Corresponding to geometrically stable and unstable system, there are internally stable and unstable systems as well. A structure is considered to be internally stable, or rigid, if it maintains its shape and remains a rigid body when detached from the supports
For simplicity we call a structure as a system, For instance, framed structures are named framed systems.
According ttheir members, framed systems can be classified into two categories:
Geometric construction analysis o2f.1sptururpcotusereof analyzing geometric construction of structures,
stable and unstable structural systems
in order to withstand and transmit load, the geometric shape of a structure system is variable under loads, the structural system cannot be used as a structure.
Conversely , a structure is termed internally unstable if it cannot maintain its shape and may undergo large displacements under small disturbances when not supported externally.
it should be realized that all physical bodies deform when subjected to loads; the deformation in most engineering structures under service conditions are so small that their effect on the geometric construction analysis of the structures can be neglected.
Purpose of analyzing geometric construction of structures is as following: (1) To estimate whether or not a system is geometrically stable, so as
to determine whether the system can be used as a structure or not; (2) To discuss geometric construction rules of stable systems.
2.2.1the degrees of freedom
The degrees of freedom of a system are the numbers of independent movements which are required to locate the system fully.obviously, arigid body has three degrees of freedom in a planar coordinate system(six degrees of freedom in a three dimensional coordinate system),e.g., the position of member AB may be determined by three parameters Xa, Ya and