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Buckling design of large circular steel silos subject to wind pressure
YangZhao,Qing-shuaiCao,LiangSu Space Structures Research Center, Zhejiang University , Hangzhou 310058, China
GMNIA—geometrically and materially nonline aranalysis of the imperfect silo.
Numerical results and discussions of the reference silo
The buckling modes in Load Case WF shift into the well-known elephant-foot deformation at the bottom part of the shell wall, which is induced by the meridional compressive stress. In such case, the vertical frictional pressure acting on the internal surface of silo wall becomes predominant to the buckling deformation.
Conclusions
The following conclusions can be drawn from these investigations: The buckling behavior in Load Case WE, is aห้องสมุดไป่ตู้most independent of the material nonlinearity, while the buckling resistance and buckling mode is much sensitive to weld imperfection. In Load Case WF, both the material nonlinearity and geometrical nonlinearity effect is strong and detrimental to buckling behavior of steel silos, resulting in decrease of buckling resistance.
Bulk solid pressure For the squat silos,the filling pressures Phf and Pwf are given by following equations
And the distributions of solid pressures along the depth are shown in Fig.3.
Buckling modes of the reference silo for Load Case WF(wind and full silo).
Buckling modes of the reference silo for Load Case We(wind and empty silo).
LBA—linear elastic bifurcation analysis of the perfect silo; GNA—geometrically nonlinear elastic analysis of the perfect silo; GMNA—geometrically and materially nonlinear ranalysi sof the perfect silo; GNIA—geometrically nonlinear elastic analysis of the imperfect silo;
Loadcases
Wind pressure The wind action has been an integral part of structural design. The distribution and magnitude of wind pressure on silo structure are to be calculated in accordance with EN1991-1-4. The circumferential variation of the pressure distribution Cp (positive inward)on an isolated closed roof silo is recommended by EN1993-4-1 in following expression:
Numerical analysis procedure
The buckling behavior of steel silos subject to wind pressure is investigated using the commercial general purpose finite element computer package ANSYS. The 8-node quadratic isoparametric shell element SHELL93 involving both bending and membrane effect is used to discretize the shell wall. Each finite element node has six degrees of freedom(DOF). The limit state of buckling should be taken as the condition in which all or part of the structure suddenly develops large displacements normal to the shell surface.
王启宇 S314020053
Table of Contents
Introduction Load cases Numerical analysis procedure Numerical results and discussions of the reference silo Conclusions
References
[1] EN 1991-4.Actions on structures—Part 4:Silos and tanks. European Standard; 2006. [2] EN 1993-4-1.Design of steel structures–Part4-1:silos.European Standard; 2007. [3] EN 1990.Basis of structural design. European Standard; 2002. [4] EN 1991-1-1.Actions on structures-Part1-1:general actions:densities, selfweight, imposed loads for buildings. European Standard; 2002.
References
Introduction
Large steel silos widely used for storing huge quantities of granular solids in industry and agriculture are typical kinds of thin-walled structure. With the development of domestic economy, both the number and capacity of steel silo has been increasing for recent decades. Large steel silo is usually squat with a large diameter to thickness ratio, which is particularly vulnerable to buckling under wind pressure .