Optimization Design Of Prestress Of Long-span Suspendome Structure

Suspendome is a new composite space structure system composed of upper single-layer reticulated shell and bottom cable-stayed system,with less steel,light weight,reasonable force,economic and aesthetic.The determination of the most reasonable prestress is the core problem of the suspendome structure.In order to obtain the optimal design scheme of hoop cable prestress.In this paper,systematic optimization analysis and comparative study are carried out in combination with various design schemes of hoop cable prestress.The specific contents are as follows:(1)A set of reasonable prestress is usually found by determining the prestress ratio of each hoop cable and then determining the level of hoop cable prestress of prestress according to some rules.In order to determine the optimum hoop cable prestress ratio,this paper introduces a new method to determine the prestress ratio: the method of fan-shaped core area of strut.According to the loading characteristics of the single-layer reticulated shell,the prestress ratio obtained by this method is more consistent with the actual situation.(2)In order to determine the optimal design scheme of hoop cable prestress,in this paper,existing methods for determining prestress ratio,including geometric method,strut controled area method are selected,and the level of hoop cable prestress was identified useing two criteria for radial displacement equality at the support and vertical displacement equality at the lattice shell peak are selected.Then six combination schemes for determining the hoop cable prestress obtained by crossing.The rigid cable which directly determines the hoop cableprestress and the improved rigid cable method are selected as two prestress design schemes.The research background of the suspendome of the Badminton Hall of the 2008 Beijing Olympic Games,Ansys-apdl parameterized language is used to design and program an optimization program that takes component size and prestress as design variables,the slenderness ratio,deflection,stability stress and strength stress as state variables,and the lightest weight of the structure as the objective function.On this basis,the influence of various load conditions is considered.By using the zero-order optimization method in ANSYS,systematic optimization analysis and comparative study of eight prestressing combination schemes are carried out.(3)Aiming at the speed and accuracy of optimization,this paper improves the zero-order optimization method.Then,on the basis of the improved zero-order optimization method,the optimization design of the prestress is carried out,and a comprehensive comparative study on steel consumption,stiffness,iteration times and material utilization ratio of components is carried out.The results show :the improved zero-order optimization method effectively improves the speed and accuracy of structural optimization;On the basis of this optimization method,the minimum weight,the maximum stiffness of the structure can be obtained under the scheme combining the method of fan-shaped core area of strut with the radial displacement equality criteria.At the same time,it points out the superiority of determining the prestress ratio of hoop cable by the method of fan-shaped core area of strut,and the simplicity and validity of the derivation method.(4)In this paper,aiming at the influence of hoop cable prestress on the static performance of suspendome structure,the static analysis of suspendome structure is carried out by using different ratio coefficients of hoop cable prestress.The influence hoop cabl prestress on the internal force,displacement and vertical deformation of structure is discussed comprehensively,which can provide reference for similar structural analysis and design in the future.