The Reliability Analysis Of Ultimate Load Capacity For Folding Reticulated Shell

It is important to analyse the ultimate load capacity of folding reticulated shell during design and making it. The facors influencing the ultimate load capictiy are random. The traditional code cann't satisfy the requirement afer the development of reliability theory for structure (The technical specification for latticed shells still use the safety-factor to get the stability storage of structure),because it cann't take the random factors into care. And the concept of reliability need to be brougt into the shell-design in order to acquire the acceptable failure probability.Firstly,the parameters related to the ultimate load capacity are listed according to experiments, design handbooks and references,and the statistical theroy is applied to study the characteristic of the parameters; In the variable scope ,the single parameter sensitivity ansysis is carried out to acquire some of them that have a bigger infurence of the ultimate load capacity;Because of the nonlinear relationship,the traditional equation can not express the relationship between them. So a new approach need to be found out .The BP neural net work theroy is introduced to fit for the relationship according to the Multilayer Net Nonlinear reflection theory ;At the same time ,the Parameters analysis is carried out to obtain the initial samples of ultimate load capacity about the common size shell .The tendence between the paramerers and the ulitimate load capacity and the mechanism of them can be found out.Secondly,According to the geometrical explanation of reliability and several variables modle, Optimization Algorithm is used to solve the reliability of the folding reticulated shell on the basis of BP neural net work to imitate the limit equation of ultimate load capacity . The Matlab program language is used to solve the problem. The Program can solve the simple-load combination(dead load+live load).when deal with the wind-load ,it is divided into two according to the orientation. The safey factor is assumed to 3 and 4 according to the consequence afer the collapse of the shells,and the reliability is computed about the shell of common size by calibration method . When all the reliability numbers are obtained ,the average is to be the target reliability .The result indicate that :The target reliability is 3.85 when the safety factor is 3,and the target reliability is 4.60 when the safety factor is 4.So the 3.85 is acquired as the target reliability because the consquece is less than the common strucrures afer the collapse ,and the acceptable failure probability is 5.901e-5.