Stability Analysis Of Kiewitt Single Layer Latticed Spherical Shell With Stochastic Imperfections Method

The effect of nonlinear (geometric nonlinearity,material nonlinearity) of Kiewitt single layer latticed spherical shell is very obvious as a result of the global thin-shell surface and compression-mainly. The single layer latticed spherical shell belongs to the imperfection sensitive structure. The study of stability analysis of Kiewitt single layer latticed spherical shell with stochastic imperfections has many important theoretical and practical values.A intelligent program was imbedded into the improved calculation procedure of the advanced stochastic imperfections method on the conclusion of the advantages and disadvantages of the advanced stochastic imperfections method. The intelligent program can automatically control the calculation numbers of advanced stochastic imperfections method and end the history of the calculation number of samples selected by experience. The intelligent controlling procedure establishes the foundation of large-scale parametrization analysis.It also makes the advanced stochastic imperfections method better to be applied.A systematical stability analysis of Kiewitt single layer latticed spherical shell with stochastic imperfections was carried out to study the stability behavior on the base of large-scale parametrization analysis (the times of non-linear analysis was no less than 82000). The influence of the span, the rise-to-span ratios, the sectional dimensions, the maximum of initial imperfections, the elasticity and plasticity to critical design load of Kiewitt single layer latticed spherical shell were also studied. The calculation numbers of the stochastic imperfections method were detailly studied. The results show that the calculation number of the stochastic imperfections method is stability, generally from 55 to 60.The imperfect influence coefficient and the plastic influence coefficient were detail studied which based on large-scale parametrization analysis. The imperfect influence coefficient can be taken 0.45 desirable when the maximum initial imperfections is L/1000 and 0.35 desirable when the maximum initial imperfections is L/500 and 0.25 desirable when the maximum initial imperfections is L/300. No matter the structure have initial imperfection, the plastic influence coefficient can be taken 65%-70% which means the critical load of Kiewitt single layer latticed spherical shell may nearly drop by 30%-35% if material non-linear was considerd.The probabilistic reliability of the consistent imperfection mode method was also studied. The result showed that the proportion of the reliability over 90% is 80%~90% when elastic analysis was carried out with consistent imperfection mode method and about 75% when elastic-plastic analysis. Therefore, the consistent imperfection mode method should be adopted cautiously.