Design bearing capacity of the initial imperfect lattice shell

Abstract

Initial imperfections can cause evident influence on the bearing capacity of lattice shells. In this article, the member initial imperfections including the initial bending and residual stress are considered by the Marshall model which is a phenomenon model based on the hysteresis loop of the real structural imperfect member under cyclic loading. The geometrical initial imperfection of lattice shells resulting from the structure assembly deviation is represented by the normally distributed random variable. The bearing capacities of lattice shells with initial imperfections are assumed to be distributed normally, and then this assumption is proved correct by the nonparametric test. The expressions of the mean value and variance estimators of the normally distributed structural bearing capacities are derived by the maximum likelihood method. A new method to calculate the design bearing capacity of the initial imperfect lattice shell at a uniform probability level is proposed, and its error expression at certain confidence level is derived. Numerical analysis indicates that some members of the structure at the ultimate limit state get buckled as a result of the member initial imperfections. The structure bearing capacity can be markedly overestimated if the member initial imperfections are neglected. The nonlinear design bearing capacity of the lattice shell at a uniform probability level cannot be acquired by the methods suggested by the structure design code.