Computation of critical initial imperfection of truss structures

A method for computing the critical (worst) initial imperfection of elastic truss structures is presented, on the basis of a previous work of the writers. This method can deal with initial imperfections of various properties, including loading pattern vectors, nodal initial position vectors, initial member length, and the product of Young's modulus and cross-sectional area. Imperfection sensitivity matrices, which express the effects of initial imperfections, are computed compatibly with the method of finite element analysis of truss structures. Critical initial imperfections of a reticulated elastic truss dome structure are investigated in detail as a numerical example. The effects of various kinds of initial imperfections are compared quantitatively. It is shown that the load-bearing capacity computed for the critical initial imperfection gives the lower bound on the capacity for the imperfections chosen at random. The present method is less costly and more accurate than the method of random imperfections.