Inelastic Post-Buckling Analysis of Space Trusses Using Fixed Inceremental Displacement Method

This paper presents a novel scheme for large deformation analysis of space truss structures, including both geometric and material nonlinearities, using a predictor-corrector procedure, titled as fixed incremental displacement (FID) method. The nonlinear equilibrium equations are solved using an incremental-iterative method based on the displacement control scheme, as, by employing a specified displacement, the corresponding load will be obtained. In the present method, the ratio of the size of increment displacement vector to that of total displacement is assumed to be constant at the beginning of each increment. The geometric nonlinearity is considered based on an updated Lagrangian formulation, while the material nonlinearity is accounted for by tracing a complete stress-strain relationship. A computer program based on the algorithm is developed for analysis of space structures with complex behaviors, including snap-through buckling, snap-back, unloading and inelastic post-buckling analysis. This algorithm can accurately trace the equilibrium path of nonlinear problems. To demonstrate the efficiency and accuracy of the method developed here, some well-known trusses are investigated and analyzed using the aforementioned algorithm and the results are compared with those of cylindrical arc-length method.