The null configuration model in limit load analysis of steel space frames

Abstract

AbstractThis paper briefly presents a numerical model for the geometric and material nonlinear limit load analysis of steel space frames under large displacements. This approach favors a global discretization by 1D beam‐column finite elements over the one with 3D elements. The steel cross‐section is discretized with 2D elements so that the fiber decomposition procedure can be applied to solve the material and geometrical nonlinear behavior of the cross‐section under biaxial moments and axial forces. A local discretization of each beam element based on the comparative body model (i. e., a prismatic body discretized using brick elements, element by element, during the incremental‐iterative procedure) allows determining the torsional constant of the cross‐section under limited warping. The model implements bending, lateral and torsional stability effects. For the large displacement analysis, an originally developed Null Configuration Model (NCM) is applied as an incremental application of the Total Lagrange – small displacement theory. A step‐by‐step procedure for the incremental loading of a follower load is applied. The numerical model has been implemented in a computer program for the practical engineering computation of the limit load of steel space frames. Some of model's possibilities are illustrated in the presented practical example which also shows the efficiency and the accuracy of the developed algorithm.