Geometric and material nonlinear analysis of three-dimensional steel frames

Abstract

Results obtained through theoretical and empirical studies which examined the nonlinear behaviour of construction members enabled us to characterize the behaviour of construction systems under external effects more closely. The calculation methods that took into consideration the nonlinear behaviour of the construction members and the nonlinear effects of their geometrical variations had to be developed in order to evaluate these phenomena and to design structures according to their collapse load principle. In the presented study, a computer program was developed for the characterization of structural systems by taking into consideration the nonlinear conditions of material behaviours under increasing loads and by considering the second-order effects. A matrix-replacement method was used as the basis for developing the program, which takes into consideration the effects of axial forces on the stiffness of the member by using the stability functions and the effects of plastic hinges by systematically changing the stiffness matrix in each occurrence of the plastic hinges. In the study, based on the results obtained from the examples, which were solved by the developed program, it was identified that the program could yield rapid and reliable results depending on the user-defined values (number of nodes, error limit for the iteration) and it is observed that the results are consistent with the literature. The obtained results in this study have contributed to capability of converting two dimensional analyses to three-dimensional analysis of stability functions developed.