| The research reported in this dissertation is part of a larger effort undertaken by Cornell's Department of Structural Engineering and its Program of Computer Graphics. The fundamental goal of the research is to further the development of practical, economical methods for the static and dynamic nonlinear analysis and design of three-dimensional steel frames.; The research presented here is concerned with the development, implementation, and evaluation of nonlinear analysis techniques which are capable of modelling the geometrically and materially nonlinear behavior of statistically-loaded steel frames. The nonlinear analysis program developed in this work employs a prismatic, three-dimensional beam-column element with twelve degrees of freedom. Geometric nonlinearities are modelled with a geometric stiffness matrix and an updated reference geometry. The assumption of large displacements but small strains has been adopted. Particular emphasis has been placed on the development of accurate yet computationally efficient material nonlinearity models. Full cross-section plastification is modelled by zero-length plastic zones at the element ends. Upon formation of a plastic hinge, and subsequent inelastic interaction of the axial force and bending about the two principal axes is accounted for with a single-equation yield surface having full slope continuity. Elastic unloading is permitted, and its occurrence is signalled by negative plastic deformations at a plastic hinge. Residual stress effects are modelled in a restricted yet efficient manner. Various analysis types and solution methods have been implemented in the analysis program and offer considerable flexibility in frame analyses.; Several numerical examples are presented to demonstrate the accuracy, efficiency, and suitability of the analysis techniques in investigating realistic three-dimensional steel frame behavior. Examples comparing various structure models, solution methods, and analysis types are also presented. |
