A USER-FRIENDLY ENVIRONMENT FOR NONLINEAR-STRUCTURALANALYSIS

摘要

Nonlinear analysis of structures has become increasingly important in the study of structural response tohazardous loads such as earthquake and blast. Currently available tools for such analysis are researchprograms lacking convenient user-interfaces, or are general purpose Finite Element programs that requirevery fine-grained modeling that is often impractical to the engineer. This paper describes the outcome of acollaborative effort between the University at Buffalo and Larsa, Inc. in developing a user-friendlyenvironment for such analyses, aimed at overcoming the above-mentioned shortcomings. Theenvironment provides the ability to perform modeling at the necessary level, yet not requiring the engineerto have to deal with the fine-grained details. Both theoretical and implementation aspects are discussed.Firstly inelastic material models as well as uni-axial and coupled 'spring' elements based on these modelsand the user-interfaces related to them are discussed. Next, two inelastic beam-column elements, one withconcentrated uncoupled flexural plasticity and the other with distributed plasticity with three-dimensionalinteraction are described along with the various numerical as well graphical outputs representing to theinelastic response of such elements. Nonlinear static as well as dynamic analysis procedures utilizingautomatic step size control algorithms are discussed next. Analysis features are described for theequivalent static procedure (pushover analysis) used in seismic design and in the load redistributionanalysis under element loss such as under blast loading. Since both these load conditions involve constantload profiles with only a scalar parameter, an automatic stepping algorithm combined with an arc-lengthcontrol strategy is utilized. Several illustrative examples of all these features are presented.