Advanced Method for Modelling Hysteretic Behaviour of Semi-Rigid Joints

Abstract

This chapter provides an introduction to the Preisach model to describe the moment-rotation hysteresis curves of semirigid joints and analyze the transient dynamic response of flexibly connected steel frames. The Ramberg–Osgood model in conjunction with the empirical rules is first used to produce a set of hysteresis loops. A time-domain incremental method is adopted to evaluate the transient dynamic response of a portal frame under seismic excitation and other dynamic loads. The hysteresis loop and dynamic response characteristics using the Preisach model are compared with those using the Ramberg–Osgood model to validate the suitability of the Preisach model. A one-storey portal frame with semirigid joints is used to demonstrate the dynamic response analysis results in terms of the Preisach model, and to compare the results with those obtained by the Ramberg–Osgood model. The moment-rotation characteristics of the flexible connections are incorporated in the analysis as a spring-point element. Although, the Ramberg–Osgood model and the Preisach model produce consistent displacement response, the steady-state minor hysteresis loops produced by the Ramberg–Osgood model have nearly zero enclosed area, showing obvious disagreement with actually observed minor loops. Contrarily, the Preisach model produces more reasonable minor hysteresis loops with a certain energy dissipation capability.