Strength and Stiffness Deterioration Material Influence on Demand Parameters in Steel Moment Frames

Abstract

ABSTRACTThe moment resisting frames (MRF) are one of the three main structural steel typologies used for seismic design of steel frames. They are characterized as the most ductile structural type possessing a large number of possible dissipative zones, following the fact that plastic hinges can develop both in the beams and the columns. Possessing the feature of being the most ductile type, these structures exhibit very large deflections before the structural damage occurs. Additionally, the strength and stiffness deterioration of the steel material due to cyclic loading increases the effect of the lateral forces and represents the most realistic behaviour of this structural system. Hence, in this research study an improved approach using updated material model for evaluating the steel MRFs' behaviour is implemented in order to tackle the deficiency in the assessment of this type of structures. Firstly, the modelling is performed using the nonlinear beam – column elements with distributed plasticity for both the beams and the columns. Then, the same frame model is developed using the elastic beam – column elements ending with zero‐length plastic hinges modelled by a stiffness deteriorating steel material referred to as Ibarra – Krawinkler (IK) model. Two sets of seven acceleration records are chosen as realistic earthquake loading to represent the medium hazard seismicity (MH) and high hazard seismicity (HH) scenarios. Incremental nonlinear dynamic analysis of the frames is conducted by scaling the records in order to attain various levels of relative intensities. They are extracted from the database and scaled to match the EC8 elastic spectra for the two hazard scenarios.