Development of more accurate cyclic hysteretic models to represent RBS connections

Abstract

The concept of Reduced Beam Section (RBS) connections in steel framed buildings have been widely adopted in previous studies as well as European and American Design codes (EN1998-3, ANSI/AISC 358-16 and FEMA 350) as a means of providing safe ductile fuse behaviour in the beam in order to protect the column from any significant damage. However, modelling the hysteretic behaviour of RBS connections under earthquake excitations can be challenging due to their non-linear complex behaviour. This paper presents a database of detailed and accurate modified-Ibarra–Krawinkler (mIK) models that can reliably capture the cyclic hysteresis behaviour of fully welded RBS connections over a wide range of different RBS geometries. An experimentally validated Finite Element (FE) model was developed using ABAQUS to accurately predict the cyclic hardening and strength degradation of RBS connections. Subsequently, a comprehensive parametric study was conducted on 1480 different American wide flange RBS and full section beams under cyclic loading. The results were then used to assess the influence of key RBS design parameters on the structural performance of the connections. It was shown that the conventional method of predicting mIK parameters cannot accurately capture the actual hysteresis behaviour of some RBS connections and may lead to unreliable predictions. Using the results of the validated FE models, a comprehensive database of 1480 different beams was developed which provides: (1) the beams full cyclic moment–rotation-hysteresis at the plastic hinge location up to 0.07 rad rotation following the SAC loading protocol, (2) appropriate mIK parameters to accurately capture the beam’s cyclic response in OpenSees, for non-linear dynamic analysis. The results of this study should prove useful in seismic design and assessment of RBS connections.