Modeling of cyclic joint shear deformation contributions in RC beam-column connections to overall frame behavior

Abstract

In seismic analysis of moment-resisting frames, beam-column connections are often modeled with zones. However, it has been demonstrated that, in ductile reinforced concrete (RC) moment- resisting frames designed based on current codes (to say nothing of older non-ductile frames), the zones are in fact not rigid, but rather undergo significant shear deformations that contribute greatly to global drift. Therefore, the rigid joint assumption may result in misinterpretation of the global performance characteristics of frames and could consequently lead to miscalculation of strength and ductility demands on constituent frame members. The primary objective of this paper is to propose a rational method for estimating the hysteretic shear behavior of RC connections and for incorporating this behavior into frame analysis. The authors tested four RC edge beam-column-slab connection subassemblies subjected to earthquake-type lateral loading; hysteretic shear behavior is investigated based on these tests and other laboratory tests reported in the literature. An analytical scheme employing the modified compression field theory (MCFT) is developed to approximate shear stress vs. shear strain response. A connection model capable of explicitly considering hysteretic shear behavior is then formulated for nonlinear structural analysis. In the model, a is represented by elements located along the edges and nonlinear rotational springs embedded in one of the four hinges linking adjacent elements. The connection model is able to well represent the experimental hysteretic shear behavior and overall load- displacement response of connection subassemblies.