Supplemental Materials Nonlinear Hysteretic Truss Model for Diagonally Reinforced Concrete Coupling Beams

Abstract

Wall piers connected by diagonally reinforced concrete coupling beams are widely used as the lateral-force resisting system of tall buildings in seismic regions. A fundamental incongruity exists in current nonlinear modeling practice for such systems: walls are typically modeled in the initial uncracked state, whereas coupling beams are assigned a secant stiffness to the yield point. This paper presents the derivation of a nonlinear hysteretic truss model for diagonally reinforced concrete coupling beams that resolves this inconsistency and validates it against experimental data reported in the literature. The model explicitly couples flexural, shear, and axial deformations through truss action in a unified nonlinear hysteretic framework, offering a clear improvement over first-generation purely phenomenological models based on shear or moment springs. Unlike these models, the proposed model develops axial compression when restrained against lengthening, and accounts for the effects of this compression, allowing redistribution of the shear force between the framing wall piers. Its applicability is demonstrated through the nonlinear response history analysis of a fifteen-story coupled wall building.