Nonlinear cyclic Truss Model for analysis of reinforced concrete coupled structural walls

This paper discusses the Truss Model proposed by Panagiotou et al. (ACI Struct J 109(2):205–214, 2012) for modeling reinforced concrete coupled structural walls. The model is validated with the landmark seismic testing of two 1:4 scale seven-story test specimens reported in Santhakumar (The ductility of coupled shear walls. Dissertation, University of Canterbury 1974) and in Paulay and Santhakumar (J Struct Div 102(1):93–108, 1976). The first specimen, Wall A, incorporated conventionally reinforced coupling beams whereas the second specimen, Wall B, incorporated diagonally reinforced coupling beams. These two specimens attained roof drift ratios of at least 1.7% before initiation of lateral strength degradation. Coupling beams in specimen Wall A exhibited significant strength degradation due to sliding shear, whereas coupling beams in specimen Wall B maintained the capacity throughout. We compare key overall and local responses reported for the two specimens with those computed with the Truss Models, as well as responses that could be only computed. In the latter, we show that when the beams effectively coupled the walls, the shear force at the wall base was mainly resisted by the wall being compressed. Moreover, the analysis shows that the first level coupling beams develop greater shear forces than the other beams despite all beams were identically reinforced. This is caused by the restraint provided by the fixed-base walls and by the kinematics of the strongly coupled walls. The Truss Model captures these responses because it explicitly considers the axial-flexure-shear interaction of RC walls and beams.