Experimental Evaluation of Posttensioned Hybrid Coupled Wall Subassemblages

Eleven half-scale experiments were conducted to investigate the nonlinear reversed cyclic behavior of coupling beam subassemblages in a new type of hybrid coupled wall system for seismic regions. In this new system, coupling of concrete walls is achieved by posttensioning steel beams to the walls using unbonded posttensioning tendons. Different from conventional hybrid coupled walls, the coupling beams are not embedded into the walls. Each test specimen described in this paper includes a steel coupling beam and the adjacent concrete wall regions at a floor level. Steel top and seat angles are used at the beam-to-wall connections to yield and provide energy dissipation. The test parameters include the angle leg thickness, angle gauge length, beam flange cover plate, posttensioning steel area, and beam depth. The results demonstrate excellent stiffness, strength, and ductility characteristics of properly designed subassemblages under cyclic loading, with considerable energy dissipation concentrated in the angles. The specimens were able to sustain large nonlinear displacements without significant damage in the beams and the wall regions; demonstrating that these structural components would require little repair, if any, after a severe earthquake. The residual deformations upon unloading of the specimens were negligible due to the restoring effect of the posttensioning force.