Lateral load behavior of unbonded post-tensioned hybrid coupled walls

This paper describes an ongoing research program at the University of Notre Dame on the seismic behavior and design of unbonded post-tensioned hybrid coupled walls. Concrete walls are coupled using steel beams and unbonded post-tensioning, without embedding the beams into the walls. Analytical results indicate that unbonded post-tensioned steel coupling beams with stiffness and ultimate strength similar to embedded steel coupling beams can be designed to soften and undergo large nonlinear rotations of up to 7.5 percent without significant permanent residual rotations upon unloading. The nonlinear rotations in the beams occur primarily through gap opening along the beam-to-wall connections. Flange cover plates are used to delay the yielding of the beams in compression and top and bottom seat angles are used at the beam-to-wall connections to provide inelastic energy dissipation. An experimental investigation of unbonded post-tensioned hybrid coupled wall subassemblages is currently underway at the University of Notre Dame.