Experimental Evaluation of Posttensioned Precast Concrete Coupling Beams

This paper describes the results from eight half-scale experiments of unbonded posttensioned precast concrete coupling beams under reversed-cyclic lateral loading. Each test specimen includes a coupling beam and the adjacent concrete wall pier regions at a floor level. Under lateral loads, the nonlinear displacements of unbonded posttensioned coupling beams are governed by the opening of gaps at the beam-to-wall joints. Steel top and seat angles are used at the beam ends to yield and provide energy dissipation. The test parameters include the beam posttensioning tendon area and initial stress, initial beam concrete axial stress, angle strength, and beam depth. The results demonstrate the lateral stiffness, strength, and ductility of the coupling beams under cyclic loading, with considerable energy dissipation concentrated in the angles. It is shown that the residual displacements of the structure upon unloading are small due to the restoring effect of the posttensioning force. The sustained chord rotation capacities of the test specimens are compared with those from previous tests of monolithic coupling beams.