Ultimate drift ratio of non-ductile coupling beams

Abstract

This chapter investigation the seismic performance of coupling beams designed according to nonseismic provisions. Two coupling beam specimens in 1/4 scale were prepared for investigation. Tests were conducted using an existing loading frame installed in the Harbin Institute of Technology. The test setup represents typical loading condition in a coupling beam in that the coupling beam is subject to end shears. A load cell was installed to measure the shear load. Transducers were used to measure the relative displacements between the top and bottom stubs and the displacements within the plastic hinges. The specimens were subject to a series of positive and negative loading cycles. First, shear load was applied (the first push cycle) until obvious reduction in stiffness was observed. The corresponding displacement was denoted as U1. Two complete cycles of push-pull loading were performed to achieve the targeted displacement. When subject to cycles of push-pull loading, failures of all the specimens were due to shear. Formation of cracks in specimens was similar to each other. In the first few loading cycles, flexural cracks were found within the plastic hinges at the two ends. Subsequently, shear cracks were developed with spalling of the concrete cover within the plastic hinges.