Seismic Behavior of a Modern Concrete Coupled Wall

RC core walls are used commonly in modern building construction as the primary lateral load–resisting system. To meet architectural constraints, including elevator, stair, and doorway openings, common configurations include walls coupled together with heavily reinforced, low-aspect-ratio coupling beams. Numerous studies have focused on coupling beams and improved seismic performance and design of coupling beams. However, far fewer research programs have studied the seismic behavior of the coupled wall system. Coupled walls are typically used in mid- to high-rise construction, and understanding their seismic response requires simulation beyond the coupling beam and must include all important yielding components of the system. A research project was undertaken to investigate the response of a midrise coupled wall designed to meet current codes. The advanced testing capabilities of the University of Illinois at Urbana-Champaign George E. Brown, Jr. Network for Earthquake Engineering Simulation (NEES) experimental facility were used to conduct a large-scale test of a coupled wall. The test specimen modeled the lower 3 stories of a 10-story building. The demands from the upper stories were imposed on each pier using an innovative loading device capable of imposing shear, moment, and axial loads or displacements. Damage progression included yielding of coupling beams, yielding of wall piers, spalling in the wall piers, and the coupling beams. Specimen failure occurred almost without warning at 2.27% drift, resulting in significant loss of lateral and axial load–carrying capacity. The damage sustained included concrete core crushing and longitudinal bar buckling in the compressive wall pier. These experimental results were combined with prior test data to develop improved design models for coupled wall systems.