Reinforced concrete core walls are commonly used in modern building construction as the primary lateral-load resisting system. Common core wall configurations include solid walls in one direction and walls with openings in the orthogonal direction to accommodate required architectural openings for elevators or other access systems. Therefore, in the orthogonal direction, the walls are coupled together with heavily reinforced beams. Typically, these beams have lower aspect ratios and prior earthquake damage has proven they are susceptible to significant damage if not properly designed for the plastic shear demand or detailed to accommodate the required rotations to meet the system drifts. A significant amount of research has focused on individual coupling beams, and these results have dramatically improved the seismic performance of the beams. However, the few research programs have studied the seismic behavior of actual modern coupled walls systems, and most have focused on low-rise structures. Yet, most commonly coupled walls are used in elevator cores, which are more typical in mid-rise construction. A research program was undertaken to specifically study this category of structural system. The advanced testing capabilities of the NEES University of Illinois at Urbana-Champaign (UIUC) testing facility permitted unique experimental simulation of this system.
The structural coupled wall specimen was designed to investigate a wall with typical geometry and reinforcement. The specimen simulated a ten-story building in a region of high seismicity. To maximize the specimen dimensions and focus on regions in which inelastic action occur, only the lower three stories were modeled in the laboratory. Specialized load-and-boundary-condition boxes (LBCBs) were used to simulate demands originating from the upper stories of a 10-story structure subjected to an ASCE 7-05 lateral load distribution. The total moment applied to the top of the specimen was proportioned to meet the target individual pier moments and coupled moment computed using a continuum analysis of the ten-story wall. The wall piers included concentrated boundary elements; the coupling beams had diagonal reinforcement in conformance with ACI 318-08.