Lateral Load Behavior of a Post-Tensioned Coupled Core Wall
A 40%-scale multi-story reinforced concrete coupled core wall structure with unbonded post-tensioned coupling beams was recently tested under quasi-static reversed-cyclic lateral loading. This paper provides an overview of the design and experimental results from this test. Conventional reinforced concrete coupling beams in seismic regions are often designed with two intersecting groups of diagonal reinforcing bars crossing the beam-to-wall joints. The placement of these reinforcing bars is a major challenge during construction. The new system eliminates the diagonal reinforcement by using a combination of high-strength unbonded post-tensioning (PT) steel and top and bottom horizontal mild steel reinforcing bars crossing the beam-to-wall joints to develop the coupling forces. The coupled wall specimen that was tested represented the most critical bottom three stories of an eight story prototype structure, consisting of two C-shaped wall piers, six post-tensioned coupling beams (two beams at each floor because of the C-shaped piers), tributary post-tensioned slabs at each floor, and the foundation. The less critical upper stories of the prototype structure were simulated analytically to obtain the axial forces and overturning moments imposed at the top of the bottom three stories. In addition to a dense array of conventional sensors, the deformations of the test specimen were monitored using a total of 14 two and three-dimensional digital image correlation (DIC) sensors, providing near-full-field response data of the most critical regions of the structure in the wall piers, floor slabs, and coupling beams. Ultimately, the high-fidelity measured data from the test specimen will be used to validate seismic design procedures and modeling/prediction tools for post-tensioned coupled wall structures. These procedures and tools may form the basis for the future implementation of this novel structural system as “special” reinforced concrete shear walls in medium and high seismic regions of the U.S.
Proceedings of the 10th National Conference in Earthquake Engineering, Earthquake Engineering Research Institute, Anchorage, AK