Clayton, Dowden, Winkley, Berman, Bruneau, and Lowes 2012
A Self-Centering Steel Plate Shear Wall System (SC-SPSW) is connected at the beam and column interfaces with post-tensioning tendons. A subassembly featuring the shear wall and a one third scale test frame were tested under quasi static cyclic loading, and the results of all experimentation and numerical evaluation demonstrated that the structure both has the ability to self center the system, and that the system undergoes cyclic hysteretic responses.
System Concept
Thin steel web plates within a steel boundary frame dissipate energy in a steel plate shear wall system. The system acts by yielding under lateral seismic forces such that the yield is distributed and deformation is constant throughout in order to dissipate seismic energy.
Post- tensioned tendons were located at all beam to column connections in order to provide a further self-centering capacity to the building. In this system, the beam and column connections are bolted with a gap to allow for the system to rock under lateral loading conditions. When the system rocks, the post-tensioned tendons elongate, and due to the elastic qualities of the post-tensioning tendons, the system reverts to its original configuration after unloading.
Paired with the post- tensioned tendons, the steel plate shear wall system can dissipate seismic energy, while minimizing the residual damage after unloading. Due to the thin shear wall system, the SPSWs remain deformed after unloading, which, though energy was dissipated in the process and people remain safe, results in costly and time-consuming repairs after an earthquake. Due to the post-tensioning ability to remain elastic and self-center the system, the residual deformation of the combined SC-SPSW system is minimized, so repairs are less expensive and the return to occupancy can be done more efficiently.
Analytical Study, Results, and Discussion
At the University of Washington, large scale subassemblies of the steel plate shear wall system connected at the beam to column interface with post-tensioned tendons were fabricated in order to test the interactions between the two systems. The setup of each subassembly was a two story system featuring only the SPSW with PT tendons that was connected to the ground with pinned connections in order to allow for rocking and was loaded into an actuator at the top. The test specimens were loaded with quasi static cyclic loading according to the ATC-24 standard procedure, which calls for displacement-controlled cyclic loading, which was performed up to a 3% drift. The specimens featured the same boundary frame and PT strands, but the web plates had different thicknesses, and the PT strands were different in number and initial load. As web plate thickness increased, the strength and energy dissipation of the system increased as well. Likewise, as total PT cross sectional area, or number of PT strands, increased, the self-centering stiffness increased as well.
At the University of Buffalo, the completed test prior to the publication of this paper was a cyclic loading test on a one third scale test specimen featuring three stories using the SC-SPSW system along with infill plates and a boundary frame. The test setup consisted of an actuator on each floor and a displacement controlled loading of the system up to 4% drift. Load cells monitored the forces on each floor, and the behavior was modeled as a hysteretic response curve. Overall, the post-tensioned strands remained elastic with some loss of strength, and the system exhibited a flag sh
Reference
Clayton, P., Dowden, D. M., Winkley, T., Berman, J.W., Bruneau, M., and Lowes, L.N., (2012). “Experimental Investigation of Self- Centering Steel Plate Shear Walls,” Structures Congress 2012, pp. 1586-1597.