Development and experimental investigation of a post-tensioned self-centering yielding brace system

Abstract

This paper presents the results of an experimental study for a post-tensioned self-centering yielding brace system (PT-SCYBS). This newly designed bracing system is comprised of high-strength post-tensioned (PT) wires with highly ductile steel bars in parallel, providing an easy-to-construct supplemental device. A full-scale PT-SCYBS prototype was fabricated, and a set of PT-SCYBS specimens with different configurations are experimentally studied. The main objective of this paper is to examine the hysteretic response of the proposed PT-SCYBS by evaluating the effects of various parameters, including the number and diameter of PT wires and the diameter of steel bars, the post-tensioning ratio of PT wires, the loading protocol, and the loading rate. As confirmed by the experiments, the PT-SCYBS provides a repeatable flag-shaped hysteretic response with the self-centering capability, which would in turn, leads to a reduced residual displacement in this system. The experimental results show that increasing the post-tensioning ratio of the PT wires results in negligible residual displacements in the PT-SCYBSs. For the same post-tensioning ratio, when a specimen has a larger energy dissipation unit (i.e., a larger number of steel bars), it has a greater cumulative energy dissipation capacity and effective stiffness. Furthermore, the residual displacement of the PT-SCYBS can be controlled by changing the number and diameter of the PT wires and the steel bars' diameter. Finally, a nonlinear finite element baseline model is calibrated for the PT-SCYBS; and a good agreement has been observed between the experimental and numerical results.