Optimal placement of post-tensioned self-centering yielding braced systems for braced frame structures

The experience of past prominent earthquakes establishes the fact that the structure’s catastrophes and casualties can be dramatically decreased through the use of self-centering systems. A promising post-tensioned self-centering yielding braced system (PT-SCYBS) has been developed, comprising of two main components, including the post-tensioned wires, exhibiting the desirable self-centering properties, and steel bars, providing the energy dissipation capacity. The structural application of such systems is expeditiously expanding due to their capabilities of not only reducing the residual deformations of the structures but also improving the structure’s performance level. As such, identifying optimal design and proper placement of the proposed device in the structure is of crucial importance. In this paper, the mechanics of the proposed system, as well as a simple and efficient approach for determining the optimal design of the PT-SCYBS, have been proposed. Numerical models have been employed to examine the effect of various configurations of the device on the hysteretic behavior of the proposed PT-SCYBS. Nonlinear static and dynamic analyses are performed on the seismically deficient 3- and 9-story moment resisting frames (MRFs), enhanced with the optimal placement of the PT-SCYBS. Comparing the results of the PT-SCYBS buildings and MRFs, it can be concluded that the residual drift decreased by 96% and 77% for the 3- and 9-story buildings, respectively. As such, the optimal design of the proposed system in the building causes notably lower residual drifts as compared with the MRF buildings, resulting in enhanced seismic performance.