Peak and residual deformation-based seismic design for multi-story hybrid concentrically braced frames

Recently, using two and more types of braces in a concentrically braced frame (CBF) has been demonstrated to be effective for developing seismic resilient structures. The hybrid CBF with the combination of buckling-restrained braces (BRBs) and self-centering braces (SCBs) is promising to realize the desirable seismic performance. However, the seismic design method for the hybrid CBFs can rarely be found. To this end, the general behavior of the hybrid CBF is first introduced. Through nonlinear time history analysis (NLTHA) on single-degree-of-freedom (SDOF) systems, the seismic responses of the hybrid CBFs are investigated comprehensively. Based on the SDOF analytical results, a performance-based seismic design (PBSD) method is introduced to size the hybrid CBFs. The essential advantage of the PBSD method is that the peak and residual inter-story drift ratios can be jointly selected as the performance targets. A benchmark six-story CBF was selected as the example building to demonstrate the method. The system-level NLTHA under a suite of ground motion earthquakes was conducted to examine the accuracy of the method. The results indicated that the hybrid CBF designed by the PBSD method could well meet the prescribed performance targets, i.e., both the peak and residual inter-story drift ratios are well controlled within performance limits. Moreover, the optimal design hysteretic parameters are suggested to eliminate the residual inter-story drift ratios and minimize the peak floor accelerations.