Design and Seismic Performance of Tied Braced Frames

Abstract

In this work, a tied braced frame (TBF) was developed to achieve uniform inelastic deformation in an eccentrically braced frame (EBF) by connecting links across the entire frame height with tie members. Herein, a TBF design method is proposed, considering a new lateral force distribution pattern. To better evaluate the seismic performance, and verify the design advantages of the TBF, nonlinear time-history analysis and fragility analysis were conducted using 6-, 10-, and 20-story TBF models designed using this method, as well as EBF models for comparison. It was found that the maximum inter-story displacement angles of the TBF model were reduced by 10%, 3.3% and 6.3% at the 84th percentile at 6, 10 and 20 stories, respectively, and the DCF values were also reduced by about 5.5%, indicating that the design of the TBF structure is more reasonable. The results revealed that the TBF models featured more uniform distributions of the normalized link shear forces and inter-story drift ratios, resulting in a better damage distribution and more ductile behavior. Furthermore, under earthquakes, the tie axial forces were similar to those calculated using the design equation, thereby indicating the reliability of the design method. Under the same seismic conditions, the PGA values of the TBF structure are about 10~15% lower at 50% exceedance probability compared to the EBF structure; the CMR values of the 6-story, 10-story, and 20-story models are 1.12, 1.09, and 1.06 times higher than those of the EBF structure, respectively. Notably, based on a comparison of the exceedance probability from the fragility analysis results for the TBF and EBF models, the TBF model exhibited better anti-collapse performance.