Experimental Investigation of Seismic Performance of Three-core buckling restrained braces

As a passive control system, braces have an effective role in creating structural resistance to lateral forces such as earthquakes and winds. One of the ways to make the braces more economical is to use their inelastic capacity. Ordinary braces perform well in tension; however they buckle under pressure and exhibit undesirable behavior. This problem can reduce dissipated energy due to lack of plasticity, which plays an important role in cyclic loading such as earthquakes. For this reason, buckling-restrained brace (BRB) have become increasingly popular in different countries. BRBs include yielding steel core and an outer steel hollow section. Although the yielding steel core has a low compressive capacity, its capacity in pressure can be increased by limiting its buckling due to the outer steel hollow section. So far BRBs introduced as mentioned have a single yielding core, however In this paper, in order to improve the seismic behavior of BRBs, buckling-restrained brace with three parallel cores with different yield stress have been suggested and introduced. The buckling braces were made in one and three steel core with the same tensile and compressive capacity. These braces were subjected to cyclic tensile and compressive loads in the laboratory under the ATC-24 loading protocol. Hysteresis cyclic performances of each brace were obtained and examined. The experimental results show that: 1) the hysteresis loop of the 3-core brace is thicker and higher than the 1-core brace, 2) indicating that the three core brace has 16.3% and 8.8% higher energy absorption and damping capacity, respectively compared to that of the single core brace. Furthermore, it has better seismic performance.