Hybrid Simulation Tests of a Soft Storey Frame Building Upgraded with a Buckling-Restrained Brace (BRB)

Hybrid simulation (HS) is an experimental technique possessing advantages over other testing methods and, in several cases, it is the only available method to test structural systems with reliability. In this paper, HS is used to assess the effects of upgrading a soft-storey frame building using a Buckling-Restrained Brace (BRB). This topic is of paramount significance in seismic regions like Mexico, where more than 40 structures collapsed and thousands resulted with different levels of damage during the September 19, 2017 Mw 7.1 Earthquake. Unfortunately, one of the still-remaining challenges in many seismic countries is the use of seismic protective technologies (SPT) that help to mitigate damages in structures. With the aim of encouraging the use of SPT, this paper presents the results of an experimental program that shows the effectivity of buckling-restrained braces (BRBs) to improve safety and reduce damages in structures with one of the most typical causes of failure, i.e. the soft storey problem. A reinforced concrete five-storey frame building was selected first. Then, a numerical 2D model of the structure was subjected to nonlinear dynamic analyses using several earthquake ground motions. In many analyses, collapse was observed in the structure model. After that, the model was upgraded by introducing a BRB in the soft storey. HS was used to assess the performance of the upgraded structure under severe earthquake action. While the frame building was modelled numerically, the BRB was tested physically. The tests were repeated using a conventional brace instead of the BRB. The results show that introducing the BRB in the soft storey was an effective measure to improve the structure performance under seismic loading; while the disadvantages of the conventional brace were exposed.