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

Abstract

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.

Analysis of the seismic performances of structures reinforced by self-centering buckling-restrained braces

“…A BRB is composed of four elements: an inner steel core, which is the yielding element; a bond-preventing layer around the inner core; an outer steel casing (round or square); and grout infill, which provides stability to the inner core. Therefore, the steel inner core is fully braced within the steel outer casing and the grout, such that it can yield in tension and compression without buckling [28,29].…”

Investigation of the Causes of Soft-Storey and Weak-Storey Formations in Low- and Mid-Rise RC Buildings in Türkiye

“…Soft-storey formations lead to a significant increase in deformation demands and cause the load of energy dissipation to be placed on the columns in this storey. Buildings with soft ground floor concentrate large drift ratio demands on the first floor and low demands on the upper floors, resulting in severe damage to or the collapse of the building [46,[53][54][55]. Additionally, the presence of poor column-beam connections and weak columns are primary causes for the development of soft-storey mechanisms [50].…”