Seismic performance analysis of BRBs and gussets in a full‐scale 2‐story BRB‐RCF specimen

Abstract

Summary The implementation of buckling‐restrained braces (BRBs) for new reinforced concrete frame (RCF) constructions is limited. This study investigates the seismic forces and stability in the BRBs and gussets of a 2‐story full‐scale RCF specimen by using Abaqus models and a newly proposed stability evaluation method. The hybrid and cyclic loading test results are accurately predicted by the Abaqus analyses. Existing methods for computing the gusset interface forces for steel buildings from both the brace and the frame actions are compared with the Abaqus results. The applicability of these methods for the BRB‐RCF design is critically evaluated. It is confirmed that the Parallel‐2 method is suitable for estimating the BRB force demand imposed on the corner gusset and the generalized uniform force method is good for the corner gusset at the base. In addition, existing stability evaluation methods for BRBs and gussets are applied to investigate the out‐of‐plane (OOP) buckling of the first‐story BRB observed at the end of tests. The proposed stability model incorporates the BRB restrainer's flexural effects and 4 rotational springs in assessing the BRB's buckling. This model confirms that the BRB and the gusset's OOP buckling limit states could be coupled and must be evaluated together. By incorporating the flexural effects of the steel casing and the infilled grout, the proposed model satisfactorily predicts the OOP buckling of the first‐story BRB and gussets. These research results can be used for the implementation of BRBs in new RC frame constructions.

Data supporting the development of loading protocols for seismic qualification of BRBs considering global performance requirements

“…To this end, the study relied on publicly available data from past experimental tests on BRBFs conducted at a full-scale and large-scale. A total of 12 relevant experimental campaigns, published between 2004 and 2018 [[2], [3], [4], [5], [6], [7], [8], [9], [10], [11], [12], [13], [14], [15], [16], [17], [18], [19], [20], [21], [22], [23]], were compiled to investigate the values that the YLR take in very detailed BRBF specimens. Table 1 summarizes the information regarding the 12 experimental studies.…”

“…[22], Tsai et al. [23]One-bay, two-story new reinforced concrete (RC) frame with BRBs, with diagonal bracing configuration2-story 1-bay BRB-RC frameFull-scaleHybrid test + Cyclic loading testWelded3473, 35866025, 59800.58, 0.60…”

Seismic design and pseudo-dynamic tests of blind-bolted CFT frames with buckling-restrained braces

“…where actions can be respectively obtained by using the generalized uniform force method [43] and the improved equivalent strut model [30]. In addition, it should be noted that the extra moment, Mub, resulting from regular shape of gusset plates should be taken into account to check the weld size on the gusset-to-beam interfaces [31].…”

“…On the other hand, it should be noted that the connection between BRBs and boundary members is of crucial importance due to the fact that axial tension and compression of the BRB need to be effectively delivered to frames through gusset plates to resist earthquake action. Previous system-level experiments [11,30,31] have shown that gusset plates were subjected not only to BRB axial force, but also to frame action resulting from opening and closing of beam-to-column joint. This behavior was found to cause that gusset plates became more susceptible to weld fracture near the gusset tips or buckling deformation prior to failure of the BRBs, thus impairing the seismic performance of the dual system.…”

Evidence collected for peer review of buckling-restrained braced frames in New Zealand

“…Global stability is another main consideration when examining BRBF behaviour. Evidence following the 2011 Tōhoku Earthquake [11] and from several full frame tests have shown BRBFs to perform well [12][13][14][15][16][17]. However, the complexity of BRB behaviour makes it difficult to verify frame stability for all configurations and sizes.…”