High-mode buckling responses of buckling-restrained brace core plates An-Chien Wu 1 , Pao-Chun Lin 1 and Keh-Chyuan Tsai 2, * 1 National Center for Research on Earthquake Engineering, Taipei, Taiwan 2 Department of Civil Engineering, National Taiwan University, Taipei, Taiwan SUMMARY Cyclic loading tests and finite element analyses on six novel all-steel buckling-restrained braces (BRBs) are conducted using different loading patterns to investigate the core plate high-mode buckling phenomenon. The proposed BRB is composed of a core member and a pair of identical restraining members, which restrains the core member by using bolted shim spacers. The design of the proposed BRB allows the core plate to be visually inspected immediately following a major earthquake. If necessary, the pair of restraining members can be conveniently disassembled, and the damaged core plate can be replaced. Test results indicate that the proposed BRBs can sustain large cyclic strain reversals and cumulative plastic deformations in excess of 400 times the yield strain. Experimental and analytical results confirm that the high-mode buckling wavelength is related to the core plate thickness and the applied loading patterns. The larger the axial compressive strain is applied, the shorter the high-mode buckling wavelength would be developed. The buckling wavelength is about 12 times the core plate thickness when the high-mode buckling shape is fully developed. However, it reduces to about 10 times the core plate thickness when a compressive core strain reaches greater than 0.03. The high-mode bucking wavelength can be satisfactorily predicted using the proposed method or from the finite element analysis. Copyright © 2013 John Wiley & Sons, Ltd. Received 30 January 2013; Revised 30 June 2013; Accepted 1 July 2013 KEY WORDS: buckling-restrained brace; buckling restrainer; high-mode buckling; buckling wavelength; cyclic loading test; finite element analysis 1. INTRODUCTION Unlike the buckling braces, buckling-restrained braces (BRBs) can be designed and fabricated to sustain yielding in both tension and compression [1–4]. Therefore, BRBs have been increasingly adopted as hysteretic dampers to improve the earthquake resisting performance of building and bridge structures [2, 5–7]. The core member of a typical BRB is usually encased in the buckling restrainer so that the failure of the core member may not be easily detected following an earthquake. Strong aftershocks could occur following the main shocks. In order to guarantee effective seismic performance of the buckling-restrained braced frames, which are required to sustain multiple earthquakes and aftershocks during the service life, developing the techniques for inspecting the BRBs is warranted. Previous researchers have based on such concepts for BRBs in which the restrainers could be disassembled first for inspection of the core member [8–11]. After the inspection, however, the restrainers might be difficult to be reintegrated with the core member where large plastic deformations could have taken place. Thus, immediately after a major earthquake, it would be desirable if the condition of the core plate could be visually inspected first without disassembling any part of the BRBs. *Correspondence to: Keh-Chyuan Tsai, Department of Civil Engineering, National Taiwan University, Taipei, Taiwan. † E-mail: kctsai@ntu.edu.tw Copyright © 2013 John Wiley & Sons, Ltd. EARTHQUAKE ENGINEERING & STRUCTURAL DYNAMICS Earthquake Engng Struct. Dyn. 2014; 43:375–393 Published online 8 August 2013 in Wiley Online Library (wileyonlinelibrary.com). DOI: 10.1002/eqe.2349