Study of buckling-restrained braces with concrete infilled GFRP tubes

Abstract

In the proposed buckling-restrained brace (BRB), a concrete infilled glass-fibre reinforced polymer (GFRP) tube is used instead of a conventional concrete infilled steel tube to restrict steel inner core buckling. It has the following advantages: 1) The GFRP is a high-strength and flexible material available for structural components; 2) Its use as an outer constraint material is also a solution for poor corrosion resistance of the outer steel tube; In this study, 11 BRB specimens with concrete infilled GFRP tubes and 3 BRB specimens with concrete infilled steel tubes were designed to investigate the effects of the types of GFRP and constraint ratios on the hysteretic behaviour of the GFRP tube BRBs. The performance of the GFRP tube BRBs was also compared to the steel tube BRBs composed of three different lengths of steel tubes with the same wall thickness. All the GFRP tube BRB specimens had the same rectangular steel inner core and included two types of GFRP tubes with three different lengths and thicknesses. The medium- and long-length filaments winding GFRP tube BRB specimens buckled at the last stage of the test, while global buckling developed the cracks in the middle of the GFRP tube. All other BRB specimens didn’t buckle and underwent the complete loading process without degradation in stiffness and strength. The finite element models of BRBs were built using ABAQUS, considering the constitutive models of the GFRP, steel and concrete subjected to cyclic loading. The finite element model of the GFRP tube BRBs could simulate the performance of the BRBs well, and the results of analysis were calibrated with experimental results. All the BRB specimens exhibited good hysteretic behaviour, sufficient load-bearing capacity, large ductility and energy dissipation capacity. The GFRP tube BRBs may share the same design criteria as the traditional steel tube BRB by limiting their constraint ratios, and the GFRP tube may be used as an alternative to the traditional outer restraining tube especially for those BRBs with strict durability requirement.