Seismic Behaviors Of A Novel Type Of H-section Steel Buckling Restrained Braces

Buckling-restrained braces (BRBs) using concrete filled steel tube (CFST) as casing exhibited an excellent capacity to resist global and local buckling in previous researches. However, the steel core of this type of BRB needs to be wrapped with an unbonding layer to eliminate the bond stress between the steel core and concrete and to accommodate lateral expansion due to the Poisson's effect. This fabrication work is generally time-consuming and difficult to ensure member quality. All-steel BRBs, of which the casing consists of all-steel components without concrete or mortar, have the advantage of easier fabrication and assembly than the CFST BRBs. However, local buckling in the core plate is prone to occur for all-steel BRBs due to the absence of constraining effect provided by concrete or mortar. Based on the problems above, a novel type of H-section steel buckling-restrained braces (HBRB) with an H-section steel as the axial load-carrying member sandwiched by two U-shape steels and two face plates, is developed in this study. It is expected that buckling of web plate of H-section steel would be restricted by the flange, and vice versa; hence, the local stability of steel plate of H-section steel could be improved somewhat compared with that of the steel core with rectangular core plate or cruciform shape. This would help to delay local buckling of BRBs. In addition, HBRB can provide larger yield force and stiffness than BRBs with traditional core plate or cruciform cross-section as steel core, which make it promising in actual application.The seismic behavior and stability of the proposed HBRB are experimentally and numerically investigated in this study. The cyclic behavior and proper details of HBRB are first examined by component testing, followed by finite element analysis. Main contents and conclusions are presented as follows:1,Two HBRB specimens with different constructional details, labeled HBRB1 and HBRB2, were designed according to the current design theory in terms of global and local stability of HBRB and H-section steel. It shows that with the restraint provided by adjacent steel plate, the local stability of HBRB and H-section steel could be improved.2,The seismic behavior and stability of HBRB1 and HBRB2 were experimentally investigated under uniaxial quasi-static cyclic loading. The rib arrangement method of H-section steel is then proposed based on the test results.3,Numerical simulation and parametric study were performed on HBRBs by using the finite element software ABAQUS. The analytical results show that the bolt spacing has the most significant effect on the stability of HBRB. The local buckling failure mode of HBRB, which is generally caused by high-mode buckling of the constrained steel plate of H-section steel, would switch to another local buckling failure mode induced by high-mode buckling of the entire H-section steel.