Investigation On Seismic Performance Of Double-level Yielding Buckling-restrained Braced Concrete Frames

Buckling restrained brace(BRB) has been widely used in the field of energy dissipation as a metal energy dissipation component due to its advantages including plentiful hysteretic curve,stable energy dissipation capacity and good ductility.However,traditional BRBs remain elastic under frequent earthquakes.Consequently,traditional BRBs can only provide lateral stiffness for the structure,and cannot dissipate energy under frequent earthquakes.In order to overcome this shortage,the double-level yielding buckling-restrained brace(DYBRB)consisting of steel dampers and buckling restrained braces was proposed.The DYBRB can provide additional damping,lateral stiffness and energy dissipation capacity under frequent earthquakes.The DYBRB is expected to exhibit better seismic performance by provding energy dissipation capacity under frequent earthquakes,comparing to traditional BRBs.In this paper,the DYBRBs were adopted in concrete frame based on an actual project.The DYBRBs were adopted to reduce the story drift ratio and protect the main frame.The seismic performance of the double-level yielding buckling-restrained braced concrete frame(DYBRBCF)and the single-level yielding buckling-restrained braced concrete frame(SYBRBCF)was compared via cyclic loading test and finite element analysis.The main research contents are as follows:(1)Two specimens including a SYBRBCF and a DYBRBCF were tested under cyclic load.The coordination performance between the DYBRB and the concrete frame was demonstrated.The seismic performance of the SYBRBCF and DYBRBCF was compared in terms of failure mode,hysteretic curve,skeleton curve,energy dissipation coefficient.The results indicate that the DYBRBCF has the better seismic performance including the higher lateral stiffness,the better ductility and energy dissipation capacity.Furthermore,the DYBRB can better protect the main frame than the traditional SYBRB.(2)The finite element models of the SYBRBCF and DYBRBCF were established to compare the seismic performance of the two types of structures.The story drift ratio,the story shear force,the sequence of plastic hinge,the hysteretic curve and the additional damping ratio were analyzed and compared in detail.The results indicate that the DYBRB exhibit excellent hysteretic behavior under frequent and rare earthquakes.In addition,it can provide additional damping and improve the lateral stiffness under frequent earthquakes.Moreover,it can better protect the concrete frame and provide better energy dissipation capacity under rare earthquakes than the traditional SYBRB.(3)Finally,performance-based seismic design method and procedure of the DYBRBCF were estiblished and the crucial design criteria of the DYBRB were proposed.