Experimental Studies On Seismic Performance Of Buckling-Restrained Braced Precast Concrete Frame

Precast Concrete(PC)frame structure is one of the most important structural forms of assembly architecture.It will be popularized in the future with its efficient and convenient and suitable for the characteristics of construction industrialization.However,due to assembly reasons,the overall seismic performance and ductility of precast concrete frame structure are relatively poor compared with cast-in-place concrete frame.Buckling restrained brace(BRB)is a kind of energy dissipation component with excellent properties.Under the action of earthquake,the support can act as the main component of the"first line of defense"to protect the beam and column.At the same time,the support can quickly enter the yield stage and dissipate the seismic energy.Buckling restrained brace is applied to the PC frame structure to improve the seismic performance of the PC frame.However,the existence of BRB's pull will have an additional impact on the poor tensile concrete,which may change the failure mode and force mechanism of the whole structure.In order to clarify the anti-seismic performance,failure mode,force mechanism of the BRB-PC frame and the effect of buckling support during the whole failure process,the detailed work of this paper is as follows:(1)The PC frame with 6 layers of BRB-PC frame is designed as the prototype,and a cross structure of the bottom layer is selected.A 1/2 scale BRB-PC frame model and a contrast specimen PC frame are made,and the pseudo static test is carried out.The results of fracture development,hysteretic curve,skeleton curve and failure mode were obtained.The test shows that under the same loading condition,the failure degree of PC frame beam and column is greater than that of BRB-PC frame.The ultimate bearing capacity of BRB-PC frame is 428.20kN and-400.21kN,PC frame is 336.35kN and-322.16kN,and the ultimate bearing capacity of BRB-PC frame is increased by 27.31%and 24.23%.(2)Compare the seismic performance of two frames,and analyze stiffness,energy dissipation and ductility.The results show that the stiffness of BRB-PC frame is much larger than that of PC frame before loading interlayer displacement angle 1/42.The ductility coefficient of the BRB-PC frame is 4.01 and the PC frame is 2.81;in terms of energy dissipation ratio and damping coefficient,the maximum values of the BRB-PC frame are 0.802 and 2.05 respectively,and the PC frame is 0.68 and 0.158,The analysis results show that all the seismic performance indexes of the BRB-PC framework are better than those of the PC framework.(3)The failure modes of the BRB-PC frame are analyzed according to the hinges order of the BRB-PC frame and the failure of concrete.The failure modes of the frame follow:the failure sequence of the buckling support to the beam and the column,which belongs to the failure mode of the supporting beam.According to the axial force variation of different stages of buckling support in the BRB-PC frame,the stress mechanism of the whole frame is analyzed.The maximum contribution of the support to the whole loading process is about 70%.(4)The energy consumption contribution ratio of buckling restrained brace in BRB-PC frame is analyzed,and the role of support in each stage of BRB-PC framework is studied.The total energy consumption ratio of the anti buckling support in the BRB-PC frame is about 50%.After the support enters the yield stage,the energy consumption ratio of the support is 65%.After that,the support will play different roles and energy for the whole frame with the increase of the loading displacement.