Hysteretic Behavior And Design Methods For Self-Centering Buckling-Restrained Brace Coaxially Assembled In Disc Springs

Self-centering buckling-restrained brace(SCBRB)lets self-centering system(SC)and buckling-restrained brace(BRB)work in parallel to decrease residual displacement of yielding of BRBs,and the SCBRBs can be used to improve the repairability of structures.Disc spring is a kind of self-centering material with stable performance and economical efficiency.However,the existing SCBRBs with disc springs have complicated configurations,unsymmetrical stiffness between tension and compression sides,short yielding segment of BRB,etc.Therefore,a new type of self-centering steel brace assembled by disc springs and buckling-restrained brace coaxially,in which the restoring force is provided by the single string disc springs with precompression,was proposed in this dissertation.Quasi-static tests and numerical simulation were carried out to investigate the seismic performance of SCBRBs.The main research contents are as follows:(1)New constructional details of the coaxial assembled self-centering buckling-restrained brace with disc springs(SCBRB)are proposed.The assembled pure steel BRB is placed in the hole of disc springs and hence the inner space of disc spring is reasonably utilized.The configuration of SCBRB is greatly simplified,the length of yielding part of BRB is increased and the stiffness difference between the tension side and compression side is greatly reduced.The ideal load-displacement curves of SCBRB were obtained by composition of the simplified bi-linear models of both bucklingrestrained brace and the self-centering system.Based on the ideal curves,the mechanism of the SCBRB in each working stage was analyzed.Both configuration and manufacturing process of SCBRB were described in detail.(2)Quasi-static tests were carried out to investigate hysteretic behavior and self-centering capacity of two braces with only self-centering system,one buckling-restrained brace and two self-centering buckling-restrained braces.The test results show that the SCBRBs have obvious flag-shape hysteretic curves,and the residual deformation of the SCBRBs is greatly reduced compared with the BRB.At the same time,axial stiffness of self-centering system can be flexibly adjusted by changing the configuration of the high strength studs.Based on the independence and stability of working behavior of the components of SCBRB,the bearing capacity of SC and BRB parts was separated,and it was found that the axial resistance of each SCBRB is mainly provided by the SC and energy dissipation capacity of each SCBRB is mainly provided by the BRB part.Besides,interaction of steel tubes in the SC can also provide some energy dissipation capacity.(3)The finite element analysis models of the specimens were established by ABAQUS software and their rationality is verified according to the test results.Hence,full-scale SCBRB models were established to explore the effects of constructional details,including the size and initial preload of disc springs,the cross-section area,the length of yielding segment and yield stress of steel plate brace in the BRB parts,the cross-section area and configuration of high strength studs,the thickness of steel controlling tubes,etc.,on both hysteretic behavior and self-centering performance of the SCBRBs.The formulas to reflect the relationship between the self-centering ratio and the residual deformation of different SCBRBs under horizontal drift levels of 2%,2.5%and 3.3% were provided.By considering both reduction of residual deformation and energy dissipation capacity of SCBRBs,reasonable ranges of self-centering ratios were given.In addition,based on test and analysis results,the actual hysteretic model of SCs was acquired by taking into account the bending action and friction effect of steel tubes in the SCs.