| Buckling restrained Brace(BRB)is an effective seismic energy-consuming component with the advantages of equivalent tensile and compression performance,full and stable hysteresis curve,and excellent energy dissipation performance.In order to solve the problems of excessive deformation of the steel frame and the difficulty of replacement of the brace due to the large inter-layer displacement angle of the structure when the buckling-constrained brace steel frame is subjected to rare earthquakes,this paper proposes a foundation without changing the basic composition of the bucklingconstrained brace member.In the above,the short-yield buckling restraint brace(SCBRB),which reduces the length of the yield zone in the buckling restraint brace core plate.Through finite element simulation,the hysteretic behavior and cumulative plastic deformation performance of SC-BRB are analyzed.Through theoretical analysis,the calculation formula of the minimum yield length of BRB under certain conditions is obtained,and the design method of SC-BRB is proposed.The main research contents are as follows:(1)Based on the performance characteristics of traditional buckling restrained braces,an SC-BRB is proposed to reduce the yield length while maintaining the total length.SAP2000 time-history analysis confirms that SC-BRB can improve the overall stiffness of the structure and reduce the residual interlayer.Displacement angle and residual deformation,while maintaining a certain energy consumption capacity and ductility;(2)Use ABAQUS finite element to simulate the analysis of BRBs with different yield lengths,and study the effects of concentration factor α on the hysteresis performance,stiffness degradation,energy dissipation capacity and cumulative plasticity of BRBs.The analysis results show that the SC-BRB hysteresis curve is full.When α ≤ 0.3,the hysteresis curve degrades when the strain is 5%.The concentration factor is inversely proportional to the brace stiffness and proportional to the yield displacement.The yield load is basically the same.Reducing the length of the yield section can also basically meet the requirements of energy consumption capacity and cumulative plastic deformation capacity.(3)After the length of the BRB yield section becomes shorter,the plastic deformation is greater,which reduces the low-cycle fatigue capacity of the brace.This paper analyzes the key parameters(width-to-thickness ratio,outer constraint length,and friction coefficient)that affect its low-cycle fatigue capacity: the larger the α,the smaller the width-to-thickness limit;when α < 0.4,the outer constraint length should be greater than 40%;The smaller the α,the greater the squeezing force between the inner core and the external constraint.The friction coefficient should be minimized to avoid overall and local instability,It is recommended that the minimum friction coefficient of the buckling restraint support with a concentration factor in the range of 0.2 to 0.4 is 0.1.(4)In order to accurately predict the fatigue life of the BRB,the minimum value of the yield section length is obtained.Based on the fatigue formula and the Miner linear criterion,the minimum deformation section length calculation formula under the prescribed loading system is obtained by the cumulative deformation method,and the finite element method is used.Analyze and verify accuracy.(5)Based on the results of SC-BRB finite element analysis,the bearing capacity,stiffness,and size of its core and external constraints are designed,and a design suggestion suitable for SC-BRB is proposed. |
