Effect Of Processing Technique On The Performance Of Buckling-Restrained Brace

Buckling-restrained brace(BRB)is a kind of energy dissipating and damping device with advantages of excellent hysteretic performance,low manufacturing cost and easy fabrication,has been applied in all kinds of structures.But as its need to withstand high strain reciprocating load in the earthquake,it is more sensitive to the defects of welding,cutting and other other machining processes.In this paper,first of all,the cutting process of buckling restrained brace is studied,and the influence of several cutting process on the performance of buckling restrained brace is compared.After that,in order to evaluate the low cycle fatigue damage of buckling restrained brace,a UMAT material subroutine is developed by using ABAQUS secondary development function and be compared with the experiment results.Finally,the theoretical derivation is carried out on the most common initial defects in the production and processing of buckling restrained braces,which are residual stress and initial bending,the influence of initial imperfections on the low cycle fatigue behavior of the buckling restrained braces is also analyzed by using the cumulative damage subroutine.The main contents of this paper are as follows:(1)By means of metallographic analysis,hardness test,uniaxial tension test,low cycle fatigue test,the influence of plasma cutting,water cutting,wire cutting and flame cutting process on the performance of buckling restrained brace was analyzed.The results show that although the specimen of plasma cutting has heat affected zone with higher hardness in the vicinity of the kerf,but still has a better low cycle fatigue performance,and in several commonly used process of cutting plasma cutting in processing cost and efficiency have certain advantages,so it is appropriate for the production of BRB.(2)Two damage accumulation subroutine based on plastic strain is developed and be applied in the low cycle fatigue analysis of BRB,and the results are compared with experimental results,predict failure position of two models are consistent with the experiment,The damage development of the nonlinear cumulative damage model is in good agreement with the damage development trend of the test members.The results show that the cumulative damage material subroutine can be used to analyze the low cycle fatigue cumulative damage of buckling restrained brace,and can be used in buckling restrained brace with various forms and materials.(3)The effects of initial bending and residual stress on the overall stability,local stability and low cycle fatigue behavior of the buckling restrained braces are discussed.Initial bending has an adverse effect on the overall stability and local stability of BRB,the stiffness requirement of the external constraint component is improved.but when the external constraint is sufficient,the low cycle fatigue performance of the buckling restrained braces is at least not affected.The residual stress has a negative effect on the local stability of buckling restrained brace,and leads to the decrease of the initial yield load,but has no significant effect on the overall stability and low cycle fatigue behavior of the buckling restrained braces.