Research On Damping Performance Of Buckling-restrained Braces With End Strengthened H-shaped Core

As the traditional brace of frame structure system to resist lateral force during the earthquake,it's easy to buckling instability under compression,this is not conducive to the structure to resist earthquake.In order to improve the stress state of the traditional brace,and it does not appear buckling instability under compression,foreign scholars put forward a new type of brace — buckling-restrained braces.On the basis of existing research,based on the theoretical analysis of the strength and stability of the unconstrained segment of the buckling-restrained brace,this article put forward using the double channel steel to strengthen the H-shaped Core of buckling-restrained braces with end,Study on the hysteretic behavior and bearing capacity of buckling-restrained braces with strengthen end and the damping performance of the braced frame.To this end,the paper analyzes the following aspects.(1)The 15 buckling-restrained braces of Q235 Material Core are designed,and use ABAQUS software to build models,to analysis the influence of hysteretic energy dissipation and bearing capacity of with different unconstrained length buckling-restrained braces or by the different length and thickness channel to strengthen the Core of buckling-restrained braces.The analysis shows that the effect of energy dissipation is more obvious when the unconstrained length section is equal to the maximum shape variable under the action of axial force;The unconstrained section is strengthened by double channel steel,which can eliminate the buckling failure of the unconstrained section;When the channel length is 2 times of the unconstrained length section,the structures have better hysteretic energy dissipation capacity and bearing capacity;The thickness of the strengthen channel should not be too large,it is 0.4 to 0.8 times of the flange and web thickness of the H-shaped Core.The results of the above parameters are based,the paper selects 3 buckling-restrained braces with Q100LY(low yield point steel)Core for finite element analysis,to further validates the analysis conclusion.(2)By adding the buckling-restrained braces to a frame structure,based on the code for seismic design of buildings(GB5001-2010),the additional damping ratio of the brace structure is further deduced.Through the engineering design software PKPM to build the braced structure model and calculate it,and the effective damping ratio of braced frame structure is calculated by iteration method.Calculation results show: the inner core are two kinds of Q100 LY and Q235 steel's buckling-restrained braces,the inner core is Q100 LY steel's buckling-restrained brace that can provide more the additional damping for the structure under the frequently occurred earthquake and fortification earthquake,however,the inner core is Q235 steel's buckling-restrained brace that can provide more the additional damping for the structure under therarely occurred earthquake.(3)Using finite element analysis software SAP2000,the 4 frame structures of the paper are analysed by mode-superposition response spectrum method and time history analysis method,In this paper,the earthquake responses of four structural systems are compared under the frequently occurred earthquake ? fortification earthquake and therarely occurred earthquake,such as the period,inter story displacement,top displacement,top acceleration,base shear force and axial force of brace.Analysis shows:it is possible to improve the stiffness distribution of the structure in the frame structure and make it more uniform by adding the buckling-restrained brace,thus,the horizontal torsional coupling effect and the cycle ratio are reduced;however,the advantage of energy dissipation of buckling-restrained brace is not obvious under the small earthquake,the hysteretic energy dissipation effect of buckling-restrained brace is obvious under the moderate and rarely expected earthquake,which is beyond the ordinary brace.(4)This paper makes a comparative evaluation on the damping performance of buckling-restrained braced frame with the inner core of Q100 LY and Q235 steel.Analysis shows: through the response spectrum method,the damping effect of the buckling-restrained braced frame with the inner core of Q100 LY is more obvious;The damping performance of the buckling-restrained braced frame with inner core Q100 LY is better than that of the buckling restrained-braced frame with inner core of Q235 under the frequently occurred earthquake and fortification earthquake;However,the damping performance of the buckling-restrained braced frame with inner core Q235 is more obvious under therarely occurred earthquake.