Research On Seismic Behavior And Optimal Layout Of The Braces Of A High-rise Frame Structure Strengthened By BRB

As a kind of displacement-based damper,Buckling-Restrained Brace(BRB)can provide effective lateral stiffness for the main structure under frequent earthquake,yield and consume energy firstly under fortification earthquake and rare earthquake,and reduce seismic response of main structure,and has a wide application prospect in the seismic reinforcement of high-rise frame structures.The lateral stiffness ratio k between brace and frame,as one of the main design parameters of BRB reinforcement,has a significant impact on the overall seismic performance of the structure.The inter-layer deformation of the upper layer of the high-rise frame structure designed based on the lateral stiffness ratio is small,which will lead to insufficient energy dissipation and waste of performance of BRB in the upper layer of the structure.Therefore,how to reasonably layout and design BRB can effectively improve the utilization rate of braces,ensure that the structure can achieve the expected performance goal and reduce property loss under earthquake,which has significant engineering significance.This paper takes the high-rise frame structure of a hospital inpatient building under the background of increasing seismic fortification intensity in Tianjin as the research object.The research contents and conclusions are as follows:1.Through the response spectrum analysis of the structure under 8 degree(0.20g)frequent earthquake,it is show that the structure belongs to out-of-code high-rise structure,which has transfinite conditions such as height transfinite and irregular torsion,,and can not meet the seismic fortification requirements of the current specification,so seismic reinforcement is required.The paper formulates seismic performance target that meets the requirements of the specifications and the actual situation of the project.2.The dynamic time history analysis of the structural reinforcement scheme with separate BRB and separate ordinary steel braces is carried out,and the finite element comparative analysis of BRB members and ordinary steel braced members with different braced lengths is carried out,which the results show that the structures with different brace types effectively improve the torsional stiffness and lateral stiffness;Under Fortification earthquake and rare earthquake,the energy dissipation effect of the structure with BRB is obvious,and the seismic performance is obviously better than that of the structure with ordinary steel braces;Compared with ordinary steel braced members,BRB members play a more excellent energy dissipation capacity,which verifies the performance advantages of BRB compared with ordinary steel braced members.3.For study the influence of different BRB layout on the seismic performance of out-of-code high-rise frame structure and determine the reasonable BRB layout suitable for the engineering,damping structural models with different lateral stiffness ratio,different BRB layout plan and different BRB layout mode are designed respectively.The dynamic time history analysis shows that,When the lateral stiffness is relatively small,the BRB energy dissipation of each floor is more sufficient,but the improvement of the overall seismic performance of the structure is limited;When the lateral stiffness is relatively large,the utilization rate of BRB will be low,resulting in performance waste;BRB arranged in the side span of the structure is conducive to reduce the torsional effect of the structure,and part of BRB arranged in the center span is conducive to improve the energy dissipation capacity of BRB;Compared with V-shaped brace layout,herringbone brace layout has more advantages in improving inter-story displacement angle,inter-story shear,elastic-plastic energy consumption and performance damage.4.For solve the performance waste of the upper braces of high-rise frame structure designed with fixed lateral stiffness ratio,based on the design method of variable lateral stiffness ratio and the layout of hybrid brace,three reinforcement schemes with the optimal layout of braces are proposed.The reinforcement effects of different schemes are comprehensively evaluated through dynamic time history analysis.The results show that the reinforcement scheme designed with variable lateral stiffness ratio and the and reinforcement scheme of hybrid steel braces can effectively improve the utilization rate of braces,give full play to the performance of BRB and meet the expected performance targets.AND,the reinforcement scheme of hybrid steel braces can further reduce the amount of BRB and play a more excellent economic benefits,so it is determined as the best reinforcement scheme.