Study On The Anti-buckling Support And Seismic Performance Of Continuous Beam Arch Bridges

As a crucial component of transportation infrastructure,bridges can cause significant economic losses and casualties when damaged by earthquakes.To improve the seismic performance of bridge structures,scholars have introduced the concepts of damping and isolation into bridge design and developed various damping and isolation devices,such as damping bearings,viscous dampers,and metallic dampers.Compared to the first two commonly used devices,metallic dampers have significant advantages in simple construction,convenient installation and replacement,and better economy.However,their application in long-span bridges is currently limited,making further research necessary.This article studies the damping and isolation effects of buckling-restrained braces(BRB),a commonly used metallic damper in the construction field,on a(90+180+90)m continuous beam arch bridge.Using Midas/civil software to establish a finite element model for nonlinear time-history analysis,the study investigates the damping and isolation performance of BRBs with different arrangements under three different earthquake waves,and uses constrained nonlinear optimization algorithms to optimize parameters such as yield bearing capacity and yield displacement.Finally,based on the results of the optimization analysis,the damping and isolation effects of BRBs and viscous dampers are compared.The research results show that:(1)Comparing and analyzing the damping and isolation effects of the longitudinally and transversely arranged "V"-shaped and "human"-shaped patterns,the longitudinal damping effect of the "V"-shaped pattern is significantly better than that of the "human"-shaped pattern,with the maximum difference in key node displacement damping rate reaching 16%and the maximum difference in pier bottom longitudinal moment damping rate reaching 27%.However,the different transverse arrangement patterns have little effect on the transverse damping effect of the bridge,with differences in key node displacement damping rate and pier bottom moment damping rate being less than 5%.(2)Optimizing the yield bearing capacity and yield displacement of the BRBs shows that as the yield bearing capacity increases and the yield displacement decreases,the displacement of all key nodes except for the arch top transverse displacement decreases,while the variation trend of the pier bottom moment is just the opposite.When the yield bearing capacities of the edge and middle piers under rarely encountered earthquake excitations are 3000 kN and 6000 kN,respectively,and the yield displacement is 5 mm,although the relative longitudinal displacement between the pier and the beam decreases by 64.61%compared with the nondamping situation,the longitudinal bottom moments of the edge and middle piers increase by 35.99%and 51.62%,respectively.(3)Based on the principle of selecting parameters to control the displacement of key nodes as much as possible without increasing the bottom moment of the pier,a constrained nonlinear optimization algorithm is used to optimize the parameters of the buckling-restrained braces with the relative displacement of the pier-beam as the objective function and the sum of the pier bottom moments as the constraint condition under various seismic excitations,and the optimal parameter values for the transverse and longitudinal BRBs are obtained.(4)The comparative analysis of the damping effects of BRBs and viscous dampers shows that under three different earthquake excitations,the responses of both structures to key node displacement,pier bottom moment,and hysteresis energy dissipation capacity are basically the same,with differences in peak displacement damping rate of key nodes being only between 2%and 12%,and differences in pier bottom moment damping rate being between 3%and 8%.The hysteresis energy dissipation of viscous dampers is only increased by 5.56%compared to that of BRBs,which indicates that the damping and energy dissipation capacities of the two dampers are basically the same under earthquake excitations.Moreover,BRBs have significant advantages in simple construction,convenient installation and replacement,and better economy compared to viscous dampers,which also confirms the feasibility of using BRBs as damping and isolation components in the continuous beam arch bridge damping system.