Research On Seismic Performance Of Reinforced Concrete Continuous Girder Bridge With Self-centering Friction Damper

Under the action of strong earthquake,the pier and bearing of traditional concrete continuous box girder bridge are prone to produce large displacement,and the function of bridge structure may be interrupted after the earthquake.In this paper,a new type of SMA self-centering friction damper is proposed to be attached to the concrete continuous box girder bridge,which can improve the seismic capacity and post-earthquake resilience of the structure.The finite element simulation analysis is carried out through the Open Sees platform to study the seismic performance of the continuous girder bridge structure with self-centering friction damper.The structural optimization algorithm of the continuous girder bridge with self-centering friction damper is developed by combining MATLAB and Open Sees.Finally,the incremental dynamic analysis and multi-dimensional seismic vulnerability of the structural system are completed.The main contents of this article are as follows:(1)Based on shape memory alloy(SMA)material and NAO friction material,a new type of composite damper is developed.Through special structure,the SMA rod can be always in tension during the tension and compression process of the damper.The experimental study on the mechanical properties of the new damper was further carried out.Based on the Open Sees finite element software,the secondary development of the SMA material constitutive model was completed,and the accuracy of the model was verified by comparing the experimental results.Taking a 4-span prestressed concrete continuous box girder bridge as the research object,a refined finite element model of the bridge structure with SMA dampers is established.The nonlinear time history analysis of the uncontrolled bridge structure and the self-centering damper bridge structure is carried out,and the obtained displacement response is compared and analyzed.The results show that the average seismic reduction rates of pier top displacement and bearing deformation under frequent earthquakes reach 82.6 % and 81.48 % respectively,and reach 48.02 % and 42.95 % under extremely rare earthquakes.The seismic reduction effect of the new damper is obvious,and the residual deformation of the controlled structure after the earthquake is smaller than that of the uncontrolled structure,which realizes the function recovery of the bridge structure.(2)The optimization design of self-centering friction damper parameters in continuous box girder bridge structure is completed.Aiming at the self-centering damper continuous beam bridge structure,the optimization algorithm of damper design parameters is developed by combining Matlab and Open Sees.Based on Matlab,the genetic algorithm is realized.Open Sees is used to carry out the time history analysis of continuous box girder bridge under rare earthquake to obtain the structural response.Taking the displacement of pier and the deformation of bearing as the optimization objectives,the damper parameters are optimized.Furthermore,the seismic time history analysis of the continuous beam bridge structure under the optimization scheme is carried out,and the seismic response of the uncontrolled structure,the trial algorithm design structure and the optimized design structure is compared and analyzed.The results show that the optimized controlled structure has a 3.75 % increase in the seismic reduction rate of the pier top displacement under the action of rare earthquakes compared with the controlled structure of the test algorithm,and the seismic reduction rate of the bearing deformation is increased by 2.14 %.The seismic reduction rate of the pier top displacement increased by 2.44 %,and the seismic reduction rate of the bearing deformation increased by 2.02 %.(3)The multi-dimensional seismic vulnerability analysis method based on the multi-dimensional limit state function completes the seismic performance evaluation of the functionally recoverable bridge structure.Three damage indexes of pier peak displacement,residual displacement and bearing peak deformation of continuous beam bridge are selected,and the incremental dynamic analysis of uncontrolled structure and optimized structure is carried out.The results show that the pier top displacement,residual displacement and bearing deformation of the optimized structure are smaller than those of the uncontrolled structure.Based on the multi-dimensional vulnerability analysis method,the contribution of the peak displacement and residual displacement of the pier to the final damage state of the pier is integrated,and the damping effect of the structural pier is quantitatively analyzed.Combined with the peak deformation of the bearing,the contribution of the three to the final damage state of the bridge system is quantitatively analyzed.The results show that the layout of the SMA self-centering damper can significantly reduce the probability of exceeding the limit state of the pier and the bridge system,and the damping effect is obvious.