Study On Seismic Performance Of Bridges With New Type Of Block

Past seismic damage to bridges has revealed that traditional concrete shear keys are ineffective in limiting the sliding of beams during earthquakes,leading to widespread damage in small and medium-span bridges both domestically and internationally.Additionally,repairing traditional concrete shear keys is challenging,impeding the restoration of bridge functionality.The predicament of being both "unrestrained" and "difficult to repair" has long been an unresolved issue.In light of this,this study proposes a novel replaceable modular limit restrainer that integrates the functions of "limitation," "energy dissipation," and "replaceability," offering a potential solution to this problem.To validate the seismic effectiveness of the new retainer,small and medium-span bridges utilizing the new retainer are chosen as the research subject.Through vibration table testing and finite element simulation,this study explores the variations in dynamic response and methods for enhancing the seismic performance of small and medium-span bridges using the new retainer under seismic actions.The main research tasks of this study are as follows:(1)Following the theory of structural dynamic testing similarity,a 1:20 scaled simply supported beam bridge model is designed and fabricated for seismic simulation on a shaking table.Initially,based on practical considerations,a comprehensive material selection process is conducted,including reinforced concrete,steel,and organic glass.Organic glass is chosen as the material for constructing the model bridge.Subsequently,employing dimensional analysis and considering the engineering background,the design of the model bridge and its related components are optimized.The issue of insufficient structural mass is addressed through the addition of mass blocks.Finally,based on the completed model bridge,the data acquisition plan and seismic wave loading scheme for the vibration table test are determined,and the seismic simulation on the shaking table is carried out.(2)Utilizing the fundamental principles of structural dynamics,the data collected from the seismic simulation on the shaking table is comprehensively analyzed,and the response results of key parameters in the experimental model bridge are extracted.By combining the experimental observations,this study investigates the effects of different restraint conditions and support parameters on the dynamic response of the experimental model bridge,exploring the correlation and patterns between various sensitive parameters and the variation in seismic performance.(3)Building upon the theory of frictional sliding isolation,a finite element model of a two-span simply supported beam bridge is established using ANSYS.The model considers the sliding energy dissipation of plate-type rubber bearings.The model bridge is subjected to seismic dynamic loading under two scenarios: with the utilization of the new retainer and without it.By comparing the results of the finite element simulation with the shaking table test results,this study examines the influence of seismic spectrum characteristics,seismic input intensity,adoption of the new retainer,and support friction factors on the seismic dynamic response of the model bridge.It also investigates the seismic performance of small and medium-span beam bridges utilizing the new retainer and the working mechanism of the new retainer on the bridge.(4)Based on previous research,a representative small and medium-span beam bridge in Southwest China is selected.A finite element model is created using Midas/Civil,and engineering application analysis is conducted.The installation of the new retainer on the bridge is completed on-site.By comparing the seismic structural response results of the bridge with the new retainer and traditional concrete shear keys under different seismic design intensities,this study analyzes and explores the patterns of variation in the seismic performance of the bridge using the new retainer.