Seismic Reliability Analysis Of Long-Span Continuous Girder Bridge With Railway Isolation Considering PSSI

Long-span continuous girder bridges are an important and often used bridge form.How to ensure its seismic performance and reasonable safety has always been an important subject that domestic and foreign scholars are concerned about.Over the past decades,the seismic research of the bridge has achieved great results.However,due to the diversity and complexity of seismic problems,many problems need further studied and discussed.Among them,the analysis of seismic reliability of bridges considering the randomness of structural parameters is a hot issue in bridge engineering in recent years.In this paper,a long-span continuous-girder bridge with railway isolation in a certain city is taken as the research background,and ansys model considering the pilesoil-structure interaction(PSSI)is established to consider the randomness of the value of the proportional coefficient of the foundation coefficient of the site soil.Orthogonal Polynomial Random Response Surface Method(PRSM)is used to analyze the seismic reliability of the long-span continuous-girder bridge with railway isolation considering PSSI.The main research content is as follows:(1)Verify the validity of the reliability analysis by applying the random response surface method(PRSM)based on orthogonal polynomials.The results of two numerical examples show that,the method developed to the fourth-order response surface is highly consistent with the real response surface.Compared with the response surface in SORM and FORM,it has higher precision and efficiency,and the method can be well integrated with commercial software.It is convenient to apply to largescale practical projects and overcomes the time-consuming problem of the Monte Carlo numerical simulation method.(2)By using ANSYS to establish a directly embedded bridge model and a bridge model considering PSSI,three rare-seated seismic waves(ie,EL waves,Hanshin waves,and artificial waves)were selected,and the dynamic characteristics and seismic response of the bridge system were compared using dynamic time-history analysis.The calculation results show that the PSSI has a great influence on the dynamic characteristics of the long-span continuous-girder bridge with railway isolation system.Compared with the bridge model with the pier bottom consolidated,the model considering PSSI reduces the stiffness of the full bridge,the natural vibration period of the bridge structure system becomes longer,and the vibration mode of the structural system changes much.At the same time,PSSI have a large amplification effect on the internal force of the bottom and the displacement response of the bearing of a longspan continuous-girder bridge with railway isolation.(3)Considering the randomness of the ratio coefficient of the ground coefficient of the site soil,we use the PRSM to fit the response surface function of the seismic response.Then taking the internal force of the pier and bearing deformation as the control indexes,we analyze and evaluate the seismic reliability performance of the long-span continuous-girder bridge with railway isolation system.The analysis results show that the seismic design of the bridge meets the requirements of relevant regulations.In the case of rare earthquakes,the bridge piers and bridge piers will not be damaged.However,for the displacement of the abutment support in the rare case of artificial waves,it completely enters the limit state,and the abutment isolation bearing may be damaged.Therefore,in the anti-seismic design,careful consideration should be taken to the design of isolation bearings at the abutments of the long-span continuous-girder bridge.(4)Analyze the guarantee rate(ie,reliability)of the bridge structure corresponding to the values based on experience or norms.The results show that: With the aid of empirical formulas,searching criteria table(only one range is stipulated)and horizontal static load tests for single piles,the values are all estimated to be unsafe,In the seismic design of large or important bridge projects,it is necessary to analyze the reliability of its structural system.