Research On Longitudinal Seismic Response Analysis Method And Seismic Performance Of Tunnels

Tunnel structures are essential parts of lifeline engineering systems.Hidden damages and difficult restorations of tunnel structures could cause great economic losses in the event of an earthquake.Through theoretical analysis and numerical technique,this dissertation is devoted to the longitudinal seismic response analysis method and seismic performance of underground tunnel structure.The main contributions of this study can be described as follows.(1)Theoretical derivation and consistency proof of the integral response deformation method are presented.According to the free-field seismic response,a method of determining the critical moments when the longitudinal maximal deformation and internal force of a tunnel structure occur is given.Then the longitudinal integral response deformation method that is applicable to longitudinal seismic response analysis of underground tunnels is put forward.And seismic response analysis of layered site-tunnel system can be carried out by using the proposed static method.Compared with the dynamic time-history analysis method,it is proved that the proposed method has high accuracy.(2)This dissertation conducts a comparative study of two pseudo-static approaches,which are the proposed longitudinal integral response deformation method and the longitudinal response deformation method suggested by the “Code for seismic design of urban rail transit structures”,respectively.Both computational models and equivalent actions of the two pseudo-static methods are research emphases.Through the numerical simulations of the actual project,computational error sources of different pseudo-static methods are analyzed as well.The conclusions of this part provide a reference for selecting the appropriate practical methods in engineering design.(3)Dynamic time-history analyses of longitudinal seismic responses of large-space tunnels are conducted in this dissertation by building refined soiltunnel structure finite element model.It is proved that the means of simplifying tunnels into beam elements is no longer applicable.Combined with the law and characteristics of longitudinal seismic responses of large-space tunnels,the integral response deformation method for the longitudinal seismic response analysis of large-space tunnels is developed.By analyzing the effects of two inertial forces,a simplified longitudinal integral response deformation method for large-space tunnels is presented,which maks the calculation and analysis more convenient and efficient.(4)For the issue of longitudinal seismic response of tunnels in complicated sites,the method of determining the structural least favorable cross-sections and the critical moments by free-field motion is proposed.And the integral response deformation method for the longitudinal seismic response analysis of tunnels in complex sites is established.It is more suitable for aseismic calculations when the tunnel structure design is repeatedly adjusted in complicated sites.Hence,the application scope of the longitudinal integral response deformation method is widen.(5)The seismic response laws of tunnel structures under P wave and SV wave are studied.The characteristics of seismic response of underground tunnel structure when P wave and SV wave are incident at different inclination and orientation angles are summerized.And the range of adverse incident angles of different types of waves in longitudinal seismic response analysis of tunnels are given.