Study On Performance-based Seismic Design Method For Highway Tunnel Structure

With the large-scale construction of China's traffic,the highway tunnel has exceeded 1200 million meters.Safeguarding the security of major infrastructure and regional transportation systems turns out to be a significant policy for china ' s architectural engineering field.However,in the previous giant earthquake,the tunnel structure still suffered from serious damage.At present,the seismic design concept of highway tunnels cannot meet the needs of modern seismic fortification.Therefore,it is extraordinary urgent to introduce new seismic design concept,the emerging performance-based seismic design method,into the road tunnel seismic filed.To begin with,this paper,based on the classification of seismic fortification,establishes a new standard for seismic fortification.Secondly,in order to determine the performance parameters of different performance levels and design control objectives,this paper researches the classification of tunnel geological hazard and damage mechanism.At last,this paper carries out the research on the tunnel catastrophe mechanism and the quantitative performance index of arch section,based on Elastic-Plastic Time-history analysis and Pushover analysis.Finally,the strength and deformation checking method is established,and the performance-based seismic design method of tunnel structure is formed.The main results as followed:(1)Based on the use function,the seismic fortification category of highway tunnel is divided into 4 categories,and the seismic performance level of highway tunnel in the mountain area is put forward,and the qualitative seismic performance targets at all levels are established;Through the seismic damage investigation and the dynamic time history analysis,the tunnel damage type is divided into five categories.According to experts' research on the catastrophe form and pattern of tunnel under earthquake,this paper divides earthquake catastrophe model into stress damage and structural damage.(2)Based on the comparison between the dynamic time history analysis method and the maximum acceleration distribution law of the inverted triangular acceleration loading on each soil layer,the horizontal load distribution form of the pushover method is determined.Based on certain loading forms,this paper compares the analysis results of pushover method and dynamic elastic-plastic time history method,the results shows the stress trend of the cross section is identical,which firstly increases and then decreases.After verifying the seismic application of pushover method in arch tunnel,this paper establishes pushover analysis method for tunnel structure.(3)The pushover method is used to study the transverse seismic behavior of tunnel structures in different depths,geologic conditions and different concrete grades.Considering the elastic-plastic response characteristics and the actual seismic damage investigation results,the relative deformation rate is selected and defined as the seismic performance index,and the threshold of performance targets is determined.On the basis of summarizing the seismic performance of rectangular and circular sections tunnel,the quantification performance indexes of the three performance levels are determined,and the seismic performance design method of highway tunnel is improved.In this paper,the performance-based seismic design method of highway tunnel structure is established,which provides the support for the establishment of performance-based seismic design theory and method.