Seismic Performance Analysis Of Multiple Arch Bridge Based On Pushover Method

As a pivotal project in transportation,it is necessary to ensure the safety performance of bridges after encountering earthquakes.There are many stone arch bridges built in earthquake areas in China,many of which exist in the form of multiple arch,multiple-hole arch bridge,especially those with flexible piers,due to the existence of multiple arch effect,compared with the single-arch arch bridge damage is more serious.With the popularity of performance-based seismic design ideas,if the representative method,a concise and reliable seismic performance evaluation method,Pushover can be applied to this traditional bridge type,it will be extremely beneficial to the protection and development of this type of bridge.In this paper,a five-hole continuous arch bridge is taken as an example to study the applicability of Pushover analysis method in multiple-hole arch bridge.Firstly,the natural vibration characteristics of the bridge are analyzed for the reference of later vibration mode selection.According to the site conditions of the bridge,three seismic waves suitable for the bridge are selected for time history analysis.In Pushover analysis,the mass center is selected as the displacement control node.The uniform and the inverted triangle modes in the fixed loading mode and the adaptive mode of the equivalent basic modes are used to load the capacity spectrum curves in the direction of the transverse bridge and along the bridge respectively,and then combined with the demand spectrum obtained by the conversion of three seismic waves.The ATC-40 capability spectrum method,Chopra’s improved ability spectrum method and simplified capability spectrum method are used to solve the seismic response of the bridge,and the modal Pushover method which can consider the influence of higher-order modes is used to solve the seismic response of the bridge.The calculation results are compared with the time history analysis results to find the lateral load loading method and capacity spectrum method suitable for the bridge type.Finally,the capability spectrum curve is combined with the demand spectrum obtained by the conversion of the standard response spectrum in China to evaluate the damage of bridges under the action of earthquakes at all levels.The analysis shows that the mass distribution of the vibration modes is discrete,the basic mode has no control on the transverse direction of the bridge,and the basic mode has control on the longitudinal direction of the bridge.The lateral stiffness is relatively large,and it is basically in the elastic stage under the specified waterproofing.The most disadvantageous seismic load combination of the bridge should be should be dominated by the seismic action along the bridge.For the direction of transverse bridge,the inverted triangle loading mode is recommended for Pushover analysis,and the result is more accurate than the more complex adaptive mode.For the along-bridge direction,the adaptive mode loading combined with Chopra’s improved ability spectrum method can accurately estimate the seismic response of the bridge.The modal Pushover method has higher accuracy.For a multi-arch bridge with a high influence on the high-order mode,the modal Pushover analysis can more accurately evaluate the seismic response of the bridge.The bridge can maintain good working performance under the required 7-degree seismic fortification intensity.The performance-based seismic evaluation method can accurately and detailedly evaluate the performance states of bridges under different fortification intensity.Therefore,it has broad prospects for engineering application.