Structural Analysis And Experimental Study Of Composite Lightweight Bridge Deck System Of Combined Highway-Railway Bridge

Combined highway-railway steel truss bridge is a classic type of bridge with distinctive structural features.The actual engineering shows that under the combined action of highway,railway coupling load and environmental factors,the deck system is often easy to take the lead in damage and affects traffic safety and patency.In this paper,based on the study of the maintenance and reinforcement of the bridge deck system of the Zhicheng Yangtze River Combined Highway-Railway Bridge,the design idea of the composite lightweight bridge deck system is proposed.That is,on the basis of the orthotropic steel bridge deck with open stiffeners,the shear studs are welded first,the steel mesh reinforcement is laid next,and then the hybrid fiber lightweight aggregate concrete and SMA are added.In order to deeply analyze the influence of various parameters of the deck system on its mechanical properties,a refined finite element model of the multi-level combined highway-railway bridge is established with ANSYS,that is,the integrated model of the combined highway-railway bridge,the local sub model of the highway bridge,the detailed sub model of the bridge deck.The equivalent load and displacement boundary conditions are transmitted between the various levels of models based on the principle of finite element sub model.The results show that this method can well consider the coupling effect of the highway and railway loads,simulate the actual working status of the bridge better,and provide the possibility for the analysis of the refine structure of the bridge system.The finite element results show that the impact of railway load on the most unfavorable mechanical response of the deck system is 62.5%,and the highway load is about 37.5%.So,the design of the bridge deck structure of the rail-road bridge should consider the influence of the railway load.Through the analysis of the structure of open stiffener orthotropic steel deck,the control loading position is obtained considering the coupling effect of the highway and railway load,and the key parameters are optimized: the stiffener spacing is 0.35 m,the height is 0.275 m,and the thickness of the steel roof is 14 mm.The analysis method can be used for reference of similar projects.In addition,studies show that the horizontal shear stress response of the shear studs gradually decreases along the height direction,and the root of the shear studs bears most of the horizontal shear stress.The diameter and number of the shear studs are more sensitive to reduce the stress of the pavement layer,while the spacing and height of the shear studs have less impact on the pavement layer.Comparing with other deck systems,the lightweight of the composite deck system can significantly reduce the stress of the deck system and the girder truss.And the composite lightweight bridge deck system can significantly reduce the seismic response of the bridge and enhance the seismic resistance of the bridge.The scale fatigue test shows that the deck system has excellent fatigue resistance.The bridge load test shows that the measured values of the static load and dynamic load of the bridge meet the requirement of the code.The whole bridge is in safe working condition.This scheme has been successfully applied to the maintenance and reinforcement works of the deck system of Zhicheng Bridge.So far,it has been opened to traffic and operating safely for more than 5 years.It has been tested without any disease and can provide a useful reference for the design and maintenance of the deck system of the combined highway-railway bridge.