Study On The Combined Reconstruction Of Existing Bridge Deck Protective Guardrail

Bridge guardrail is an important protective device to ensure the traffic safety of bridge deck and plays an important role in traffic safety engineering.With the continuous development of Chinese automobile industry,more and more vehicles are appearing on roads and bridges,and the proportion of various types of vehicles is gradually changing.In the current traffic situation,accidents of vehicles rushing out of bridge guardrail occur from time to time,which indicates that the existing bridge guardrail has hidden safety dangers in some degree.From the economical point of view,it is of great significance to use the existing bridge guardrail structure itself and to study the reconstruction technology based on the original guardrail.In this paper,according to the different positions of the existing bridge deck guardrail,the retrofit schemes are studied to solve the problems of insufficient protective capacity of the median W-beam guardrail and the inner curb stone structure of the urban bridge pavement.For the situation that the protective ability of the median W-beam guardrail of highway bridge is insufficient,this paper puts forward two kinds of reconstruction schemes of the combined W-beam,which are fixed and hinged between the column and the horizontal beam.For the condition that the protective ability of the curb structure inside the pavement of the city bridge is insufficient,this paper puts forward the reconstruction scheme of the combined guardail of the curb,in order to make the research universal,the base of the curb stone is connected to the bridge panel in two ways: planting reinforcement and non-planting reinforcement.On this basis,two kinds of finite element models of guardrail are established according to the collision theory and the safety performance evaluation system of guardrail.Then according to the demand of guardrail protection grade of highway bridge and urban bridge,the frontal crash test are performed to verify the reliability of the models of car,bus and truck.Finally,the model of collision system between vehicle and guardrail is established by pre-processing settings in finite element simulation software.In the research on the structure of the median combined W-beam of highway bridge,according to the protection level of highway bridges’ SB guardrail collision test conditions,1.5t car,10 t bus and 18 t truck are chosen for the crash simulation analysis of two kinds of schemes and the hinged connection mode are determined as the better scheme,on this basis,the hinged scheme is further optimized,ultimately determining the best added height for the guardrai.In order to analyze the influences of uncertain factors on the protective performance of guardrail when vehicles lose control,the sensitivity analysis method is used to study the sensitivity of guardrail deformation under different collision angles and different collision speeds based on the optimized guardrail,and the results show that the impact of vehicle collision speed was greater.In the research on the structure of the combined guardrail on the inner curb of the pavement of the city bridge.according to the test conditions in the urban bridges SA level guardrail,1.5t car and 14 t bus models are used for crash simulation analysis.In the simulation analysis of the joint of planting bar,firstly,the effects of different spacing of planting bars and post on the collision performance of guardrail are studied,then reasonable influencing factors and levels are selected to carry out orthogonal design experiment.Through orthogonal design experiment,the parameters of 1.5m spacing between post,100 mm spacing between planting bars,4mm thickness of circular tube beam and 5mm thickness of rectangular tube beam are obtained as the optimized scheme.In the simulation analysis of the curb with no reinforcement connection,the influences of different strength interface and different contact area on the collision performance of guardrail are studied,and it is concluded that increasing the contact area is not as economical and effective as changing the interface connection strength,and the S2 interface with the strength equalling to the old bridge panel is the better solution.Based on the guardrail optimized above two kinds of connection,the sensitivity analysis method is also used to explore the impact of different collision angles and different collision velocities on the impact force and lateral deformation of guardrail.The results show that the impact velocity has a greater influence on the guardrail protection performance under both two connection modes with the same change range of uncertainties.Based on the research of the two kinds of bridge guardrails,this paper provides certain reference value for improving the protective capability of existing bridge guardrails.