Parameter Analysis And Optimization Of Orthotropic Sandwich Bridge Deck Of Cable-Stayed Bridge With Steel Box Girder

The steel-polyurethane orthotropic sandwich plate(SPS)is a new sandwich structure which composed of two pieces of steel faceplates and one polyurethane core,and these two materials are firmly bonded by the molecular force which generated by the thermochemical reaction.This new structure has been applied to construction,maintenance and reinforcement of bridge in foreign countries,but it's rarely used in China.And as a new bridge deck structure,there is no corresponding design specification at home and abroad.In this paper,SPS is applied to steel box girder cable-stayed bridge,and its mechanical properties were studied by multiscale modeling method.The main works of this paper are listed as followings:Firstly,this paper summarized the application and research status of SPS at home and abroad,and introduced the mechanical theory of SPS sandwich plate.Then the Timoshenko energy method has being used to deduce the bending stress of the simply supported SPS which under the local uniform load.Not only that,the critical buckling stress of SPS under axial pressure axial pressure is also being calculated.Secondly,based on the Jiangwan Bridge,the most negative section of the steel box girder in the whole bridge was extracted.And the steel box girder segment model with ordinary steel bridge panels and two different SPS bridge deck are established respectively.Considering different longitudinal load conditions,the stress and deflection of the bridge deck were calculated.The results show that the SPS meets the stress requirement,and the polyurethane core layer is good for stress diffusion.However,adding the polyurethane core layer has little effect on reducing the stress of the bridge deck while keeping the thickness of the steel plate constant.Therefore,another method is to reduce the number of stiffener ribs while increasing the core layer.After that,this paper established a submodel of bridge deck,and analysed the influence of various parameters on stress,deflection and stability of SPS sandwich bridge deck.The results show that the stress and deflection are greatly affected by the thickness of the steel faceplates,the spacing of the stiffening ribs and the spacing of the diaphragms.And the thickness of polyurethane,the height and thickness of the stiffening ribs have less influence.Stability analysis shows that increasing the polyurethane core layer is beneficial to the stability of bridge deck.In addition,increasing the thickness of steel faceplates,the number and thickness of stiffening ribs can also improve the stability of bridge deck.However,increasing the height of stiffening ribs is is disadvantageous to the stability of bridge deck,and the spacing of diaphragms has little influence on the stability of bridge deck.Finally,this paper briefly described the relevant knowledge of optimal design.Then threespan SPS sandwich deck was selected as the optimization object,taking the total mass of bridge deck as objective function,the structural parameters of SPS bridge deck were optimized by three methods under the constraints of strength,stiffness and stability.At the end of the paper,the parameters of the bridge deck with the lowest quality are obtained under the stress condition of the completed bridge.It provides a reference for the application of SPS in cable-stayed bridge in the future.