Parameter Analysis And Optimization Of Orthotropic Sandwich Bridge Deck Of Self-anchored Suspension Bridge

The steel-polyurethane composite orthotropic bridge deck(the SPS orthotropic bridge deck)is a new type of bridge deck structure,which is composed of a polyurethane elastic core layer and the top and bottom steel panels.This structure can greatly reduce the fatigue cracking of traditional orthotropic steel bridge deck welds,and has been used in new construction,repairment,and reinforcement abroad,but rarely in domestic engineering applications,let alone large-span bridges.Especially for self-anchored suspension bridges,the steel box girder itself is subjected to strong longitudinal pressure,while the steel bridge deck in the positive bending moment section is subjected to greater longitudinal pressure,and the steel bridge deck is prone to stress concentration,which leads to structural fatigue cracking or buckling.Therefore,this paper attempts to apply the SPS orthotropic bridge deck to the self anchored suspension bridge project creatively,uses the multi-scale modeling method to research and analyze,and explores a new type of bridge deck alternative with better performance.The main research work is as follows:(1)Based on the Huaihe Highway self anchored suspension bridge project,the whole bridge model is established,and the most unfavorable section of steel box girder is determined and extracted for fine modeling.Then,the stress and deflection of the traditional bridge deck steel box girder model and the SPS model with three different parameters are compared and analyzed.The results show that: the bending rigidity of SPS model in longitudinal and transverse direction is significantly improved;SPS1 model can be used as the key structural form of SPS orthotropic bridge deck for repairment and reinforcement;The stress distribution of the bridge deck is more uniform due to the stress diffusion of polyurethane core layer,which slows down the stress concentration phenomenon.(2)The parametric model of SPS orthotropic bridge deck is established to calculate and analyze the influence rule of local stress and deflection when eight structural parameters change.The results show that: the thickness of both steel deck and polyurethane can improve the local mechanical properties of SPS orthotropic bridge deck;The opening width and height of U-shaped longitudinal rib are conducive to the improvement of longitudinal stress and transverse stress respectively,but it can not improve the longitudinal and transverse stress at the same time;The change in thickness of U-shaped longitudinal ribs has little effect on the local mechanical properties of the structure except itself;Compared to traditional bridge decks,the increased stiffness of the SPS orthotropic bridge deck can reduce the number of longitudinal stiffeners,thereby reducing welds and the number of hollowed out diaphragms;The change of diaphragm spacing can significantly improve the structural deflection.When the number of sling segments increases to 4,the difference of mechanical properties is very small,so the number of sling segments should not be greater than 4.(3)Considering the influence of geometry nonlinearity,material nonlinearity and initial geometric defects,the influence rule of structural parameters on the stability bearing capacity of SPS orthotropic bridge deck is analyzed.The results show that: the increase of steel deck thickness can significantly improve the stability bearing capacity;Although the increase of polyurethane thickness can improve the stability of bridge deck,it is not suitable to simply increase the polyurethane thickness;Although the increase of the number and height of longitudinal ribs can improve the ultimate bearing capacity of stability,the influence will decrease when the parameters increase to a certain value.Therefore,the number of longitudinal ribs can be appropriately reduced(i.e.increasing the spacing of longitudinal ribs),so as to reduce the number of welds and weaken the fatigue problem of deck details at the root.(4)Based on the optimization module of ANSYS,the principle of structural optimization design,including its mathematical model and the realization process and steps in the ANSYS program,is described in detail.Then,the reasonable design sequence under the three optimal design methods is analyzed,and the optimal SPS orthotropic bridge deck scheme based on the project is finally obtained,which provides necessary reference for the later application of the structure in self anchored suspension bridge and other long-span bridges.