Research On Light-type Composite Bridge Deck System With Steel And Ultra-thin UHPC Layer

In order to put thinner UHPC(Ultra High Performance Concrete)layer combine with orthotropic steel bridge deck to form light-type composite bridge deck system with orthotropic steel bridge deck and ultra thin UHPC layer(Hereinafter referred to as steel-ultra thin UHPC layer composite deck).Therefore it can be applied to thinner design deck pavement structure,and tried not to change the original stress state of the bridge structure.This article is about to research the basic performance of steel-ultra thin UHPC layer composite deck. Steel-ultra thin UHPC layer composite deck is putting 35 mm thinner UHPC layer combine with orthotropic steel bridge deck to form a composite structure.And the steel mesh in the UHPC layer is welded directly within the roof of orthotropic steel deck to bear the shear between the them.Apart from 35 mm UHPC layer,the overall composite deck also inclu des 15~20 mm wearing course laid on the UHPC layer.This kind of composite bridge deck must be under the premise of its basic performance of safety and durability,then reducing its thickness and expanding the scope of use to meet the goal of increasing dec k's stiffness,reducing the risk of fatigue crack of orthotropic steel deck and avioding the pavement disease problem of traditional asphalt pavement.Based Runyang Yangtze river bridge of south suspension bridge as the research object.Researched on the orthotropic steel deck of its steel-ultra thin UHPC layer composite deck program.The paper completed the following work:(1) Discussed the traditional orthotropic steel bridge deck and its pavement disease problem.Proposed steel-ultra thin UHPC layer composite deck program. Describe the structur's features and explained the necessity of the design of this omposite deck.(2) Used the finite element software Midas to conduct a overall calculation of Ruyang Yangtze river bridge of its steel-ultra thin UHPC layer composite deck program. Calculation results show that using composite deck has little effect on the overall mechanical condition of the bridge and it has almost no effect on structure 's safety.(3) Used the finite element software ANSYS to conduct a local calculation of Runyang Yangtze river bridge of its steel-ultra thin UHPC layer composite deck program by hot spot stress method. Used the domestic rules and regulations of the vehicle load to analysis composite bridge deck. The analysis result shows that 35 mm UHPC significantly improved the performance of orthotropic bridge deck. Stress-range of the top deck plate reach a decline of 68.72% while trough rib and transverse rib reach a decline of 11.98% to 32.38%.It will obviously reduce the risk of fatigu e cracking of the deck. Meanwhile,the caculation result of maximum tension stress of UHPC surface layer is 7.48 MPa while the transverse maximum tensile stress is 7.36 MPa.(4) Conducted the bending test study of the 35 mm UHPC composite deck cross the bridge. The test results showe that cracking strength and ultimate strength is closely related to its section reinforcement ratio of UHPC layer. With the increase of reinforcement ratio, bending tensile strength increased, cracking stress also increases gradually. The minimum cracking stress of specimen B5 has reached 26.3MPa of the surface of UHPC,which is nearly 3.6 times as much as the maximum theoretical stress values obtained under calculation. It is believed that under the provisions of the vehicle load, the maximum tensile stress generated by UHPC surface is less than the tensile stress which UHPC surface can bear by experiments. So it can ensure the safty and reliablity of the structure which proves the feasibility of the new-type composite bridge deck system.(5) Explained the basic theory of fatigue assessment of steel bridge. Briefly described the the three methods of fatigue design steel bridge and briefly compared the fatigue design specifications of steel bridge of the United States, Europe and China. Used hot spot stress method to assess the fatigue life of steel-ultra thin UHPC layer composite deck of Runyang Yangtze river bridge. According to the European norm(Eurocode) to determine the fatigue load model. Calculated the hot spot stress and determine the stress frequency spectrum which is most unfavorable for structure detail. Finally, assessed the fatigue life by hot spot stress S-N curve and Miner linear cumulative damage theory.