Fatigue Performance Study Of The Corrugated Steel-UHPC Layer Composite Bridge Deck

The fatigue problem of orthotropic steel bridge deck(called OSD)is serious,and further optimization of structure system is an effective way to solve this problem.Based on the existed types of bridge decks,a new structure composed of corrugated steel and UHPC layer is proposed in this paper.Compared with OSD,the UHPC layer can increase the stiffness of the bridge deck;the corrugated steel can improve the local stress concentration by reducing the number of welds and geometric discontinuities.In order to verify the structural rationality and superior anti-fatigue performance of the composite bridge deck(called CD),the main works are shown as follows:(1)The dimension of CD study.The effects of varied parameters including the UHPC layer thickness,the corrugated steel thickness,the lower edge plate width,the horizontal projection of the inclined plate width,and the wave depths are studied and the feasible ranges are determined via the local finite element model.The parameters’ combination is further optimized by the Ideal Point solution and the reasonable parameter matching is established.Comparing with the spandrel-filled composite bridge deck,the UHPC usage is reduced by 52%,the weight is reduced by 39%,the cost is reduced by 36% per meter,the stress of steel is increased by less than 5%,while the stress of UHPC layer is reduced by 27%,35%.(2)Fatigue life assessment of the fatigue details study.The stress response of details with local wheel load movement is analyzed,and based on the Miner linear cumulative rule,the nominal stress fatigue assessment method,the hot spot stress fatigue assessment method and metal stress fatigue assessment method are used to evaluate the fatigue life.Compared with OSD,the fatigue life of rib-to-diaphragm weld,arc-shape cutouts in diaphragm and steel plate bends / rib-todeck weld in CD is increased by at least 2 times;fatigue damage will not occur within the design service life of other details,in addition to the fatigue life of the arc-shape cutouts is 58 years.(3)Fatigue assessment of the stud study.Taking the weld toe at the root of the stud as the research object,the 0.5t/1.5t extrapolation method is used to evaluate from the two perspectives of design stress amplitude and fatigue life.The result shows that the local wheel load affects about 3 to 5 rows of studs;about 25 million standard fatigue cars’ rear wheels pass,fatigue damage may occur at the stud located above the diaphragm.