Study On Influence Of Ultra-high Performance Concrete On Light-weighted Composite Bridge Deck

Attributed to its light self weight, high bearing capacity, rapid erecting speed,and superior integrity, orthotropic steel decks (OSD) have been widely applied tolong-span bridges all around the world. However, a lot of engineering experiencesindicate that there are two major technical challenges existing in orthotropic steelbridge deck: fatigue cracking and conventional asphalt pavement failure. Domesticand overseas researchers have tried a lot during the past decades, but theabove-mentionded problems still remain unsolvable fundamentally. To deal with theabove-mentioned typical problems, our research team proposed to add a layer ofreinforced UHPC (Ultra-High Performance Concrete) to an OSD to form a new“light-weighted composite bridge deck”. The reinforced UHPC possesses high tensilestrength as well as high elastic modulus.Based on the renovation of bridge decks in Humen suspension bridge, this paperhas conducted a pilot investigation on the fatigue performance of this innovativecomposite deck system. The following specific works are carried out:Firstly, this paper summarizes the current use-situation, the various diseases anddisease-reasons of traditional steel bridge deck. Then, after giving the materialproperties of UHPC，it introduces the concept of light-weighted composite bridgedeck.Secondly, the fatigue theories of steel bridge are summarized systematically,including fatigue design method, S-N curve in fatigue life evaluation, fatiguecalculation method. And the three basic system of steel bridge deck are thrown lightupon.Thirdly, based on the Humen Bridge, an existing steel box girder suspensionbridge in China, local finite-element models are built using ANSYS software. Then,hot spot stress approach is adopted to calculate traffic-induced stress ranges at typicalfatigue details of the OSD. The UHPC layer is considered as0mm,45mm, and60mm thick in the analysis. The results show that the influence of UHPC layer inlight-weighted composite bridge deck on rib to deck plate connections and thelongitudinal rib splice joints is very considerable, but for other details, the extent ofimprovement is relatively small. According the finite-element analysis results, when a45-mm-thick UHPC layer is applied to the Humen Bridge, after passing8,035,868 standard fatigue vehicles in total, a single with a total weight of330kN, fatiguecracks will appear at the diaphragm of rib-to-diaphragm connections in middle lane.At last, based on full-scale composite beam model of the Humen Bridge, aflexural static test and a fatigue test are designed and conducted. The static test showsthat UHPC has a strain hardening behavior and a long ductility after tensile cracking.The value of elastic modulus of UHPC is suggested as40.1GPa in linear elasticdesign of tension. The fatigue load test reveals that the UHPC layer stays intactwithout visible cracks appearing after application of3,101,389cycles ofconstant-amplitude loading with a tensile stress range of9.8MPa~24.3MPa in theUHPC layer. According to equivalent principles, the equivalent maximum tensilestress of the UHPC layer in the fatigue test is not less than21.3MPa, a value at halfof the static tensile strength of UHPC (42.7MPa). Therefore, the reduction factorregarding the flexural fatigue strength of UHPC is over0.5, and UHPC can satisfy therequirements of Humen Bridge.