| Orthotropic steel deck(OSD)is widely used in medium and long-span bridges owing to its light-weight,high load-bearing capacity,and good integrity property.However,the OSD is susceptible to fatigue cracks,and the pavement is prone to damage.Steel-ultra high-performance concrete(UHPC)composite deck is an excellent measure to solve those two diseases of OSD.Based on the in-situ test and finite element analysis,this study evaluates the fatigue performance of the steel-UHPC composite deck and ERE(Epoxy bond chips layer + Resin asphalt +Epoxy bond chips layer)deck in the Junshan Yangtze River Bridge,which is a long-span cable-stayed bridge.The fatigue cracks and pavement damages occurred on the Junshan Yangtze River Bridge during the bridge’s lifetime.Therefore,the bridge’s upstream and downstream deck pavement were replaced by ERE and steel-UHPC composite deck.Besides,the steel plate was bonded to the downstream side steel deck plate to reduce the cracking risk of the UHPC layer.The main contents and conclusions are as follows.(1)The whole finite element model of the bridge is established by Midas civil.It was calculated that the stresses on the upper and lower edges of the steel box girders and the stresses in the bridge’s cables.The results show that the maximum stress of the steel box girder and cable is respectively 107.1 MPa and 503.7 MPa,after replacing the upstream and downstream deck pavement.The overall stress state of the bridge meets the specification design requirements and has an extensive safety reserve.(2)The crack resistance of the UHPC layer was studied by establishing a finite element model of the steel-UHPC composite deck.The results show that there is a cracking risk at the bottom of the UHPC layer of the steel-UHPC composite deck when there are penetration cracks that are not repaired in the steel deck plate.The maximum tensile stress of the UHPC layer was 7.9 MPa.The cracking risk in the UHPC layer was significantly reduced after the steel plate was bonded to the steel deck plate.(3)Based on the traffic flow information and in-situ strain data under random traffic,it was studied and compared the effect of the ERE and Steel-UHPC composite deck to improve the OSD fatigue performance.The results show that the steel-UHPC composite deck was subjected to heavier traffic.Even in this case,compared to the ERE deck,the effective stress ranges of each fatigue-prone detail on the steel-UHPC composite deck are reduced by 19% to 66%.The residual fatigue life of the rib splice welded joints at the ERE side is only 47 years,and there is a risk of fatigue damage in the area during the service period of the bridge.The residual fatigue life of the rib splice welded joint of the steel-UHPC composite deck is 100 years,and the other fatigue-prone details satisfy the requirements of infinite life.(4)A segment finite element model was established to discuss the stress distribution of each fatigue-prone detail and the flexural stiffness of ERE and steel-UHPC composite decks.The effect of overload was also considered.The results show that the stress distribution of each fatigue-prone detail is the same for the two decks.Compared to the ERE deck,the stress ranges of each fatigue-prone detail on the steel-UHPC composite deck are lower.Under 1.5 times the design load,it is exceeded their corresponding constant amplitude fatigue limit respectively by 10%and 42% that the maximum stress range at the rib-to-floor beam welded joints rib side at the ERE deck and rib splice welded joints at the steel-UHPC composite deck.The two details do not satisfy the requirement of “infinite” life.Compared to the ERE deck,the maximum deflection of the steel-UHPC composite deck is reduced by 31%.The greater flexural stiffness of the steel-UHPC composite deck can be attributed to two main reasons:(i)the increase in the young’s modulus of the material;and(ii)the UHPC layer and the steel deck plate form a composite deck structure through shear studs. |
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