| In order to solve two difficult problems of the fatigue cracking of steel bridge surface and the easy damage of the pavement layer,the author and the research team proposed steel-ultra thin UHPC(35-40mm)lightweight composite deck structures.For this composite structure,conventional shear connectors(such as short studs)can not meet the requirements of the protective layer.Therefore,the research team developed a new type of special connector,the welded steel mesh connector,in order to ensure the synergistic work of the bridge deck and the thin layer UHPC,transfer the shear between the bridge deck and the UHPC layer,and resist the uplift effect.The welded steel mesh connector is different from any previous shear connector,and the connector is embedded so shallow.In view of the connector's characteristics,the uplift performances of the welded steel mesh connector were studied in this paper.The main work was completed as follows:(1)This paper carried out the research on the static uplift performance of the welded steel mesh connector,analyzed the influence of interlayer bonding,steel diameter,weld length and strength of concrete on the load interface separation curve,and evaluated the uplift performance of the connector.Through static uplift test and finite element analysis method,the failure mechanism of connectors is explored,and the characteristics of stress changes of connectors are defined.(2)Based on the static uplift test,the uplift fatigue life of the welded steel mesh connector was studied.Combined experimental research with Miner theory,the uplift fatigue life of steel super thin UHPC lightweight composite bridge deck structure was equivalent conversion.The test results showed that the A-1 component is loaded 500 thousand times under the 6.56kN-32.8kN load amplitude,1 million times under the 8.2kN-41 kN load amplitude and 2 million 110 thousand times under the 7.38kN-49.2kN load amplitude,and the crack width of the UHPC surface is 0.05 mm,the interface separation increases obviously.The A-2 component is loaded under the 7.38kN-49.2kN load amplitude for 3 million 500 thousand times,and The crack width of the UHPC surface is 0.05 mm.The A-3 component is loaded 2 million times under under the 11.48 kN-57.4kN load amplitude,and the width of the crack on the UHPC surface is 0.03 mm,the interface separation is equivalent to the A-1 component.After the fatigue test,the elastic limit load of the connector descends 2.1%-14.1%,the bearing capacity of the uplift cracking is reduced 9.9%-12.4%,the uplift stiffness decreases 27.5%-35.5%.The uplift fatigue performance is good.The reasonable slope parameter of the S-N curve of the welded steel mesh connector is 3.(3)Establishing the section model of Runyang Yangtze River bridge to analyze the actual bridge project.The welding spacing of the welded steel mesh connector are 150 mm at longitudinal and 200 mm at transverse.Interlayer force and UHPC tensile stress of the steel ultra thin UHPC composite deck structures steel super thin UHPC composite bridge structure under the load of the vehicle were calculated.The finite element analysis showed that the maximum uplift force is 2.16 kN and the safety factor is 5.97,the interlayer shear and the UHPC tensile stress can meet the static requirement under the most adverse vehicle load.Based on the Miner linear theory,the estimated fatigue life of the welded steel mesh connectors of steel ultra thin UHPC lightweight composite deck structures is more than 3 million 430 thousand times.The welded steel mesh connector can effectively transfer the shear stress between layers,resist the lifting effect between the steel and UHPC,ensure the steel sheet and ultra-thin UHPC work together. |
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