Static And Seismic Response Analysis After Scouring On Continuous Bridge Combined With Flow Force During Flood Period

Floods is still one of the major natural disasters facing the whole world, the water level will increase substantially during flood, parts of river will be some new forms, such as large water flow and flow velocity greater than 3m/s. In addition, with the large-scale construction of the crossing-river bridge, the flowing environment conditions around the substructure piles become more complex, the flow rate changes continuously,large diameter of the piles will increases the water blocking effect. Due to the covering effect, the design of pile group will make the flowing environment different with the solo-pile, the water level surrounding piles will suddenly surge, that makes the flowing be very complicated, resulting flow kinetic energy into lateral forces onto the bridge piles, this will present a greater challenge to the bridge piles.At present, most of the study about the flowing act is around the subcritical Reynolds region and mainly using two dimensional numerical simulation, but the study of flowing under the supercritical Reynolds region during flood is relatively seldom. In this paper, the study is relying the strengthening engineering of WoLong bridge crossing the Wei river, selecting one joint of the worst affected piles. Based on the fluid dynamics(CFD) principle, this paper firstly analyze the three-dimensional flowing state around the bridge piles with the flow analysis software Fluent, getting the flow characteristics, the flow resistance coefficient and the cover coefficient around series two and three piles under the different L(pile space)/D(pile diameter).The results showed that the flow characteristics between the supercritical and subcritical Reynolds region is different, the flow resistance coefficient under the supercritical Reynolds region is smaller, the cover relationship is more complex, thus it has no strong regularity; Based on the finite element theory, this paper carried out the spatial static and seismic response analysis with the flow act on the piles using structural finite element software Midas Civil. The results showed that it will greatly increase the piles internal force and displacement with considering the flood effect compared with no flood effect, but the flow effect on the axial force is quite small, the seismic response of structures varies greatly compared with no scouring, so it should reinforce the structure promptly after scouring; At the same time, comparing with the flow resistance coefficient in the specification, we can see that the coefficient given by the specification is somewhat safe, and it has greater affluence. In fact, there is room for optimization of structural design.