Dynamic Response Analysis Of Large Flow Multi-tower Cable-stayed Water Conveyance Pipeline Bridge Under Water Hammer Effect

As a significant infrastructure project that spans across rivers and valleys,the water conveyance pipeline bridge holds a vital position in water transmission projects.Numerous long-span water transmission bridges have been constructed domestically and abroad,contributing greatly to the allocation of water resources,urban water supply,and agricultural irrigation.However,during the pipeline conveying process,it is inevitable to face various operating conditions,such as valve opening and closing,mechanical start-stop or external incentives.The resulting water hammer effect can cause failure or destruction of piping,valves and external structures.At present,the research on the effect of water hammer is mainly focused on pipelines,and the impact of water hammer on bridges is relatively rare and simplified.Consequently,when it comes to long-span,large-flow water pipeline bridges,the live load that water generates could create dynamic responses that may hinder the bridge’s safety performance.Thus,it is imperative to conduct a thorough examination of the action of water hammer on the dynamic response of bridges so as to clarify its influence mechanism,meet the engineering needs,and provide a supporting basis for the design,operation,and maintenance of the pipeline bridge in question.The cable-stayed water conveyance pipeline bridge is an important part of the Hanjiangto-Weihe River Valley Water Diversion Project,and its constant water flow load effect is four times that of the same width highway class I automobile load.The construction of such bridges is very rare in the country and even in the world.Taking the bridge as the research object,this paper carried out the research on the influence of the dynamic response of the bridge under the action of water hammer based on the Shaanxi Provincial Natural Science Basic Research Program project "Research on Key Technologies of Long-span,Large Flow and Multi-tower Cable-stayed Pressure Water Conveyance Pipeline Bridge"(2021JLM-47): Firstly,based on the fluid-structure interaction method,the water hammer test was simulated to verify the effectiveness of the simulation method.On this basis,a three-dimensional numerical simulation model of water-pipe-bridge is established.The structural response of the bridge was studied by fluid-structure interaction and non-fluid-structure interaction respectively to reveal the influence of coupling on the bridge effect.Secondly,the factors that are sensitive to the structure of water hammer are selected for analysis,including valve closing time,pipeline boundary,buttress spacing,pipeline thickness and valve-bridge distance.The influence of vertical,vertical and longitudinal water hammer on the dynamic response of the bridge under different factors was analyzed.Finally,according to the calculation results,the water hammer amplification factor under sensitive factors is proposed.The results show that under the action of vertical water hammer,the bridge will produce a large longitudinal displacement response.However,the axial force of the member and the vertical displacement of the main beam in the middle of the span have no obvious amplification effect,while the bending moment of the main beam only fluctuates in a small range.In comparison to vertical water hammer,vertical and longitudinal water hammer have a larger impact on causing longitudinal displacement responses in the bridge,leading to some degree of amplification effect on the axial force of the member located in the middle of the span.Under the action of vertical water hammer,the valve closing time,buttress spacing and pipeline thickness have a great influence on the longitudinal displacement response of the bridge,while the influence of pipeline boundary and valve-bridge distance is small.Under the action of vertical and longitudinal water hammer,the closing time,pipeline boundary and buttress spacing will have a great influence on the longitudinal displacement response of the bridge.Among these influencing factors,the influence of valve closing time is more obvious.When the closing time is in the range of 6-30 seconds,taking the longitudinal displacement effect at the top of the bridge tower as an example,the range of vertical water hammer amplification factor is 1.023-1.143,and the range of vertical,longitudinal water hammer amplification factor is 1.032-1.193.For the longitudinal displacement of the end of the main beam,the range of vertical water hammer amplification factor is 1.115-1.720,and the range of vertical,longitudinal water hammer amplification factor is 1.114-1.805.The research conclusions can provide reference for the design and dynamic response analysis of water conveyance pipeline bridges under the action of water hammer.