Mechanical Property And Parame-ter Sensitivity Analysis Of Double-wall Steel Cofferdam In Complex Marine Environment

Circular double-wall steel cofferdam is widely used as temporary structure in deep-water long-span bridge construction due to its simple structure,large stiffness and strong stability.Due to the complex stress conditions,the double-walled steel cofferdam will have accidents such as water leakage of bottoming concrete,instability even collapse of inner support under complex dynamic water.Therefore,it is necessary to carry out the dynamic response and structural parameter sensitivity analysis of double-wall steel cofferdam.Based on the numerical calculation of ANSYS Fluent,this paper reveals the characteristics and generation mechanism of the force of water flow and wave on the circular double-walled steel cofferdam.The structural deformation and stress response of current force,wave force and wave-current forces were studied by ANSYS Workbench.Finally,the parameter sensitivity of double-wall steel cofferdam is analyzed.The main work and research results are as follows:(1)The flow force and wave force of the large-scale circular double-wall steel cofferdam have been studied by numerical simulation.The numerical results reveal the weak correlation between the drag coefficient and Reynolds number of smooth cylindrical structures in supercritical region,and the deviation of the scale model and the full-scale model in structural stress and vortex shedding is pointed out.For large-scale circular double-wall steel cofferdam,the flow field characteristics and stress conditions under the action of flow and wave are calculated respectively.(2)The structural dynamic response of circular double-walled steel cofferdam under the flow force,wave force and wave-current forces have been studied by numerical simulation.The numerical results show that the response law of structural deformation and component stress under three types of hydrodynamic pressure is consistent with the fluctuation law of dynamic load.When the hydrodynamic load is simplified as static force for structural deformation and stress analysis according to the specification,the calculation results are different from the dynamic analysis in the maximum deformation position,maximum deformation and maximum component stress.(3)The influence of different component parameters on circular double-wall steel cofferdam has been studied by numerical simulation.The numerical results show that the influence of different component parameters on the dynamic response of circular double-wall steel cofferdam is as follows: the size of vertical stiffener > the thickness of inner and outer wall plates >the distance between horizontal annular plate and brace > the size of horizontal brace.According to the sensitivity of each component to the above parameters,the optimization suggestions for adjusting structural deformation and stress are proposed.