Numerical Simulation Of Tsunami And Wave Forces On Superstructure Of Coastal Bridges

Tsunami is a kind of destructive natural disasters.When a tsunami landed in nearshore,it would attack the residents living along the coastal area and transportation infrastructures due to large amounts of energy.In order to reduce destructive effects of tsunami to offshore structures,many countries have been carried out tsunami warning systems.The generally accepted method for tsunami forcasting is the shallow water equation model combined with the measured data.As an important transportation infrastructure,coastal bridges are vulnerable to be attacked by the huge wave energe.So,it is important to study the wave forces on bridge superstructure and reveal the flow field of wave-structure interaction.Hydrodynamic experiments and numerical models are used to illustrate the above problems and the main sections of this thesis are listed as follows:(1)The explicit method is inserted into COMCOT(Cornell Multi-grid Coupled Tsunami Model),which lead to a fast tsunami warning system.In order to extend the explicit method to solve the tsunami runup in the nearshore area,a new nested grid system is adopted to combine the non-linear wave equations and the explicit method.Finally,the 2004 Indonesia tsunami is used to validate the effectiveness of the explicit method.(2)How to consider the dispersion of tsunami propagation has always been a problem for the shallow water equation model.This paper mainly focused on how to make the explicit method can be used to mimic physical dispersion of tsunami in the varing topography with the uniform grid system.In order to achieve this goal,start from the explicit method,the new dispersion algorithm and the corresponding dispersion conditions are derived.A variable coefficient is introduced in the derived dispersive condition to cope with the varing topography,which simplifies the dispersive conditions and improve the computational efficiency.(3)The hydrodynamic experiments are used to investigate wave forces on thesuperstructure of the bridge.Five type of bridge decks are used to reveal the waveforce in the conditions of three clearances and four wave amplitudes.Secondly theAir Relief Openings(ARO)are setted on the bridge superstructure,experimentsare peformed to reveal the effectiveness of ARO.(4)The open source CFD software OpenFOAM is used to investigate the numerical wave forces on bridge decks,and the experimental data is used to validate the numerical values.Then the flow fields of wave and different types of bridge decks are revealed by the numerical model,and the effects of handrails are also studied by the numerical model.Mor eover,the numerical model is adopted to study the relationship between the wave forces on the bridge deck and the shapes,volume and locations of ARO.In order to further combine the explicit method and Open Foam,the developed numerical model the explicit method is used to get the maximum surface elevation of tsunami,which are adopted as the input condition to obtain the wave forces on bridge decks,so that the security status of bridge can be figured out.