The Comparative Study On Wave Force Calculation Methods Of Bridges

Part of the substructure of cross-sea bridges is submerged in water, where the environment is complex.The substructure is composed of multiple rows of piles mostly, which bears large wave force.The wave force is a dynamic load, alternating positive and negative force, which easily leads to structural fatigue damage or even destruction. Therefore, study on the calculation methods of the wave force on bridge’s substructure has important and practical significance to improve the safety and durability of the bridges.The primary contents of this paper are as follows:(1) Collect main scholars calculation methods of wave force on pier structures at home and abroad, and carry on the detailed analysis, comparison and research on the theoretical basis and practical calculation and parameter selection of these methods sum up the basic rules and characteristics of these methods. These methods divide pier structures into small-scale pier structures and large-scale pier structures, according to the scale of pier structures relative to the wavelength. Calculation method of wave force on a small pile is the Morison equation based on potential flow theory, which can obtain the analytical solutions of linear wave theory and calculate pile group by the pile group effect. Calculation method of wave force on a large pier must consider wave diffraction effect. The analytical solution of wave force on a circular pier and a quadrate pier can be obtained by linear wave theory. Through the examples, the distribution characteristics of wave force along the height of pier by using these methods is obtained and results with a circular pier and a quadrate pier are compared. For the distribution of wave force along the height of a quadrate pier, the calculation results are consistent compared to the results of the scholar calculation method and the code empirical formula.(2) Collect and discuss calculation method of domestic and international specifications about wave force on the pier structure. The specifications are consistent in calculating theory, but for the wave theory and the selection of hydrodynamic coefficients. Through calculation analysis, the Asia specifications coefficients is conservative, but the calculation method of the European and American specifications consider more factors and involve a lot of experience parameters, which are more reasonable.(3) As a cross-sea bridge for example, by changing the location of pile cap relative to the depth of the water to study the wave force on the pile cap and the piles. The pile cap will has huge wave force when part of pile cap is under still water level and the other part is above still water level, so the location of pile cap relative to the depth of the water should be considered while designing a cross-sea bridge.