Random Wave Impact On Different Shore Types Pier Superstructure Study

In coast and offshore engineering, the safety of the structures whose superstructures located in the splash zone such as piled wharves, shore trestles, oil drilling platforms, etc, have great relation to wave slamming. Under confused sea condition, the structures may subject to very strong w ave impulsive 1oad due to slamming by the wave with significant crest when waves propagate underneath the structure and surge up to its subface. Previous studies indicate that impact pressures are characterized by an initial peak pressure of considerable magnitude but of short duration occurs, followed by a slowly-varying uplift pressure of less magnitude but of considerable duration, and which typically is first positive, then decreases to zero and becomes negative, In hostile sea state, the peak pressures may cause the damage of the horizontal members of the structures or make the whole superstructure collapsed. Also the concrete structure's service life may be threatened by the negative pressure occurred when waves separate from the subface of the structures. In the recent twenty years, the forecast of wave slamming loads in the design of coast and offshore engineering has become a new subject. This paper presents the experimental investigation of random wave impact on piled wharves with different shore connecting structures, also the certification analysis by the numerical simulation results.The experiments were conducted in the large wave-current tank in the State Key Laboratory of Coastal and Offshore Engineering, Dalian University of Technology. The modified JONSWAP spectrum is chosen as the target spectrum of the random wave. The incident wave height H1/3 is in the range from 0.1m to 0.25m, and the peak period TP in the range from 1.0s to 2.0s. The ratio of s/H1/3, which refers to the subface level of wharf deck (s) to the incident wave height (H1/3), is between -0.1 and 0.7. Three different shore connecting types: open-piled, permeable slope with armored 1ayer of dolosse b locks and impermeable slope with armored layer of concrete plate, are set in the experiment for the research on the effects of boundary condition with different shore connecting types on the wave impact.Based on the experimental results for different wave height, wave period and the relative clearance of underside of the wharf deck, the properties of wave impact pressure on wharf deck are studied. The distribution of impact pressure along the underside of the deck model is analyzed. The influence of different incident wave parameters, structure dimension and relative clearance s/H1/3 on the impact pressure is discussed. The empirical formulas are given for the design of the engineering application. And the similarities and differences between the properties of regular wave impact pressure and that of the irregular wave impact pressure are discussed. According to the analysis of the w ave impact pressures on the wharf deck with different shore connecting structures, the effect of different shore connecting structures on the impact pressure on wharf deck is discussed.Based on the unproved VOF method, parametric studies have been carried out for random wave slamming on open piled wharf by numerical simulation. The governing equations are Reynolds time-averaged equations and two equations k - model. Third order upwind difference scheme is applied to convection term to reduce the effect of numerical viscosity. Appropriate moving contact-line boundary conditions are introduced to model wave incontact with and separation from the underside of structure. The numerical random wave flume wave-maker appropriate for the volume of fluid method (VOF) is established. The numerical computation results of wave pressure on open-piled wharf deck for different parametric cases are verified by the experimental results. Great progress is made on the numerical model for the study of wave slamming problem.