ABSTRACT:

An experimental study has been carried out to investigate impact pressures on a slab and a vertical pile due to regular waves. The pressures on the bottom of the slab are measured by the pressure transducers and hydrodynamic loads acting on the pile are measured by a four-component balance. It has been found that in a wave period, wave pressure undergoes periodic variation along with time. Moreover, the influences of relative clearance height and length of the slab on the impact pressures are discussed. On the other hand, comparison is carried out thoroughly between the hydrodynamic force exerted on the single pile with and without the effect of the slab.

1.INTRODUCTION

The problem of wave force acting on structures is of significant importance for the security of piers, platforms and slabs. A particular illustrative case is that the Ekofisk platform (Gebara, Dolan, Pawsey, 2000; Jha, Kiciman, Gebara, 2000). Isaacson and Prasad (1993) found that the slamming phenomenon was of a high frequency in nature. A number of publications related to wave slamming on horizontal cylinder or horizontal plate have been published. Both theoretical analysis and experimental results have been presented and discussed. Kaplan and Silbert (1976) developed a solution for vertical force exerted on a horizontal cylinder from the instant of impact to full immersion. For cylinders, wave slamming force is generally expressed by a slamming coefficient Cs. In recent years, experimental studies on the distribution of pressure along a horizontal plate have been performed in ever increasing numbers, and correspondingly various empirical relationships are proposed (Song, Bai, 1997; Zhou, Chen, 2003; Zhou, Chen, Huang, 2003; Ren, Wang, 2004). Zhou (2004) proposed that the maximum total uplift forces did not necessarily occur with the maximum impact pressure intensity synchronously.

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