On Hydroelastic Behavior of Very Large Floating Structures for Ocean Space Utilization

对超大型浮式海洋结构物在波浪中的水弹性行为进行了理论和试验研究。1.采用干模展开技术和混合积分方程法相结合的方法，编制了超大型浮体结构波致水弹性响应的计算程序。在规则波水池中进行了模型试验，测量了VLFS模型的水弹性响应。该模型由多块铝板组成，这些铝板连接在一个开缝的聚乙烯块上，以提供浮力。除了具有不同弯曲刚度和质量的模型外，还对波前边缘带有竖壁和水平潜板的VLFS模型进行了试验，以考察减小VLFS边缘区域大挠度的可能性。通过一系列试验得出以下结论：(1)VLFS模型的运动响应以高阶弹性振型为特征。随着波频的增加，除了在波前边缘附近观察到大挠度外，响应幅值都急剧减小。(B)在波前边缘附加垂直墙或水平潜板可以减小边缘区域的大挠度。波频越高，其影响越明显。当VLFS的长度超过波长的五倍时，附加长度与吃水相当的边板，响应减小到约2/3到1/2。(C)理论和实验预测结果令人满意地吻合，证实了所提出的分析方法的有效性。

Theoretical and experimental studies have been performed to predict the hydroelastic behavior of a very large floating offshore structures (VLFS) in waves. The results of the project are summarized as follows :1. A computer program has been developed to predict the wave-induced hydroelastic response of a VLFS by combined use of a dry-mode expansion technique and the hybrid integral-equation method.2. Model tests have been conducted to measure the hydroelastic response of a VLFS model in a regular wave tank. The model is composed of a number of aluminum plates attached to a slitted polyethylene block to provide buoyancy. In addition to the models with different bending stiffnesses and masses, a VLFS model with a vertical wall or a horizontal submerged plates at the wave-front edge were tested to investigate the possibility of reducing the large deflection near the edge zone of the VLFS. The following conclusions were derived from the series of tests.(a) The motion response of the VLFS model is characterized by the higher-order elastic modes. With increasing the wave frequency, the response amplitudes are reduced drastically except near the wave-front edge where the large deflection is observed.(b) Attaching the vertical wall or the horizontal submerged plates at the wave-front edge has the effect of reducing the large deflection at the edge zone. Its effect is more pronounced with increasing the wave frequency. When the length of the VLFS exceeds five times the wave length, the response is reduced to about 2/3 to 1/2 with attaching the edge plates whose length is comparable with the draft.(c) Satisfactory agreement is observed between theoretical and experimental predictions, confirming the validity of the proposed analytical method.