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

为预测超大型海上浮式结构在波浪中的水弹性行为，进行了理论和实验研究。项目成果总结如下：1。结合干模展开法和混合积分方程法，编制了预测VLFS波动水弹性响应的计算机程序。通过模型试验测量了VLFS模型在常规波浪槽中的水弹性响应。该模型由许多铝板组成，铝板附着在一个裂开的聚乙烯块上，以提供浮力。除了不同弯曲刚度和质量的模型外，还测试了在波前边缘有垂直壁和水平淹没板的VLFS模型，以研究减少VLFS边缘附近大挠度的可能性。从一系列试验中得出以下结论。(a) VLFS模型的运动响应具有高阶弹性模态特征。随着波频的增加，除了波前边缘附近有较大的偏转外，响应幅值急剧减小。(b)在波前边缘加装垂直壁面或水平淹没板，可以减小边缘区域的大挠度。随着波频的增加，其效果更加明显。当VLFS的长度超过波长的5倍时，通过附加与吃水长度相当的边板，将响应减小到约2/3 ~ 1/2。(c)在理论预测和实验预测之间观察到令人满意的一致，证实了所建议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.