Establishment of Design Procedure of Semi-submersible Type Very Large Floating Structure

点击翻译按钮获取中文摘要

Initial design procedure of Very Large Floating Structure (VLFS) was proposed compiling knowledge and research results obtained so far. Assuming that the design procedure is proposed for a floating airport to be installed offshore of Japan, environmental conditions used for design of safety and functionability were determined. Initial design was carried out and principal dimensions of airport were determined. The dimension were determined to satisfy the requirement to introduce jet airplane to isolated islands.Basin experiments were carried out using a scale model which is elastically and dynamically similar to real structure, and the response characteristics were clarified. Simple numerical model was proposed for dynamic response of VLFS. This is a simple model, a beam on elastic foundation, but basic response characteristics of the structure is expressed by this model and relations between major parameters and dynamic response were clarified. Furthermore it was made clear that response estimated by this model gives upper limits of that of real structure. These parameters are proposed as design parameters of VLFS.Using the design parameters, an optimal design procedure was proposed. In this procedure resonance is avoided imposing constraints on frequency response and weight of the structure is minimized. Effectiveness of the procedure was confirmed through application to design and analysis.Through initial design, it became clear that the wind drag force occupies major part of the total drag force. Drag force induced by wind is very important in the design of mooring system of the VLFS. A series of wind tunnel experiments were carried out in critical Reynold's number region. Drag force characteristics which act on columns and deck were clarified and multi-step reduction phenomena of drag force was observe and data for estimation of drag force was obtained.