Wind Loads on Columns of Semi-Submersible-Type-MegaFloat

摘要

When ocean space utilization is considered in Japan, a Semi-Submersible-Type-Mega-Float is a promising option. Calm waters suitable for Pontoon-Type-Mega-float are limited to the internal waters. But there are many needs to install Mega-float at more rough sea such as the mouth of bay and the open sea. A research was carried out to study possibility of Semi-Submersible-Type-Mega-Float in such a waters. A Semi-Submersible-Type-Mega-Float which serves as a airport for local air transportation of isolated islands was assumed in the research. Principal dimensions of the airport were determined assuming that it is used as a floating airport to be installed offshore Japan and designed to satisfy functional requirements when a middle size jet airplane lands on the airport. From this research it became clear that the airport itself can satisfy strength requirement but the wind drag force acting on the structure becomes significant and cause a problem in the design of the mooring system. It became necessary to study behavior and formulate estimation method of wind force acting on the structure in the high Reynolds' number region. A series of wind tunnel experiments were carried out to clarify drag force characteristics and interaction between the columns in the high Reynolds' number region. Multi-step reduction phenomena of the drag force coefficient was observed and data for the estimation of the drag force was obtained.