Geometrical Accuracy Management of Very Large Floating Structures

摘要

The new technology of construction of Very Large Floating Structures called Mega-Float has recently received public attention due to its possibility for better utilisation of ocean space. However, in order to construct the Mega-Float, there are some issues to be solved. Because it is too large to build at any building dock or other site on the ground, it can be constructed only by joining many floating units together at the site at sea. Some advanced technologies such as joining operations in waves, under-water welding technology and accuracy management for the construction operations at sea are necessary. Technological Research Association of Mega-Float (TRAM) was established in 1995 and has carried out research and development for Mega-Floats, which are several kilometres in length, and with a lifespan of 100 years. Also, TRAM has developed the construction technologies, and established them through construction and dismantling of two experimental floating models. Fig.1 shows the floating airport model under construction. During construction of the experimental floating models, we found out it is very important to estimate the deformation of Mega-Float precisely. This paper is regarding the thermal deformation and welding deformation. Comparisons between experimental results and estimation by FEM analysis are shown, and as a result, we show it is possible to precisely estimate the thermal deformation and welding deformation of Mega-Float under construction. Moreover, we show FEM analysis can provide the procedure to minimize geometrical inaccuracy and misalignment among floating units by controlling the shapes and the placing position of the floating units.