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This paper describes the motion characteristics and cargo handling efficiency of the Large-Scale Floating Coal Transshipment Station (LFTS). Indonesia is the main country supplying coal in the Asia-Pacific region, it is important to ensure stable coal supply to Japan. Because the topography of the seabed near East Kalimantan Island, Indonesia’s main coal production area, is shallow, it is difficult for bulk carriers to reach the coast. And then, Large-scale Floating Transposition Station for Loading Coal (hereafter LFTS) was proposed, which will be used as a transposition station between small coal barge coming down the river and bulk carriers stay offshore. By installing LFTS, improvement of coal transport efficiency is expected. As a previous study, the motion characteristics of LFTS using a catenary chain in its mooring system were grasped. However, LFTS can carry up to 500,000 tons of coal, and the draft of LFTS tends to change greatly depending on the coal loading conditions. Besides, the tidal difference in the sea area where the LFTS is installed is about 2 m, and the mounting position of the mooring system on the LFTS side moves up and down by about 10 m at maximum due to changes in the draft and tidal differences. For this reason, when the mounting position of the mooring system is in the lowest state, the mooring line is loosened and the horizontal force is reduced, and it is considered that sufficient restraining force is not exhibited. And, when the mounting position of the mooring system becomes high, the mooring line tension increases and the mooring line may break in some cases. Therefore, in this study, an attempt was made to use an elastic mooring line as a mooring system for LFTS. An elastic mooring line is a mooring line that incorporates a highly stretchable material between mooring lines that connect anchors and floating body. Even if the mooring line attached to the LFTS moves up and down, an appropriate tension always acts on the elastic mooring line, and it can be expected to suppress the oscillation of the floating body and prevent the mooring line from breaking due to excessive tension. However, elastic mooring lines are mainly used for mooring small structures such as piers and aquaculture facilities, but there are no examples where these mooring lines have been applied to structures over 500m like LFTS. Therefore, elastic mooring lines are adopted for the mooring system of LFTS, systematically calculated according to various setting conditions of elastic mooring lines, and it is grasped whether elastic mooring lines can be applied to LFTS, and the motion characteristics of LFTS moored by elastic mooring lines was also grasped.

Indonesia is the main country supplying coal in the Asia-Pacific region, and in order to secure a stable supply of coal to neighboring countries, efficient coal transportation is required. East Kalimantan Island in Indonesia is the main coal-producing area, but the sea around the island is very shallow and bulk carriers for transporting coal cannot approach the coast. And then, Large-scale Floating Transposition Station for Loading Coal (hereafter LFTS) was proposed, which will be used as a transposition station between small coal barge coming down the river and bulk carriers that stays offshore. LFTS has a two-dimensional extent, and because the bulkheads for separating coal according to quality are installed on the floating body, the rigidity is partially different, and the draft also changes greatly according to the coal loading condition. In this way, LFTS has different characteristics from Mega-Float, which was built in Japan in the late 1990s with the aim of realizing a floating airport, so it is important to clarify its structural characteristics. In order to grasp the stress distribution acting on the structural member in consideration of the influence of the interaction between the overall deformation and the local deformation of LFTS, an analysis in which the entire structure is modeled in detail is desired. However, because members such as the internal bulkheads are arranged in a complicated manner in LFTS, a model in which the entire structure is modeled in detail requires enormous calculation costs in both capacity and time, it is difficult to perform the analysis. In existing research, various models have been studied, but there remains a problem in setting boundary conditions that reproduce the interaction between global and local deformations. And then, in this paper, a new modeling method of LFTS that can be analyzed efficiently was proposed. And the occurrence of stress concentration in the structural members of the LFTS was identified by systematically changing the external force conditions such as the coal loading condition and wave load assumed during the operation of the LFTS, and performing LFTS oscillation analysis and stress deformation analysis. Furthermore, the occurrence of plastic strain due to large deformation was investigated. The stiffening method that efficiently suppresses the occurrence of plastic strain was studied for the locations where the plastic strain was identified by the above analysis. These results demonstrate the importance of modeling large floating structures with complex structures.

Several types of oscillating water column (OWC) type wave energy converters (WECs) are researched and developed in the world. They are floating types and fixed types. In case of a fixed type, wave-dissipating caissons could be replaced by WECs of an OWC type. In OWC types, installation of the projecting walls (PWs) is useful in order to improve power take-off (PTO) performance. In this study, a double-dissipating caisson was used as an OWC type WEC with PWs. A front caisson of the double caisson seems to be the area surrounded by PWs and a back caisson can be seen as an OWC. The paper studied the basic property of the primary conversion from wave power to pneumatic power from model tests in a wave tank. It was found that the wave height strongly affects the behaviors of OWC motion and air pressure. Finally, the primary conversion was affected by wave height. Besides, the concept of use of a double caisson was useful for the primary conversion over 80% evaluated using test data.