At the reclamation of a coast, a floating unit besieging a sand transport boat is built for the prevention of water pollution. A movable gate is equipped at the aft end of the floating unit for the access of sand transport boat. This floating unit has a large opening at bottom for the purpose of dumping the sand. Therefore, at the still water condition, the water level is equal between inside and outside the movable door. On the other hand, the water level difference occurs by the sand damping effect on the inside the floating unit. And, the wave load acting on the outside of the movable door. As for the coastal floating unit like this, there is no specific design rule. Therefore, it is necessary to establish the design load to start the design of movable door. In this paper, the design procedure from the establishment of load to the determination of structure is explained.
In advance of the explanation of structural design of the movable gate, the feature of the floating unit is explained in this section. The rough arrangement of the floating unit is shown in Figure 1. As shown in Figure 1, the floating unit is composed with U-shape section (see Sec.-A), bottom open section(see Scc.-B) and box shape section (see Scc.-C). A sand transport boat enter into the inside of floating unit from the aft end side. Therefore, when the movable Stern gate is closed, thc sand transport boat is surrounded by the floating unit. Additionally, a rubber curtain is equipped at the circumfercncc of thc bottom opening. The draft of the floating unit is controlled so that the curtain can reach to the bottom of the sea.
