Masahide Takeda

Coupled motion between crane-barge, crane hook and shackle during wave motion

When the hook of a crane-barge carries loads under wave condition, it is important to estimate motion of the ship, the hook, and the shackle for work safety. The hook and the shackle motions are mutually combined motions between the crane-barge, the hook and shackle swing. In this study, analytical model for coupled motion between crane-barge, hook, and shackle was proposed and verified experimentally; by a crane-barge model and by double pendulum model. In addition, analytical study for the development of reduction of the hook and the shackle swing motion method was conducted. By this analytical model, we proposed a way of reducing the hook and the shackle swing on a crane-barge under wave condition.

A study on Wave Energy Absorption of Breakwater with OWC type Wave Energy Convertors

東日本大震災において原子力発電所が被災したことに より,自然エネルギーの利用が見直されている.振動水 柱型空気タービン方式(OWC型)波力発電装置は30数 年にわたる研究開発と実証試験が行われた実績があるも のの,発電コストが高いことから,開発が停滞していた. OWC型波力発電装置は,小島ら(1983)の波力発電ケ ーソンと同様,ケーソン前面に没水部が開口した空気室 を設けており,入射波によって空気室内に水塊が上下動 し,同時に空気室に設けられたノズルを通して空気流が 生じ,この空気流によって空気タービン発電機を駆動す る.この課題は,エネルギーの1次変換効率(入射した 波エネルギーと空気室内の圧力と水位変動から計算され るエネルギーの比)が,波の周期が共振周期を外れると 急減する点であった.そのため共振する周期帯を広げ, 発電出力向上を目的として,図-1に示すような法線直角 方向に突出したプロジェクティングウォール(以下, PW)と呼ぶ壁構造を空気室の前面に設置した.本研究 では,PW-OWC型の波力発電装置を取り付けたケーソン の発電効率について,中規模と大規模の水理模型実験に より検討した.

SAND DEPOSITION CHARACTERISTICS OF THIN SAND CAPPING IN SHALLOW WATER

There are terrible problems that the organic sediments on the sea bed destroy the ecosystem all around the closed water. Generally, the two improving methods for the bottom sediments which target such the organic sediments are executed. The one is a dredging method which removes them outside, and the other is a capping sand method which covers the sea bed with the sand. This paper describes the sand deposition characteristics of thin sand capping when the sand was dumped by either a backhoe or a grab bucket into shallow water, because the construction demands the sand piled up as thinly and uniformly as possible. They were clarified through the field research at our construction site. Finally, the average layer thicknesses were almost equal to the planned layer thicknesses in any case of the dumping either the dredged sand or the pit sand. The coefficient of variation of the layer thickness became larger as the planned layer thickness decreased. Thus in the thin sand capping, it found that we have to set more surcharge for the quantity of sands, because the error of layer thickness would grow.