In an attempt to apply the "Finite Element Method" to the analysis of the stress at the bracketed joint of deep beams, such as where the bottom transverse is connected to the longitudinal bulkhead with the vertical web frame, we, the authors, firstly built a simple scale model of such joint for the purpose of simulated experiment. The result thereof was carefully compared with the result obtained from the theoretical calculation made by the "Finite Element Method" and they were found to be very much the same. Secondly, at the end of a closer examination of both results, we arrived at an approximate calculation method, thereby establishing the fact that the stress at thetoe of bracket would get smaller as the toe assumes the "soft" shape.

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The structural damage, speed loss and hull shudder done by slamming are serious problems in seaworthiness of a ship. Investigations of slamming mechanism, impact pressure and prevention method of damage of large ship have been made and the rules of the classification societies has been suitably revised. Nevertheless, structural damage due to slamming are still reported. The slamming damage of bottoms of small ships are specially characterized of larger domain spreading to the midship, and of larger amount of push-up of the whole structure of bottom, compared with large ship of which the damage is of shell panel surrounded by the longitudinal and transverse girders. The slamming impacts are computed from the structural damage of the whole bottoms of five small ships and it is found that the whole structures of single bottoms of small ships are weak as compared with the double bottoms of large ships. The computation is based on the energy method of statical elastic theory. The other characteristic feature of larger domain of the slamming damage is originated in the larger value of speed length ratio. The pitching and heaving amplitudes of ships are calculated with the approximate formulas proposed by Prof. Tasai, and the normal and oblique impact pressures classified by Dr. Watanabe are calculated on the eight damaged ships. If the small ships is operated without speed loss, the pitching or heaving amplitudes of them are larger than the large ships, and then these facts may be the other characters of large slamming damage of small ships. The characteristics of the slamming damage of bottoms of small ships are clarified by these calculations.

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In recent years, steel hatch covers have been used in many cargo ships in order to obtain the highest loading efficiency. But it is a serious problem to select the normally operating hatch covers for ships with long hatchways, because in these ships the horizontal deflections, that is, opening and closing of long hatchways are sometimes over the allowable limits. The allowable limits are different on the kinds of hatch covers. In the other hand, the horizontal deflections of long hatchways are differently affected by such many items as length, breadth of hatchway, flexural rigidities of structural members in holds, loading conditions and others, and these deflections are compound with them of the longitudinal and transverse strength mechanisms. In this investigation, the horizontal deflections of long hatchways of standard ships different dimmensions and rigidities according to ship length have been computed and shown in curves. The standard ships have been settled from the mean data obtained from many practical ships of 40m〜90m length. Moreover, the many curves correcting deviations from the standard horizontal deflections of standard ships due to the increase and the decrease of many items affecting to deflections have been provided. These curves will be used to estimate the maximum range of opening and closing of long hatchway and effective reinforcement to settle the maximum range in the allowable limit in the stage of initial design.

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In this paper, we explain first a modification to the previous paper on the calculation of the shearing deformation of wing tanks, published by us two years ago, and then introduce a method of calculation for the case where the centre girder acts 100per cent effectively, in order to examine the influence of the centre girder on the shearing deformation of wing tanks. The main conclusions obtained by this paper are as follows: 1) When we carry out the calculation considering only the deviation loading, we need consider the term of F^L in the equilibrium condition of forces at the crossing Points of longitudinal bulkheads and end transverse bulkheads. [See Eqs. (2) and (3)] The influence of this modification is insignificant in the tanks of centre part, but fairly large in the tanks of fore and aft ends. 2) The shearing deformation of wing tanks become small in general by considering the effect of centre girder. In the numerical example of this paper, the amount of the shearing deformation has decreased 30〜40per cent at the centre parts of tank by assuming that the centre girder acts 100per cent effectively. As the degree of effectiveness of centre girder, however, is not 100per cent in an actual ship structure, the amount of decrease of shearing deformation do not become so large as this.

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Concerning to the hull painting in shipyards, especially in case of super manmoth vessels, the most important problems in these days are to perform it effectively and safely with the less period and painters and to get the higher quality of paint film for the longer performance. Taking the side shell in way of parallel part into consideration, Hitachi Zosen had studied about automatic airless spraying techniques and succeeded to develop the first automatic painting machine for the shell outside. The fallowings are now being expected after successful operation test on new building vessels. a) It is possible to get high quality of paint film by spray condition controlled regularly. b) It requires the least period and workers for painting c) It enables safety warks on shell outside. d) It can be used for the other purpose, such as for a smoll deck crane, for automatic surface preparation and so on.

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This paper gives results of a study made of the size and arrangement of water courses in cargo oil tank bottom to reduce the time required for cargo oil stripping of mammoth tankers. A formula representing the relationship between flow and level of water in bays marked off by longitudinal and transverse frames in cargo oil tanks was made, and calculations were made using an electronic computer. The results are as follows. 1) Stripping efficiency is higher in the conventional system (medium-sized holes are made uniformly in longitudinal frames in tanks) than in the concentrated hole system (large-sized holes are made in the longitudinal frames of the aftermost bay only in tanks). 2) The stripping efficiency can be greatly increased by increasing bellmouths in number. 3) The trim of the ship is highly effective in raising stripping effciency, and it is desirable that the largest possible trim is provided to increase the stripping efficiency.

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The Variable Suction Angle Valve is a new-modeled valve which is to be fitted at the end of cargo oil suction pipe on tankers, and has a variable suction area to meet with the flow rate required. Recently during past few years, the tankers became larger and larger and also the cargo oil pumps increased their pumping capacity. Accordingly the larger-sized suction bellmouth came into our special consideration. As one of rationalization of the cargo handling system of the tanker, the authors developed this new "Variable Suction Angle Valve", and two mammoth tankers equipped with these new type of suction valves have been built in their shipyard for Japanese ship owners. By adopting these valves you can expect following merits; 1. Stripping pipe lines can be ommitted and no inconvenience can be found in stripping operation. 2. Huge bellmouth is not required but the sucion mouth can be easily accommodated between bottom longitudinals. 3. The number of cargo valves which is hydraulically remote-controled can be decreased and cargoing operation more simplified. 4. Maintenance and inspection of the cargo suction valve can be made easier because this Variable Suction Angle Valve is more compact than the ordinary gate valve. 5. Cargo oil can be unloaded quicker than usual tankers which are not equipped with the Variable Suction Angle Valve.

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To prevent explosion and the forming of sherbet-shaped ice, L.P.G. (Liquified Petroleum Gas) tanks in low temperature systems are air-purged and dehydrated by the charging of N2 gas just prior to the loading of L.P.G. gas. To reduce the volume of N2 gas and save the port time for loading of L.P.G. gas, we have been dehydrating L.P.G. tanks by using special dehydration machines such as Lituium chloride (Licl) dryer prior to charging N2 gas in shipyrds. We have studied and developed a new way of dehydration by using compressed air in the shipyard and have applied it to the L.P.G. tanks of a 53,000 deadweight tons L.P.G. & oil carrier built in Jnne. 1966. This method is more effective than the conventional one and also can be applied to reduce humidity in general tanks and to facilitate painting of same. The Main Conclnsions are as follows. 1. General tanks can be dehydrated down to a humidity almost the same as that of the compressed air at the air chainging ratio of 2.0-2.5 M3/M3. Actually we could get a dew point of-1-5℃ at the changing ratio of 2.1 M3/M3. 2. The compressed air is very useful for tank painting. It prevents tank snrface from sweating. 3. The compressed air is available very easily and it costs much less than the conventional method in shipyards.

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波浪中の不規則な動揺がほぼ定常的な共振動揺とまつたく任意の瞬間に発現する自由動揺の二種から構成されていることはよく知られている。とくに沿岸航路の小型船舶では波の卓越周期が船の固有周期に一致していることが多く,このとき両者の位相差はπ=180°になるときが多い。これは復原性の見地からはつねに安全性が保有されている結果となつている。本文は観測資料に基きこの事実を解析したものである。

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台風中心の海洋波生成係数および吹送率を沿岸観測資料を基礎にしてStokes波理論を展開して推定した。眼縁ではとくに岨度が高く,吹送流を大きく,このため船舶は共振が不可能なほど速く流されるとともに,数分以上の長周期波動のため定常風圧傾斜が長く持続する。台風が移動するとき周囲の暴風域に高い波を随伴しているがその分布は物理的には熱伝導と同種の現象であつて,その特性は冬季寒冷前線の波況分布から解析される。

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When launching a medium size vessel, considerably big in comparison with narrow Onomichi Channel, it is necessary to know whether the launching will cause any damage to the opposite side with the waves and rising sea water or not, in addition to the study of inherent many problems involved in safe launching. To investigate the probable effects caused by launching, the authors carried out experiments using models in parallel with measuring the effects caused by the several cases of actual launching. Then, the authors realized the values of the rising water level at every experiment and actual launching came to almost the same tendency, and this enabled us to figure out certain ratios at several places where damage might happen. Thus, the following formula which shows the maximum rising water level caused by launching has been developed. H_w^2=C{1.42+0.00165(x-200)}×0.202×10^<-13>×(14.0-d)d^3B^3V_s^4×e^<(54.8-5.81(x-200)(3500-4x)×10^<-5>)/(14.0)> H_w: Max. rising waters level (m) C: Coefficient at several places where damage might happen. x: Distance from end of berth to each place (m) d: Max. aft draught (m) V_s: Max. launching speed (m/s)

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In this paper, dividing hydrodynamically a ship running straight in calm seas into three parts, i.e., hull, propeller and rudder, the author derives the fundamental equations to solve the performance characteristics of the respective parts taking account of the interference of them and the effect of free surface of water.

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In the previous papers, the authors made some statistical investigations of bow bottom emergence of a ballasted bulk carrier in rough seas. Here, they present the results of a study on determination of fore and after draughts of ballasted bulkcarriers in rough seas with consideration of the criteria of slamming and propeller racing. The authors carried out the theoretical calculations of response operators of relative bow motion and relative stern motion of a bulk carrier selected as a typical ship form, in regular head waves under nine different ballasted conditions which were determined by combining three different fore draughts and three different after draughts. Then, they estimated theoretically the probabilities of occurrence of slam and propeller emergence among rough seas corresponding to the average sea states of the North Atlantic under various wind velocities, by using the derived response operators and the wave spectra which were assumed so as to represent the sea states realistically. And finally they made the estimation of the critical fore draught with respect to slamming and the critical after draught with respect to propeller racing. These theoretical estimations were made for geometrically similar ships having different lengths. The critical fore draught and the critical after draught are given in charts as functions of ship length with parameters of sea state and ship speed. By investigating those results, the following facts were found: (a) When the fore draught being constant, the larger after draught causes little increase of relative bow motion and probability of occurrence of bow emergence or slam. Therefore, the frequencies of bow emergence and slam are almost dependent on the fore draught only. (b) When the after draught being constant, the larger fore draught causes a little increase of relative stern motion and probability of occurrence of propeller emergence. Therefore, the propeller emergence is almost dependent on the after draught only. (c) The probabilities of occurrence of slamming and propeller racing decrease considerablly with increase of ship length. (d) The probability of occurrence of slamming decreases considerablly with decrease of ship speed, whereas the probability of occurrence of propeller racing does not, but somewhat increases with that. Probabilities of occurrence of slamming and propeller racing calculated by the theoretical method are largely dependent on the values of threshold velocity and critical propeller emergence respectively. Therefore, the reliabilities of calculated probabilities are almost dependent on the reliabilities of the values of those. It is necessary to make further studies on threshold velocity and critical propeller emrgence. However, the results obtained here would be available for the purpose of determination of fore and after draughts of ballasted bulk carriers in rough seas at the view point of comparative design for ships of different lengths.

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In this paper, general theory of anti-rolling tank with free surface, such as flume stabilization system with center tank or perforated wing bulkheads, is treated. It is, also, shown that the action of this type is fundamentally same with the Frahm's tank of U-tube.

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We have had some reports of the Western Reseach Commitee of Ship Structure concerning with the damages of cracks, on the stiffened bulkhead at the neighbours of the joint with stiffeners. One of the causes of these damages is the fatigue fracture which is caused by the vibration of the plate, associated with the torsional and bending vibration of the stiffeners. To make this cause clear, we have to know the stress distribution on the stiffener when it is vibrating. In a preparation of this attempt, this report shows the natural frequencies and stress distribution of the beam, both ends are free supported, and attached with the added mass of angle section corresponding to the cross section of the stiffener, by applying the dynamical equation of slope deflection method. We defined the following three nondimentional parameters, K_M=m_s/m_b, K_R=Θ_A/(m_bl^2), K_G=(m_sy_A)/(m_bl) where, m_s: mass of the added body, m_b: mass of beam at the length l, l: corresponding to the stiffener space, Θ_A: mass moment of inertia of added mass around the joint, y_A: eccentricity of the centre of gravity of the added mass at horizontal direction. These value of the actual vesseles are shown in Fig. 1 and Fig. 2. For four examples, shown in Table 1, the eigenvalue βS calculated are shown in Fig. 6 and mode and stress distribution is shown in Fig. 7〜Fig. 10. This made it possible to conclude that: 1. For the K_M and K_R corresponding to the ordinary stiffened structure of the vessel, in the first and the second mode, added mass acts as the concentrated load and concentrated moment respectively, and in the third or more mode, will be almost fixed. 2. Accordingly the stresses produced at the neighbours of joint is considerably large. 3. Assuming the fatigue limit as σ_F=22kg/mm^2, when the maximum dynamical stress of the vibrating beam is that fatigue limit, the ratio of the maximum deflections of the beam to the stiffener space are 2.88×10^<-2>〜7.25×10^<-2>, 7.00×10^<-2>〜2.0×10^<-2>, 4.0×10^<-3>〜7.7×10^<-3> for the 1st, 2nd and 3rd mode, respectively, as shown in Table 2. 4. But the assumed fatigue limit is the value in the ideal condition, and so this value will decrease to 1/2〜1/3 in the actual conditions, considering the shape factor, the change in quality of materials by welding and the influence of corrosion. Thus it is conceivable that the fatigue fracture of the stiffened plate may be caused by local vibration of ship. We are now analyzing the dynamical stress distribution at free vibration of the beams having many added masses, and the actual stiffened plate. We will report in the next papers.

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General equations of motion have been derived for the transient vibratory response of a beam with attached sprung masses. Qualitative observation has been made for the special case of uniform beam. As a numerical example the transient response of a topedo boat has been calculated taking into account the bottom shell as local vibratory structures. The main conclusion is that higher mode components in the transient response whose frequencies are higher than the frequency of the local system decreases when it is attached, while the response of the mode whose frequency is nearly equal to that of the local system are magnified by existence of it.

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The paper considers the eigen values and the corresponding modes of the vertical vibration of the rectangular hull like the plan of a mammoth tanker taking into account athwartship flexibility. For confirming existence of the spectra other than that in a simple beam, some experiments by use of wooden model are attempted.

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In ship structure, there often appears that two stiffeners are butt welded to both side of a plate such as deck plate or horizontal girder on bulkhead. If these stiffeners are welded each other with a certain discrepancy, it is thought that the fatigue strength of the butt joint is much reduced. In this report, the author describes on a fatigue test which shows the relation between fatigue strength and discrepancy ε. Results are: 1) S-N curves are flat till N=5×10^2〜10^3 and then fatigue strengths are rapidly reduced. 2) The influence of discrepancy is more evident in high cycle range (N=10^3〜10^5) than in static tests.

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Recently, it has been reported that the web plates of large ships, especially with a hole, are damaged by shear buckling. For the ratio of the Thickness to the breadth which is as usual in actual ships, buckling will occur within the plastic range. So, the authors have reserched experimentally the effect of the ratio of hole diameter to the plate dimention, the aspect ratio, the existence of weld joints and the method of stiffening for the pierced parts, on the plastic buckling strength using simple square plates. The conclusions are as follows; 1) The effect of aspect ratio, the ratio of hole diameter to the plate dimention, is represented by the following empirical farmula, τ_<cr>=τ_<cr1>[1-(-0.06β+1.09)D/S][-0.24β+1.24] where, β: aspect ratio D/S: hole diameter/breadth of plate τ_<cr1>: shear buckling stress of plate (β=1.0, D/S=0.0) τ_<cr>: shear buckling stress of any pierced plates. with the limitation {1.0≦β≦2.11 0.0≦D/S≦0.5 0.0128≦t/s≦0.0170 2) Approximate caluculation based on the stowell's theory verified the above mentioned empirical formula. 3) Strength of the plate with truck type perforation can be argued by the longer diameter. 4) Shear buckling strength of the model specimen composed of stiffener, double bottom plats is higher than the strength of simple plates. 5) The ratio of reduction of shear buckling strength due to existance of slot, weld joint are as follows; slot 10〜20%, butt joint: about 30% lap joint about 30%, lap joint in stiffening side about 6%. 6) As for the stiffening method, stiffener type is better than the ring type.

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任意の応力〜歪特性を有する材料からなる梁に関する一般の不静定問題を解くことは,弾性梁や極限解析のような理想化された場合以外は基礎方程式の非線型性のため,それらに較べて一般に困難であり1 spanの両端固定梁などの簡単な場合以外の研究は見当らない。これに対し著者の一人は鋼材について弾性域および塑性域における応力〜歪特性を,電子計算機により数値的にSimulationを行ない.これをもとにして荷重履歴も考慮した弾塑性梁の応力および歪の解析を行ない,その結果を前報告において述べた。この方法は原則的には梁の不静定問題にも適用が可能であり,両端固定梁等の例についての解法を示したが,その際用いた中型の電子計算機(九州大学設置のOKITAC 5090H)によれば1回の計算に数十分以上を必要とする場合が多く,しばしば実用的でない例に遭遇した。本報告では実用的な設計問題に応用することを目的として材料が焼鈍された状態から出発して増大する荷重を受けた不静定梁に生ずる最大の応力,歪および撓み等を求めるため変形理論を用いた鋼材の応力〜歪関係を出来るだけ一般的な表現が出来る形式の数式で表わし,これに基づいて軸力のない場合の梁の一般的な曲げモーメント〜曲率関係を求め,撓みやその勾配を求めるため出来るだけ数式的な積分を行なつて数値積分を行なう部分の減少を計り,所要計算時間を減少させることを試みた。これにより一般にLoopによる反復計算時間の短小化を実現し,多次不静定弾塑性問題の解法の実用化を計つたものである。また今後更に大型の電子計算機の導入により前報告で述べた応力履歴を考慮した一般性のある純数値的方法をこのような多次不静定問題に適用する際にも,この方法は部分的にRoutineの一部として使用することが出来,特に高次不静定構造に対する大型高速電子計算機の活動可能な範囲を更に拡大するためにも役に立つものと思われる。

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Due to the recent tendency of enlargement of ship size, and also machinery erection and outfitting works at early construction stage, launching weight has increased year by year. At last launching weight reached to 21,558 tons at the launching of m.v. "BERGEBIG", which had successfully launched at our Hitachi Innoshima Shipyard on 22nd of November, 1965 using semi-8 feet launching ways, which had been developed by our shipyard to meet increase of launching weight. Mean pressure on fat at this launching is 28.63t/m^2 which, we presume, is the highest value in fat launchings experienced so far in the world, at least in Japan. Here, we report our experiences on the launching in which we have mainly indicated following three points; 1. There was not any hindrance on the launching ways and their constructions even under such high pressure. 2. Frictional coefficients of fat at both during sliding and just before starting conditions were nearly same as our empirical value derived from the result of launchings of lesser pressure. There was not any peculiar change in frictional coefficients due to high pressure. 3. Web plates of bottom transverses in way of cargo tank part just above the launching ways slightly yielded to hollow in spite of their previous reinforcement. Attention must be paid for such part, especially for the tanker whoes bottom transverses are arranged in wider space and comparatively thin in their thickness.

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