In the previous paper, the authors proposed a method of analyzing the strength of framed structures by means of elastic-plastic hinge method to save the computing time and simplify the analysis. The equivalent moment versus rotational angle relationship of an elastic-plastic hinge is obtained by elastic-plastic beam theory applied to the part between elastic-plastic hinges. In this paper, generalized elastic-plastic hinge method taking into account of the effects of shearing force and the round corners of deep web frames superposing to the effects of the bending and axial force is developed, showing several examples of its applications. And it is shown that the elastic-plastic failure loads and load〜deflection curves obtained by this method are practically agreed well with the values obtained by Nitta's experiments.

抄録全体を表示

Great parts of ship construction are consisted of reinforced plates with stiffners. In application of welding to fabricate them, the shrinkage of welded portion may usually produce distortion and residual stresses in each element of plate structure. Such initial imperfections may be decisive factors for structural strength or ultimate strength of stiffened plates subjected to compression. Several significant studies were already completed on ultimate strength of thin plates with stiffeners. This paper presents the relation between ultimate strength and initial imperfections of stiffened plates subjected to in-plane compression which are consisted of comparatively thick plate as used for ship structure. In order to investigate the collapse mechanism of them, the deformation, the extended state of yielded zone and the stress distribution in each structural element are calculated by finite strip method.

抄録全体を表示

From about ten years ago, many papers have been published on the theoretical analyses and full-scale measurements of the fore-and-aft vibration of superstructure. As a result of these papers, it have been cleared that we need to consider the effects of the elastic rotation at the base of superstructure, those of the coupling with the vibration of dodger, etc.. In this paper, the authors have studied the phenomenon of the fore-and-aft vibration of superstructure paying special attention to the coupling with the vibration of dodger. Besides, they have studied the effects of the struts supporting dodger. The assumptions for the analysis of this paper are as follows: a) Both superstructure and dodger are treated as a beam taken the effects of bending, shear flexibility and rotary inertia into consideration. b) The coupling effect with the hull vibration is not considered. c) The base of superstructure is supported by the rotary spring. d) The strut is replaced by the mass-spring system. After a study under these assumptions, the following results have been obtained. 1) When f_D and f_S, the frequency of the non-coupled vibration of dodger and superstructure, have close value, the lower one of them become more lower, and the higher one become more higher, owing to the effects of coupling. 2) The mode curves of both superstructure and dodger obtained by the calculation of this paper have showed a good agreement qualitatively with the results of full-scale measurements. 3) The struts fitted between middle and free end of the dodger are considerably effective in regard to increasing the frequency of the coupled vibration. 4) The struts have considerable influence upon the mode curve of dodger.

抄録全体を表示

In the recent research analizing propeller performance characteristics, great effort has been made to the unsteady effect of a wake. The author has investigated the method to evaluate the unsteady effect on the vibratory propeller shaft force for practical design purpose, which is outlined as follows. The circumferential fluctuations of thrust and torque are calculated by the quasi-steady analysis by using the propeller open water diagram, in which the axial and tangential wake components are taken into account. The circumferential fluctuation of thrust is transformed into the circulation fluctuation of the quasi-steady lifting line, when the assumed radial distribution of circulation is given as a function of radial coordinate except the strength of circulation. The quasi-steady lifting line is transformed into the quasi-steady lifting surface by introducing the assumed chordwise distribution of circulation. The circulation of the unsteady lifting surface is solved at one point under the condition that the downwash flow on the blade in the unsteady flow field is same to that in the quasi-steady flow field. Vibratory propeller shaft force is calculated from the circulation of the unsteady lifting surface. In order to confirm the propriety of this method, the unsteady effects on the thrust and torque fluctuations are investigated numerically.

抄録全体を表示

In model test on full ships with blunt bow, large amount of added resistance is observed in the range of shorter wave length, where ship motions such as heaving and pitching are scarecely observed. This added resistance is considered to be caused by wave reflection at the hull surface of blunt bow, and it become more important for recent large full ships, because the length of encounter waves in a seaway becomes relatively shorter compared with ship length. A model test was carried out for a 210 KDWT tanker to investigate the effect of waves on ship speed, chiefly concerning the speed drop in irregular waves of smaller wave height and shorter wave period, corresponding to the sea conditions at sea trial. As a result, speed loss of the ship compared with the case of ideally calm sea is expected to be about 0.5 knots for sea state 4 with wave height of about 2 meters. Many trial data of full scale ship larger than 200 meters were analysed, and correlations between the added resistance and sea state were recognised.

抄録全体を表示

In the previous paper, the authors presented a theoretical approach to the self-propulsion test of a full ship, which utilized measured hull resistance and wake data for a model (L_<pp>=8.0m). In this paper, they investigate scale effect on propulsive performance of a full ship which consists of an actual hull form and an infinitely bladed propeller. In computing propulsive performance of the ship of different scale (L_<pp>=4m, 12m, 302m), the total resistance of the ship is obtained based on the three-dimensional extrapolator method using Hughes' line and the nominal wake distribution is obtained by Sasajima's method. Two kinds of skin friction correction (SFC) are mainly selected: zero SFC and SFC based on I.T.T.C. 1957 line (ΔC_F=0.0002). Contraction of the wake due to propeller suction is also approximately considered in the calculation. The frictional part t_f of thrust deduction fraction is assumed to be 0.015. Results are analysed based on the thrust-identity method assuming that the open water propeller characteristics have no scale effect. Following conclusions may be drawn; (i) Scale effect on thrust deduction fraction is generally small and seems to depend on wake, propeller load, hull form etc. (ii) Relative rotative efficiency is larger for a full scale ship than for a model ship. This may be due to large circumferential inequality of wake distribution for a full-scale ship. (iii) Quasi-propulsive coefficient has small scale effect, though propeller efficiency and hull efficiency have considerable scale effects. (iv) The rate of revolutions of the propeller and delivered horse power of a full-scale ship are estimated with good accuracy by considering SFC. (v) By using calculation method described here, the rate of revolutions of the propeller and delivered horse power at speed trials are estimated pretty well.

抄録全体を表示

There is few theoretical study on the variation of wetted length or area of a ship gliding on water surface in spite of its practical importance. To improve this defect of theory, the present report proposes a linear solution representing the elongation of wetted length at first. This linear approximation tells us fairly well the variation of wetted length in two-dimensional case. The foregoing theory considers only induced velocity but not induced surface elevation, so that profiles of the ship obtained may differs from the ones assumed to be. Thence, the equation representing the surface elevation is introduced, calculated in some cases of simple pressure distribution and found their interesting character. Finally, an example to calculate the variation of wetted area is shown by making use of a two dimensional linear solution representing the elongation of wetted length.

抄録全体を表示

It has been becoming a great important problem to predict the hydrodynamic forces and ship motions in water of finite depth, because of increasing dimensions of ships. The studies of ship motions in water of finite depth, however, have been limited comparing with those in water of infinite depth. It is therefore desired that the correlation works between theoretical and experimental investigation should be performed and extended to oblique waves on water depths smaller than twice the draft of the ship. In this paper, author measures the amplitudes of motions of tanker ship model with various heading angles in waves at a shallow water tank. The experimental results are compared with the results of theoretical calculation obtained by so-called "New Strip Method". It becomes clear from the above comparisons that the theoretical calculations according to New Strip Method agree approximately with the experimental results in oblique waves, and especially the theoretical and the experimental results with zero-advancing speed agree very well in beam sea condition.

抄録全体を表示

During past eight years, un expectable huge meteorological tides have occurred frequently. In this era, interval of rizing and ebbtide reaches maximum. This oceanographical event has appeared with the period of 177.10778 years, which is the period of encounter of the Earth and Neptune of 177.10446 years and also the period of encounter of the Earth and Moon of 177.06604. According to the spectral analysis of various oceanographical data, there are a number of the periods of solar and lunar ecllips such as the Saro's 18.03001 years or the Moton's 19.00023 years, so that we can prefer suitable range of annual data which should correspond to the period of ecllips.

抄録全体を表示

This paper shows the result of the model test for the flow vortex around bellmouth in tank, for which the following items were tested in the scale model. (1) To measure height and shape of air entraining vortex. (2) Mutual interference of vortex at double bellmouth. (3) Effectiveness of baffle plate against flow vortex. Judging from the above model test, the followings are concluded. (1) The height and shape of actual air entraining vortex is able to be estimated by the following formula. (i) For height: [numerical formula] For shape: h=-Г^2/8π^2gr^2 (2) When two bellmouths are installed in one tank, it is unnecessary to consider the mutual interference between each vortex. (3) The baffle plate is effective to restrain the air entraining vortex, and the face plate of bottom longitudinal in tank is too.

抄録全体を表示

Last year, D/W 445,000 T.U.L.C.C. which has horizontal main system instead of trans main system was built in IHI KURE shipyard. As horizontal main ship is very rare for us, to recognize the accuracy of the calculation method, we carried out the ship board experiments under hydrostatic loaded condition. In the experiments, deflection of ships' hull and horizontal ring in addition to the stress distribution of trans ring and horizontal ring were measured. As regards structural analysis, two ways of analysis were studied as follows. (1) 3 dimensional frame analysis→3 dimensional F.E.M. calculation→2 dimensional F.E.M. zooming calculation. (2) 3 dimensional frame analysis→2 dimensional F.E.M. zooming calculation. As results of experiments and analysis, the followings were obtained. In case of (1) the results of analysis are in fairly good agreement with measured value. Also we recognized that the second method has enough accuracy for practical-design, although the accuracy of this method is inferior to the first method.

抄録全体を表示

The statistical predictions of wave loads (vertical shearing force, vertical bending moment, horizontal shearing force, horizontal bending moment and torsional moment) have been made for a container ship of 175 meters length and the similar ships of different length, in order to find out the long-term trends of wave loads and to examine the design values of those. In the first place, the response functions of wave loads are calculated by the aid of the modified strip theory. Then, the standard deviations of wave loads are evaluated based upon the linear superposition theory, by using the calculated response functions and the formulated wave spectra for given sea conditions. Finally, the long-term predictions of wave loads are determined by the obtained standard deviations and the wave statistics of the North Atlantic Ocean. According to the systematic prediction analysis, the longitudinal distributions of vertical wave shearing force and horizontal wave shearing force, which are predicted with the exceeding probability of 10^<-6>, are investigated in relation to the ship speed, heading angle and ship length. The longitudinal distributions of vertical wave bending moment, horizontal wave bending moment and wave torsional moment, which are predicted with the exceeding probability of 10^<-8>, are also investigated in relation to the ship speed, heading angle and ship length.

抄録全体を表示

The authors present the method of estimating axial force induced on a ship hull in regular waves. And, the statistical predictions of wave axial force are made for a gigantic oil tanker of 310 meters length and the similar ships of different length, in order to find out the long-term trends of wave axial force. Firstly, the response functions of wave axial force are calculated by the aid of the presented method. Then, the standard deviations of wave axial force are evaluated based upon the linear superposition theory, by using the calculated response functions and the formulated wave spectra for different sea conditions. Finally, the long-term predictions of wave axial force are determined by the obtained standard deviations and the wave statistics of the North Atlantic Ocean. According to the systematic prediction works, the longitudinal distributions of wave axial force predicted with the exceeding probability of 10^<-8> are investigated in relation to the ship speed, heading angle and ship length.

抄録全体を表示

The decreasing side thruster effectiveness at non-zero ship speeds is a well known phenomenon. The author, in previous paper, also has discussed on this matter theoretically and experimentally. And we have understood the effect of ship speed on side thruster performance was significant factor in ship manoeuvrability operating thruster. And, it should be noted that the tendency for the thruster effectiveness to increase with increasing speed after reaching a minimum at a certain ship speed was confirmed experimentally. It will be considered that the flow field of reduced pressure region will exist in the intermediate range of hull and the circumference of the jet flow, therefore, the lateral force generated by the thruster will decrease in some degree because the jet of fluid directed normal into a mainstream of fluid will be bent into the direction of a mainstream. Accordingly, it seems that the bow thruster is an effective steering aid when backing, and the thruster should be located as forward as possible or under the bottom of keel. Simultaneously, for a ship required the dynamic positioning, a tidal current becomes a serious problem. On this problem, it is necessary to make clear the relation between side thtuster performance and drift angle of hull. Therefore, this paper dealt with the effect of drift angle on side thruster performance theoretically and experimentally. And the following conclusions may be reached. (1) There is no greatly effect of drift angle for the lateral force acting on a hull generated by the side thruster as compared with the effect of ship speed. (2) For the moment acting on a hull, there is almost no effect of drift angle. (3) For the analyses of ship motion operating side thruster, we shall be necessary to consider both the influence of ship speed and drift angle of hull as significant factor.

抄録全体を表示

A barge has been used for elimination or reduction of labour in loading and unloading work, or for the particular purpose. Recently, these ships also become growing more and more, and being full of a great variety. Because a barge generally is to be unstable on the course stability, various ways for stabilization have been considered. As one of the ways, we have well known to fit the skeg on aft of barge. In this paper, the skeg effect for the course stability on a barge is investigated experimentally by measuring the lateral force and moment acting on hull and skeg. And the types of skeg are selected as the following, (1) Mariner Type Skeg, (2) Deformed Type Skeg, (1) Slotted Flap Type Skeg. With these results, we may conclude that the lateral force acting on a barge increases as extending of distance between skegs but the moment decreases, and the difference due to skeg is very remarkably. We see that a barge with skeg becomes stable in order of Marine Type Skeg, Deformed Type Skeg and Slotted Flap Type Skeg. And we can't almost see the difference of the rotary derivatives in comparison with hydrodynamic forces due to the Deformed Type Skeg and Slotted Flap Type Skeg. However, the difference of static derivatives in oblique towing test, especially the value of N'_β, is remarkably. Then, it will be not necessary to consider the interference effect between skeg and ship's body on hydrodynamic derivatives in the case of extended distance between skegs. The most desirable method for the course stabilization in a barge will be to select the Slotted Flap Type Skeg, however, it will be noted the resistance of barge due to skeg also increase remarkably. Therefore, when applying these results to practical ship, we should have to consider the most suitable method for the course stabilization of a barge in connection with the lateral force and moment and the resistance increment of ship due to skeg.

抄録全体を表示

The maneuverabilities of two full ships are investigated by the model experiments. The principal particulars of the ships are almost the same except l_<cb> positions as shown in Fig. 1 and Table 1. From the general results of free running tests, the mean maneuvering characteristics of the two model ships resemble each other and seem to be unusual stable as frequently observed in recent full ships. The detailed analysis of free running tests and PMM (planar motion mechanism) tests, however, leads the following conclusions. 1) The motions of both model ships caused by some definite small rudder angle, can not be determined uniquely and involve small irregular yawing motions. 2) The hydrodynamic forces acting on the hull of ships in steady turning can be devided into two parts. One is the force proportional to the drift angle as an ordinaly ship has, and the other is some unusual force not depending on the drift angle but nearly constant. Anyway, this unusual force is not stable in small drift angle. 3) The conditions causing the unusual force are seemed to depend on the effective drift angle at the stern, the rudder angle and the propeller loadings. 4) To improve the maneuverability of the ship having such an unusual force, the enlargement of the rudder area may be useless, because it requires unrealistic large area. 5) The existence of an unusual force affects the thrust of the ship. 6) On ship A (fuller than ship B), two values of hydrodynamic forces are observed under a larger drift angle, and both values are seemed to be stable. This may be the reason of having two steady turning circles in a larger rudder angle.

抄録全体を表示