Since 1970, semi-submerged containers have been investigated in the Ship Research Institute. The knowledge of the hydrodynamic characteristics of a shallow-running flat submerged body has become essential for the hull form design of a large semi-submerged ship. Through the study on separation of the resistance components of three flat submerged bodies and an elliptic body of revolution, following problems are discussed.
a) Unexpected large resistance of shallow-running submerged bodies (Fn>0. 25) results from generation of the vortices behind ship.
b) The resistance due to the vortices is obtained as viscous resistance depend on Froude number because of the vortices behind submerged bodies mainly originated in the current of free waves.
c) Wave making resistance of submerged bodies is seriously affected by the vortices.
d) Flow symmetrization between the up and down side of the shallow-running flat submerged bodies significantly contributes to reduce the resistance.

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Series tests were carried out to investigate the relations between hull form and wave resistance obtained by wave pattern analysis. The eleven models selected were composed of four series, namely ∇/L³-series, B/d-series, C_p-series and l_cb-series. The hull characteristics of these models are as follows :
(1) Water lines meet with base line tangentially at both ends.
(2) Frame lines are consisted of Lewis forms.
(3) Sectional area curves are equivalent to Tchebycheff's functions.
(4) Models are symmetric about midship except for l_cb-series.
The wave pattern measurements were performed simultaneously with ordinary resistance tests, and wave data were analyzed by the method of J. N. Newman. The test results of wave resistance, residual resistance and sinkage for each series were presented in non-dimensional form. Form factors were derived from these results by deducing wave pattern resistance from residual resistance. Some consequences of experiments were compared with the results of linearized theory, which may be usefull information for the basic hull form design.

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Computational investigation was made on characteristics of incompressible turbulent boundary layers on a shiplike body and on two kinds of two-dimensional bodies. One of the latter bodies had nearly the same contour as one of the streamlines on the three-dimensional body. The other had pressure distribution on it the same as along the streamline on the three-dimensional body. Momentum thickness, shape parameter and surface cross-flow angle of the boundary layer were calculated for the three cases and factors contributing to variations of these quantities were analyzed.
Comparison between the results for the three cases revealed the following facts. The rate of growth of the momentum thickness in the region of deceleration was promoted mainly by the streamline convergence which was absent in two dimensions. In this case the development of the momentum thickness became larger in the three-dimensional boundary layer than in the two-dimensionalone. The surface cross-flow angle near the rear stagnation deviated rapidly in the direction of the center of streamline curvature due to the curvature and convergence of the three-dimensional streamline.

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In this paper, the specific features of Akashi Ship Model Basin are described.
One of its features is that this reseach institute is the joint venture of two independent enterprises, and another one is automatic system which has been employed to a great extent.
Automatic system is represented by the software system for carrying out automatic tank test and computer-controlled ship model shaping system.

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This report proposes an approximate calculus for calculating normal part of the thrust deduction.
The basic integral equation of the present method is deduced from hydrodynamic assumptions of the pressure field about a hull and a propeller.
The author calculates normal part of the thrust deduction for various hull-forms by the present method, and compares the calculated results with results calculated by the potential flow method or results of the self-propulsion test. These comparison show that the present method is reasonable.
Calculating time consumed with the numerical method in the present method is less than that in the case of the potential flow method, and application of the present method to the more practical hull-form is easy.
Consequence of some numerical results shows that normal part of the thrust deduction is the largest part of the thrust deduction.

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The application of ducted propellers to large full ships has recently been intensified. However, these highly loaded propellers using an accelerating duct are susceptible to the occurrence of propeller cavitation. Therefore, in adopting the ducted propeller for a 280, 000 dwt. tanker, the M. S. 'THORSAGA' the authors conducted model tests in the cavitation tunnel and in the NSMB depressurized towing tank (vacuum tank) to study the ducted propeller cavitation. Also full scale cavitation observations were carried out succesfully during the sea trials of the M. S. 'THORSAGA', using a T. V. camera scanning the propeller. The observed results were recorded on video tape.
Results of the cavitation tunnel and vacuum tank experiments are presented together with the full scale cavitation observations, and the correlation between the model and full scale observations is discussed. The model test procedures are also described.
The correlation of the vacuum tank cavitation pattern with the full scale observations can be seen tc be satisfactory, although the extent of the full scale cavitation is slightly larger than observed on the model propeller. Moreover, the vacuum tank/full scale observations appear to have a better correlation than cavitation tunnel/full scale observations. This difference is regarded to be mainly due to lack of simulation of transverse velocity components and the propeller-hull interaction in the cavitation tunnel. Thus for large full ships, the presence of the ship model in front of the propeller during the cavitation tests seems to be very important.

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The fluctuations of the propeller load of a high speed container carrier oscillating on the swells have begun to come into question as it's speed becomes higher and higher. The measured results of model experiments in the self-propulsion test in oblique regular waves have shown the fluctuations that amount to be 50% of mean value, at the wave height 1/40 of model length. These phenomena of remarkably great vibrating bearing propeller forces have already been pointed out by Hoshino et al., Schwanecke, Vedeler and Lipis.
In the present work, the author attempted to estimate the fluctuations of propeller load applying the unsteady aerofoil theory and the theoretical calculations of ship motions based on the New Strip Method in oblique regular waves. The fluctuations of propeller load were shown to consist of three harmonics for one blade, namely encounter circular frequency ω_e, the frequency compounded by circular frequency of propeller revolution ω_e±Ω. For the total blades only one harmonic ω_e was shown to act. Predominant components in the amplitude of these fluctuations have been made clear that wave orbital motion contributes exceedingly, and then in the order of surging and pitching motions of a vessel.
Theoretical calculations by the present method have been compared with the above mentioned model experiments, and shown to be in good agreement with them, except the region of short wave length where the fluctuations of fluid velocity are affected by the deformation of waves due to the presence of the vessel. The thrust fluctuations of loads acting on one blade and that for the total blades as a whole propeller were simulated by the computer, the results of which are similar to some experimental results measured by Takaishi and others.

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In recent years, the utility of Transient Water Wave has been proved for ship response tests and for the research of wave impact on ships, etc. Although it is apparent that its utility depends on Linearity, but the significanse of non-Linear effects had not been recognized.
In this report, introducing a new type averaged Lagrangian, the author shows the non-Linear character of finite amplitude Transient Water Waves and the controllability of it.

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It has been shown theoretically by Bessho that it is possible to absorb a train of regular waves passed a floating body if its motion is properly controlled. It has also been shown experimentally by J. H. Milgram that in a specified case, the “perfect wave absorption” could be realized.
In this paper, the authors rearrange Bessho's theory and show that when an incident wave is diffracted by a fixed body, the height of symmetric wave system and asymmetric wave system which are fundamental components of the reflected and the transmitted waves is exactly one half of the height of the incident wave, and show that this relation is valid independent of the form of the body. They also show that this relation holds in the case when the body is allowed to move provided the body is of symmetric.
Making use of these relation, the authors show theoretically and experimentally that it is possible to absorb completely the energy of an incident wave by actively controlling the motion of a floating body.
They also show that at the “wave absorption point” at which no reflected and transmitted wave exist, the work done by the mechanism which activated the body is negative and is equal to the energy of the incident wave.

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A method of calculating the wave induced pressure on the surface of an elongated body fixed horizontally in head sea waves is presented. Numerical results are given for the case of semicircular cross section and compared with measured results. Comparison is made also with the calculations by other theories such as the strip method and Faltinsen's theory. A consistent agreement with the experiment is obtained by the present method.

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The hydrodynamic forces on a circular disk as a shallow draft ship for the forced heaving oscillation in shallow water are investigated. The boundary value problem is formulated by the use of the concept of the surface distributed sources so that integral equations for the source densities are obtained. In the case of long waves, the problem is solved analitically. The numerical solution of the integral equations is found and the added mass and damping factor are calculated. The exciting forces on a fixed circular disk in an incident wave are calculated according to Haskind-Newman's relation. The influence of the shallow water effect on the forces is illustrated graphically and discussed.

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In the article [4], the authors have clarified that the hypercircle method is useful for estimating the added mass of two-dimensional cylinders with a rectangular or triangular section when vibrating in the horizontal direction very slowly. In this paper, the added mass of a rectangular cylinder floating on the surface of water and vibrating in the horizontal or vertical direction with a very high frequency is calculated by the same method also for the purpose of investigating the effect of the restricted waterway on the added mass.
As the result, it is concluded that the clearance between the side wall of the waterway and the nearer side wall of the cylinder has a considerable effect on the horizontal added mass, while the vertical added mass is affected remarkably by the clearance of water under the bottom of the body.

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Many methods for calculating the hydrodynamic forces on a rigid body, produced by its harmonic oscillations on a free surface have been presented since the analytically method was published by Ursell. Recently, these kind of hydrodynamic problems have been studied using the finite element method (F. E. M.).
It seems that F. E. M. can be available to solve the hydrodynamic problems which have been difficult to be solved by other traditional methods becauce of the bodies' complex geometries and their complex boundary conditions.
In this papers, as examples of the application of F. E. M. to these kind of hydrodynamic problems, the authors have calculated the added masses and damping coefficients for two-dimensional bodies and also for axi-symmetrical bodies. In order to examine the applicability of F. E. M., the numerical solutions by this method were compared with the solutions obtained by other analyical method, and a good agreement was obtained.
As a conclusion, it was found that the finite element technique was a sufficiently accurate and reliable method to solve the hydrodynamic problems of this category.

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In the previous papers, the authors applied the transient response method to pure heave motion, pure pitch motion and coupled motion and showed the effectiveness for ship research. The experimental results obtaind by this method, frequency transfer functions and hydrodynamic derivative coefficients, were affected by side wall effect due to the reflection from the tank walls of waves generated by motions of the ship model.
By using the Hanaoka's theoretical calculations on the angle of a travelling wave sector formed by motions of the ship model, Vossers & Swaan offered a practical chart on side wall effect in waves.
In this paper, the waves were measured near the oscillating ship model running in still water at a given speed and the relationship among the reflected waves, model speed, the ratio of tank breadth to ship model length and the frequency of oscillation was investigated.
The authors could certify that the frequency range in which the ship model would be influenced by side walls could be predicted practically by using the Vossers & Swaan's chart.

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The forced oscillation method is generally used to examine hydrodynamic derivative coefficients of the equations of ship motions. This method is to analyse the ship motions caused by known mechanical force or to analyse the hydrodynamic reactions caused by known displacement of ship in still water.
In this paper, however, the authors propose new forced oscillation method which uses water waves instead of known mechanical forces. This method has two merits. One is that hydrodynamic derivative coefficients can be obtained without using the apparatus for forced oscillation method, and the other is that the investigation of hydrodynamic coefficients from new aspect is possible, because they are obtainable in the field where water waves exist.
The results obtained by applying this new technique to longitudinal motions almost coincided with ones by conventional forced oscillation method, and its effectiveness was shown.
Moreover, the authors were able to examine the main terms of sway and roll in beam wave obtained by the above-mentioned technique expanded to lateral motions.

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Dynamic positioning control tests were carried out for a semi-submersible two-lower-hull type platform model in the simulated environment for offshore current, wind and wave in a ship model basin. Prior to the control tests, hydrodynamic characteristics of the platform and the propulsion systems were measured and computer simulations were made to obtain the basis for the design of the dynamic positioning control system. The results of over-all control tests indicate that the dynamic positioning control is duly practicable at the two-lower-hull type semi-submersible platform.

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Waves caused by steady ship motion are analyzed by the finite element method on the basis of the concept of the superposition of analytical and finite element solutions. The radiation condition is substituted by assuming appropriate radiating waves. Wave motions in a certain domain Ω^a around the ship is assumed as a linear combination of the radiating waves and certain finite element solutions.
The amplitude of the radiating waves can be determined by the condition of continuity on the surface of the domain Ω^a, which can be expressed as the form of a single collocation equation.
The finite element formulation can be developed by the same way as linear elastic problems, and its analysis can be performed easily by the use of general-purpose-programs for structural analysis. Numerical results obtained by the present method is compared with those by the previous authors, and they show good agreement.

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In many structural members, out-of plane stress due to bending and in-plane stress due to extension act at the same time. In the present paper, the characteristics for fatigue crack propagation and brittle fracture initiation from a through thickness crack in a plate under arbitrary combined extension and bending are analysed theoretically using ρ⁺-concept. Considering the stress balance within the plate thickness, the authors defined effective tensile plastic zone size (ρ⁺_eff) or effective stress intensity factor (K_eff) as a criterion of brittle fracture initiation and fatigue crack propagation. The effectiveness of this criterion were confirmed by brittle fracture initiation tests and fatigue crack propagation tests.

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A simple model of fatigue crack propagation is offered which takes the effeet of stress ratio into account. In the model it is assumed that fatigue crack propagation rate is proportional to the absorbed hystereisis energy per a stress cycle at the tip of a crack. The energy is calculated from stress and strain field around a crack. Stress distribution is determined by Dugdale model and strain field is done from the experimental results shown by some researchers. It is affirmed that the model can be applied to the experiments on several materials.

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The behavior of the fatigue crack under the narrow band random stress intensity factor was studied experimentally. It was found that stress intensity factor governs the fatigue crack growth rate under random load process as well as under deterministic load sequences, and the crack growth rate in the short range showed noticeable fluctuation while that in the long range was almost constant implying that Miner's rule could be applied for the crack growth provided that the constants were determined from random fatigue test.
A small digital system with a micro-CPU and the associated software developed for this study was found suitable for random fatigue tests.

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It is important to obtain the information on propagation of fatigue crack in ship hull structures for the prediction of service lives of structures subjected to alternating load in a corrosive environment. The effect of sea water on the fatigue crack propagation was examined for mild steel by using the center notched plate specimen and the slotted structural model. It was found that the correlation between the range of stress intensity factor ΔK and crack propagation rate da/dN for mild steel in sea water could be given in the same manner as the Paris's law, that is,
da/dN=c (ΔK) ^m,
where m is nearly equal to 3. 5 both in the environments of sea water and air, and C is a coefficient which depends on the environment and load frequency f. In the sea-water environment, C is affected remarkably by the frequency but slightly in the air, and it could be given by the following equation.
C=-Alogf+B
where A and B are coefficients which depend on the environment.
Correlations between the stress intensity factor and the crack propagation in the root of web stiffener and in the web plate of structural model were in good agreement with those in the center-notched plate specimen.
Finally, using the above mentioned corrosion-fatigue crack propagation law, fatigue crack propagation lives were calculated for the root of web stiffener and the web plate at the slot corner in the transverse web frame ring of the actual ship.

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In the first report, stress and strain distribution of a thick steel plate under uniform plastic bending in plane strain state was analysed, and a new method of bending test was proposed.
In this paper, bending stress and strain distribution of the plate in plane stress field was analysed and calculated results were compared with experiment ones, and some differences in bending stress and strain distribution between the two cases were discussed.
True stress and true strain relations of the material used in these analysis were obtained by tension test of wide thin plate and compression test of short round bar cut from the same material used in bending tests, and these relations were compared with Bridgeman's corrected one.
From these results, the following conclusions were obtained.
(1) Stress and strain relation by tension test of wide thin plate is more effective rather than Bridgeman's corrected one for analysis of uniform bending in the both cases.
(2) Bending strain in compressive side of the plate in plane stress field is a little smaller than one in plane strain field, but slope of bending strain distribution on convex surface of the plate in the both fields is nearly equal at the same bending strain level on convex surface of the plate.
(3) Bending stress on convex surface of the plate in plane stress field is smaller than one in plane strain field, and slope of bending stress distribution on convex surface of the plate in plane stress field is a little smaller than one in plane strain field at the same bending strain level on convex surface of the plate.
(4) Bending moment of the plate in plane stress field is a little smaller than one in plane strain field at the same bending strain level on convex surface of the plate.

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The behavior of the stretched zone and fracture initiation at the notch root with increase of the applied load has been investigated at various temperatures.
The stretched zone width is almost constant regardless of test temperatures when crack initiates by fibrous crack, while, in the case of cleavage initiation, it takes various values between the above-mentioned value and zero depending on temperature and plastic constraint.
When fracture occurs with plastic COD, the critical COD at fracture is reduced by the amount of stretched zone given by the preloading, while the effect of preloading on the critical COD is small when the COD mainly consists of elastic deformation.
The process of fracture initiation from the tip of 45° crack has also been investigated and it is found that the stretched zone width of 45° crack specimen is about the same as that in mode I.

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The effects of circular hole located near crack tip on deformation and brittle fracture were investigated analytically using F. E. M. and experimentally. It will be important to investigate these effects in relation to the significance of defects in welded structures.
Stress and strain distributions at the vicinity of crack tip were calculated for various locations of hole. The results showed that stress and strain between crack tip and hole become extremely large due to the effect of hole.
Experiments were also conducted for the same model of F. E. M. calculation. It was found that brittle fracture initiation is almost independent of hole location, when the diameter of hole is small in comparison with the crack length. And the estimation of fracture initiation stress for this experiments can be made by COD-criterion. It also showed that stress and elongation at completely fracture of specimen with hole are dependent of hole location and are never lower than these of specimen without hole.
For more general circular holes, the effects of circular hole location and size on brittle fracture behaviors were preparedly considered.

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The authors carried out the experimental and analytical investigations for the purpose of finding out the method of estimating the fatigue crack propagation life and the increment of crack length due to fatigue crack propagation for the surface cracked 9 % Ni-steel plate.
In the first place, fatigue crack propagation tests were carried out on center through notched specimens of plate, forged, welded material, and for 4 kinds of surface notched specimens, similar tests were also conducted.
From these test results, they cleared the following matters such as, law of fatigue crack propagation, surface crack length when surface crack was through the plate thickness, crack length when the crack length at front surface was nearly identical to one at back surface, the method to estimate the fatigue crack propagation of surface cracked plate, etc.
Next, using the above method, they investigated the fatigue crack propagation life and the increments of crack length due to fatigue crack propagation for three high stressed regions in spherical tank of LNG carriers.

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In order to obtain useful and reliable data of fatigue strength of 5083 type aluminum alloy and its welded joint for designing of LNG tanks, the fatigue strength was studied experimentally and analyzed statistically including available data in literatures surveyed.
Axial zero-to-tension fatigue tests were carried out of 25 mm thick base plate specimens and the transverse butt welded joint specimens whose reinforcements were ground partly, flushed out, and as welded. Rotating bending tests were also carried out to evaluate the fatigue strength of a heavy section aluminum plate, where the specimens were cut out of thickness direction of a 200 mm thick plate, and longitudinal of a 40 mm plate and crosswise to welding direction of the butt welded plate.
Present test results show that the fatigue strength of the butt welded joint decreases remarkably due to the reinforcement of the weld, but increases up to about 1.3 times by grinding out partly the reinforcement toes, and reaches to the level of the base metal by flushing out the reinforcement. It is also noticed that the relative fatigue strength S_a/σ_u of the 200 mm thick plate along the short transverse direction decreases to about 72% of the strength of 40 mm thick plate at N_f = 2 ×10⁶ mainly due to its porous structure.
Statistical analysis made on the fatigue strength under axial load including the present data derived fatigue design curves presented as an exponential relation S_a/σ_u=C (N_f) ^-k, where the C and k values for the 99% survival were defined with 50% or 95% confidence.
Finally fatigue design curves of the 99% survival with 95% confidence were proposed, of which reduction rates of the strength resulted in 2/3, 4/5, and 1/2 for the base metal, the butt joint without reinforcement and with reinforcement respectively. A Pohl diagram (S_max/ σ_uvs. R) of which S_max/σ_u is determined by a straight line from S_max/σ_u at R=0 to that for R=1 in a modified Goodman diagram (S_max/σ_uvs. S_min/σ_u) is presented as a design curve which shows the effect of the stress ratio.

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The ship model tests were carried out in oblique regular waves to obtain the wave loads : the torsional moment, the vertical and horizontal bending moments.
The model consisted of four segments longitudinally jointed by three multi-component strain-gauge balances. The wave loads were measured at the three sections : S. S. 3, midship and S. S. 71/2.
The experimental values were compared with the calculated ones by the strip method, and fairly good agreement was obtained for vertical bending moment; however, discrepancies were found for horizontal bending moment and torsional moment.
In order to predict the wave loads more accurately, it is considered that the calculation method of wave exciting forces and moments should be improved.

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There are few researches on analysis of propagation of elastic waves in solid by the finite element method and in relation to nonlinear response. J. H. Argyris dealt the behavior of a circular solid of elastic perfectly plastic material under an axial impact. Observing actual behavior of ship structures, there are many cases where the effect of strain rate on mechanical properties of material should not be neglected and for dynamic collapse of structures elastic-plastic large deflection analysis is required under impact load.
To these problems, a formulation for analysis by the finite element method is made and results of analysis show clearly dynamic effects on the nonlinear behavior of structures.

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There are many deep girders in a ship structure as the main strength members. Under increasing loads, local failures, such as buckling, yielding etc., occur in these members. These phenomena decrease the stiffness of the members and these changes of relative stiffness in the structure induce redistribution of internal forces and the structure finally shows its ultimate strength.
A ship structure is composed of so many such members and its behavior to the ultimate strength is highly nonlinear. There are powerful tools to analyze nonlinear behavior, such as the finite element method, finite strip method, etc. However, the analysis by these methods requires enormous computing time for calculation and in the present circumstances it is impossible to apply these methods directly.
To overcome these difficulties, an analytical unit of large size and idealization of the highly nonlinear behaviors are developed in this paper. A “Girder Element” is proposed, of which stiffness matrices are derived for indivisual kinematic condition, such as after buckling, at the ultimate strength or plastic strength under compression, bending, and/or shear. Based on these idealized behaviors, a method of ultimate strength analysis is proposed. The result of analysis by this method represents well the detail behavior of example structures, of which simple one well coincides experimental behavior conducted in this study. The computing time is remarkably very short.
These nature of the new method promises the validity and possibility of the method to the ultimate strength analysis of structure of large size.

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Increase of tanker size may be accompanied with the problem that hull deformation will affect alignment of shafting and turbined gear in various conditions.
We investigated deformation of hull structure by FEM calculation and measurement of 270, 000 & 410, 000 DWT turbine tankers. The results of FEM calculation agree rather well with the measurement of actual ship (270, 000 DWT tanker).
In this paper, we would report some results as reference for structural design. The summary is as follows.
(1) Shear rigidity of hull girder affects the response of double bottom deflection. Therefore, 3-dimensional calculation is useful for checking the bouble bottom design.
(2) In way of narrower breadth of double bottom, vertical deflection is much affected by bending moment carried from pressure on side shell than by vertical pressure from bottom shell.
(3) Variation of loading weight in engine room, and L. O. temperature seem to give some effects on hull deformation and alignment of shafting.
(4) Reverse deflection in (2) due to side pressure works good effection on shafting as a cancellation factor of upward deflection of double bottom due to bottom pressure.

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The bow impact pressure and its structural response have so far been studied mainly by drop test of three dimensional bow model. In the previous report, authors discussed the characteristics of maximum impact (peak) pressure obtained from drop tests under various impact conditions which were determined by three principal parameters dictating the bow impact pressure. In this second report, the authors deal with the structural response of a rectangular plate panel in the bow model for impact pressure. Drop tests were conducted with five models and, as the magnitude of the impact pressure equivalent to the panel structural response, the “equivalent static pressure P_eq” was used, since the measured “maximum impact pressure P_max” did not contribute to structural response of the panel as uniformly distributed pressure. The equivalent static pressure P_eq, which is converted from maximum transient strain of the panel into uniformly distributed static pressure, includes the dynamic response to impact pressure. In the severest condition of impact (relative angle α of 0 deg.), the magnitude of P_eq for the typical, flexible panel of the ship bow is of the order of one third of P_max, and about 20% higher than that for comparatively rigid panel (three times as thick as the flexible panel). The relationship between relative angle α and P_eq for a panel located at the center of the model was established.
Furthermore, applied to semi-cylindrical body with relative angle of 0 deg. combining the characteristics of P_max obtained by experiment and the Wagner's hydrodynamic pressure, the quasi-static response of a rectangular plate panel to calculated impact pressure was analyzed, for comparison with experimental results. It was found that such numerical analysis would be useful in estimating the approximate magnitude of equivalent static pressure P_eq. The results of such numerical analysis showed that P_eq was affected considerably by an area of a panel and its position.

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Long-term predictions of vertical wave shearing force were made for a gigantic oil tanker of 310 meters length and the similar ships of different lengths, in order to examine the design values of vertical wave shearing force given by the different classification societies.
In the first place, the response functions of vertical wave shearing force were calculated by the aid of the modified strip theory which was applied for cases in oblique waves. Then, the standard deviations of vertical wave shearing force were evaluated for different short-term sea conditions, based upon the linear superposition theory, by using the calculated response functions and the wave spectra which were formulated for the different sea conditions. Finally, the long-term predictions of vertical wave shearing force were performed by using the obtained standard deviations of vertical wave shearing force for individual short-term sea conditions and the wave statistics of the North Atlantic Ocean.
According to the results of systematic prediction works which were made for a range of ship speed and of heading against wave direction, the longitudinal distributions of shearing force amplitude predicted with the exceeding probability of 10^-6 were obtained and compared with those given by the different classification societies.

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In the usual analysis of floating structures, rigid body motion is analized first and afterthat, global structural analysis as a elastic body is conducted. For large floating structures, however, elastic deformation of structural members may affect the motion of them. In this paper, a method analyzing the motion of floating framed ocean structures subjected to periodic waves is presented, where flexibility of members is included and internal stresses of them are calculated simultaneously. In this method, functions of subdivided elements of members are assumed to be divided into two. One is a rigid body with mass, shape and sizes and the other is a elastic beam with elastic rigidity. The equations of motion are introduced by using matrix method.
The calculations based on the mentioned analytical model were compared with experiments by simple floating models and the coincidence was fairly good.

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The buckling strength, resistance against vibrations, and fatigue strength of the transverse member are very important considerations in the designing of very large oil tankers. The authors specifically studied the deck transverse member for buckling strength.
Six deck transverse models, three corresponding to the deck transverse members in a 120, 000, tons dw oil tanker and the remaining three to those in a 240, 000 tons dw oil tanker, were fabricated and tested to determine the buckling strengths of these transverse members reinforced with tripping brackets. The tripping brackets were provided with different degrees of imperfection, and one model in each group was provided with no such tripping brackets at all. All models indicated the lateral instability but almost no difference in their buckling strengths and their modes of failure. Also, the authors treated each deck transverse member as a compressed beam supported on an elastic foundation and successfully analyzed the buckling behavior of the transverse member. Simple formulas used by the authors to determine the buckling load and failure mode were found highly useful.

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Much has been learned about the stress concentration in the vicinity of slots in the ship transverse web frame and the fatigue strength of the slots, contributing greatly to the improvement of ship structural design.
The authors produced 1/2 scaled three dimentional models of the transverse web frame members, each containing 9 or 10 slots, and tested them for fatigue strength hydrostatically or by hydraulic-jack mechanical loading. By use of such large models, the authors studied, specifically, (1) the validity of the previous findings made using relatively small models regarding the stress concentration near the slots and strength of the slotted transverse frame against crack initiation, (2) how the crack propagation would be affected by the three-dimensional structural profile and by the presence of adjoining slots, and (3) the fatigue strengths of problem regions of slotted bottom transeverse frames which are to be provided between the outer and inner bottom shells in the projected double-bottomed tanker hull structure, the last named being an important consideration in the prevention of possible sea pollution by leaking cargo oil.
Hiroshima Technical Institute and Nagasaki Technical Institute of Mitsubishi Heavy Industries, Ltd., jointly experimented the models, with the former taking charge of the ordinary, slotted transverse “ring” web frame in the tanker wing tank and the later the slotted bottom transverse frames in the double-bottomed tanker. Also, the authors analyzed the crack propagation characteristics using the fracture mechanics technique, the results of which will be reported later on.

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In this paper, experimental test results of a full scale measurement on a cantainer ship are reported of the structural behavior of the transverse strength members of the ship. The test is carried out by filling fresh water in a container hold, and the stress measurements are made on tank top plating, floors, girders, side transverses, and upper deck girders, as well as box-typed beam, pillars and horizontal girders of container supporting structures. Local stress measurements are also made on small brackets attached at the corner of tank top plating and inner hull where stress concentration is remarkable due to the straight corner connection between bottom and side constructions.
Also described are the theoretical analyses on the container hold structure under tested condition by means of computer programmes based on the finite element method both for three-dimensional frame and plate structures.
It is found from this investigation that the stress distributions in the double bottom structures can be well estimated by using the structural analysis programmes within a satisfactory accuracy for practical design purpose. Furthermore, it is confirmed that the container supporting structures in the container hold are effectively arranged from view point of the transverse rigidity of the ship.

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In regard to the hull strength of cargo vessels, ore carriers and tankers, some measurements have been done during voyages, and the results of these theoretical. analysis have been published so far.
On the other hand, while many large, fast container ships have been built recently, there still remain some problems to the hull strength in rough sea.
In order to cralify these problems, we have measured the stresses of the hull of a container ship during one round voyage across the Pacific Ocean in winter.
From these experiments, we obtained the following results.
(1) From the estimation of the long term distribution of total longitudinal stress on upper deck, the maximum value is expected to be 10 kg/mm² in single amplitude for 20 years and consequently 16 kg/mm² with still water bending stress.
(2) Horizontal stress on upper deck is comparatively small, however torsional stress reaches to 4080% of total longitudinal stress according to the sea states.
(3) Longitudinal bending stresses separated from the measured stresses coincide with the theoretically calculated values of wave bending moment in head sea, but the formers are a little bigger than the latter in following sea.
(4) The maximum wave bending moment in 20 years is expected to be 7 kg/mm² in single amplitude. This value is 70% of total longitudinal stress.
(5) Maximum warping stress during this voyage was 2.2 kg/mm² and the maximum value in 20 years is expected to be 4.5 kg/mm² in single amplitude respectively.

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In numerical simulation pertaining to torsional strength of large container ships, various problems encountered in the initial stages of designing ships with large hatch openings are discussed.
An actual ship of 38, 000 gross tonnage (container capacity : 1, 800 of 20' container) is adopted as the type ship, and the loading condition is based on the method proposed by Wilde.
In the analysis, ships are treated as beam shells with variable cross-section, and a coupling effect between torsion and horizontal bending is also taken into account.
As a result of this simulation, the following conclusions were obtained.
(1) It was found that the most severe condition possibly occurs not in the middle part of ship but in the part about L/4 (L : ship length) apart from the bow.
So the effect of variable cross-section should not be neglected in the analysis.
(2) The effect of the double hull structure of ship side is considerably large to increase the torsional strength of container ships.
(3) The application of the high tensile steel to the upper deck part gives little effect on the increase of torsional deformation in spite of the decrease of the plate thickness of that part.
(4) In arranging the cross decks between hatch openings, provision of a large member in the middle part between the midship and the bow is very effective for the torsional strength.
(5) The tier type structure is preferable to the knuckle type in various respect. In particular this type will assure a greater strength in the section toward the bow.

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One of the principal causes of the fractures around the slot of transverse web is considered to be the effect of lateral vibration of transverse member.
In this report, at first, exciting tests were carried out with the bottom trans. model of 1/4 scale actual ship in order to investigate the natural frequencies and modes in detail.
Secondly, during the sea trial of 224, 841 DWT and 284, 495 DWT oil tanker, comprehensive vibration measurements of ship hull and bottom trans. were carried out and those data were used to find response characteristics and excitation sources.
Finally, the theoretical analysis of natural frequency and hydrodynamic pressure for the lateral vibration of trans. member were carried out and the former results were compared with the measured values.
The results obtained are as follows :
(1) Calculated natural frequencies and modes except for modes in water showed considerably good agreement with those of the measurement. Natural frequency of 2 nd order in water is less than or nearly equal to one of the O-node axial vibration of shaft system.
(2) Hydrodynamic pressure distribution depends on natural mode of member itself, correlation between adjacent ones and the shape of bracket and face plate. Therefore, further investigation is necessary to estimate virtual added mass.
(3) Engine and propeller induced axial forces of shaft system are mainly transferred to the bottom trans. and amplified through axial vibration of shaft system and ship hull vibration.

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End cracking in one side automatic welding is said to be a kind of solidification cracking. Though many analyses and experiments have been done to know expansion of root gap near the end of the plate, there is no attempt to evaluate the deformation behavier of weld metal during solidification in one side welding. In order to develop the higher welding technology, the authors are aiming to establish a criterion for occurrence of end cracking by using deformation curve (1) during solidification and ductility curve (2) in high temperature range as shown in Fig.1. In this report, authors have firstly analyzed deformation behavier during solidification in one side welding of fully large plates by modification of analytical solution using finite element method. Secondly, effects of plate width, weld length, and welding conditions on deformation behavier during solidification have been investigated. Thirdly, validity of analysis method using in this report are examined by comparing the calculated transient deformation behavier to the experimental one.
Finally, authors have proposed the methods to estimate length and position of end cracking in one side welding.

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One sided automatic welding technique has broadly been prevailed in our shipyards. This technique not only enables omission of turning from side to side but also improves production processes of ship structures. But it is observed that cracking occurs in the center of weld metal near the end of weld joints. So far, complete preventing methods which do not violate production processes seem not to be found.
In this paper a preventing method is proposed. In the process of one sided automatic welding, restraint force (1030 ton) should be loaded on the two devided tab plate and furthermore the tack weld near the end of weld joints should be removed (extend over 2 m). Experimentally it is confirmed that the end cracking has not appeared and it seems to be very useful preventing method.
In order to analyse this preventing method, authors have proposed calculation technique which differs from the ordinary welding thermal stress analysis such that the conditions of calculation are simulated to be more realistic welding procedures. And special attention is paid to that yield phenomenon of tack weld and strength of electro magnets which sustain welded plates are considered.

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In the assembly stage of ship construction, gap is often produced between the prepared edges of joints owing to welding deformation, etc. Especially, in the case of Tee-type fillet welded joints, to establish effective joining methods is an important problem. The effective method should be discussed from the view points of efficiency in procedure and strength of the joint.
Today, the following three methods are used for welding of joints with gap : by increasing the leg length, by welding with bevel preparation, by inserting a liner into the gap. Sufficient strength of joint should be guaranteed regardless of the amount of the gap and the kind of treatment.
In this report, the effect of the treatment for the gap on static and fatigue strength for Tee-type fillet welded joints were investigated. As the amount of penetration influences the strength of the joint, the relation between the amounts of penetration and the gap was studied by experiments. The counterplan of the treatment considering the strength and the welding procedure was then discussed and the following conclusion was obtained :
(1) In the case, where the gap is smaller than 3 mm, the joint with the rule leg length shows sufficient strength.
(2) If the gap g is greater than 3 mm, additional leg length, A is required as follows :
A= g -3 (mm)
(3) If the gap is larger than 5 mm, a piece of liner should be put into the gap. The liner breadth, B, must satisfy the following condition :
t+2R+10≤B≤ 3h (mm)
where, h : thickness of liner
t : thickness of base plate
R : rule leg length
In this case, the rule leg length furnishes sufficient strength of the joints.

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In recent years, SPITS (Sumitomo Production Information Total System) which consists of aggregation and delivering system and job order system has been developed in our company.
These systems have intimate relationship namely the former supplies the latter with the material information to estimate working man hours and the latter indicates the former with the time for aggregation and delivering.
The job order system has been carried out in hull shop and machinery fitting shop from May, 1973 as test case and now prepared for all construction dept.
This time the aggregation and delivering system in which all fitting equipments of hull and machinery are included has been systematized as material control total system extended design, purchasing and construction dept., and carried out as On-Line Real Time System.
This paper explains about the aggregation and delivering system.

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A recent numerically controlled flame cutter has brought on improvement of efficiency of both marking and cutting, and has resulted higher accuracy to us. However, an automated or numerically controlled equipment is very expensive in the field of not only hardware but also software, and then increasing its running time, from the point of view of investment, has to be very required.
Nevertheless, it still requires many hand operations, therefore it is considered that its running time is a few and does not function as a labor saving or man-less apparatus.
Some points requiring hand operation, for example, are as follows.
(i) Steel supply and its accurate setting to NC cutter.
(ii) Watch and adjustment of flame.
(iii) Cutting of bridges for preventing from heat distortion.
(iv) Setting the cutting speed, amount of kerf-width compensation and pre-heating time.
(v) Marking characters.
(vi) Input paper tapes for every plate and each cutter because of its individual NC.
(vii) Others.
The Group Control System from Steel out up to Cutting can eliminate those factors against labor-saving or man-less operation with various new automated apparatuses and planning out new control methods.
In this system one mini-computer with magnetic drums, a magnetic tape and a CRT controls directly 4 NC cutters (2 plasma and 2 gas cutters), steel supply facilities that are 36 line conveyors, a traverser, a graphic pannel for monitoring traverser and conveyors, etc. and other apparatuses.
Also this system makes various administrative control, e. g. scheduling for cutting, summing running results of NC cutter, etc.
This system, in other word, is considered as the first attempt in the world of the whole process control system from steel out up to cutting.

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This paper describes the planning principles for the sub-assembly & fabrication stages in the serial procedure of SASP (Sasebo Scheduling Programme) on hull construction process.
It has been generally believed that the quantities of input data are a great obstruction to the effective computer applications in this field, however, the author has attained a practical solution for this problem by employing the concept of unit-work's, instead of taking each piece of materials as the direct object of controlling.

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In order to improve the hatch covers of a container ship, the calculations on deck wetness are applied to predict the water leakage into a cargo hold.
The results obtained by the calculations are as follows :
1) The quantity of water flow into a cargo hold under the heavy weather is small, even where the gaskets of a hatch cover are eliminated.
2) The short term probability of deck wetness is small.The flow into the foward cargo hold is less than 10 m³/h, under the sea conditions of significant wave height of 710 m.
3) The long term probability of deck wetness is also not so high.
According to these results, the improvement of hatch covers, such as elimination of gaskets, will be successfully adopted.

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There are many comparatively small oil tankers carrying clean products of petroleum or petrochemicals. Recently, the sizes of these product carriers are being apt to become larger type due to the need in the world wide petroleum situation.
Internal tank surfaces of this carriers are exposed to severe corrosive environment such as high solubility Hydrocarbons, rolling and moving ballast water, high temperature condition of Butterworth cleaning and corrosive moisture contaning active sulfur compound.
Pitting or local corrosion may occur attacking on unprotected internal tank structure and corrosion products often causing cargo contamination and pump trouble.
Method for preventing these corrosion is very difficult and expensive, cathodic protection, use of organic inhibitor in cargo or water, clud of stainless steel or lining of Fiber Reinforced plastics etc. are not so perfect every time and difficult to apply. Protective coating of Inorganic Zinc Silicate is comparatively economical and considered to be endurable against clean cargoes and seawater ballast.
We hereby report the results investigated on the durability of Inorganic Zinc coating to clean products and contamination of cargoes.

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