Deformation Of Hull Research Articles

On a Study of the Longitudinal Strength of Ships with Torsional and Horizontal Deformations

In addition to the longitudinal bending and shear deformation of ships in the vertical plane, the effect of longitudinal bending and shear deformation of ships in the horizontal plane coupled with the torsional deformation is particularly considered in the method of theoretical analysis.This theoretical analysis treats the ship as a beam shell with various cross-section in which the actual structure of ship is rather faithfully considered.Concerning the structural idealization, ships are divided into substructures with uniform cross-section and then each substructure is also divided into small strip elements.Further, the experimental works are carried out, using a model of container ship with large hatch openings. And it has been confirmed that the calculated results obtained through this method are in good agreement with the experimental results.The results of this investigations led to the following conclusions.In dealing the longitudinal strength of container ships considering the horizontal bending and torsion, the analytical method described here seems to be effective for the practical use in designing of ships.In the structural analysis of container ships, the cross decks between hatch openings should be treated as a reinforced member arresting the torsional deformation of main hull instead of treating them as a part of it. And it is appropriate to adopt 1.0 as the fixedness of the end connection of cross decks for the practical use in the calculating the torsional strength of the main hull.

The Deformation of Ship's Hull under Construction (No. 6, Final)

The Deformation of Ship's Hull under Construction (No. 6, Final)

The Deformation of Ship's Hull under Construction (No. 4)

In this report, three problems of hull deflection during construction will be dealt with. First the deflection of that part of the vessel's bottom which overhangs port & starboard of the concrete building berth will be discussed. Secondly the deformation of superstructure decks during the completion of work after launching will be discussed.The third and major topic of discussion will be the problem of the deformation of the vessel's bottom and inner bottom in way of machinery room in connection with the problem of propeller shaft centerline alignment and/or boss boring. In regard to this problem, the following findings will be shown : (1) The rate of rising of the stern is greatest during the earlier period of construction and decreases gradually as the work progresses. The amount of eccentricity of stern tube bossing when ploted against progress of work gives the “Sine” curve.(2) The athwartship deflection of the vessel's stern either to port or starboard is strongly influenced by seasonal, climatic conditions.(3) The fore & aft shrinkage of the stern part of vessel's hull is greatest during early stages of construction (as is the case of the stern rising). The rate of shrinkage of the main deck does not necessarily coincide that of the vessel's bottom.Finally, the shrinking force resulting from welding and heating will be discussed together with the result of some experimental model tests to confirm the fact that the fore & aft shrinkage of the vessel is caused to far greater degree by the welding on the ship's bottom and its vicinity than the welding on the main deck and above.

The Deformation of Ship's Hull under Construction (No. 5)

In this report, three subjects will be dealt with. First, an example of variation of transverse shrinkage of ship's bottom plating during progress of hull welding will be illustrated, which variation of shrinkage somewhat resembles that found in fore & aft direction.Secondly, an attempt will be made to explain results observed in actual cases of ship construcition which indicated that the ship's bottom deformation such as the rising of the stern was caused chiefly by welding the bottom in the vicinity of the deformation and was little affected by welding of the main deck & structures above the main deck.The third and major discussion will concern the influence of ship's deformation on the propulsion shafting. When main propulsion shaft bearings are out of line, many troubles should be anticipated, such as shaft failure, extraordinary wear-down of bush or bearings, vibration or whirling, and loss of power etc.Regarding the problem of untrue shaft bearing, the variation of bearing reactions and the bending moments in shafting corresponding to various alignment conditions were calculated on one ship. The comparison of the resulting calculations led to the conclusion that the most important thing is to equalize the bearing reaction and bending moment of shafting everywhere as much as possible. It is only of secondary importance to maintain all bearings on straight line.Another conclusion resulting from the calculation is that a faired deflection of bearing position such as deformation due to ship's hogging or sagging, even if the amount of deviation of bearing position from a reference line is remarkably large, will do little harm the shafting. Rugged deformation such as in case of stern bush wear-down or local deformation due to welding will be harmful to the shafting.

The Deformation of Ship's Hull under Construction (No. 3)

The major subject of the present report is concerned with the deformation of ship's bottom caused by welding. And it will be shown that the final shape of bottom on berth-lifting at ship's ends and shrinking fore & aft-is determined by the welding to the bottom and its vicinity, and not the main deck and above.It will also be shown that the intensity of tensile reaction stress in main deck plate of the large tanker does not increase with the progress of welding work through construction period.It follows from the above that the apparent sagging moment by which the weld-constructed ship tends to sag after her launching is not due to the welding internal stress which may be considered to be restricted on berth and released at water born, but the differences between the distribution of ship's own weight and reaction force by keel block and shore.

The Deformation of Ship's Hull under Construction (No.2)

In the previous report, the deformation of sihp's hull on berth caused by simple loading, temperature variation, or welding shrinkage was discussed.In this report, superimposed deformation and lowering of ship's hull as well as building berth through construction and testing period over one month will be discussed, and it will be shown that the unexpectedly large amount of lowering of ship's bottom, amounting to 2030 mm, is not necessarily due to overloading, but nature of wood, in other terms, the accumulation of both unrecoverable deformation with loading cycles and time effect in keel blocks or wooden supports.In addition, some ideas will be developed which will be useful in the prediction and interpretation of ship's condition, sagging or hogging, encountered immediately after ship's launching.

The Deformation of Ship's Hull under Construction (No. 1)

Ship's hull under construction undergoes various deformations, such as bending up and down or athwartships and shrinkage fore and aft. The major elements to cause such a deformation are (1) loading (hull weight and water weight), (2) temperature variation, and (3) shrinkage force due to welding.The deformation of ship's hull is complicated, because the above elements affect the ship simu ltaneously and the intensity of element itself varies with time. Thus, while the length of ship, for instance, varies every moment with atmospheric temperature and sun shine, it tends to be shortened as a whole due to the welding shrinkage force. Furthermore, because of the nature of wood, the ship's bottom lying on wooden blocks lowers with time even if the load be kept constant.The present paper is concerned with the result of deformation measurement on actual ships, theoretical investigation, and practictal applications in ship-building in connection with, for example, the hull supporting method on berth and the method to find the most favourable propeller shaft center line.