US2741208A - Tank ship bulkhead and girder construction - Google Patents

Description

April 10, 1956 v. ALBIACH 2,741,208

TANK SHIP BULKHEAD AND GIRDER CONSTRUCTION Filed Aug. 24, 1951 2 Sheets-Sheet 1 INVENTOR. VINCENT ALBIACH April 0, 1956 v. ALBIACH TANK SHIP BULKHEAD AND GIRDER CONSTRUCTION 2 Sheets-Sheet 2 Filed Aug. 24,

INVENTOR. VINCENT HLsmcH HIS HTTOR EYS Unite rates Patent TANK m BULKHEAD AND GERBER CGNSTRUCTION Vincent Albiach, Paris, France Application August 24, 1951, Serial No. 243,463

4 Claims. (Cl. 114-79) The instant invention relates to ship construction, and particularly to an improved tanker.

Among all the types of merchant ships, those vessels intended for the transportation of petroleum or other liquids in bulk are particularly affected by conditions at sea. The reasons for placing the oil tanker in this particular category are threefold.

In the first place, tankers are generally designed to navigate at the minimum freeboard permitted by the International Convention Tables on Load Lines. To this end the superstructure is reduced to a minimum, and therefore its contribution to the strength of the hull structure is correspondingly reduced. Secondly, the propelling installation is generally arranged aft, and seldom amidship' as is the case for the majority of other types of ships. This results in an increase of the loading of a tanker in the order of by comparison with a cargo ship of the same hullform but with the engines amidship. Finally, the nature of the cargo creates special problems. The petroleum cargo, which may not be evenly distributed especially when the ship is in a ballast condition, imposes local loads on certain parts of the hull structure such as the longitudinal and transverse bulkhead platings, the motion of the ship at sea causing inertial forces to be exerted upon the hull.

In the past, tankers have been designed with the object of integrating the longitudinal bulkhead platings into the main structure of the ship so as to provide added stiifening against the main hull stresses imposed by hogging and sagging while the ship is under way. The liquid cargo exerts hydrostatic stresses (static and dynamic) upon the ships hull so that these stresses had to be algebraically added to the hogging and sagging stresses in calculating the scantlings for the various members of the hull structure. The superposition of these stresses on the longitudinal bulkhead platings frequently resulted in fractures, with the concomitant dangerous possibility of their spreading to adjoining structural elements.

The present invention avoids this superposition of stresses on the longitudinal bulkheads, these bulkhead platings being so constructed that they are in effect filling panels and hence need only be designed to withstand the hydrostatic stresses imposed by the liquid cargo.

In accordance with the present invention, the longitudinal bulkhead platings are composed of sections positioned between reinforced keelsons at the ships bottom and reinforced continuous girders at the top side, the sections of the, bulkhead being interposed between cruciform struts arranged as pillaring members in the region of the trans verse bulkhead platings. In the preferred form of the invention, the longitudinal bulkhead platings are formed from flanged plates in U-form so as to have vertical corrugations. The resulting fluted form of the bulkhead plating has a taper varying linearly from the bottom to the top in accordance with the moment of inertia of horizontal sections thereof, adjusted to the stresses of the liquid cargo.

The new construction reduces the possibility of frac- 2,741,208 Patented Apr. 10, 1956 istic of prior art designs. Also, it facilitates prefabrica tion and repair, thus lowering both the initial shipbuilding costs and the costs of maintenance while the tanker is in service.

A better understanding of the invention may be had from the following description taken in conjunction with the accompanying drawings, in which:

Fig. l is a reinforced transverse half section in accordance with the invention, taken along the line 1--1 of a longitudinal bulkhead plating shown in Fig. 3, the port and starboard half sections being identical.

Fig. 2 is an ordinary transverse half section in accordance with the invention, taken along the line 22 of a longitudinal bulkhead plating shown in Fig. 3, the port and starboard half sections being identical.

Fig. 3 is a horizontal section in accordance with the instant invention taken on a reduced scale along the line 33 of a longitudinal bulkhead plating shown in Fig. 1.

Fig. 4 is a horizontal section, also on a reduced scale, of another embodiment of a longitudinal bulkhead plating.

Fig. 5 is a perspective view of a longitudinal bulkhead plating in accordance with the instant invention.

Fig. 6 is a diagrammatic horizontal sectional view, on a reduced scale, as seen from about the level of the line 33 in Fig. 1.

Referring to the drawings, the tanker comprises two longitudinal bulkhead platings 25 (Figs. 1 and 2), running fore and aft and dividing the cargo portion of the ship into three sections. A number of transverse bulkhead platings 26 (Fig. 3), placed perpendicular to the longitudinal bulkhead platings, subdivide these longitudinal sections into tanks, the outboard tanks being called wing tanks (one on the port and one on the starboard side), and the inner tank being called a center tank. Between successive transverse bulkhead platings, the ships hull comprises reinforced and ordinary sections, as shown in Figs. 1 and 2, respectively. 1

Referring now to Fig. 1, there is shown a reinforced section of a tanker in accordance with the invention. The hull is bounded by a bottom 1, deck 2 and shell 3. In order to help stiflen the ships girder against fore and aft deflection, longitudinals 4, 5 are provided at the bottom and at the deck, respectively. Under the deck 2, a continuous deck transverse 6 is arranged, and similarly at the bottom 1 a continuous bottom transverse 7 is positioned in the port to starboard direction. A reinforced frame 8 is mounted between the deck and bottom transverses 6, 7. Added strength is provided for the hull structure by diagonal ties 9, 10. Diagonal tie 9 is secured between lugs 11 and 12, which are integrated with the reinforced frame 8 and the deck transverse 6, respectively. Similarly, diagonal tie 10 is mounted between lugs 13 and 14 integrated with the reinforced frame 8 and the bottom transverse 7, respectively. At the outboard ends of the diagonal ties 9 and 10, stiffeners 15 are secured to the frame 8 and shell 3, while at the inboard ends, stifi'eners 16 and 17 are fastened, respectively, to deck transverse 6 and bottom transverse 7.

Under the deck 2 and on the ships center line is a continuous longitudinal center line girder, shown generally at 18. The vertical center keelson 19, running fore and aft, is positioned on the center line at the bottom of the hull, and is reinforced by a bracket 21 and a flat plate 20.

Near each side of the ship, a side keelson 22 is provided as added longitudinal stiffening for the bottom 1. Each side keelson 22 is reinforced by a fiat plate 23. Under the deck and in vertical alignment with each side keelson 22, a continuous girder 24 is similarly pro I successive transverse bulkhead platings.

I deck, girders 24 being reinforced by plates 24a.

As previously stated, the two longitudinal bulk-head platings 25partition the-ships breadth into three sections or row's,,each bulkheadplating. 25 being erected between the reinforced sidekeelson-22 atthe bottom and the continuousreinforced girder 24-atthe top. In accordance with .the invention, the 1 longitudinal bulkhead plating's 25 are formed by means of flanged plates in U -form so as to have vertical corrugations, as. shown in Figs 3, 4 and 5, The flangedaplatesmay be-placed butt to butt as in Fig. 3 or overlapped asinFig- 7 The corrugated bulkheadplatingsli aretapered, varying linearly from the bottom'at plate 23- to the top under plate 24a. This isbest-illustratedin the perspective view shown in Fig. iwhere it will be t-observed that dimension c at the foot is greaterthan the-length-btshown at the top.

The longitudinal; bulkhead plating 25 is not. continuous bUtIQ'mlHaIES just short otja transverse bulkhead plat-' ing26 (Figs. 3eand 4) so as to form sections 25; between terminations of the corrugated bulkhead platings 25 on each. side of the transverse bulkhead plating 26, cruciform struts 27 extend vertically sojasrtovform a strong pillaring member between the deck and bottom portions of the ship. As shown in the drawings, particularly Figs. 3, 4 and6,

these strutsl'l form theintersections-of the longitudinal bulkhead plating 25f. and'thietransverse bulkhead plating 26, the struts'having arms 21a: secured tothese bulkhead platings in substantially liquid-tight relation; to complete the liquid cargo tanks. 7 V

Reterring now, to theftransverse section illustratedwin Fig. 2, this section comprisesside stringers 29- extending 'foreandaftalongthe sideeofythehullg the stringers 29 having brackets 31:. Between the'deckandtop stringer,

a-stiffening'plate 30 is mounted; The bottom longitudinals 4 are secured by'transverse stifiener 32. The vertical center keelson Bis-:strengthenedin this section by, a

r vertical stiffener; The girder24 and side keelson 22 are reinforced by brackets 3-5; and 33, respectively.

Whenasbip is underway atsea, the hull girder is. subjected to bendingstresses imposed by the;conditions of hogging and sagging. Theterms-hogging and sagg-"are used to refer to-, the twoopposed conditions of longitudinal deflection ot the, ships girder. In thesag ging condition, the dfiflfiCtiOH'iiSdGWHWflId,iILthfi region;

: ot midship, while in-theih'ogging condition the d flection is upwardin, this region; Various combinations of hog and. sag can'and do; ofzcourse, occur nder dynamic condi- .tions at sea.

In prior artgdesigns, the longitudinal bulkheadplat ngs areintegrated into'themainstructure of the ship. so that 7 they cooperate in resis i g. thebending moments imposed by hog andsag; In a-tanker, theelongitudinal bulkhead platings are also; subjected to the static-and dynamic hydrostatic stressesofitheliquidcargo, the motion of the" ship, under way causing, inertial forces to beexerted; Thus; there resultsa superposition of, the main hull, stresses-(bending 1110111611155 due to: hogging and sagging), and the local. stresses (hydrostaticstressesfla combina tion which is the causeofi'a large number of fractures in the ships structure, The;rnostseriousconsequence; of these fractures is. the danger'offthein spreadingto par Qfthe adjoining structures especially where the ship is of welded construction as is the case in most ,moderntankers.

I have found it adyantageousto avoid this superposition of the main hull; and localstresses. According to my'in girder in resistingthe main hull stresses, Theglongitudi- Between the 4 nal bulkhead platings 25 thus act as filling panels between the above-described members and hence are only required to sustain the local stresses. Accordingly these bulkhead platings may be designed with scantlings having a reduced margin sufiicient only to support the hydrostatic loads due to the liquid cargo, thus efiectingvaluable save ings in the weight of the ship;

Another advantage of the invention over the prior structures stems from the tapered fluted form of the bulkhead plating 25 (Fig. 5). This configuration enables one to adjust the moment of inertia of'difierenthorizontal sec tions of the bulkhead plating to the stresses transmitted by the liquid cargo, so that further savings in weight can be obtained. 7 V

The new construction also facilitates prefabrication and 'makes cleaning andmaintenance in service mucheasier.

The flanged plates for the corrugated longitudinal bulkhead platings 25; maybe lowered into the hold, so: that construction of the main ship. structure can proceed in: dependently. Similarly, when repairs are required in the longitudinal bulkhead plating, sections of it may beremoved. with a, minimum oi'disturbance to the remaining ship-is structure. I claim:

1. In a tanker'shzp having a shelhbottom and deck,

the combination; of. center. keelson extending longitudibelow: and secured insubstantially liquid-tight relation to the side keelsonsand deck girders, said longitudinal bulkhead plating terminatingshort'of the transverse bulkhead plating, and cmciform struts forming the intersectionsof the bulkhead. plating and extending vertically from the side-keelsons to the deck girders and secured. to'said. side keelsons and deck: girders and having arms securedto said longitudinaliandtransverse bulkhead. plating, all'in substantially liquid-tight relation, the bulkhead plating forming with the struts a series of liquid cargo tanks, the strutsconstituting the main pillaring for the deck girders, thereby enablingthe use of bulkhead platingofr reduced scantlingc I 2. Thecombination according to claim 1, in which the longitudinal bulkhead platings' are corrugated vertically.

3.' The combination according. to claim 1, in which the longitudinal bulkhead platin gs are corrugated vertically, thecorrugations having: greater depth at the-bottom of the bulkheadplatings than at the topthereof.

4.. The combination according to claim 1, comprising also deck and bot'tonr transverses, a reinforced frame mounted between said transverses adjacent the shell, and diagonal ties extending fromsaid' frame to the'deck andbottomtransvers'es', respectively, said ties terminating adjacent' thevertical' extremities of the longitudinal'bulk-e 7 head platings.

I References iCited in'the'fileof this patent UNITEDSTATES PATENTS

Images