US1267680A - Concrete ship. - Google Patents

Description

A4 MACDONALD.

CONCRETE SHIP.

APPLICATION FILED OCT.23, 1917.

Patented May 28, 1918.

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ATTORNEYS,

A. MACDONALD.

CONCRETE SHIP.

APPLICATION FILED OCT. 23, 1917.

1,267,680. Patented May 28, 1918.

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ED STATES PATENT one .ALAN MACDONALD, OESAN Fnenorsoo, cALIron'NIA, AsSIGNon T0 SAN FRANCISCO SHIP BUILDING (30., ,OF FRANCISCO, CALIFORNIA, A CORPORATION OF CALI- FOBNIA.

CONCRETE SHIP.

Specification of Letters Patent.

Patented May as, 1918.

Application filed October 23, 1917.- Serial No. 198,010.

To all whom it may concern:

Be it known that I, Aux MACDONALD, a citizen of the United States, residing at the city and county of San Francisco and State of California, have invented certain new and useful Improvements in Concrete Ships, of which the following is a specification.-

My invention relates to the art of .ship building and especially to concrete-ships. One of the main diificulties in building a concrete ship is to keep the structure within the required weight. The solution rests largely in keeping the walls and bottom thin.

Considering the whole ship as a large box girder, spanning two waves, or on the top of one wave, with bow and stern out of the water, bad bending and shearing stresses are produced in the sides and bottom. Due to the necessity of keeping the walls thin, by a small area of concrete, it is necessary to add steel to take care of this shear.

It is customary in concrete walls of buildings and other structures where thin walls are used, to put steel bars at right angles to one another, vertically and horizontally, to resist the temperature stresses. In the walls of a ship, however, if the bars are placed vertically and horizontally, while they will resist stress to some extent, they are nevertheless insuflicient to resist the shearing stress, which acting at an angle of 45 degrees to the vertical, would require said bars, when so disposed, to be unduly large, and, in turn, such large bars would require a greater thickness of concrete wall to hold them, thus materially increasing the dead weight of the structure.

In order, therefore, to reduce this thickness of wall and to save both steel and concrete, my invention consists primarily in the disposition of the bars in approximate alinement with the direction of the resultant shearing stress, said disposition being oblique to the vertical and horizontal, the preferred inclination thereto being 45 degrees.

Furthermore, considering a ship under a hogging or sagging strain, the entire structure is in fiexure and is so designed. WVhen sagging, the deck is in compression and the bottom in tension, just as any other form of beam under similar circumstances. Under these conditions, and since a ship is hollow inside, the tensional stresses in the bottom are transmitted to theside at the knuckle,

connections, to resist them.

that is, the junction of the bottom and side,

very great, and it has been the custom in concrete ships to increase the size of the sides and the bottom and deck slabs, at these These connections, therefore, become very heavy.

To save this weight and to increase the efliciency of the construction, my invention further contemplates the continuation of the obliquely disposed bars into the deck and bottom slabs to a distance far enough for the adhesion of the cement to develop their strength, the continuation or extension of the bars being oblique to the center line of the ship so as to be exactly in. line of the stress. Lastly, it is best to terminate said bars in the deck and bottom along difi'erent lines.

Referring to the accompanying drawings,

Figure 1 is a perspective view, broken, of a concrete ship showing my improvement.

Fig. 2 is a plan view, broken, of the deck, showing the steel bars exposed.

Fig. 3 is a cross sectional view of the ship.

1 is the side, 2 is the bottom and 3 is the deck of a ship. These are of concrete, as indicated. In the concrete sides of the ship are embedded the steel bars 4 and 5, in such number as may be predetermined. The bars are disposed diagonally, those designated by -l extending in one direction and those marked 5 extending in the opposite direction, the bars thus crossing each other. Their best angle is approximately one of l5 degrees to the vertical, thereby lying in line with the direction of shearing stresses. The bars are continued 01' extended at 4. and 5, respectively, into the bottom, and at l and 5 into the deck, these extensions lying obliquely to the fore and aft median line of the ship, the angle being best 45 degrees.

In order to avoid the termination of these extensions along the same line, it is best to carry alternate ones into the bottom and deck slabs farther in. This is easily done by having all the bars of the same length and extending the lower ends of alternate ones into the bottom to a greater distance than their upper ends are extended into the deck, and vice versa. This is shown clearly in Figs. 1 and 2, and it has the advantage of keeping the full strength of all the bars at the knuckle and gunwaie, where it is needed, and leducing the strength toward the me dian fore and aft line, Where the stresses are not so great.

I claim 1. In a concrete ship, the concrete side Walls thereof having embedded Within them a plurality of obliquely disposed metallic bars crossing each other, and the concrete deck and concrete bottom of said ship having embedded in them continuotions of said bars disposed obiiqueiy to the fore and aft center line ofthe ship.

2.111 a concrete ship, the concrete sides, bottom and deck thereof having embedded Copies of this patent may be obtained for five cents each, by addressing the Within them a plurality of obliquely disposed bars crossing each other in the sides, and continued obliquely inrthe bottom and deck, the extremities of alternatecbars terminating in said bottom and deck along different lines.

In testimony whereof I have signed my name to this specification in the presence of two subscribing Witnesses.

ALAN liiACDONALD.

Witnesses:

WM. F. BOOTH, D. B. RICHARDS.

Commissioner of .Patents "Washington, D. U.

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