US639320A - Girder or beam for bridges. - Google Patents

Description

No. 639,320. Patented Dee. I9, |899.

A. VIERENDEEL.

GIRDER 0R BEAM FOR BRIDGES.

(Applicationled Dec. 31, 1897.)

3 Sheets Sheet (N0 Model.)

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A. VIERENDEEL. GIRDER 0R BEAM FOR BRIDGES. (Application filed Dec. 31, 1897.)

3 Sheets-Sheet 2.

No. 639,320. Patented necflmlass. A. VIERENDEEL.

GIRDER URBEAM FOR BRIDGES.

` (Application mea nec. 31, 1897.)

(N0 Model.)

3 Sheets-Sheet 3.

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. Fili@ e GIRDER OR BEAM FORBRIDGES.

SPECIFICATION forming part of .Letters Patent No. 639,320, dated December 19, 1899. Application led December 81A, 1897. Serial No. 664,823. (No model.)

To all whom, t may concern:

Be it known that I, ARTHUR VIERENDEEL, a Belgian subject, residing at Bruges, Belgium, have invented newand useful Improvements in Girders or Beams Having Arched Openings for Bridges, Framings, and other Metal-Work, (for which I have obtained patents in Belgium, No. 122,018, bearing date June 22, 1896, and No. 128,573, bearing date May 29, 1897; in France, No. 261,686, bearing date November 28, 1896; in Great Britain,

No. 20,214, bearing Idate September l2, 1896,l

and in Austria, No. 47/2,618, bearing date June 24, 1897,) of which the following is a specification. Y

My invention relates to a new system of girders or beams for bridges and other metal constructions designed to be used in the place of the lattice-work girders employed at present.

The said invention has for its object to dispense with the use in lattice-work beams or girders of diagonal bars-that is to say, of triangulated bracing-and thus to simplify the lattice-work vby reducing it to a rectangular truss.

In triangulated lattice-work with pin-joints as employed in America the diagonal is an indispensable stay; but in lattice-work having rigid joints of the type in general use in Europe the diagonal becomes superfluous and therefore useless, for which reason I have dispensed with it by reducing the lattice-work to the verticale alone, whereby I have been led to the girders having arched openings, which constitute my invention. Y

Triangulated latticework with pin-joints of the American type has the advantage of being capable of being calculated with absolute accuracy, which is not the case with triangulated lattice-work having rigid joints of the European type,which are calculated solely according to Jthe formule of statics by assuming the joints to be pinned; but this is a hypothesis which experience has proved to be incorrect. The bars which are rigidly held at the joints are thus subjected by the deformations of the girder to bending strains,which produce stresses that are added to those which are due to the direct strains and act to increase the same very considerably; but if the American type has the advantage of absolute accuracy of calculation it also possesses numerous disadvantages-great complexity in the construction of the joints and in the rigid connection of the cross-girders of the flooring and of the wind-bracing to the pin-joints, Which connection must be made Without interfering with the movement ol the latter, thus causing considerable expense for labor, want ofsafety due to the necessary inclusion of forged parts, Wear of the joints after a certain time, and consequent mobility in the general connections of the framework, which produces on the passage of trains dynamical effects, shock, and very powerful hammering or jarring. p

I havel sought to produce a type of girder which shall be capable of replacing to advantage not only the lattice-Work with rigid. joints used in Europe, but also the American pinjointed lattice work, while possessing the same absolute accuracy of calculation as the pin-jointed type, avoiding the practical inconveniences `of pin-jointing, reducing the surface exposed to rusting, Vcausing a saving in labor in the Workshop and in erecting, and in most cases a saving in material. With this object I have invented a system of open-work Agirders or beams composed solely of booms and verticals without any diagonal connecting the foot of one vertical to the top of another vertical, and I have discovered an eX- act method of calculating for this kind of construction.

The accompanying drawings illustrate the construction of the` beams or girders of my system and also various types of said girders.

Figure 1 is a perspective view showing the application to the construction of a railwaybridge of girders having parallel and horizontal booms connected together by vertical members rigidly iixed thereto. Fig. 2 perspective view showing the application to the construction of a railway-bridge of girders having booms whichare not parallel and not symmetrical. Fig. 3 is a diagramillustrating a girder having non-parallel; symmetrical booms. Fig. 4 illustrates a portion of a girder having parallel booms with pin-joints in the upper and lower booms. Fig. 5 shows a portion of a similar girder with pin-joints in isaV IOO

' the lower boom only.

In these figures, l is the lower boom of the girders, C the upper boom, and D D the vertical members. E E, Figs. 4 and 5, indicate the pin-joints. Figs. ti and 7 show the method which I employ for calculating the constructions according to my invention, and the theory of which I shall set forth in a concise and clear manner, while repeating the statement that the possibility of exact calculation constitutes one of the most important advantages of myinvention. The method of calculation is based on the following principle: Taking a girder of any shape, Fig. (i or 7, letit be cut into two parts on the line M M at any height, but in such a lnanner as to intersect all the vertical members. Ateach section thus made there are at each vertical which is cut through three unknown forces-wiz., a direct strain X, a transverse strain Y, a couple or moment Z- and therefore there are as many times three unknown forces as there are vertical members. Now after deformation of the girder by the action of the load carried by it the section A of the vertical member is shifted by exactly the same amount, whether it be considered to belong to the upper part S of the girder or to the lower part I of the same. I take the section indicated at A in Figs. 6 and 7 and I consider it as belonging to the upper part S, and I designate it by AS. I estimate its displacement in a horizontal S sense and represent it by AH. l then estimate its displacement in a vertical sense and S call 1t Av, and, finally, I estimate its angub lar displacement and call it Ad. rlhese three I and AEL, as above,

tions- Ag Agi. A; Ag.. A: Ag).

Each vertical gives me three similar equations. I have therefore as many times three equations as there are vertical members and therefore as many equations as there are unknown quantities. Consequently the problem is solved-that is to say, I can determine all the unknown forces X Y Z which act upon each vertical member. I can therefore determine the exact stresses and dimensions of the several elements of the girders, and thc calculation of these is complete. In practice this general method can be greatly simplified. It should loe noted that ithas no recourse to any hypothesis. Itis solely and simply based on the two fundamental equations of flex` urelattice-work bridge shows that the type of construction which forms the subject of my present invention gives a strength equal to 1.75 times that of the lattice-work type with equal load, which renders my type in particular much lighter with equal strength.

Now in lattice-work bridges it is necessary that the verticals and diagonals should be fastened at their ends, with the result that the rivets alone carry the bending strains at their maximum; but my system allows of arranging intermediate joints J, Fig. 2, atthose places where the bending strains are smaller and. even of arranging them at the middle of the height ot' the vertical members, where the bending strain is equal to O.

The Savin g in labor is considerable with my system not only because the construction is more simple, but also because the larger parts can be sent out of the workshops in sections ready riveted together without risk of damage, with the result that the labor of erection is considerably diminished.

My system has the great advantage that the verticals are not subjected to any contingencyof collapse, this being a great drawback in all lattice-work bridges and more so in those with pin-joints. Finally, a bridge on my system will offer in the case of a train running off the line a resistance to the impact of a locomotive against the verticals sufficient to prevent its destruction and breaking down or collapse.

Instead of the upper and lower booms being continuous or rigid from one end of the girders to the other they may be made with a hinge or pin joint at the middle of the interval between two successive vertical members, as shown in Fig. 4, or even this hinging may only be provided in one only of the two IIO booms, as shown in Fig. 5. The position of the hinge is muchbetter than in the American pin-jointed type, because, first, each joint or connection consists only of the union of two parts, Whereas in the American lattice-work there are at least four parts, and, second, the pin-jointed connections are outside the connections of the cross-girders of the iooring and of the Wind-bracing, whence there results great simplicity of construction.

Having fully described my invention, what I claim, and desire to secure by Letters Patent, is-

1. A modified construction of girders or beams for bridges of the type known as lattice- Work, in which the diagonals are removed and the Vertical members rigidly connected to the booms by rounded pieces in such manner that the booms and vertical members form practically one piece, substantially as described.

2. A modified construction of girders or beams for bridges of the type known as lattice-Work, consisting solely of booms and vertical members made of rolled iron orsteel plates and angle-irons rigidly connected by rounded corner-pieces and rivets, but Without any diagonals connecting the foot of one Vertical member Witli the head of anothervertical member, substantially as described.

In Witness whereof I have hereunto set my hand in presence of two Witnesses.

ARTHUR VIERENDEEL. Witnesses: f

I-I. J. E. KIRKPATRICK, J. S. Kmizrfirmcn.

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