US893640A - Reinforced girder. - Google Patents

Description

No. 893,640. PATENTED JULY 21, 1908.

E. A. MOGCETTI. REINFORCED GIRDER.

APPLIOATION FILED APR.18, L105.

2 SHEETS-SHEET 2.

IUITE ERNST ARNOLD liIOCOETTI, OF PARIS, FRA YCE.

REINFORCED GIRDER.

Specification of Letters Patent.

Application filed April 18, 1905.

Patented July 21, 1908.

Serial No. 256,253.

To all whom it may concern:

Be it known that I, ERNsT ARNOLD Moc- CETTI, a citizen of the Republic of France, residing at Paris, France, have invented new and usefulIm rovements in Reinforced Girders, ofwhich the following is a specification.

This invention relates to compound girders which, from their nature and the arrangement of the materials forming them, are in most cases better suited than the majority of girders as heretofore made for the eflicient bridging oflarge spans and the support of heavy loads.

In Figure 1 a girder made according to the inventionis shown in its general form. Figs. 3 to 14 illustrate the application of the principle employed in the construction of the girder to a number of different types of girder work. Figs. 2, 4 and 8 are cross sections on the lines m-m of Figs 1, 3 and 7 respectively.

The girder illustrated in Figs. 1 and 2 consists simply of a number of tension members 2 for takmg up the tensile forces and a number of compression bodies or members (1 which are introduced between the tension members. The tension members are connected together at a oint A and extend from this point in boti directions towards the compression zones of the girder. They are bent polygonally or in continuous curves and, if necessary, are provided with branches such as Z (Fig. 1) for increasing the tensile strength. The ends of the tension members are bent around and on to the free surfaces of the compression body as at a (Fig. 1).

The compression members are either in-' serted between the tension members or are poured or cast therein according to their nature; each body can be composed of one or more materials. Furthermore, each of the compression members can wholly occupythe space between two tension members or may only partially occupy such a space. In

the latter case the compression bodies between the tension members are arranged as rods; the girder is, in this case, a lattice or framework irder (Fig. 10). The various structures, t herefore, are built u girders, the resistance of which varies witi the nature of the materials employed. The latter do not need to possess any adhesion between themselves; the load capacity of the girder is not injuriously affected if care be taken that the compression bodies are always maintained compressed against the tension members.

By the combination of two or more girders constructed as above described, structures as usually employed for building purposes areobtained.

The rivets or bolts which effect the connection of the tension members'at the point A do work only under a one-sided load or with the unsymmetrical arrangement of the tension members, and prevent the said members from sliding apart from one another at the said point, which would otherwise be the case. W'hen, therefore, the tension members are arranged symmetrically and the load is symmetrical, or approximately symmetrical, which would be the case, for ex ample, with girders the weight of which is large compared with the load, then the connection at the point A may be dispensed with.

The bending of the ends of the tension members, as above remarked, gives rise to a greater effect the less the friction or adhesion existing between the tension members and the compression bodies. According to the importance of these factors with respect to the stresses in the tension members the said bends can be partially or wholly dispensed with. Adhesion between the compression members and the tension members also results in the removal of load from the rivets or bolts at the point A. The latter are, therefore, in many cases, unnecessary.

In connection with the construction of the different beam elements I proceed as follows. For the tension members, iron or steel lamellae are best adapted. Each tension membercan consist of a single iron bar (Fig. 2) thew'idth of which is equal to the thicknessof the girder, or it may be composed of a number of adjacent fiat bars (Fig. 4). The latter arrangement is to be preferred in bridge construction and permits of the employment of verticals between the separate ars of the individual tension members for connection to the road beam.

For the compression members freestone, artificial stone, concrete, reinforced concrete, cast iron or steel, that is to say, materials having a high compressive strength, are advantageously chosen. In cases where a number of different materials are present in the same compression body or member the strongest material is used at the points which are subjected to the heaviest stresses.

members a that they girder shown in Fig. 1 may be taken as a type.

- The structure illustrated in Fig. 3 is a simle beam mounted upon two supports. lach of the tension members 2 consists of a number of adjacent flat iron bars. They are. so curved or bent that they intersect the compressive forces in the compression bodies or proximately at right angles at all points. T16 tension members are, in the neighborhood of the supports, made only of cement concrete C; towards the center they consist of slag concrete S and ranite blocks g. The latter are also used at t e upper part of the beam, where the. compressive stresses are the greatest. The surfaces of the stone blocks which are in contact with the tension members, are carefully pre ared and are curved similarly to the iron ars; the lower surfaces or faces are also made with a slight curvature in the direction of the compressive forces, so that no strain is set up between the concrete and stone. The joints through which the tension members pass are provided with a paper or asbestos insertion for the better transmission of the compressive stress, but they can be filled also with a substance of greater strength, such for example, as lead or cement without an addition of sand. At the points at which the distance between the tension members is too great to be spanned by a single block, the compression bodies are each provided with. a number of stone blocks. The new joints are also curved and, as before, are provided with an insertion or the filling; they can, however, be made similarl to the others by means of shorter iron bars is (Fig. 3) which pass through the joints and are anchored in the lower concrete so that the different elements of the same pressure member are rigidly connected together.

Another method of obtaining shorter stone blocks is shown in Figs; 5 and 6. The iron bars 2 of each tension member are no longer arranged in the same plane, but are displaced with respect to one another. The principle of construction remains the same, since the new beam can be regarded as the combination of three separate adjacent beams the thickness of which is approximately equal to the width of the iron bar and wherein each of the tension members consists of a single iron. bar. At those points at which the strength curved and arranged as in the preceding case. The compression members consist of cement concrete 0 and stoneblocks g. As inthis case the tension members at their central parts possess a tendency to straighten, they are retained in their proper positions by means of iron supports 12 (Figs. 7 and 8). The tension members run in straight lines between the lower ends of the supports. The function of the metal supports is thus to take up special tensile stresses which are set up a in consequence of the shape of the tension members. Their lower ends are formed as shown in Figs. 8 and 9 for practical reasons, and can be connected to the tension members in any suitable manner. The supports are thus in effect not new elements or members of the beam but are rather to be regarded as branches of the tension members. The structure illustrated in Fig. 7, therefore, can be considered a beam with branched tension members which are bent partially in curves and partially polygonally.

Fig. 10 represents a simple beam with rodlike compression members. The tension members, which are assumed to be branched inorder to show the girder in its general form, consist, as in the two preceding constructions, of flat iron bars arranged adjacent to one another. For the compression members cement concrete 0, reinforced concrete (1 and granite g are chosen. The separated rods g, c and a serve the same function as the blocks 9 and concrete S of the previously described figures. The girder forms an open- 101) work structure which may be regarded theoretically as follows Figs. 11 and 12 are details of connections between the tension and compression members of Fig. 10. At the angular points a 105 slight curvature is given to the tension members for more equable transmission of the compressive stresses. Furthermore, at these points angle. irons w are arranged in order to prevent the compression members from sliding. As the compression members are a plied directly at t e angles (Fig. 11) for t e etter transmission of forces they must not' be subjected to the action of tensile forces; where this condition cannot be fulfilled by reason of the varying load the iron insertion at the aforesaid angle extends through the iron bar forming each tension member (Fig. 12) so that the pressure rods are rigidly se, cured at the angles. In the same manner the tension members which, under certain circumstances, may be subjected tocompressive forces must be stiffened with angle irons or with concrete jackets (Fig. 12). The tension members, in case they are not stiffened in any way must obviously run in straight lines between the joints. In cases Where, as in Fig. 10, the tension members are made with s ecial branches Z the latter must be fitted to the joints; fastening is effected by means of simple rivets or bolts. The connection of the tension members at the point A is, in this case, of still greater importance than in the case of beams with solid compression members. It is, in practice, always necessary, even in the case where no tension member extends from the point in question and can only be dispensed with in the case of the quite symmetricalarrangement of the tension members in combination with symmetrical loads.

Fig. 13 illustrates an arch structure. It consists of two girders connected together by a link G The tension members are curved and finished as in the case of the girder shown in Fig. 3. Cement-concrete C and stone blocks 9 are used for the compression members. Further details are obvious from the drawing without further explanation. In order that compressive forces shall always exist in the compression members the arch is provided with links G, G and G and its curvature is so chosen that the .neutral axis is always outside the pressure lines corresponding to the varying oa s.

Fig. 14 illustrates a girder beam which is made of'three separate girders connected together. The projecting central beam is supported upon two metal supports C and D and the end girders rest upon t e ends of the central girder and u on the outer supports B and F respectively. The tension members -2 of the end girders are curved and arranged as in the case of the structure shown in Fig. 7 and are provided with iron supports 1) on account of their curvature as before. of cement-concrete C and granite blocks g. In the case'of the central girder the tension members are also so curved that they intersect the direction of the compressive stresses practically at right angles and consist of adjacent flat iron bars. For the compression members on the other hand, I can use: (1)

Cement-concrete C, granite blocks g and cast iron e for the overhanging portions of the structure. (2) For the central parts of the central girder slag concrete S granite blocks 9 and cast iron 6. For downwardly directed forces the suspended end girders are only subjected to positive bending moments. The ends of the tension members must in this case and for this reason he arranged at the u per edge of the beam. In

those parts of t e overhanging girder adj a-.

The compression members consist as have also occurred in the structures illustrated in Figs. 1 and 10. As the bending moments are considerably greater above the middle supports C and D than in the middle of the central girder, the number of the tension members at the last named oints may be less than over the supports.

he outer tension members are for this reason made of short lengths 2 and are connected together by rivets or bolts in the manner indicated in Fig. 14. By reason of the high value of the bending moments above the supports the compression members are made of cast iron 6 at these points.

The connection of the end girders to the central structure is, in the arrangement in Fig. 14, effected simply by the connection (by riveting as shown or otherwise) of the outermost tension members :2 2 The tension members of the suspended beams can be therefore regarded as branches of those of the central girder or, more generally stated, the tension members of any two single girders can be regarded as branches of the tension members of the third girder. The structure illustrated in Fig. 14 is very nearly related to that illustrated in'Fig. I. It is a girder with partially polygonal and partially curved and specially branched tension members. Between the tension members 2 2 a short flat iron bar f is introduced in order that the floating parts may be actually linked above the central overhanging girder. If the iron bar f be dispensed with, the girder in Fig. 14 becomes a continuous beam upon four supports.

Having now particularly described and ascertained the nature of my said invention and in what manner the same is to be performed, I declare that what I claim is:

1. A girder composed of tension and compression members, the tension members bepressure zones, the spaces between the tension members being occupied by compression members of varied degrees of strength in positions corresponding to the varied compressive stresses in the girder.

- 2. A girder composed of tension and compression members, the tension members be ing brought close to each other at the point tersect the compressive stresses at approxi-- mately right angles throughout the whole of the compression members.

3. A girder composed of tension and compression members, the tension members being brought close to each other at the point. where the tension is greatest, and being extended in diverging lines from this oint to the portions of the girder in which. t e coinpression is greatest and in which their extremities lie, so as to divide the girder into pressure zones, the spaces between the ten- .sion members being occupied by material adapted to resist compression, the compression members being composed of concrete S and blocks of hard material 9, the latter being arranged at the points where the greatest compressive stresses exist.

4. A girder composed of tension and compression members, the tension members being brought close to each other at the point where the tension is greatest, and being extended in diverging 'lines from this point to the p rtions of the girder in which the compression is greatest and in which their extremities lie, so as to divide the girder into pressure zones, the spaces between the tension members being occupied by material adapted to resist compression, the compression members being composed of concrete S and blocks of hard material g, the latter being arranged at the points where the greatest compressive stresses exist, and said tension members being bent in a direction to intersect the compressive stresses at approxi-' mately right angles throughout the whole of the compression members.

' 5.- A girder composed of tension and compression members, the tension members being'brought close to each other at the point Where the tension is greatest, and being. extended in diverging lines from this point to the portions of the girder in which the compression is greatest and in which their extremities lie, soas to divide the girder into pressure zones, the spaces between the tension members being occupied by material adapted to resist compression, the compression members being composed of concrete S and blocks of hard material g, the latter being arranged at the points where the greatest compressive strains exist, and said blocks being connected with the concrete by means of metal bars k.

6. A girdercomposed of tension and coming brought close to each other at the point where the tension is greatest, and being extended in diverging lines from this point to the portions of the girder in which the compression is greatest and in which their extremities lie, so as to divide the girder into pressure zones, the spaces between the tension members being occupied by material adapted to resist compression, the compression members being composed of concrete S and blocks of hardmaterial g, the latter being arranged at the points where the greatest compressive strains exist, and said blocks having their lower faces so curved that no strain exists longitudinally of them.

7. A girder composed of tension and compression members, the tension members being, brought close to each other at the point where the tension is greatest, and being extended in diverging lines from this point to pression is greatest and in which their extremities lie, so as to divide the girder into sion members being occupied by material adapted to resist compression, the compression members being composed of concretelS and blocks of hard material g, the latter being arranged at the points where the greatest compressive strains exist, and said blocks having their lower faces so curved that no strain exists longitudinally of them, and said tension members being bent in a direction to mately right angles throughout the Whole of the compression members.

8. A girder composed of tension and com -pression members, the tension members being brought close to each other at the point where the tension is greatest, and being extended in diverging lines from this oint to the portions of the girder in which t e compression is greatest and in which their extremities lie, so as to divide the girder into pressure zones, the spaces between the ten sion members being occupied by material adapted to resist compression, the compression members being composed of concrete S and blocks of hard material g, the latter being arranged at the points where the greatest compressive strains exist, and the tension j acent planes. I 9. A girder composed of tension and compression members, the tension members being brought close to each other at the point where the tension is greatest, and being extended in diverging. lines from this oint to theportions of the girder in which t 1e comi pression is greatest and in which their exthe portions of the girder in which the com-.

pressure zones, the spaces between the 'ten-' intersect the compressive stresses at approximembers being arranged in a plurality of adpression members, the tension members betremities lie, so as to divide thE-i girder into In witness whereof, Ihave hereunto signed pressure zones, the spaces between the tenmy, name in the presence of two subscribing 10 sion rlnemhers beiicilgdoccupiedfby compression witnesses. a mem ers o varie egrees 0 strength in o- 5 sitions corresponding to the varied compre ss- ERNST ARNOLD MOCCETTI' ive stresses in the girder, and metal supports Witnesses: p connecting said tension members to the up- MARCEL ARMENGAUD, J eune., per part of the girder. HANSON C. COKE.

Images