GB1560213A - Bridges - Google Patents

Description

(54) IMPROVEMENTS RELATING TO BRIDGES (71) I, ULF PAHNKE, a citizen of the Federal Republic of Germany of Hauptstrasse 18a, 8130 Starnberg, Federal Republic of Germany, do hereby declare the invention, for which I pray that a patent may be granted to me, and the method by which it is to be performed, to be particularly described in and by the following statement:- The invention relates to bridges either single-span or multi-span, with fixed or fixed and movable supports.

As is known, linear deformations occur in bridge structures that are not caused by external forces, such as for example moving or travelling loads or wind loads, but instead arise mainly as a result of changes of temperature of the structure, causing expansion or contraction.

If the movements of the superstructure, comprising deckportions or bridge girders, that are produced by these linear deformations were prevented by rigid bearings at the ends of the bridge, then locked-in stresses would arise which would dissipate a considerable proportion of the load-bearing capacity and stability of the structure and could possibly even destroy the structure.

For this reason all bridge structures are supported so that no or only slight locked-in stresses are produced by thermal expasion, creep and contraction. This is normally achieved by providing a rigid support in the form of joints, cup bearings or the like for each deckportion of the bridge superstructure or each bridge girder and having the remaining bearings in the form of roller or polymer bearings which allow movement longitudinally of the bridge, sufficient movement play being given to the free end or, in the case of continuous girders, the free ends. The mounting of rigid supports and the reliable transmission of the forces generated therein can usually be successfully accomplished in the case of a single-span bridge with short piers supported on good subsoil.The cost and material'involved in providing rigid supports are however often unacceptably high in the case of multi-span bridges, bridges having high piers or bridges supported on subsoil of poor load-bearing capacity.

Problems often occur even in the case of double-span railway bridges. In order to prevent large movements under the rails or rail expansion joints, the rigid supports are usually located on a middle pier, although they would be much safer if located at the bridge ends since the middle pier and its foundations have to absorb all the forces produced by starting up and braking of trains on the bridge.

The so-called "control rod" solution has been proposed for absorbing starting up and braking forces on piers in the case of long valley bridges on high piers. This proposes joining all the bridge girders with a rod securely anchored to both bridge ends. If the rod is secure against buckling or collapse, then all the bridge girders, which are held like beads knotted on a string, can dissipate by means of the control rod the accelerating forces generated by braking and starting of trains or other heavy vehicles, without the bridge superstructure or rails lying on bridge girders being overstressed. The same effect is obtained if the control rod is laid on a continuous floor slidably mounted on the girders and anchored at the bridge ends.

Apart from the increased construction costs, there are disadvantages with such control rod constructions, especially in the case of those formed as a solid bridge floor, since such constructions are unsuitable for arch bridges as the degrees of freedom of the line route is restricted. Moreover, high thermal stresses can arise in the control rod acting as a bridge floor, which stresses can cause cracks if the floor is not prestressed.

Large control rod cross-sections increase the danger of the formation of unstable states caused by pier deflections in the transverse direction. Small control rod cross-sections lead to high stresses on the rails in the case of railway bridges.

The danger of unstable states is further increased if the bridge floor formed as a control rod is not anchored as close as possible to the bridge ends but is continued therebeyond unanchored.

According to the invention there is provided a bridge having a superstructure comprising individual deck portions or girders whose juxtaposed ends are displaceably supported via interposed bearings on support piers, wherein each two juxtaposed ends are interconnected via a silicone based elastic-plastic composition located between co-operating opposed abutment surfaces provided either, by depending projections on the juxtaposed ends and complementary walls of a recess in the respective pier, or by a first plurality of spaced plate-like vanes, provided on a first member connected to one of the two juxtaposed ends, alternately interleaved in labyrinth fashion with a second plurality of spaced plate-like vanes provided on a second member connected to the other of the two juxtaposed ends.

Thus simply and economically in single or multi-span bridges locked-in stresses produced by temperature changes, creep and contraction can be avoided, with bridge support piers subjected to external forces directed substantially in the vertical direction only.

The elastic-plastic composition can accommodate long-term linear deformations resulting from creep and contraction and also daily and seasonal thermal expansions in an almost stress-free manner by virtue of its plastic properties, and accordingly significant locked-in stresses do not occur.

Short-acting acceleration forces produced by starting up and braking of trains and other heavy vehicles, and in particular also braking-conditioned jolts and jerks and centrifugal forces, and other forces acting intermittently in the horizonal direction, are diverted by way of the structural parts which are coupled together by means of the elastic-plastic composition, without loading the bridge support piers in an inadmissible manner.

The bridge support piers themselves are subjected substantially to vertical forces only, and are hot deflected, or only insubstantially, by horizontally directed loads. Railway lines and other carriageways can be laid in a simple manner because displacements of individual deckportion or girder end points can be kept small since the displacements can be dlstributed uniformly over the length of the bridge.

Silicone-based materials known commercially as "resilient mastic" are used as the elastic-plastic composition. These materials have the property that they react elastically to short-acting stresses and yield plastically to prolonged stresses, in the manner of a mastic rubber. The stiffness of the composition can be adjusted. It furthermore has the characteristic that its mechanical properties scarcely change over wide temperature ranges. Thus if differs essentially from conventional costing compounds of bitument or tar, and generally from cushioning and damping compositions.

Arrester means are advantageously provided, which prevent further movement of the ends of the deckportions or girders coupled together by the elastic-plastic composition, after a relative movement of determined extent has occurred. Such arrester means, which may for example comprise eye bars, cables or chains, prevent unallowably large movements occurring at the other coupling points when constructional parts are damaged or deflected, and thereby prevent further damage.

The abutment surfaces and/or tie elements connected to the ends of the area floors or girders allow displacements over a limited spring deflection.

Such abutment surfaces and/or tie elements can comprise labyrinth-like, interengaging plate-like vanes disposed spaced apart from one another, and secured via girders to the justaposed ends of two deckportions. These can serve to transfer coupling forces, such as compression, traction, thrust or bending forces, to the elastic-plastic composition, and can be secured in simple manner to the deckportions, girders or bearing parts. The abutment surfaces and. or tie elements may be provided with contact means for the elastic-plastic composition, which are formed like buffers having flat, arched, smooth, rough, corrugated, knobbed or cammed surfaces so as to allow a good force transfer to the composition.

The abutment surfaces and/or tie elements may also have bars, rods or like means that project into the composition and subject it to thrust forces or shear forces, when parts mounting them move. The bars or rods may also project into openings in oppositely disposed coupling pieces, and may be provided with stays, rings or screw-like formations. The openings in the counterpart pieces may also have internal flanges, stays, cams or screw-like raised portions that prevent flow movement of the elastic-plastic composition, or enlarge the flowpaths in a desired manner.

The elastic-plastic composition may be enclosed by flexible tubing, sleeves, membranes, bellows, pipes, grooves, channels or like means so as to prevent the composition leaving the space between the abutment surfaces and/or tie elements. The enclosing elements are preferably resilient so that movements as force-free as possible can take place between the abutment and/or tie means. The enclosing elements should also be designed so that specific movements are promoted or prevented. To this end, they may for example contain coiled springs.

The enclosing elements may be applied so as to extend from securement part to securement part, but in each case should envelop only one securement part and on the other hand should surround bars or rods situated between the securement parts more than one space being surrounded with elastic-plastic material per coupling piece.

The surrounding covering may also be arranged between the structural parts to be joined, the enclosed space being completely or partially filled with the elastic-plastic material.

Spring elements may also be combined, between the structural or securement parts with the coupling pieces so as to prevent undesired variable movements between the structural parts, or compensate for such movements if they have already occurred.

Depressions, clearances, recesses, cavi ties, troughs or the like may be formed in parts of the bridges, bridge decks and also in the pier heads, into which project coupling parts or parts to be coupled having spikes, cams, rods, claws or the like.

The coupling is formed by completely or partially filling, pouring, casting or inserting elastic-plastic material in the interspaces or gaps.

The surfaces of the cams, spikes and/or depressions can be fully or partially provided with elastic bearing surfaces so that a protective contact is formed in the case of fairly large movements. The size of the interspaces and their constructional shape, by which the elastic-plastic material is subjected more to thrust or more to normally directed forces, also enables an intercepting or safety effect to take place after a certain displacement and thereby prevent unallowably large movements occurring. An intercepting and/or spring effect can also be obtained if separate or interconnected coupling and spring elements are employed. The "rigid supports also can be formed by the elastic-plastic coupling according to the invention.

The invention is diagrammatically illustrated by way of example in the accompanying drawing, in which: Fig. 1 is a longitudinal section through adjacent deckportions, of a bridge according to a first embodiment of the invention, supported on a pier and connected to one another by an elastic coupling; and Fig. 2 is a view similar to Figure 1 but of a second embodiment of a bridge according to the invention.

Referring to the drawing and firstly to Figure 1, a support pier 1 supports the juxtaposed ends of deckportions 2 and 3 of the bridge by way of sliding bearings 4, 5. A plurality of cylindrical vessels 6, only one of which is shown, of circular or polygonal cross-section are firmly secured to the end face of the deckportion 2, plate-like or web-like radially inwardly extending vanes 9 being secured to the walls of each of said vessels. A respective rod 7 extends into each vessel 6 and is secured to the end of the opposite deck-portion 3. Radially outwardly extending vanes 8 are secured to the rod 7 and extend into gaps between the vanes 9.The cylndrical vessel 6 is completely filled with an elastic-plastic composition 13 and is closed by an end cap 10, secured to the vessel 6 and having clamping straps 11 extending around the rod 7 and clamping straps 12 extending around the vessel 6, so that the elastic-plastic composition 13 cannot flow out but damps and absorbs forces producing longitudinal expansion or contraction of the deckportions 2, 3.

If displacements occur which are greater than the distance between the vanes 8, 9, the vanes abut and press against one another and thereby produce a rigid coupling of the deckportions 2, 3, with the result that unallowably large displacements are prevented.

In the embodiment shown in Figure 2, the upper end of a pier la supports deckportions 14, 15 by sliding bearings 4a, 5a and is provided with a trough-shaped recess 18 into which an elastic-plastic composition 13 is cast. The ends of the deckportions 14, 15 of the bridge are provided with downwardly directed projections 16, 17 which dip into the elastic-plastic composition 13. The deckportions 14, 15 are thus coupled together by the composition 13 which damps and absorbs forces producing longitudinal expansion of the deckportions 14, 15.

Unallowably high displacements are prevented by the ends of the deckportions 14, 15, after reaching the permitted maximum movement, either pressing against one another in the case of expansion or, by way of their projections 16, 17, pressing against the edges of the trough-shaped recess 18 in the case of contraction.

WHAT I CLAIM IS: 1. A bridge having a superstructure comprising individual deckportions or girders whose juxtaposed ends are displaceably supported via interposed

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (7)

**WARNING** start of CLMS field may overlap end of DESC **. surfaces and/or tie elements. The enclosing elements are preferably resilient so that movements as force-free as possible can take place between the abutment and/or tie means. The enclosing elements should also be designed so that specific movements are promoted or prevented. To this end, they may for example contain coiled springs. The enclosing elements may be applied so as to extend from securement part to securement part, but in each case should envelop only one securement part and on the other hand should surround bars or rods situated between the securement parts more than one space being surrounded with elastic-plastic material per coupling piece. The surrounding covering may also be arranged between the structural parts to be joined, the enclosed space being completely or partially filled with the elastic-plastic material. Spring elements may also be combined, between the structural or securement parts with the coupling pieces so as to prevent undesired variable movements between the structural parts, or compensate for such movements if they have already occurred. Depressions, clearances, recesses, cavi ties, troughs or the like may be formed in parts of the bridges, bridge decks and also in the pier heads, into which project coupling parts or parts to be coupled having spikes, cams, rods, claws or the like. The coupling is formed by completely or partially filling, pouring, casting or inserting elastic-plastic material in the interspaces or gaps. The surfaces of the cams, spikes and/or depressions can be fully or partially provided with elastic bearing surfaces so that a protective contact is formed in the case of fairly large movements. The size of the interspaces and their constructional shape, by which the elastic-plastic material is subjected more to thrust or more to normally directed forces, also enables an intercepting or safety effect to take place after a certain displacement and thereby prevent unallowably large movements occurring. An intercepting and/or spring effect can also be obtained if separate or interconnected coupling and spring elements are employed. The "rigid supports also can be formed by the elastic-plastic coupling according to the invention. The invention is diagrammatically illustrated by way of example in the accompanying drawing, in which: Fig. 1 is a longitudinal section through adjacent deckportions, of a bridge according to a first embodiment of the invention, supported on a pier and connected to one another by an elastic coupling; and Fig. 2 is a view similar to Figure 1 but of a second embodiment of a bridge according to the invention. Referring to the drawing and firstly to Figure 1, a support pier 1 supports the juxtaposed ends of deckportions 2 and 3 of the bridge by way of sliding bearings 4, 5. A plurality of cylindrical vessels 6, only one of which is shown, of circular or polygonal cross-section are firmly secured to the end face of the deckportion 2, plate-like or web-like radially inwardly extending vanes 9 being secured to the walls of each of said vessels. A respective rod 7 extends into each vessel 6 and is secured to the end of the opposite deck-portion 3. Radially outwardly extending vanes 8 are secured to the rod 7 and extend into gaps between the vanes 9.The cylndrical vessel 6 is completely filled with an elastic-plastic composition 13 and is closed by an end cap 10, secured to the vessel 6 and having clamping straps 11 extending around the rod 7 and clamping straps 12 extending around the vessel 6, so that the elastic-plastic composition 13 cannot flow out but damps and absorbs forces producing longitudinal expansion or contraction of the deckportions 2, 3. If displacements occur which are greater than the distance between the vanes 8, 9, the vanes abut and press against one another and thereby produce a rigid coupling of the deckportions 2, 3, with the result that unallowably large displacements are prevented. In the embodiment shown in Figure 2, the upper end of a pier la supports deckportions 14, 15 by sliding bearings 4a, 5a and is provided with a trough-shaped recess 18 into which an elastic-plastic composition 13 is cast. The ends of the deckportions 14, 15 of the bridge are provided with downwardly directed projections 16, 17 which dip into the elastic-plastic composition 13. The deckportions 14, 15 are thus coupled together by the composition 13 which damps and absorbs forces producing longitudinal expansion of the deckportions 14, 15. Unallowably high displacements are prevented by the ends of the deckportions 14, 15, after reaching the permitted maximum movement, either pressing against one another in the case of expansion or, by way of their projections 16, 17, pressing against the edges of the trough-shaped recess 18 in the case of contraction. WHAT I CLAIM IS:

1. A bridge having a superstructure comprising individual deckportions or girders whose juxtaposed ends are displaceably supported via interposed

bearings on support piers, wherein each two juxtaposed ends are interconnected via a silicone based elastic-plastic composition located between co-operating opposed abutment surfaces provided either, by depending projections on the juxtaposed ends and complementary walls of a recess in the respective pier, or by a first plurality of spaced plate-like vanes, provided on a first member connected to one of the two juxtaposed ends, alternately interleaved in labyrinth fashion with a second plurality of spaced plate-like vanes provided on a second member connected to the other of the two juxtaposed ends.

2. A bridge according to claim 1, wherein the plate-like vanes are provided with helicoidal formations.

3. A bridge according to claim 1 or claim 2, wherein the first member is a cylindrical vessel filled with the elastic-plastic composition and provided on its inner surface with the first plurality of plate-like vanes and wherein the second member is a rod provided with the second plurality of plate-like vanes.

4. A bridge according to any one of claims 1 to 3, including arrester means rigidly to join together the juxtaposed ends of the deckportions or girders coupled by the elastic-plastic composition upon relative movement beyond a permitted maximum.

5. A bridge according to claim 4, wherein the arrester means comprise abutment and/or tie elements connected to the juxtaposed ends of the deckportions on girders and which allow a limited displacement movement via springs.

6. A bridge according to claim 5, in which the springs act only after a determined displacement.

7. A bridge substantially as hereinbefore described with reference to Figure 1 or Figure 2 of the accompanying drawing.