Lattice of bridge, span of bridge comprising such lattices and a method for building the span.

The invention relates to the® bridges,

A known technique for making a bridge comprises elementary cross sections are prefabricated bridge and to place these sections in situ by means of a beam launch, all the sections component ' a bay being held in cantilever prior to incorporation into the final structure.

This construction technique was used particularly for effecting the bridge Bubiyan at Kuwait (review "jobs", volume of no. 571, November 1982, page 38 to 46) with a loriguor of cantilever of the order of 40 meters, this which made already performance.

The technique provides with the cantilever provides. provides cycles shorter than with all other known techniques but is quickly limited by the weight of the assembly in cantilever since excessive weight would result in a beam launch of a size, a weight and a cost prohibitive.

An object of the present invention is to enable a bridge using the described method with a length of cantilever up to 200 meters, without requiring a beam launch exhorbitante.

This is achieved, according to the present invention, by the fact that prefabricated sections transverse bridge consisting essentially a three-dimensional mesh - like design prestressed concrete high strength and free of any slab, that by locating these cross sections by in situ and laid, on the set of cross sections of a bay, the elements that will build the middles of the slab.

High strength concretes are common knowledge? especially by work.

With grated cheese FREYSSINET (FS " e.g. the French patents 764,505? 781,388? 797,785 and second addition 46,379 French patent 122 338) but are essentially remained until now one laboratory concrete "the applicant has developed a technique for performing industrially these concretes and this technique has been applied for Patent French 83, 10057 deposited 17 June 1983" this technique enables in particular beams of the EH concrete having a work rate in the range 50 - 100 mpa or allowable upper? while the rate of permissible operating of a prestressed concrete girder conventional is of the order of 10 - 20 MPa at "

In a bridge made in accordance with the present invention? the resistance of the beam to longitudinal bending is provided by the mesh? the slab nothing that the transverse bending strength "

The three dimensional lattice elemental bars ^ prestressed concrete high strength is in itself a new product which constitutes one aspect of the invention "

In a typical example, the bars are arranged? each? in two horizontal planes one above the other with a space between the planes and the other? obliquemenfc in this space? to connect the two planes? the group of bars being held in. the configuration chosen by connective blocks cast concrete "

In each of the parallel planes the bars are placed in provisions which are chosen at will? the measures the more common being the measures according to the sides of a rectangle? the layouts along lines connecting the centers of the sides of a rectangle, the layouts along lines connecting the center of a rectangle at the vertices or at the middle of the sides of a rectangle and the measures according to the posts and the rungs of a ladder. These examples are not limiting.

The bars disposed in the space between the two planes are distributed preferably in vertical planes each, other in planes inclined to the vertical.

The linking block bars are preferably pretensioned triaxialement blocks and the initial stress is preferably conducted by tendons bars which terminate in the blocks. The blocks themselves can advantageously be prestressed concrete high mechanical strength.

The slab of a bridge according to the invention may be a metal slab or a concrete slab and typically consists of cross sections of the prefabricated slab which are layered one after the other. When the cross sections are concrete, they are preferably conjugated, it is to say that the operation of the end face of a section already performed as one of the form wall of the next section.

Similarly, the blocks of two adjoining grid are preferably conjugated blocks.

The following will describe an example embodiment of a lattice element according to the invention, with reference to the drawings of the seal design, the specification and drawings showing other features of the present invention.

figure 1 - is a perspective of a

example elemental mesh;

figure 2 - is a portion of a cross section of the mesh that the mesh after elementary confectioneries been placed and has received a slab section of the bridge;

figure 3 - is a schematic of an exemplary apparatus unit and road elemental mesh;

figure 4 - is a longitudinal sectional view of a truss member in. during manufacture, and

figure 5 - is a cross section of the bar of Figure 4.

It has already been explained that the elementary lattice, it is to say the cross-section of mesh which, by assembly further and with same or similar sections, will constitute a jacket of a bridge framework, can have many different configurations. Figure 1 is an example configuration that has been specifically designed but which would not be considered limiting.

In this example, it is noted that the following features:

- The mesh comprises a lower plane comprising bars p1 p4 to disposed along the sides of a rectangle whose vertices are formed of blocks binding, b., C., D..

- The mesh comprises an upper plane comprising bars p5 p14 to arranged according to the sides of two rectangles kissing whose vertices are made even blocks of link e to j, the common side fi and the two opposing sides and gh JE also having the middle part thereof blocks binding of L, m and K and, other bars p15 to p18 connecting diagonally the M block to blocks f and I and the unit K F and I to the blocks.

- The two planes are connected by bars rising from lower blocks and resulting in some of the larger blocks, each Ρ 21, 22 Ρ, p27 and p28 located in two vertical planes determined respectively by the blocks C, D., I and the A blocks, b., w, other Ρ 19, 20 Ρ, p25 and p26 located in two inclined planes determined respectively by the B blocks, c and K and A, d and m, both planes being further connected by bars 23 Ρ, p24, p29 p30 and arranged along the edges of a pyramid whose base is formed by the blocks, and b, c and d and whose apex is the unit L.

In this example embodiment, we split each truss member.

These bars are fabricated by any suitable technique and, illustratively, will describe further manufacturing technique.

The shape and dimensions of the cross section of a bar are selected at will. Particular preference is given to the cylindrical rods having a diameter in the range of 25 to 35 cm.

For performing the trellis, prefabricated bars are placed in the desired relative positions, we place formworks for blocks and binding and are cast blocks. If to complete blocks of concrete joint high strength, formworks used injection pressure resistant concrete (e.g. 50 to 60 bar).

A typical mesh has a weight of 5 tons

per linear meter for a bridge 18 m wide. With a beam which can lay 1,000 tons, may thus range of 200 meters.

The shown 2 is a vertical section through the mesh in place after a slab element V has been placed on the mesh.

Figure 3 is an enlargement of one of the blocks of assembling the frameworks of the shown 2. In this example, the unit being preloaded by the cables triaxialement 1, 2, 3 from horizontal bars and rising 4.5 6 and ending in the block. The tendons connect the bars and the block. The preload that existed in the bars pass in the node and the bars create dice bearing pressure in the block. These cables 1.2, 3 are tensioned prior to, during or after the casting of the block.

Further, certain blocks such as that represented in Figure. 3 are traversed freely by cables, because the cables 7, which are tensioned when the assembly truss of a bay has been put in place. These cables, which are cables biasing assembly, make up a longitudinal prestress and contribute to the overall strength of bending.

Figures 4 and 5 are related to a method of making a truss member in which radiation curing of concrete of the bar into a straight tubular casing surrounded by a band, by compressing the concrete during taken along the axis of the shell particles with a pressure of the range 50 - 150 mpa, the longitudinal compression creating transverse thrusts in the concrete which rotate the hoop tensioned around the tubular casing.

For example (Figure 4 and 5) is placed, preferably vertically, a cylindrical tube 1 ', for example in a thin sheet with a thickness of about 2 mm or cardboard or plastic, the tube wall having multiple drain perforations 4' and surrounding the tube a double ferrule constituted by two steel wires 2 ', 3' which are helically wound around the tube, respectively in the clockwise and counter-clockwise direction. At this point, the winding 2 'is in contact with the tube 1' and the winding 3 'surrounds the winding 2' but they are not deformed.

Means are provided for fixing each end of a winding assembly relative to the corresponding end of the other winding, for example by fixing both ends thereof onto means also maintains these ends to one end of the tube .1 '. An example of such a means is a ring 6 'which surrounds the tube 1' and is fixed in position relative to the tube 1' and to which is attached the two corresponding ends of the fret wires. There is one such circle at each end of the tube 1'.

Arranged inside the tube one or more longitudinal drain 5 'which are preferably made from steel tubes generally thicker than the tube 1' when it is steel, e.g. a wall thickness of 4 to 6 mm.

The material and thickness of the tubular casing 1' are chosen so that the tube distributes the stresses and resists shearing by the hoop.

Is introduced into the space between the outer tube 1 'and the drain 5' the components of the concrete, is for example a mixture of aggregates, sand, cement and water, mixture known per se. The aggregates have, a priori, the same type as the aggregates of a conventional concrete, but are preferably selected from the high end of a concrete aggregates: aggregate rock resistant to values between 200 - 300 mpa (some limestone, sandstone, andc...). The binder may also be a binder such as those used for the conventional concretes including the resin binding. The percentages of aggregate and binder may be the same as those of conventional concretes.

The mixture is compressed to axial pressure 7 'of 50 - 150 mpa before and during the engagement, to hardening concrete comprising a portion of the water is removed through the ports 4' of the outer tube 1 'and by the drain 5' (note that the openings 4' may be simple pore).

To perform the axial pressure while avoiding buckling of the tube, it is recommended, as 1' a, to bring one of the other two plates inserted respectively at one end and at the other end of the tube. This approximation is obtained for example by means of one or more prestressing cables passing in the concrete and pulled by a jack. One such device is shown schematically in Figure 4 vindications the two pressure plates 8 ', 9' which one is pulled toward each other by wires 10 ', 11' actuated by a cylinder 12' which bears on the other plate. Advantageously, the cables 10 ', 11' pass through tubes drain 5'

The compression is performed constantly or not, and continuously or not.

Under longitudinal compression of the béboh, the frets is thus effected tend and confined compressive, the frets invests pressure planes transverse and axial pressure by making the pressure in the third dimension.

In some cases, for example in long bars, it is envisaged that the operation by successive layers of concrete, pending the taking of a layer for the next layer.

A typical process to bridge according to the invention includes performing the operations where ii

- is precast prestressed concrete bars high-strength;

- is performed with these bars elementary three-dimensional lattices where they are joined by connecting blocks cast;

elementary lattice - are laid side-by-side in-situ using a beam Annacis is repeated until a set in cantilever having a desired length for the bay.;

the R is prepressurized assembly;

- slab components is placed on the set of elementary lattice to form the slab of the bay.

The prestressed concrete slab will be generally high strength, but may also be metal.

The invention is not limited to the exemplary embodiments which have been described..