EP4245919B1 - Expansion joint between two concrete slabs suitable for passing automatically guided vehicles - Google Patents

Description

Technical area

The invention relates to the technical field of expansion joints between two adjacent concrete slabs, capable of resisting and following the movements of the slabs after retraction of the concrete.

Prior art

In the field of construction, and in particular that relating to ground covering with concrete slabs, it is well known to use expansion joints between the slabs, adapted, on the one hand, to create a space of air necessary for the absorption of variations in volume of a slab, for example under the action of shrinkage, and on the other hand, to resist and follow the movements of the slabs, for example during the movement of heavy loads stored on slabs or during earthquakes.

Nowadays, logistics buildings have increasingly large floor areas, and are managed almost automatically by means of automatically guided vehicles which circulate on the ground to transport objects of all kinds, such as packages. For example.

The automatic drive of this type of vehicle means that the ground surface must be free of any defect that could cause impacts and jerks to the wheels of the vehicle when traveling.

The new constraints generated by the use of these automatically guided vehicles mean that the distance between two longitudinal elements of an expansion joint, after retraction of the concrete, must be relatively small, in particular of the order of 4 to 10 mm, if necessary, these automatically guided vehicles fault and therefore stop.

To remedy this problem, it is known to act on the composition of the concrete so that its shrinkage, after drying, is as low as possible, but the results are not yet in line with expectations.

The space generated between two longitudinal elements of a straight edge expansion joint is incompressible due to the shrinkage of the concrete. In practice, the shrinkage can take the form of an opening which can vary between a few millimeters to 10 to 20 mm, or even 20 to 25 mm, for example in cold rooms.

To remedy this problem, it is known to produce expansion joints comprising two longitudinal elements having sinusoidal profiles joined to each other so as to engage crests of one element with hollows of the other element. Furthermore, the French standard NF DTU 13.3 now requires the installation of an expansion joint with longitudinal elements with sinusoidal profiles when vehicles traveling on concrete slabs make more than 250 passes per day over the expansion joints.

In practice, each sinusoidal element is intended to form an integral part with an upper and horizontal edge of a concrete slab, the longitudinal elements being intended to move away from each other by a distance corresponding to the theoretical shrinkage after drying concrete slabs, and each longitudinal element comprises an external sinusoidal profile intended to be in contact with a concrete slab, and an internal sinusoidal profile in contact with the internal sinusoidal profile of the other sinusoidal element.

In this way, taking into account the fact that the separation between two adjacent slabs is made with a sinusoidal profile, the wheel of a vehicle does not tend to fall between the two longitudinal elements of the joint. Said wheel therefore no longer hits the longitudinal elements of the joint when passing over the joint, but is in practice supported by one or other of the longitudinal elements of the adjacent slabs. This characteristic makes it possible to limit shocks and, ultimately, wear of the concrete slabs near the expansion joints.

That being said, automatically guided vehicles have increasingly smaller wheels, and in particular smaller than those of forklift vehicles, such as forklifts, vehicles known as “tritracks” or other well-known pallet trucks, so that the requirement becomes stronger.

It follows that the spaces left between the slabs after removal of the concrete must therefore be as small as possible, and in particular between 4 and 10 mm.

He is also known EP3483339 , FR2902118 And US2014/366472 which do not give complete satisfaction.

Presentation of the invention

One of the aims of the invention is therefore to remedy these drawbacks by proposing an expansion joint between two adjacent concrete slabs capable of providing a rolling surface without impact and jerk to a vehicle, in particular a vehicle with automatic guidance, without having to try to limit the value of concrete shrinkage after drying.

For this purpose, and to resolve the aforementioned problems, an expansion joint has been developed for a formwork system for concrete slabs on which at least one automatically guided vehicle is intended to circulate.

In a known manner, the expansion joint is in the form of two longitudinal elements each intended to form an integral part with an upper and horizontal edge of a concrete slab.

The longitudinal elements are intended to move away from each other by a distance corresponding to the theoretical shrinkage after drying of the concrete slabs, and each longitudinal element comprises an external sinusoidal profile intended to be in contact with a concrete slab.

According to the invention, each longitudinal element comprises an internal sawtooth profile so as to engage crests of the internal profile of one longitudinal element with hollows of the internal profile of the other longitudinal element, each crest and hollow being open to 'an angle less than or equal to 34.70°, with a radius of curvature at the apex less than 2 mm.

In this way, the longitudinal elements of the expansion joint according to the invention are designed so as to leave a gap between them which is reduced, even after shrinkage of the concrete by a maximum shrinkage value of 25 mm.

In practice, the gap left between the longitudinal elements is such that wheels of at least 15.6 mm width, with a contact surface on the ground of at least less than 1 mm, can circulate perpendicular to the joint with continuous support, so that circulation takes place without impact.

In other words, it is important to note that this means that the expansion joint according to the invention, after retraction of 25 mm, does not leave a gap greater than 1 mm for a wheel of 15.6 mm width, circulating on the joint, perpendicular to the longitudinal elements.

Of course, circulation is also without impact if the width of the wheels is greater than 15.6 mm, if the contact surface has a width greater than 1 mm, and if the shrinkage due to drying of the concrete is less than 25 mm.

Preferably, the amplitude of the internal sawtooth profile is greater than 25 mm, so as not to leave a gap between the crests of the internal sawtooth profiles after retraction of the concrete.

In practice, the circulation on the joint according to the invention takes place without impact in a direction perpendicular to the longitudinal elements of the joint, but also in all directions, except in those which are parallel or perpendicular to a slope of a tooth of the profiles sawtooth, but this on the assumption of circulation with a wheel. The minimum necessary being three wheels, circulation in all directions is therefore possible subject to dimensioning and respecting a horizontal and vertical spacing and positioning of the wheels sufficient so that three wheels are always supported on the current part of the paving and not on the joint.

From the above, the amplitude of the internal sawtooth profile is greater than or equal to 40 mm in order to further reduce the gap between the internal sawtooth profiles after retraction of the concrete and therefore to further reduce the risk that the vehicle wheel is not supported when passing over the joint. In practice, the amplitude value of 40 mm allows the crests to penetrate into the hollows of the complementary internal profiles with a value of 15 mm for a shrinkage of 25 mm after retraction of the concrete.

This characteristic makes it possible to reduce the gap between the slopes of the sawtooth of the sawtooth profiles to help reduce the risk of impacts when the wheels travel in a direction parallel or perpendicular to a slope of a tooth of the sawtooth profiles.

The internal sinusoidal profiles can have different shapes without departing from the scope of the invention. For example, the internal sinusoidal profiles can have vertices at a screw angle to have a sinusoidal sawtooth profile, or vertices with a radius of curvature to have a so-called classic sinusoidal profile.

Preferably, the radius of curvature at the top of the sawtooth profiles is less than 1 mm, preferably less than 0.5 mm so as not to clip the profiles and enlarge the gap between the longitudinal elements.

Brief description of the drawings

• [ Fig. 1 ] is a schematic representation, in perspective, of an exemplary embodiment of the expansion joint of the invention, equipped with vertical load transfer means, and fixed to a vertical separation plate of a formwork system.
• [ Fig. 2 ] illustrates, seen from above, the internal sawtooth profiles of the longitudinal elements of an expansion joint according to the invention, spaced 25 mm apart, the crests and hollows being open at an angle of 34.70°, with a radius of curvature at the top less than 2 mm.

Detailed description of the invention

With reference to figures 1 And 2 , the invention relates to an expansion joint (1) used to create an air space between two adjacent concrete slabs, necessary for absorbing variations in volume of the slabs, for example under the action of retraction of the slabs during drying.

The expansion joint (1) according to the invention is adaptable to any type of formwork system implementing at least one vertical separation plate (2) of two adjacent concrete slabs, such as that described for example in the international application for patent published under number WO 2013/072619 .

In practice, the upper part of the vertical separation plate (2) of the formwork system is made integral with the expansion joint (1), and more precisely with two longitudinal elements (3, 4) having “sinusoidal” profiles or more generally in waves, that is to say with alternating troughs and crests.

For example, the separation plate (2) comprises in its upper part a horizontal support plane on which one of the sinusoidal elements (4) is fixedly secured, by any appropriate means, and preferably by welding. In other words, a sinusoidal element (4) is arranged over the entire length of the plate (2) so as to form a horizontal support plane, and is coupled with the second sinusoidal element (3).

The longitudinal elements (3, 4) are joined together so as to engage crests of one element with valleys of the other element, and each sinusoidal element is intended to form an integral part with an upper edge and horizontal of a concrete slab.

After pouring and drying the concrete slabs, the longitudinal elements (3, 4) are intended to move away from each other by a distance corresponding to the theoretical shrinkage (r).

As illustrated in the figures, each sinusoidal element (3, 4) comprises a width determined so as to define an external sinusoidal profile intended to be in contact with a concrete slab, and an internal sawtooth profile, see figure 2 , in contact with the complementary internal profile of the other sinusoidal element. Each sinusoidal element comprises for example rods (not shown) projecting from a lower face, obliquely, and in the opposite direction to the other sinusoidal element to constitute concrete grip means, thus arranged to ensure balancing.

According to the invention, the expansion joint (1) makes it possible to ensure continuity between the concrete slabs so that the circulation of a vehicle, in particular of the automated guided type known by the acronym AGV from the English "Automatic guided vehicle", with wheels at least 15.6 mm wide, having a contact surface at least 1 mm wide (reference (5a)), can be done without impact, even with a maximum removal of 25 mm after drying of the concrete slabs.

To this end, at the figure 2 , the crests and hollows of the internal sawtooth profiles are open by an angle α equal to 34.70°, with a radius of curvature at the top less than 2 mm. There figure 1 is schematic, the radius of curvature according to the invention is not respected.

Of course, if the shrinkage is lower, the admissible wheel widths, to circulate without impact, for a contact surface of 1 mm wide are summarized in the table below. [Table 1] Shrinkage (in mm) 25 20 15 10 5 Permissible wheel width (in mm) without impact for a contact surface of 1 mm wide 15.6 12.5 9.4 6.25 3.13

According to this table, the expansion joint according to the invention, after retraction of the concrete by 10 mm for example, does not leave a gap greater than 1 mm for a wheel of 6.5 mm width, circulating on the joint, transversely to the longitudinal elements (3, 4).

According to different embodiments, the amplitude (A) of the internal sawtooth profile is greater than 25 mm, see figure 1 , and preferably greater than or equal to 40 mm, see Figure 2 .

The radius of curvature at the top of the sawtooth profiles is less than 1 mm, preferably less than 0.5 mm, see figure 2 .

Other possibilities offered by the joint according to the invention have been summarized in the table below: [Table 2] Concrete Shrinkage (mm) Continuous support in circulation perpendicular to the joint elements ensured up to a wheel width equal to (mm) for ground contact of 1 mm wide Continuous support in circulation parallel to a sawtooth slope ensured up to a wheel width equal to (mm) for ground contact 1 mm wide 5 3.13 3.31 10 6.25 6.61 15 9.38 9.92 20 12.5 13.22 25 15.6 16.53

In the most critical case where the wheels travel in a direction perpendicular to a slope of a sawtooth, the joint according to the invention makes it possible to have a gap of 6 mm for a wheel having a width less than 52 mm, when the concrete shrinks by 20 mm. And a gap of 4 mm for a wheel with a width less than 50 mm, when the concrete shrinks by 15 mm.

If the wheels are wider, they move without impact. It is further recalled that these results are calculated for a critical hypothesis of circulation with one wheel, whereas in reality automatically guided vehicles include at least three wheels, or even four or more.

The central and lateral longitudinal elements (3, 4) can be in one piece. Preferably they are multi-layered, and include arrangements (6) opening out at an upper face allowing at least one surface layer to be removed from each of the longitudinal elements (3, 4) with a view to their replacement.

The arrangements are for example in the form of orifices passing vertically through at least one surface layer of each of the longitudinal elements (3, 4), and of inserts, not shown, positioned and fixed to a lower or intermediate layer. The inserts are tapped and capable of receiving complementary clamping members for the removable fixing of the surface layer of each of the longitudinal elements (3, 4).

The surface layer can be made of steel or of a resin or of a composite material made from polymeric materials so that it can be sanded in order to rectify a flatness defect.

Below the sandable surface layer, it is possible to have one or more layers, for example metallic.

In the embodiment illustrated in figure 1 , the longitudinal elements (3, 4) of the joint comprise a stack of at least three layers (3a, 3b, 3c, 4a, 4b, 4c) to ensure the transfer of vertical load between the two slabs.

For example, the first longitudinal element (3) comprises three layers, with an intermediate layer (3b) called plane support connection of a width greater than that of the other two layers (3a, 3c) so as to form a longitudinal tongue projecting laterally, that is to say along a plane parallel to that of an upper face of the first longitudinal element (3).

And, the second longitudinal element (4) also comprises a stack of three layers, with an intermediate layer (4b) called plane support connection of a width less than that of the other two layers (4a, 4c) so as to form a longitudinal lateral groove, that is to say extending parallel to a plane defined by an upper face of the second longitudinal element (4), receiving in insertion the tongue of the first longitudinal element (3) to form the plane support connection.

It appears from the above that the invention provides an expansion joint (1) between two adjacent concrete slabs capable of providing a rolling surface without impact and jerk to the wheels of a vehicle, in particular a vehicle with automatic guidance.

Claims (4)

1. Expansion joint (1) for a formwork system of concrete slabs on which at least one automated guided vehicle is intended to travel, said expansion joint (1) consists of two longitudinal elements (3, 4) each intended to form an integral part with a top and horizontal edge of a concrete slab, the longitudinal elements (3, 4) being intended to move apart from each other by a distance corresponding to the theoretical shrinkage after drying of the concrete slabs, and each longitudinal element includes an external sinusoidal profile intended to be in contact with a concrete slab, characterized in that each longitudinal element includes an internal sawtooth profile so as to engage the crests of the internal profile of one longitudinal element with the troughs of the internal profile of the other longitudinal element, each crest and trough being open at an angle α of less than or equal to 34.70°, with a curvature radius at the top of less than 2 mm.
2. Expansion joint (1) according to claim 1, characterized in that the amplitude of the internal sawtooth profile is greater than 25 mm.
3. Expansion joint (1) according to claim 2, characterized in that the amplitude of the internal sawtooth profile is greater than or equal to 40 mm.
4. Expansion joint (1) according to claim 1, characterized in that the curvature radius at the top of the sawtooth profiles is less than 1 mm, preferably less than 0.5 mm.

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