EP0269497B1 - Reinforcement of supporting structure elements by inserting highly resistant plates - Google Patents

Description

• altération du bois par suite des intempéries ou de l'attaque par des larves d'insectes, des algues, des champignons, des micro-organismes (pourritures). Ces altérations touchent fréquemment par exemple les extrémités de poutres encastrées, à cause notamment de l'humidité qui peut régner autour de la poutre au niveau de l'encastrement par absence de ventilation;
• apparition de charges anormales pouvant entraîner la rupture de fibres: surcharge des planchers, modification de la géométrie des assemblages par suite de tassements des fondations, etc... .

The present invention relates to a method of reinforcing structural elements or building structures, in particular of wood, such as beams. We can reinforce wooden beams and structural elements for different reasons:

• weathering of the wood due to bad weather or attack by insect larvae, algae, fungi, micro-organisms (rot). These alterations frequently affect for example the ends of embedded beams, in particular because of the humidity which can reign around the beam at the level of the embedding by absence of ventilation;
• appearance of abnormal loads which can lead to the breaking of fibers: overloading of floors, modification of the geometry of assemblies due to settlement of foundations, etc ....

French Patent No. 2,170,498 to BOUWECONOMISCH EN TECHNOLOGHISCH ADVIESBUREAU describes a method of reinforcing wooden beams in the region of their support by reinforcing rods driven into holes drilled in wood and secured to wood by a hardenable paste resin-based. This process has several drawbacks: on the one hand, it is difficult to size the reinforcing rods because we do not always know the direction and intensity of the forces to be taken up in a degraded beam, on the other hand, this process only concerns beam reinforcements at their supports. Finally, reinforcing rods work mainly in traction, and it is the degraded beam which must provide the additional mechanical resistance necessary for the resumption of bending moments and compression forces. English Patent No. 2,150,969 to DINARDO & PARTNERS describes a method for reinforcing wooden beams by digging longitudinal grooves, inserting reinforcing plates in these grooves, and fixing said plates by bolts crossing the beam perpendicular to the plates and by filling the groove with curable resin. This process requires drilling the beam perpendicular to the groove to allow the passage of the bolt rods, which is a time consuming operation and which is only possible if there is sufficient space on each side of the beam, at right of the party to strengthen. Furthermore, tightening numerous bolts can be a time consuming operation. In addition, a heavily damaged beam does not always allow the bolts to be tightened.

An object of the present invention is to provide a method of reinforcing structural elements or building structures, in particular of wood, such as beams, without adding structural reinforcing parts to the exterior of said elements, and while preserving the original shape and size of these elements, as well as their appearance in most cases. Another object of the present invention is that said reinforcement is easily calculable, and that it is possible by implementing it to reinforce a wooden element both at the level of its supports and in other places, even over its entire length.

• creuser des cavités sensiblement planes dans les zones à renforcer de l'élément;
• insérer dans lesdites cavités des plaques de renforcement;
• remplir lesdites cavités d'un produit durcissable de remplissage à base de résine de façon à solidariser lesdites plaques à l'élément, sans adjonction d'autres éléments métalliques,

lesdites plaques de renforcement étant suffisamment résistantes et dimensionnées pour pourvoir restituer ou conférer à l'élément l'inertie souhaitée après solidarisation.According to the present invention, a method of reinforcing structural elements or building structures, in particular of wood, such as beams, comprises the following steps:

• dig substantially flat cavities in the areas to be reinforced of the element;
• inserting into said cavities reinforcing plates;
• filling said cavities with a curable resin-based filling product so as to secure said plates to the element, without the addition of other metallic elements,

said reinforcing plates being sufficiently strong and dimensioned to provide restore or give the element the desired inertia after joining.

The cavities are for example rebates or grooves dug in the wood.

The resin product can be an epoxy resin, a grout or a resin mortar, which adheres strongly to both the wood and the material of the reinforcing plates, which can be metal, wood, plastic, or any other sufficiently rigid and resistant material. The plates can also be of expanded metal.

According to an advantageous embodiment of the invention, the connection of the reinforcement plates with the grout or the resin mortar can be improved, either by perforating or perforating the reinforcement plates, or by equipping them with projections or reliefs such than ankles or nipples.

Still according to the invention, if the element comprises degraded zones, the degraded zones can be regenerated beforehand by impregnation by capillary action or injection of product based on fluid resins, possibly solvent-based, or recharged with a semi-flexible resin mortar, the elasticity will have been adjusted according to that of the wood.

Other characteristics and advantages of the present invention will appear better on reading the following description given by way of nonlimiting examples of the possible embodiments of the invention, with reference to the attached drawings and which will make it clear how the invention can be realized.

In the drawings:
FIGS. 1a to 1d are cross-sections in principle illustrating different stages of the strengthening of an element according to an embodiment of the method of the invention;
Figure 2 is a cross section in principle of a reinforced element according to another embodiment of the method of the invention;
Figure 3 is a longitudinal section in principle of a rotten butt end of a reinforced recessed beam according to the method of the invention;
FIG. 4a is a longitudinal section in principle of another end of a reinforced embedded beam according to the method of the invention;
Figure 4b is a cross section in principle of the beam end of Figure 4a, along line XX;
Figure 5 is a partial side view of an overloaded beam being reinforced according to the method of the invention;
FIG. 6 is a perspective view of a wooden beam to which its initial resistance has been restored over its entire length thanks to the process.

In Figure 1a, there is shown a beam 1 of rectangular section in cross section. A first zone 2 is healthy, while a second zone 3 is degraded by rotting. The broken lines show the initial beam shape. In FIG. 1b, cavities in the form of grooves 4 have been dug in the beam. The grooves cross the degraded zone 3 and enter the healthy zone 2. FIG. 1c illustrates a later phase of the beam reinforcement: the degraded zone 3 has been impregnated with resin, and longitudinal reinforcement plates 5 have been placed in said grooves 4. The reinforcement plates 5 are pierced with holes 6. In FIG. 1d, the reinforcement is finished: a resin grout 7 was injected into said grooves 4 around the plates 5, and the shape of the beam was reconstituted by an addition of material in 8, which can be a resin mortar. The holes 6 have dimensions such that they are filled with resin grout during injection, which improves the connection of the reinforcement plates with the rest of the beam 1.

Figure 2 is a cross section of a reinforced beam according to another variant of the method of the present invention. We recognize a beam 11, a healthy area 12, a degraded area 13 regenerated by impregnation of resin, a groove 14, which extends longitudinally, and a reinforcing plate 15 inserted in said groove. This time, the reinforcing plate 15 is provided with pins or dowels 16 for securing in order to improve the joining of said plate to the rest of the beam 11. Said dowels also make it possible to position the reinforcing plate 15 in the groove before injection and setting the resin grout.

In Figure 3, there is shown in longitudinal section a buttress of recessed beam reinforced according to the method of the present invention. A wooden beam 21 is embedded in a load-bearing wall 20. A first zone 22 of the beam is healthy and a second zone 23 located near the wall is degraded, for example by decay. Wood is missing at the end of the beam, at the level of the embedding. According to the method of the invention, a reinforcing plate 25 has been introduced into a longitudinal groove not shown, but similar to those 4, 14 described previously with reference to FIGS. 1 and 2. The reinforcing plate extends in a part from the healthy zone 22, passes through the degraded zone 23 and protrudes from this second zone towards the outside, to the end of the beam as it originally appeared. A resin grout is then injected which fills all the voids, around the reinforcement plates in the groove, said plates thus being embedded in the resin grout, and between what remains of the beam and the wall 20, in the housing embedding 28. In addition, the excess resin permeates and strengthens the degraded or decomposed areas 23 of the wood, and gives them a resistance greater than their initial resistance. As before, the plate 25 can be provided with fixing holes or dowels 26 for fixing and positioning.

Figures 4a and 4b illustrate a variant of the method described with reference to Figure 3. This time, the method of the invention is used to reconstruct a beam butt. The end of a wooden beam 31 supported by this end in a wall 30 is degraded and the support must be restored. Two longitudinal grooves 34 are hollowed out in the beam and reinforcing plates 35 pierced with holes 36 are introduced into the grooves. The reinforcement plates are here provided with bearing heels 40 at their lower part. The grooves start from a healthy zone 32 of the beam, crossing the degraded zone 33 and extend towards the support up to the end of the beam as it appeared before its degradation. As before, a resin grout is injected into the grooves 34. It fills these grooves, permeates the degraded area 33 and replaces the missing material 38, here wood, at the end of the beam. A seal bottom 39 can be provided to limit resin overflows.

The method of the invention can also be used to allow a beam to withstand forces for which it was not originally intended. This application of the process of the invention is illustrated in FIG. 5. Following an overload causing an excessive bending moment, a wooden beam 41 is cracked in the middle according to surfaces defined by oblique lines 42. According to l invention, after having taken up the deflection of the beam by means of props 43, one or more longitudinal grooves 44 are hollowed out in the lower part of the beam 44 in each of which a reinforcing plate 45 is pierced with holes 46. After having carried out injection drilling 47, 48 which intersects the rupture cracks 42 in the beam 41, a resin-based product is injected into these drilling. In this way, the resin product travels through the cracks and restores the monolithism of the beam. As before, the grooves are also filled with resin.

In the last example, illustrated in Figure 6, a wooden beam 51 8 meters long and 0.4 x 0.4 m2 in section, embedded at its ends to a depth of 0.40 m, was reinforced over its entire length by means of a metal plate 55 15 mm thick inserted in a groove 54 20 mm wide starting from the top of the beam and stopping 50 mm from the bottom of the beam. The plate 55 is pierced with securing holes 56. In this example, the beam has been restored to its initial strength after hardening of the resin injected into the groove 54 around the metal plate. It is easy to size the metal plate, because it was enough here to give it the same mechanical resistance as the wooden beam from the point of view of bending moments and sharp forces, the rest of the wooden beam being used here only for s opposing the buckling of the compressed part of the metal plate, above its neutral axis.

The method of the present invention is particularly applicable to the reinforcement of building structures, for example in the context of rehabilitation, conversion or restoration of building operations.

Claims (9)

1. Process for reinforcing a building structural element (1, 11, 21, 31, 41, 51), in particular a timber element with decayed areas (3, 13, 23, 33), comprising the following steps:

   - excavating cavities in the form of rabbets or grooves (4, 14, 24, 34, 44, 54) in the regions of the element to be reinforced;

   - inserting into said cavities reinforcing plates (5, 15, 25, 35, 45, 55) with holes (6, 26, 36, 46, 56);

   - simultaneously filling said cavities (4, 14, 24, 34, 44, 54) and said holes (6, 26, 36, 46, 56) with a resin-based hardenable filling product so as to lock said plates to the element without addition of other metal elements, said holes permitting improved locking of said plates to said product after hardening, said reinforcing plates being sufficiently strong and dimensioned to restore or impart the desired stability to said element after hardening.
2. Process for reinforcing an element according to Claim 1, characterized in that it also comprises the replacement of a missing portion (8, 18, 28, 38) of said element by a refilling material.
3. Process for reinforcing an element according to Claim 1 or Claim 2, characterized in that it also comprises the impregnation of decayed regions (3, 13, 23, 33) of said element with a fluid resin-based product.
4. Process for reinforcing an element according to any one of the preceding claims, characterized in that said reinforcing plates are made of steel, metal, wood or rigid plastic.
5. Process for reinforcing an element according to any one of claims 1 to 3, characterized in that said reinforcing plates are plates of expanded metal.
6. Process for reinforcing an element according to any one of the preceding claims, characterized in that said reinforcing plates are provided with dowels (16) for positioning or locking in place.
7. Process for reinforcing an element according to any one of the preceding claims, characterized in that said reinforcing plates are provided with supporting heels (40).
8. Process for reinforcing an element according to any one of the preceding claims, characterized in that said resin-based product is a resin grouting, in particular epoxy resin.
9. Process for reinforcing an element according to any one of the preceding claims, characterized in that said filling product is a resin mortar.

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