EP2154316A1

EP2154316A1 - Method for in situ restoration of wood beams

Info

Publication number: EP2154316A1
Application number: EP07788580A
Authority: EP
Inventors: Mikel Landa Esparza
Original assignee: Individual
Current assignee: Individual
Priority date: 2007-06-06
Filing date: 2007-06-06
Publication date: 2010-02-17
Also published as: WO2008148897A1; EP2154316A4

Abstract

The method for in situ restoration of wood beams (1) of the invention comprises a phase of joining at least one part of the contact surface of the wood beam (1) with a wood reinforcing element (2) along the longitudinal direction of the wood beam.

Said joining can be carried out on all the contact surfaces of the beam (1) and the reinforcing element (2), enabling the reinforcing element (2) to work jointly with the wood beam (1).

Description

Object of the Invention

The object of the method for in situ restoration of wood beams of the invention is to reinforce wood beams without needing to remove said beams from their location.

Background of the Invention

Methods based on incorporating materials such as steel, concrete or prostheses of composite materials are currently used for the reinforcement of damaged wood structures.
The drawback of said methods, which use materials anchored to the beam at discrete points, is the fact that the loads are not uniformly distributed along the surface of the reinforcing materials. Therefore, the wood beam will be subjected to perhaps excessive stresses at the specific points of joining with the reinforcing materials, reducing the effectiveness of the reinforcement carried out.
Alternatively, and to overcome the mentioned problem, document ES-A-2154545 proposes giving the resistant capacity back to structural wood elements by means of using grafts. This technique consists of eliminating the damaged wood part, and providing wood in a good condition, joining it to the wood to be repaired by means of bonding.
Said technique is limited to the recovery or repair of a wood element, such that 100% of its original resistant capacity is recovered. However, this is not enough in some cases, since in certain conditions it is necessary to increase the load capacity of the beam thus restored.

Description of the Invention

The invention relates to a method for in situ reinforcement of wood beams. Said method is carried out without it being necessary to remove the beam to be restored from the present location. The action will be carried out in the site in which the beam is located.
According to the invention, the method comprises a phase of joining the largest contact surface of the wood beam with a wood reinforcing element along the longitudinal direction of the wood beam.
The reinforcing element does not have to cover the entire beam, nor is it necessary to carry out any intervention in the supports thereof. This is due to the profile of stresses of the beam, which stresses are greater around the mid-area of the beam, decreasing with the movement away from the mid-area. Therefore, the load in the supports of the beam is minimal, so it is not necessary, in most cases, to carry out any reinforcement in said area.
The reinforcing element made of wood can be joined to the beam either in its upper surface or in its lower surface, although the optimal reinforcement of the structure is carried out when it is performed in the lower surface of the beam, since it is in the lower fibers in which tensile stresses, more critical than the compression stresses experienced by the upper fibers of the beam, occur.
In the event of carrying out the reinforcement in the lower surface of the beam, the tensile strength characteristics of the beam will be improved and will tend to be those of the reinforcing element. Said reinforcing element will have known strength characteristics, therefore the strength of the reinforced beam will tend to be known and similar to the characteristics of said reinforcing element.
The invention contemplates, as an alternative to the fact of carrying out the reinforcement in the lower surface of the beam, carrying it out in the upper surface thereof. The greatest difference between both embodiments is that in this case the wood is placed in the compressed area and there is no action in the tensed area, which is the most critical one.
Therefore, this solution must only be used in the cases in which the wood of the beam to be restored does not have sufficient section, and therefore needs more wood, but the beam is in a good state of preservation. Confidence must therefore be placed in the quality of the wood of the beam in order to be able to apply this solution, given that the beam is not reinforced in its most critical surface, in which the tension load is greater and in which breakages or fractures could more likely occur.
In the event that the joining is carried out in the entire contact surface of the reinforcing element, such that the joining is homogeneous, it is achieved that the reinforcement acts jointly with the beam and that the loads are uniformly distributed in the entire joining or contact surface of the beam and the reinforcement, favoring that the reinforced beam acts as a beam with a larger edge and not as a beam and an outer reinforcement. This fact, the joint action of the beam and its reinforcement, is not possible in those cases in which the beam is joined with its reinforcement at discrete points, as could occur in the reinforcements carried out with steel sheets.
However, the reinforcing element being joined with the beam through wood connecting elements is contemplated as a possibility. It is thus possible to reinforce wood beams in which it is not possible to perform the reinforcement in its upper or lower surface. This situation could occur, for example, in a wood floor in which above the beams, and perpendicular thereto, joists or girders have been placed on which a wood floor will be arranged. The wood connecting elements are placed for the purpose of overcoming the presence of said joists, which elements will allow joining the beam at one end and the reinforcing element at their other end.
The method contemplates the possibility of the reinforcing element comprising the joining of at least one additional sheet to the one joined to the wood beam or to the connecting element. Said additional sheets will be added until the reinforcement has the suitable strength, i.e., the strength necessary to withstand the stresses to which the beam is subjected.
The adaptation of the reinforcing element to the shape of the beam generates strains at the ends of the reinforcing element, such that they tend to separate from the beam. If this occurs, the reinforcing elements and the beam would stop working jointly, and the reinforcement would have no effect. To prevent this, pin type joining elements made of either wood, fiber or metal can be placed, the exclusive function of which is to withstand the tension stresses perpendicular to the bonding plane which occur at the ends of the sheets and thus assure the correct operation of the assembly.

Description of the Drawings

To complement the description which is being made and for the purpose of aiding to better understand the features of the invention, a set of drawings is attached as an integral part of said description, in which the following has been depicted with an illustrative and non-limiting character:

Figure 1A shows a perspective view of the beam in which the reinforcement has been performed in its lower surface.
Figure 1 B shows a plan and elevational view of the beam in which the reinforcement has been performed in its lower surface.
Figure 2 shows a perspective view of the beam in which the reinforcement has been performed in its upper surface.
Figure 3 shows a perspective view of the beam in which the reinforcement has been carried out through connecting elements.

Preferred Embodiment of the Invention

Figure 1 shows an embodiment of the present invention. A beam (1) reinforced by means of reinforcing elements (2) in its lower surface (3) can be observed therein.
As can be observed in said Figure 1, the reinforcing element (2) is formed by a plurality of reinforcing sheets (4) along the length of the beam. The number of these sheets is enough to achieve the desired strength of the beam-reinforcement assembly.
The following case is proposed by way of a reinforcement embodiment.
A 12x10 cm beam (1) is considered, to which a 3 mm thick reinforcing sheet (4) is joined, determining a 15x10 cm beam (1), the values of the area, resisting moment and moment of inertia for the two configurations are:

12x10 cm beam 15x10 cm beam

Area 120 cm² 150 cm²

Resisting moment 240 cm³ 375 cm³

Moment of inertia 1440 cm⁴ 2812.5 cm⁴
The formulas for calculating the previous parameters are: $Area = a \times b$
$Resisting moment = b \times a^{2} / 6$
$Moment of inertia = b \times a^{3} / 12$

where a is the edge of the beam and b is the width thereof.
The previous example indicates that changing the edge from 12 to 15 cm increases the area by 25%, whereas the strength increases by 56.25% and the rigidity by 95.3%.
These values give an idea of the applicability of the solution, since it causes a considerable improvement in the conditions of the structure.
Said sheets (4) will have a decreasing surface, the surface being larger the closer the sheet is to the beam. The sheet (4) with a larger surface will thus be the one which is directly joined to the beam (1), improving the mechanical properties of the thus reinforced beam in the entire length of the sheet. The following sheet, which will be joined to the latter, will be smaller in size, given that the stresses of the outer segments require less reinforcement than those sections closer to the center of the beam (1). Sheets (4) will continue to be added until the last sheet, together with all the previous ones, provides the central section with the required strength.
In relation to the joining of the sheets (4) with one another, and the beam (1) with the reinforcing element (2), the joining will be carried out in the entire contact surface that the different elements have between one another. An equal distribution of the loads and the joint working of the beam together with the reinforcement will thus be achieved. The joining will be carried out by means of epoxy resin, for example. The characteristics of said reason are the fact of favoring a homogeneous joining and its adhesion and filling capacity.
The joining through epoxy resin may be complemented at the ends of the reinforcing elements (2) through the placement of pin type joining elements (5).
During the process of joining the wood reinforcing element (2) to the wood beam (1), the temperature of the contact surfaces is greater than 10ºC. Likewise, the humidity is less than 20%.
Figure 2 shows a second embodiment of the present invention in which the reinforcing element (2) has been joined in the upper surface (6) of the beam (1).
Figure 3 shows a third embodiment of the invention in which the reinforcing elements (2) are joined to the beam by means of connecting elements (7). Said connecting elements (7) are joined to the beam (1) at a first end and to the reinforcing element (2) at a second end.
It is thus possible to reinforce beams (1) having in the surface in which the reinforcement is to be performed elements making said reinforcement impossible. The connecting elements (7) allow raising the reinforcing element (2) to a level at which the elements making the reinforcement impossible no longer affect or interfere in the placement thereof. This situation occurs, for example, in joists on which the floor is placed which block the possibility of placing reinforcing elements (2) according to the first or second claim described.

Claims

Method for in situ restoration of wood beams (1),
characterized in that
it comprises a phase of joining the largest possible contact surface of the wood beam (1) with a wood reinforcing element (2) along the longitudinal direction of the wood beam.
Method according to claim 1, characterized in that the wood reinforcing element (2) is joined with the wood beam (1) in the upper surface (6) of the wood beam (1).
Method according to claim 1, characterized in that the wood reinforcing element (2) is joined with the beam (1) in the lower surface (3) of the wood beam (1).
Method according to any of claims 1-3, characterized in that the wood reinforcing element (2) is directly joined with the wood beam (1) in the entire contact surface of said wood reinforcing element (2).
Method according to any of claims 1-3, characterized in that the wood reinforcing element (2) is joined with the wood beam (1) through wood connecting elements (7).
Method according to any of claims 4-5, characterized in that the joining of the wood reinforcing element (2) comprises joining at least one additional reinforcing sheet (4) until achieving the suitable strength.
Method according to any of claims 1-6, characterized in that the joining of the contact surface of the wood elements (1, 2, 4) is carried out by means of epoxy resin.