WO2006102733A1

WO2006102733A1 - Column-based building and round timber anchorage

Info

Publication number: WO2006102733A1
Application number: PCT/CA2006/000357
Authority: WO
Inventors: Libère Nitunga
Original assignee: Kebeya, Evariste; NIYONIZIGIYE, Déogratias
Priority date: 2005-03-31
Filing date: 2006-03-16
Publication date: 2006-10-05

Abstract

The invention relates to column-based buildings and to round timber anchorages exhibiting quakeproof properties. Said invention provides for several possible wall embodiments: timber, panels, thin earthen partitions pressed on bamboo structures, conventional masonry etc.

Description

BUILDING WITH COLUMNS AND ROUND WOOD CHAININGS

The present invention relates to the production of structures bearing structure in the form of columns and chaining.

For this type of construction, the conventional technique generally uses columns and links in reinforced concrete or steel.

On the other hand, the present invention consists in producing these columns and links in solid wood, by means of a cluster of innovations that each bring its stone to the building. Indeed, there are a multitude of problems that must be solved one by one, until a product that is interesting from a technical, financial and environmental point of view. These innovations are mainly:

- The multiplication of the points of attachment of the beams to the columns;

- The realization of an axial assembly of a beam with two plates by friction;

- Localized drying of the areas of assemblages of columns and chaining;

- The realization of thin walls in compressed clay on bamboo fences; - The improvement of the adhesion of the cement on a wall of raw earth;

- Axial elongation of 2 massive woods.

The multiplication of the points of attachment of the beams to the columns

For a horizontal beam connected to a column can effectively play the role of chaining, it must have sufficient resistance to traction efforts that tend to tear the column.

The tensile strength of commonly used wood assemblies is relatively low. To remedy this situation, the present invention has as its main objects the multiplication at will of the number of beam-column connections on the one hand, and the improvement of their unit resistance to traction on the other hand. The invention uses a multitude of points of attachment of the beams to the columns.

The first point is the very end of the beam, and then come from other points situated higher and lower on the column, and others situated further to the left and more to the right on the beams directly adjacent. i) A point of direct attachment of the beam on the column at their point of intersection, by a fitting whose assembly at the end of the beam is by friction.

In the conventional assembly of a fitting with the end of a beam per bolt, when the end distance is too small, there is a risk of rupture by tearing or splitting.

In order to deal with it, it is sought to place the bolt as far as possible from the end of the beam, so that the area between the bolt and the end is as large as possible.

In the context of the invention, it is mainly the friction forces that occur between the surface of two metal plates placed on either side of the beam and the latter. These friction forces occur due to the pressure exerted by the clamping bolts. Thus, the contact surface between the plates and the beam, sandwiched by said plates, plays a large role here. The tear resistance of the small piece of wood between the bolt and the end of the beam is also greatly enhanced.

Such an assembly is also used to connect the floor joists to the chaining, which contributes to considerably increase the rigidity of the construction. ii) Points of direct attachment of the beam on the column, by one or more pieces of vertical triangulation. ifi) Indirect points of attachment of the beam on the column, by one or more pieces of horizontal triangulation. The connection thus made concerns not only the two beams perpendicular to the beam concerned, but also the opposite beam.

In the case of multi-level constructions, the vertical loads transmitted to the ground by a column are important and generally require a very rigid connection between said column and the foundation, especially via the lower chaining.

In the context of the invention, the distribution of vertical loads on the foundation is made by several pieces of vertical triangulation. These pieces can be doubled or even tripled incase of need.

All triangulation parts mentioned above are in position to play, in addition, an important role in the bracing of the structure both in the horizontal direction in the vertical direction. These parts also play the role of struts, and thus greatly increase the capacity of the beams to support your vertical loads from the upper floors.

Thus one arrives at a construction having an extremely dense bracing made relatively inexpensively insofar as its cost is imputed to its primary function which is to give the character of chaining to the beams. Such bracing gives the building an important earthquake resistance capability.

The assembly of all these triangulation parts with the beams and with the columns is done by threaded rods, placed at a good distance from the ends to reduce as much as possible the risk of tearing in case of stress. Among these stems, i! some are stressed in tension and others are stressed in shear.

The rods stressed in tension do not require special strengthening measures except the use of large washers for tightening the nuts. As for the rods that are stressed in shear (single or double), reinforcement measures are necessary to prevent the triangulation piece from sliding along the beam in tension, it is for example to put a wedge in the angle formed by the triangulation piece and the beam.

In one embodiment of the invention, the wood used as columns, chaining, triangulation pieces and floor joists is a round wood, which has a lot of advantages over squared wood (wood that has gone through a sawing process ):

- It is a raw wood, which did not consume energy for its transformation.

- Almost 100% of the ligneous material is valorized. The virtual absence of transformation makes it possible to avoid losses of materials (slabs, sawdust, dust, etc.).

- For the same mechanical performance, a lower volume of roundwood than squared wood is needed, since the cutting of the wood fibers during sawing considerably affects its resistance to bending. See also the role of the sapwood in the mechanical stability of the standing tree. - Preservative treatment is much more effective on roundwood than squared timber of the same section: see presence of the sapwood.

- The age of exploitation of wood is much less reduced for roundwood than for squared timber. Local drying of the assembly areas of columns and chaining In order for the pressure exerted between the two metal plates to be constant, it is necessary that the thickness of the beam clamped between said lacquers is constant, too, throughout the lifetime of the 'work. So the wood must have reached a relative humidity of 19% or less at the time of assembly, so that its dimensions do not change thereafter.

This requirement can be disadvantageous in the case of beams of high thickness, because it takes a lot of time with conventional drying means.

That is why in the context of the invention a localized drying technique has been developed, which consists in producing a heating plate having the shape of the fittings connected by bolts, exactly as will be the fitting of the iron fittings. assemblies. It should be noted that it is a matter of perfecting the drying and not of a very numid wood drying technique.

Among the advantages of this technique we can note these: - The drying efforts are concentrated on the area whose subsequent removal of the wood would have the greatest negative impact on the stability of the construction.

- The clamping force exerted by the bolts prevents cracking due to possible rapid drying, which allows the use of a relatively high temperature compared to conventional methods. - The clamping bolts connected to the heating plate pass into the wood mass and thus contribute to the achievement of a fast and homogeneous drying.

- The strong pressure exerted on the end of the beam by the clamping bolts leads to a certain compression of the cells of the wood. Performing such an operation well in advance during the drying process makes it possible to arrive at an invariable thickness at the time of implementation of the chaining.

One can ask the question of what happens to the value of the clamping force in case of re - humidification of the beam.

For the thicknesses of the beams referred to in the context of the invention - of the order of 8 cm between the plates of the assembly fitting, and the clamping forces of 3 bolts of the M12 type (class 8.8), It has been found that exposure to a wetter atmosphere does not lead to significant moisture recovery at the pressurized zone.

Construction of a thin wall of compressed earth on a bamboo screen The wooden structure object of the present invention can support conventional masonry as filling walls. However, this requires the use of fairly large section wood. When the wood used is of common dimensions, it is necessary to lighten as much as possible the weight of the walls. This can be done in particular by the use, as filler walls, of solid wood panels or plywood, but they are relatively expensive.

A technically feasible and economically affordable solution developed in the context of the present invention is to use thin walls of compressed earth on bamboo screens. One or more bamboo slats are sandwiched between wooden slats, which are themselves firmly attached to the elements of the structure: chaining, columns, triangulation pieces.

Fixed formwork is then installed on one side of the wall. A well-kneaded soil is applied against the inner face of the formwork until it reaches a thickness slightly greater than that predicted for the wall. A mobile formwork is then placed on the other side of the wall, then pressed firmly against the earth to compress it, thanks to multiple bolts that cross the two forms and the wall under construction. It can thus achieve walls of 10 square meters with a thickness of about 7 cm.

In place of the raw earth, a cement concrete can also be used, but in this case there is no compression to do. The technique of building compressed or tamped earth walls is well known; it is mainly rammed earih. However, here compression takes place in the vertical direction between two fixed forms, and does not allow the realization of thin walls, which is the objective pursued within the scope of the invention. It is also impossible to arm this earthen concrete with any grid as is the case within the scope of the invention. Indeed, the grooming operations would be strongly handicapped by the presence of said frame.

Earthen constructions on a wooden fence, bamboo or reed are also known as cob. But in the case of mud no compression is envisaged, resulting in thick, low-density walls. Other types of constructions are close to the invention:

The half-timbering

This technique is characterized by wooden structure elements usually assembled by tenons and mortises. The free spaces between the wooden elements are filled by different types of materials such as: cob, bricks; rubble, wood ...

Poles - beams

The system consists of creating a kind of large open structure formed, as the name suggests, of poles and beams supporting the floors, partitions and roof. It should be noted that we bet posts - beams and not columns - chaining! Indeed, as said above, chaining involves a tensile force resistance capacity.

Improved adhesion of cement on a mud wall

The thin earthen wall compressed on a bamboo fence must be protected from the weather. The most common protection of the walls is to coat them with a layer of cement.

However, when applying a coating of cement on a mud wall exposed to bad weather, it comes off more or less quickly, because the cement does not adhere very well to the ground. In order to allow a better adhesion of the plaster, it is usually a staking of the surface or is embedded in stone chips.

The solution found in the context of the invention is to intercalate between the two, a layer of cement stabilized clay coating, which has a significant adhesion to both the earth and cement. Axial elongation of 2 massive woods

The solid wood structure object of the invention requires woods of great straightness. For chaining, there are usually no problems in finding them since they are lengths of the order of 3 - 4 m.

As for the columns, lengths of the order of 10 m are required for a two-level construction. It may then be necessary to assemble two posts in the axial direction to arrive at the desired length.

In the context of the invention, a technique for assembling two solid wood end-to-end has been developed. It involves axially drilling the two ends to be assembled with a hollow cylindrical drill (bell saw) of appropriate dimensions, and then to introduce a metal pipe which serves as a connection between the two pieces of wood; the diameters of the hole saw and the pipe being chosen so that the introduction is forced inside the pipe but free outside. In this way, the wood involved in the assembly will be solicited only compression.

Figure 1 shows a perspective of two pieces of solid wood to assemble (1) and (2), and the connecting pipe (3); the drilling with the hole saw being finished. Figure 2 shows in section the ends of pieces of wood already assembled end to end. Figure 3 shows a possibility of improving the strength of the assembly by a system of non-return studs (4) placed inside the assembly pipe. FIG. 4 represents the assembly mode chaining-lock closest to the invention. It clearly appears that the distance between the bolts of assemblies and the end of the beam for the pull-out resistance in case of axial force is counted.

FIG. 5 represents a method of assembly chaining - fitting according to the invention. Here the distance between the assembly bolts and the end of the chaining is not very important.

Figure 6 shows the end of a chain with two irons L, which highlights that it is the friction forces of the two fittings on the end of the beam that are important.

Figure 7 shows a direct link chaining - column at their point of intersection. FIG. 8 represents the schematic diagram of the direct link chaining - column by pieces of vertical triangulation. Column (5), chaining (6), two pieces of vertical triangulation (7), assembly bolts of said triangulation pieces to the beam and to the column (8), and an anti-slip wedge ( 9). FIG. 9 represents the schematic diagram of the indirect chaining-column link, by two pieces of horizontal triangulation (10) connecting the chaining (6) to the two links adjacent to the column (11). These last two diagrams highlight the contribution of the opposite beam (12), in the recovery of the tensile stresses exerted on the beam (6). Figure 10 shows the positive consequences of the direct links chaining - columns by vertical triangulation parts on the vertical bracing of the construction, the resistance of the chaining to the vertical loads, and the distribution of these on the foundation.

Figure 11 shows the positive consequences of indirect chaining - column links on the horizontal bracing of the construction.

The industrial applicability of the claimed invention is amplified by two previous inventions of the same author, which allow the impregnation of round wood throughout its mass (heart and sapwood): see file PCT / IB 01/01171 and PCT / CA2005 / 001,356.

The first method fully deploys its performance on eucalyptus wood which is widely used in tropical countries, and the second is better indicated for coniferous species, more used in temperate countries.

With autoclave vacuum and pressure treatment, which is the most commonly used conventional technique, only the 1 to 3 cm outer layer of sapwood is impregnated. Thus the heartwood, which represents more or less 70% of the volume of roundwood is not protected. The use of a wood thus treated in the constructions object of the present invention would greatly limit the applications.

Claims

BUILDING WITH COLUMNS AND ROUND WOOD CHAININGS

1. A system for constructing buildings with a load-bearing structure of the column-chained type, characterized in that the structure is made of wood, and the beam-column assembly is designed to withstand the tensile stresses thanks to the following connections acting together or separately: (a) a direct beam - column connection at their point of intersection; (b) several direct column - beam connections by vertical triangulation parts; c) several indirect links by pieces of horizontal triangulation connecting the beam concerned to two other beams directly adjacent.

2. A technique for producing a beam-column connection in a wooden construction, characterized by a resistance to tensile stresses due to the friction forces that occur between the beam and two metal plates placed on either side of the beam. said beam, plates interconnected by several bolts.

3. A building system according to claim 1, wherein a vertical load distribution is performed on a continuous foundation by multiplying as much as

, if necessary, the vertical triangulation parts ensuring the direct connection between the columns and the different sections of the lower chaining.

,

4. A construction technique according to claim 2, used in the fixing of wooden floor joists.

5. A technique of construction of compressed earth walls, characterized in that the compression of said earth takes place horizontally using formwork placed on either side of the wall and interconnected by bolts.

6. A technique of building earthen walls according to claim 5, characterized in that the compression is er u on one or more screens in bamboo slats.

7. A technique for improving the adhesion of cement on a wall of raw earth, which consists of inserting between the two, one or more layers of stabilized earth plaster.

8. A technique of joining two solid woods end to end, which consists in axially piercing the two ends to be assembled with a hollow cylindrical drill (bell saw) of appropriate dimensions, and then introducing a metal pipe which serves as a connection between the two pieces of wood; the diameters of the hole saw and the pipe being chosen so that the introduction is forced inside the pipe but free outside.