Prefabricated structural bamboo system for slabs and roofs

Abstract

This invention refers to a structural system for floor and roof construction, based on a parallel arrangement of a set of composite pre-tensioned girders to provide support to a deck formed by layers of any given material. The composite girders are components formed by lengths of bamboo culms, steel components and fillings of mortar or other materials, arranged in such way that a maximum mechanical efficiency is obtained.

Claims

1. A slab system comprising: a deck comprising one or more layers which form a structural diaphragm and at least one of a top finishing layer and a bottom finishing layer; and a plurality of pre-tensioned composite girders installed in a parallel arrangement to support the deck, the pre-tensioned composite girders including a hollow bamboo culm having first and second opposite longitudinal ends defining a length from the first longitudinal end to the second longitudinal end with a central zone therebetween, and a profile having a length greater than the length of bamboo culm.

2. The slab system according to claim 1, where the profile is fastened to the bamboo culm at its longitudinal ends and at the central zone so that a distance between the length of bamboo culm and the profile is greatest at the central zone and the distance is linearly variable until the profile contacts the bamboo culm at the longitudinal ends.

3. The slab system according to claim 1, where the profile is fastened to the bamboo culm using a plurality of bolts and nuts that allows connection through a plurality of bores in the bamboo culm at connection points thereof that simultaneously pass through the profile and the bamboo culm in vertically aligned orientation.

4. The slab system according to claim 3, wherein at least one internode length of the bamboo culm is filled with a mortar at a connection point and prevents shear stress failures or crushing of one or more culm walls.

5. The slab system according to claim 3, wherein at least one bends of the profile at one or more connection points generates a compression condition in the bamboo culm when the profile is under stress, thereby reducing a shear stress load on the bamboo culm.

6. The slab system according to claim 3, wherein the bolts provide an axis about which a respective separator tube resides to separate the profile from the bamboo culm.

7. The slab system according to claim 1, where the pre-tensioned composite girder comprises a separator tube of greater diameter than a bolt located midway in a span of the central zone; the tube sheathing the bolt with the tube mechanically separating the bamboo culm from the profile and generating a compression stress between the bamboo culm and the profile.

8. The slab system according to claim 7, further comprising a second spacer tube of greater diameter than a second bolt located along the length of the pre-tensioned composite girder.

9. The slab system according to claim 1, wherein each composite pre-tensioned composite girder includes a profile including a steel plate having a curvature matching an outer curvature of a respective one of the bamboo culms, and a separator tube supporting the respective bamboo culm over the steel plate which distributes a compression stress over a larger area.

10. The slab system according to claim 9, wherein the steel plate having the curvature of the bamboo culm has a length no smaller than a third of an internode distance and is a support for a separator tube reducing a shear stress generated by the separator tube on a bottom wall of the bamboo culm.

11. The slab system according to claim 1, wherein the deck is comprised of at least one of concrete, steel, masonry, adobe, wood, composite materials, polyaluminum, bamboo, polystyrene, mineral wool, and mineral insulation material.

12. The slab system according to claim 1, wherein the pre-tensioned composite girder includes a gap between the bamboo culm and the profile along the central zone resulting in a condition of stress in the profile balanced by a compression produced in the length of bamboo culm.

13. The slab system according to claim 1, wherein the bamboo culm is arranged horizontally with a top of the bamboo culm allowing connection with the deck to which the pre-tensioned composite girders provide support.

14. The slab system according to claim 1, wherein the pre-tensioned composite girder generates a mechanical condition known as flexo-compression, which is produced by a spatial arrangement of a bamboo culm span.

15. The slab system according to claim 1, wherein the profile is fastened to the longitudinal ends of the bamboo culm producing a condition of stress in the profile and flexo-compression in the bamboo culm.

16. The slab system according to claim 1, wherein at least one pre-tensioned composite girder is configured with light weight, rigidity and high mechanical resistance to bear loads and deformations transmitted by the deck.

17. The slab system according to claim 1, wherein the pre-tensioned composite girder has a cambered geometrical configuration.

18. The slab system according to claim 1, wherein the profile is wrapped around the longitudinal ends of the bamboo culm, ending on a top side of the bamboo culm adjacent the deck.

Description

BRIEF DESCRIPTION OF THE FIGURES

(1) FIG. 1 shows the slab system working as a housing roofing or flooring where a parallel arrangement of pre-tensioned composite girders (1) is shown, consisting of a portion of bamboo culm and steel components over which a deck (2) is placed; said deck consists of one or several layers of material and is comprised of a structural diaphragm (3), a top finish (4) and a bottom finish (5).

(2) FIG. 2 shows a cross-section of the structural system for floors and roofs showing the arrangement of the pre-tensioned composite girders (1) that provide support for the deck (2), as well as all its components, such as the diaphragm (3), the top (4) and the bottom (5) layers, the bamboo culm, a metallic profile, a threaded bolt, a steel separator tube, nuts, washers, and plate, as indicated by numerals (6), (7), (8), (9), (10), (11) and (12) respectively.

(3) FIG. 3 shows a longitudinal view of the pre-tensioned composite girder that provides support to the slab, following the same numbering of components as in FIGS. 1 and 2, showing the cambered geometrical configuration resulting from the pre-tensioning process.

DETAILED DESCRIPTION OF THE INVENTION

(4) The present invention as shown in FIG. 1 refers to a slab system consisting of pre-tensioned composite girders installed in parallel arrangement (2), and supporting a deck (2). The deck consists of one or several layers forming a structural diaphragm (3), the top finish (4) and the bottom finish (5) of the system, which may consist of different materials (such as concrete, steel, masonry, wood, bamboo or a combination thereof). According to FIG. 2, each girder has a portion of bamboo culm (6) and a profile connecting to the culm (7), with bolts (8), nuts (10), and washers (11) for fastening the profile to the culm by inserting the bolts into previously perforated bores that vertically aligned pass through the profile and the culm; the nuts and washers are used to fasten them. The nuts are threaded into the bolts and rest on the profile via the washers, thus generating a condition of compression stress between the culm and the profile. The profile is arranged on the bottom part of the culm with symmetric geometry with respect to the center of the span and with a variable distance to the culm, but said distance is maximum at the central zone, linearly approaching the culm until making contact with it at the ends thereof. Moreover, the girder consists of a tube of greater diameter than the bolt located midway the span. As shown in the separator tube (9) of FIG. 2, the tube sheaths the bolt and is introduced to mechanically separate the bamboo culm from the profile. This tube rests on the bottom part of the culm, by means of a steel plate with the same curvature as the tube and of a length smaller than one third of the internode distance (12), to distribute over a larger area the compression caused by the tube on the bottom wall of the culm.

(5) FIG. 2 shows a cross-section of the system, in which the composite girders are arranged separated apart by a distance s whose magnitude depends on the structural design considering the load conditions of the system, the geometry of the target covered space, and the geometrical and mechanical characteristics of the bamboo and other materials. This figure shows the components of the slab in this section: the potential layers of the deck (2) forming the diaphragm (3), and the top (4) and the bottom (5) finishing, the bamboo culm (6), the profile (7), the bolt (8), the separator tube (9), the nuts (10) and the washers (11).

(6) FIG. 3 shows a possible geometric configuration of the composite pre-tensioned girder. This figure features the different components, whose number and arrangement will depend on factors such as the distance between the mounting supports on the ends, the acting loads and the architectural requirements and characteristics of the raw materials. The composite girders (1) rest on the ends over walls, columns or beams made of steel, concrete, wood or other material to provide support to the deck. The bamboo culm (6) may or may not have mortar (13), or other filling material in the internode spans where the beam rests, to prevent the occurrence of local failures. All the components are arranged so that the profile (7) is fastened to the ends of the bamboo culm, and there are one or more separator tubes (9) that produce a condition of stress to the profile and a condition of flexo-compression to the bamboo culm, compressing said tubes by pushing them towards the profile and the bamboo culm in opposite directions, until producing a cambered condition of the mechanical system and a pre-tensioned condition of the materials.

(7) The bamboo longitudinal compression condition is produced due to a stress balancing action exercised by the profile due to the transfer of load to the ends of the culm. The proposed system achieves a mechanical condition allowing to obtain a reduced bottom deflection lower than the maximum permitted by the Official Mexican Standards for building methods and the Building Regulations of the Federal District (Mexico City). The fastened composite girders (1) subject to the presence of service load adopt a slightly curved condition. The bends of the profile together with the mortar filling, if any, at the ends of the bamboo culm have the function of freeing the bamboo from the shear stress load produced by the bolts, causing that the transmission of the profile load to the bamboo is achieved through the compression of the culm in the direction of its longitudinal fibers.

(8) Any system used to keep the gap between the profile and the culm is considered a possible variation of the system, such as the introduction of nuts to prevent the culm and the profile from returning to their initial balance position. Another possible variation of the system is the introduction of additional bolts (with or without a tube) along the span length to cover greater distances. Another possible variation of the system is the introduction of any steel component that works under tension as a replacement of the profile, such as a rigid or flexible cable. Still another possible variation of the system is the absence of camber for roofs subject to a wind driven suction action. Other possible variations include any form of filling in any of the internode span to prevent local failures, or in points where there are bolts connecting to the deck, or elements for bracing the composite girder.

(9) The differences with the existing patented systems lay on the fact that in the present invention the compression is being absorbed by the bamboo culm section and not by a system with a girder manufactured with laminated bamboo. The stress is absorbed by a steel component placed outside the culm, thus achieving an optimum performance of the materials. The pre-tensioned condition makes the bamboo and the steel work together from the beginning and not when the stress forces from the service load start to appear. The condition of the girder ends at the mounting support free the bamboo culm from the possibility of crushing and/or tearing due to shear stress.

(10) The pre-tensioned composite girder has the fundamental property of dissipating energy due to its non-linear behavior to the failure.

(11) The present invention is a system of geometrical and mechanical configuration that meets all the requirements of the current domestic and foreign building regulations. The system is light in weight and, for example, during an earthquake it allows floor slab displacements of small magnitude, and its deformation condition due to dead and live loads is low due to the resistance of steel and bamboo, and the pre-tensioned condition of the composite girders.