EP3498928A1

EP3498928A1 - Structural system for constructing single-layer structures

Info

Publication number: EP3498928A1
Application number: EP17380026.9A
Authority: EP
Inventors: Joseba Xabier SANCHEZ CAMPOS; Mikel MONASTERIO CAMPILLO
Original assignee: Lanik I S A; Lanik I SA
Current assignee: Lanik I S A; Lanik I SA
Priority date: 2017-12-12
Filing date: 2017-12-12
Publication date: 2019-06-19
Anticipated expiration: 2037-12-12
Also published as: ES2846900T3; EP3498928B1; MX2018002233A

Abstract

The present invention relates to a structural system for a single layer based on nodes and bars joined to each other by means of screws threaded into bushings embedded and fastened to holes coaxial to the bars, the screws are introduced from the inside of the nodes through the through holes in the node.

Description

DESCRIPTION

The present invention relates to a structural system for constructing single-layer structures, based on nodes interconnected by bars.

Background of the invention

Single-layer structures made up of bars and nodes are used to cover large open spaces.
Generally, single-layer systems situate the nodes of the structures inside a surface parallel to the enclosure that they must normally fasten. This surface, which is called a "generatrix surface", will be able to have a simple curvature or a double curvature. The joints between nodes are formed by means of bars with different profiles. The assembly of the structure actually constitutes a polyhedron; the nodes of the structure are the vertexes of the polyhedron and the bars are the edges. The most normal lattices are made up of triangles or quadrilaterals. Except for in a few structures with very simple and regular geometries, for example in cylindrical arches, which have a simple curvature or in certain types of domes as long as they have rotational symmetry, the degree of diversity of the bars and of the angles formed between them is extraordinarily high, an aspect which strongly conditions the production processes.
An example of a connection system for single-layer spatial structures is the one described in patent ES2317818 , where a construction assembly for spatial structures is represented based on bars joined in nodes, the joint between said elements being made by means of screws that have two differentiated threaded portions separated by a stop, said first portion being threaded and said second portion being threaded, threaded in opposite directions. In the system described in patent ES2317818 , the twist angle, formed by the orientation vector of the bar and the projection of the orientation vector of the node in the plane perpendicular to the axis, is not very wide.

Description of the invention

The present structural system has been developed for constructing single-layer spatial structures.
Said structures of bars and nodes situate the nodes thereof in a surface with a double curvature, in other words, surfaces generated by the movement of a curved generatrix. Starting from this surface, the structure is formed by means of a mesh of triangles or quadrilaterals, such that the assembly constitutes a polyhedron inscribed in the cited surface. The axes of the bars of the real structure coincide with the edges of the cited polyhedron.
The bar-node joint of the system of the present invention has a high degree of embedding, mainly in the direction perpendicular to the generatrix surface. In the present system, the nodes are basically hollow cylindrical pieces, the main axis of which is arranged perpendicular to the plane tangent to the cited surface in the node itself. In the side surface of the cylinder, planes perpendicular to the axes face each other by which the bars that end in said node access it. In turn, through holes are machined, through which the connection with the end of the bar is formed.
The system described in the present invention admits a wide variety of angles of attack of the elements that make up the structure, as well as providing the structure with stability, strength and stiffness.
The present invention relates to a structural system for single layers based on nodes and bars joined to each other by means of screws threaded into bushings embedded and fastened to holes coaxial to the bars, the screws are introduced from the inside of the nodes through the through holes in the node.
Therefore, the first aspect of the invention relates to a structural system for constructing single-layer structures from among those that comprise bars, with at least one coaxial hole in each end of the bar, joined to nodes by means of joining screws, each node having at least one threaded through hole intended to receive the joining screw; wherein a bushing with an inner threading embedded and fastened in the coaxial holes of the ends of the bar houses the joining screw that fastens bar-node joint.
Another advantage of the bushing is that in this way a linear joint without gaps is formed, in addition to the bushings staying completely hidden inside the bar with which it reduces the aesthetic impact.
There are three angles involved in the connections of the bars to the node: horizontal angle, the system enables any horizontal angle of attack, with the only condition that the angles between the bars condition the size of the node due to the need to prevent interference between the bars; vertical angle, the limitation of this angle is given by the height of the profile of the bar and the thickness of the initial perforated tube in order to generate the node, such that if the vertical angle is larger, a greater thickness of the initial perforated tube is necessary so that the inclination of the plane that is made with the node does not cause an excessive loss of material; twist angle, this angle is a direct geometric consequence derived from the fact that the orientation vectors of the nodes joined by a bar do not necessarily have to be contained in one plane. This implies that the bar has to acquire a compromise orientation inclined with respect to the two end nodes thereof. The twist angle is precisely the one formed by the orientation vector of the bar and the projection of the orientation vector of the node in the plane perpendicular to the axis of the bar.
The manufacturing method of the nodes is assisted by computer, in particular machined by CAM, which results in a drastic reduction in necessary graphic documentation and enables free and complex geometries to be made without increasing engineering costs. The geometric repeatability of the nodes stops being a requirement when the geometry of each node is automatically generated by means of design software tools. It is not necessary to make detail or exploded diagrams of nodes, given that the information that defines them is gathered in lists of parameters that directly feed the machine language templates that the machining centers use.
Moreover, the automated geometric resolution also results in the definition of the exact lengths of the bars that make up the structure. These in turn are manufactured by means of cutting and positioning machines fed directly by parameters obtained from the calculation software.
The nodes and the bars are manufactured in very flexible and highly automated industrial installations. The pre-manufacturing thereof enables high levels of diversification, precision and finish to be obtained. The nodes and bars are easily stackable and are shipped to the worksite in containers once they are adequately painted, achieving a high volumetric yield. At the worksite, it is only necessary to screw in the different elements.
Another aspect of the present invention is the single-layer structure that comprises a structural system of the invention which comprises a plurality of nodes and a plurality of bars screwed into said nodes, said structure configuring a polyhedron with edges defined by said bars.

Brief description of the drawings

For the purpose of helping to make the foregoing description more readily understandable, it is accompanied by a set of drawings which, schematically and by way of illustration and not limitation, represent an embodiment.

Figure 1 shows an exploded view of the system of the invention.
Figure 2 shows a cross section along the AA' axis that is shown in figure 1.
Figure 3 is a perspective view of the node of the example of the invention.

Description of a preferred embodiment

As described, the first aspect of the invention relates to a structural system for constructing single-layer structures from among those that comprise bars (1), with at least one coaxial hole (2) in each end of the bar, joined to nodes (3) by means of joining screws (5), each node (3) having at least one threaded through hole (6) intended to receive the joining screw (5); wherein a bushing (4) with interior threading embedded and fastened in the coaxial holes (2) of the ends of the bar houses the joining screw (5) that fastens the bar-node (1, 3) joint.
Preferably, the bars (1) are made of wood. Wood has advantages compared to other materials like steel, such as reducing carbon footprints, not undergoing corrosion, having controlled behavior when exposed to fire without needing to use intumescent coatings. Unlike other types of wooden joints based on fittings and bolts, the behavior of the system of the invention is linear for the whole range of admissible forces. This is especially important when trying to resolve single-layer structures by compression, where the occurrence of overall sagging is directly related to the behavior of the node; in particular, to the stiffness and linearity of the joint. More preferably, wood has high strength, such that the cross-section thereof can be smaller with respect to traditional laminate woods and that are similar to the profile heights used in steel, avoiding the extra costs of larger profiles.
Preferably the cross-section of the bar (1) is rectangular. Preferably the ends of the bar (1) are formed of rectangular covers that have two coaxial holes (2).
Preferably the nodes (3) are made of steel. Preferably the node (3) is a hollow cylindrical body, open at both ends, in order to enable access to the joining screws (5) with which the node (3) joins the ends of the bar, through the outer face, the cylindrical body has planes that give support to the corresponding ends of the bar. More preferably these planes have a frustoconical cross section. Preferably the nodes (3) have two threaded through holes in each of the faces thereof that are complementary to the two coaxial holes (2) of the ends of the bars (1).
Preferably, the threaded through holes of the nodes for the introduction of the outer end of the bushing are countersunk holes, so that the head of the screw is seated correctly. These countersunk holes are concentric to the through holes of the node and the axis thereof can cut across the orientation axis of the node or not; for which reason it preferably has an eccentricity that enables the twist angle in the node.
Preferably the bushing with inner thread (4) embedded and fastened in the coaxial holes (2) of the ends of the bar is fastened with an adhesive agent. More preferably the adhesive agent is a resin.
In order to guarantee a good dimensional tolerance in the bar (1), the contact with the node (3) is made by the bushings (4), which slightly project with respect to the bar, such that the contact is made between bushing (4) and node (3) and not between bar (1) and node (3). Thus, the preloading of the screws (5) is carried out with the node (3) against the bushing (4) and the joint with the adhesive agent remains unloaded initially. On a dimensional tolerance level, this prevents the bar (1) from being what limits the longitudinal tolerance.
Preferably, there are two holes (2) in the ends of the bar. The fact that there are two joints screwed into the end of each bar has the aim of transmitting bending stress.
As for the capacity to transmit types of stress, axial, bending and shearing stresses can be discussed. The structural stress is transmitted between bars (1) through the node (3) by means of the following elements: first, the bar (1) made of high-strength laminate wood transfers the stress to two metal bushings (4) by means of the joint with the adhesive agent; the bushings (4) are in direct contact with the node (3) and pressed against it by the preloading of the screws (5). Thus, if there is compression, the bushings (4) transmit the load directly to the node (3). If there is tensile stress, it will be due to the screw (5) by means of the head thereof, it being responsible for transmitting this stress to the node (3). The wall of the node (3) between the head of the screw (5) and the bushing (4) is calculated in order to offer at least the same resistance as the screw (5) itself; finally, it is the node (3) itself that transmits the stress between the bars (1) that come together in it.

Claims

A structural system for constructing single-layer structures from among those that comprise bars (1), with at least one coaxial hole (2) in each end of the bar, joined to nodes (3) by means of joining screws (5), each node (3) having at least one threaded through hole (6) intended to receive the joining screw (5); wherein a bushing (4) with interior threading embedded and fastened in the coaxial holes (2) of the ends of the bar houses the joining screw (5) that fastens the bar-node (1, 3) joint.
The structural system according to claim 1 characterized in that the cross section of the bar (1) is rectangular.
The structural system according to any of claims 1 to 2 characterized in that the ends of the bar (1) are formed of rectangular covers that have two coaxial holes (2).
The structural system according to any of claims 1 to 3 characterized in that the node (3) is a hollow cylindrical body, open on both sides, in order to enable the access of the joining screws (5).
The structural system according to any of claims 1 to 4 characterized in that the planes of the outer face of the node (3) are planes with a frustoconical cross section.
The structural system according to any of claims 1 to 5 characterized in that the nodes (3) have two through holes in each of the faces thereof, complementary to the two coaxial holes (2) of the ends of the bars (1).
The structural system according to any of claims 1 to 6 characterized in that the through holes of the nodes are countersunk holes.
The structural system according to any of claims 1 to 7 characterized in that the through holes of the nodes are threaded holes.
The structural system according to any of claims 1 to 8 characterized in that the bushing with inner threading (4) embedded and fastened in the coaxial holes (2) of the ends of the bar is fastened with an adhesive agent.
The structural system according to any of claims 1 to 9 characterized in that the bars are made of wood.
A single-layer structure that comprises a structural system according to any of claims 1-10 which comprises a plurality of nodes and a plurality of bars screwed into said nodes, said structure configuring a polyhedron with edges defined by said bars.