EP4308770A1

EP4308770A1 - Fastener for arranging a framework with profiled elements curved along pseudo-geodesic curves

Info

Publication number: EP4308770A1
Application number: EP22713712.2A
Authority: EP
Inventors: Olivier Baverel; Romain MESNIL
Original assignee: Ecole Nationale des Ponts et Chaussess ENPC
Current assignee: Ecole Nationale des Ponts et Chaussess ENPC
Priority date: 2021-03-17
Filing date: 2022-03-14
Publication date: 2024-01-24
Also published as: CA3208229A1; FR3120881B1; WO2022195209A1; US20240218654A1; FR3120881A1; AU2022239885A1

Abstract

The subject of the invention is a fastener (1) for securing two profiled elements together, comprising two half-fasteners (2, 3) linked together by a link (4) of the fixed pivot type allowing one half-fastener (2, 3) to pivot with respect to the other about a pivot axis (AX), each half-fastener (2, 3) having a fixing member (11) for fixing a profiled element (18) which is inclined with respect to the pivot axis (AX). This fastener makes it possible form a gridshell by securing pseudo-geodesic longitudinal profiled elements to pseudo-geodesic transverse profiled elements.

Description

Title: Attachment for the arrangement of a frame with curved sections according to pseudo-geodesic curves

TECHNICAL AREA

The invention relates to a framework comprising bent sections which intersect to jointly delimit a curved surface, being secured to each other by fasteners. PRIOR ART

In such an arrangement, also called "gridshell", the sections are deformed in their elastic range to follow curved shapes, and they are secured to each other at their intersections so as to jointly constitute a rigid structure delimiting the shape of a surface. curved such as a dome shape.

In this type of arrangement, the fasteners which secure the elastically bent sections together give the assembly the required mechanical rigidity, this structure once in place having a potential energy corresponding to the elastic deformation of the sections which compose it. As shown in Figure 1, when viewed in a cross-sectional plane, a profile has an axis 11 of greatest quadratic moment, and another axis 12 perpendicular to 11 having a quadratic moment less than or equal to its quadratic moment with respect to axis 11.

The axis of greatest quadratic moment 11 corresponds to that around which the profile has the greatest bending stiffness. In the case of a rectangular profile, axis 11 extends parallel to the narrowest sides of the profile, and axis 12, which corresponds to that for which the profile has the lowest rigidity, extends parallel to the sides. the widest. To increase the mechanical rigidity of such gridshells, it is possible to use sections with a non-round section such as sections with a rectangular section, made of steel, of composite material, or other.

One possibility is to arrange the profiles so that they follow so-called geodesic curves of the surface to be delimited, a curve being geodesic if at each of its points, the normal to the surface coincides with the normal to the curve when it is defined .

In practice, the sections of a gridshell with geodesic lines are curved in bending around the axis of weakest quadratic moment of their section. In the case of a geodesic gridshell formed of sections of rectangular section, each section is thus arranged so that its widest sides extend parallel to the surface, its narrowest sides extending perpendicular to the latter.

The significant flexibility of the sections around their axis of weakest quadratic moment thus makes it possible to delimit a dome-shaped surface, by using first longitudinal sections and second transverse sections jointly forming a regular grid in the shape of a dome.

However, in a geodesic gridshell, the mechanical rigidity is conditioned by the weakest quadratic moment of the section of the sections used, which is penalizing for the dimensioning of these sections and therefore of the structure. Therefore, it may be necessary to stack several longitudinal or transverse sections to obtain the required mechanical rigidity.

Another possibility consists in arranging the sections so that they follow so-called asymptotic curves of the surface to be delimited, a curve being asymptotic if at each point of the latter, the curvature of the surface, in a plane containing the tangent to the curve and the normal to the surface, is zero.

In the case of an asymptotic gridshell formed of rectangular sections, each section is arranged so that its widest sides extend perpendicularly to the surface, its narrowest sides extending parallel to this surface. Thus, in the case of an asymptotic gridshell, the mechanical rigidity is conditioned by the highest moment of inertia of the section of the sections used, which is advantageous in terms of dimensioning of the sections and therefore of the structure.

Nevertheless, the choice of asymptotic curves limits the variety of surfaces that can be delimited by an asymptotic gridshell: they are limited to surfaces with negative Gaussian curvature, which does not allow, for example, to mesh a curved surface such as a surface spherical or domed surface.

The object of the invention is to provide a solution making it possible to constitute a gridshell which can delimit a wide variety of surfaces and leading to an advantageous dimensioning of the sections used.

DISCLOSURE OF THE INVENTION

To this end, the subject of the invention is a clip for securing two sections together, comprising two half-clips linked to each other by a fixed pivot-type connection allowing a half-clip to pivot relative to the other about a pivot axis, each half-attachment comprising a member for fixing a section which is inclined relative to the pivot axis.

Such an attachment makes it possible to maintain a profile inclined with respect to a surface that this profile contributes to delimit, so that the profiles can follow curves of the pseudo-geodesic type, which makes it possible to delimit a wide variety of surfaces including in particular surfaces with positive Gaussian curvature, such as domed surfaces.

The invention also relates to a fastener thus defined, in which the inclination of each fastener member relative to the pivot axis is adjustable.

The invention also relates to a clip thus defined, in which each half-clip comprises a base and a bracket carrying the fixing member, the bracket being linked to the base by a fixed pivot type link allowing its rotation relative to the base around an axis of rotation normal to the pivot axis of the attachment, and a system for locking the inclination of the peg relative to the pivot axis. The invention also relates to a fastener thus defined, in which the hook comprises two flanges extending on either side of the base, these two flanges each having an edge rigidly secured to the fixing member, these two flanges being linked to the base by the pivot connection, each flange comprising an edge in the form of an arc of a circle centered on the pivot connection with holes regularly spaced along this edge, the locking system comprising a pin which can engage together in a hole in each flange and in a hole in the base.

The invention also relates to a fastener thus defined, in which the inclination of the fastening members with respect to the pivot axis is adjustable over an angular range extending from 0° to 90°.

The invention also relates to a fastener thus defined, in which the fastening member has the shape of a jaw delimited by two flat portions spaced apart from each other by a distance corresponding to the thickness of the profile to be maintained.

The invention also relates to a frame delimiting a curved surface comprising first elastically bent sections and second elastically bent sections intersecting the first sections, in which the sections are fixed to each other by fasteners thus defined.

The invention also relates to a framework thus defined, in which the sections are hollow sections with a rectangular section.

The invention also relates to a framework thus defined, comprising sections which are strips of constant width.

BRIEF DESCRIPTION OF DRAWINGS

Figure 1 is a schematic representation of a rectangular section profile;

Figure 2 is a perspective view of the clip according to the invention;

Figure 3 is a side view of the clip according to the invention;

Figure 4 is a side view of an example of a domed gridshell established in accordance with the invention; Figure 5 is a front view of an example of a domed gridshell established in accordance with the invention;

Figure 6 is a top view of an example of a domed gridshell constructed in accordance with the invention.

DETAILED DISCUSSION OF PARTICULAR EMBODIMENTS

The basic idea of the invention is to establish a mesh of the left surface by means of sections following pseudo-geodesic curves of the surface which they delimit, these sections crossing while being fixed to each other by so as to jointly constitute a rigid mesh.

A curve is pseudo-geodesic when at any point of it, the normal to the curve forms a non-zero constant angle with the normal to the surface. In general, the pseudo-geodesic curves make it possible to delimit a greater variety of surfaces, these surfaces being able in particular to have a negative or positive Gaussian curvature as for example in the case of a dome shape.

In the gridshell according to the invention, the sections follow pseudo-geodesic curves of the surface which they delimit by being deformed in bending and/or in torsion in their elastic domain. To this end, these profiles are secured to each other at each crossing by specific fasteners ensuring that each profile is held at a predetermined inclination with respect to the surface.

The fasteners used are advantageously all identical and of the type of fastener shown in Figures 2 and 3 where it is marked 1.

This attachment 1 comprises two identical half-attachments 2 and 3 which are mounted head to tail while being coupled to each other by a connection of the fixed pivot type 4, of axis AX, each half-attachment being symmetrical with the other relative to the center of the pivot link 4.

The half-attachment 2 comprises a base 6 comprising a tubular portion 7 oriented along the axis AX, which carries a hook 8 formed of two flat flanges 9 and 10 secured to each other by a fixing member 11, the hook 8 having an adjustable orientation with respect to the base 6. The two flanges 9 and 10 are flat and extend parallel to each other on either side of the base 6. Each flange 9, 10 is a flat sheet metal plate having an outline in the shape of a sector angular. This contour comprises a first rectilinear edge 12 and a second rectilinear edge 13 joined together at a vertex S, and an arcuate edge 14 having the shape of an arc of a circle centered on the vertex S, this arcuate edge connecting the two ends of the edges 12 and 13 which are opposite the vertex S. In the example of the figures, the rectilinear edges 12 and 13 form between them an angle close to the right angle.

These two flanges are arranged at a distance from each other facing each other, the flange 10 being the image of the flange 9 by a translation in a direction normal to the plane of the flange 10, over a distance corresponding to the diameter of the tubular portion 7.

These two flanges are rigidly secured to one another by the attachment 11 rigidly secured to their respective second edges, and which is intended to receive a portion of a section of the structure.

In the example of the figures, this binding 11 essentially comprises a plate folded into a U-shape to form two flat portions 16 and 17, rectangular and parallel, which are spaced apart from each other by a distance corresponding to the thickness of the profile to receive, and which have a length, counted in the direction of the second edges to which they are fixed, which corresponds to the width of this profile.

In the example of the figures, this attachment 11 receives a profile 18 which is of the “flat” type, that is to say formed of an initially flat strip, metallic or of composite material or other.

As visible in Figures 2 and 3, the hook 8 is secured to the base 6 by a connection of the fixed pivot type 5, of axis AY normal to the axis AX located at the top S, which allows adjust the orientation of the hook 8 with respect to the base 6, this orientation being immobilized by a locking system.

As such, the flanges 9 and 10 include along their arcuate edges a series of holes 19 regularly distributed along this edge, and the portion tubular of the base 6 carries at its end furthest from the pivot connection 4 a spacer 21 rigidly secured to the free end of the tubular portion 7 and which is traversed by a bore oriented parallel to the axis AY.

As shown in Figure 2, the blocking of the hook 8 relative to the base 6 is ensured by positioning the hook at the desired angular position by rotating it around the axis AY, until placing one of the holes 19 of the flange 10 opposite the through hole of the spacer 21 to engage through the hole and the hole a locking pin 22.

Advantageously, the inclination adjustment of the peg is possible over a range extending from 0° to 90°. When the hook is inclined at 0°, the fixing 11 extends parallel to the axis AX, that is to say perpendicular to the surface delimited by the gridshell, which corresponds to a limit case of profile following an asymptotic curve .

When the hook is inclined at 90°, the fixing 11 extends perpendicular to the axis AX, that is to say parallel to the surface delimited by the gridshell, which corresponds to another limit case of a following section a geodesic curve.

All the intermediate inclinations between 0° and 90° correspond to the maintenance by the attachment of sections following pseudo-geodesic curves along the surface which they delimit.

The inclination of the attachment 11 corresponds to the inclination of the axis of weakest quadratic moment of the section that this attachment 11 receives, relative to the axis AX of pivoting of the half-attachments which coincides with the normal to the surface delimited by the sections constituting the gridshell.

In the example of Figures 2 and 3, the binding 11 essentially comprises two flat portions 16 and 17 which delimit a kind of U-shaped jaw in which the profile engages. Additionally, this attachment 11 may comprise snap-fastening claws ensuring that the profile cannot come out of the attachment 11 once it has been engaged therein. Additionally, or alternatively, the profile can be secured to the fixing by gluing, riveting, bolting or any other appropriate means. Thus, in the example of the figures, the fixing 11 has the shape of a jaw intended to enclose the profile which it receives, but this fixing can also be reduced to a simple plate to which is fixed a side of the profile which it is meant to receive.

In practice, the establishment of a gridshell according to the invention consists in determining the surface to be delimited by the sections. In the example of Figures 4 and 5, a dome-shaped surface 23 has been chosen having, as can be seen in Figure 4, a length L greater than its width I which appears in Figure 5, this dome shape approaching that of a portion of an ellipsoid of revolution.

A set of pseudo-geodesic curves, comprising on the one hand curves extending essentially along a longitudinal direction on this surface, and on the other hand curves extending essentially along a transverse direction on this surface, is then determined. The longitudinal curves are chosen to be spaced as evenly as possible from each other, and likewise for the transverse curves which intersect these longitudinal curves. Advantageously, the surface and the curves are defined by successive calculations carried out on a numerical modeling of the structure.

A three-dimensional frame having the role of a template is advantageously constructed to receive the sections to delimit the surface. Transverse sections 24 are then inclined, bent, positioned and fixed on this frame in accordance with the previously determined three-dimensional longitudinal pseudo-geodesic curves. To this end, the frame is equipped with appropriate fastening systems for the sections, these systems possibly being of the same type as the fasteners according to the invention.

At this stage, the gridshell's own fasteners are fixed to the transverse sections carried by the frame, at each point of intersection with a longitudinal pseudo-geodesic curve, these intersection points having been previously identified and located.

For each attachment, the inclination of one of the hooks is adjusted to the angle corresponding to the transverse profile to which this hook is fixed, and the second hook of this fastener is adjusted to the angle of inclination of the longitudinal profile that it is meant to receive. In practice, the inclination of a profile with respect to the surface is the same all along this profile, but two profiles can have different inclinations with respect to the surface. Each attachment comprising two hooks whose angular orientations must be adjusted, the hook settings may be different on each fastener.

At this stage, the longitudinal sections 26 can be positioned, tilted and flexed in accordance with the previously defined longitudinal pseudo-geodesic curves, and they are fixed to the transverse sections by the fasteners which were fixed thereto in the previous step. Once all the longitudinal sections have been installed and fixed, the transverse sections can be separated from the fixing systems by which they were secured to the three-dimensional frame. At this stage, the gridshell is constituted, that is to say that it can for example be handled in order to be transported from the frame to the load-bearing structure of a building intended to receive it. In this gridshell, each longitudinal section is inclined at a certain angle with respect to the dome-shaped surface so as to follow a pseudo-geodesic curve, the inclination of one of the longitudinal sections having been identified by "alpha". in FIG. 5. Similarly, each transverse section has, with respect to the domed surface, a predetermined inclination corresponding to the adjustment of the angles of the pegs which ensure its maintenance. As noted above, once the gridshell is made, each clip has its pivot axis oriented perpendicular to the surface of the gridshell.

Claims

1. Attachment (1) for securing two sections to one another, comprising two half-attachments (2, 3) connected to each other by a connection (4) of the fixed pivot type allowing a half - clip (2, 3) to pivot relative to the other about a pivot axis (AX), each half-clip (2, 3) comprising a member (11) for fixing a section (18) which is inclined relative to the pivot axis (AX).

2. Fastener (1) according to claim 1, wherein the inclination of each fixing member (11) relative to the pivot axis (AX) is adjustable.

3. Fastener according to claim 2, in which each half-fastener (2, 3) comprises a base (6) and a hook (8) carrying the fixing member (11), the hook (8) being linked to the base (6) by a fixed pivot type connection (5) allowing its rotation relative to the base (6) around an axis of rotation (AY) normal to the pivot axis (AX) of the clip (1), and a system for locking the inclination of the peg (8) with respect to the pivot axis (AX).

4. Fastener according to claim 3, wherein the hook (8) comprises two flanges (9, 10) extending on either side of the base (6), these two flanges (9, 10) each having an edge (13) rigidly secured to the fixing member (11), these two flanges (9, 10) being linked to the base (6) by the pivot connection (5), each flange (9, 10) comprising an edge (14) in the form of an arc of a circle centered on the pivot link (5) with holes (19) regularly spaced along this edge (14), the locking system comprising a pin (22) which can engage together in a hole (19) in each flange and in a hole in the base (6).

5. Fastener according to claim 2, wherein the inclination of the fixing members (11) relative to the pivot axis (AX) is adjustable over an angular range extending from 0° to 90°.

6. Fastener according to one of the preceding claims, in which the fixing member (11) has the shape of a jaw delimited by two planar portions (16, 17) spaced apart from each other by a distance corresponding to the profile thickness to be maintained.

7. Framework delimiting a curved surface comprising first elastically bent sections (24) and second elastically bent sections (26) crossing the first sections (24), characterized in that the sections (24, 26) are fixed to each other by fasteners (1) as defined in one of the preceding claims.

8. Frame according to claim 7, wherein the sections (26) are hollow sections of rectangular section.

9. Framework according to claim 7 or 8, comprising sections (24,

26) which are bands of constant width.