EP0342114A1 - Assembly consisting of an exterior building wall such as a roof covering or cladding and a metal rail section for supporting the same - Google Patents

Abstract

The rail is of the type comprising two flanges, outer (3) and inner (4) respectively, which are parallel and of equal thickness, and a web (5) which joins the said two flanges, the outer flange (3), against which the wall (2) to be supported is laid, moreover being fastened to this wall, for example by means of self-tapping screws (6), and the inner flange (4), in danger of buckling, resting on at least two supports (7). The inner flange (4) is continuously of considerably greater width than the width of the outer flange (3), the ratio between the said widths being between 1.2 and 2. It is employed in the supporting of an external building wall such as a roof covering or a wall cladding.

Description

The present invention relates to a profiled metal purlin intended to support an exterior wall of a building such as a covering, horizontal or substantially horizontal, or cladding, vertical or substantially vertical, said purlin being of the type comprising two parallel flanges, respectively exterior and interior. , which are of equal thickness, and a core which joins said two soles, the outer sole against which the wall to be supported is applied, being additionally secured to this wall, for example by self-tapping screws, and the insole, in danger of buckling, based on at least two supports.

To support loads between two supports, a beam is generally used which works on bending, the forces to which this beam is subjected acting transversely to its length; this is the case with a bridge beam, an overhead crane beam or a joist for example.

We know that, in such a beam, the cross section of which is usually symmetrical with respect to a plane parallel to the wall to be supported, and in which consequently the flanges are of equal width and thickness, the distribution of stresses is performs according to a bi-triangular diagram whose common apex passes through the neutral fiber of the beam, that is to say through the intermediate fiber which includes the centers of gravity of all the sections and which is consequently located at mid height of the web of the beam.

Under the action of the loads, the beam flexes and deforms: unlike the neutral fiber whose length does not vary, the fibers located on the concave side of the beam are then shortened and are therefore subjected to compression, while those located on the convex side are elongated.

Taking into account the stress distribution diagram, it is agreed that, for optimal use of the material, it is desirable to concentrate it as far as possible from the neutral fiber, which corresponds to the zone of zero stress.

This observation, combined with other considerations such as the saving of material, the reduction in weight and consequently the reduction in the price of the works, justified the design of beams with an I-shaped profiled section, or with a neighboring profiled section. or derived from such a section in I.

These beams, commonly used in metal constructions, therefore comprise two parallel flanges of the same width and the same thickness joined by a core which, depending on the case, can be flat or itself profiled.

However, the compressed sole of the beam, like all the elements subjected to compression, tends to slip away in a plane perpendicular to the stress. This change in shape in a direction different from that of the stressing forces, and which cannot be done in the plane of great inertia of the beam, results in a lateral buckling of the beam causing it to spill.

It is for this reason in particular that the upper flanges of the beams, for example those supporting overhead traveling cranes, are stiffened laterally, generally by a truss beam.

The thinner and lighter profiled beams, called purlins, which are more particularly intended to support the exterior walls of buildings, such as roofing or cladding, are also long pieces subjected to bending.

However, given the low loads that these breakdowns have to bear (lightness of the covers, dust and snow, wind, for example), the most restrictive condition that these wall support breakdowns have to respect is the limitation due to the maximum deflection imposed by regulations and which, under service charges, is generally 1/200 of range.

To reduce the deflection of a slight profiled failure, manufacturers use two means:
- by manufacturing stiffer profiles, that is to say profiles of greater heights, and preferably using cold profiling of thin sheets,
- by creating continuity on supports, either by interlocking of the flanges formed at the level of the wings when the profiles are in Z section, or by splicing by means of internal or external fishplates to the pieces to be butted when these are of a profile other than Z.

In all these constructions, whatever the section of the purlin profile, whatever the wall which this purlin must support, and whatever the inclination of this wall, the so-called "outer sole" against which the wall is applied is generally attached to said wall, for example by self-tapping screws. This outsole is therefore correctly stabilized when it is compressed.

On the other hand, the so-called "inner" sole of the purlin rests freely on its supports and is not stabilized laterally; when this sole is compressed, it can therefore cause the breakdown by lateral buckling.

However, given the lightness of the walls, covers or cladding, currently used, the profiled purlins which support them are subjected to bending in both directions, depending on whether the loads are oriented towards the interior of the building to be protected (case of snow, dust, and dead weight of roofing for example), or towards the outside of the building (wind for example).

In the case of a load oriented towards the interior of the building to be protected, the insole of each support failure, due to the continuity on the supports, is compressed in each support zone, i.e. on each support and on either side, near said support.

In the case of a load oriented towards the outside of the building to be protected, it is in the central part between two supports, that is to say in the middle of the range of each support failure, that the insole of said profile is compressed.

• a) de donner à la semelle extérieure, contre laquelle est appliquée la paroi à supporter, une largeur minimale compatible, d'une part, avec une bonne raideur latérale permettant de limiter les déformations latérales pendant le montage et la mise en place de la paroi et, d'autre part, avec un appui jugé suffisant pour les matériaux de couverture et/ou de bardage, et pour les attaches de ces matériaux (une largeur de 50 à 70 millimètres paraît en général suffisante à cet égard),
• b) d'élargir la semelle intérieure, de manière à réduire la contrainte qui lui est appliquée, en réduisant sa distance au centre de gravité constituant la fibre neutre, et simultanément de manière à accroître sa raideur latérale afin qu'elle résiste mieux au flambement latéral.

From this knowledge and observations, the company filing this patent application has therefore come to the conclusion that, to optimize the use of the material on any wall support failure, it would be advisable:

• a) to give the outer sole, against which the wall to be supported is applied, a minimum compatible width, on the one hand, with a good lateral stiffness making it possible to limit lateral deformations during the mounting and the positioning of the wall and, on the other hand, with support deemed sufficient for roofing and / or cladding materials, and for the fasteners of these materials (a width of 50 to 70 millimeters generally seems sufficient in this regard),
• b) to widen the insole, so as to reduce the stress applied to it, by reducing its distance from the center of gravity constituting the neutral fiber, and simultaneously so as to increase its lateral stiffness so that it better resists buckling lateral.

• a) à profil à section en Z, tel que l'enseigne le brevet FR-A-2.088.237 lorsqu'il convient au surplus de créer une continuité sur appuis par emboîtement de leurs semelles ; il faut malgré tout préciser à cet égard que la semelle la plus large est d'une largeur supérieure seulement de 10 à 15 à la semelle la moins large et que, du fait précisément de l'emboîtement, il y a sur chaque face de la poutre formée alternance de semelles larges et de semelles étroites ;
• b) à profils à section en I ou en C, tels que l'enseignent les brevets GB-A-2.102.465 et FR-A-2.358.524, la semelle extérieure ayant alors une largeur notablement supérieure à celle de la semelle intérieure, et les semelles ayant au surplus des épaisseurs alors différentes, l'une par rapport à l'autre, et inégales au niveau de chaque semelle.

These two trends - reducing the width of the outer sole and increasing the width of the inner sole - are in total contradiction with current conceptions which want:
- either the purlins have parallel soles, of the same width and of equal thickness; these purlins are then profiled in a conventional cross section in I or in a cross section in C, as taught for example by patents GB-A-1,562,688 and EP-A-0,163,712;
- either the purlins have parallel flanges, but of different widths and are then:

• a) with a Z-section profile, as taught in patent FR-A-2,088,237 when, moreover, it is appropriate to create continuity on supports by fitting their soles; however, it should be noted in this regard that the widest sole is only 10 to 15 times wider than the narrower sole and, precisely because of the interlocking, there is on each face of the beam formed alternating wide soles and narrow soles ;
• b) with I or C section profiles, as taught by the patents GB-A-2,102,465 and FR-A-2,358,524, the outsole then having a width significantly greater than that of the insole , and the soles having in addition thicknesses which are then different, one with respect to the other, and unequal at the level of each sole.

The present invention, going against current recommendations and habits, therefore proposes a wall support failure with an asymmetrical profile, and of which more precisely the flanges are of different widths, while being of equal thickness, it is that is to say both constant at each sole and equal for both soles.

The present invention therefore has for first object a profiled metal purlin intended to support an exterior wall of a building, such as a covering or cladding, said purlin being of the type comprising two footings, respectively external and internal, which are parallel and of equal thickness. , and a core which joins said two flanges, the outer flange against which the wall to be applied is applied, being additionally secured to this wall, for example by self-tapping screws, and the flange, in danger of buckling, resting on at least two supports, said purlin being characterized in that its inner sole is of a width continuously between 1.2 and 2 times the width of the outer sole.

In other words, over the entire length of each profiled purlin supporting the wall, the insole not stabilized by said wall is continuously and notably wider than the stabilized outsole.

According to a preferred embodiment, the inner sole of the profile is preferably of a width continuously between 1.4 and 1.8 times the width of said outer sole.

In a first alternative embodiment, the longitudinal axes of symmetry of the soles, respectively exterior and interior, belong to a plane perpendicular to said soles. This is the case for I-section profiled purlins, purlins marketed under the brands "Pannerval" and "Propanne", and Z-section profiled purlins in which the core, by construction, is also inclined on the two flanges that it brings together.

In a second variant embodiment, the longitudinal axes of symmetry of the soles, respectively exterior and interior, belong to a plane which forms with each of said soles an angle different from 90 °. This is the case with I-shaped section, C-section or Z-section purlins in which the core, by construction, is perpendicular to the two flanges.

The advantages of the invention, as well as certain other of its characteristics, will be clearly understood on reading the additional description which follows and with reference to the appended drawings which form an integral part of this description, said drawings representing in particular, by way of purely illustrative and nonlimiting examples, various preferred embodiments of said invention.

Figure 1 shows schematically, in cross section, a conventional profiled purlin (1) with a straight I-section intended to support an exterior wall (2) of a building. This purlin (1), for example and preferably obtained by cold profiling, comprises two parallel soles, respectively exterior (3) and interior (4), and a core (5) which joins said two soles, the exterior sole (3 ) against which is applied the wall to be supported being surplus to this wall, for example by self-tapping screws shown diagrammatically by the centerline (6), and the insole (4), in danger of buckling as shown diagrammatically by the arrow (10), resting on at least two supports (7).

The profile of this breakdown (1) is symmetrical with respect to the plane (8), parallel to the wall (2) to be supported, which passes through the neutral fiber (9) located halfway up the profile (1).

We know that the distribution of the stresses, in this symmetrical section (1) subjected to a bending stress, is carried out according to the bi-triangular diagram represented in FIG. 2.

Figures 3a, 3b, 4a and 4b schematically illustrate the means used to create continuity on the support of profiled purlins, with a straight section in I and a straight section in Z respectively.

In FIGS. 3a and 3b which are, respectively, a side view and a cross-sectional view of the abutment zone of two purlins (1) at I, continuity on the supports (7) is obtained by means of one or two external ribs (11) the height of which is slightly less than the height of the core (5) of each purlin (1), the splice or said ribs (11) being welded to the cores of the two purlins (1) abutments. In another case where the purlins to be butted would have a cross section at C, the fishplates creating continuity could be external and / or internal to these purlins, being once again welded to their butted cores.

In FIGS. 4a and 4b which are, respectively, a side view and a cross-sectional view of the overlap area of two identical purlins (12) and (13), with a cross section in Z, the continuity on the supports ( 7) is obtained by fitting the flanges formed at the wings of said Z-shaped purlins, the respective widths of these wings being such that there is a difference between them roughly equal to twice the thickness of the purlins. Thus, the continuity of the beam is obtained on the support (7) by fitting the narrow sole of the purlin (13) into the wide sole of the purlin (12) and vice versa by fitting the narrow sole of the purlin (12) in the wide sole of the purlin (13). The beam obtained therefore has a doubling of its section at each support (7). In this construction, the widest sole of each purlin (12, 13) is approximately 10% greater in width, and at most 15% greater in width, than the narrower sole.

It should be noted that, precisely because of the interlocking, each face of the beam obtained is formed by alternating wide soles and narrow soles. Consequently, in the calculation of the ultimate bending moments in span under the rising and falling loads respectively, bending moments which constitute the performance indices of the beam, the value retained for the width of each sole is always that of the sole la narrower, for obvious security reasons.

Finally, it has been shown in Figures 5a and 5b the constraints to which a failure may be subject, whatever in this regard the means ensuring its continuity on the supports (7).

In the case of a load (A) going from the outside to the inside of the building to be protected (Figure 5a), load possibly due to the dead weight of the wall if it is horizontal and possibly to snow, the insole (4), due to the continuity on supports, is compressed to the right of each support and close to each support, as shown by a strong line, while the outsole (3) is compressed in mid-range, this last compression (also shown schematically by a strong line), however, poses no stability problem since the outer sole (3) is attached by screws (6) to the wall (2) to be supported.

In the case of a load (B) going from the inside to the outside of the building to be protected (Figure 5b), load due for example to the wind which rushes under the roof of the building, the insole (4) is this time compressed in the middle of the range, in the central part between two supports (7), as shown by a strong line, while the outer sole (3) is compressed at the right of each support and near each support, as it is also shown diagrammatically by a strong line.

Since the outer sole (3) is in all cases attached to the wall (2) to be supported, the problem of lateral stability does not arise at its level; there is no danger of buckling, and therefore this sole exterior may have a minimum width, simply compatible with good lateral stiffness to limit lateral deformations during assembly and positioning of the wall and also simply sufficient to offer good support to the elements of the wall (2) to be supported.

In view of these conditions, an outer sole (3) with a width of the order of 50 to 70 millimeters will generally be sufficient.

On the other hand, the insole (4) which rests freely on the supports (7) is in danger of buckling at each of its points where it can be compressed, that is to say at the right and near each support under the downward and mid-span loads as well as at both ends of the beam under the upward loads.

Unlike the possible reduction in width recommended for the outer sole (3), it appears fundamental, in view of the above observations, to widen the inner sole (4), on the one hand to increase its lateral stiffness and allow it to better resist lateral buckling (10), and on the other hand to reduce the stress applied to it by reducing the distance which separates it from the center of gravity or neutral fiber (9) of the fault profile .

If the inner sole (4) is wider than the outer sole (3), it is indeed clear that the center of gravity (14) is lowered from the corresponding profile towards the inner sole (4).

FIGS. 6 to 12 illustrate various applications of these principles to profiled purlins currently marketed, for example to a purlin (15) profiled in I (FIG. 6), to a purl (19) profiled in C (FIG. 10), to purlins (17, 20, 21) Z-shaped (Figures 8, 11 and 12), a breakdown (16) marketed under the brand "Pannerval" (Figure 7) and a breakdown (18) marketed under the brand "Propanne" (figure 9).

For all the purlins (15 to 21) represented in FIGS. 6 to 12, the insole (4) is of constant thickness and equal to that of the outsole (3) and is of a width continuously and appreciably greater than that of the outer sole (3), a construction which results in making the fault profile asymmetrical with respect to any plane parallel to the wall (2) to be supported.

Advantageously, the insole (4) of each of these types of profile is of a width continuously comprised between 1.2 and 2 times the width of the outsole (3), and it is preferably of a width continuously understood between 1.4 and 1.8 times the width of said outer sole.

Unlike the construction shown diagrammatically in FIGS. 4a and 4b, thanks to which the beam formed has on each of its two faces an alternation of wide flanges and narrow flanges, the invention allows to produce a beam whose inner sole (4) not stabilized by the wall (2) is continuously and notably wider than the stabilized outer sole (3). It is then the width of this insole (4) of any asymmetrical profile which will be able to be taken into account in the calculation of the performance indices of all the failures according to the invention.

Table I illustrates by the results that it communicates the advantages of implementing the invention.

In this table, the first column is reserved for the test number, the second column gives in millimeters the dimensions of the purlin concerned, namely successively its height, the width of its outsole (3), the width of its sole. inside (4) and the thickness of the profiled sheet to make the breakdown, the third column gives in cm² the section of the breakdown concerned and finally the fourth column gives in cm / Kg the moment of resistance in theoretical span Mr.

All the tests, 32 in number, were carried out on a "Propane" type failure (18) obtained by cold profiling of a steel sheet whose elastic limit, common to the 32 profiles tested, is 400 MegaPascals.

Tests No. 1 to 16 were carried out on a conventional propane purlin, symmetrical, that is to say with outer and inner flanges of the same width and the same thickness, while tests No. 17 to 32 were carried out on a Propanne type breakdown in accordance with the invention, asymmetrical, the insole of which is significantly greater in width than that of the outer sole.

For all tests N ° 1 to 32, the resistant moment Mr was calculated under the ascending loads of type B, that is to say oriented from the inside towards the outside of the building to be protected, by applying the method of SOKOL published in the journal CM N ° 1-1979, the covering elements (2) being tubs of corrugated sheet steel screwed in the hollow of the wave on the purlin support.

The values communicated in table I clearly show the advantages of the profiled purlin of the invention compared to the traditional purlin, the moment resisting at equal cross-sections, ie still at identical weight, being greater for the purlin according to the invention, and vice versa, at equal resistive moments, the tip of the invention being of smaller cross section, that is to say lighter, and consequently of lower price, than the traditional tip which corresponds to it for said value of the moment resistant.

For substantially identical sections, it is interesting to compare the tests 1 / 18-2 / 19-3 / 20-5 / 21-6 / 22-7 / 23-9 / 24-10 / 25-11 / 26-12 / 27-13 / 28-14 / 29-15 / 30-16 / 31.

The resistant moment Mr of the failure according to the invention tion, identified by a number between 17 and 32, is in fact greater than the resistant moment Mr of the traditional failure which corresponds to it, identified by a number between 1 and 16, with a value which is respectively: 17 , 3%; 14.2%; 13.3%; 18.5%; 15.6%; 15.0%; 19.1%; 16.7%; 16.5%; 15.8%; 31.7%; 26.6%; 26.2%; 24.4%.

From the above comparisons, it should also be observed that:
the improvement of the stabilizing effect of the asymmetrical fault profile in accordance with the invention compared to the traditional symmetrical fault profile is all the more remarkable the higher the fault concerned,
- for a breakdown of the same height, the improvement in the stabilizing effect is all the more important the smaller the thickness of the sheet.

It is also significant to compare the geometric characteristics of the asymmetrical purlins of the invention and of the traditional symmetrical purlins which, formed from a sheet of the same thickness, make it possible to obtain values of substantially identical resistance moment. It is in particular interesting to compare tests 4 / 20-8 / 23-13 / 24-15 / 26 and 16/27.

From these five comparisons, it follows that, at equal resistive moments, the section of the purlin according to the invention, and consequently the weight of this purlin, is less than the section and respectively the weight of the traditional purlin by: 6.1%; 6.4%; 7.1%; 6.3%; 6.5%.

The comparison between tests 1 and 17 is also particularly edifying. For values of substantially equal resistive moments, and the two purlins being produced from a sheet of the same thickness, it is remarkable to note that it suffices to design a purloin according to the invention whose outer sole has a width lowered from 60 to 50 millimeters, all other things being equal. This observation is proof of the non obviousness of the present invention since nothing is a priori simpler than reducing the width of one of the two flanges of a profile if, moreover, we know that the mechanical characteristics of this profile do not change.

The comparison between tests 15 and 32 is also particularly edifying. It is seen in fact that the failure of the invention corresponding to test 32 has substantially the same value of resistance moment Mr as the traditional failure corresponding to test 15 while being finer (2 millimeters instead of 2.5 millimeters) and of a section and as a result of a considerably reduced weight (8.576 cm² instead of 10.540 cm²).

Naturally, the invention is not limited to the mode TABLE I TEST NO. PROFILE DIMENSIONS IN MILLIMETERS PROFILE SECTION S IN cm2 MOMENT RESISTANT IN THEORETICAL TRAVEE Mr IN cm / Kg 01 130 x 60 x 60 x 1.5 4.972 36,323.78 02 130 x 60 x 60 x 2 6.591 56,771.62 03 130 x 60 x 60 x 2.5 8,191 78107.73 04 130 x 70 x 70 x 2.5 8.794 89,267.20 05 160 x 60 x 60 x 1.5 5.422 40,754.51 06 160 x 60 x 60 x 2 7.191 65,754.51 07 160 x 60 x 60 x 2.5 8,941 92,964.21 08 160 x 70 x 70 x 2.5 9.544 106,857.70 09 200 x 60 x 60 x 1.5 6.022 44,851.81 10 200 x 60 x 60 x 2 7.991 74,238.47 11 200 x 60 x 60 x 2.5 9,941 107,781.20 12 200 x 60 x 60 x 3 11,870 143,920.10 13 200 x 70 x 70 x 1.5 6.384 52,604.88 14 200 x 70 x 70 x 2 8.474 87501.09 15 200 x 70 x 70 x 2.5 10,540 124,740.30 16 200 x 70 x 70 x 3 12,600 165,437.50 17 130 x 50 x 60 x 1.5 4.780 36,470.12 18 130 x 50 x 70 x 1.5 4.961 42,538.37 19 130 x 50 x 70 x 2 6.451 63,462.26 20 130 x 50 x 70 x 2.5 8.385 90,621.06 21 160 x 50 x 70 x 1.5 5.411 48,217.81 22 160 x 50 x 70 x 2 7,051 74,534.16 23 160 x 50 x 70 x 2.5 9.135 109,263.00 24 200 x 50 x 70 x 1.5 6.011 53,298.28 25 200 x 50 x 70 x 2 7.851 85,083.47 26 200 x 50 x 70 x 2.5 10,140 128128.90 27 200 x 50 x 70 x 3 11,920 167404.80 28 200 x 50 x 90 x 1.5 6.373 69,186.77 29 200 x 50 x 90 x 2 8.334 108,906.20 30 200 x 50 x 90 x 2.5 10,740 160,444.80 31 200 x 50 x 90 x 3 12,640 206,481.10 32 200 x 50 x 100 x 2 8.576 120,370.10 of application no more than to the embodiments which have been described above and it is possible to conceive of various variants without departing from the scope of said invention. This is particularly the case with the relative arrangements of the two soles (3, 4). For each of the purlins (15, and 18 to 21) shown in FIGS. 6, and 9 to 12, the insole (4) is centered under the outsole (3), so that the longitudinal axes of symmetry of said soles, respectively (22) and (23), belong to a plane perpendicular to the two soles. For each of the purlins (16 and 17) shown in FIGS. 7 and 8, the core (5) is provided perpendicular to the two flanges (3, 4) so that, this time, the longitudinal axes of symmetry of said flanges, respectively ( 24) and (25), belong to a plane which forms with each of the two flanges an angle different from 90 °.

It is quite clear, however, and for non-limiting examples, that:
- for the purlin (16) marketed under the Pannerval brand, the insole (4) can be centered under the outsole (3) by a simple modification of the profile of the core (5) and / or of the profile of the ribs ( 26),
- conversely, and for example for the purlin (18) or for the purlin (19), the insole (4) can be offset relative to the outsole (3), to the right, taking as references the sections shown in Figures 9 and 10, so that the left longitudinal edge (27) of the outsole is located exactly in line with the left longitudinal edge (28) of the insole; in this case, the plane passing through the longitudinal axes of symmetry of the soles (3, 4) of the purlins (18, 19) will form with each of said soles an angle different from 90 °.

Claims (5)

1. Profiled metal failure intended to support an exterior wall of a building, such as a covering or cladding, said purlin being of the type comprising two flanges, respectively exterior (3) and interior (4), which are parallel and of equal thickness, and a core (5) which joins said two soles, the outer sole (3) against which the wall (2) to be supported is applied being additionally secured to this wall, for example by self-tapping screws (6), and the inner sole (4), in danger of buckling, resting on at least two supports (7), characterized in that the insole (4) has a width continuously between 1.2 and 2 times the width of the outsole ( 3) 2. Failure according to claim 1, characterized in that the inner sole (4) is of a width continuously between 1.4 and 1.8 times the width of the outer sole (3). 3. Failure according to any one of claims 1 and 2, characterized in that the longitudinal axes of symmetry (22, 23) of the soles, respectively exterior (3) and interior (4), belong to a plane perpendicular to said soles. 4. Failure according to any one of claims 1 and 2, characterized in that the longitudinal axes of symmetry (24, 25) of the soles, respectively outer (3) and inner (4), belong to a plane which forms with each of said soles an angle different from 90 °. 5. Failure according to any one of claims 1 to 4, characterized in that it is obtained by cold profiling.

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