Frontal butt connection between two roof slab elements of a flat roof and corresponding roof slab element

Abstract

The invention relates a frontal butt connection between two roof slab elements of a flat roof and to a corresponding roof slab element (1) which comprises undercuts, grooves or pockets (8, 9) integrated into its profile walls (6, 7). In this area the pockets of at least one roof slab element are substantially recessed in the form of slots (11) or a jog (15), and the apex of the slab can be removed. The slabs can be nested into one another or stacked without the pockets or grooves mutually impeding one another. Especially when the slots or the jog is configured in such a way that they almost halve the pockets next to the upper chord, the remaining pockets enclose the pockets of the subjacent slab. The top slab, in the slot area, is elastic to such an extent that it almost engages into the upper chord of the lower slab. The roof slab elements can be fastened, for example, in the area of the overlapping upper chords or with their slab surfaces resting on the purlin either with one another and/or on the purlin. The invention allows a gap-free butt connection of the roof slab elements despite their projecting pockets.

Description

TECHNICAL FIELD OF THE INVENTION

The invention relates to a front-end connection between two roofing sheet elements for a flat roof and the corresponding suitable roofing sheet element that in its profiled walls comprises molded undercuts, grooves, or pockets, and the roofing sheet elements to be abutted have the same profile cross-section with the same profile size.

STATE OF THE ART

Roofing sheet elements mostly have the form of sheets with trapezoidal corrugation and with uniformly alternating protruding and receding creases that rest on the purlins of a flat roof, and are usually lined with an insulating material and sealed with plastic or bitumen sheeting. The insulating and sealing materials are mechanically attached. This process is done with screws and large-surface load-distributing disks or a plastic-and-screw combination. A plastic-and-screw combination consists of a hollow shaft made of plastic, which retains a sunk-in screw. The screw has a drilling tip that cuts into the roofing sheet element. In the case of conventional roofing sheet elements, the screws penetrate the roofing sheet in the area of the sheet's top cord and are visible from the inner side of the building, which can be disadvantageous not only for visual reasons, but also because this design is prone to corrosion. In order to eliminate this flaw, the German patent specification DE 199 43 661 A1 describes an attachment system in which the roofing sheet element comprises in its sides molded pockets or grooves. The pockets of two parallel adjacent sheet sides form a back-taper pair, which serves as a retaining means for the clamping lugs imbedded in the receding crease of the roofing sheet element. The clamping lugs form a drillable working surface for attachment screws. The drilling bits penetrating the clamping lugs protrude into the receding creases of the roofing sheet elements and are no longer visible from the inner side of the building. The roofing sheet elements of this form can no longer be installed so as to overlap in the butt area, i.e., in transversal butt, because the pockets or grooves molded in the sheet wall do not allow it. Such butt connections are created, e.g., with transition sheets.

The French patent FR 1 491 552 describes a sheet with trapezoidal corrugation, which—in order to avoid drilling holes during the installation—are equipped with dents, in which attachments can be anchored. To allow assembly of the elements in a longitudinal direction, one end of the sheet with trapezoidal corrugation comprises a retaining profile, which—by shaping the relevant end—is designed in such a manner that the flat, slightly expanding sections fit precisely against the flat sections of the adjacent element. The resulting butt joint is technically demanding and costly, because the butt joint requires a deformation of the sheet elements and must be mechanically secured. However, this circumstance eliminates the original advantage of a screw-free connection.

In addition, the specific protrusion of the sheet elements does not allow for free turning of the elements; rather, they must always be used in one particular direction of installation. This problem results in a relatively high percentage of cuttings and thus in increased consumption of the sheet material.

This invention proposes to solve the underlying technical problem by means of a simple and safe butt connection for roofing sheet elements that have molded undercuts, grooves, or pockets in their profiled walls. Furthermore, the task of this invention is to create a roofing sheet element suitable for such a butt joint, wherein the roofing sheet elements to be abutted have the same profile cross-section with the same profile size.

REPRESENTATION OF THE INVENTION

To resolve the aforementioned technical problem, the invention proposes to overlap the roofing sheet elements in the area of the abutting surface and to arrange (in at least one of the roofing sheet elements or in the overlapping area) undercuts and pockets.

The particular advantages of this invention have to do with the roofing sheet elements, which can overlap in the abutting surface in the conventional manner. This possibility not only brings a static benefit, but it is also advantageous for the installation technology. The sheets can both be inserted into each other and be shifted afterwards, and simply laid on each other in order to create the abutting surface. In spite of the proprietary profile cross-section, no special design needs to be used in the transversal abutting area. Thus, the invention allows one to build a transversal butt joint with constructional overlap in the direction of tension in the proven manner, which complies with the conditions of [the German industrial standard] DIN 18807, wherein this invention, for the first time, creates an abutting surface with modified sheets with pockets.

From the point of view of statics, the transversal butt serves only for the transmission of transversal and/or support forces. Transmission of the bending moment is not intended. A special embodiment of this invention ensures that the roofing sheet of transversally abutting design can be formed and dimensioned as and end support (abuttal) of a conventional non-slotted or non-notched sheet. Sheets designed according to this invention that are attached to the purlin (binding rafter) will provide additional protection against suction forces created by the wind.

An advantageous embodiment of the invention comprises roofing sheet elements that will lie flatly on each other, at least in the area of the bottom cord. The pockets are designed in such a manner that they do not stick out and thus do not create any gaps in the overlapping area. If instead of notching, where the top cord of the sheet is also removed, a double-sided slotting is selected in order to remove the pockets, then the top cords also lie on the adjacent surface. The sheets can be inserted into one another or laid one on top of the other, without the pockets or grooves colliding with each other. Especially if, for example, the slots are designed in such a manner that they approximately halve the pockets close to the top cord, then the remaining full pockets envelope the pockets of the sheet lying below. The upper sheet is elastic in the slot area to such an extent that it slides into the top cord of the lower sheet. The roofing sheet elements can be attached, e.g., in the area of the overlapping top cords, either to each other or to the binding rafter. In a preferred design, the slots or the notches extend from the front edge in the longitudinal direction of the roofing sheet element. With this design, the first sheet of the sheet band to be created and installed does not need to be modified. Each following sheet requires, on its front end, the fabrication of, e.g., the slots according to this invention. The top cord located above the slot is supported by the top cord of the sheet lying underneath.

An advantageous embodiment of this invention comprises a notch in the roofing sheet element in the area of its undercuts, pockets, and grooves. Since the top cord of the roofing sheet is not exposed to any static load, instead of the performed slotting it can be completely notched or removed. Such slotting or notching can be optionally performed on the upper side of the bottom side of the sheet.

Furthermore, the invention provides a roofing sheet element for a butt joint according to claim 1. Especially with an almost trapezoidal profile cross-section (wherein its profiled wall sides comprise molded undercuts, lugs, or pockets), the roofing sheet elements to be abutted will have the same profile cross-section with the same profile size, and which are characterized in that the roofing sheet elements comprise—on both their sides in the area of the undercuts, lugs, and pockets—of slots or a notched area that cut out the undercuts, lugs, or pockets to a large degree and that extend from the front edge in the longitudinal direction of the roofing sheet element parallel to the sheet cord.

An advantageous embodiment of the invention comprises a notch in the roofing sheet element in the area of its undercuts, lugs, or pockets so that the undercuts, lugs, or pockets including the sheet cord are mostly cut out and the notch runs from the front edge in the longitudinal direction of the sheet. It is this design (with remaining or fully removed sheet cord that enables very flexible handling of the sheets in a real-life scenario. The sheets to be abutted can be pressed into each other, or inserted into each other so that any required adjustment in length is also possible.

Other advantages and advantageous embodiments of the invention will become clear from the following description, drawings and claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a cross-section of the roofing sheet element according to this invention

FIG. 2 shows the butt joint according to this invention in a side view

FIG. 3 shows a perspective view of the roofing sheet element according to this invention

FIG. 4 shows the front view of a test body

FIG. 5 shows the side view of the test body from FIG. 4

FIG. 6 shows a system outline of a test arrangement

FIG. 7 shows the bedding of the test objects in the cutout end

FIG. 8 shows a force displacement diagram of the examined sections of sheets with trapezoidal corrugation (machine path s)

FIG. 9 shows a force displacement diagram of the examined sections of sheets with trapezoidal corrugation (end abuttal displacement w)

FIG. 10 shows a summary of statistical evaluation of the ultimate loads achieved.

FIGS. 11-13 indicate important dimensions of the tested sheets with trapezoidal corrugation

FIG. 14 shows a schematic representation of the overlapping length in the tension direction

FIG. 15 shows a side view that defines the length of the slotting

FIG. 16 shows a front view that defines the height of the slotting

FIG. 17 shows a table with the minimum widths of the abuttal zone

FIG. 18 shows a schematic representation of the arrangement of additional attachment means

INVENTION DESIGN EXAMPLE

The steel sheet with trapezoidal corrugation E 160 manufactured by the company Hoesch is used as the roofing sheet element 1. This steel sheet with trapezoidal corrugation is subsequently cold-formed in the top cord in such a manner that it provides the option of attaching to the trapezoidal sheet interlocking elements in a screw-free connection.

The roofing sheet element denoted with 1 consists of parallel trapezoidal protruding and receding creases 3 and 4. In FIG. 1, the next receding crease 4 following the protruding crease 3 is only indirectly indicated. The roofing sheet elements 1 and 2 are abutted with overlapping areas that are denoted as 5. The roofing sheet elements 1, 2 comprise pockets 8, 9, which are subsequently formed in their walls 6, 7. Due to this special form, so far it has not been possible to perform a conventional transversal abuttal with constructive overlapping in the stress direction in accordance with DIN 18807, Part 3, Paragraph 4.6.1. Therefore, according to this invention the roofing sheet element 1 comprises a slot 11 in each of its walls 6, 7, which slot extends from the front edge 12 in the longitudinal direction of the sheet and which approximately halves the pockets 8, 9 so that they can be tilted over the pockets 8′, 9′ lying above them. In the overlapping zone, the roofing sheet element 1 envelops the roofing sheet element 2 lying underneath, and both sheets fit closely together with their bottom cords 13, 14 and/or their top cords 16, 17.

In order to prove the functionality of this invention, load tests were performed on sections of sheet with trapezoidal corrugation connected at the butt joint. These tests will now be explained using the subsequent figures. We used 2.5-meter long sections of modified steel sheet with a trapezoidal corrugation profile, in which—as shown in FIGS. 4 and 5—at one end the top cord was cut out at the length of about 25 cm and at the depth of about 4 cm. The resultant notch is denoted with the reference 15. The tests were performed in accordance with DIN 18807 as the so-called end-support tests under suction load. The required test design that was used is essentially illustrated in FIGS. 6 and 7. This design complies in all essential details with the conditions of the relevant industrial standards. The load was exerted by a servo-hydraulically controlled 63-kN single test cylinder. The tests were performed in the displacement-controlled manner. The control parameter was the displacement speed of the test cylinder piston. The constant displacement speed was 0.08 mm/sec. The measured parameters were the piston displacement (machine path S) and the resulting force F. Electrical signals were recorded using a PC, then further processed and directly plotted as force displacement curves.

FIG. 8 graphically illustrates the force displacement diagrams that were determined in four stress tests. FIG. 9 shows the results of displacement measurements on the end support. The table in FIG. 10 contains a summary of the statistical evaluation of the ultimate loads achieved. FIGS. 11-13 contain the most important dimensions of the tested sheets with trapezoidal corrugation. The assessment of the invention in connection with the performed stress tests went so far as to design a test focusing on total failure. This test had to be stopped only after all the screws were removed. Moreover, the tests demonstrated that the reference values indicated for the constructive overlapping length I₀ in the stress direction by DIN 18807 are decisive. Reference values of 50 to 150 mm apply to the overlapping length for a sub-shell made of sheets with trapezoidal corrugation and with the upper side sealing the roof. The length of the notch or slotting I₅ (FIG. 15) should correspond with the reference values for the overlapping length with an additional extension that takes into account the extent of the possible assembly gaps (FIG. 14) that are due to the necessary tolerance in installation. From the point of view of statics, the length of the slotting 15 (FIG. 15) and thus also of the alternative notch, i.e., a complete removal of the top cord, is not relevant. As shown in FIG. 16, the slotting should be restricted to the zone of the pockets. The bearing surface widths b_A of the elements according to the invention in the zone of the transversal abuttal design (according to FIG. 14) comply with the minimum bearing surface widths of the end supports as per DIN 18807, Part 3, Paragraph 4.2.1., to the entirety of which we herewith refer. In slotted or notched sheets with trapezoidal corrugation, due to the cross-section weakening, the minimum bearing surface widths b_A2 must be complied with from the end of the slot or the notch along the entire un-weakened zone. The minimum bearing surface width depends on the course of the installation. The underlying non-slotted or non-notched sheet with trapezoidal corrugation is not usually attached to the overlying sheet immediately after the laying. The overlying slotted or notched sheet with trapezoidal corrugation can be attached immediately after the laying. FIG. 17 indicates the recommended minimum surface widths for the sheet with trapezoidal corrugation according to the invention recommended by DIN 18807. As for the connection means, relevant industrial standards or local government parameters prepared by the German Institute for Construction Technology apply together with the provisions of DIN 18807, Part 3. According to DIN 18807, Part 3, the minimum distance of the means of connection from the transversal edge of the sheet with trapezoidal corrugation is:
e≧20mm, e≧2×d with d=hole diameter.

Due to the cross-section weakening that can result in the case of high suction stress, the connection of the slotted or notched sheet and the underlying construction should be as close to the end of the slotting or the notch as possible. Experimental verification has been performed with the following distance of the connection means from the end of the slotting:
e+s≦60 mm
As shown in FIG. 18, if for design reasons this distance cannot be adhered to, an additional attachment element should be arranged in the unweakened zone of the slotted or notched sheet with trapezoidal corrugation. From the point of view of statics, arrangement of more connection elements is not necessary. However, additional construction attachments such as the attachment of the remaining top cord to the underlying trapezoidal sheet in the area of the slotting are possible.

All the features that have been indicated in the claims, the description, and in the drawings are essential for the invention on its own and also in connection with other features. Front-end butt connection between two roofing sheet elements for a flat roof and the corresponding suitable roofing sheet element

Claims

1. Butt joint between two roofing sheet elements that comprise undercuts, lugs, or pockets formed in their profile walls, comprising the roofing sheet elements to be abutted, the roofing sheet elements have the same profile cross-section with the same profile size, the roofing sheet elements that overlap each other in the abuttal zone and the undercuts, lugs, or pockets of at least one of the roofing sheet elements are at least removed or cut out in the overlapping zone.

2. Butt joint according to claim 1, wherein the roofing sheet elements lie one on another, at least in the zone of the bottom cords.

3. Butt joint according to claim 1, wherein the undercuts, lugs, or pockets are at least partially removed by slots arranged in their area.

4. Butt joint according to claim 1, wherein the undercuts, lugs, or pockets are at least partially removed by a profile notch.

5. Roofing sheet element for a butt joint according to claim 1, comprising undercuts, lugs, or pockets formed in their profile walls, wherein the roofing sheet elements to be abutted have the same profile cross-section with the same profile size, and on both sides in the zone of the undercuts, lugs, or pockets, the roofing sheet element comprises slots or a notch, which remove the undercuts, lugs, or pockets to a large extent, and extend from the front edge in the longitudinal direction of the roofing sheet element parallel to the sheet cord.

6. Roofing sheet element according to claim 5, wherein, in the area of the undercuts, lugs or pockets, the roofing sheet element is cut out, including the sheet cord, so that the undercuts, lugs, or pockets are removed to a large extent, and the cut-out extends from the front edge in the longitudinal direction of the roofing sheet element parallel to the original sheet cord.

7. Butt joint according to claim 2, wherein the undercuts, lugs, or pockets are at least partially removed by slots arranged in their area.

8. Butt joint according to claim 2, wherein the undercuts, lugs, or pockets are at least partially removed by a profile notch.

9. Butt joint according to claim 3, wherein the undercuts, lugs, or pockets are at least partially removed by a profile notch.

10. Butt joint according to claim 7, wherein the undercuts, lugs, or pockets are at least partially removed by a profile notch.

11. The roofing sheet element of claim 5, wherein the roofing sheet element has an almost trapezoidal profile cross-section.