A joist support for use in building and a building structure including such a support

Description

[0001] This invention relates to a joist support for use in building, and to a building structure including such a support.

[0002] Where the context allows, the expression "joist" includes all forms of structural timber element such as roof trusses for example as well as the timbers conventionally referred to as joists and intended to support floors and ceilings.

[0003] in the past, it was the practice to build joists directly into masonry as the walls of a building were being constructed but this is generally unacceptable today for various reasons. For example, the timber of which joists are made tends to rot, particularly where it projects into a relatively wet environment, for example into the cavity of a cavity wall. Secondly, a timber extending through a layer of masonry provides a fire bridge which may enable fire to penetrate through a wall. Thirdly, repair and alteration work is extremely difficult if not impossible where joists are built directly into masonry because it is necessary for a joist to be longer that the gap between a pair of existing walls into which it is to be inserted.

[0004] These difficulties and drawbacks have been overcome or reduced by the use of metal joist hangers. These have proved very satisfactory when used correctly in suitable applications. However, there are some applications for which conventional joist hangers are unsuitable. Use in these situations may be dangerous and is certainly unsatisfactory.

[0005] For example, there is increasing use of very lightweight thermally insulating building materials, particularly in the inner leaf of an external cavity wall. Such building materials are much softer than the more traditionally brick or breeze block, and there is a considerable danger that the lightweight block will crumble and the joist will become unsafe if a conventional joist hanger is used. This problem is caused by the fact that the conventional joist is approximately 50 millimetres wide and the conventional joist hanger has about the same width so that the load is very strongly concentrated on a 50 millimetre length of the front top edge of a relatively soft block.

[0006] An attempt to distribute the loading of the joist across the supporting structure away from its forward edge was made in our prior British Patent, number 2,027,477, describing a joist support in which the joist was secured in a channel section metal member, having an integral forwardly projecting part resting on the masonry. However, this proposed solution required a different size of joist support for each size of joist and lacked a positive lateral restraint for preventing sidewards movement of the joist support relative to the wall under, for example, exceptionally high wind loading of the building.

[0007] A proposal was also made in the publication "Hochbau Konstruktion" by H. Schmitt at Page 450, to support joists from internal partition walls using channel section metal members, bolted to the joists through the base of the channel, only the part of the channel projecting beyond the joist resting on the wall. This proposal is open to the same comments as our prior British Patent number 2,027,477.

[0008] It is an object of the present invention to provide a new or improved joist support which is capable of use with a supporting structure of soft lightweight blocks, by transmitting joist loads across the supporting structure from its forward edge to reduce the risk of that edge crumbling under load.

[0009] According to the invention we provide a joist support for use in securing a joist to a supporting structure such as a masonry wall, the joist support comprising a single sheet metal member having a fold extending completely across it to divide the member into a pair of generally planar, mutually perpendicular flanges the member further comprising:

[0010] a fixing portion, provided by one of said flanges, with fixing holes for fasteners to secure the joist support to a face of the joist,

[0011] a bearing portion, provided by the other of said flanges, which rests horizontally in use on the supporting structure to transmit the load of the joist to the supporting structure,

[0012] and means defining a location for an end of the joist so that it can be positioned wholly outside the bearing portion,

[0013] the fold in the sheet metal member forming a rigid spine extending in use along a horizontal edge of a vertical face of the joist and throughout at least the major part of the bearing por- tion to rigidify the bearing portion and to transmit the load of the joist across the supporting structure from its forward edge;

[0014] characterised in that the sheet metal member is of slightly elongate, generally rectangular form and the fold forming the rigid spine extends obliquely across the member from one corner to intersect the longer side of the elongate rectangle adjacent the opposite corner.

[0015] It has been proposed, in securing timber joists or trusses to other timber members, to use brackets including or consisting of a sheet metal member folded to form two right angled flanges, which are nailed to respective faces of the timbers.

[0016] For example, U.S. Patent number 2,751,644 of Pedersen shows a vertical face of a joist secured in a butt joint to a vertical face of a timber wall plate, using a right-angled bracket.

[0017] British Patent number 868,578 of Wallis shows timber connectors having two assym- metrically disposed flanges at right angles.

[0018] U.S. Patent number 4,003,179 of Gilb shows a hanger for timber-chorded roof trusses in which the timber chord is attached to a wooden structural member by means of metal brackets having three mutually perpendicular flanges.

[0019] However, in each case, the part of the bracket attached to the supporting structure is a plain unsupported flange. Allowing for the known tendency of such a flange to flex under loading, it is clear that these brackets would be unsuitable for use in the context of transmitting a joist load to a supporting structure of soft, lightweight blockwork. The flange would flex and exert the heaviest loading on the supporting structure at its extreme forward edge. This is perhaps acceptable if the supporting structure is of timber or hard and durable masonry but not if it is of soft, lightweight blockwork.

[0020] In the joist support of the present invention, loading from the joist is transmitted across the supporting structure from its forward edge because of the presence of the rigid spine extending throughout the joist support including its bearing portion. No concentration of loading occurs at the forward edge. Alongside the projecting rigid spine, the vertical flange por- tion in the masonry also provides lateral restraint.

[0021] The joist support may be further characterised in that, in addition to the bearing portion, said other flange also provides a support por- tion extending beneath the joist in use, and the width of said other flange is at a maximum in the region where the bearing portion and support portion meet.

[0022] The means defining a location for the end of the joist may be disposed in said one flange. They may comprise one or more tongues of metal pressed out of the plane of the flange or one or more apertures through which the end of the joist can be seen.

[0023] The bearing portion may have one or more keying formations and/or one or more fastener receiving apertures.

[0024] The invention also provides a building structure comprising a supporting structure such as a masonry wall; a joist; and a joist support as set out above, securing the joist to the supporting structure.

[0025] The invention will now be described in more detail by way of example only with reference to the accompanying drawings in which:-

FIGURE 1 is a perspective view of a joist support embodying the invention, showing the position of an end portion of a joist in chain dotted outline;

FIGURE 2 is a diagrammatic side elevation on a smaller scale, showing a joist positioned in a building structure using a pair of joist supports.

[0026] Referring to Figure 1 of the drawing the joist support will be seen to comprise a generally rectangular metal member 10 which has a single oblique fold 11, extending from one corner 12 across the member 10 to intersect an elongate edge 13 of the metal member adjacent the corner 14 opposite the first mentioned corner 12.

[0027] The metal member is therefore divided by the fold 11 into one flange 15 which is generally upright in use and another flange 16 which is generally horizontal in use.

[0028] The fold 11 can be regarded as a rigid spine extending somewhat diagonally across the metal member 10 and providing a considerable degree of rigidity. The two flanges 15 and 16 are disposed at right angles to each other and, in use, the joist 17 which is outlined in chain dotted lines is placed in abutment with the flanges 1 and 16. The position of the end of the joist is controlled by placing the end of the joist so that it can be seen through a joist locating aperture 18. Alternatively, a tongue or more than one tongue of metal can be pressed out of the member 10 to provide joist locating means equivalent to the aperture 18. The aperture 18 is shown provided on the one flange 15 but could alternatively be provided on the other flange 16.

[0029] It will be seen that the remainder of the metal member forms an extension 30 extending from the end of the joist.

[0030] The end portion of the joist is positioned so that its end face is located at the aperture 18 and it is then secured to the one flange 15 by suitable fastening means. In the embodiment shown, a number of nail holes 19 are provided, through which nails can be driven into the joist. Additionally, for alternative use, a pair of large diameter bolt holes 20 are also provided. All of these fixing holes are provided in a fixing por- tion of the one upright flange 15, this fixing por- tion lying to the right hand side of the chain- dotted line 21 which indicates the end of the joist.

[0031] It will be seen that the majority of the nail holes 19 are disposed well to the right of this line 21, so as to comply with the requirements of the relevant standard which requires that the structural fixings should be placed and spaced at such a distance from the end as to prevent splitting or similar degradation of the material. In the case of a timber joist, the main securing nails will be at least twenty times the nail diameter from the end for example. An additional nail hole 22 is provided somewhat closer to the line 21 for added stiffness by reducing the buckling length of the free edge 32 of the extension 30. Additionally, or alternatively, the free edge 32 of the extension 30 could be stiffened by one or more ribs for example.

[0032] The other flange 16 of the member 10 is disposed horizontally in use and includes a support portion 23 which is disposed beneath the end of the joist 17 in use. This may contribute to supporting and locating the joist although the joist is not secured to this support portion 23. A large opening 24 is provided in the support portion 23; to be used for securing, for example, plasterboard to the underside of _' the joist.

[0033] The other flange 16 also includes a bearing portion 25. This bears on the upper surface of a supporting sturcture 26 shown in dotted outline. The bearing portion has a larger aperture 27 which may be used as a mortar key to embed the bearing portion 25 in mortar used between adjacent courses of masonry. This keying is also assisted by virtue of the fact that a corner 28 of the member 10 is also positioned to the left hand side as shown of the line 21 which represents the position of the end of the joist and also of the edge of the supporting structure 26; thus, the corner 28 is embedded in the mortar if mortar is provided.

[0034] Additionally, a pair of nail holes 29 are - provided, to enable the joist support to be used on a supporting structure of timber, to which it will then be nailed using these holes 29. Alternatively, a bolt can be inserted through the aperture 27 or other purpose designed fixing means can be provided.

[0035] If reference is now made to Figure 2 of the drawings it will be seen that, in use, a joist support as shown in detail in Figure 1 is secured to each end of the joist 17 and effectively forms an extension 30 of the joist projecting from the end of the joist. This extension is the part of the joist support to the left hand side of the line 21 in Figure 1.

[0036] When the joist has been thus extended by means of a pair of joist supports, these extensions 30 can be rested on the previously provided supporting structures 26. For example, where one is considering the building of a house using masonry walls, the walls will be built up to the level at which the joists are to be provided and a pair of joist supports according to the invention will then be secured, for example by nailing, to the end portions of the joist 17. The extensions 30 at each end of the joist can then be rested on the masonry of the walls as shown in Figure 2. It will be seen that the structure is fully stable without any additional courses of masonry being built above the joist support at that stage.

[0037] In contrast, the correct use of a conventional joist hanger requires that it is held in place by several courses of masonry above the level of the hanger before the joist can be supported. In practice, this requirement is frequently ignored and it is not unknown for the joists to be inserted with no masonry provided above the conventional hangers and for the bricks or blocks to be used in building the wall above to be stacked on boarding laid across the joists which those masonry elements ought to be anchoring in position. This frequently results in distortion of the conventional type of joist hanger which can result in its subsequently pulling out of the masonry and can also result in the masonry being excessively stressed at the edge adjacent the joist, causing damage to the masonry.

[0038] With the joist support according to the invention, this problem is completely eliminated because the structural strength comes from the rigid spine afforded by the fold 11 and not from any anchoring effect due to masonry disposed above the bearing portion 25.

[0039] This feature of the joist support makes it adaptable for use in securing roof trusses in place to the top of a wall. In this case, there would normally be no masonry above the level of the base of the roof truss which would make the use of a.conventional joist hanger impracticable.

[0040] Returning now to Figure 1 of the drawings it will be seen that the width of the bearing por- tion 25 in the region of the line 21 at the end of the joist is at its greatest, and that the width then tapers away in the form of a triangle but with the fold 11 affording a rigid spine throughout the distance from the line 21 to the corner 12.

[0041] When the joist support is placed in position on a partly built wall formed of lightweight thermal insulating blocks, it will be appreciated that the load of the joist is spread across the width of the bearing portion in the region of the line 21 denoting the end of the joist, which coincides roughly with the edge of the lightweight blocks forming the supporting structure 26. The rigidity of the spine formed by the fold 11, however, also serves to distribute the joist load across the thickness of the lightweight block. In this way, the load is not concentrated on the forward edge of the block, which might cause that forward edge to crumble, but is spread over a large, generally triangular region of the top surface of the block. It has been established empirically that, using a bearing surface which measures approximately 80 millimetres along the line 21 by 70 millimetres along the fold 11, it is possible to load the joist so strongly that distortion of the metal of the joist support will occur before failure of lightweight blocks with a crushing strength as low as 3.5 N/m for example.

[0042] The embodiment of joist support shown in the drawings and described above has considerable advantages compared with a conventional welded joist hanger. Firstly, it can be manufactured quite simply by stamping and pressing from sheet metal which can be galvanised to any desired thickness as it does not need to be welded. The sheet metal member 10 is generally rectangular, being slightly skewed as shown to permit the corner 28 to lie inboard of the line 21 and of the edge of the supporting structure 26. This means that large numbers of the metal members can be cut without substantial wastage from a single sheet.

[0043] As referred to above, it is unnecessary to have any masonry above the joist support to make it fully effective. It can therefore by used for fixing roof joists and roof trusses for example including trusses used for monopitch and part- profile roofs. It is not necessary for there to be a mortar board to hold the joist support in position. If mortar is used, however, the bond is extremely good and, compared with a conventional welded hanger, it will be appreciated that there is a much reduced tendency for the mortar bond to be broken. The forces acting on the bearing portion 25 of the joist support, in use, are largely downward compressive forces whereas, with a conventional joist hanger, the forces tending to pull the bearing portion out of downward compressive forces and lateral shear forces tending to pull the bearing por-tion out of the mortar joint. This is because the joist is. disposed below the forward edge of the bearing portion of a conventional joist hanger.

[0044] The joist support of the present invention is positively secured at the side of the joist by means of the fixings passing through holes 19 or 20. There is an upright 31 provided by the one flange 15 of the extension 30. This upright 31 is disposed between adjacent masonry elements of the wall structure as it is built up. In combination, these two features permit the joist support to give some lateral restraint to the joist, in addition to merely transferring the load from the joist to the wall.

[0045] Since the joist is located only against the two flanges 15 and 16, it will be appreciated that all sizes of joist can be accommodated with one or two suitable sizes of joist support and also that, provided adequate fixing and bearing areas are provided, structures such as roof trusses and so on can also be accomodated. This means that a supplier or a builder does not need to hold a large range of stocks to cover all requirements. It will be seen that the joist supports in the form shown are capable of being stacked one on another in a very minimal space and can readily be packed for transport and storage.

[0046] It will be appreciated that various modifications can be made to the shape of the joist support and to the fixing arangements. For example, instead of providing nail holes and bolt holes 19 and 20 on the fixing portion of the one flange 15, this could be provided with punched- out tongues forming a nail plate so that the joist could be driven into position using a hammer or press. In this way, roof trusses for example could be provided with supports of the general type shown which are fitted in the factory before the roof trusses are delivered to a building site.

[0047] Although the flanges are generally planar, they could be ribbed or otherwise profiled for stiffness or to improve keying or friction.

[0048] It is intended the joist support shown should be provided in left-hand and right-hand forms. If these are used alternately, with the joist disposed at conventional centres of 400 millimetres, the upright 31 will be spaced correctly to occur in the interstices between building elements of a course of masonry in alternate bays.

[0049] If it is found, in use, that the positioning of the joist supports does not agree with the positioning of the masonry elements, a masonry saw can be used to slot the masonry elements to accommodate the upright 31. If it is desired to use the joist support in renovation of existing buildings, a masonry saw can again be used to produce a pair of perpendicularly disposed slots into which the joist support can be slid. It will be appreciated that no mortar is required to secure the joist support in position so that renovation work is much more satisfactory than it would be using a conventional joist hanger which requires a mortar bond to provide edge bearing and hold it securely in position.

Claims

1. A joist support for use in securing a joist to a supporting structure such as a masonry wall, the joist support comprising a single sheet metal member (10) having a fold (11) extending completely across it to divide the member (10) into a pair of generally planar, mutually perpendicular flanges (15, 16); the member (10) further comprising:

a fixing portion, provided by one of said flanges (15), with fixing holes (19, 20) for fasteners to secure the joist support to a face of the joist (17);

a bearing portion (25), provided by the other of said flanges (16), which rests horizontally in use on the supporting structure (26) to transmit the load of the joist (17) to the supporting structure (26);

and means (18) defining a location for an end of the joist (17) so that it can be positioned wholly outside the bearing portion (25);

the fold in the sheet metal member forming a rigid spine extending in use along a horizontal edge of a vertical face of the joist (17) and throughout at least the major part of the bearing portion (25) to rigidify the bearing portion (25) and to transmit the load of the joist (17) across the supporting structure (26) from its forward edge;

characterised in that the sheet metal member (10) is of slightly elongate, generally rectangular form and the fold (11) forming the rigid spine extends obliquely across the member from one corner (12) to intersect the longer side (13) of the elongate rectangle adjacent the opposite corner (14).

2. A joist support according to claim 1 further characterised in that, in addition to the bearing portion (25), said other flange (16) also provides a support portion (23) extending beneath the joist (17) in use, and the width of said other flange (16) is at a maximum in the region (21) where the bearing portion (25) and support portion (23) meet.

3. A joist support according to any preceding claim and further characterised in that the means (18) defining a location for the end of the joist (17) are disposed in said one flange (15).

4. A joist support according to any preceding claim and further characterised in that the means defining a location for the end of the joist (17) comprise one or more tongues of metal pressed out of the plane of the flange (15, 16).

5. A joist support according to any of claims 1 to 4 further characterised in that means (17) defining a location for the end of the joist (17) comprise one or more apertures (18) through which the end of the joist (17) can be seen.

6. A joist support according to any preceding claim and further characterised in that fastener receiving apertures (29) are provided in the bearing portion (25).

7. A joist support according to any one of claims 1 to 6 further characterised in that one or more keying formations (27) are provided on the bearing portion (25).

8. A building structure characterised in that it comprises a supporting structure (26) such as a masonry wall; a joist (17); and a joist support (10) according to any one of the preceding claims, securing the joist (17) to the supporting structure.

Revendications

1. Support de poutre apte à être utilisé pour fixer une poutre à une structure porteuse telle qu'un mur de maçonnerie, ce support comprenant une pièce unique en tôle (10) qui présente un pli (11) la traversant sur toute son étendue pour diviser la pièce (10) en deux ailes (15, 16) perpendiculaires l'une par rapport à l'autre de forme générale plane, la pièce (10) comprenant en outre:

une zone de fixation sur l'une des ailes (15), qui présente des trous (19, 20) pour permettre à des organes de fixation de fixer le support à l'une des faces de la poutre (17);

une zone d'appui (25) sur l'autre aile (16), qui repose horizontalement en cours d'utilisation sur la structure porteuse (26) pour transmettre la charge de la poutre (17) à la structure porteuse (26);

et des moyens (18) définissant une position pour l'une des extrémités de la poutre (17) afin que cette extrémité puisse être située entièrement en-dehors de la zone d'appui (25);

le pli dans la pièce en tôle formant une arête rigide qui s'étend en cours d'utilisation le long d'un bord horizontal de l'une des faces verticales de la poutre (17) et sur au moins la majeure partie de la zone d'appui (25) pour rigidifier la zone d'appui (25) et transmettre la charge de la poutre (17) sur une surface de la structure porteuse (26) s'étendant au-delà de son bord avant;

caractérisé en ce que la pièce (10) en tôle a une forme générale rectangulaire légèrement oblongue et le pli (11) formant l'arête rigide traverse la pièce obliquement depuis un de ses angles (12) pour venir couper le côté le plus long (13) du rectangle oblong au voisinage de l'angle opposé (14).

2. Support de poutre selon la revendication 1, caractérisé en ce que, en plus de la zone d'appui (25), l'autre aile (16) présente aussi une zone de soutien (23) qui s'étend en cours d'utilisation sous la poutre (17), et que la largeur de l'autre aile (16) est maximale dans la région (21) où la zone d'appui (25) et la zone de soutien (23) se rencontrent.

3. Support de poutre selon l'une quelconque des revendications précédentes, caractérisé en ce que les moyens (18) définissant une position pour l'une des extrémités de la poutre (17) comportent une ou plusieurs saillies métalliques estampées hors du plan de l'aile (15, 16).

4. Support de poutre selon l'une quelconque des revendications précédentes, caractérisé en ce que les moyens (18) définissant une position pour l'une des extrémités de la poutre (17) comportent une ou plusieurs saillies métalliques estampées hors du plan de l'aile (15,16).

5. Support de poutre selon l'une quelconque des revendications 1 à 4, caractérisé en ce que les moyens définissant une position pour l'une des extrémités de la poutre (17) comportent une ou plusieurs ouvertures (18) à travers lesquelles on peut voir l'extrémité de la poutre (17).

6. Support de poutre selon l'une quelconque des revendications précédentes, caractérisé en ce que des ouvertures (29) destinées à recevoir des organes de fixation zone ménagées dans la zone d'appui (25).

7. Support de poutre selon l'une quelconque des revendications 1 à 6, caractérisé en ce qu'une ou plusieurs entailles d'adent (27) sont ménagées dans la zone d'appui (25).

8. Structure de bâtiment, caractérisé en ce qu'elle comprend une structure porteuse (26) telle qu'un mur de maçonnerie; une poutre (17); et un support de poutre (10) selon l'une quelconque des revendications précédentes, assujettissant la poutre (17) à la structure porteuse.

Ansprüche

1. Stütze für Tragbalken zum Befestigen eines Tragbalkens an einem Tragwerk wie etwa einem tragenden Mauerwerk, wobei die Stütze ein einzelnes Metallbelechteil (10) mit einer Falte (11) ist, die sich vollständig über das Metallblechteil erstreckt und es in zwei im wesentlichen ebene, zueinander parallele Flansche (15, 16) unterteilt, wobei das Metallblechteil (10) ferner aufweist:

einen Befestigungsabschnitt, der durch einen der Flansche (15) mit Befestigungslöchern (19, 20) für Befestigungselemente zum Sichern der Tragbalkenstütze an einer Fläche des Tragbalkens (17) versehen ist;

einen tragenden Abschnitt (25), der durch den anderen Flansch (16) gebildet ist, im Betrieb horizontal auf dem Tragwerk (26) aufliegt und das Gewicht des Tragbalkens (17) auf das Tragwerk (26) überträgt;

und Mittel (18), die eine Position für ein Ende des Tragbalkens (18) definieren, so daß dieser vollständig außerhalb des tragenden Abschnitts (25) positionierbar ist;

wobei die Falte in dem Metallblechteil einen festen Rücken bildet, der sich im Betrieb längs einem horizontalen Rand einen vertikalen Fläche des Tragbalkens (17) und über wenigstens des größten Teil des tragenden Abschnitts (25) erstreckt, den tragenden Abschnitt (25) versteift und das Gewicht des Tragbalkens (17) über das Tragwerk (26) von seiner Vorderkante überträgt; dadurch gekennzeichnet, daß das Metallblechteil (10) etwas längliche, im wesentlichen rechteckige Form hat und die den steifen Rücken bildende Falte (11) sich von einer Ecke (12) ausgehend schräg über das Metallblechteil erstreckt und die längere Seite (13) des langen Rechtecks nahe der entgegengesetzten Ecke (14) schneidet.

2. Stütze für Tragbalken nach Anspruch 1, dadurch gekennzeichnet, daß zusätzlich zu dem tragenden Abschnitt (25) der zweite Flansch (16) ebenfalls einen Stützabschnitt (23) bildet, der sich im Betrieb unter den Tragbalken (17) erstreckt, wobei die Breite des zweiten Flanschs (16) in dem Bereich (21), in dem der tragende Abschnitt (25) und der Stützabschnitt (23) aufeinandertreffen, am größten ist.

3. Stütze für Tragbalken nach einem der vorhergehenden Ansprüche, dadurch gekennzeichnet, daß die eine Lage für das Ende des Tragbalkens (17) definierenden Mittel (18) in dem einen Flansch (15) angeordnet sind.

4. Stütze für Tragbalken nach einem der vorhergehenden Ansprüche, dadurch gekennzeichnet, daß die eine Lage für das Ende des Tragbalkens (17) definierenden Mittel eine oder mehrere Metallzungen aufweisen, die aus der Ebene des Flanschs (15, 16) herausgedrückt sind.

5. Stütze für Tragbalken nach einem der Ansprüche 1-4, dadurch gekennzeichnet, daß die eine Lage für das Ende des Tragbalkens (17) definierenden Mittel eine oder mehrere Offnungen (18) umfassen, durch die das Ende des Tragbalkens (17) sichtbar ist.

6. Stütze für Tragbalken nach einem der vorhergehenden Ansprüche, dadurch gekennzeichnet, daß in dem tragenden Abschnitt (25) Öffnungen (29) zur Aufnahme von Befestigungselementen ausgebildet sind.

7. Stütze für Tragbalken nach einem der Ansprüche 1-6, dadurch gekennzeichnet, daß an dem tragenden Abschnitt (25) eine oder mehrere Hohlausformungen ausgebildet sind.

8. Baustruktur, dadurch gekennzeichnet, daß sie ein Tragwerk (26) wie etwa tragendes Mauerwerk, einen Tragbalken (17) sowie eine Tragbalkenstütze (10) nach einem der vorhergehenden Ansprüche umfaßt, die den Tragbalken (17) an dem Tragwerk sichert.

Drawing