GB2146090A - An intersection joint for bar elements - Google Patents

Abstract

In intersection joints for a framework of bar elements (1, 2, 3), the bar elements are clamped to connector bodies (4) which each have a plurality of threaded bores (5) defining three-dimensional and/or planar angles to one another, into each of which a headed screw (6) can be screwed, the head of which screw (6) abuts axially against a shoulder face of the bar element which faces away from the connector body (4). Shoulders (15) are provided on the connector body (4) against which bar elements (1, 2) abut in the direction of the deflection of the bar elements caused by loading. <IMAGE>

Description

SPECIFICATION An intersection joint for a framework of bar elements This invention relates to an intersection joint for a framework of bar elements, of the kind referred to in the preamble of claim 1 and as described and published in DE-PS 31 27 243.

Hitherto, when mounting a roof on known frameworks, vertically directed supports have been fixed to intersections of connector bodies, on which are arranged the purlins carrying the roof, in order to transmit the roof load to the intersections.

However, this does not ensure that turning moments, for example due to wind load, are transmitted via the purlin supports to the connector bodies, which moments exert additional forces on the intersection joints and thereby significantly weaken the joints, so that the intersection joints have to be designed much larger and more rigid than would be necessary for bearing the vertically acting roof load.

Further, the purlin supports and the purlins significantly increase the cost of a roof structure.

A main object of the invention is to improve an intersection joint of this kind, to provide simply and without substantial additional expense, far greater rigidity of the intersection joints and a more economical roof structure.

According to the invention there is provided an intersection joint for a framework of bar elements, especially for those of the upper chord of a framework, which are clamped to connector bodies, and which each have a plurality of threaded bores defining three-dimensional and/or planar angles to one another, into each of which a headed screw can be screwed, the shank of which screw matches and penetrates a bore in a bar element directed in the same direction as the threaded bore, and the head of which screw abuts axially against a shoulder face of the bar element facing away from the connector body so that the bar element is directly clamped to the connector body, characterised in that shoulders are provided on the connector bodies against which the bar elements abut in the direction of deflection of the bar element caused by loading.

These measures allow a roof, for example a roof of corrugated sheets, to be arranged and secured directly on the upper chords of the framework, without the purlin supports and purlins hitherto necessary, so that the roof is now effective as a continuous load on the bar elements constituting the upper chords. This continuous load does lead to deflection loading of the bar elements, but this deflection loading no longer, as previously, has to be transmitted exclusively via the fixing screws to the connector bodies, so that the fixing screws which are subjected to tension loadings, are not subjected to significant shear and bending forces. Attempts to avoid the effects of shear and bending forces have been made previously by directing the roof load to the intersection via the purlins and purlin supports.

These additional loadings, which act in the direction of the roof load, are now transmitted directly to the connector bodies via the shoulders on the connector bodies, without loading the fixing screws additionally in shear and bending, so that with significantly less expenditure than hitherto a simpler and more economical roofing is provided.

Preferably the fixing screws are each spaced as far as possible from a shoulder of the connector body, opposite to the deflection of the bar element.

The result of this is smaller tensile loading of each fixing screw than hitherto, so that smaller, lighter and cheaper fixing screws can be employed because, by the arrangement of the fixing screw relative to the bar element and to the shoulder of the connector body, compared with a fixing screw arranged in the centre of a bar element, the moment arm of the moment resulting from the bending loading of the bar element which is transmitted by the fixing screw to the connector body, is increased so that, corresponding to the increase of the moment arm, so the force acting on the fixing screw in its longitudinal direction is reduced.

In a preferred construction of the connector body, which is light and yet rigid, and permits a plurality of different framework constructions, the connector body has a plurality of arms crossing each other in a common plane, a threaded bore for receiving a fixing screw is formed in each free end face of the arms, which bores are directed in the same direction as the longitudinal extent of the arms, and on one longitudinal side of all of the arms there is a hub which is integral with the arms, which hub extends outwardly over the free end faces of all the arms and thus constitutes shoulders for supporting the bar elements, and in the free end face of the hub facing away from the arms further threaded bores are provided which make planar or threedimensional angles with the threaded bores of the arms, the longitudinal axes of which further threaded bores cross at the intersection.

It is advantageous to make the hubs circular.

In one embodiment of the connector body the free end face of the hub is domed, and has abutment surfaces for the end faces of the bar elements, which surfaces extend at right angles to the threaded bores.

For simple manufacture, the arms and the hub can be made integrally by initial casting.

It is also possible to connect the prepared hub permanently with the arms which cross in a common plane.

In another embodiment which is useful in some circumstances the joint has a connector body of substantially spherical shape and with abutment surfaces for the bar elements aligned at right angles to the threaded bores, wherein the abutment surfaces are so recessed in the connector body that they abut at least one longitudinal side of the end parts of the bar element at a recessed flank facing towards the deflection of the bar element caused by loading, the recesses are directed transversely to the longitudinal extent of the bar elements and are formed with openings at least corresponding to the width of the associated end parts of the bar elements, and the flat abutment face for each bar element opens at the boundary surface of the connector body.

Some embodiments of the invention will now be described, by way of example, with reference to the accompanying drawings in which: Figure 1 is a front elevation, partly in section, of an intersection joint of a framework, Figure 2 is a view from above of the joint of Fig. 1, Figure 3 is a front elevation of another intersection joint according to the invention, and Figure 4 is a view from above of the joint of Fig. 3.

Referring to Fig. 1, an intersection joint is shown where three bar elements 1, 2, 3, of a framework are jointed. The bar elements are formed as hollow sections, and are joined together by means of a connector body 4.

For each bar element there is a threaded bore 5 in the connector body 4, and eachbar element is releasably fixed to the connector body 4 by means of a fixing screw 6 witha polygonal socket in its head.

The shank 7 of each fixing screw 6 extends through a matching bore 8, and is firmly screwed into one of the threaded bores 5 of the connector body 4. The head 9 of each fixing screw 6 abuts against a shoulder in the interior of the appropriate bar element, and thus clamps that bar element firmly against the connector body 4.

In the interior of each bar element there is fixed a tubular guide member 10, which is welded against the inner side of an end wall 11 of the bar element. The guide member 10 is a gently curved tube of constant annular cross-section.

The internal diameter of each guide member 10 is only slightly greater than the external diameter of the fixing screw 6 which can be pushed into the guide member 10, so that the screw is guided for longitudinal adjustment within the guide member 10.

Furthermore, the guide member 10 is gently bent in such a way that it opens into a window 12 for passage of the screw, in the wall of the bar element. The guide member 10 can be welded to the bar element in the area of this opening.

The connector body 4 consists of two arms 1 3 which cross each other in a common plane, and are of constant rectangular section, matching the bar elements 1, 2. There is a threaded bore 5 in each end face of the arms 1 3. Further, the arms 1 3 are arranged on a circular hub 14, which is made integrally with the arms 1 3 and forms a shoulder 1 5 for both the bar elements 1 and 2, against which the bar elements 1 and 2 abut directly. The lower, free end face of the hub 13 is domed and has a plurality of threaded bores 5 making planar or three-dimensional angles with the threaded bores 5 in the arms 1 3. The vertical var element 3 is fixed to the connector body 4 by means of one of these threaded bores 5.

The abutment surfaces 16 which cooperate with the free end faces of tne bar elements extend at right angles to the threaded bores 5.

A roof 1 7 is directly fixed to the bar elements 1 and 2 which constitute the upper chord of the framework, The roof exerts quasicontinuous loads on the bar elements 1 and 2, causing deflection loadings on the bar elements, directed vertically downwardly. In order to maintain as small as possible the resulting tension loading on the fixing screws 6, which are screwed into the threaded bores 5 of the arms 13, the threaded bores 5, the fixing screws 6 within the bar elements are spaced as far as possible above the shoulders 15.

This provides the longest possible moment arms 18, Fig. 2, of the moments which result from the deflection loading of the bar elements 1 and 2 and act on the fixing screws 6.

This is in contrast with fixing screws previously arranged centrally in bar elements such as the bar elements 1 and 2, and a significantly smaller force develops, acting in the longitudinal direction of the fixing screws 6, which has to be transmitted by the fixing screws 6 to the connector body 4.

As shown in chain lines, more bar elements can be joined to the connector body 4.

Referring to Figs. 3 and 4 the connector body 4' has a substantially spherical shape, with abutment faces 1 9 for the bar elements 1, 2 and 3, extending at right angles to the threaded bores 5. These abutment surfaces 1 9 are so recessed in the connector body 4' that the longitudinal faces of the end parts of the bar elements 1 and 2 abut against the lower flanks of the recesses.

For ease of assembiy of the framework, the recesses 20 are made to open upwardly in a manner such that the bar elements 1 and 2 can be fitted in from above, with their free end faces ready to bar on the abutment surfaces 19. Moreover, in the insertion area for the bar elements, the flat abutment sur faces 1 9 extend right to the bounding surface of the substantially spherical connector body 4'.

In some circumstances it could be advantageous to make the recesses 20 in the embodiment shown open not upwardly, but towards the side, so as to be able to insert the bar elements 1 and 2 from the side through these openings up to the threaded bores 5.

In this way there results plug-type couplings, acting in the vertical direction in a close-fitting manner, and rigid in bending, yielding a connection between the connector bodies and the bar elements which is stiff in bending, and has not been attained hitherto.

For erection of the framework, first the bar elements are aligned with the connector body 4, ready for abutting, and then the headed screws 6 are pushed into the guide members 10 from the screw admission windows 1 2, and are inserted in the bores 8.

Then, by means of an impact screwdriver, having a universal joint, which can be pushed into the guide members 10 of the bar elements in the same way as the fixing screws 6, the fixing screws 6 are screwed with prestresses into the threaded bores 5 of the connector body 4.

In order to be able to arrange the fixing screws 6 in a captive manner in the guide members 10 before the erection of the framework, friction members can be provided on the head of the fixing screws 6, which cooperate with the inner walls of the guide elements, and reliably prevent unintended escape of the fixing screws 6 from the guide members 10.

In all embodiments, the connector body 4 or 4' extends at most to the plane of the upper faces of the bar elements 1 and 2.

Claims (9)

1. An intersection joint for a framework of bar elements, especially for those of the upper chord of a framework, which are clamped to connector bodies, and which each have a plurality of threaded bores defining three-dimensional and/or planar angles to one another,into each of which a headed screw can be screwed, the shank of which screw matches and penetrates a bore in a bar element directed in the same direction as the threaded bore, and the head of which screw abuts axially against a shoulder face of the bar element facing away from the connector body so that the bar element is directly clamped to the connector body, characterised in that shoulders are provided on the connector bodies against which the bar elements abut in the direction of deflection of the bar element caused by loading.

2. An intersection joint according to Claim 1, wherein the fixing screws are each spaced as far as possible from a shoulder of the connector body opposite to the deflection of the bar element.

3. An intersection joint according to Claim 1 or Claim 2, wherein the connector body has a plurality of arms crossing each other in a common plane, a threaded bore for receiving a fixing screw is formed in each free end face of the arms, which bores are directed in the same direction as the longitudinal extent of the arms, and on one longitudinal side of all of the arms there is a hub which is integral with the arms, which hub extends outwardly over the free end faces of all the arms and thus constitutes shoulders for supporting the bar elements, and in the free end face of the hub facing away from the arms further threaded bores are provided which make planar or three-dimensional angles with the threaded bores of the arms, the longitudinal axes of which further threaded bores cross at the intersection.

4. An intersection joint according to Claim 3, wherein the hub is circular.

5. A intersection joint according to Claim 3 or Claim 4, wherein the free end face of the hub is domed, and has abutment surfaces for the end faces of bar elements which surfaces extend at right angles to the threaded bores.

6. An intersection joint according to any one of the preceding claims, wherein the arms and the hub are made integrally, by initial casting.

7. A intersection joint according to any one of Claim 1 to 5, wherein the prepared hub is permanently connected with the arms which cross in a common plane.

8. An intersection joint according to any one of the preceding claims, with a connector body of substantially spherical shape and with abutment surfaces for the bar elements aligned at right angles to the threaded bores, wherein the abutment surfaces are so recessed in the connector body that they abut at least one longitudinal side of the end parts of the bar element at a recessed flank facing towards the deflection of the bar element caused by loading, the recesses are directed transversely to the longitudinal extent of the bar elements and are formed with openings at least corresponding to the width of the associated end parts of the bar elements, and the flat abutment face for each bar element opens at the boundary surface of the connector body.

9. A intersection joint for a framework of bar elements, substantially as herein described with reference to the accompanying drawings.