GB1589606A

GB1589606A - Lattice frames

Info

Publication number: GB1589606A
Application number: GB3184377A
Authority: GB
Original assignee: BAUTECHNIK ANSTALT
Current assignee: BAUTECHNIK ANSTALT
Priority date: 1976-07-29
Filing date: 1977-07-28
Publication date: 1981-05-13
Also published as: MX144850A; ATA557476A; NL7708382A; DE2733941A1; BE857304A; AT348217B

Description

(54) LATTICE FRAMES (71) We, BAUTECHNIK ANSTALT, a Liechtenstein Company, of Kirchstr. 1, Vaduz, Fustentum, Liechtenstein do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: The invention relates to lattice frames, more particularly to lattice frames having at least one top chord and two bottom chords running parallel to one another.

In such frames, the top and bottom chords may be joined by means of diagonal braces which comprise a pair of diagonal, generally serpentine, wires which lie in two planes intersecting in the zone of the top chord and extending in the longitudinal direction of the lattice frame.

Such lattice frames are known and may serve as reinforcement members, in particular for supporting ceilings in construction work. In general, the serpentine joining or bridging wires extend over the whole length of the lattice frame. The production of such lattice frames by means of welding and bending machines and their application is sufficiently well known to make further description of them unnecessary.

A problem found with the known lattice frames is that prefabricated reinforced concrete slabs, for instance, have one or more lattice frames, according to their dimensions. These concrete slabs are cast on site after erection on supports. With the known steel supporting frames it is possible for certain of the lower chord nodes to be located between pairs of supports, and, because of the moments occurring the chord may sag leading to a layer of concrete beneath the lower chord, which is too thin and may disappear when the concrete is tramped out.

Objects of the invention include the provision of forms of lattice frames overcoming or alleviating the above-noted problems.

According to the invention there is provided a lattice frame with at least one upper chord and two lower chords running parallel thereto, the upper chord and lower chords being joined to one another along their length by a pair of continuous wire braces of generally serpentine form, which braces lie in planes intersectig one another adjacent the upper chord and extending in the longitudinal direction of the frame, wherein the two generally serpentine wires are staggered relative to one another such that the apexes of the peaks of one wire are at positions, along the length of the frame, corresponding to the lowest points of the other wire.

By staggering the wave troughs and peaks, a halving of the unsupported length is attained for a given chord, which yields significant economy of material for the frame.

Furthermore, the possibility is considerably improved that, with lattice frame cut to different lengths, a welded joint between the chord and the bridging wire will lie upon a support. With a system spacing of 20 cm for instance (that is the spacing between consecutive wave troughs of an undulating diagonal wire) there must be a weld point every 10 cm, measured along the length of the lattice frame, in the case of lattice frames embodying the invention. In the case of the supporting breadth required in Austria, for example of 122 cm, one node point of the lattice frame will therefore always lie on the support.

A preferred embodiment of the invention provides that the upper wave peaks of one generally serpentine wire extend above the upper chord and that the upper chord is joined to a diagonal strut of this wire. Again it may advantageously be provided that the two generally serpentine wires cross over in the zone of the upper chord. One embodiment thereby provides that the wire with the greater wave height passes beneath the upper chord.

In order to attain a significantly better strength for the lattice frame, it is further provided that where the generally serpentine wires pass closely to one another, the two wires are joined together, for instance by welding.

The extension above the upper chord leads to a material economy of one half when full cambering is required in the upper surface zone, without the erection rigidity of the supporting frame being impaired.

Through this, the production or adaptation of such lattice frames for different required heights is considerably simplified, since no adjusting work in the height of the supporting frame is necessary on the machine used to weld the wires to the upper and lower chords.

If, then, the generally serpentine wire with greater wave height is taken under the upper chord and the diagnonal struts of the two wires are welded to one another, the result is an increase in the buckling strength of the diagonal struts, since the free unsupported length of the diagonal struts is reduced. It further results - and it is to be particularly emphasised - in strengthening of the three-dimensional frame-work, since the triangle formed by the upper chord and the two diagonal struts lies in a plane which is at an angle to the plane in which the diagonal wires run.

The pulling up of the wire of a diagonal wire, that is, lowering the upper chord in relation to it together with the joining lines of the two diagonal wires, introduces a higher lateral rigidity of the lattice frame.

Furthermore, for a given concrete base dimension, it yields a larger clear width between the lower chords, which is of particular significance for the introduction of additional wires. The flatter angle of the diagonal wires to the supporting plane of the lattice frame furthermore simplifies the laying of ceiling slabs.

One embodiment makes provision that the part of the diagonal wire pulled up above the upper chord is bent roughly at right-angles, with the zones of the wire running vertical directed at an angle of about 90" to the upper chord.

A further embodiment of the invention provides that one diagonal wire or both diagonal wires are bent under the lower chords, when the bent ends lie at least approximately in a plane joining the two lower chords and for instance form supports for additional wires.

One preferred embodiment provides that the parts of the one undulating diagonal wire protruding above the upper chord are bent back in a plane which in the erected attitude lies at least approximately normal to the plane of the support for the lattice frame.

A further embodiment of the invention is characterised by additional wires welded on the lattice frame. Such additional wires, which are preferably welded on to the diagonal wires in the zone of the lower chord, require no special additional contact length and may be disposed exclusively in those places where they are used in order to cover the bending moment.

Various embodiments of lattice frames according to the invention are described below with reference to the accompanying drawings in which: Figure 1 schematically shows one embodiment of a lattice frame in accordance with the invention, Figure 2 schematically shows a second embodiment of a lattice frame in accordance with the invention Figures 3, 4 and 5 show schematic sections of different embodiments of a lattice frame in accordance with the invention Figure 6 is a side view of an embodiment of a lattice frame in accordance with the invention, Figure 7 is a section drawn on A of Figure 2; and Figure 8 shows a further embodiment of a lattice frame in accordance with the invention.

In the embodiment of Figure 1, the lattice frame has an upper chord 3 and two lower chords 4, the upper and lower chords being joined together by means of diagonally extending wires 1 and 2. The upper chord 3 and the lower chords 4 are joined to the diagonal wires 1, 2 (at the individual contact points) in the known way by means of spot welding.

As can be seen from Figure 1, the two undulating diagonal wires 1, 2 are staggered relative to one another so that (viewed from one side of the frame) at all times an upper wave peak S joined to the upper chord 3 lies opposite a wave trough T of the opposite diagonal wire 1, 2 joined to a lower chord 4.

This results in a reduction of the buckling length of the lattice frame.

The lattice frame of Figure 2 shows the same feature, only in this embodiment the wave peaks S of the diagonal wire 2 extend above the upper chord 3. Here the diagonal struts 2' run underneath the upper chord 3 and are welded thereto at contact points 5.

They are additionally welded to struts 1' of the diagonal wire 1 at contact points 6. This results in a triangle 5, 6, 7 (shown in more detail in Figure 7) that is located threedimensionally in the lattice frame. Numeral 7 indicates the welding point of the upper wave peak of the smaller diagonal wire 1 with the upper chord 3.

A section of this embodiment is shown in Figure 3.

In the embodiment of Figure 4, the part 2, 2" of the diagonal wire 2 extending above the upper chord 3 is bent in the plane X the erected location of which lies perpendicular to the support plane indicated by Y in the drawing. The advantages of this embodiment have already been mentioned.

Figure 5 shows a cross-section of the lattice frame in accordance with the invention in which the lower tips BE of the diagonal wires 1, 2 are beneath the chords 4 into the lattice frame, in order to form supports for additional wires 8.

Figure 6 shows an example of a lattice frame with an additional wire 8, welded on, which only extends over the length of the lattice frame, and which is necessary in order to cover the bending moment occurring.

Figure 8 shows an example of a lattice frame similar to that shown in Figure 2 but in which the parts of the wire 2 above the chord 3 have been formed generally rectangularly and have been bent up into the plane X referred to in Figure 4.

WHAT WE CLAIM IS: 1. A lattice frame with at least one upper chord and two lower chords running parallel thereto, the upper chord and lower chords being joined to one another along their length by a pair of continuous wire braces of generally serpentine form, which braces lie in planes intersecting one another adjacent the upper chord and extending in the longitudinal direction of the frame, wherein the two generally serpentine wires are staggered relative to one another such that the apexes of the peaks of one wire are at positions along the length of the frame, corresponding to the lowest points of the other wire.

2. A lattice frame according to Claim 1, wherein the apexes of the peaks of at least one generally serpentine wire extend above the upper chord, and wherein the upper chord is joined to parts of this wire at positions to either side of said apexes.

3. A lattice frame according to Claim 1 or Claim 2, wherein the two generally serpentine wires pass adjacent one another in the zone of the upper chord.

4. A lattice frame according to Claim 3, wherein one of the wires extending above and passes through the other wire below the upper chord of the frame.

5. A lattice frame according to Claim 3 or Claim 4, wherein the adjacent parts of the two wires are joined together.

6. A lattice frame according to Claim 5, wherein the adjacent parts of the two wires are welded together.

7. A lattice frame according to any one of Claims 1 to 5, wherein one or both wires are bent around their respectively associated lower chords so that their bent ends lie, at least approximately, in a plane joining the two lower chords.

8. A lattice frame according to Claim 2, wherein the part of the said one generally serpentine wire extending above the upper chord is bent through approximately 90" such that the parts of the wires passing the upper chord are directed at an angle of approximately 90" thereto.

9. A lattice frame according to any one of Claims 2 to 8, wherein the parts of the one wire extending above the upper chord are bent to be in a plane which is approximately normal to the plane of the frame support.

10. A lattice frame according to any one of Claims 1 to 9, and including additional wires welded onto the lattice frame.

11. A lattice frame substantially as hereinbefore described with reference to the accompanying drawings.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. with the upper chord 3. A section of this embodiment is shown in Figure 3. In the embodiment of Figure 4, the part 2, 2" of the diagonal wire 2 extending above the upper chord 3 is bent in the plane X the erected location of which lies perpendicular to the support plane indicated by Y in the drawing. The advantages of this embodiment have already been mentioned. Figure 5 shows a cross-section of the lattice frame in accordance with the invention in which the lower tips BE of the diagonal wires 1, 2 are beneath the chords 4 into the lattice frame, in order to form supports for additional wires 8. Figure 6 shows an example of a lattice frame with an additional wire 8, welded on, which only extends over the length of the lattice frame, and which is necessary in order to cover the bending moment occurring. Figure 8 shows an example of a lattice frame similar to that shown in Figure 2 but in which the parts of the wire 2 above the chord 3 have been formed generally rectangularly and have been bent up into the plane X referred to in Figure 4. WHAT WE CLAIM IS:

1. A lattice frame with at least one upper chord and two lower chords running parallel thereto, the upper chord and lower chords being joined to one another along their length by a pair of continuous wire braces of generally serpentine form, which braces lie in planes intersecting one another adjacent the upper chord and extending in the longitudinal direction of the frame, wherein the two generally serpentine wires are staggered relative to one another such that the apexes of the peaks of one wire are at positions along the length of the frame, corresponding to the lowest points of the other wire.