Static structures (e.g. – buildings) – Openwork; e.g. – truss – trellis – grille – screen – frame – or... – Side-by-side terminus shafts; e.g. – truss
Patent
1996-01-19
1998-09-08
Safavi, Michael
Static structures (e.g., buildings)
Openwork; e.g., truss, trellis, grille, screen, frame, or...
Side-by-side terminus shafts; e.g., truss
527242, 527243, 249 95, 249 96, E04C 320, B22O 1902
Patent
active
058028021
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
Arrangement for trusses with open web, trusses of the type with two chords, trusses of the type with two chords with at least one cast chord, and also chords for a slab of a cast member with an open web of a bar, wire or strip material with various types of arrays, fastened to the chords or to the chord and the slab, respectively.
BACKGROUND OF THE INVENTION
As companies producing pre-cast concrete are provided with widely differing equipment and capability to produce members of this kind, a number of varieties as regards web design is required. These truss webs have been developed in order to facilitate manufacture with a reasonable financial investment, but are also adapted to cast chords as well as chords made from steel tubing.
The invention is a development of a truss or a truss component or a member possibly to be cast with open web of wires or strip material bent to a zig-zag or zig zag resembling array according to Swedish patent SE 450135 and a further development of Swedish patent SE 466860 referring to a cast member consisting of a slab with strengthening chords, as well as PCT Patent Application PCT/SE92/00810 published as WO 93/11323, regarding trusses with single or double chords.
The chord of the cast member and the double chord trusses are provided with a chord with a web that is mainly bent to a zig-zag array, of which one configuration item 10 (with reference to FIGS. 1 to 3 in SE 466 860 ), has been given a new, different design in order to facilitate simultaneous casting of a chord and a slab.
It is desirable to be able to cast the chords at the same time as the member slab in order to avoid unnecessary handling caused by heavy pre-cast chords and in order to speed up the manufacturing process.
This invention indicates a solution to the above problem.
SUMMARY OF THE INVENTION
Today it is desired to manufacture members of large spans without intermediate supports, with the slab facing upwards and the chords below the slab.
The chords will in this case be subjected to tensile forces only, and because of this it is desired to use materials, e.g., steel sections, which can effectively take care of such forces. A web made from wire should then be provided with bends adapted to the shape of the chord at the point of connection, and the web can be fastened by means of a suitable method, e.g. welding.
Crosswise arranged bends of the webs at the connection to a cast slab or a chord have been subjected to tests on prototypes and show excellent properties as regards member performance, particularly as there is a possibility to provide the connection with longitudinal reinforcement and anchor bars in parallel with the main forces, without having to connect web and bars by welding, for example.
It is, however, difficult to manufacture long webs in one piece for the large spans and member depths in question. Fairly robust webs are required in these structures at these spans, in order to attain adequate stability, for example bar sizes of 10 to 12 mm diameter. Most machines can manage 8 mm diameter and manufacture webs bent in one plane. The machines are too expensive, neither are they available on the market, and development of new machines is too expensive for the time being. The invention provides a solution to this problem.
Examples of technologies known today through patents are given below.
As regards U.S. Pat. No. 4,185,423, designs are illustrated, constructed of webs bent in one plane where the web is welded to chord of steel sections. When embedded in a slab, these chords are provided with such a welded bar in order to obtain fully satisfactory anchorage. Test results indicate much improved performance of perpendicular bends when cast into a slab and facilitate slimmer dimensions in the structures, e.g. a thinner slab. However, in the invention the bends of the web are arranged perpendicular or oblique when embedded in a chord or a slab.
As regards WO 82/02916, a web with bends in one plane is indicated. The same comments as regards the joint apply equally here,
REFERENCES:
patent: 893792 (1908-07-01), Gabriel
patent: 3036676 (1962-05-01), Potzsch
patent: 4185423 (1980-01-01), Gutierrez
patent: 4660346 (1987-04-01), Burger et al.
Resaro AB
Safavi Michael
LandOfFree
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