US 3398498 A
Description (OCR text may contain errors)
Aug. 27, 1968 p. uss 3,398,498
COMPOSITE STEEL TRUSS AND PRECAST CONCRETE SLAB AND BEAM UNITS 2 Sheets-Sheet 1 Filed Sept. 9, 1966 "Warren PAUL KRAUSS Aug. 21, 1968 P. KRAUSS 3,398,498
COMPOSITE STEEL TRUSS AND' PRECAS'I CONCRETE SLAB AND BEAM UNITS Filed Sept. 9, 1966 2 Sheets-Sheet 2 \xmsxm xxx I INVINTOR PAUL KRAUSS @g ziw United States Patent F 3,398,498 COMPOSITE STEEL TRUSS AND PRECAST CONCRETE SLAB AND BEAM UNITS Paul Krauss, Winnipeg, Manitoba, Canada, assignor to Barkrauss Enterprises Ltd., Winnipeg, Mamtoba, Canada Filed Sept. 9, 1966, Ser. No. 578,341 8 Claims. (Cl. 52-691) ABSTRACT OF THE DISCLOSURE A composite concrete and steel truss consisting of a reinforced concrete slab or beam with a plurality of downwardly depending webs and a number of exposed steel members. The steel members incorporated with the concrete slab and webs produce a composite truss unit in which the steel members are the tension chord and tension diagonals and the concrete slab and vertical webs are the compression members.
This invention relates to new and useful improvements in composite steel truss and precast concrete slab and beam units.
The invention consists primarily of a precast concrete slab having a central longitudinally extending concrete member upon the underside thereof and a plurality of downwardly depending, substantially rectangular webs. Incorporated with the structure and precast therewith is an arrangement of steel tension bars, the principal ones extending from end to end of the truss and engaging the lower edges of the webs. Secondary reinforcing extends from the lower edges of some of the webs, diagonally upwardly into the aforementioned longitudinal member.
Open web, steel joist floors are normally used in construction and 5115561 from several disadvantages.
Such disadvantages include poor load distribution transverse to the joist span and subsequent poor resistance to concentrated loads such as partitions, ofiice machines, and the like.
Another disadvantage is light weight and poor transverse load distribution which results in a very low vibration resistance to the structure.
Such open web steel joist floors usually include a relatively thin 2" poured concrete floor slab which is poured in situ, and is therefore very much subject to shrinkage, cracking, premature drying and subsequent dusting.
Furthermore the curing of thin slabs also presents a considerable problem both in summer and winter weather.
The conventional open web steel joist floor includes the joist seat and slab, the total depth of which conventionally are approximately 4 /2". Unfortunately this is neither a modular brick nor block dimension and is therefore awkward in bearing wall construction.
The use of steel joists over crawl spaces is not recommended unless expensive rust protection is carried out. The thin wall rolled chord sections, high stress steel, and fusion welded web connections combined are easily subject to corrosion.
Todays open web steel joists are mass produced, using electric fusion welding. Therefore quality control is difficult and defects, such as poor or broken welds, occur frequently.
The installation of duct work transverse to steel joists within the joist space is difiicult due to frequent occurrence of joist web members necessary for strength characteristics.
Finally, fire resistance of the floor can only be achieved by the installation of a fire resistant ceiling therebelow.
The above disadvantages are largely counteracted by the present invention inasmuch as the concrete compression verticals of the truss system are carried out as reinforced Patented Aug. 27, 1968 slabs. After installation of the floor system, these slabs act as continuous distribution members and by modification of the reinforcing and connections, full 2-Way load distribution can be achieved.
The relatively deep concrete bridging beams hereinafter to be described, greatly increase the vibration resistance of the floor and the factory controlled precast concrete slab and the longitudinal compression in the slab due to truss action will result in a crack free floor.
The present slab system hereinafter to be described, lends itself to winter construction because all structural field connections are welded or bolted and the grouting of joints can be carried out after the building is closed in and heated.
The dimensions of the present device include the seats of the slab which have a depth of one standard concrete block and therefore will replace a full block course during the building operation. The 7%" depth of the seat and the beam depth under the slab can be maintained for any span length.
The truss tension chords consist of plain round solid bars which do not tend to collect dust and corrosive moisture. Inasmuch as no welding is used in the manufacture of the truss, the bars can be precoated for rust resistance.
No structural welding is used in the fabrication of the slab units and therefore quality control regarding structural strength is dependent on concrete control only, a well known and simple standard procedure.
The construction permits air ducts of considerable size to be installed in both directions. By leaving the diaphragms or webs solid, air return plenums may be created by simply closing the bottom of the passages defined by the plurality of webs.
With little additional cost, built in concrete ducts can be provided for floor electrification purposes.
The use of open web composite floor beams as shown, will permit duct work installation completely within the floor construction and the fire resistance of the slabs and beams can easily be achieved by concrete or plaster coating of exposed steel tension members.
With the foregoing in view, and all those objects, purposes or advantages which may become apparent from consideration of this disclosure and specification, the present invention consists of the inventive concept embodied in the method, process, construction, arrangement of parts, or new use of the same, as herein particularly exemplified in one or more specific embodiments of such concept, reference being had to the accompanying figures in which:
FIGURE 1 is a side elevation showing a four panel truss.
FIGURE 2 is an underside isometric view of the four panel truss shown in FIGURE 1.
FIGURE 3 is an end elevation, on reduced scale, showing a section of erected truss slabs.
FIGURE 4 is an enlarged cross sectional view substantially along the line 44 of FIGURE 1.
FIGURE 5 is a section substantially along the line 55 of FIGURE 1.
FIGURE 6 is a section substantially along the line 6-6 of FIGURE 4.
FIGURE 7 is a section substantially along the line 77 of FIGURE 5.
In the drawings like characters of reference indicate corresponding parts in the different figures.
Proceeding therefore to describe this invention in detail, reference should be made to the accompanying drawings which show the panel truss.
It will, of course, be appreciated that the panel truss is cast in an upside down position within a mould (not illustrated) for ease of manufacture.
The truss illustrated in FIGURES 1 to 5 inclusive comprises a relatively thin upper rectangular slab including conventional reinforcing wires 11 and 11'.
At either end of the panel 10 are cast in place end seats 12 by which the slabs may be supported upon building walls.
Depending downwardly from the underside 13 of the panel 10 is a plurality of webs or diaphragms 14 substantially rectangular when viewed in section, these webs or diaphragms are precast and set in place and being reinforced by reinforcing wires or rods 15 and 15'. Rods 15 are diagonally situated and rods 15 are substantially open rectangular, the upper sides of which extend into the center line of the panel 10.
It is desirable to leave a cylindrical aperture 16 one upon each side of the diaphragm but, if desired, these may be closed.
Extending longitudinally upon the center line of the panel and upon the underside thereof is the main concrete rib or longitudinal member 17 also cast in place, which not only acts as a strengthening rib or beam but also as a retaining anchor for the tension rods or members colectively designated 18.
The main tensioning rods specifically designated 19 comprise a pair of spaced and parallel, rolled steel rods, the ends 20 of which incline upwardly through the ends 21 of the main ribs 17 and hook downwardly as at 22, within the seats 12 thus anchoring these rods securely within the truss.
The major portions 23 of these rods engage the under side edges 24 of the diaphragms as clearly shown in the drawings and are Welded to bearing plates 25 within the underside edges 24, said arrangement being shown in FIGURE 4.
A secondary reinforcing rod or load transfer member 26 is secured centrally of the rods 19, to the plates 25 of the central Web or diaphragm and the portion 27 of this rod extends diagonally upwardly into the main rib 17 and then hooks downwardly as at 28 in order to be anchored within this rib adjacent the webs or diaphragms upon either side of the central web or diaphragm.
FIGURES 1 and 2 show a four panel truss slab which has just been described but it will be appreciated that a six panel truss can be formed in which the reinforcing bars are similarly arranged, there being additional secondary bars 26 upon each side of the center of the truss slab.
Also cast in place within the flanges, webs or diaphragms 14, are welding plates 29 secured to hook anchors 30 and these Welding plates are flush with the surface of the side edges 31 of the diaphragm 14.
When the truss slabs are placed upon the supporting walls in side 'by side relationship as shown in FIGURE 4, adjacent slabs may be levelled by jacking and then the slabs may be welded together at the diaphragms by means of the plates 29 of adjacent diaphragms which are in interfaci-al contact.
This gives an extremely smooth and level floor surface which does not require the conventional floor topping.
It will be noted that the longitudinal edges of the upper panel 10 are provided with longitudinal recesses 32 (see FIGURE 5) and these grooves may be grouted when the welding has been completed.
Various modifications can be made within the scope of the inventive concept disclosed. Accordingly, it is intended that what is described herein should be regarded as illustrative of such concept and not for the purpose of limiting protection to any particular embodiment there of, but that only such limitations should be placed upon the scope of protection to which the inventor hereof is entitled, as justice dictates.
What I claim as my invention is:
1. A composite steel truss and precast concrete slab and beam unit comprising in combination a substantially elongated rectangular upper concrete slab, longitudinally and transverse extending steel reinforcing in said slab, a slab seat formed on each end of said slab and depending downwardly therefrom; a plurality of transverse concrete webs formed integrally with and depending downwardly from the underside of said slab at intervals along the length thereof, and at least one steel tension member secured intermediate the ends thereof to the base of at least one of said webs, the ends of said tension member inclining upwardly towards the ends of said slab and being secured to said slab, said tension member extending longitudinally of said slab, and at least one secondary tension member secured intermediate the ends thereof to one of said webs, the ends of said secondary tension member also inclining upwardly towards the ends of said slab and being secured to said slab inboard of the ends thereof.
2. The device according to claim 1 which includes a longitudinally extending beam formed integrally with said slab and said webs and upon the underside of said slab, said beam connecting with said seats at each end thereof.
3. The device according to claim 1 in which said webs include a pair of diagonally situated reinforcing rods and a pair of open rectangular reinforcing rods.
4. The device according to claim 2 in which said webs include a pair of diagonally situated reinforcing rods and a pair of open rectangular reinforcing rods.
5. The device according to claim 1 in which each web is provided with welding plates embedded therein, hook anchors secured to said welding plates and extend inwardly into said web, one side of said welding plate being flush with the side edges of said webs whereby adjacent welding plates of adjacently situated slabs may be welded together to form an integral structure.
6. The device according to claim 2 in which each web is provided with welding plates embedded therein, hook anchors secured to said Welding plates and extend inwardly into said web, one side of said welding plate being flush with the side edges of said webs whereby adjacent welding plates of adjacently situated slabs may be welded together to form an integral structure.
7. The device according to claim 3 in which each web is provided with welding plates embedded therein, hook anchors secured to said welding plates and extendinwardly into said web, one side of said welding plate being flush with the side edges of said webs whereby adjacent welding plates of adjacently situated slabs may be Welded together to form an integral structure.
8. The device according to claim 4 in which each web is provided with welding plates embedded therein, hook anchors secured to said welding plates and extend inwardly into said web, one side of said welding plate being flush with the side edges of said webs whereby adjacent Welding plates of adjacently situated slabs may be Welded together to form an integral structure.
References Cited UNITED STATES PATENTS 1,572,669 2/1926 Muller 52-723 2,154,619 4/1939 Hurley 52587 2,813,310 11/1957 Harrison 52-226 2,912,849 11/ 1959 Wissinger 52-723 FOREIGN PATENTS 464,361 4/ 1937 Great Britain. 1,018,618 10/1952 France.
FRANCIS K. ZUGEL, Primary Examiner.