IL96502A - Reinforced concrete ribbed ceilings and methods for the preparation thereof - Google Patents

Description

REINFORCED CONCRETE RIBBED CEILINGS AND METHODS FOR THE PREPARATION THEREOF limni? rnmen "p nw "nun niy^^n ϊτηρη -2- 96502/2 The present Invention relates to a reinforced concrete ribbed celling and a method for Its construction.

More particularly, 1t 1s concerned with providing a low-cost celling having an improved strength/weight ratio, and wherein the voids between adjacent Hbs remain available for use by service conduits.

It has long been known that the solid slab floor/celling commonly used for small spans, such as those smaller than 4 meters, does not provide the optimum form for covering large spans such as are required in public and Industrial buildings. Such ceilings are usually designed as a series of concrete ribs cast 1n situ between blocks which remain part of the completed structure; or as a series of concete ribs with topping cast on steel forms which are removed after the concrete has set; or with a continuous top and bottom face but containing voids of rectangular, oval or other shape.

It Is known that the aforementioned blocks which remain part of the structure do not contribute to the strength of the celling. Such blocks may be hollow cement, wood, foamed plastic or even carton blocks, and they will inevitably add to the cost and weight of the celling. A disadvantage of a heavy celling, aside from its own cost, lies 1n the stronger support walls or columns required for its support. A further disadvantage of these blocks is that the space -3- 96502/3 between the ribs become unavailable for use by air-conditioning and other service conduits, or by lighting fixtures. While the use of cement blocks does provide a basis for the subsequent application of a plaster coating, modern practice no longer relies on plaster coatings to such an extent as in the past, and often calls for acoustic panels or gypsum board to be applied as a lower surface. In industrial buildings, the void between the ribs is usually left uncovered and remains available for use by lighting fixtures or service conduits.

Thus it is one of the objects of the present invention to obviate the disadvantages of the prior art ceiling construction systems and to provide a system which achieves a high strength/ weight ratio at low cost, by the use of a load-carrying casting plate which remains to form part of the ceiling.

This the present invention achieves by providing a system for forming ribbed concrete ceiling slabs, comprising a plurality of spaced-apart precast concrete ribs, each of said ribs being provided with at least one upper shoulder surface; and a supporting casting plate supported upon the shoulders of two adjacent spaced-apart ribs in a general plane and adapted to serve as a casting surface; whereby an upper layer of steel-reinforced concrete is castable on said casting plate to form the upper surface of a ceiling slab.

It is a further object of the present invention to provide an improved method for forming ribbed concrete ceiling slabs, comprising the steps of arrangi ng a plurality of reinforced concrete ribs, each provided with two upper shoulder surfaces; arranging said ribs in parallel horizontal formation; laying supporting casting plates in a general plane to bridge the gaps between adjacent ribs, each supporting casting plate resting on an upper shoulder of two adjacent ribs and remaining to form a - 4 - 96502/2 permanent part of the structure; layering reinforcing rods on said supporting casting plate, and casting a layer of concrete on the supporting plates to submerge said reinforcing rods.

Here it may be mentioned that a ribbed ceiling may include secondary ribs oriented at right angles to the main ribs, but these are not shown in the present disclosure as not forming part of the present invention.

Reinforced concrete floors and similar structures are described in Israel Patent 31401 and German Patent 2,306,379; however, both of said patents teach and are limited to the use of arched shutterings, and do not teach or suggest the use of a supporting casting plate located in a general plane, which is both structurally different and inter alia also enables the use of substantially less cast concrete.

The invention will now be described in connection with certain preferred embodiments with reference to the following illustrative figures so that it may be more fully understood.

With specific reference now to the figures in detail, it is stressed that the particulars shown are by way of example and for purposes of illustrative discussion of the preferred embodiments of the present invention only and are presented in the cause of providing what is believed to be the most useful and readily understood description of the principles and conceptual aspects of the invention. In this regard, no attempt is made to show structural details of the Invention in more detail than is necessary for a fundamental understanding of the Invention, the description taken with the drawings making apparent to those skilled in the art how the several forms of the invention may be embodied in practice.

In the drawings: Fig. 1 shows a perspective view of a preferred embodiment of the celling slab shown after casting of the celling upper surface; Fig. 2 is a detail view of a rib and its surrounding components as shown in F1g. 1; Fig. 3 is a cross-sectional view taken at AA of Fig. 2; Fig. 4 1s a perspective view of a second embodiment of the supporting casting plate; and Fig. 5 1s a cross-sectional view of a further embodiment of the celling slab according to the Invention.

There 1s seen in Figs. 1, 2 and 3 a ribbed concrete celling slab 10. A plurality of spaced-apart concrete precast ribs 12 are each provided with two upper shoulder surfaces 14, 14'. The ribs 12 may advantageously be of general trapezoidal cross-section. This shape will bring a greater area of concrete to bear the compressive forces to which the upper part 16 of the ribs 12 1s subjected when the rib 12 1s subjected to a bending moment when the slab is in use.

Steel reinforcing rods 18 are cast into the rib 12, their primary function being to resist the tensile forces which will be exerted on the lower part 20 of the rib 12 when the rib 12 1s subjected to the aforementioned bending moment. Preferably the reinforcing rods 18 also project upwards above the shoulder surfaces 14, 14', whereby a bound structural connection 1s made with the upper layer 22 of steel reinforced concrete which is subsequently cast.

The rib 12 1s preferably provided with a recess 24 on its upper face between the shoulder surfaces 14, 14'. This recess 24 will be filled by concrete when subsequently the upper layer 22 1s cast, and thereby Improves the bond between the rib 12 and the upper layer 22. A supporting casting plate 26 having a length slightly less than the center distance between adjacent ribs 12 is supported upon the upper shoulder surfaces 14, 14' of two adjacent ribs 12. The supporting casting plate 26 shown 1n this embodiment comprises a corrugated metal sheet, such sheets being commonly made of galvanized steel, and it is adapted to serve as a casting surface for the subsequent addition of an upper layer 22 of steel-reinforced concrete which serves as the upper surface of the celling slab 10. The steel supporting casting plate is a relatively lightweight item yet well able to carry the weight of the concrete being poured thereon. Subsequently it - -remains as part of the ceiling slab 10 and when anchored to the shoulder surfaces 14, 14' or provided with means to engage the upper layer 22, makes a substantial contribution to resisting the tensile forces to which the lower part of all ceilings are subjected. Obviously there is also some saving in labor as compared to the use of conventional casting forms which require removal, cleaning and possible storage before being reused.

Fig. 4 shows a second embodiment of the supporting casting plate. A metal latticework 28 typically formed from round-section steel rods welding at their joints has a general shape of a shallow inverted U. At least one face of the latticework 28 is covered with a tough plastic film 30. While the slab is being formed, the legs 31 of the inverted U subsequently are positioned to rest on the shoulder surfaces 14, 14' shown 1n Fig. 2 and the plastic film 30 supports the concrete of the upper layer 22 poured thereon.

The cross members 32 project into and engage the upper layer 22 and are therefore able to accept the tensile force exerted on them when the celling slab 1s in use.

Fig. 5 shows a celling slab 34 provided with a supporting casting plate 36 which 1s formed of a precast reinforced concrete. The precast ribs 38 are generally similar to the rib 12 described with reference to Fig. 2. Preferably a ridge 40 is provided on each upper shoulder surface 42, 42' and two corresponding matching grooves 44 are cast near two opposite edges of the supporting casting plate 36. This anchoring of the supporting casting plate 36 to adjacent ribs 38 facilitates the transfer of tensile forces from the former to the latter. Furthermore, a plurality of projections 46 formed above the upper surface of the casting plate 36 are preferably provided, these facilitating the transfer of tensile forces from the upper layer 22 to the supporting casting plate 36.

The present Invention also provides for a method of forming the celling slabs, which will be described with reference to the embodiment of Figs. 1, 2 and 3 but 1s applicable also to the other embodiments.

A method for forming ribbed concrete ceiling slabs 10, comprising the steps of a. preparing a plurality of reinforced concrete ribs 12 each provided with two upper shoulder surfaces 14, 14'; b. arranging the ribs 12 in parallel horizontal formation; c. laying supporting casting plates 26 to bridge the gaps between adjacent ribs 12, each supporting casting plate 26 resting on an upper shoulder surface 14, 14' of two adjacent ribs 12, the supporting casting plates remaining permanently as a structural part of the ceiling slab 20; d. laying reinforcing rods 18 on the supporting casting plates 26; and B. casting an upper layer 22 of concrete on the supporting casting plates 26 to submerge the reinforcing rods 18.

It need only be added that small celling slabs may conveniently be cast at ground level and when completed be lifted onto the structure being built, while large ceiling slabs will more conveniently be assembled and formed on the structure at the height where the ceiling slab is required.

It will be evident to those skilled 1n the art that the invention is not limited to the details of the foregoing illustrative embodiments and that the present Invention may be embodied in other specific forms without departing from the spirit or essential attributes thereof. The present embodiments are therefore to be considered 1n all respects as illustrative and not restrictive, the scope of the Invention being indicated by the appended claims rather than by the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.

Claims (6)

-10- 96502/3 WHAT 18 CLAIMED IS:

1. A system for forming ribbed concrete ceiling slabs, comprising a plurality of spaced-apart precast concrete ribs, each of said ribs being provided with at least one upper shoulder surface; and a supporting casting plate supported upon the shoulders of two adjacent spaced-apart ribs in a general plane and adapted to serve as a casting surface; whereby an upper layer of steel-reinforced concrete is castable on said casting plate to form the upper surface of a ceiling slab.

2. The system for forming ribbed concrete ceiling slabs as claimed in claim 1, wherein said supporting casting plate is formed of a corrugated metal sheet.

3. The system for forming ribbed concrete ceiling slabs as claimed in claim 1, wherein said supporting casting plate is formed of a plastic-coated metal latticework.

4. The system for forming ribbed concrete ceiling slabs as claimed in claim 1, wherein said supporting casting plate is formed of a pre-cast reinforced concrete plate.

5. A system for forming ribbed concrete ceiling slabs, substantially as hereinbefore described and with reference to the accompanying drawings. -11- 96502/3

6. A method for forming ribbed concrete ceiling slabs, comprising the steps of arranging a plurality of reinforced concrete ribs, each provided with two upper shoulder surfaces in parallel horizontal formation; laying supporting casting plates in a general plane to bridge the gaps between adjacent ribs, each supporting casting plate resting on an upper shoulder of two adjacent ribs and remaining to form a permanent part of the structure; layering -a¾€h reinforcing rods on said supporting casting plate, and casting a layer of concrete on the supporting plates to submerge said reinforcing rods. for the Applicant: WOLFF, BREGMAN AMD GOLLER