US3462902A - Composite floor construction - Google Patents

Description

6, 1969 R. E. ALBRECHT ET AL 3,462,902

COMPOS ITE FLOOR CONSTRUCTION Filed Dec. 20. 1965 //VV'/V7'0/\5. RAYMOND E. ALBRECHT, BERNARD E. CURRAN ROBERT G. LINDNER United States Patent 3,462,902 COMPOSITE FLOOR CONSTRUCTION Raymond E. Albrecht and Bernard E. Curran, Sewickley,

and Robert G. Lindner, Bridgeville, Pa., assrguors to H. H. Robertson Company, Pittsburgh, Pa., a corporation of Pennnsylvania Filed Dec. 20, 1965, Ser. No. 514,976

Int. Cl. E04!) 5/16, 13/04 U.S. Cl. 52336 3 Claims ABSTRACT OF THE DISCLOSURE A composite floor construction utilizing corrugated sheet metal decking and concrete. The allowable loading for a specific span of composite flooring is significantly increased by the inclusion of wires or mesh embedded in the concrete in those regions where the decking rests upon a horizontal beam of the building framework. The quantity of wires or mesh is insufficient to satisfy the requirements of the American Concrete Institute for shrinkage and temperature reinforcement of concrete generally.

This invention concerns composite floor construction utilizing corrugated sheet metal decking and concrete.

PRIOR ART In the construction of many multi-story buildings, the floors are assembled from corrugated sheet metal decking which is rigidified by a covering concrete layer. Such floor construction is described in U.S. Patents 1,855,082, 2,259,674. The concrete component of such floor construction is considered as a parasitic mass making no contribution whatsoever to the load carrying capability of the building floor. The corrugated metal decking sustains the entire load including the weight of the concrete.

There are other floor constructions utilizing corrugated sheet metal decking merely as a form for supporting a poured-in-place reinforced concrete slab which serves as a building floor, 1,073,540; 1,073,542. Such concrete slabs combine the hardened concrete with metal tension reinforcement rods or wires.

More recently various proposals have been advanced for utilizing the load carrying capability of concrete components in combination with the load carrying capability of the sheet metal decking elements. The two materials are combined and the resulting floor has been identified as a composite floor. Typical composite floor construction has been described in Canada Patents 704,839; 704,- 840; 704,841 and 704,842. All of these composite floor constructions utilize corrugated sheet metal decking having alternating crests and valleys with generally vertical webs therebetween. The sheet metal decking extends generally horizontally between the horizontal beams of the building framework and is covered with concrete to form a composite floor construction. The crests of such corrugated metal fiooring sections are deformed from a plane, preferably by indented or embossed grooves which are transverse to the longitudinal axis of the decking sections. The decking also has some means to retain the covering layer of concrete in tight engagement with the decking sections. This hold-down means may take the form of diverging webs as described in Canada Patents 704,839 and 704,840; or may take the form of deformations such as indentations or embossments along the vertical web generally parallel to'the longitudinal axis of 3,462,902 Patented Aug. 26, 1969 THE PROBLEM The provision of greater allowable loadings for certain span lengths with such composite fioor constructions would extend the applicability of such flooring constructions. Conversely, for constant allowable loadings, greater spans might be realized.

THE PRESENT INVENTION According to the present invention, we have discovered a surprising means which achieves an increase of approximately 66% in the allowable loading for a specific span of composite flooring.

The composite flooring of this invention utilizes the composite corrugated sheet metal flooring sections as described in the above-mentioned Canada patents. Those flooring sections extend across the horizontal beams of the building. A supply of metal wires or mesh is provided above the corrugated metal decking in those regions where the decking rests upon a horizontal beam of the building framework. The metal wires or mesh are displaced above and out of engagement with the corrugated metal decking. The metal wires or mesh are embedded in the concrete cover which is subsequently poured above the structure. In order to support the metal wires or mesh above the corrugated metal decking prior to the pouring and hardening of the concrete, suitable wire chairs or other non-structural spacer members may be provided.

The unexpected feature of the present invention is the remarkable increase in allowable loading (at constant span) which can be achieved by the inclusion of such metal wires or mesh in the present composite fioor structure. Non-composite corrugated metal flooring sections, for example, of the type described in U.S. Patent 1,855,- 082, produce a fioor which is unaffected in its loadsupporting characteristics by the presence or absence of such wires or mesh in the concrete. Such non-composite fioors are designed so that the steel decking supplies the entire load carrying requirements of the floor. The concrete is not taken into consideration and hence any modifications to the concrete component do not affect the load carrying capacity of the resulting floor.

The wires or mesh contemplated by the present invention are insufiicient to satisfy the requirements of the American Concrete Institute Code for shrinkage and temperature reinforcement of concrete generally. Such shrinkage and temperature reinforcement of concrete slabs is merely auxiliary to the principal metal reinforcement of reinforced concrete slabs. Hence the wires or mesh contemplated by the present invention (insufiicient to serve even as shrinkage or temperature reinforcement) does not create any reinforced concrete slabs in combination with the concrete.

It is therefore wholly unexpected that the use of such lightweight metal wires or mesh in the concrete layer of composite decking should so substantially alter the load carrying capacity of the resulting floor. The wires or mesh contemplated by the present invention are not the conventional reinforcing rods, wires or mesh which are familiar as tensile components of reinforced concrete slabs. Such prior art reinforcing rods, wires or mesh are required to sustain substantial tensile stresses in slabs where the concrete sustains compressive stresses. The present wires or mesh are required, moreover, only across the supporting beams, which further distinguishes the present concept from the prior art.

The amount of metal in the present wires or mesh is less than that specified as shrinkage and temperature reinforcement for concrete. Thus the metal wires or rods of the present invention are not adequate in size to serve as concrete reinforcement and are inadequate in size to serve even as shrinkage and temperature mesh for the concrete slab. In fact, the present metal wires or mesh are of such size that the concrete slab is allowed to develop cracks in the regions above the supporting beams.

The present invention, its objects and advantages will be more clearly understood by the following detailed description which refers to the accompanying drawings in which:

FIGURE 1 is a perspective illustration of a typical multi-story building utilizing composite fioor construction principles;

FIGURES 2, 3, 4, 5 are fragmentary perspective illustrations of typical corrugated metal decking sections of the type with which the present invention is concerned;

FIGURE 6 is a cross-section illustration taken along line VI-VI of FIGURE 1 illustrating the principles of the present invention; and

FIGURE 7 is a fragmentary illustration of metal wire mesh fabricated from steel wires.

Referring to FIGURE 1 there is illustrated a building 10 having vertical columns 11 and horizontal beams 12. Corrugated sheet metal decking 13 is provided above the beams 12 and is covered with a layer 14 of concrete which serves as a rigidifying floor component.

In order to achieve composite coaction between the sheet metal decking 13 and the covering concrete layer 14, the decking may be provided in the configuration shown in FIGURES 2, 3, 4, 5. The sheet metal decking shown in FIGURES 3 and 5 is of a special type known as metal cellular flooring.

Referring to FIGURE 2, the sheet metal decking section 19 is the type shown in Canada Patent 704,841. It comprises a metal sheet having alternating crests 20, valleys 21 and sloping webs 22. The crests 20 are provided with deformations 23 which are preferably elongated indentations as shown in FIGURE 2 although the deformations 23 may comprise elongated embossments or weld beads. In general the deformations 23 extend transversely to the axis XX of the metal decking section 19. A plurality of elongated deformations 24 is provided along the generally vertical webs 22 in a direction parallel to the axis XX. The deformations 24 are preferably embossments as shown but may be indentations or weld beads.

The metal cellular flooring section 28 shown in FIG- URE 3 corresponds to that described in Canada Patent 704,842 and includes a top sheet 29 and a bottom sheet 30 which are joined together by a plurality of spot welds 31. The top sheet 29 has alternating crests 32 and valleys 33 with intervening sloping webs 34. Deformations 35 are provided along the crests 32 corresponding to the deformations 23 discussed in connection with FIGURE 2. Elongated deformations 36 are provided along the sloping webs 34 corresponding to the elongated deformations 24 described in connection with FIGURE 2. The bottom sheet 30 is essentially flat. Lengthwise cells 37 are presented in the metal cellular flooring section 28 of FIGURE 3 to serve as raceways for distribution of electrical wiring and ventilation air. Each cell is defined by a portion of the bottom sheet 30, the undersurface of a crest 32 and the inner surfaces of adjoining vertical webs 34.

An alternative sheet metal decking section 39 suitable for composite coaction in a floor construction is illustrated in FIGURE 4 corresponding to that described in Canada Patent 704,839. The corrugated metal decking 39 of FIGURE 4 includes alternating crests 40 and valleys 41 with converging vertical webs 42. The vertical webs 42 converge downwardly from the sides of each of the crests 40 whereby the channels 43 which are formed between adjacent crests 40 are wider at the bottom along the valley 41 than along the top. These valleys 43 serve to confine a subsequently poured layer of concrete and maintain the hardened concrete in engagement with the corrugated decking sections 39. Accordingly with the configuration shown in FIGURE 4 there is no need for elongated deformations of the type identified by the numeral 24 in FIGURE 2.

Deformations 44, provided along the crests 40 correspond in function with the deformations 23 already described in connection with FIGURE 2. The deformations 44 are disposed transversely to the longitudinal axis XX of the corrugated decking section 39.

A metal cellular flooring section 49, shown in FIG- URE 5, corresponds with that described in Canada Patent 704,840. This metal cellular flooring section 49 comprises a top sheet 50 and a bottom sheet 51. The top sheet 50 corresponds with the corrugated sheet metal decking section 39 already shown in FIGURE 4 and includes alternating crests 52, valleys 53 and converging webs 54. The top sheet 50 is secured to the bottom sheet 51 by a plurality of spot welds 55 which are disposed along the valleys 53. Deformations 56, provided along the crests 52, correspond in function with the deformations 23 already described in connection with FIGURE 2. The converging webs 54 define alternating channels 57 between the adjacent crests 52. The channels 57 are wider at the bottom along the valleys 53 than along the top. The metal cellular flooring section 49 includes longitudinal cells 58 corresponding to the longitudinal cells 37 described in connection with FIGURE 3. The longitudinal cells 58 likewise may serve as raceways for distribution of electrical wiring or ventilation air.

The four decking sections shown in FIGURES 2, 3, 4, 5 all possess alternating crests and valleys with generally vertical webs therebetween. The sections have deformations in the crests extending transverse to the longitudinal axis of the decking. The sections possess hold-down means which comprises converging vertical webs (FIGURES 4, 5) or non-converging webs with linear deformations (FIGURES 2, 3).

The assembly of corrugated sheet metal decking sections according to the present invention is illustrated in FIGURE 6 wherein the sheet metal decking 13 is applied over horizontal building beams 12a, 12b, 120. The sheet metal decking 13 adopts a normal sag between the beams 12a, 12b, 12c. An effective composite floor construction can be obtained by utilizing as the decking 12 any of the sheet metal corrugated flooring sections shown in FIG- URES 2, 3, 4, 5 in combination with a covering layer of concrete as described in the above-mentioned Canada patents. However by providing metal mesh 15 within the concrete layer 14 above and across each of the horizontal beams 12a, 12b, 120, a striking increase in the load carrying capability of the resulting building floor is achieved. The metal mesh 15 is not connected to the corrugated metal decking 13, but instead, is displaced above the crests of that decking and below the top surface of the concrete 14. Metal reinforcing rods and mesh in concrete construction frequently are supported by small wire chairs which serve the sole purpose of elevating the metal reinforcing rods to a predetermined level above the bottom of a concrete form. Such wire chairs are contemplated for the purpose of elevating the metal reinforcing wires and mesh 15 above the ,crests of the corrugated metal decking 13 without introducing any structural connection between the mesh 15 and the decking 13.

The metal mesh 15 is similar to the familiar temperature reinforcement or shrinkage reinforcement material which is utilized in concrete structures, but contains less metal. Such shrinkage and temperature mesh is described in the American Concrete Institute Code, Section 807, 1963 edition, as follows:

807-Shrinkage and temperature reinforcement (a) Reinforcement for shrinkage and temperature stresses normal to the principalgcinforcement shall be provided in structural floor and roof slabs where the principal reinforcement extends in one direction only.

Such reinforcement shall provide at least the following ratios of reinforcement area to gross concrete area,

but in no case shall such reinforcing bars be placed farther apart than five times the slab thickness or more than 18 in.

Slabs where plain bars are used 0.0025 Slabs where deformed bars with specified yield strengths less than 60,000 p.s.i. are used 0.0020 Slabs where deformed bars with 60,000 p.s.i. specified yield strength or welded wire fabric having welded intersections not farther apart in the direction of stress than 12 in. are

used 0.0018

Thus where welded mesh is utilized for shrinkage and temperature reinforcement under the ACI Code, the metal cross-section is greater than.0.00l8 times the concrete cross-section. A lesser amount of wire mesh is contemplated for the present invention since development of concrete cracking is anticipated, is intended, and is not avoided.

Customary wire mesh is assembled by arranging individual Wires in a criss-cross basket weave pattern and welding the points of intersection to form a checkerboard like structure which is widely used as temperature and shrinkage reinforcement in concrete slabs. Such reinforcing mesh usually is available in various wire sizes and wire spacings. For the present invention, ordinary welded wire fencing is contemplated. Provision of the metal wires or mesh 15 in lesser quantities than the temperature and shrinkage reinforcement requirements of the American Concrete Institute Code achieves the present unexpected improvements. Such typical reinforcing mesh is illustrated in FIGURE 7 as including a number of generally parallel wires 61 which are interwoven with a second series of generally parallel wire 62. At each intersection 63 there is a weld connection between the wires 61, 62 to form a rigid open fabric 60 known in the construction industry as wire mesh.

EXAMPLES Two corrugated metal decking sections were tested to demonstrate the effect of metal mesh in the concrete covering layer for composite sheet metal corrugated decking above the supporting beams. Examples 2 and 4 correspond to this invention. Examples 1, 3, 5, 6 illustrate prior art.

Example 1.A metal cellular flooring section of the type shown in FIGURE 3 was tested. The bottom sheet 30 was fabricated from 16 gauge steel. The top sheet 29 was fabricated from 18 gauge. Each flooring section was 24 inches side-to-side and contained a total of 4 crests and hence 4 cells. The crest widthwas 3.875 inches. The valleys were 2.125 inches wide. The height of the crests above the valleys was 1.5 inches (inside dimension). The crest deformations 35 were indentations as described in occurred at a load of 1300 pounds per square foot (live June 18, 1965, and assigned to the assignee of this invention. The longitudinal web deformations 36 (FIGURE 3) were embossments as described in that patent application. The metal cellular flooring was supported on knife edges 12 feet apart, creating a span of 12 feet. The flooring section was covered with 2 /2 inches of concrete above the crests of the decking. The concrete had a compressive strength of 2610 p.s.i. Prior to pouring the concrete, a film of grease was applied to the metal decking to prevent formation of any adhesive bond between the decking and the concrete.

After the concrete had hardened, loads were applied to the flooring structure. Failure of the structure occurred at a loading of 475 pounds per square foot (live load). For this purpose the term failure is defined as the inability of the flooring assembly to accept additional load.

Example 2.-The corrugated metal decking sections described in Example 1 were provided in lengths of 14.5 feet. A section was supported on 6 inch WF beams at its ends and its mid-point. Thus the free span of the resulting floor was 7 feet 3 inches. The flooring was covered with a layer of concrete to a depth of 2.5 inches above the crests of the decking. A section of welded metal mesh 2 feet wide by 14.5 feet long, was applied to wire chairs above the decking before the concrete was poured. A film of grease was applied to the metal decking prior to pouring the concrete to prevent formation of any adhesive bond between the decking and the concrete. The concrete had a compressive strength of 2755 p.s.i. The welded metal mesh was in the form of 6 inch squares of No. 10 Wire having a diameter 0.135 inch, weighing 0.21 pound per square foot. The reinforcing mesh extended across the entire metal flooring section above the central beams. The mesh was one inch below the level of the concrete, i.e., 1.5 inches above the crests of the decking.

Upon application of the load, failure of the structure occurred at a load of 1300 pounds per square foot (live load).

Example 3.-The properties of ordinary unindented, unembossed metal cellular flooring are well known, being described in many catalogs as a result of numberless tests and actual installations. The properties of such sections are readily calculable. Calculations were carried out for an ordinary, unindented, unembossed metal cellular flooring section otherwise identical in dimensions to that of Example 1. Such section was assumed to be supported on 6 inch WF beams over a span of 7 feet 3 inches. The flooring was assumed to be covered with 2.5 inches of p.s.i. concrete above the tops of the crests. Upon application of load, failure will occur at a loading of 202 pounds per square foot (total load). The weight of the concrete and decking alone (dead load) is 43.3 pounds per square foot. Accordingly the calculated live load at failure is 158.7 pounds per square foot.

This example assumes a yield strength of the sheet steel at 33,000 psi, and also assumes that no adhesive bond develops between the concrete and the steel decking.

Example 4.Example 3 is duplicated assuming that welded metal mesh as described in Example 2 is applied to chairs over the supporting beam. There can be no change in the failure load for this test since the steel decking alone sustains the design load.

Example 5.The unindented, unembossed metal cellular flooring section described in Example 3 was assumed in a 12 foot span and covered with concrete to a depth of 2.5 inches above the crests. Failure of the specimen will occur at 74 pounds per square foot (total load) corresponding to 30.7 pounds per square foot (live load).

Again the yield strength of the steel sheet is assumed to be 33,000 p.s.i. and it is further assumed that no adhesive bond develops between the steel decking and the concrete.

Example 6.The failure of the 12 foot span also will occur at about 74 pounds per square foot when a quantity of welded metal mesh is provided as described in Example 2 above the corrugated metal decking, since the steel decking alone sustains the design loads.

The results of the foregoing examples are tabulated in the following Table I.

TABLE I.ALLOWABLE LOADS OF FLOORINGASSEMBLIES WITH CORRUGATED METAL DECKING AND CONCRETE [Allowable loading, p.s.f.]

The allowable loading values shown in Table I are determined, in accordance with conventional design practices, by applying a safety factor of 2.0 to the actual failure load. Those figures followed by an asterisk are the values obtained from the Examples 16. The values marked with double asterisks in Table I were obtained by conventional design calculations for the changes in span. That is, the value 393 was obtained by relating the value 237.5 (based on a 12.0 foot span) to the corresponding value for a span of 7.25 feet; similarly the value 390 was obtained by relating the value 650 (for a span of 7.25 feet) to a corresponding value for a 12.0 foot span.

It will be observed from study of Table I that the use of the reinforcing material with the present composite decking achieves a remarkable increase in the allowable loading of the resulting floor, namely, a 66% increase above that which could be achieved in the absence of the metal mesh. The metal mesh alone is not responsible for the change as is evidenced in Table I where the mesh contributes no improvement whatsoever to the ordinary corrugated metal decking.

GENERAL OBSERVATIONS The present improvement appears to be unique with those composite corrugated sheet metal decking sections having transverse deformations in the crests. Such corrugated metal decking sections are described in the aforesaid Canada Patents 704,839; 704,840; 704,841 and 704,842. In addition these composite sheet metal decking sections have a hold-down means which may comprise linear deformations along the vertical webs of the deck-ing as shown in FIGURES 2 and 3 or may comprise converging webs as shown in FIGURES 4 and 5. The present improvement in load carrying capability of composite flooring structures is not manifested with other types of corrugated sheet metal decking sections.

The unique feature of the described composite sheet metal decking results from (a) the provision of alternating crests and valleys having generally vertical webs therebetween; (b) the provision of deformations in the crests of the decking; (c) the provision of a hold-down means which may comprise deformations in the webs of the decking or converging webs; (d) the provision of metal wires or welded mesh in the covering concrete layer above the crests of the decking at least in the regions where the decking rests on horizontal beams.

We claim:

1. In a building having a composite floor construction including: horizontal beams; corrugated sheet metal decking having alternating crests and valleys and generally vertical webs converging from each of said crests toward the adjoining valleys and extending lengthwise between the said horizontal beams; a concrete covering over the said decking; deformations in the said crests of the said decking extending transverse to the longitudinal axis of said decking; said concrete conforming to the said deformations and said converging vertical webs; the improvement comprising:

metal wires in the said concrete spaced apart from the said decking above each of the said horizontal beams; the said metal wires being provided in a quantity which is insufficient to satisfy the requirements of the concrete for temperature and shrinkage reinforcement.

2. In a building having a composite floor construction including: horizontal beams; corrugated sheet metal decking having alternating crests and valleys and generally vertical webs therebetween and extending lengthwise between said horizontal beams; a concrete covering over the said decking; deformations in the said crests of the said decking; deformations in the said webs of the said decking; said concrete conforming to the said deformations; the improvement comprising:

metal wires in said concrete spaced apart from said decking above each of said horizontal beams, the quantity of said metal wires being insufficient to satisfy the requirements of the concrete for temperature and shrinkage reinforcement.

3. The improvement of claim 2 wherein the said metal wires comprise a welded metal mesh.

References Cited UNITED STATES PATENTS 602,274 4/1898 Sill 52-339 840,016 1/1907 Schlafly 52 450 1,073,906 9/1913 Kahn 52 577 1,170,743 2/1916 Evers 52 675 1,986,171 1/1935 Wilson 52 336 2,256,309 8/1944 Garbe 52 450 3,245,186 4/1966 Jentoft 52 334 3,283,458 11/1966 Gersovitz 52-260 FOREIGN PATENTS 278,186 10/1927 GreatBritain.

FRANK L. ABBOTT, Primary Examiner J. L. RIDGILL, JR., Assistant Examiner US. Cl. X.R. 52452

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