US3894370A

US3894370A - Reinforced structures incorporating strip deck material

Info

Publication number: US3894370A
Application number: US502245A
Authority: US
Inventors: Stephen Parazader
Original assignee: Individual
Current assignee: Individual
Priority date: 1972-10-04
Filing date: 1974-08-30
Publication date: 1975-07-15
Anticipated expiration: 1992-07-15

Abstract

A reinforced structure using settable material such as concrete to form a slab comprises a plurality of spaced, parallel loadbearing duct members of closed cross-section extending over and between at least two support surfaces of the structure and supported therefrom by a shear-resisting connecting means to constitute beam members. A thin strip extends beneath the duct members spaced therefrom and is connected to the duct members by shear-resisting connecting means, the strip serving as formwork for the layer of settable material while it is being poured, and reinforcement after it has set. The duct members and connecting means are completely embedded by the set material which enters the space between the strip and the duct members to provide a void-free layer between them. The duct members provide steel reinforcement for the set slab and also can constitute conduits or raceways for the provision of services through the resulting structure.

Description

[4 1 July 15,1975

United States Patent 1191 Parazader 783.64l 9/1957 United Kingdom...........ln...v 52/469 REINFORCED STRUCTURES INCORPORATING STRIP DECK MATERIAL Primary E.mminerAlfred C. Perham Attorney, Agent, or FirmStanley 1. Rogers V A a n mo ea hd wm so V I M 7 [22] Filed: Aug. 30 1974 [2]] Appl. No.: 502,245

Related U.S. Application Data parallel load-bearing duct members of closed [63] Continuatiomin-part of Ser. No. 295.025, Oct. 4,

1972, abandoned, which is a continuation-in-part of cross-section extending over and between at least two Ser No. I51

,340. June 9. l97l. abandoned.

support surfaces of the structure and supported therefrom by a shear-resisting connecting means to consti- [52] U.S. Cl. 52/173; 52/220; 52/335;

tute beam members. A thin strip extends beneath the 52/629 duct members spaced therefrom and is connected to E04f 17/08 the duct members by shear-resisting connecting means, the strip serving as formwork for the layer of settable material while it is being poured, and reinc r a e S t 0 M .W F

forcement after it has set. The duct members and connecting means are completely embedded by the set material which enters the space between the strip and the duct members to provide a void-free layer between them. The duct members provide steel reinforcement for the set slab and also can constitute conx m m E: 0 mm MA "H .lP m C s d mTmm m rTka mSRH D man '99 www 72 47 ll 6 l 5 mm Young FOREIGN PATENTS OR APPLICATIONS duits or raceways for the provision of services through the resulting structure.

52/220 12 Claims, 13 Drawing Figures SHEET FIG. 5

FIG. 4

FIG. 3

SHEET FIG. ll

z 202/3 FIG. 8 Zia FIG. 9

FIG. T

FIG

SHEET FIG. 13

REINFORCED STRUCTURES INCORPORATING STRIP DECK MATERIAL CROSS REFERENCE TO RELATED APPLICATION This application is a continuation-in-part of my application Ser. No. 295,025, filed Oct. 4, l972 now abandoned, which is in turn a continuation-in-part of my application Ser. No. l5 1 ,340, filed June 9, 1971 now abandoned.

FIELD OF THE INVENTION This invention is concerned with improvements in or relating to reinforced structures incorporating preformed strip deck material.

REVIEW OF THE PRIOR ART One of the commonest forms of reinforced structure now built comprises a sectional steel deck which is placed in position on a supporting steel framework, and over which a layer of concrete is applied. The set concrete and the steel deck co-operate together in what is known as composite action" to provide a floor structure for the space above and a ceiling structure for the space below. Designers now require the use of longer spans in order to obtain unobstructed floor space. The stronger steels and concretes now available assist in meeting this requirement, but it has also proven possible, by careful design of the deck material and the structure incorporating it, to provide a stiffer floor structure without reducing the total slab thickness, or conversely to provide the same stiffness by the use of a thinner floor slab. A stiffer slab will usually permit a reduction in the weight of the supporting steel framework and may also result in a reduction in the overall depth of the floor structure. These factors become important in multi-storey buildings, in that it may be possible to provide an additional storey of leasable space in a structure of given height.

Another important factor in the economical production of reinforced structures is whenever possible the reduction in the amount of relatively expensive, uncertain and inefficient field labour required, as compared with the amount of less expensive more efficient and easily controllable shop labour.

It is usually essential, especially in multi-storey structures, to provide service ducts or raceways in the floor or ceiling structure, through which the various services such as electricity, telephone, intercommunication, heating, air-conditioning, water, can be supplied and can be easily changed as occupancy of the building changes, or as changes are made in a particular area of the building. These services usually should be readily accessible from above, particularly in office-type buildings, so that the occupant can make any necessary changes without the need to enter the floor directly below. It is also of course necessary that the structure meet the minimum fire rating requirements of the appropriate authority.

An example of a way in which raceways have been provided is shown in US. Pat. No. 2,131,652, issued Sept. 27, l938 to H. H. Robertson Co., the floor structures shown therein comprising a substantially flat lower metal sheet over which is laid a corrugated upper metal sheet, with the overlaid sheets resting on suitable supporting members. The upper corrugations of the corrugated metal sheet are filled with concrete and form ribs on the underside of the resulting concrete slab, the sheets providing a permanent form upon which the concrete may be poured. The flat metal sheet co-operates with the lower corrugations to close them and thereby form the service ducts, the sheet also forming a ceiling plate which provides the space below with substantially flat metal ceiling which can be finished. The ducts may be entered from above through holes or openings drilled through the concrete or they may be entered from below through the ceiling sheets.

British Pat. No. 748,104, published Apr. I8, 1956, and issued to the Pre-stressed Concrete Company Limited, discloses building structures in which a preformed, pre-stressed plank is used for the subsequent casting in situ of floors or roofs. A plank is made by pouring concrete over a form consisting of mesh fabric, such as expanded metal, on which mesh fabric ducts are laid, or alternatively in which ducts have been formed integrally by bending up from the mesh fabric material. It is essential therefore for operation of this invention that the form is temporarily supported during its production prior to setting of the concrete, since it is inherently not self-supporting. The ducts are intended principally for the accommodation of prestressing cables, although the specification states at page 1, lines -88 that if all the ducts are not required for cables they provide convenient passages through which services can be run. When the ducts are separate from the mesh sheet they may be welded or wired thereto in well known manner and, in effect, also act as stiffening ribs for the mesh. It is intended that the concrete shall penetrate the mesh so that the ducts and mesh act as a reinforcement for the resultant plank. The specification states at page 1, lines 59-66 that if additional reinforcement is required transversely to the direction of the ducts, further ducts may be laid across those already in position and the concrete either poured over both sets of ducts at once or in two stages. These ducts, if provided, are therefore operative as tensile reinforcement for the slab, and there is no disclosure or teaching of these ducts provided in a manner such that they can operate as beam members resisting both compression and tensile forces. It will be seen that, if such further ducts are provided, the firstmentioned ducts constitute large voids interposed between the mesh and the further ducts. Moreover, the common method in the art of fastening additional reinforcement to a primary reinforcement is by means of wires, which type of connection is inherently not shear resisting; there is therefore no disclosure or teaching whatsoever ofa shear-resisting connection between the first-mentioned ducts and said further ducts, if provided.

DEFINITION OF THE INVENTION In accordance with the present invention there is provided a reinforced structure comprising a support structure providing at least two spaced support surfaces, a plurality of parallel, spaced, elongated, loadbearing duct members of closed cross-section extending between the said spaced support surfaces and over at least a portion of each of the said surfaces, shearresisting connecting means disposed between each support surface and the respective portion of each duct member extending thereover, whereby each duct member constitutes a beam member supported by the support surfaces, void-free shear-resisting connecting means connected to the duct members between the said portions which extend over the surfaces, a thin continuous strip extending beneath and spaced from the duct members over the space between the spaced support surfaces, and connected to the last-mentioned connecting means to be supported from the duct member to constitute formwork for a superimposed layer of settable material and reinforcement for the layer when set, and a void-free layer of set material that has been set on the strip as formwork therefor, the layer enclosing the duct members, the connecting means and filling the spaces between the strip and the undersides of the ducts.

DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view from above illustrating a particular preferred example of a single span of my new deck in roll form, being unrolled on to a support structure for the formation of a composite reinforced concrete floor/ceiling,

FIG. 2 is a similar view to FIG. 1, showing a multiple span rollable deck being unrolled on to a corresponding support structure,

FIGS. 3 to 6 and 8 are similar views to FIG. I, of a small portion thereof, to illustrate different forms of fastening means for fastening the duct members to the strip material,

FIGS. 7 and 9 are sections taken on the lines 7-7 and 99 respectively of FIGS. 6 and 8,

FIG. 10 is a section taken on the line I10 of FIG. 1 and showing the cross-section through a typical completed floor,

FIG. I I is a section similar to FIG. showing a mod ified form of fastening means,

FIG. I2 is a perspective view similar to FIGS. 1 and 2 of another preferred example wherein the sections of deck are placed on the support structure in flat form, and

FIG. 13 is a perspective view of a preferred example of deck as illustrated by FIG. 12, showing a modified form of raceway and illustrating the way in which the raceways are enclosed by the concrete.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring now especially to FIGS. 1 and 2, in the particular construction shown therein the resulting composite floor/ceiling is supported by spaced primary load-bearing members 12 (only one of which is shown), which in this embodiment comprise spaced I-beams. In other embodiments other forms of primary members can be used, such as spaced pillars or columns, walls and trusses. A plurality ofjoist or truss members 13 are supported at their ends by the primary members 12 in generally horizontal spaced parallel relation to one another, the upper flanges of these joist members providing respective substantially flat uninterrupted uppermost surfaces longitudinally of the joist members. Other forms of secondary joist members providing such an uppermost surface can of course be used.

Each joist 13 may in some examples be provided, by means of a preliminary shop operation under controlled conditions, with a plurality of upwardlyprojecting shear connector members 16 disposed in spaced distribution along the length of its surface 15. In this particular embodiment the connectors are illustrated as headed studs which are welded to the upper chord of the joist, the studs being staggered in relation to the joist centre line to avoid the junction at this position, and so that they are fastened alternately to different sections of the chord. Other forms of shear connector can of course be used.

The particular preferred form of the deck material of this invention illustrated by FIG. 1 comprises a relatively thin flat, uninterrupted, elongated, wiped-coat, galvanized steel strip 18 that when unrolled will lie flat along the surfaces 15 with its edge portions resting thereon. It is an important feature of this preferred form that the sheet metal used for the deck material is sufficiently thin that it will permit pre-rolling to roll form as illustrated. A plurality of elongated, rectangular closed cross-section duct members 19 are fastened at spaced intervals along the length of the strip, being disposed substantially parallel to each other. For convenience in description the top, bottom and side surfaces of the duct members are given the

references

190, 19c, 19b and 19d respectively. The members 19 are fastened to the strip by fastening means such that the bottom surface of each member is spaced a substantial distance from the upper face of the strip 18 to provide a space 20 for the entry of settable material between the duct members and the strip.

In this particular embodiment the fastening means comprise a plurality of Z-shaped members 21 having a flange 21a fastened, as by welding for example, to the strip 18, while the other flange 21b is fastened, as by welding for example, to the underface 190 of the respective duct member. The portion of each member 21 between the flanges is given the reference 21c. In this embodiment owing to the presence of the shear connector members 16 the width of the strip is less than the length of each duct member in the same direction, so that the ends of the duct members protrude beyond the edge portions of the strip, the amount of this protrusion being such that, as seen in FIG. I, the immediately adjacent registering ends of two duct members of adjacent pieces of strip deck material almost abut one another, so as to form a substantially continuous duct. In other embodiments the width of the strip may correspond more exactly with the length of the duct members.

A roll of the preformed flexible strip deck material can be hoisted into position at the ends of two adjacent joists l3 and is deposited on the members with the longitudinal axis of the roll transverse to the joists and par allel to the primary members 12. The spacing between the joists is predetermined to correspond to the width of the strip 18, so that its two edge portions reston the surfaces 15. Once accurately placed in position the material can be unrolled. as indicated by the arrow 22, simply by pushing by hand in the direction of the arrow 23. Preferably, the length of the roll is the same as that of the joists, so that only a single roll is required. With an unusually long span two rolls may be unrolled from opposite ends, the abutting ends being joined together, so that the carriage of decking units within the building structure is avoided. Adjacent strips are adjusted longitudinally the very small amount that is required to ensure that the duct members are accurately in register with one another and connectors, such as strips of suitable adhesive tape, may be applied around the closely adjacent ends to ensure that wet concrete cannot enter.

The construction of the reinforced structure is now completed by applying the usual upper wire mesh reinforcement 24 (see FIGS. I0 and 11) and pouring a concrete slab 25 to the required thickness, the strip 18 providing the necessary formwork. In some constructions it may be possible to eliminate the wire mesh reinforcement, for example when the fasteners are continuous and can perform the function of the mesh. The close engagement of the flat surfaces of the edge portions of the sheet and the joists ensure that the concrete cannot leak between them while in flowable condition. It is essential in pouring the slab that care be taken to completely fill the spaces 20, without the presence of voids therein, and techniques required for this purpose are well known to persons silled in the particular art.

It will be noted particularly that at least one shearresisting connecting fastening means 21 is interposed between each end of each duct member 19 which extends over the joist surfaces and the portion of the strip 18 that is resting on and is fully supported by the joist surfaces 15. The duct members thereby act as beams suporting via the connecting members the part of the strip that extends between the support surfaces 15. They thereby act as shear and beam supports for the dead load of the wet concrete while it is being poured and for construction loads during the pouring. The action of the intervening connecting members 21 is therefore to support the steel sheet in its suspension from the duct member acting as a beam over substantially its entire width at a large number of points, so that a relatively thin sheet (e.g. 0.030 inch for a slab of 5 inches overall thickness) can be used. The duct members provide a solid working plateform which can be walked upon by workmen if necessary till the concrete is poured, and also provide support for the reinforcing mesh 24 if used.

The duct members and the fastening connecting members are completely encased with concrete, as described above, and will bond to the concrete as it cures. The connecting means must in themselves have sufficient shear resistance to transmit the corresponding forces between the duct members and the sheet and permit the desired composite action to be obtained. if desired, additional mechanical connecting means, such as protruding lugs, depressions and ridges may be provided to ensure sufficient bonding. Such mechanical means will also increase the stiffness of the duct members. The mechanical action of the concrete encasing the duct members and connecting means, combined with the bond that is developed between the two materials results in a composite structural unit. The composite bond action between the concrete and the rigid duct members will resist transverse shrinkage stresses during the curing of the concrete, while longitudinal shrinkage stresses are resisted by the transfer of these stresses by the duct members to the bottom sheet. Once the concrete slab has been set the flat uninterrupted sheet constitutes the positive moment main reinforcement for the slab, carrying the tensile forces therein to the supporting joists, because of its continuous unbroken form it can also act in the longitudinal direction as an exceptionally effective temperature reinforcement for the slat. Moreover, again because of its uninterrupted form it distributes point load forces, caused for example by the movement of a heavy weight over the floor, over the slab and prevents cracking due to such forces.

Since the duct members are completely encased by the concrete the full thickness of the floor slab may be considered in determining the composite action of the floor slab with the supporting members, and not only the part of the slab that is above the ducts, as with the constructions referred to above, as disclosed in U.S. Pat. No. 2,131,652 and British Pat. No. 748,104.

Thus, there is a transfer of compressive stresses around the void constituted by the duct member due to its location within the body of the slab. This increases the effective thickness of the concrete and results in an increase in the effective area for consideration in determining the composite action. There is a consequential lowering of the centroidal axis of the composite section, with a corresponding increase in the section modulus of the bottom of the supporting member, giving an overall decrease in steel stresses and greater stiffness, resulting in less deflection and less vibration. This may be contrasted with the conventional prior art deck described above, which permits only the concrete over the metal deck to be considered in determining the extent of this composite action. Such conventional deck required that the shear connectors extend above the top of the deck, which results in the development of a moment between the top of the supporting member and the effective concrete, causing the cells of concrete formed by this type of deck to rotate under the load.

The location of a layer of concrete under the duct members prevents uplift of the concrete slab away from the deck, the mechanical action between the concrete and the fastening members, the bottom sheet and the duct members transferring the tension stresses between the latter two which therefore both act as positive reinforcements.

For convenience in terminology the term duct member alone is used in the claims, and it will be understood by those skilled in the art that such term includes, pipes, tubes, and like members.

In the embodiment particularly described and shown the duct members are intended for electrical service, and therefore are shown as of conventional closed rectangular transverse cross-section, since supplementary equipment for use with such ducts are readily commercially available. However, other closed cross-sections may also be used, such as round or square tube. It is found that the improvements in performance to be obtained by use of the new deck material are such that it is also preferred to use duct members that are not necessarily required to act for the carriage of services. Such non-service duct members may be of same or similar configurations, but the gauge of metal may be reduced substantially. Different materials may also be used.

A duct member intended for electrical service must usually be of a minimum thickness specified by local regulations, and it is therefore contemplated that deck material may be provided in which different types of duct members are provided along the length thereof in order to achieve maximum flexibility and/or economy of material. Thus, it may be arranged that only each third or fourth duct member is particularly suitable for electrical service, while the intervening members are of substantially reduced thickness and/or cross-section. It is also contemplated that different duct members may be provided, depending upon their specific function, for example, they may be successive groups of four, one of which is for electrical service, another is for telephone, a third is available for air conditioning service, and the remaining member is for water, gas, or some other type of service.

It is also therefore a particularly useful feature that the design of the duct members is independent of the design of the bottom sheet. This may be contrasted with the conventional deck wherein the bottom sheet is part of the duct member and must usually be of minimum thickness, greater than would otherwise be required, to meet the associated regulations This blending of the duct members is possible in the shop rather than in the field and may be contrasted with a conventional deck wherein comparable very limited blending can only be obtained by alternating the use of electrical type and a non-electrical type deck material.

In a particular preferred embodiment where all of the duct members are suitable for electrical service the strip deck material is 4 or 5 feet wide and the duct members are each of 6 inches width and may be from 1 /2 to 3 inches in height, in increments of one-half inch, the height chosen being dependent upon the span of the deck material, the spacing of the duct members and the load on the deck during construction. The duct members may be 12 inches, 15 inches or inches from one another. The lower surface of the duct members will usually be spaced about lk inches to 2 inches from the upper surface of the sheet metal strip 18.

Since the service ducts are completely encased in concrete material they are protected from all sides, and this may be contrasted with the prior art deck materials described, in which only a light gauge sheet metal layer separates the duct from the floor area or ceiling space. The layer of concrete provided by the deck material of this invention in the space 20 provides greater protection from fire, the provision of voids within the slab also acting to insulate the slab more effectively against the transfer of heat through it. Therefore the fire rating of the structure is greater, or conversely the same fire rating is obtainable with a smaller overall floor thickness. This greater protection results in less damage in the event of small localized fires, and also decreases the possibility of transfer of damage to other areas within the building. For the same reason sound transmission is reduced.

The width of the sheet 18 is made such in relation to the spacing of the joists, and to the disposition of the connectors 16, that the edges of the sheet can be spaced from the connector members to ensure that they are completely embedded in the concrete slab by means of an uninterrupted strip of concrete which surrounds them. This arrangement is important to ensure that the connector members and the deck material do not interact to apply torsional forces that can crack the concrete deck.

Since the deck material is unrolled it is important that the connectors 16 be accurately located transversely of the joists 13, so that an unobstructed path is left for the unrolling, and this can readily be achieved by the use of jigs in the pre-attaching operation. it is also important that the duct members be accurately located along the length of the strip so that adequate registration of adjacent members is obtained. As the deck is unrolled the edge portions thereof resting on the joists may be fastened thereto, for example by spot welding or suitable clips. in some floor constructions it may not be necessary to provide shear connectors, for example the above-mentioned welding of the deck to the beam members providing sufficient shear horizontal resistance.

Another application of the strip deck material of the invention is in bridge construction to provide permanent formwork and reinforcing for the bridge slab. In this application the duct and fastening connecting members would be larger and heavier due to longer spans and heavier loads. Also, the bottom sheet would be heavier and could be either flat or corrugated for increased strength and stiffness. The connecting members for each duct may, for example, comprise a longitudinal web fastened at its upper edge to the underside of the duct while its lower edge is fastened to the strip, shear-resisting cross-webs also being provided at intervals transverse to the longitudinal webs and shaped to fit around the duct periphery. The cross and longitudinal webs are joined together at their junctions; the cross webs are also fastened to the duct and to the strip as required in order to provide the necessary horizontal shear resistance. The duct members create large voids within the slab thereby reducing the dead load of the slab. Once the concrete has set, composite action between the concrete and deck is achieved through the mechanical action of the concrete and the shearresisting connecting members and also through the chemical bond developed between the concrete and duct members, connecting members and bottom sheet.

The embodiment of FIG. 2 differs from that of FIG. 1 only in that the duct members 19 are continuous over a plurality of elongated strips disposed side by side and also continuous over a plurality of support surfaces 15. Thus at least two strips are disposed with the direction of elongation parallel to one another, while each duct member is of a length such as to extend uninterruptedly over all of the strips. Nevertheless such a structure can readily be rolled as shown, and easily unrolled when once hoisted into position on the support structure. The immediately adjacent edges of each adjacent two strips are spaced from one another to clear the shear connectors 16. With a deck material in accordance with the invention it is possible, for example, to provide as many as six strips side by side, each strip being of width 5 feet and of length 40 feet, so that an area of approximately 1,200 sq. ft. can be applied as a single roll.

Various shapes and types of fastening means 21 may be employed for connecting each duct member 19 to the strip 18 with the undersurface 19c or its equivalent spaced from the adjacent strip surface, so as to provide the space 20 therebetween, and some examples only are shown in FIGS. 3-11. Preferably the concrete extends completely under the duct members but an equivalent action can be obtained if the space 20 permits only partial interposition thereof, the minimum required for beneficial action to be obtained being readily calculable by those skilled in the art.

Generally the fastening means members should have a truss-like or suspended configuration and be capable of transferring horizontal stresses between the duct member, metal strip and the concrete, after the concrete is poured and set. Moreover they should provide adequate lateral stability to the duct member, so that they will readily withstand the construction loads, workmen walking on them, and the load of the wet concrete applied thereto while the floor slab is being poured. The members may be mechanically deformed in shape or otherwise provided with means which mechanically increase the bond with the concrete. Such bonding action combined with the mechanical action of the concrete completely encasing these members enables full transfer of the stresses between the duct members, bottom sheet and the concrete.

In the embodiment illustrated by FIG. 3 the fastening member 21 is of what is called zig-zag configuration and is fastened adjacent the valleys 21a thereof to the metal strip, while the peaks 21b thereof are fastened to the underside 190 of the rectangular-configuration duct member. It will be noted particularly that at the ends of the support member a vertically extending portion 21d is provided, in order to ensure full transfer of the forces applied to the duct member I9 to the edge portions of the strip that are fully supported by the joists 13.

In the embodiment of FIG. 4 the support member for each duct member comprises two zig-zag shaped rods disposed one on each side of the respective duct member, the valleys being fastened to the sheet 18, while the crests are fastened to the side walls 19b and I9d. Vertical end portions 21d are also provided. These rods may be deformed to increase their bond with the surrounding concrete.

In general the specific shape, arrangement and disposition of the fastening members will be determined by factors such as economy of material, ease of fabrication of the members and ease and economy in fastening them accurately and securely in position.

In the embodiment of FIG. 5 the fastening members comprise a plurality of U-shaped

brackets having flanges

21a and 21b facing the same way, the upper flanges 2112 being fastened to the flat underface 19c, while the lower flange 21a is fastened to the strip.

In the embodiment of FIGS. 6 and 7 the members may comprise Z-shaped brackets as shown in solid lines. Instead they may comprise brackets of so-called top-hat" shape as shown in the combination of solid and broken lines, the brim" members 210 being fastened to the strip 18, while the hat top" 21b is fastened to the face 19d. Similarly, in the embodiments of FIGS. 8 and 9 the support members may be of L-shape, as shown in solid lines, or instead of deep top-hat" cross-section, as indicated by the solid and broken lines, in this case the hat-top 21b being fastened to the face 19a.

FIG. 10 shows the connecting means of FIGS. 1 and 2, and shows also the upper reinforcement mesh 24 and the complete cement slab 25. In the embodiment of FIG. 11 each bracket member 21 is of greater width in the direction of elongation of the strip at the junction of the flange 21a and the body 21c than at the junction of the flange 21b and body 210, such a construction making for easier access in fastening and also providing increased transverse stability. The unsupported span of the bottom strip between the duct members also is reduced.

In the preferred example of FIGS. 12 and 13 the sections of deck material are of flat form and are placed on the joist surfaces 15 with the length of the strip 18 parallel to the length of the duct members 19 and transverse to the length of the joists 13. In the particular embodiment illustrated the strip is of sufficient length to extend continuously over several spans, and the duct members also are continuous and extend over the same number of spans. A complete floor is assembled by laying several assembled sections side by side with their adjacent edges 18a abutting one another; these abutting edges may be turned upward as illustrated and arranged to interlock with one another or to be crimped together in any suitable known manner along their length. As illustrated by FIG. 13 the duct members may have at least the

faces

19a and 1% longitudinally corrugated to increase their longitudinal rigidity.

The fastening means of this embodiment also are Z- shaped members, as with the embodiments of FIGS. 1, 2, IO and 11, but each is of sufficient length to extend the full width of the strip, and therefore acts to fasten more than one duct member (three in this embodiment) to the strip 18. In other embodiments only some of these members may be continuous across the strip. As with the other embodiments care is taken to ensure that fastening members are interposed between each duct and the underlying portions of the strip 18 that are resting on the joist surfaces 15, and in this embodiment these are illustrated as being of the top-hat shape described with reference to FIG. 7. Subsequent to mounting the sections on the joists the feet of these top-hat fastening members are welded through the strip 18 to the joist surfaces, so that they act as integral shear connectors, avoiding the need to provide the special separate connectors 16 of the previously described embodiments and thereby considerably simplifying the assembly and decreasing its cost. This feature can also be used with the other embodiments of the invention.

At the present time sheet steel is readily available in widths of only about 5-6 feet, so that the fabrication of a coil having a width of say 15 feet would involve preedge welding together three separate strips. With the construction of FIG. 12 separate strips of up to about 45 feet length and 56 feet wide can easily be provided, the duct members 19 holding the strip flat in the longitudinal direction, and the continuous fastening members 21 at least assisting in holding it flat in the transverse direction, to permit easy handling. It will be noted that each strip is of substantially the width of the steel strip available, less the small amount required for the narrow upturned edges 18a, that is to say nearly 5-6 feet, whereas the loss in width caused by rolling to provide the prior art corrugated sections results in strips that are only about 2-3 feet wide. The welded wire mesh used in prior art corrugated constructions is not needed except perhaps at joints of adjacent sections of deck.

The deck of this invention may be produced in a relatively small manufacturing area with relatively inexpensive equipment, such as spot welding equipment, unlike the conventional prior art deck described which requires large manufacturing areas and expensive roll forming equipment. For example, the sheet steel can be supplied in rolls which are unrolled at a specific location at which the duct members are installed, and then immediately stacked or recoiled into compact form to await transportation to and installation on the site. Any length of deck can be provided, depending on the length of completed strip or the diameter of the roll that can be handled efficiently. For example, a section of deck 40 feet long can be rolled into a coil having a diameter of 4-5 feet.

I claim:

I. A reinforced structure comprising:

a. a support structure providing two spaced support surfaces,

b. a plurality of parallel, spaced, elongated, loadbearing duct members of closed cross-section extending between the said spaced support surfaces and over at least a portion of each of the said surfaces,

c. shear-resisting connecting means disposed between each support surface and the respective portion of each duct member extending thereover, whereby each duct member constitutes a beam member supported by the support surfaces,

d. void-free shear-resisting connecting means connected to the duct members between the said portions which extend over the surfaces,

e. a thin continuous strip extending beneath and spaced from the duct members over the space between the spaced support surfaces, and connected to the last-mentioned connecting means to be supported from the duct member to constitute formwork for a superimposed layer of settable material and reinforcement for the layer when set,

f. and a void-free layer of set, settable material that has been set on the strip as formwork therefor. the layer enclosing the duct members which thereby act as reinforcement for the layer when set, the layer also enclosing the connecting means and tilling the spaces between the strip and the undersides of the duct members.

2. A structure as claimed in claim 1, wherein the firstmentioned connecting means are disposed at the edges of the respective strip and are fastened to the duct members and the strip.

3. A structure as claimed in claim 1, wherein the said thin strip is of sufficient longitudinal flexibility to be rolled into the form of a roll having a longitudinal roll axis, the duct members being disposed with their respective directions of elongation parallel to the said roll axis.

4. A structure as claimed in claim 3, comprising at least two elongated thin strips disposed with their directions of elongation parallel to one another, each duct member being of a length to extend uninterruptedly over all of the strips.

5. A structure as claimed in claim 1, wherein the ends of each duct member extend beyond the immediately adjacent edges of the strip.

6. A structure as claimed in claim 1, wherein the strip is of elongated form, the duct members are disposed with their directions of elongation parallel to the direction of elongation of the strip, and at least one of the connecting means extends continuously across the width of the strip to connect a plurality of the duct members to the strip.

7. A structure as claimed in claim 1, wherein the connecting means connecting each duct to the strip comprise at least one member of zig-zag configuration fastened adjacent the valleys thereof to the strip and adjacent the peaks thereof to the respective duct member.

8. A structure as claimed in claim 7, wherein the said zig-zag connecting means comprise at least one bent thin sheet member interposed between the sheet and the respective duct member.

9. A structure as claimed in claim 1, wherein the said connecting means comprise a plurality of spaced members of top-hat cross-section having the brim members fastened to the strip and the hat top fastened to the duct member.

10. A structure as claimed in claim 1, wherein the said connecting means comprise a plurality of spaced bracket members interposed between the strip and the respective duct member and fastened thereto.

11. A structure as claimed in claim 10, wherein each bracket member is of greater width in the direction of elongation of the strip at its junction with the strip than at its junction with the respective duct member.

12. A structure as claimed in claim 1, wherein the duct members are longitudinally corrugated to increase the longitudinal rigidity thereof.

Claims

1. A reinforced structure comprising: a. a support structure providing two spaced support surfaces, b. a plurality of parallel, spaced, elongated, load-bearing duct members of closed cross-section extending between the said spaced support surfaces and over at least a portion of each of the said surfaces, c. shear-resisting connecting means disposed between each support surface and the respective portion of each duct member extending thereover, whereby each duct member constitutes a beam member supported by the support surfaces, d. void-free shear-resisting connecting means connected to the duct members between the said portions which extend over the surfaces, e. a thin continuous strip extending beneath and spaced from the duct members over the space between the spaced support surfaces, and connected to the last-mentioned connecting means to be supported from the duct member to constitute formwork for a superimposed layer of settable material and reinforcement for the layer when set, f. and a void-free layer of set, settable material that has been set on the strip as formwork therefor, the layer enclosing the duct members which thereby act as reinforcement for the layer when set, the layer also enclosing the connecting means and filling the spaces between the strip and the undersides of the duct members.

2. A structure as claimed in claim 1, wherein the first-mentioned connecting means are disposed at the edges of the respective strip and are fastened to the duct members and the strip.