WO2012072671A1

WO2012072671A1 - A composite beam flooring system

Info

Publication number: WO2012072671A1
Application number: PCT/EP2011/071361
Authority: WO
Inventors: Maurice O'brien; Anne O'brien; Terry Nolan
Original assignee: Maurice O'brien; Anne O'brien; Terry Nolan
Priority date: 2010-11-30
Filing date: 2011-11-30
Publication date: 2012-06-07

Abstract

A concrete flooring system (10) for use in the construction of floor/roof levels within framed buildings and which provides improved levels of stiffness for a relatively shallow depth when using prefabricated slabs or steel decking with in situ concrete in the construction of the floor/roof levels, the system comprising at least a pair of prefabricated slabs (12); a pair of beams (14) in parallel spaced relationship such as to define a inter-beam space (20) therebetween, each beam supporting a respective slab at an edge of the slab, an array of reinforcing members (22) located within and/or overlying the inter-beam space, and concrete filling the inter-beam space and encasing the array of reinforcing members and covering the prefabricated slabs.

Description

A Composite Beam Flooring System

Field of the invention

This invention relates to a composite beam flooring system, in particular a concrete flooring system for use in the construction of floor/roof levels within framed buildings and which provides improved levels of stiffness for a relatively shallow depth when using prefabricated slabs or steel decking with in situ concrete in the construction of the floor/roof levels.

Background of the invention In the construction of framed buildings, for example a steel framed building as illustrated in Figure 1, the conventional approach is to initially erect a steel framework of vertical columns spanning which are grids of horizontal beams that form the underlying support for each floor of the building. Each column is normally connected to an adjacent column by a single primary beam extending co-planar with the respective columns. Extending between adjacent primary beams are an array of secondary beams. Together these horizontal beams form a rectangular grid that supports the floor slabs of the building. The slabs may be precast concrete or corrugated steel decking that is placed on the steel beams to act as shuttering for a poured in situ concrete floor. The spacing of the secondary beams is determined by the loading on the slab, the thickness of reinforcing steel in the slab and whether or not the slab will have props under it when the concrete is poured. The decking/shuttering may be placed on top of the flange of the beams or on the bottom flange.

The main beams may have limited connectivity at the columns and the floor may also have limited connectivity across the beams resulting in large deflection at the centre of the floors. One method of dealing with the issue is to increase the thickness of the floor in order to reduce deflection, although this increased structural depth can give unacceptable or an uneconomical depth of floor.

In many buildings it is necessary to have a relatively thick layer of poured concrete, in order to ensure minimum deflection/vibration of the floors of the building during use, which vibration is an inherent and essentially unavoidable occurrence due to footfall of the occupants within the building. This is particularly important in buildings such as hospitals, where floor vibration, for example in an operating theatre, must be minimised for obvious reasons. However, for a given height of building the use of thicker floors will reduce the usable space within the building. In addition, the use of a fully poured concrete floor gives rise to delays in the length of time taken to construct the building, as each poured floor must be allowed by cure before additional work can commence.

The present invention provides a system and method of introducing continuity at the columns and into the floor where it crosses the beams, resulting in a floor with reduced deflection and thickness, which can be erected with the speed of a framed system of construction.

Summary of the invention

According to a first aspect of the present invention there is provided a composite beam flooring system for a framed building, the system comprising at least a pair of prefabricated slabs; a pair of beams in parallel spaced relationship such as to define a inter-beam space therebetween, each beam supporting a respective slab at an edge of the slab; an array of reinforcing members located within and/or overlying the inter-beam space; and concrete filling the inter-beam space and encasing the array of reinforcing members and covering the prefabricated slabs. Preferably, the building comprises at least a pair of substantially vertical columns spaced from one another, the system comprising a support pad on each of a pair of opposed outer faces of each column, each beam extending between at least a pair of the columns and being seated on at least one support pad at each column.

Preferably, the reinforcing members comprise an array of reinforcing members within the inter-beam space and an array of reinforcing members overlying the inter-beam space and extending outwardly to overlie the edge of each slab.

Preferably, at least some of the reinforcing members within the inter-beam space pass through the columns which extend vertically through the inter-beam space.

Preferably, each beam supports the respective slab on a side of the beam opposite to that on which the inter-beam space is defined.

Preferably, the beams comprise I-beams.

Preferably, each I-beam comprises an upper flange, a web, and a lower flange, the lower flange having a greater width than the upper flange.

Preferably, the lower flange has a stepped reduction in thickness between the web and an edge of the flange.

Preferably, the flooring system comprises permanent shuttering positioned between the pair of beams such as to define a base of the inter-beam space. Preferably, the shuttering becomes an integral part of the beam.

Preferably, the shuttering comprises one or more substantially flat plates having stiffening depressions formed therein. Preferably, the shuttering comprises a lip provided along each of a pair of opposed edges of the shuttering. Preferably, the flooring system comprises an array of couplings formed integrally with each slab adjacent the edge thereof, and to which are secured some of the reinforcing members which overlie the channel.

Preferably, the couplings are in the form of hooks cast into the slabs, the respective reinforcing members passing through the hooks.

Preferably, the slabs comprise pre-cast concrete.

Preferably, each slab comprises a shoulder formed along the edge of the slab, and into which shoulder the edge of the respective beam is received.

According to a second aspect of the present invention there is provided a method of constructing a composite beam flooring system in a framed building having vertical columns, the method comprising the steps of:

• Securing a pair of beams between at least a pair of columns with one beam on either of a pair of opposed sides of the columns such as to define a inter-beam space between the beams;

• Supporting an edge of a respective slab on each of the pair of beams;

• Positioning reinforcing members within the inter-beam space and above the inter-beam space to overlie the edge of each slab; and

• Pouring concrete to encase at least the overlying reinforcing members to provide continuity across the pair of slabs.

Preferably, the method comprises passing the pair of beams past a plurality of the columns in order to achieve continuity of the beams at said columns.

Preferably, the method comprises, in the step of positioning reinforcing members, positioning a first set of reinforcing members to lie in a direction substantially parallel with a longitudinal axis of the beams, and positioning a second set of reinforcing members to lie in a direction substantially transverse to the longitudinal axis of the beams. Preferably, the method comprises the step of passing at least some of the first set of reinforcing members through the columns to achieve continuity of the reinforcing members at said columns.

Preferably, the method comprising the step of positioning shuttering between the pair of beams such as to define a base of the inter-beam space.

Preferably, the method comprises, in the step of pouring the concrete, filling the inter- beam space with poured concrete in order to encase the reinforcing members within the inter-beam space.

Preferably, the method comprises, in the step of securing the pair of beams, fixing a support pad on each of the pair of opposed faces of each column, and seating each beam on a support pad at each column.

Brief description of the drawings

Figure 1 illustrates a partially constructed prior art steel framed building; Figure 2 illustrates an overall perspective view of a flooring system according to an embodiment of the present invention;

Figure 3 illustrates a perspective sectioned view of the flooring system according to an embodiment of the present invention;

Figure 4 illustrates an end view of the flooring system shown in Figure 2; Figure 5 illustrates a perspective view, from beneath, of the flooring system shown in Figures 2 to 4; Figure 6 illustrates a perspective view of the flooring system shown in Figures 2 to 4, in which precast slabs forming part of the system have a shoulder or notch formed in a lower edge; and

Figure 7 illustrates a perspective sectioned view of the flooring system shown in Figures 2 to 4, in which a precast slab is disposed in an inter-beam space as an alternative formwork for in situ poured concrete.

Detailed description of the invention

Referring now to Figures 2 to 7 of the accompanying drawings, there is illustrated a flooring system, generally indicated as 10, for use in the construction of buildings, in particular multi-storied framed buildings such as conventional steel framed buildings. The flooring system 10 utilises a composite beam assembly in place of the conventional single beam arrangement of the prior art, to achieve continuity at the columns and continuity across the beams thereby significantly reduce deflection of the floor, thereby allowing the depth of the flooring system 10 to be reduced. The flooring system 10 of the present invention also embodies a number of additional advantages as set out below. The flooring system 10 comprises an array of precast concrete or steel decking slabs 12 to form each floor of the building, which slabs 12 are secured between arrays of horizontal beams 14. The beams 14 themselves are secured between adjacent vertical columns 16 on support pads 18 secured on opposed faces of each column 16, as will be described in greater detail hereinafter. Unlike in conventional steel frame construction techniques, each column 16 carries a pair of eccentrically mounted beams 14, each pair of which therefore defines an inter-beam space 20 therebetween. In use, and again as will be described in greater detail, each inter-beam space 20 is provided with an array of reinforcing members 22 both therein and overlying the inter-beam space20, which are then encased in poured concrete which fills the inter-beam space20 such as to create a composite beam construction which provides continuity between the slabs 12. In addition, the beams 14 and reinforcing members 22a preferably extend continuously past each column 16 as opposed to terminating at each column 16 as in the prior art, thereby providing continuity at the columns. The reinforcing members 22 may be connected using continuity bars (not shown) as is standard practice for reinforcing bars. This continuity both across and along the floor ensures a significant reduction in deflection of the floor.

Looking now in detail at the method of constructing a building using the flooring system 10 of the present invention, initially the array of vertical columns 16 are fixed in position using conventional construction techniques. Then at fixed vertical intervals along each column 16, at the level at which each floor is to be located, a pair of the support pads 18 are secured to each column 16, one pad 18 being secured on each of two opposed faces of the column 16 as illustrated. The pads 18 may be secured to the column 16 in any suitable fashion, for example using welding, bolting, riveting, or any combination thereof. The pads 18 are also preferably formed from steel, and may be of any suitable shape/configuration. It is envisaged that some or all of the pads 18 could be replaced with, or effectively extended to form, a beam (not shown) which will thus extend in a direction transverse to the beams 14, such as to contact and be secured to an adjacent column (not shown). Such an arrangement may be required for the structural integrity of the building. In this configuration either end of such a beam can then be said to form the pads 18 on which the beams 14 are supported.

A parallel pair of the beams 14 are then laid between adjacent columns 16 on the pads 18. As mentioned above it is preferably that each beam 14 is of a length that spans a number of the columns 16 and most preferably the joints between beams 14 is at or close to the points of contra flexure. The beams 14 are preferably provided with a lower flange 24 having a greater width than an upper flange 26, which are connected together in conventional fashion by a web 28. The lower flange 24 then sits on the upper face of the pads 18, and again may be secured thereto in suitable fashion, for example using welding, bolting or riveting. By providing the lower flange 24 with a greater width than the upper flange 26 it is possible to conveniently lower each slab 12 into position between the beams 14 on which the slab 12 will be supported without fouling the respective upper flanges 26. The use of a pair of the beams 14, one on either side of each column 16, as opposed to the conventional use of a single beam between columns, allows the height of the beams 14 between the upper and lower flanges 26, 24 to be reduced over the conventional single beam construction. As will be described in detail hereinafter, this allows the overall thickness of the floor formed by the flooring system 10 to be reduced, thereby increasing the available interior space of the building. An edge 30 of each slab 12 is thus seated and supported on the outwardly facing side of the lower flange 24 of the beams 14 as shown. Due to the provision and width of the inter-beam space 20 between each pair of beams 14, the overall length of each of the slabs 12 between opposite edges 30 of the same slab 12 is reduced with respect to a conventional flooring system.

At this point in the construction of the flooring system 10, shuttering 32 is positioned between the pair of beams 14 such as to define a base to the inter-beam space 20. The shuttering 32 is preferably in the form of sheets of steel provided with impressions or protrusions 34 therein in order to increase the stiffness of the shuttering 32. A lip 36 is also provided along either edge of the shuttering 32 that in use receives an edge of the lower flange 24 of each of the beams 14. This ensures that the underside of the shuttering 32 is then flush with the underside of the lower flange 24, for reasons set out hereinafter. The shuttering 32 is preferably provided in short discrete sections, with multiple sections then being laid in end to end engagement to define the base of the inter-beam space 20. The inter-beam space 20 is then filled with an array of the reinforcing members 22, which preferably take the form of conventional steel reinforcing bars. These may be laid in a cross lattice arrangement as illustrated, or in any other suitable fashion. In the preferred embodiment illustrated the reinforcing members are laid in a first set 22a extending in a direction substantially parallel with a longitudinal axis of the beams 14 and a second set 22b extending in a direction substantially transverse to the longitudinal axis of the beams 14.

Additional reinforcing members 22c and 22d are then laid above and across the width of the inter-beam space 20, with the second set 22d being dimensioned to extend beyond each of the beams 14 such as to overlie the pair of opposed slabs 12 as illustrated.

Suitably positioned holes (not shown) may be drilled through the column 16 in order to allow the reinforcing members 22c to pass directly through the column 16 such as to provided continuity at the columns 16. Alternatively the reinforcing members 22c may be cut to length to fit exactly between the columns 16 and be attached, for example by welding or the like, to each of the columns 16.

At this point concrete is poured into the inter-beam space 20 to fill same, with the concrete being poured until the reinforcing members 22c and 22d located above the inter-beam space 20 are encased in concrete. In this way simultaneously a layer of poured concrete is provided above each of the precast slabs 12 such as to form a skin thereon. As an alternative to the shuttering 32, as illustrated in Figure 7, a precast reinforced concrete slab 40 may be located within the space 20, which slab 40 will serve as shuttering when pouring the concrete used to encase the reinforcing members 22 above the inter-beam space 20. The slab 40 may contain some of the reinforcing members 22.

Once set, the pair of beams 14, along with the reinforcing members 22, form a composite beam in which the reinforcing members 22 encased in concrete knit the opposed pair of slabs 12 together, thus providing continuity widthways between the slabs 12 and lengthways between the columns 16 and thus significantly reduces deflection of the slabs 12. This, in combination with the shorter and therefore stiffer slab 12, has the effect of shifting upwardly the natural resonant frequency of the slab 12 in comparison to a conventional slab of greater length. This increases the resonant frequency of the slab 12, whilst simultaneously reducing the thickness of the flooring system 10 over conventional flooring systems.

Referring to figure 6, the flooring system 10 is shown in which the edge 30 of each of the slabs 12 is provided with a shoulder 38 for receiving the lower flange 24 of the respective beam 14. The depth of the shoulder 38 is such that once in position, the underside of each of the slabs 12 is flush with the underside of the lower flange 24 and the shuttering 32, which both greatly improves the finished appearance of the flooring system 10 for occupants of the building, and also provides a number of functional benefits. For example when services such as air-conditioning, electrical services, and the like are being fitted, the lack of any stepped change at the transition between the underside of each slab 12 and the inter-beam space 20 of the flooring system 10 reduces significantly the complexity of fitting such services. The continuous surface on the underside of the flooring system 10 also greatly eases the application of a coating of fire retardant material to the underside of the beams 14 necessary to protect the steel form work which is the backbone of the steel frame building.

To further increase the safety of the flooring system 10 in the event of a fire, couplings in the form of hooks (not shown) may be precast into the upper surface of each of the slabs 12, adjacent the edges 30 thereof. Then during construction of the flooring system 10 the reinforcing members 22d that overlay the inter-beam space 20 and extend outwardly over the edges 30 of the slabs 12 can be passed through these hooks before being encased in concrete. In this way, if parts of the steel structure supporting the flooring system 10 where to weaken or fail, adjacent slabs 12 would still be secured together, thereby greatly reducing the likelihood of adjacent slabs 12 separating and collapsing downwardly. It will therefore be appreciated that the flooring system 10 of the present invention provides a construction system which greatly reduces the deflection and vibration in order to increase the comfort specification of the building, while at the same time increasing the occupational space of the building and reducing the construction time 5 necessary to erect the building. In addition the composite beam flooring system 10 provides an economical and speedily erected system for use in the construction of framed buildings.

The following table provides a comparison between the system 10 of the present

1 0 invention and conventional flooring systems currently in use. In particular the table shows data from conventional systems used in hospitals with a span of 7.5m (in night wards). The data for the prior art systems is taken from a hospital vibration study by the Concrete Centre (UK):

15

The system 10 of the present invention shows efficiency by having depth next to the post-tensioned system while having prefabrication with a framed structure that gives the greatest speed of construction.

Claims

1. A composite beam flooring system for a framed building, the system comprising at least a pair of prefabricated slabs; a pair of beams in parallel spaced relationship such as to define a inter-beam space therebetween, each beam supporting a respective slab at an edge of the slab; an array of reinforcing members located within and/or overlying the inter-beam space; and concrete filling the inter-beam space and encasing the array of reinforcing members and covering the prefabricated slabs.

2. A composite beam flooring system according to claim 1 in which the building comprises at least a pair of substantially vertical columns spaced from one another, the system comprising a support pad on each of a pair of opposed outer faces of each column, each beam extending between at least a pair of the columns and being seated on at least one support pad at each column.

3. A composite beam flooring system according to claim 1 or 2 in which the reinforcing members comprise an array of reinforcing members within the inter-beam space and an array of reinforcing members overlying the inter-beam space and extending outwardly to overlie the edge of each slab.

4. A composite beam flooring system according to claim 2 or claim 3 when dependent on claim 2 in which at least some of the reinforcing members within the inter-beam space pass through the columns which extend vertically through the inter- beam space.

5. A composite beam flooring system according to any preceding claim in which each beam supports the respective slab on a side of the beam opposite to that on which the inter-beam space is defined.

6. A composite beam flooring system according to any preceding claim in which the beams comprise I-beams.

7. A composite beam flooring system according to claim 6 in which each I-beam comprises an upper flange, a web, and a lower flange, the lower flange having a greater width than the upper flange.

8. A composite beam flooring system according to claim 7 in which the lower flange has a stepped reduction in thickness between the web and an edge of the flange.

9. A composite beam flooring system according to any preceding claim comprising permanent shuttering positioned between the pair of beams such as to define a base of the inter-beam space.

10. A composite beam flooring system according to claim 9 in which the shuttering becomes an integral part of the beam.

1 1. A composite beam flooring system according to claim 9 or 10 in which the shuttering comprises one or more substantially flat plates having stiffening depressions formed therein.

12. A composite beam flooring system according to any of claims 9 to 1 1 in which the shuttering comprises a lip provided along each of a pair of opposed edges of the shuttering.

13. A composite beam flooring system according to any of claims 2 to 12, when dependent on claim 2, comprising an array of couplings formed integrally with each slab adjacent the edge thereof, and to which are secured some of the reinforcing members which overlie the channel.

14. A composite beam flooring system according to claim 13 in which the couplings are in the form of hooks cast into the slabs, the respective reinforcing members passing through the hooks.

15. A composite beam flooring system according to any preceding claim in which the slabs comprise pre-cast concrete.

16. A composite beam flooring system according to any preceding claim in which each slab comprises a shoulder formed along the edge of the slab, and into which shoulder the edge of the respective beam is received.

17. A method of constructing a composite beam flooring system in a framed building having vertical columns, the method comprising the steps of:

securing a pair of beams between at least a pair of columns with one beam on either of a pair of opposed sides of the columns such as to define a inter-beam space between the beams;

supporting an edge of a respective slab on each of the pair of beams;

positioning reinforcing members within the inter-beam space and above the inter- beam space to overlie the edge of each slab; and

pouring concrete to encase at least the overlying reinforcing members to provide continuity across the pair of slabs.

18. A method according to claim 17 comprising passing the pair of beams past a plurality of the columns in order to achieve continuity of the beams at said columns.

19. A method according to claim 17 or 18 comprising, in the step of positioning reinforcing members, positioning a first set of reinforcing members to lie in a direction substantially parallel with a longitudinal axis of the beams, and positioning a second set of reinforcing members to lie in a direction substantially transverse to the longitudinal axis of the beams.

20. A method according to claim 19 comprising the step of passing at least some of the first set of reinforcing members through the columns to achieve continuity of the reinforcing members at said columns.

21. A method according to any of claims 17 to 20 comprising the step of positioning shuttering between the pair of beams such as to define a base of the inter-beam space.

22. A method according to any of claims 17 to 21 comprising, in the step of pouring the concrete, filling the inter-beam space with poured concrete in order to encase the reinforcing members within the inter-beam space.

23. A method according to any of claims 17 to 22 comprising, in the step of securing the pair of beams, fixing a support pad on each of the pair of opposed faces of each column, and seating each beam on a support pad at each column.