GB2340853A

GB2340853A - Beam for a composite floor comprising integral shear connectors

Info

Publication number: GB2340853A
Application number: GB9902644A
Authority: GB
Inventors: David Nicholas Varley; Nicholas Stephen Whitehouse
Original assignee: Terrapin International Ltd
Current assignee: Terrapin International Ltd
Priority date: 1998-08-24
Filing date: 1999-02-05
Publication date: 2000-03-01
Anticipated expiration: 2019-02-05
Also published as: GB9902644D0; GB2340853B

Abstract

Methods of manufacturing a composite floor comprise securing together cold rolled galvanised steel sections 1a so as to form a series of spaced apart parallel beams 1. Steel sheets 2 are positioned so that their edges rest on the beams. Concrete is poured onto the sheets to form a deck 4. The beams may define troughs T into which the concrete flows, or the sections may have tabs or holes, in order to key the deck to the beams.

Description

2340853 IMPROVEMENTS IN COMPOSITE FLOORS It is known to manufacture a

composite floor in-situ by casting a concrete deck onto profiled sheeting supported on a series of parallel steel beams. The hot rolled Ibeams which have been used in the past for this purpose are heavy and relatively difficult to manoeuvre. Moreover, in order to achieve a firm connection between the beams and the concrete deck it has been conventional to weld shear connectors in the form of studs onto the beams. Although it would be convenient to use lighter, galvanised steel beams produced by cold rolling, instead of hat rolled beams, shear connectors cannot be fixed in place in the conventional way. The alternative of using a large number of screws or nails to fix shear connectors on cold rolled galvanised steel beams would be a time consuming operation and might lead to operator error.

The composite floors and methods of manufacture described herein obviate the need for fixing shear connectors individually in place, whilst at the same time ensuring a firm and reliable connection between floor and beams.

In the drawings:

Figure 1 is a section through a first embodiment of composite floor in accordance with the invention, the section being taken transversely of a support beam assembled from a pair of cold rolled steel sections, Figure 2 is a section taken on the line 2-2 in Figure 1, Figure 3 is a view similar to Figure 1 but of a second 2 embodiment of composite floor, Figure 4 is a section taken on the line 4-4 in Figure 3, Figure 5 is a view similar to Figure 3 but of a third embodiment of composite floor, Figures 7 to 14 are views similar to Figures 1 and 3 but of modified floors.

Referring to Figures 1 and 2 of the drawings, a composite floor includes a series of parallel support beams 1, only one of which is shown. Each beam is assembled from a pair of identical, cold rolled, is galvanised steel sections la. Each section has upper and lower vertical webs 1b and lc which abut face to face with the corresponding webs of the other section when assembled to form a beam. The webs 1b and lc have rows of holes 7a, 7b, respectively, which register during assembly of the beams and receive bolts 8a, 8b, respectively, which secure the sections together.

Each section la is profiled so as to have a corrugation to provide rigidity and define a shoulder id along its upper side. When the beams 1 have been assembled and secured in position, corrugated steel sheets 2 are laid on the beams, with each end of each sheet resting upon a shoulder 1d of a respective beam. The sheets are connected to the beams by nails or screws but only to hold them in place during assembly. A firm interconnection between the sheets and beams is established in the finished floor as described below.

When the steel sheets have been fixed in place, with the gaps at the ends of the corrugations closed by abutment 3 with the webs 1b of the beams, reinforcing metal mesh 3 may be placed in position on the upper edges of the beams. Concrete is then poured onto the sheets to form a deck 4. 5 Although some of the holes 7a in the webs 1b receive bolts, the majority of these holes 8a remain open so that the concrete passes through the open holes 7a as well as around the heads and nuts of the bolts to key the concrete deck to the beams. This arrangement also ensures that the webs 1b are securely coupled together regardless of the soundness of the bolted connections. The mesh becomes embedded in the concrete during the formation of the deck. By using the upper row of holes 7a and bolts 8a to key the concrete deck to the beam, there is no risk of operator error producing an insecure joint, as could be the case if shear connectors were fixed individually in place. The webs 1b close the gaps at the ends of the corrugations in the sheets to prevent the concrete escaping.

Figures 10 and 14 are sections similar to Figure 1 through modified floors constructed using a similar principle but with beams 1 assembled from sections having alternative profiles.

In the case of the embodiment shown in Figure 10, the sections la are planar and abut throughout their vertical extent. The sections are secured together by bolts 8a and 8b and are provided at their upper ends with L-sectioned angle pieces 9. The flanges of the angle pieces extend above the sheets and are held in place by the bolts 8a. The corrugated steel sheets rest on the horizontal flanges of the angle pieces. Some of the bolt holes near the upper edge of the beam are left 4 open, to allow concrete to flow through them. The embodiment shown in Figure 14 differs from that in Figure 1 essentially in that the sections la are parallel sided throughout and define a rectangular 5 cavity within the beam.

In the embodiment shown in Figures 3 and 4, the beam 1 is formed from two laterally spaced cold-rolled galvanised steel sections la of rectilinear channel section which are bolted together with a channel shaped connector piece between them. The channel shaped connector piece 5 is also in the form of a cold-rolled, galvanised steel section and defines a trough T. The connector piece 5 extends the full length of the beam 1, or at least over that part of it intended to support the sheets 2. The flanges of the connector piece have upper and lower rows of holes 7a and 7b, respectively. The webs of the sections la have upper and lower rows of holes 7c and 7d, respectively. The upper row of holes 7c in the webs of the channel sections la register with the lower row of holes 7b in the connector piece and receive bolts 8b to secure the connector piece to the channel sections. Further bolts 8c are passed through the lower holes 7d so as to secure the channel sections la to each other adjacent their lower edges. The channel sections and connector piece thereby form a support beam having an open-topped trough T in its upper side. Holes 7a open into the trough along both sides. Bolts 8a (which perform no securing function) may be optionally passed through some of the holes 7a to extend between the side flanges of the connector piece.

During formation of the concrete deck, concrete flows through the upper holes 7a in the uppermost row of holes in the connector piece (and around the heads, nuts and shanks of the bolts 8a, if provided), and around the shanks of the bolts 8b within the trough T. Concrete may also flow into the trough T through the mesh 3. The most effective arrangement of holes and bolts, i.e. the number of holes 7a per unit length, and the number of bolts 8a per unit length, as well as the dimensions of the holes and bolts, may be determined by experiment so as to key the concrete to the channel section and hence with the beams most effectively. Alternatively, the bolts 8a may be omitted altogether so that only bolts 8b are embedded in concrete.

As an alternative to perforating the sections la of the first embodiment and channel section 5 of the second embodiment so as to form holes 7a to receive concrete, tabs may be formed along the inner or outer lateral surfaces of the sections at the same level as the rows of holes 7a shown in the Figures. The tabs become embedded in the concrete decking and key the concrete decking to the beams. Tabs may be formed by cutting Ushaped slots in the metal and pressing the tab out of the plane of the beam or connector piece. Alternatively, the bean or connector piece may have holes into which studs are fixed to serve as tabs.

Figures 8, 9, 11 and 12 show alternative constructions employing this general principle. In Figure 8, the sections la are shaped so as to form a trough T into which bolt holes 7a open as indicated by dotted lines.

Concrete flows into the holes 7a. Bolts used to hold angle pieces 9 in place become embedded in the concrete. In Figure 9, the open-topped connector piece 5 which defines the trough T is received within an outer channel defined by two sections la. Concrete flows through the bolt holes 7a indicated by dotted lines. The embodiment 6 shown in Figure 11 is similar to that shown in Figure 9 but makes use of sections la of a different shape. In the case of Figure 12, the beam is formed by a single channel section la which defines a trough T. Bolt holes are arranged near the upper edges of the section to receive concrete. Angle pieces 9 support the sheets and are bolted to the section at a lower level. Bolts may extend through some of the holes 7a and become embedded in the concrete. may be provided in these embodiments instead of or in addition to the bolt holes.

Referring to Figure 5, the floor shown therein is constructed in a manner similar to that described with reference to Figures 3 and 4 but without the aid of reinforcing mesh. Instead reinforcing fibres are mixed into the concrete before it is poured. Suitable fibres may be of steel, plastics or other materials and may have a length of 25mm and a diameter of 0.4mm, by way of example. The bolts 7a are provided with tubular spacers.

Because the open-topped connector pieces 5 do not support mesh reinforcement, they need not project above the level of the sheeting 2, and may simply form open- topped troughs T in the upper surfaces of the beams 1. As the cement is poured onto the sheeting it flows into these troughs and around the shanks of bolts 8 which pass through holes 7 in the sections la and connector pieces 5. The bolts are thereby embedded in the concrete when it sets to key the concrete to the beams. With this arrangement there need be only a single row of fixing bolts, although the number of bolts is preferably increased compared with the embodiments previously described.

7 The vertical flanges of the connector pieces preferably terminate flush with the upper surface of the sheets 2 in order to facilitate flow of concrete into the troughs and close the gaps at the ends of the corrugated sheets.

The flanges of the connector pieces help to ensure that the edges of the sheets 2 are correctly positioned relative to the beams and do not overlie the troughs.

The embodiments shown in Figures 6,7 and 13 are similar to Figure 5 in that the edges of the trough do not project above the sheets 2 and the concrete flows into the trough through its open top to form a lower layer of concrete onto which reinforcing mesh is placed before further concrete is poured onto the lower layer.

In the case of Figures 6, 8, 9 and 11, the depth of concrete between the beams may be increased to provide improved fire resistance.

It is, of course, also possible to omit the reinforcing mesh from the constructions shown in the other Figures and use reinforcing fibres instead.

It also falls within the scope of the invention for the bolts extending through the troughs T to be surrounded by bushes which may be profiled to enhance keying of concrete and beam. Alternatively, the sections and channel shaped connector pieces and/or angle pieces may be secured together other than by bolting them together (for example by rivetting) so that bolts do not pass through the trough into which the concrete flows during installation. In this case tabs may project from the flanges of the connector pieces into the troughs and be embedded in the concrete.

8 The cold rolled galvanised sections used to construct the beams are thinner and lighter than the hot rolled beams used in the past, and may be readily formed with holes or tabs. In those embodiments (such as Figures 3 and 4) wherein supernumerary bolts pass through the beam so as to serve only as keys and perform no securing function, these bolts may be replaced by other elongate members which will achieve the same effect.

9

Claims

I. A composite floor including a plurality of parallel support beams each comprising at least one cold rolled section defining an open-topped trough in the upper side of the beam, sheeting supported by the beams, and a concrete deck overlying the sheeting, downwardly extending portions of the concrete deck extending into the troughs, thereby uniting the deck with the beams.
2. A composite floor as claimed in claim 1, wherein each beam includes a pair of cold rolled sections secured together with the interposition of a channel-shaped connector piece to define the trough.
3. A composite floor as claimed in claim 1, wherein each beam includes a pair of abutting cold rolled sections so shaped as to define the trough.
4. A composite floor as claimed in claim 2 or claim 3, wherein bolts which secure components of each beam together pass through the trough and are embedded in the concrete to key the deck to the beams.
5. A composite floor as claimed in any of claims 1 to 3, wherein bolts which perform no securing function pass through the troughs and are embedded in the concrete to key the deck to the beams.
6. A composite floor as claimed in any preceding claim, wherein a plurality of holes open into the trough, some of which holes receive bolts, and others of which holes are filled with concrete, thereby to key the deck to the beams.
7. A composite floor including a plurality of parallel support beams each comprising at least one cold-rolled section, sheeting supported by the beams, holes passing through portions of the beams above the level of the sheeting, and a concrete deck overlying the sheeting, portions of the concrete deck extending into the holes to key the deck to the beams.
8. A composite floor including a plurality of parallel support beams each comprising at least one cold-rolled section, sheeting supported by the beams, tabs projecting from the beams above the level of the sheeting, and a concrete deck overlying the sheeting, portions of the concrete deck extending through the holes to key the deck to the beams.
9. A method of manufacturing a composite floor comprising arranging a plurality of beams in parallel, spaced apart relationship, the beams having troughs in their upper sides, each beam being formed by at least one cold-rolled section, positioning sheeting with edges thereof resting on the beams; and pouring concrete onto the sheeting to form a deck, the concrete flowing into the troughs to key the deck to the beams.
10. A method of manufacturing a composite floor comprising arranging a plurality of beams in spaced apart, parallel relationship, each beam including at least one cold-rolled section, rows of holes extending from one side of a portion of each beam to the other, positioning sheeting with edges thereof resting on the beams; and pouring concrete onto the sheeting to form a deck, the concrete passing through the holes to key the deck to the beams.
11 A method of manufacturing a composite floor comprising securing together cold rolled steel sections having vertical webs surmounted by horizontal flanges with the interposition of connector pieces so as to form a series of spaced-apart parallel beams, the connector pieces and sections having therein rows of holes which open into spaces within the connector pieces, positioning sheeting with edges thereof resting on the flanges of the beams at a level below the holes; and pouring concrete onto the sheeting to form a deck, the concrete passing through the holes to key the deck to the beams.
12. A method as claimed in either of claims 10 and 11 wherein bolts extending through at least some of said holes become embedded in the concrete.
13. A method of manufacturing a composite floor comprising positioning sheeting with edges thereof resting on the beams, tabs projecting from the beam above the level of the sheeting, and pouring concrete onto the sheeting to form a deck, the concrete enveloping the tabs to key the deck to the beams.
14. A method as claimed in any of claims 9 to 13, including supporting reinforcing mesh on the upward extremities of the beams, the mesh becoming embedded in the concrete.
15. A method as claimed in any of claims 9 to 13, wherein reinforcing fibres are mixed into and become embedded in the concrete.
16. Methods of manufacturing composite floors substantially as hereinbefore described with reference 12 to the drawings.
17. Composite floors substantially as hereinbefore described with reference to and as illustrated in Figures 1 and 2, Figures 3 and 4, Figure 5 or any of Figures 6 to 14 of the drawings.