GB2495319A

GB2495319A - Beam and slab floor construction

Info

Publication number: GB2495319A
Application number: GB201117282A
Authority: GB
Inventors: John Stehle
Original assignee: Laing Orourke PLC
Current assignee: Laing Orourke PLC
Priority date: 2011-10-06
Filing date: 2011-10-06
Publication date: 2013-04-10
Anticipated expiration: 2031-10-06
Also published as: GB2495319B; GB201117282D0

Abstract

A system for constructing a floor (2) in a large-scale composite structure provides a steel framework (8) which is made up of steel beams (10) which define a perimeter of the floor and at least one horizontal beam (12) within it. This framework is used to support a plurality of lightweight concrete precast planks ( 14) which are laid on the framework and connected to it by means of shear connectors. The shear connectors connect couplers which are precast into the edges of the planks in the factory with adjacent pockets by means of a bar ( 24) which is pre-installed into a pocket and then passes through a hole (22) in a steel plate (18) welded to the top of a horizontal beam and then screwed into the coupler in the adjacent plank. Once the pocket has been in filled by grouting or concreting the connections increase the effective strength and stiffness of the beams, diaphragm strength, fire separation and resistance and acoustic separation.

Description

Floor Construction The present invention relates to the construction of floors within large multi-storey composite structures using steel beams that create a framework defining multiple floors.

In particular it is concerned with systems for connecting concrete panels or planks that can be used to make up a floor slab in such a structure in order to transfer the shear forces to a steel framework of the structure.

One such system and the technical background are described in US2O1 1/0113714 (New Jersey Institute of Technology) 19 May 20] 1. In this system shear transfer takes place with a deck material which supports a floor slab and uses a shear connector that passes through the floor slab.

In order to enable rapid construction, it is desirable to use pre-cast concrete elements and assemble them on site.

A coupler system for allowing adjacent precast concrete members to be connected is described, for example, inUS2009/1039177 (Barsplice Products, mc) 4 June 2009. In this system reinforcing rebars within the slabs are connected by means of a cast metal connector.

Solution of the Invention The present invention provides a floor comprising a steel framework defining a perimeter of the floor and at least one horizontal beam within the floor; and a plurality of concrete planks laid in an array on the framework; each of the concrete planks having at least one coupling socket precast into an edge of the plank and at least one pocket extending into a body of the plank from at least one other edge; the horizontal beam being provided with upstanding shear plates having openings therein spaced to align with couplers on the edge of an adjacent concrete planks: a plurality of threaded bars which each have one end received in a pocket, pass through an opening in a shear plate, and have the other end screwed into a coupling socket in order to connect edges of adjacent planks that abut over the horizontal beam; and grouting or concrete which secures the bars into the pockets.

The invention also includes a method of manufacturing and constructing such a floor.

diaphragm strength, fire separation and resistance and acoustic separation.

Brief Description of the Drawings

In order that the invcntion may be well understood an embodiment thereof will now be described, by way of example only, with reference to the accompanying diagrammatic drawings, in which: Figure 1 shows a perspective view of a pan of a framework of a composite structure made up of steel beams; Figure 2 shows a plan view of the same part as Figure 1 after installation of lightweight concrete plan ks; Figure 3 shows a perspective view of a steel beam used to make up the framework of Figure 1; Figure 4 shows a detail section through a joint over a steal beam of the type indicated as typeAin Figure 2; FigureS shows a detail section through an unsupported joint of the type indicated as type B in Figure 2; and Figure 6 shows a detail cross-section through a shear plate in a completed type A joint.

Description of a Preferred Embodiment

A floor 2 in a large-scale composite structure can be defined as shown in Figure 1 by means of a stee' framework 8, which is made up of steel beams 10 that define a perimeter of the floor and at least one horizont& beam 12 within it. This framework 8 is used to support a plurality of lightweight concrete (LWC) precast planks 14 which are laid on the framework 8 and connected to it by means of shear connectors.

The planks are laid in an array with edges of the planks resting on the beams of the framework. Shear connectors connect adjacent edges of the planks 14 by means of joints that can be seen in Figure 2.

As shown in Figure 3, the horizontal beams 12 are provided with upstanding steel shear p'ates 18 welded to their tops 20. Each plate 18 has a hole 22, which may take the form of a circular or horizontally elongated slot, which is oversized to cooperate with a threaded bar 24 that forms part of the shear connector.

The LWC planks 14 are prefabricated in a factory. As shown in Figure 2, they are formed in a range of sizes. Atypical large sized plank 26 traverses two horizontal beams and is pre-formed with three spaced coupler sockets 28 along one edge 30 and three elongate pockets 32 extending into a body of the plank from an opposite edge 34. As will be seen in Figure 2 the planks can have differing arrangements of sockets and pockets as dictated by other design and access issues for the floor. The planks are precast and may contain reinforcing bars (rebar). The sockets and pockets are formed in corresponding positions so that two similar adjacent planks can be connected together on site across a horizontal beam 12 in a type A joint as shown in Figure 4. The planks 26 also have coupler sockets 28 precast into their other edges 40 so that they can also be connected to adjacent planks where they join without a supporting beam underneath -this is a type B joint as shown in Figure 5. In the illustrated embodiment, the planks forming the edge rows 42 of the floor are shorter and have only two pocket or sockets along each of their long unsupported edges to allow them to be connected together. It will be appreciated that various configurations and shapes of planks may be provided to enable an appropriate array to be laid on the framework for any specific required floor configuration.

The shear connectors are completed on site by the installation of threaded bars 24 which are typically pre-loaded in position prior to placement of planks in their final construction location.

As can be seen in Figures 4 and 5,the pockets 32 are formed with one inner end 44 open to an upper surface of the plank. The other edge end 45 of the pocket is open to an edge of the plank. These open ends are joined by a hollow bore 46 created in a known manner by the insertion of a corrugated void former 48 placed in the mould when the plank is cast.

The whole of the pocket may be provided \vith a rough interface to its exposed surfaces.

The length of the pocket is such that it can receive the whole of a bar 24. The inner end 44 may have a tapered and curved or arcuate base surface to facilitate demoulding. The pockets can alternatively be provided as open recesses in a body of the plank open to only one surface of the plank or as a fabricated steel box.

The coupler sockets take the fom of a threaded connections sized to receive an end of a bar 24. The socket is provided in the end of a reinforcing bar 36 which is embedded into the concrete plank during casting. However, in the simplest embodiment the coupler socket is just a nut east into the edge of the plank, although greater stability is provided by having the socket on the end of a rebar extending into a body of the plank.

On site the planks are laid on the framework. As shown in Figure 4 coupler sockets 28 on the edges of the planks that rest on horizontal beams 12 are positioned in alignment with one of the steel shear plates 18. When the array of planks has been fitted on the framework, bars 24 are placed in the pockets. Where the connection passes over the top of a horizontal beam the bar is projected out through the hole 22 in the shear plate. The bar is then screwed into the coupler socket. The holes 22 are oversized to allow for some tolerance during the positioning of the planks to enable an end of the bar 24 to enter the coupler socket squarely. Where there is no horizontal beam, the ends of the bars are screwed directly into the adjacent coupler socket as shown in Figure 5. Once all the connectors have been installed to connect all the edges of the planks in the array together, the open pockets are grouted or concreted to hold the bars firmly iii position. The grouting SO secures the bars in position and is keyed to the rough surface of the pockets as well as filling the space between the edges of the planks where they pass over the beam 12.

The type B joint as shown in Figure 5 is similar to Figure 4 except that the edges 40 of the planks abut one another and the grouting 50 fills both ends of the pocket and the gap between the planks in order to surround the engaged bar 24 and coupler socket 28.

Plates 18 may also be provided along the tops of beams 10 defining a perimeter of the floor to allow studs or other shear connector types that may be pre-installed on the beam to project into pockets in the adjoining planks. These pockets are then subsequently concreted or grouted in situ.

The array of LWC planks serves the following functions: * Support of gravity loading on the floor spanning between steel beams.

* Provision of composite action with the steel beams, such that the effective strength and stiffness of the steel beams are greater than if considered in isolation.

* Provision of diaphragm strength enabling lateral loading to be transferred through the floor.

* Provision of fire and acoustic separation between floors.

* Provision of fire resistance.

The planks and steel beams are designed according to normal building code requirements.

However, the shear connection system between the planks and the steel beams is unique.

It will be appreciated that this system is not dependent on the presence or position of the rebars within the planks and allows many different floor layouts and plank sizes to be used as required by the size of the framework and the loading required.

The system is particularly advantageous when used with planks made using either lightweight or normal weight aggregates.

Claims

<claim-text>CLAIMS1. A floor comprising a steel framework defining a perimeter of the floor and at least one horizontal beam within the floor; and a plurality of concrete planks laid in an array on the frameworlc each of the concrete planks having at least one coupling socket precast into an edge of the plank and at least one pocket extending into a body of the plank from at least one other edge; the horizontal beam being provided with upstanding shear plates having openings therein spaced to align with couplers on the edge of an adjacent concrete planks; a plurality of threaded bars, which each have one end received in a pocket, pass through an opening in a shear plate, and have Ihe other end screwed into a coupling socket in order to connect edges of adjacent planks that abut over the horizonta.l beam; rnd grouting or concrete which secures the bars into the pockets.</claim-text> <claim-text>2. A floor as claimed in claim 1, wherein the pocket is defined by means of a corrugated void formcr cast into the plank between an edge and an inner end open only to one face of the plank.</claim-text> <claim-text>3. A floor as claimed in 1 or 2, wherein some of the connections between planks do not occur over a beam.</claim-text> <claim-text>4. A method of constructing a floor as claimed in any one of the preceding claims, comprising the steps of placing lightweight concrete planks on the steel framework and making a joint between adjacent planks where they are both supported by a horizontal beam by means of placing a bar into a pocket, through a shear plate and into a coupler socket on an adjacent plank; and then grouting or concreting in order to fill gaps in the pocket and between the planks.</claim-text> <claim-text>5. A method of constructing a floor substantially as herein described with reference to the accompanying drawings.Amendments to the claims have been filed as followsCLAIMS1. A floor comprising a steel framework defining a perimeter of the floor and at least one horizontal beam within the floor; and a plurality of concrete planks laid in an array on the frameworic each of the concrete planks having at least one coupling socket precast into an edge of the plank and at least one pocket extending into a body of the plank from at least one other edge; the horizontal beam being provided with upstanding shear plates having openings therein spaced to align with coupling sockets on the edges of adjacent concrete planks; a plurality of threaded bars, which each have one end received in a pocket, pass through an opening in a shear plate, and have Ihe other end screwed into a r coupling socket in order to connect edges of adjacent planks that abut over the horizonta.l beam; rnd grouting or concrete which secures the bars into the pockets.Ct)
2. A floor as claimed in claim 1, wherein the pocket is defined by means of a v" corrugated void former cast into thc plank between an edge and an inner end of the pocket open only to one face of the plank.
3. A floor as claimed in 1 or 2, further comprising connections between planks made with the coupling sockets, pockets and threaded bars which do not occur over a beam.
4. A method of constructing a floor as claimed in any one of the preceding claims, comprising the steps of placing lightweight concrete planks on the steel framework and making a joint between adjacent planks where they arc both supported by a horizontal beam by means of placing a bar into a pocket, through a shear plate and into a coupler socket on an adjacent plank; and then grouting or concreting in order to fill gaps in the pocket and between the planks.
5. A method of constructing a floor substantially as herein described with reference to the accompanying drawings.</claim-text>