WO2015087070A1

WO2015087070A1 - Pre-fabricated flooring cassette

Info

Publication number: WO2015087070A1
Application number: PCT/GB2014/053653
Authority: WO
Inventors: John Gradwell; David Scott; John Siegfried STEHLE; Sivasakthy SELVAKUMARAN; Philip Robinson
Original assignee: Laing Orourke PLC
Current assignee: Laing Orourke PLC
Priority date: 2013-12-11
Filing date: 2014-12-10
Publication date: 2015-06-18
Anticipated expiration: 2016-06-11
Also published as: GB201321922D0; AU2014363228A1; GB201611178D0; GB2535955A

Abstract

A steel framed floor is constructed from an array of cassettes. Each cassette has a spaced pair of longitudinal steel beams (2), a factory-installed concrete slab (4) connecting the steel beams (2), and modules (6) for services supported by at least one beam mounted beneath the slab. Primary cassettes also have at least two transverse beams (8) secured to the longitudinal beams (2), and a storey-height length of steel column (10) secured to each transverse beam.

Description

PRE-FABRICATED FLOORING CASSETTE

Technical Field

The present invention relates to modular constructions for use as prefabricated flooring cassettes and to mechanisms for connecting modules to supporting beams. The present invention describes a new way of constructing steel framed floors and complete building frames.

Background Art

Prefabricated buildings and building modules that are assembled in factories are well known.

These modules are transported to a construction site and craned into position. The module is then secured to the rest of the structure by means of bolts or other loose connections. The crane hook supporting the inserted module is not released until all the loose connections have been fixed. If there is any alignment issue this can cause considerable delays and the crane cannot be released to other duties.

Existing modules of complete rooms or floors lack versatility and need to be designed for the specific building.

When constructing steel framed buildings the beams used may be long and flexible when unsupported. This results in the need to prop them up during transport and installation. These props can be removed when the beams have been concreted in, but this requires an additional construction step.

Composite beams use steel and concrete, arranged so that the concrete participates in resisting bending stresses and enhances the steel beam’s bending stiffness. Traditional composite construction use steel from one supplier, combined with concrete from a second supplier and this marriage is made on the construction site, in the final, permanent configuration. This is subject to site constraints, weather, access, working at height etc. with associated risk and cost. For example a bridge over a river might have steel beams craned into position, followed by a team pouring concrete, with all sorts of logistical problems.

Where the module is intended to form part of an extended floor in a building, it is necessary to introduce some pre-camber to the concrete so that in use the floor stays level. This is difficult to do when concrete is poured on site.

An example of a prefabricated steel skeleton which can be taken to site is described in

WO

WO 98/35113

A ARCONA PROJECT AB 19980813

. The concrete slab is intended to be poured on site and the steel beams are designed to act as a shutter for the pouring of the wet concrete. This floor structure element offers provision in the steel beams for services to pass through during on-site installation. Therefore this approach only provides a partial solution to the technical problems of efficient construction.

A cassette comprising a spaced pair of longitudinal steel beams and a factory-installed concrete slab connecting the steel beams, is described in

WO

WO 2006/068435

A GCG HOLDINGS LTD 20060706

. When this product is used as a floor panel, it is taught to pour concrete over an array of beams so that portions of the metal joists are embedded in the concrete. Openings are provided for this purpose. Because of this a separate rim member to contain the concrete is needed. The beams are also provided with openings through which conduits for services can be passed. However traditional on-site installation of the services is envisaged.

Disclosure of Invention

The present invention seeks to solve these technical problems by providing two types of double T floor cassette as defined in the claims that have inherent structural stability during transport and installation.

These cassettes with building services integrated allow a steel framed floor to be assembled from an array of cassettes and occasionally additional primary steel beams. This makes for more efficient construction. The cassette system, as well as being a modular system, has the advantage of combining concrete slab and steel beam in the factory, reducing the risks and costs associated with forming composite action on site. This kind of product would be ideal for highway bridges as well as floors. By using interlocking engagements between the primary and secondary cassettes and/or providing landing lugs, the crane hook can be released quickly after secondary cassettes have been positioned.

Brief Description of Drawings

In order that the invention can be well understood some embodiments 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 from below of a primary cassette;

Figure 2 shows a perspective view from above of the primary cassette with its concrete planks partially installed;

Figure 3 shows a perspective view of a secondary cassette with a plank removed to reveal installed building services modules below;

Figure 4 shows an exploded view of a hanger connection detail;

Figure 5 shows the hanger connection in use with a support beam;

Figure 6 shows a three-way connection;

Figure 7 shows a detail of how the precast concrete slabs are notched over the connections;

Figures 8A and 8B are a sequence of drawings showing the step by step factory assembly of a flooring cassette and their subsequent transport; and

Figure 9 shows the cassettes partially assembled into a multi-storey building.

Mode(s) for Carrying Out the Invention

A steel framed floor is constructed from an array of cassettes. Each cassette is a prefabricated combination of structural steelwork, concrete slab and building services. A cassette has a spaced pair of longitudinal cellular steel beams 2, a factory-installed concrete slab 4 connecting the steel beams, and building services equipment 6 supported by at least one beam mounted beneath the slab. Primary cassettes also have at least two transverse beams 8 secured to the longitudinal beams 2, and a storey-height length of steel column 10 secured to each transverse beam 8.

The beams 2 may be a standard rolled product or a plate girder having top and bottom flanges joined by a vertical web.

The floor cassette combines three building systems that are traditionally installed separately. Namely, the steel frame, the intermediate floor slab (which may also act compositely with the steel) and the building services.

A ‘primary’ cassette as shown in Figures 1 and 2 comprises a pair of primary floor beams 2 and a storey-height length of steel column 10 (or columns). A storey-height length is defined by the design height of the storey between two adjacent floors. The columns 10 of each storey are interconnected as shown in Figure 9 so that the concrete slabs of each floor are separated by the required height for that storey. It will be appreciate that the columns 10 of each cassette are the same height but storey-height of different cassettes may vary according to the position of the cassette in the final construction.

The tops of the steel beams 2 are connected by a strip of factory-installed concrete slab 4. This slab is created from a series of pre-cast concrete planks 12. The planks 12 have notched edges 14 that fit round projecting studs 16 on an upper surface of the beams 2 so that the planks can be grouted together to create a continuous slab 4 integrally connected with the beams 2 after assembly. The notches therefore provide pockets for shear connections. As an alternative the concrete slab could be cast in-situ, though in the factory, rather than on site as taught by Arcona.

Each end of each beam 2 in the secondary cassettes is provided with a hanger connection 18 so that the cassette can be supported both on set up jigs 20 bolted to a factory floor during assembly as shown in Figure 8, and on a supporting beam 34 in a final construction. The hanger connections which are member parts of an interlocking engagement system are described in more detail below with reference to Figures 4 to 6. The hanger connection 18 allows the cassette to be captured as it is released from the lifting equipment, allowing time ‘on the hook’ to be minimised. A hanger connection is not shown on the primary beam in Figure 1 and 2 as it is not needed for floor plate as shown in Figure 9 which is one primary cassette wide. However, if a larger floor plate is required, then some of the primary cassettes would be provided with hanger connections 18.

Modular building services equipment 6 is installed at the manufacturing stage, beneath the slab 4 and between and around the steel structure, passing through web openings 22 in the beams when required. The equipment may be housed in modules or conduits, which are pipes and tubes which can be or support services for example electrical cables, water pipes, air conditioning units and the like.

The longitudinal primary beams 2 are connected by transverse outrigger beams 8 bolted to the primary cassette beams. The storey-height column segment 10 has bolted splices for connection to adjacent column segments.

A ‘secondary’ cassette is shown in Figure 3 and is based around a pair of secondary floor beams 2, without column elements. Otherwise it is similar in principal to the primary cassette. In this design the pre-cast concrete planks 12 may overlap the edges of the beams 2 and have openings 24 spaced from their edges to engage over shear connection lugs 16 on the tops of the beams 2. The edges of the planks 12 at each end of the secondary cassette are provided with notches 26 to expose the hanger connections 18. The connections 18 provide lifting/landing lugs to support the cassette when it is released from a crane hook. These lugs will rest on the tops of the primary beams of an adjacent primary cassette which serves as their supporting beam. Figure 7 shows a detail of the junction between a secondary cassette and the beam 2 of a primary cassette before the pockets have been grouted over to create a permanent bond. To maximise site productivity, the secondary cassette connections are detailed to enable quick release from the crane, without needing to engage a permanent connection. This will be accomplished with a steel hanger or ledge, enabling the secondary cassette to be landed on the first. If required, the strength of this connection can be supplemented using cover plates or cleats (without needing the crane hook for support).

Hanger Connections

Each hanger connection 18 is made up of an L-shaped plate 30 and an angle member 32 attached to the supporting beam. The angle member 32 creates a knife edge bearing for the shear force in the beam. The vertical leg of the angle can be arranged so that it bears over, or close to the web of the supporting beam 34 thereby minimising or eliminating any eccentricity. A vertical plate may also be used in place of the angle member, forming a ‘T’.

The profiled plate 30 is sized to act as a cantilever. The plate has a laterally extending arm 31 that can support the cassette on an adjacent longitudinal beam of another cassette on release from a crane that lifted it into position. The shaped plate 30 is tied into the top and bottom flanges as well as the web of the supported beam 2 of the cassette. This allows transfer of shear forces and bending moments. The supported beam 2 can be processed by standard coping machinery to create a notch 36 into which the shaped plate 30 can be fitted and welded to the flanges and web of the beam.

The shaped plate 30 incorporates a hole 38 for a lifting shackle. In this way there is no need for additional lifting brackets or lugs. All parts are welded together using fillet welds or butt welds.

Figure 5 shows the hanger connection connected to a supporting beam 34 provided with shear studs at the position of support onto which the cassette is landed by the lifting equipment. The shear studs form the other member of the interlocking engagement members. The shear studs 40 connect the angle member to the beam 34. The cassette could be shown positioned over holes in the beam and connected by bolts. The incoming beam is landed over the shear studs on the supporting beam. It is therefore captive and capable immediately of resisting vertical shear, horizontal shear and tie forces. The studs 40 provide interlocking members for receiving and interlocking with a mating member, namely the L shaped plate on the cantilever arm 31, on the ends of a longitudinal beam of another cassette.

Figure 6 shows the arrangement with two incoming beams on a single supporting beam 34, which may itself be a beam 2 of a primary cassette. The bearing angles (or plates) 32 become back-to-back. These can be through bolted if required to create a direct load path for tie forces.

Figure 7 shows the precast end notches 26, which create the void in which the hanger connection can sit. These notches 26 are grouted up on site at a later date during construction.

Factory assembly

The assembly of a cassette in a factory is illustrated in Figure 8. The set up jigs 20 are bolted to the factory floor and support the adjacent longitudinal beams of a cassette (only one of which is visible in the Figure) at a convenient height for working on. In the second step, the beams 2 are supported on the jigs 20 using the same hanger connections 18 that will be used in the final construction. As shown in the third step the services 6 are installed as required by the design. Then in the fourth step the pre-cast concrete planks 12 are landed on the steelwork covering the services that have been installed.

Precamber can be built into the cassette in two ways: firstly, by precambering the steel beam, before cassette assembly (in which case the precamber calculation should be based on the steel stiffness alone); or secondly, by laying the components out on pre-set levels and creating a precamber during assembly, using packing under the middle of the beam: before grouting or concreting. In this case the precamber calculation would use the composite stiffness.

The fifth step shows precamber being created by jacking up the steelwork in the centre to induce the required precamber with tight control. The shear connections between the planks are grouted to lock in the precamber.

In the sixth step the completed cassette is lifted off the jig using the lifting points 38 in the hanger connections 18. The completed cassettes can then be loaded onto a lorry for transport. As shown in the eighth step multiple cassettes can be transported to site together.

Lifting points, edge protection and any loose fittings/fixings can also be integrated at the design and manufacturing stages, so that the cassettes can arrive at site, ready for immediate installation.

Site assembly

On site the primary cassettes would be installed first and connected to column segments of the floor below, then secondary cassettes installed. In a preferred embodiment the secondary cassettes can be interlocked with engagement members (shear lugs 16) on the sides of the primary beams 2 to provide an interconnection that does not require connection with loose parts.

In the case of both primary and secondary cassettes the double T structure offered by the two beam connected by the slab, gives the cassette structurally integrity that avoids the need for propping. The combination of two steel beams and a composite precast concrete slab forming a ‘double T’ cross section is unique and will be immune to lateral-torsional buckling. No propping will be required on site. The steel downstand and a concrete top flange act as a single structural element.

After manufacture the cassettes are transported and erected as single components. An assembly of primary and secondary cassettes forms a cohesive structural system, including floor plates and service modules, as shown in Figure 9.

The service modules 6 that can be incorporated into the cassettes can have a wide variety of forms and some examples only are shown in the drawings. The services are interconnected across the cassettes using the cellular openings in the beams.

Claims

A cassette comprising a spaced pair of longitudinal steel beams (2), and a factory-installed concrete slab (4) connecting the steel beams, characterised in that building services equipment modules (6) are factory mounted beneath the slab and are supported by at least one beam, and in that the cassette is provided with interlocking engagement members (18 or 16, 40) that enable an array of cassettes to be assembled on site.
A cassette as claimed in claim 1, further comprising at least two transverse beams (8) secured to the longitudinal beams (2), and a storey-height length of steel column (10) secured to each transverse beam.
A cassette as claimed in claim 1, wherein the interlocking engagement member comprises a hanger connection (18) at each end for supporting the cassette both during factory assembly and on a support beam in a final installation.
A cassette as claimed in any one of the preceding claims wherein precamber is induced in the concrete slab during factory assembly.
A cassette as claimed in claim 4, wherein the concrete slab is assembled from pre-cast concrete elements (12) grouted together after the required precamber has been introduced.
A cassette as claimed in claim 3, wherein the beams are I-shaped with flanges joined by a web, and the hanger connections comprise an L-shaped plate (30) welded to the flanges and web at the ends of the beam and providing a laterally extending arm (31, 32) that can support the cassette on an adjacent longitudinal beam of another cassette on release from a crane that lifted it into position.