Technical Field

[1] The present invention relates to building systems which use precast concrete

elements. More specifically, the present invention relates to systems in which the structure is supported using only concrete columns and walls rather than being steel framed or using separate horizontal beams to support the structure.

[2] The invention is particularly applicable to building systems for residential

applications for multiple occupancy such as hostels, blocks of flats or hotels, which due to the number of identical or similar residential units, lend themselves to modular construction. Such constructions are also divided into relatively small units making them an appropriate size to be created from a series of precast panels.

Technical problems

[3] The challenge with precast concrete buildings that do not have a frame with

horizontal beams, is that the joints between precast elements need to transmit vertical loads, lateral diaphragm forces to a stability structure, typically cores and/or shear walls, and provide a degree of vertical and horizontal tying capacity for robustness as required by most building codes. A conventional solution would be to cast an in situ structural topping .

[4] A further challenge is that construction tolerances of any in situ topping prevents direct placement of finishes and, if floor joints are exposed, then the joints open and close as the floors are loaded, which damages finishes. A conventional solution would be to provide an additional in situ architectural screed upon the structural topping.

[5] A further challenge is that floors generally need to sit on beams, which in turn sit on columns and walls. The conventional solution to avoiding beams is using a thick two- way spanning flat slab. The building services distribution occurs below the floor slab. The thickness of the slab impacts the building height.

[6] There is therefore a technical problem to create a precast construction system that allows a variety of layouts to be created without independent supporting beams together with a connection system requiring the minimum of site assembly whilst achieving the structural performance requirements as described above. Solving this problem reduces the installation time and overall cost of the construction.

[7] There is also a technical problem of minimising the thickness of the floor in order to minimise the overall building height and costs of the construction, particularly that of cladding, as well as vertical structures needed to support the floors, while maximising the number of units for a given height.

[8] Many precast components for various purposes have been disclosed in the prior art.

For example DE19842742 23 March 2000 (DENNERT) discloses a prefabricated modular base plate for a building which has separate depending feet at each comer. While it is taught that the slabs can be connected, said connections are non-positive, do not transmit vertical and/or horizontal loads, and, the feet are not coupled. It is only intended that these panels be used for the foundation layer.

Solution of the Present Invention

[9] The invention is defined in the appended claims.

[10] The solution of the invention is a building constmction system that uses large format precast floor panels, that do not require independent, separate supporting beams, site placed in situ stmctural toppings, that are connected together to create a complete floor. The panels have downstands around the perimeter. The downstands come together and are jointed. The panels can be supported only by vertical concrete column and wall elements that define the stmcture without the need for independent beams.

[11] The floor panels are typically sized to overlie a single residential unit such as a hotel or student accommodation room, or a bedroom or living room area, such that the downstands around the perimeter match the periphery of the residential unit.

[12] Embodiments of the invention use precast concrete panels that are sized to be lifted on a single crane hook. The panels are provided with perimeter longitudinal and transverse downstands. The longitudinal downstands are preferably along the edges of the panel and abut one another when the panels are assembled in an array in order to allow the panels to be interconnected and to be connected to supporting columns or walls, without the need for direct support of each panel.

[13] The downstands provide support to the slab which allows it to be considerably thinner than normal flat slab construction. The floor services below the slab, can penetrate the downstands allowing the combined thickness of the floor slab and services to be reduced. This results in a lower floor to floor height.

[14] The connection system between the panels uses a combination of cast- in steel

brackets and grouted connectors in preformed voids or sockets, and grouted shear keys formed into the side of adjacent downstands, designed to create a continuous floor across adjacent panels. Connectors can be designed for holding adjacent panels together both on the upper surface to prevent hogging and as tension connectors at the lower surface to prevent sagging, where the panels are not supported by a column.

[15] The upper surface connectors also limit movements under loading, preventing grouted joints opening, and with the substantially flat surface allow for the direct placement of finishes with only a debonding membrane, removing the need for a cast in situ architectural screed.

[16] The grouted shear key in combination with the connectors enable the continuous floor panels to transmit lateral diaphragm forces to stability elements and provide sufficient robustness tie capacity, without the need of any cast in situ structural toppings.

Description of the Drawings

[17] 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:

[18] Figure 1 shows a perspective view of an array of four interconnected panels of the present invention showing the connection to supporting wall sections and columns;

[19] Figure 2 is a view from below of the array of Figure 1;

[20] Figure 3 shows the connections between the panels for the array of Figure 1 ;

[21] Figure 4 shows how the array of Figure 1 forms part of a floor of a building

construction; [22] Figure 5 shows how an array of panels can form part of a building construction;

[23] Figure 6 is a view from below of an array similar to Figure 5;

[24] Figure 7 is a perspective view of a single panel of the present invention;

[25] Figure 8 is a series of drawings showing the stages of construction of a floor of a structure using the system of the present invention;

[26] Figures 9 is a perspective view of connections joining adjacent panels;

[27] Figure 10 is a view from below of the adjacent panel connections of Figure 9;

[28] Figure 11 is a sectional view of the connections joining adjacent panel downstands of Figure 9 and Figure 10;

[29] Figure 12 shows a perspective view of a further type of connector in situ and isolated;

[30] Figure 13 shows an example of a panel connection to a column, which uses embedded reinforcing double-headed studs in a downstand;

[31] Figure 14 shows an example of a panel connection to a wall, which uses embedded reinforcing double-headed studs in a downstand supported by a wall section; and

[32] Figure 15 is a perspective view of a detail of a comer connection between four

adjoining panels, in a situation where there are no downstands within a central access corridor;

Description of an Embodiment

[33] The building constmction system being described is primarily for multiple occupancy residential buildings, where the building is divided into residential units that may contain a bathroom pod and which are of sufficiently modest size, for example 3m x 7.2m and preferably no more than 4.5m wide or lOm long. The building element which creates both floor and ceiling is a large format precast plank or panel 10. The panels have substantially flat upper surfaces 12 at least in the central portion of the panels and can have rounded or bevelled upper edges 14. A floor plan of the building can be assembled from an array of interconnected panels which may be all of the same size or selected from a restricted set of panel sizes. Each panel consists of a thin concrete slab 16, for example 150mm deep, having downstands 18 of a depth of, for example, 300mm making a beam depth of 450mm, along the intended periphery of the residential unit. The downstands 18 extend along each longitudinal edge in this embodiment and are joined by two transverse downstands 20 so that the downstands co-operate to create a continuous enclosure beneath the floor surface in the manner of an inverted“bathtub”.

[34] The term downstand in the context of this specification is intended to refer to

depending extension from the main plane of the panel which is of a depth to transmit required structural loads to adjacent panels and supports

[35] The depth of the downstand 18 dictates the overall depth of the panel and are typically located within architectural wall zones. The depth of the thin concrete slab 16, kept to a structural minimum is located within the usable plan area of an architectural space thereby minimising the overall building height. For a panel with dimensions of 3m x 7.2m as discussed above with 300mm downstands, the ratio of overall depth of the panel to floor-to-floor height is typically 1:9, and the ratio of slab depth of panel to floor- to-floor height is typically 1:18. These figures are given as examples only to illustrate that the depth of the downstand and slab is small relative to the height of supporting columns 90 or walls 30 (typically 2.5m) within the structure. The present invention does not encompass proposals for precast elements which provide large and cumbersome U shaped structures combining wall and floor elements.

[36] If there is a central corridor, then one of the transverse downstands 20 can be offset from the end of the panel as best shown in Figure 2 and Figure 15. This results in the downstand enclosure terminating short of the end of the slab 28. This allows the downstands 18 to surround the residential unit and provide for a corridor needed for access. The adjacent downstands of abutting floor panels together create an integrated beam which supports the panels. Openings 22 of appropriate sizes are provided in the slab 16. The openings in the slab should be designed so as not to interfere with the downstands. Openings 23 in the downstands are detailed to allow services to pass through. The openings in the downstand are designed as slots to allow services distribution to be integrated within the depths of the downstands. [37] Notches 24 are pre-formed at various positions along the side edges of the panel to facilitate the alignment with rebar 26 projecting from supporting wall sections 30 or columns 90.

[38] Proprietary channel connections 27 are cast into the building perimeter side edge of the panel to facilitate the installation of the building fagade.

[39] The panels 10 may include radiant heating and cooling pipes in the precast

component.

[40] A panel of size 3m x 7.2m as described above would weigh about 10 tonnes and be capable of being lifted into position on a single crane hook. For larger units a maximum weight of, for example, 20 tonnes would still allow single hook lifting.

Connections

[41] Connections join adjacent panels, creating a continuous floor capable of transmitting vertical loads to supporting columns 90 or walls 30, and a lateral diaphragm structure. The general principle of the connectors to be described herein is that they have connector plates, usually fitted within preformed recesses 43 in the panel. The plates are bolted into the panel and to another adjacent panel, so that adjacent downstands are connected together to create integral beams which, when grouted, enable the panels to transmit vertical loads, supporting the floor on walls or columns only.

Several types of connector will now be described.

[42] Where adjacent panels are not supported, the connectors enable the panels’

downstands to form an integral continuous beam between supports. Connector recesses 43 may also be formed in a lower surface of the downstands, at locations where sagging may be an issue. Figures 9 to 11 show an example of a connector for use in this situation. With this connector, plates 54, 56 are fitted both on the upper surface of the panels and the lower surface of two adjoining downstands. The location of this type of connector is shown in Figure 9. Voids 58 with internal grooves, extend from the upper surface of each panel to the lower surface of the downstand. Each plate, 54, 56 has two pairs of projecting bolts 57 which fit into the voids. The plates and bolts fitted from both sides are grouted into position. [43] Another design of connector is shown in Figure 12. A base 60 of this connector supports four projecting rods 62 each with a socket 64 as an upper end. The connector with rods fit into the voids 58 within adjacent panels. An upper part 66 of this connector is a plate with four projecting bolts 65 which fit into the sockets in the rods. The plates and rods are grouted into position.

[44] Additional jointing recesses 42 with grooved voids 44 are also formed along the sides of the panel 10, at hogging supports where the top of the panels are in tension, to receive connectors of the type described in GB1721561.7 Laing O’Rourke Plc filed 2321 December 2017. These connectors use plates 50 that fit across adjoining recesses 42. The plates are fixed into the panels by bolts 52 which pass through holes in the plates into the voids 44 beneath. The connectors can then be grouted in position. Similar connectors can also be used where there is no recess and it is not necessary to have a flat upper surface at that point. An example of such a connector location is shown in Figure 3.

[45] Recesses 32 are formed at the corners of the panels at an inner end so that rectangular connector plates 34 can be bolted into position where four panels join together where there is no downstand. The corner connector plate 34 is shown sectioned in Figure 15 in order to illustrate how headed bolts 36 fixed to the connector plate are received into grooved voids 40 preformed within the base of the recess 32. The connector plate together with its headed bolts is grouted in position over the junction of the four panels to make a permanent connection between the panels. The bolts 36 can be permanently welded to the plates 34 or be screwed in position so that the connection can be demountable.

[46] Although a limited number of connector types may be needed for different positions within the structure depending on the type of forces arising at the various junctions, all of the connectors can be devised using similar principles of plates and bolts so that in many cases the parts are common and interchangeable.

[47] Reinforcing double -headed studs 68 can be positioned both in horizontal and vertical orientations within the body of a downstand as shown in Figures 13 and 14. The studs are positioned during the factory casting process. These studs will cooperate with the rebar 26 to reinforce the structure at that point above the columns and wall sections. [48] Upon installation and grouting of connectors 54, 56, 57 or 60, 62, 66, and 50, 52, adjacent panels are structurally connected together and can span between supporting columns or walls without the need for independent beams as the downstands together with the connectors create integral beams that provide the necessary structural support that would, in the prior art be supplied by separate beams that would require a separate construction step.

[49] Upon installation and grouting of all connectors, a floor slab is formed that has

sufficient horizontal tying capacity for robustness.

[50] Between adjacent panel downstands 18,20, the vertical face of the downstand is

longitudinally recessed 19, forming a shear key void 59 between connected panels. This shear key void is grouted when panels are installed.

[51] Upon installation and grouting of connectors and grouting of shear keys 59, a

continuous floor slab diaphragm is formed, capable of transmitting lateral forces to the building stability structure.

Construction process

[52] Figures 4 to 6 and Figure 8 show how the system is used to create a floor or storey of a building. Panels 10 are laid out in accordance with the plan and connected to concrete columns 90 and wall sections 30 constructed as required. It will be noted that the downstands define the periphery of a residential space. For the larger spaces shown in the design of Figures 5 and 6, two or more panels combine to provide the floor/ceiling of that residential space. Then the next floor is constructed by lifting on the next layer of panels 10 in the same configuration as the floor below. The soffit or underside of a panel can form an exposed ceiling of the residential unit and also the floor of the unit above.

[53] As shown in Figure 8, which illustrates an example sequence of events in the

construction process, minimal propping is required. Shoring props 80 are only needed at the positions where adjacent panels join at positions where there is no permanent column or wall section needed by the structure. Column and wall elements can be structurally joined by rebars 26 which pass between the adjoining downstands. The notches 24 provide space for rebar and surrounding concrete. The rebar 26 can be grouted or concreted in position. [54] A variety of connectors as described above are used at different positons depending on the forces arising.

[55] Where sagging is possible connectors as described with reference to Figures 9 to 12 are used. Where these connectors are installed at positions where temporary props are provided the connector plate 56 or 60 with its bolts in position and projecting upwardly can be placed on the tops of the props so that as the panel is lowered into position it can be manoeuvred so that the projecting bolt enters the preformed void 58.

[56] Where columns or wall sections are constructed with projecting rebar, it may be

possible to lower panels into position so that the rebar is sandwiched between the adjoining downstands.

[57] For certain types of connection it may be necessary to notch or thicken the downstand in certain limited areas, for instance it may be possible to notch the panel so that they can be supported on the edges of a column. These features can be preformed into the panel when it is cast. The downstands 18 may terminate short of the free end as shown in Figure 2 and Figure 15 to allow room for passage of services such as air ducts in a central portion of a corridor region. Notching may also be required adjacent wall panels.

[58] The panels or panels are bolted together by connector plates and grouted joints to create a flat surface that is ready for use. The solution has no concrete structural topping or architectural screed and because services are integrated within the depths of the beam this generally results in a reduction of floor depth and building height.

[59] By using panels as described the construction time can be considerably reduced

relative to pre-existing techniques resulting in cost savings. The overall weight of the construction is also reduced leading to saving in foundations, piles and other construction elements.

[60] By using panels it is possible to include radiant heating and cooling within the slab, which is a low-energy cooling or heating system.

[61] Matching the downstands to the periphery of the residential unit will frequently allow the soffit of the panel to form a ceiling for the unit.