Patent Application
20210095466
The present invention relates to precast concrete floors suitable for use in concrete buildings, for schools, hotels, office, retail and other premises.
The invention is also applicable to precast concrete floors that connect to conventional steel framed buildings. It is an alternative to building floors that consist of concrete on metal deck spanning onto steel beams, and it can be integrated with this solution or used as a direct replacement.
The invention is particularly applicable to floors which are required to be demountable in order to change the configuration and/or to have deck openings.
The challenge with precast concrete buildings is the joints between precast elements. If the joints are exposed, then the joints open and close as the floors are loaded, which damages finishes. A conventional solution would be to either cast an in situ topping or an in situ joint.
A steel framed building will typically have an array of vertical columns arranged in a grid structure joined at each floor level by horizontal beams. Various types of floor system for creating a floor or deck supported by the beams have been proposed. Existing steel and metal deck solutions create composite floors with a layer of concrete over a profiled metal deck. These solutions are low-profile and relatively lightweight and set a standard that must be matched by alternative constructions
A joint between concrete elements has been described in EP2882905 Laing O'Rourke Plc published on 17 Jun. 2015. That joint is formed by overlapping headed bars extending from adjacent faces of the concrete elements with vertical transverse studs between the bars. Such a joint technology has been used successfully to create floors without proppings or toppings from concrete elements in the form of solid precast flat slabs. However, such a strategy requires significant site construction in order to create the joints between adjacent concrete elements. The joints, so made, are also permanent.
There is therefore a technical problem to create a flooring system from precast and prefabricated elements that does not require a topping or in situ joints, that can be assembled easily on site, and that will perform in a way similar to normal steel framed buildings and remain competitive in terms of weight and profile depth with prior art solutions.
The jointing problems that a solution needs to address include the transfer of diaphragm forces across a floor, as well as making sure that joints do not open up, or suffer excessive cracking when the floor is subject to vertical loads and in-plane loads.
There is also a technical problem to create a demountable flooring system from precast and prefabricated elements that can be assembled easily on site and remain competitive in terms of weight and profile depth with prior art solutions.
Embodiments of the present invention utilise primary precast floor components made from reinforced concrete or prestressed concrete elements. The secondary components are an inverted U-shaped planks with a depending rib running along each longitudinal edge. These secondary components abut (with a narrow grouted gap) other secondary components along the longitudinal edge to create a ribbed floor. The secondary planks are connected together at regular centres by intermediate connector plates that transfer tensile forces across the grouted joint so that the floor can act as a complete diaphragm.
The ends of the secondary components are supported on primary beam elements that typically span between columns. The secondary components have a corner connector plate that extends across the grouted joint at the primary beam, to reduce cracking over the primary beam and to provide continuity across that joint, so that the floor can act as a complete diaphragm.
The primary beams can be an inverted T-shaped profile which enables the secondary components to sit on a support nib. Alternatively, or in addition, primary support beams can also be rectangular beams below the planks, or steel beams. The secondary planks are continuous over such support beams.
The primary beams support the secondary planks and sit on columns. A connector plate at the column, connects the secondary planks to the primary beam and to the column above. The column connector plates transfer diaphragm action across the joints and are designed to reduce cracking in the floors and to create a performance similar to a concrete floor on metal deck on steel beams.
All the connector plates are designed to transfer tensile forces across joints. The plates can be recessed into the floor. Tolerance is achieved by inserting the connector plates into grouted or concreted joints.
The connector plates are designed to be unbolted and thus the system can be demounted, with concrete/stone splitters used to split the grout joint once the connector plates have been removed.
The planks are precast with sleeves for bolt holes and recesses so that the various elements of the flooring system can be interconnected with metal plates bolted into the concrete elements. These plates work in combination with grouted joints to create a complete diaphragm. Bolted joints are normally not possible because of the need to allow tolerances.
The floors are connected together by a series of connector plates and grouted joints that provide a complete diaphragm action and loadable surface.
The solution of the present invention avoids the use of large in situ joints, or welded connections and makes the connections from bolts that can easily be undone. Therefore, the system can be disassembled in order to remove or re-configure the floor allowing at least some components to be reused.
The elements are stable in their own right and the infill joints are simple.
Because the floors do not have any propping, nor do they rely on any topping, they can be loaded immediately after erection.
Because the floors are connected by plates that can be unbolted, the floors can be completely demountable.
The invention is defined in the appended claims.
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:
The modular flooring system described is intended to be installed in a multi-storey building such as a low rise office, retail premises, hotel or school. The building is defined by means of an array of vertical columns made up of individual floor height column sections 2 arranged in a grid structure, for example a 9 m×9 m or 7.5 m×7.5 m, or 9 m×12 m grid as shown in
Each concrete plank 10 is an elongate inverted U-shaped precast concrete element having ends 12 and ribs 14 depending on the longitudinal side edges. The plank has a substantially flat upper surface that defines the level of the floor. The upper surface has recesses as described later for the purpose of interconnecting the planks. The underside of the plank is the soffit. The concrete planks are precast with internal rebar reinforcement 20 as shown in
A typical inverted U channel plank has a width of 1500 to 3000 mm between its side edges and a rib depth of 250 to 550 mm at those edges and 120-150 mm in its middle region. The planks may span 6 to 12 m between primary beams such that three planks can create a grid bay as illustrated in
The ends 12 of the longitudinal beams may be square or have an undercut rebate 24 which is sized to cooperate with the adjacent beam and allows the plank to be self-supporting on the beams 6 during construction. The ends of the planks sit on neoprene pads 64 on the beams. The joints between the planks are filled with a grout or concrete mix. Connector plates 54 link the planks across the beams 6 and therefore create a moment connection across the beams in the final condition.
The longitudinal ribs 14 of the planks may be provided with apertures 44 for services to pass through if required.
Lifting points 26 are provided on the plank so that it can be hoisted into position as shown in
Recesses 30 for the connector plates surrounding bolt sleeves 32 are pre-cast in the upper surface of the plank along the longitudinal edges. The bolt sleeves extend from the upper surface into the ribs 14. Recesses 40 surrounding bolt sleeves 42 are also formed at each corner of the end of the plank. These recesses 30, 40 are deep enough, for example 20 mm, to accommodate the various connector plates 52, 54, 56, and 58 which are used to join the components of the flooring system together. The use of connector plates 52, 54, 56, 58 and bolts 50 rather than welded or in situ joints which require construction work during assembly, allows this flooring system to be demountable.
The beams 6 are preferably of an inverted T-shaped section as shown in
Connector plates 52, 54, 56, 58 are provided in various configurations as shown in
Once the plates and bolts have been assembled, they can be fixed in position by grouting 62 to give moment continuity. The countersunk bolt head 53, can simply be unscrewed to facilitate removal of the connector plates 52, 54, 56, 58. Once the connector plates are removed the panels have no tensile capacity between the precast units, and can be separated by a concrete splitter for later reuse.
The primary beams 6, are bolted to a column 4 through threaded bars 74 that sleeve through the beam, as shown in
The flooring system made up of the components as described can be assembled on site without significant construction steps. There is no need for any propping during construction as the planks are self-supporting on the beams.
| Number | Date | Country | Kind |
|---|---|---|---|
| 1721561.7 | Dec 2017 | GB | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP2018/086231 | 12/20/2018 | WO | 00 |
