EP1397562B1

EP1397562B1 - Ground anchorage apparatus

Info

Publication number: EP1397562B1
Application number: EP02730439A
Authority: EP
Inventors: Derek William Rea
Original assignee: Corus UK Ltd
Current assignee: Corus UK Ltd
Priority date: 2001-06-06
Filing date: 2002-06-06
Publication date: 2009-04-08
Anticipated expiration: 2022-06-06
Also published as: ATE428030T1; GB0113711D0; DE60231874D1; EP1397562A1; WO2002099204A1

Abstract

Ground anchorage apparatus for foundations of modular structures comprises an anchor head (1) for location below ground level including two or more blade (4) members. The blades (4) are movable from a folded position in which they are generally aligned with one another to a splayed position in which they are inclined outwardly away from their folded positions once the anchor head (1) is in position. In a preferred embodiment, the apparatus includes a modular foundation block (3) whose upper surface is adapted to support a column (17) of a modular structure, and an elongate connector (2) extending between the anchor head (1) and a reaction plate (1) of the foundation block (3).

Description

The invention relates to ground anchorage apparatus. More especially the invention relates to ground anchorage apparatus for use inter alia with foundation blocks of modular structures. More especially, but not exclusively, the invention relates to ground anchorage apparatus for foundations of modular structures including, but not limited to, multi-level structures including platforms, roadways, car parks and bridges. The invention also relates to methods of constructing foundations for modular buildings using such ground anchorage apparatus.
On-site assembly of permanent and temporary structures from a plurality of readily transportable components and modules is well known. Advantages include speed of assembly (or disassembly where temporary structures are concerned) and cost savings through off-site production of generally standardised modular components. Additional advantages include elimination or significant reductions in the use of wet trades, significant reductions in disruptions caused by on-site evacuations, the use of light-weight structures and the ability to instal foundation blocks without disrupting on-going services.
Hitherto, for many multi-storey modular structures these advantages have been marginalised by the need for conventional foundations to minimise any tendency for an assembled structure being subjected to uplift forces. Uplift forces are occasioned by turning moments attributable, for example, to wind resistance acting on the modular structure when assembled.
US-A-4189879 discloses an earth anchor having a plurality of anchor arms which are extendable after being placed in position. A flexible skirt is attached to the anchor arms whereby after insertion into a hole, the arms and the skirt member may be extended into undisturbed earth. US-A-1844273 discloses a ground anchor which includes a plurality of outwardly movable flukes and US-A-5026213 discloses a ground anchor connected to a ground mounted slab through an anchor line.
The present invention sets out to provide ground anchorage apparatus which removes the need for conventional foundations thereby significantly increasing the benefits and advantages of on-site assembled modular structures.
In one aspect the present invention provides ground anchorage apparatus comprising a modular foundation block whose upper surface is adapted to support a column of a modular structure, and an anchor head for location below ground level which includes two or more blade members movable from a folded position in which the blade members are generally aligned to a splayed position in which the blade members are inclined outwardly away from their folded positions once the anchor head is in position, the apparatus being characterised by an elongate tensionable connector which extends between the anchor head and a reaction plate embedded within the foundation block, the upper surface of the foundation block being recessed to provide access to the end of the tensionable connector remote from the anchor head to facilitate in situ tensioning of the connector, the arrangement being such that movement of the blade members from their folded to their splayed positions is activated by in situ tensioning of the connector.
The anchor head is preferably shaped to resist uplift caused inter alia by wind forces acting on the modular structure when assembled. Thus, when in use, the anchor head may be tapered such that its cross-sectional area increases from its base to its upper surface. The blade members are preferably secured together through a swivel joint to which the tensionable connector is also attached, movement of the blade members from their folded to their splayed positions being activated by in situ tensioning of the connector. Alternatively, the blade members may be connected through pivots to the elongate connector itself. Each blade may be arcuate in cross section to take the shape of an aerofoil.
The foundation block may be produced from a cementitious material (e.g. concrete), a plastics material, (e.g. a polymer), a metallic material (eg. steel), a composite of two or more such materials or indeed any other material able to provide a stable foundation for a modular structure and the required integrity for ground anchorage purposes. Typically, the modular foundation block is formed with at least one bore or opening through which the upper end of a tensionable connector can pass, the uppermost end of the bore or opening providing the required access for in situ tensioning of the elongate connector. In a preferred embodiment, three bores or openings are provided, each adapted to receive the upper end of one of three tensionable elongate connectors. In practice, the foundations for a given modular structure may include a mix of foundation blocks having one, two and three (or more) bores or openings.
Typically, the surface area of the foundation block is one metre by 600 mm with a depth of 300 mm. Other sizes and shapes of foundation blocks may however be employed.
Where an anchor head is positioned below and to one side of a foundation block, the centre line of the respective bore or opening formed in the foundation block is preferably inclined to coincide generally with the angle at which the tensionable connector approaches and passes into the foundation block. Where two or more anchor heads connected to a single foundation block are provided, a like number of bores or openings each inclined to coincide generally with the angle of approach of the respective tensionable connector are provided.
Each bore or opening of a foundation block may include along its length an opening through which the uppermost end of a tensionable connector can protrude.
Alternatively, the foundation block may comprise an open-sided frame of, for example, metal (preferably steel). An open section tubular member may be secured to and depend from the internal periphery of the frame. In use, the or each elongate connector extends downwardly through the tubular member for anchorage at a location below the lowermost end of the tubular member.
The reaction plate preferably extends over substantially the entire width of the foundation block and is preferably produced from a metallic material. Suitable metallic materials include cast iron and steel. The latter may be galvanised. Other suitable materials could, however, be employed.
The reaction plate is formed with one or more apertures to coincide with the position or positions of the or each bore or opening formed in the foundation block.
Threaded connectors may extend upwardly from the uppermost surface of the reaction plate to positions, at, below or above the upper surface of the foundation block. These provide a secure connection to a base plate of a column of a modular structure. The threads of these connectors may be externally or internally formed.
The or each elongate tensionable connector may comprise a rod, bar, tube or cable connected to the anchor head. Connection to the anchor head may be via the aforementioned swivel joint and its uppermost end either threaded or crimped or otherwise connected to a threaded extension piece to enable the required tensioning to be effected. The tensioning may be achieved by means of a suitably dimensioned nut which co-operates with the complementary threaded portion of the elongate connector. In a preferred embodiment, the undersurface of the nut bears against the adjoining surface of the reaction plate.
Typically, the tension imposed on the elongate connector is between one and two times the predicted load to be imposed by the modular structure on the foundation block. Preferably the tension forces equate to between 1.15 and 1.50 times the predicted imposed loading.
In another aspect, the invention provides a method of providing a ground anchorage for a foundation of a modular structure, the method including the step of locating an anchor head below ground level which includes two or more blade members which are movable from a folded position adopted during location of the anchor head below ground level in which the blade members are generally aligned to a splayed position in which the blade members are inclined outwardly away from their folded positions once the anchor head is in position, the method being characterised in that it further includes the step of in situ tensioning of an elongate tensionable connector secured at one end to the anchor head located below ground level and at its other end to a foundation block having an embedded reaction plate through which the uppermost end of the elongate connector passes and against which the connector is tensioned in situ, said in situ tensioning of the connector activating said movement of the blade members from their folded to their splayed positions, access to the end of the elongate connector remote from the anchor head being facilitated by the upper surface of the foundation block being recessed, the upper surface of the foundation block providing a foundation for a column of a modular structure.
Tensioning of the elongate connector may be achieved by tightening a nut threaded on to the upper end of the connecting member against the upper surface of the reaction plate.
In an alternative embodiment, the elongate connector comprises an elongate tube, rod or the like to one end of which is secured a drill-head comprising a plurality of cutting teeth. In this embodiment, the blade members are secured through pivots carried on the outer surface of the connector close to its drill-head carrying end. Means for rotating the elongate member is provided at the end of the connector remote from the drill head. The rotation imparting means may comprise castellated teeth formed in the rim of the connector remote from the drill head. The connector may comprise a plurality of connector lengths each carrying castellated teeth which interengage with complementary teeth of a preceding or succeeding connector length to enable rotation to be imparted to the drill head nothwithstanding the number of connector sections employed.
The invention will now be described by way of example only with reference to the accompanying diagrammatic drawings in which:

Figure 1 is a side view in section of anchorage apparatus in accordance with the invention for supporting a column of a modular structure;
Figure 2 is a plan view from above of the apparatus illustrated in Figure 1;
Figure 3 is a side view of an alternative elongate connector of apparatus in accordance with the invention;
Figure 4 is a side view of the connector of Figure 3 in its splayed form; and
Figure 5 is a side view in elevation of an alternative foundation block which is not in accordance with the invention.

The anchorage apparatus illustrated in Figures 1 and 2 of the drawings comprises three anchor heads I connected through elongate connectors 2 to a foundation block 3. Each connector 2 may comprise a rod, bar, tube, cable or chain of metal or other suitable material. Typically, each connector 2 comprises a galvanised steel cable, rod or tube. Each anchor head 3 is positioned below ground level. Typically, the heads 3 are located by driving or excavation. An embodiment in which the connector is drilled into the ground is described below with reference to Figures 3 to 5.
Each anchor head comprises a plurality of blades 4 connected together for pivotable movement through a swivel joint 5. Each connector 2 is connected at its lowermost end to the swivel joint 5. Initially, the blades 4 are generally aligned with the respective connector 2 to assist driving of the anchor heads 1 into the ground. The blades are moved from their initial folded position to the splayed position shown in Figure 1 by in situ tensioning of each connector. Preferably, the selected anchor head is tapered such that its cross sectional area increases from its base to its upper surface.
The foundation block 3 has three bores 7. The bores 7 communicate with recesses 10. The block 3 may be cast from a cementitious material such as concrete, a metallic material, a plastics material such as a polymer or a composite of two or more of these materials. Embedded within the block 3 is a reaction plate 9 of metal or like material. The reaction plate is formed with three apertures 8 aligned with the bores 7 through which the connectors 2 pass and extends over substantially the entire width of the block 3. The upper end of each connector is threaded to receive a nut 12.
The centre line of each of the bores 7 is inclined to coincide generally with the angle at which the respective connector 2 approaches and enters the foundation block. As mentioned, the uppermost ends of the connectors are threaded. The threads may be formed in the outer circumference of the connectors or may comprise threaded extension pieces crimped or otherwise secured to the upper end of each connector. The threads extend to positions above the apertures 8. The recesses 10 are dimensioned to provide access to enable the nuts 12 to be placed on and engage the threads of the connectors for tensioning purposes. For rigid connectors such as steel rods or tubes, wedge shaped inserts may be positioned below the nuts 12. In this case, the centre lines of the recesses may be contiguous with the centre lines of the bores. The wedges ensure that the forces imposed by tightening the nuts act and are applied evenly to the adjoining surfaces of the reaction plate. Typically, the tensioning forces imposed on the connectors between one and two times the predicted loading imposed by a modular structure on the foundation block. A preferred tensioning force will be between 1.15 and 1.50 times the predicted load to be carried by the foundation block.
Tensioning of the connectors 2 is simply achieved by tightening the nuts 12 against the upper surface of the reaction plate 9. This may be achieved by using a suitable spanner. Once tensioned, it may well be necessary to check the imposed tension after a day or two and to make adjustments to ensure that the required tension is imposed.
Welded to the upper surface of the reaction plate and extending through the upper surface of the foundation block are internally threaded receptors 15. These are positioned immediately below apertures formed in a base plate 16 of a column 17 of a modular structure. The apertures receive threaded bolts 18 which engage the receptors 15.
The foundation blocks may be produced off-site by casting a cementitious material to a suitable mould, the reaction plate with upstanding receptors 15 being embedded within the block during casting. Modular foundation blocks are then transported to site thereby minimising on-site preparation times.
Typically, each foundation block measures 1 metre by 600 mm and has a depth of around 300 mm.
Turning now to Figures 3 and 4 of the drawings, the connector illustrated comprises a tube 20 typically produced from metal (eg. steel). Typically the external diameter of the tube 20 is between 2 cm and 25 cm, typically of the order of 5 cm. Aerofoil shaped blades 21 are connected to the tube 20 through pivots 22 which enable the blades to move from their folded positions close to the periphery of the tube 20 to the splayed positions shown in Figure 4. In Figure 3, the blades are shown in intermediate position. As shown, two blades are provided. More than two blades may be provided if required. As shown in Figure 3, the tube 20 comprises a plurality of elongate sections which are joined together by fixings 23 to vary the overall length of the tube. The end of the blade - carrying tube section remote from the blades 21 is formed with castellations 24 which engage complementary castellations formed in the adjoining end of a second tube section. Succeeding tube sections interconnect in the same way.
The end of the tube 20 carries a drill head 26 formed with a plurality of cutting teeth 27. Rotation can be imparted to the tube 20 by, for example, an electric or a petrol driven motor through the interengaging castellations 24 to enable the tube to be driven into the ground for anchorage purposes. Rotation of the tube 20 in the direction of arrow 28 causes the blades 21 to be positioned as shown in Figure 3; at the appropriate depth, the tube 20 is turned in the opposite direction to cause the blades 21 to move to their splayed positions shown in Figure 4. The relatively low weight imposed on the connector tube during drilling enables a relatively small motor to be adopted to impart rotation to the connector.
Figure 5 shows an alternative foundation block which is not in accordance with the invention. This comprises a steel open-sided frame 30 from which depends a galvanised steel tube 31. The sides of the frame 30 typically comprise lengths of steel which are joined together at their ends by any conventional means to define a frame of the required dimensions. The rim of the tube 31 may carry teeth for ease of driving of the tube into the ground. The tube is secured to the frame by, for example, a welding technique and provides additional resistance to uplift and alter loads imposed on the supported structure.
The elongate connector tube 20 extends through the tube 31 and the frame 30, and passes through a suitably shaped opening formed in a reaction plate 32 in the form of a plate of bar 33. The end of the tube 31 has an upstanding threaded member 34 for tensioning purposes. As for the foundation block illustrated in Figures 1 and 2, receptors are provided to receive a base plate of a column of a modular structure.
In an unillustrated embodiment, also not in accordance with the invention, the required ground anchorage simply comprises a tubular structure similar to steel tube 31 depending from a foundation block, typically of the type shown in Figure 5. In this embodiment, no elongate tensionable connector is provided. The lower rim of the tubular structure may carry teeth to enable drilling of the structure into the ground to the required depth. Typically the diameter of the tubular structure will be between 1 and 3 metres, typically 1-5 metres.
It will be appreciated that the foregoing is merely exemplary of anchorage systems in accordance with the invention and that various modifications can readily be made thereto without departing from the scope of the invention as set out in the appended claims.

Claims

Ground anchorage apparatus comprising a modular foundation block (3) whose upper surface is adapted to support a column of a modular structure, and an anchor head (1) for location below ground level which includes two or more blade members (4) movable from a folded position in which the blade members are generally aligned to a splayed position in which the blade members are inclined outwardly away from their folded positions once the anchor head is in position, the apparatus being characterised by an elongate tensionable connector (2) which extends between the anchor head (1) and a reaction plate (9) embedded within the foundation block (3), the upper surface of the foundation block (3) being recessed (10) to provide access to the end of the tensionable connector (2) remote from the anchor head (1) to facilitate in situ tensioning of the connector, the arrangement being such that movement of the blade members (4) from their folded to their splayed positions is activated by in situ tensioning of the connector (2).
Apparatus as claimed in claim 1 wherein the anchor head (1) is tapered whereby its cross-sectional area increases from its base to its upper surface.
Apparatus as claimed in claim 1 or claim 2 wherein the blade members (4) are secured together through a swivel joint (5) to which the tensionable connector (1) is also attached.
Apparatus as claimed in any one of claims 1 to 3 wherein the foundation block (3) is produced from a cementitious material, a plastics material, a metallic material, or a composite of such materials.
Apparatus as claimed in any one of claims 1 to 4 wherein the foundation block (3) is formed with at least one opening (7) through which the upper end of the tensionable elongate connector passes, the uppermost end of the opening providing the required access for in situ tensioning of the elongate connector.
Apparatus as claimed in claim 5 wherein the foundation block has three openings (7), each adapted to receive the upper end of one of three tensionable elongate connectors.
Apparatus as claimed in any one of claims 1 to 6 wherein the surface area of the foundation block is one metre by 600mm with a depth of 300mm.
Apparatus as claimed in any one of claims 5 to 7 wherein the centre line of the or each opening (7) formed in the foundation block is inclined to coincide generally with the angle at which the tensionable connector approaches and passes into the foundation block.
Apparatus as claimed in any one of claims 5 to 8 wherein the or each opening (7) includes along its length an aperture through which the uppermost end of a tensionable connector protrudes.
Apparatus as claimed in any one of claims 1 to 9 wherein the reaction plate (9) extends over substantially the entire width of the foundation block (3) and is produced from a metallic material.
Apparatus as claimed in any one of claims 5 to 10 wherein the reaction plate (9) is formed with one or more apertures to coincide with the position or positions of the or each opening formed in the foundation block (3).
Apparatus as claimed in any one of claims 1 to 11 wherein threaded elongate connectors extend upwardly from the uppermost surface of the reaction plate (9) to positions at below or above the upper surface of the foundation block (3).
Apparatus as claimed in any one of claims 1 to 12 wherein the or each elongate connector comprises a metallic rod, bar, tube, chain or cable.
Apparatus as claimed in claim 13 in which the or each elongate connector (2) is connected to the anchor head (15) through the swivel joint with its uppermost end connected to a threaded extension piece to enable the required tensioning to be effected.
Apparatus as claimed in any one of claims 1 to 14 wherein tensioning is achieved by means of a suitably dimensioned nut which co-operates with the complementary threaded portion of the elongate connector.
Apparatus as claimed in claim 15 wherein the undersurface of the nut bears against the adjoining surface of the reaction plate.
A method of providing a ground anchorage for a foundation of a modular structure, the method including the step of locating an anchor head (1) below ground level which includes two or more blade members (4) which are movable from a folded position adopted during location of the anchor head below ground level in which the blade members are generally aligned to a splayed position in which the blade members are inclined outwardly away from their folded positions once the anchor head is in position, the method being characterised in that it further includes the step of in situ tensioning of an elongate tensionable connector (2) secured at one end to the anchor head located below ground level and at its other end to a foundation block (3) having an embedded reaction plate (9) through which the uppermost end of the elongate connector passes and against which the connector is tensioned in situ, said in situ tensioning of the connector (2) activating said movement of the blade members (4) from their folded to their splayed positions, access to the end of the elongate connector (2) remote from the anchor head (1) being facilitated by the upper surface of the foundation block (3) being recessed, the upper surface of the foundation block providing a foundation for a column (17) of a modular structure.
A method as claimed in claim 17 wherein tensioning of the elongate connector is achieved by tightening a nut threaded on to the upper end of the connector against the upper surface of the reaction plate.