GB2422629A

GB2422629A - Adjustable Pile Cap

Info

Publication number: GB2422629A
Application number: GB0501584A
Authority: GB
Inventors: Duncan Clift Mcgregor
Original assignee: Screwfast Foundations Ltd
Current assignee: Screwfast Foundations Ltd
Priority date: 2005-01-26
Filing date: 2005-01-26
Publication date: 2006-08-02
Also published as: GB0501584D0

Abstract

An adjustable pile cap assembly to compensate for angular misalignment of a pile, a bottom plate 10 is positioned relative to a pile 34 in a generally horizontal plane and is fixed to the pile by a nut 38 and C-plate 14 connected to a threaded rod 30, connected to the pile 34, which passes through a central aperture or elongate slot in the bottom plate 10. A top plate 20 is then attached to the bottom plate 10 by a plurality of threaded rods 41 to 44 and fasteners 48 which are adjustable to permit adjustment of the height and angle of the top plate 20 relative to the bottom plate 10. The top plate 20 carries connection means such as a mast stub 24 for attachment of the structure to be supported by the pile and a tubular body 26 may be interposed between the plates to define an enclosure for reception of grout.

Description

1 2422629

ADJUSTABLE PILE CAP ASSEMBLY

This invention concerns a cap assembly particularly but not exclusively suitable for attachment to an individual pile whereby a structure, or a leg of a larger structure, may be secured to the pile with positional precision, while compensating for any misalignment of the pile itself.

Screw piles as are commonly used to support and anchor masts, towers, pylons and the like, typically each have a large steel disc, known as a pile head plate, welded to its upper end and a threaded rod (or stud) projecting centrally from this disc for purposes of attachment.

Usually, a respective pile is provided to support each leg of the mast or tower or the like so a typical mast with four legs will be mounted upon a set of four piles which are driven into the ground at appropriate positions at corners of a square corresponding to the lower ends of the legs. A foundation frame, substantially square in shape, and having a grout box at each corner is then mounted onto the upper ends of the piles. Bach grout box, which is simply a rectangular or box-like enclosure, rests upon a respective pile head plate, as is described in the applicant's earlier specification GB 2390128. The grout boxes may have bases with apertures there through to enable them to be secured to the threaded studs of the respective piles by application of nuts. Alternatively, other fixing means may be provided. If bases are provided on the grout boxes the apertures there through are larger than the respective stud diameters to allow for misalignment of the respective piles, it being virtually impossible to drive a pile into ground with such precision as is needed for exact alignment with the required position of the base of a leg of a mast. In any event, there is plenty of space within the enclosure of the grout box, around the pile attachment stud, and, once the foundation frame is levelled, each box is filled with grout which sets to secure the frame to the four supporting piles. The mast or tower or the like is then constructed upon and connected to the foundation frame.

An object of the invention is to allow a mast or tower or the like to be directly mounted to respective supporting piles without the need for an intervening foundation frame.

Another object is the provision of a pile cap assembly which is adjustable in more respects than hitherto so as to compensate more precisely than hitherto for angular misalignment of a pile.

Another object is the provision of an adjustable pile cap assembly for an individual pile (a mono pile).

According to the invention an adjustable pile cap assembly comprises a bottom plate and means of attachment of the bottom plate to a pile, in which respect the bottom plate is adapted to be adjusted relative to the pile in a generally horizontal plane prior to attachment and the attachment means are capable of securing the bottom plate to the pile in any adjusted position, and a top plate and means of attachment of the top plate to the bottom plate, in which respect these attachment means permit adjustment of the height and angle of the top plate relative to the bottom plate.

Preferably the bottom plate has a central aperture or an elongate slot therein which is of larger dimension than a threaded rod as conventionally is provided at the top of a pile so as to permit adjustment of the position of the bottom plate relative to the pile in a generally horizontal plane.

Preferably the means of attachment of the top plate to the bottom plate comprise a plurality of threaded members and respective fasteners which are threadedly adjustable thereon to support the top plate.

The invention will be described further, by way of example, with reference to the accompanying drawings, in which: Fig. 1 is a cross- sectional view showing a preferred practical embodiment of the pile cap assembly of the invention attached to the top of a pile; Fig. 2 is a plan view to a reduced scale of a bottom plate in the assembly of Fig. 1; Fig. 3 is a plan view to a reduced scale of a C plate in the assembly of Fig. 1; Fig. 4 is a plan view to a reduced scale of a top plate in the assembly of Fig. 1; Fig. 5 is a plan view to a reduced scale c the assembly of Fig. 1, parts underlying the top plate being indicated in broken lines; Fig. 6 is a plan diagram to a further reduced scale showing the positioning of four pile cap assemblies as in Fig. 1 as installed for the support of a four legged mast; Fig. 7 is a plan view showing the fitting of a template during installation of an arrangement as in Fig. 6 of four pile cap assemblies as in Fig. 1; and Fig. 8 is a shematic side view of a mast supported upon piles via respective pile cap assemblies as shown in Figs. 1 and 6.

With reference to Figs. 1 to 5 of the drawings, a preferred practical embodiment of the pile cap assembly of the invention comprises a bottom plate 10, a disc with a radial slot 12, which is known as a C-plate 14, and a top plate 20, these parts being illustrated separately in Figs. 2 to 5. Additional components of the assembly include a threaded rod 30 which is attached to an extends from the centre of a pile head plate 32, which is welded to an upper end of a pile 34, and four threaded rods 4 1-44 and their respective pairs of associated washers 46 and nuts 48, which serve to connect the top plate 20 to the bottom plate 10, as will be explained further.

As showing in Fig. 2, the bottom plate 10 is circular and has a large central aperture 11 there through, which may be between 19 and 20cm in diameter. Arranged at equal distant spacing from each other, radially outwardly of the central aperture 11, these are four smaller apertures 13, which are internally threaded for engagement of the respective rods 4 1-44.

As shown in Figs. 4 and 5, the top plate 20 is also circular, and is of substantially the same size as the bottom plate 10 and has a corresponding set of four threaded apertures 23 through which the threaded rod 4 1-44 also engage in use. The top plate 20 does not have a central aperture but it does have an aperture 21 offset from the centre, which is a grout filler hole. An upper surface of the top plate 20 carries a mast leg stub 24, which is an upstanding L- section element and may be welded into the plate surface. The L-section stub 24 is an accurate right angled guide and connection element positioned over a central region of the top plate 20.

A further component of the assembly is a tubular element 26.

All of the components are preferably of steel.

In use, and with reference to Fig. 1, the assembly is attached to the top of the pile 34, which is at or near ground level, after the pile 34 has been driven into the ground.

The threaded stud 30 already projects upwards from the pile head plate 32 and the bottom plate 10 is placed there over to rest upon the head plate 32. However, when four piles are being used to support respective legs of a mast, as indicated in Fig. 6, the position of the bottom plate 10 in a substantially horizontal plane may need to be adjusted to conform to predetermined spacing from the other pile heads so that the plate 10 is not concentric with the stud 30 and the pile head 32, The large central aperture 11 in the plate 10 allows for such sideways adjustment of the plate 10. The bottom plate 10 is then secured to the pile head plate 32 by placement of the C-plate 14 over the stud 30, the C-plate being of larger diameter than the aperture 11, and then by placement of a washer 36 over the stud 30 and finally threaded engagement of a nut 38. The provision of a radial slot 12 in the C-plate allows it to accommodate the threaded stud 30, no matter in which direction it is misaligned compared to the desired centre position of the bottom plate 10.

The four threaded rods 41-44 are then threadedly engaged into the apertures 13 of the bottom plate 10. The tubular element 26 is placed onto the bottom plate 10 to surround the upstanding rods 4 1-44. Then the lowermost of each of the pairs of nuts 48 are screwed onto each of the rods 4 1-44 to a position just slightly above the edge of the tubular element 26. The lower washers 46 and the top plate 20 are then put in place, At this point the height and inclination of the top plate 20 must be adjusted by manipulation of the respective lower nuts 48 to be exactly as required to support the respective mast leg at the required base height and upward inclination. This is most conveniently achieved by using a template 50 (Fig. 8), which is positioned between the respective mast stubs 24 of the arrangement of four piles and their respective cap assemblies shown in Fig. 6. Top plates 20 need to be adjusted in height so that the template 50 lies absolutely level and they also need to be adjusted in inclination so that the L-section mast stubs 24 fit snugly to the corners of the template at exactly the correct upward inclination. In this respect they all need to lean inwards towards the centre of the square, i.e. the centre of the eventual mast 60 (Fig. 7) which is to be mounted thereon. A typical inward inclination may be about 0.975 to the vertical and really precise positioning is essential at this stage. Only when the mast stubs 24 are absolutely level, correctly squared off to the template 50 and leaning exactly correctly should the upper nuts 48 be applied to the rods 41 to 44 and tightened.

Further adjustment of the bottom plate 10 may be necessary for correct squaring up and that can be done by lifting off the top plate 20 and loosening the nut 38, before resuming adjustment of the top plate 20.

After final checking of the above positions and tightening of the upper nuts 48, tape is applied externally to seal up any gaps between the tubular element 26 and the plates 10, 20. In particular, a gap of a few mm is likely to be present between the tube 26 and the top plate 20 owing to the necessary slight inclination of the latter by a few degrees from the horizontal. Grout is then poured into the hole 21 to fill the enclosure 52 defined between the plates 10, 20 and within the tube 26 in a similar way to a conventional grout box.

The template is removed for reuse. After the grout is fully set, the mast 60 can be mounted, or constructed, by attachment to the respective mast stubs 24.

The foregoing is illustrative and not limitative of the scope of the invention and variations in detail are possible in other embodiments.

Claims

1. An adjustable pile cap assembly comprising: a bottom plate and means of attachment of the bottom plate to a pile, in which respect the bottom plate is adapted to be adjusted relative to the pile in a generally horizontal plane prior to attachment and the attachment means are capable of securing the bottom plate to the pile in any adjusted position, and a top plate and means of attachment of the top plate to the bottom plate, in which respect these attachment means permit adjustment of the height and angle of the top plate relative to the bottom plate.

2. An assembly as claimed in claim 1 wherein the means of attachment of the bottom plate to the pile includes a threaded rod which is itself attached or attachable to a pile head plate at an upper end of the pile.

3. An assembly as claimed in claim 2 wherein the bottom plate has a central aperture or an elongate slot therein which is of larger dimension than the threaded rod so as to permit adjustment of the position of the bottom plate relative to the pile in a generally horizontal plane.

4. An assembly as claimed in claim 2 or 3 wherein the means of attachment of the bottom plate to the pile includes a disc having a radial slot therein.

5. An assembly as claimed in any preceding claim wherein the means of attachment of the top plate to the bottom plate comprise a plurality of threaded members and respective fasteners which are threadedly adjustable thereon to support the top plate.

6. An assembly as claimed in any preceding claim wherein the top plate carries connection means for attachment of a structure which is to be supported andlor anchored by the pile.

7. An assembly as claimed in any preceding claim wherein a substantially tubular body is interposed between the bottom plate and the top plate to define an enclosure for reception of grout.

8. An adjustable pile cap assembly for a mono pile substantially as hereinbefore described with reference to and as illustrated by Figs. 1 to 5 of the accompanying drawings.