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Title:
JOINTING METHOD, SYSTEM AND COMPONENTS FOR MAKING PRE-CAST TENSIONED CONCRETE PILES
Document Type and Number:
WIPO Patent Application WO/2001/092646
Kind Code:
A1
Abstract:
A locking joint for joining first (10) and second sections (18) of a concrete pile comprises a metal plate on the end of each pile section and a metal skirt (130) extending from the metal plate on the first pile section around said pile section, and having an opening defined therein. A monocoque housing (12) made from folded sheet steel is secured behind the metal plate of the first pile section. The housing defines a base having an opening (48) therein coincident with an opening in the metal plate, and defines a second opening for receiving a wedge and aligned with said opening in the skirt. An outwardly projecting pin (16) projects from the metal plate of the second pile section and is received in a pin receiving space in the housing (122). The pin (16) defines an external flange or spigot at one end thereof. A wedge means (14) having a front end and a rear end, an upper face and a lower face and defining two arms and a slot (84) extending from said end front between the arms locates in the housing. Part of the upper face of the wedge means (14) adjacent the slot (84) firmly abuts the external flange of the pin (16) which passes through the slot means (84).

Inventors:
Chad, Walter Edward ("Corella", Lot 31 Old Hume Highway, Alpin, via Mittagong NSW 2575, AU)
Application Number:
PCT/AU2000/001156
Publication Date:
December 06, 2001
Filing Date:
September 22, 2000
Export Citation:
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Assignee:
Chad, Walter Edward ("Corella", Lot 31 Old Hume Highway, Alpin, via Mittagong NSW 2575, AU)
International Classes:
E02D5/52; E04C3/22; (IPC1-7): E02D5/30; E02D5/52; E02D5/58; F16B7/04; E04C3/22
Domestic Patent References:
WO1997038173A11997-10-16
Foreign References:
GB2115467A1983-09-07
DE3505479A11986-08-28
Other References:
DATABASE WPI Derwent World Patents Index; Class Q42, AN 1980-D8091C/17, XP002905557
DATABASE WPI Derwent World Patents Index; Class Q42, AN 1992-329743/40, XP002905558
DATABASE WPI Derwent World Patents Index; Class Q42, AN 1986-310226/47, XP002905559
Attorney, Agent or Firm:
F B RICE & CO (605 Darling Street, Balmain, NSW 2041, AU)
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Claims:
CLAIMS:
1. A jointing system for precast concrete piles in which opposing faces of two concrete piles are formed with mating joints wherein the joint is completed by inserting the spigot in the spigot receiving aperture and tensioned using a wedge defining two arms, one face defining a spigot receiving aperture, the other face defining a projecting bar having a spigot defined adjacent one end thereof and an opposed flange insertable through a side of the pile into the spigot receiving aperture with the upper face of the wedge and the spigot in firm slotting engagement.
2. A jointing system as claimed in claim 1 wherein the wedge is received in a housing in the form of a shroud defined on one of the piles, the shroud being made from one piece of sheet steel.
3. A jointing system as claimed in claim 2 wherein the shroud is made from a single piece of folded sheet material and flares outwards from a relatively narrower upper part which defines an orifice for receiving a bar to a relatively wider base which defines the spigot receiving aperture.
4. A jointing system as claimed in claim 3 wherein the upper part of the shroud defines an aperture formed to closely fit the shape of a bar forming part of a, or being connectable to, a reinforcing cage of the pile thereby allowing a deep penetration perimeter weld between the shroud and the bar.
5. A jointing system as claimed in any of claims 2 to 4 wherein a washer is provided which locates inside the shroud, closes one end of the same and braces the shroud thereby reducing the bending movement at the base of the shroud.
6. A jointing system as claimed in claim 5 wherein the washer defines a hole which is, in use, concentric with the spigot receiving aperture in the base of the shroud.
7. A jointing system as claimed in any preceding claim wherein a retainer element is provided for locking the wedge into the shroud.
8. A jointing system as claimed in any preceding claim wherein inner faces of the arms of the wedge are configured to interlock with the retainer element.
9. A jointing system as claimed in any preceding claim wherein the retainer element is formed from a plastics material and defines a profiled edge which mates with a corresponding profile on the inner faces of the arm of the wedge, initially compressing and deforming to engage with the profile before reverting to their original profile/configuration to lock the wedge in place.
10. A jointing system as claimed in any preceding claim wherein the wedge is made from a steel having a higher carbon content than either the shroud or the washer.
11. A locking joint for joining first and second sections of a concrete pile comprising: a metal plate on the end of each pile section; a metal skirt extending from the metal plate on the first pile section around said pile section, said skirt having an opening defined therein; a housing secured behind the metal plate of the first pile section said housing defining a base having an opening therein coincident with an opening in the metal plate, and defining a second opening for receiving a wedge and aligned with said opening in said skirt; an outwardly projecting pin projecting from the metal plate of the second pile section and received in the pin receiving space in said housing said pin having an external flange defining a spigot at or adjacent one end thereof and a second flange spaced from and opposing the spigot; a wedge means having a front end and a rear end, an upper face and a lower face and defining two arms and a slot extending from said front end between the two arms, the wedge device locating in said housing between the spigot and second flange part of the upper face of the wedge means adjacent the slot firmly abutting the spigot of the pin which passes through the slot means ; and locking means for locking the wedge inside the housing.
12. A locking joint as claimed in claim 11 wherein the housing is made from a single piece of relatively thick sheet metal and has a base, sides and a roof portion said roof portion defining an aperture for receiving a bar therein, said bar being part of or connected to a reinforcing cage for said first pile section.
13. A locking joint as claimed in claim 12 or claim 11, including a washer defining a first plate portion located between the lower face of the wedge and the base of the shroud, the washer further defining a second plate portion oriented generally perpendicular to the first portion which is shaped and configured to close and brace one open end of the housing.
14. A locking joint as claimed in claim 12 or claim 13, wherein the pin is defined on one end of a second bar which is part of or connected to a reinforcing cage for the second pile section such that tension forces are transferred from the second bar via the spigot as a shear force to the wedge and thence to the housing and first starter bar.
15. A locking joint as claimed in any one of claims 11 to 14, wherein the locking means comprise the inner faces of the arms of the wedge defining serrations, a serrated or irregular shaped profile and a deformable plastics block having a profile configured to mate with and engage the inner faces of the arms of the wedge connected to the second plate portion of the washer.
16. A locking joint as claimed in any one of claims 11 to 15, wherein at least one of the sides of the housing is welded to and supported by the skirt portion.
17. A cap for a concrete pile, the cap defining one element of a mating joint for connecting two piles, the cap defining a base plate and a skirt portion, the base defining a first opening adapted to receive a bar defining a spigot, the skirt portion having a second opening defined therein for receiving a wedge; a housing secured behind the base plate, said housing defining a base having a first aperture therein aligned with the first opening in the base plate, and defining a second aperture for receiving a wedge aligned with said second opening in said skirt, the housing being connectable to a reinforcing bar of a pile and being adapted to receive a spigot on a pin via the first aperture in the base; and locking means for locking the wedge in the housing.
18. A housing for use in a locking joint for jointing first and second sections of a concrete pile said housing being formed from a sheet of metal folded to define a chamber having a base, side walls and a roof portion, the base defining an aperture for receiving a spigot, in use, one end wall of the housing being open for receiving a wedge, and wherein the roof aperture defines a tubular portion arranged to encompass a bar forming part of or attachable to a reinforcing cage for the pile.
19. A housing as claimed in claim 17 further including a washer defining a first plate portion located on an interior face of the base of the shroud, the wedge further defining a second plate portion oriented generally perpendicular to the first portion which closes and braces the other open end of the housing.
20. A housing as claimed in claim 18 or claim 19, wherein the housing is formed from a single folded sheet of steel defining two opposed sloping roof portions at whose ends upstanding flanges are defined which are welded together, and further defining a tubular aperture adapted to receive a bar therein.
21. A jointing method for jointing precast concrete piles in which opposing faces of two concrete piles have mating joints, one face of a first pile defining a spigot receiving aperture, the opposed face of the second pile defining a projecting bar having a spigot defined at or adjacent one end thereof, comprising the steps of: locking the spigot of the second pile in the spigot receiving aperture of the first pile; and inserting a wedge means having a generally planar upper face and two arms and a slot defined therebetween into the spigot receiving aperture with the bar located in the slot and the upper face of the wedge in firm abutting relationship with the spigot thereby forming a pretensioned joint.
22. A jointing method as claimed in claim 21 wherein the wedge is received in a housing in the form of a shroud defined on the first pile.
23. A jointing method as claimed in claim 22 wherein the shroud flares outwards from a relatively narrower upper part which defines an orifice for receiving a bar to a relatively wider base which defines the aperture for receiving the spigot projecting from the opposed pile.
24. A jointing method as claimed of claims 22 to 23, wherein a washer is provided which locates inside the shroud, closes one end of the same and braces the shroud thereby reducing the bending movement at the base of the shroud.
25. A jointing method as claimed in any preceding claim wherein inner faces of the arms of the wedge define a serrated or irregular shaped profile and including the step of locking the wedge into the shroud by engaging the profile around a plastics block fixed in the housing defining a mating profile.
Description:
jointing Method, System and Components for making Pre-Cast Tensioned Concrete Piles Background to the Invention The present invention relates to pre-cast concrete piles which are jointed together to form a continuous length of pile and to components therefor. In particular, the invention relates to a method of pre-tensioning a pile joint to a given force.

Description of the Prior Art Piles are used to secure and support structures to the earth. The earliest form of pilings were holes dug into the ground and filled with stones and a binding material. Later wooden posts were driven into the ground. The advent of modern materials allowed more sophisticated piles to be made from steel and concrete. Numerous methods of inserting piles developed. One was to dig or drill a hole and cast in reinforced concrete. Another piling method was to drive a wooden, steel or pre-cast concrete pile into the ground. Yet another was to drill a hole in the ground using a steel casing which was later filled with concrete and steel reinforcing.

More recently, the pre-cast concrete pile has gained wide acceptance due to the economic efficiency with which it can be manufactured and the speed with which it can be inserted into the ground.

Most of the pre-cast piles manufactured today are designed to be jointed with a simple compression joint which is load bearing only and has no capacity for pre-tensioning or resistance to bending. They are cheap to manufacture but are limited in their application. Although the joint can be designed to be pre-tensioned, until now this has proved to be to expensive to manufacture.

US 3,884,589 in the name of Stabilator AB, discloses a locking joint for concrete piles having joined sections. Facing end surfaces of the pile sections to be joined are made of metal and have outwardly projecting pins and/or openings arranged therein. The openings communicate with pin receiving spaces to receiving a pin from the next section. The pin receiving are made from a block of steel. Each pin has a transverse hole therethrough to receive a second pin which is inserted through the hole in the first pin, via a bore extending through the side of the pile section. Locking means locate in the

bore to lock the second pin in place. The blocks for the joint are machined from solid blocks of steel which are 63mm thick. Machining has to be accurate and requires a 3 axis CNC machine. Machining and cutting the blocks to shape is time consuming and expensive. A jig set up is required as the mis- alignment required to create pre-tensioning has to be precise. The joint works but is expensive at three to four times the cost of a standard compression joint.

The foregoing description is provided to inform the reader of prior art piles which have come to the applicant's knowledge. The discussion should not to be interpreted in any way or shape or form as an admission that the prior art piles discussed above, are part of the common general knowledge of the person skilled in the art in Australia, or elsewhere.

The invention seeks to provide a pre-cast piling joint which can be produced at similar price to the compression joint and which can provide all the engineering benefits of a pre-tensioned joint.

Summary of the Invention In one broad aspect, the invention provides a jointing system and method for pre-cast concrete piles in which opposing faces of two concrete piles are formed with mating joints and the joint is tensioned using a wedge and spigot.

The wedge may be received in a shroud defined on one of the piles. It is preferred that the shroud is formed from a single piece of steel.

Preferably, the shroud flares outwards from a relatively narrower upper part which defines an orifice for receiving a bar to a relatively wider base which defines an aperture for receiving the spigot projecting from the opposed pile.

The purpose of the shroud is to transfer any tension load applied across the joint, during driving, or in service, back from the spigot to the body of the pile. This is typically achieved by welding a shroud starter bar which is welded to the pile reinforcing cage into the shroud where it is then cast into the body of the pile.

The shroud is preferably formed to closely fit the shape of the sized starter bar thereby allowing a deep penetration perimeter weld between the shroud and starter bar.

The method of forming and drawing the steel shroud allows the design shape to be achieved and eradicates any potential degradation of the steel's

molecular structure. It also allows a smooth flow of force to occur from the starter bar on one side of the joint through to the spigot, to which the starter bar, on the opposite side of the joint, is attached.

Thus, in a related aspect of the present invention, a housing for use in a locking joint for jointing first and second sections of a concrete pile said housing being formed from a sheet of metal folded to define a chamber having a base, side walls and a roof portion, the base defining an aperture for receiving a spigot, in use, one end wall of the housing being open for receiving a wedge, and wherein the roof aperture defines a tubular portion arranged to encompass a bar forming part of or attachable to a reinforcing cage for the pile.

In a particularly preferred embodiment, a washer is provided which locates inside the shroud, closes one end of the same and braces the shroud thereby reducing the bending movement at the base of the shroud. The washer defines a hole which is, in use, concentric with the aperture in the base of the shroud.

The shape, size and location of the washer reinforces the shroud at a point where bending could take place. It also shifts the tension loading of the shroud as it is transferred to shear below the head of the spigot. In addition, it further reinforces the internal end of the shroud by forming a solid closure of the internal end profile. It also serves to seal off the inner shroud area from ingress of concrete during casting.

In a further preferred feature, a retainer element is provided for locking the wedge into the shroud. The wedge defines a slot for receiving the spigot between two arms. Typically, the retainer element is formed from a plastics material and defines an irregular shaped edge which mates with corresponding irregular shapes on the inner faces of the arms of the wedge, initially compressing and deforming to engage with the irregular shapes before reverting to their original profile/configuration to lock the wedge in place.

Typically, but not always, the wedge is made from a steel having a higher carbon content than either the shroud or the washer.

The spigot is accurately machined to provide a predetermined tension loading to a joint when a wedge is driven into position. The design and shape of the spigot provides a shear line along the surface of the wedge, which exceeds the tensile strength of the starter bar to which it is welded. The spigot is typically recessed in the area where the starter bar is welded, providing a full perimeter deep penetration weld.

Typically, the wedge provides a leading edge to facilitate ease of alignment. Its thickness also provides a predetermined tensioning load in conjunction with the spigot. Irregular shaped front internal edges of the wedge grip and retain the retainer element to prevent movement during the driving of the pile.

The starter bars may be cranked at an angle of 45 degrees to allow them to be inserted into the cage which provides reinforcing for the body of the pre- cast pile. The cranked end of the starter bar that is attached to the joint is formed and sized. The spigot starter bar may be sized round.

In a related aspect, there is provided a locking joint for joining first and second sections of a concrete pile comprising: a metal plate on the end of each pile section; a metal skirt extending from the metal plate on the first pile section around said pile section, said skirt having an opening defined therein; a housing secured behind the metal plate of the first pile section said housing defining a base having an opening therein coincident with an opening in the metal plate, and defining a second opening for receiving a wedge and aligned with said opening in said skirt; an outwardly projecting pin projecting from the metal plate of the second pile section and received in the pin receiving space in said housing said pin having an external flange defining a spigot at or adjacent one end thereof and a second flange spaced from and opposing the spigot; a wedge means having a front end and a rear end, an upper face and a lower face and defining two arms and a slot extending from said front end between the two arms, the wedge device locating in said housing between the spigot and second flange part of the upper face of the wedge means adjacent the slot firmly abutting the spigot which passes through the slot means; and locking means for locking the wedge inside the housing.

A related aspect provides a cap for a concrete pile, the cap defining one element of a mating joint for connecting two piles, the cap defining a base plate and a skirt portion, the base defining a first opening adapted to receive a bar defining a spigot, the skirt portion having a second opening defined therein for receiving a wedge; a housing secured behind the base plate, said housing defining a base having a first aperture therein aligned with the first opening in the base plate, and defining a second aperture for receiving a wedge aligned with said second

opening in said skirt, the housing being connectable to a reinforcing bar of a pile and being adapted to receive a spigot via the first aperture in the base; and locking means for locking the wedge in the housing.

In a further related aspect, the invention also provides a jointing method for jointing pre-cast concrete piles in which opposing faces of two concrete piles have mating joints, one face of a first pile defining a spigot receiving aperture, the opposed face of the second pile defining a projecting bar having a spigot defined at or adjacent one end thereof, comprising the steps of: locking the spigot of the second pile in the spigot receiving aperture of the first pile; and inserting a wedge means having a generally planar upper face and two arms and a slot defined therebetween into the spigot receiving aperture with the bar located in the slot and the upper face of the wedge in firm abutting relationship with the spigot thereby forming a pretensioned joint.

The components described above constitute a joint. An average of four, and up to eight, joints are welded and combined in a metal housing, constituting a base and a skirt in a welded assembly, called a"Half Pile Joint".

Within the"Half Pile Joint"they are assembled alternate as Shroud and Starter Bar and Spigot and Starter Bar sub-assemblies. The"Half Pile Joints"are symmetrical. Definitions of the various components are provided towards the end of the specific description.

Brief Description of the Drawings Specific embodiments of the invention will now be described, by way of example only, and with reference to the accompanying drawings in which : Figure 1 shows a spigot and starter bar assembly; Figure 2 shows an exploded and sectioned view of the spigot and starter bar assembly of Figure 1; Figure 3 shows an exploded view of a joint assembly embodying the present invention ; Figure 4 shows a sectioned view through a joint assembly; Figure 5 shows an exploded view of a"half joint" ; Figure 6 shows a"half joint"assembly; Figure 7 shows a sectioned view through a"pile joint"assembly of two "half joints"as shown in Figure 6;

Figure 8 shows an exploded view of the pile joint shown in Figure 7 with the two"half joints"separated; Figure 9 shows a horizontal section view of an assembly of a shroud, spigot, washer, wedge retainer and wedge; Figures 10a-10c are orthographic views of a flexible plastic wedge retainer; Figures 11a-11c are orthographic views of a locking & pre-tensioning wedge; Figure 12a-12c are orthographic views of a washer; Figure 13a-13c are orthographic views of a skirt; Figure 14a is a plan view of the shroud of Figure 10; Figure 14b is an end elevation view of the shroud of Figure 10; Figure 14c is a section on lines"A-A"of Figure 18a; and Figure 14d is a side elevation of the shroud of Figure 10.

Detailed Description of the Preferred Embodiment Referring to the drawings, Figure 3 shows an exploded view of a joint embodying aspects of the present invention. The joint comprises a number of components including a first or"shroud"starter bar 10, a housing in the form of a shroud 12, a wedge 14, a pin defining a spigot 16, a further starter bar 18, a combined washer/closure means 20 and a wedge retainer 22.

The components of the joint will now be described with reference to the relevant drawings.

Figures 1 and 2 illustrate the spigot 16. Figure 1 shows the spigot welded onto a starter bar 18 with Figure 2 showing the starter bar and spigot separated.

The spigot is rotationally symmetrical about its central axis and generally cylindrical. A chamfer 28 is defined at the top of the spigot. A recess 24 extends around the mid-portion or the spigot and a flange 29 is defined at its base. An upper face of the recess defines an annular flange 26 which, in use, engages with the wedge 14, as is explained in more detail below. A circular recess 30 is machined into the base 29 of the spigot 16. The recess is configured to receive a lead-in portion 32 of the further starter bar 18.

The starter bar lead-in 32 locates in the starter bar recess 30 and is secured thereto by a fillet weld 34.

The starter bar 18 comprises an upper portion 33 whose upper end defines the lead-in 32 and a lower portion 36 which are oriented generally parallel to one another, and a cranked offset portion 38 linking the upper 33 and lower 36 portions together. In the above described embodiment, starter bar lead-in 32 is designed to closely fit the starter bar recess 30 to create the optimum welding conditions. However, in an alternative embodiment, for joints with very high tensile loading, the outer bar lead-in 32 is threaded and the starter bar recess is tapped with a matching thread.

The"spigot"starter bar 18 and the shroud starter bar 10 have a cranked off-set, to enable them to be inserted into the steel reinforcing cage of the main cast concrete pile body. The degree of cranked offset varies with the diameter of the bar specified.

The position of the crank of the spigot starter bars is:- the length of the lead-in of the shroud starter bar plus the height of the shroud less the distance the shroud starter bar is inserted into the shroud.

The length of the starter bars from the cranked offset 38 into the pile body is to Engineer's specifications but preferably must not be less than 30 times the diameter of the starter bar.

The shroud 12 is best seen in Figures 3 and 10 and Figures 14a to 14b.

With reference to Figure 3, the function of the shroud is to transfer forces including tensile forces which may be applied to the starter bar 10 through the body of the shroud 12, the washer/closure 20, wedge 14, to the flange 26 of the spigot and thence onto the starter bar 18 welded to the spigot.

Turning to Figures 14a-14d the shroud is formed from a single piece of steel defining a base 40, and opposed side walls 42 and opposed sloping roof portions 44 at which turn upwards at the apex where they meet to define opposed adjacent upstanding flanges 46. The side faces or ends 45a, 45b are open. At the apex of the roof portion the two opposed flanges 46 are welded together. In the centre of the base 40 of the shroud there is a circular hole 48.

The hole is sufficiently wide to allow the spigot to pass therethrough as far as the bottom flange 29 of the spigot which is wider than the hole 48. The roof of the shroud, is formed to define an orifice 48 having an annular cross section which is shaped and configured so that the starter bar 10 is a close fit inside the orifice. The profile of the roof defining the orifice is deep drawn and has deep drawn radii 50,52 filleting the circular profile and all adjacent faces.

The welding of the shroud 12 to the starter bar 10 is best illustrated in Figure 4. The starter bar 10 locates in the circular orifice 48 and the shroud is fillet welded to the circumference of the starter bar externally by a fillet weld 54. The inner face of the orifice is also fillet welded to the starter bar at 56.

The next component to be described is the combined washer/closure means 20 which is illustrated in Figures 12a to 12c. One function of the washer/closure means 20 is to close one open end 45b of the shroud. The washer 20 also acts as a brace when fitted inside the shroud (as illustrated in Figure 4). The washer has a base portion 70 in the centre of which there is a circular hole 72 having a slightly narrower diameter than that of the hole 48 in the base of the shroud. A side wall 74 extends up from one side of the base.

The profile of the wall matches the inner profile of the ends 45a, 45b of the shroud so that when the washer is located inside the shroud with the lower face 70a of the base coincident with the base of the shroud, the side wall 74 closes one open end of the shroud. In the centre of the side wall 74, there is a small circular aperture 76 which receives a barb defined on the wedge retainer 22, which is described in more detail below following a description of the wedge 14.

The wedge 14 is shown in more detail in Figures lla to lie. The wedge is made of a steel material which may have a higher carbon content than both the shroud 12 and the washer/closure means 20. The wedge defines a lower face 80 which in use (see Figures 4 and 9) contacts the upper face 70b of the washer 20, and an upper face 82 which is parallel to lower face 80. The wedge is generally rectangular in plan except for an elongate cut-out portion 84 defined in one of the shorter sides of the wedge so that the wedge defines a generally U-shaped lead-in edge 86 having two parallel arms 88 disposed either side of the cut-out portion 84. The tips of the arms 88 are tapered to allow easy entry of the wedge element into assembled pile joints, to be described in more detail below. The arms define opposed inner faces 89 which are serrated or profiled or deformed at their distal ends for engagement with corresponding sections of the retainer element 22. In use, when the wedge is inserted into a joint thereafter, the upper face 82 of the wedge around the cut-out portion 84, engages against the spigot 26. Thus, the shear line between the washer and shroud and the shear line between the spigot and wedge are parallel (refer to Figure 9).

The wedge retainer 22 is best seen in Figures 12a to 12c. It defines a profiled wall 90 which corresponds to the shape of the upper part of the open walls 43a, b of the shroud for locating the retainer element inside the shroud.

A barb 92 projects from a rear face 90a of the wall 90 which in use abuts the wall 74 of the washer/closure 20. A block 94 projects from the base of the opposite face 90b of the wedge retainer. The block 94 has a serrated or profiled or irregular shaped external profile to match the internal profile 89 defined by the two arms 88 of the wedge. The wedge retainer element is made from a relatively flexible plastics material and, in use, the flexible plastic block 94 compresses as the wedge is driven into position and returns to its original profile as it mates with the corresponding profile 89 of the wedge.

Figure 5 shows two further components of a pile joint embodying the present invention, namely a base plate 120 which is generally square being profiled to mate with the corner radius of a skirt 130. A number of spigot entry holes 122 are punched into the base plate depending on the number of joints to be configured within the joint arrangement, which in the described embodiment is four.

The skirt 130 is shown in more detail in Figures 13a to 13c. The skirt includes a cut-out portion 132 which in use, allows the wedge to be inserted into the shroud, as will be described in more detail below. The skirt is made in two halves 133a, 133b which are welded together and which are identical until a number of breather holes 134 are punched in to one of the halves. The function of the breather holes is to permit air to escape from the jointed end of the pile as a concrete pile is cast.

The formation of a tensioned joint between two piles using the components described above will now be described with particular reference to Figures 5 to 8.

In the first stage, the two halves 133a, 133b of the skirt are welded together using a bead weld 140 on a jig to ensure precise alignment between the two components. The base plate 120 and skirt 130 are then stitched (fillet welded) on their internal adjacent faces with a full fillet weld being provided on the bottom edge. Two spigot and starter bar assemblies as shown in Figure 19 are then welded to the base plate with each starter bar passing through one of the entry holes 122 and with the spigot 16 projecting from the underside of the base plate. A shroud assembly 140, comprises the shroud washer closure 20, wedge retainer element 22 and a starter bar which is fillet welded to the

circular profile 48, but excludes the wedge which is used at a later stage in the proceedings to complete and pretension the joint between two concrete piles.

The welding of the components is carried out in an alignment jig to ensure that the spigot assemblies and shroud assemblies are correctly aligned on the base plate. The spigot and starter bar assemblies 19 are oriented with the starter bar offset at 45° to the wall of the skirt. This allows the four starter bars to be inserted into a cage which provides reinforcing for the pile. The assembly or "half pile joint 150 which is as shown in Figure 6, except that Figure 6 also shows a wedge is then coated with a polyurethane paint for preservation until the pile is cast and driven into the ground. The half pile joints are placed into the ends of a mould and steel reinforcing, in the form of a continuous cage is then added. The starter bars 19 overlap the bars of the reinforcing cage and are wired to the reinforcing cage and the piles are then cast. The lower most pile is then driven into the ground. The upper joint is then rotated and oriented until the spigots align with the entry holes into the shrouds as illustrated in Figure 8. The two ends 150a, 150b of the opposing piles are then mated together and the wedges driven into position to lock and pretension the final complete pile joint. The assembled steel and joints are then cast in concrete to form a complete pile segment.

When two pre-cast piles are positioned end-to-end, with one rotated at 90 degrees to the position in which it was cast, the spigots projecting from the end of each pile will enter the shrouds of the other via the holes 122 (see Figure 9). The piling joint is then locked into position and tensioned to a pre determined loading by driving the Wedge into position. The spigot is the control item governing the amount of tension which can be applied on insertion of the wedge. The control over the tension can be achieved by machining the face of the spigot which comes into contact with the upper face 82 of the wedge to give the required amount of minus clearance between the two components to effect the required degree of tensioning.

The pre-tensioning of the Joint takes place by applying a force between the upper face 82 of the Wedge, and the flange 26 on the Spigot.

The assembled pre-tensioned pile can now be driven into the ground with the retainer 22 preventing the wedge 14 from disengaging.

DEFINITIONS Pile joint Two"Half Pile Joint"assemblies mated and locked together with Wedges to make one Pile joint.

Half Pile Joint An assembly of Base Plate, Skirt, Shroud and Spigot assemblies to be cast into one end of a pre-cast concrete pile. joint A Joint constitutes two welded assemblies: i) Shroud/Starter Bar/Washer ii) Spigot/Starter Bar plus one Flexible Plastic Wedge Retainer and one Locking & Pre-tensioning Wedge.

These are the locking and pre-tensioning elements of a pile joint when welded to a Base Plate/Skirt assembly and cast into a concrete pile.

Spigot Turned metal part.

Shroud A blanked, formed and welded metal part.

Washer A blanked and formed metal part which is welded in position within the Shroud.

Spigot Starter Bar A cranked and sized deformed bar which is welded into the recess of the Spigot.

Shroud Starter Bar A cranked and sized deformed bar which is welded into a formed cylindrical hole in the Shroud.

(Flexible Plastic) Wedge Retainer A moulded plastic component which is fixed to the inner face of the Washer by a collapsible barb fixture and positioned such that a serrated or irregular shaped block protrusion will engage and retain the wedge when driven home.

Wedge A precision formed metal part which applies tension to the shroud and spigot assemblies and locks the two halves together.

Base Plate A stamped metal part in which holes are punched and govern the number, configuration and position of the joints to be incorporated in the Pile Joint.

Skirt A stamped and formed metal part which is welded to the Base Plate and contains the concrete at the jointed end.

SOME IMPORTANT BUT NOT NECESSARILY ESSENTIAL FEATURES AND ADVANTAGES OF THE PREFERRED EMBODIMENT 1. Monocoque shroud and method of joining to Starter Bar The one piece shroud 12 is designed to encompass the starter bar around its circumference and be coincident to the adjacent faces in order to create perimeter welds at the top of the shroud and at the end of the bar internally within the shroud.

The shroud is a force transfer medium between the starter bar, to which a tension force is applied, and the spigot. The tension force applied to the starter bar is transferred through the welds to the side walls of the shroud and dispersed to the bottom edges where it is converted from tension to shear.

2. Wedge force transfer & pre-tensioning The wedge 14 performs a function of force transfer of tension and bending from the outer edges of the wedge 14 and the inner bottom edges of the shroud 12 and converts these forces to shear where the upper face of the wedge 14 is in direct contact with the spigot 16.

The wedge transfers and resists the tension forces applied to the starter bar and shroud assembly and the spigot starter bar and through the shear line of contact between the upper face of the wedge and the contact face of the spigot.

The wedge locks the two halves of the joint together.

The wedge is shaped so as to give a tapered lead into the joint and to gradually apply a pre-tensioning force to the joint as it is driven into position.

The wedge has an inner irregular shaped profile on the leading inner faces of the slot to engage with a flexible retainer. This prevents it from vibrating out of position during the driving of the pile into the ground.

3. Washer closure, brace and shroud reinforcement.

The outer edges of the washer which are in contact with, or in close proximity to, the shroud side walls, reinforce the base of the shroud and prevent a bending moment taking place in the base of the shroud.

The washer adds to the shear strength of the shroud base under the head of the spigot.

The closure feature of the washer is designed to resist the ingress of concrete into the joint during casting.

The brace feature reinforces the shroud when it is placed under tension load and prevents it collapsing within itself.

4. Spigot shape, pre-tensioning control & method of attachment to Starter Bar The spigot is machined with a chamfer 28 on the leading end to facilitate easy alignment with the opposing joint into which it is to be inserted.

The spigot is so designed as to be the control item governing the amount of tension which can be applied to the joint on the insertion of the wedge. This is achieved by machining the face of the spigot which comes into contact with the upper face of the wedge to a dimension which gives the required amount of minus clearance between the two components.

The Spigot is machined with a recess into which the starter bar is inserted allowing a full perimeter weld between the two components.

5. Flexible wedge retainer.

The flexible wedge retainer is designed to engage and trap the wedge in its home position. The engagement profile of the flexible retainer closely matches that of the adjacent faces of the wedge.

The flexible wedge retainer is designed with a flange profile to align its adjacent face to the vertical face of the washer closure, and in so doing position the engagement portion of the retainer in the correct position to engage the wedge when it is driven home.

The flexible wedge retainer has a collapsible barb, which is incorporated into its face where it is adjacent to the washer closure. Once the barb passes through a corresponding hole in the washer closure face it then returns to its original profile, leaving the protruding heads of the barbs locked into position behind the outer face of the washer closure.

6. The assembled pre-tensioned joint The joint is so designed as to lock together the male and female halves of the joint with a wedge which are in turn cast into the concrete ends of a pre- cast pile. In so doing the opposing ends of the concrete pile are locked together.

The pre-tensioning of the joint prevents movement and or separation of pile segments during the driving of the pile and contributes to the resistance to bending of the pile when lateral forces are applied to the structure to which it is attached.

The specification of materials used in the construction of the joint are such that the tensile strength of the joint exceed that of the starter bars to which it is attached.

It will be appreciated by persons skilled in the art that numerous variations and/or modifications may be made to the invention as shown in the specific embodiments without departing from the spirit or scope of the invention as broadly described. The present embodiments are, therefore, to be considered in all respects as illustrative and not restrictive.




 
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