EP1741839B1

EP1741839B1 - Concrete pile connections

Info

Publication number: EP1741839B1
Application number: EP06253340A
Authority: EP
Inventors: Anthony Lewis c/o Stent Foundations Ltd Reddaway
Original assignee: Balfour Beatty PLC
Current assignee: Balfour Beatty PLC
Priority date: 2005-06-30
Filing date: 2006-06-27
Publication date: 2008-07-16
Anticipated expiration: 2026-06-27
Also published as: DK1741839T3; EP1741839A1; GB0513437D0; ATE401462T1; DE602006001800D1

Abstract

A concrete pile comprises first and second concrete pile sections joined together by respective end connectors, each end connector comprising an end plate covering an end of the pile section, two recess blocks fixed to an inner part of the end plate, two projecting pins fixed to an outer part of the end plate and a side pin for insertion through the two recess blocks, thereby to retain projecting pins of the other end connector which are inserted into the recess blocks. The recess blocks are arranged at two adjacent quarters of the end plate, and the projecting pins are arranged at the other adjacent quarters of the end plate, and one side wall of the skirt is provided with an opening, which is aligned with openings in the two recess blocks. The side pin of one end connector extends into the same side face of the joined concrete pile as the side pin of the other end connector. The two pins for forming the join can be hammered into the same face, so that the pile driver mast does not obscure access.

Description

This invention relates to a coupling arrangement for interlocking adjacent ends of concrete piles.
In the construction of foundations, an extended length continuous concrete pile may be formed by joining two or more pile units end to end. The requirement for piles of extended length is increasing. As structures are built taller and with greater concentration of weight, deeper foundations are required. Precast concrete piles are typically formed up to 15m in length, and it is very common for two lengths to be connected together.
Concrete piles as in the preamble of claim 1 are known e.g. by DE-8504456U .
A precast concrete pile is formed by casting concrete around a steel reinforcing cage. This cage typically comprises longitudinal reinforcing bars, and transverse reinforcement which winds around the reinforcing bars. In the case of a square cross section pile, the reinforcing bars run near the corner edges of the pile.
The joint between the sections must have a cross section no larger than the non-jointed section of the piling. The joints should also be as strong as the non-jointed piling in order to remain straight so that the jointed pile will drive vertically true during the high stress pile driving process.
A number of concrete pile joint arrangements have been disclosed in the past, and different joint designs have been proposed for different applications.
In situations where the ability to withstand high tensile forces may be required, a bayonet type interlocking arrangement has been used, and this comprises steel end plates which are attached (during the casting of the concrete pile) to the ends of the piles. The steel end plates have accurately formed interlocking arrangements. Typically, these interlocking arrangements are engaged by rotating one pile with respect to the other. This coupling is made after the first pile has been driven into the ground, and is a heavy labour intensive task.
For this reason, an alternative joint design is used, and this is shown in Figure 1. The joint is arranged as two end connectors 10, 12 which are coupled to the concrete pile section during the casting process.
Each end connector 10, 12 comprises a cap 14 having an end plate and a skirt, arranged as a square for a square cross section pile. The cap 14 has two projecting pins 16 and two recesses 18 (as can be seen more clearly in Figure 2). The caps plug together with two diagonally opposite pins 16 in one cap projecting into two diagonally opposite recesses in the other cap.
The recesses are formed in a recess block 20 which is cast with or welded to the cap 14, and the block has a bore 22 which extends to a side face 23 of the cap. The projecting pins 16 also have a bore 24, and when coupled together, the joint is secured with transverse pins 26, one of which is shown in Figure 1. Figure 1 also shows plastic end covers 25.
The projecting pins 16 and recess blocks 20 are connected to anchor rods 27 which extend into the concrete, and the concrete is cast around these anchor rods 27. The effect of the joint is to provide a continuous anchor rod extending across the joint, and these anchor rods extend into the piles a sufficient distance to provide the required strength properties of the joint. For example, they may be 500mm to 10000mm long.
Figure 2 shows one pile section in end view including the end connector. The two pins 26 (not shown in Figure 2) are provided in bores on opposite sides of the pile section. Identical end connectors can be used, with a 90 degree relative rotation. This means that the connected joint has a bore on all four faces. Alternatively, one end connector can be a mirror image of the other, and this results in the connected joint having bores only on two opposite faces.
The installation of a pile using sections with this type of joint involves hoisting the first pile section upright, and driving it into the ground. When the top of the first pile section is near ground level, the next pile section is then lowered on top, and the cross pins 26 are inserted through the bores 22,24 to make the joint. The coupled pile sections are then driven further into the ground.
A problem with this method is encountered during the pile driving stage, and this problem arises particularly from the way in which the piles are manufactured.
Figure 3 shows schematically how the precast pile sections are made. A mould 28 comprising a number of parallel channels 30 is used. The end connector 14 is mounted in place before the concrete fills the mould, and the reinforcing structure is also put in place (not shown). The reinforcing structure includes a lifting hook 32 which projects beyond a side face of the pile, and is used by the lifting hoist. This necessarily is at the top of the mould channel and therefore faces upwardly. Equally, one of the bores 22 faces upwardly and the other faces downwardly. The voids are formed by steel blocks which are sealed such that no concrete can enter them during the concrete casting process.
It can be seen that the preferred manufacturing process results in the lifting hook 32 and at least one of the bores 22 being on opposite faces of the manufactured pile. This gives rise to a problem when installing the pile. In particular, the pile section is lifted by a hoist using the lifting hook and is then put in front of the mast of the pile driving equipment. The mast of the pile driving equipment thus blocks easy passage to the side of the pile opposite the handle, and the mast is therefore in the way of the bore 22 that was at the bottom of the channel during the casting process. This impedes the operation of hammering in the pins which complete the joint.
According to the invention, there is provided a concrete pile comprising first and second concrete pile sections joined together by respective end connectors, each end connector comprising:

an end plate covering an end of the pile section;
two recess blocks fixed to an inner part of the end plate;
two projecting pins fixed to an outer part of the end plate; and
a side pin for insertion through the two recess blocks, thereby to retain projecting pins of the other end connector which are inserted into the recess blocks,
wherein the recess blocks are arranged at two adjacent quarters of the end plate, and the projecting pins are arranged at the other adjacent quarters of the end plate, and wherein the openings in the two recess blocks are aligned,
and wherein the side pin of one end connector extends into the same side face of the joined concrete pile as the side pin of the other end connector.

This arrangement aligns the two pins and the two projections parallel to the sides of the pile section. The opening in the side wall is aligned with both recess block openings so that a single pin can be used for both recess blocks. Each single pin can then be hammered into one face only, and this simplifies the site connection of the two halves and improves the site production process.
By extending the two side pins into the same side face of the joined concrete pile, two pins can be hammered into the same face of the joint to complete the joint, and this face can also be the same face as the face carrying a lifting hook, so that the pile driver mast does not obscure access.
Preferably the end plate has a skirt into which the pile section is cast, wherein one side wall of the skirt is provided with an opening which is aligned with openings in the two recess blocks, and wherein the side pin is further for insertion through the opening in the skirt side wall.
Each recess block and each projecting pin is preferably connected to an anchor bar which extends in the longitudinal pile direction. The connector preferably includes the side pin for insertion through the opening in the side wall and through the two recess blocks, thereby to retain projecting pins of another end connector which are inserted into the recess blocks.
To form the opening for the side pin, a removable insert can be provided for insertion through the opening in the side wall and through the two recess blocks, for defining a bore during casting of a concrete pile section including the end connector. The defined bore is then for receiving the side pin.
Each concrete pile section preferably also has a reinforcement cage placed into the skirt of the end plate into which concrete is cast. The cast concrete then defines a lateral bore extending from the opening in the side wall of the skirt to the first recess block and between the first and second recess blocks.
The reinforcement cage may comprise longitudinal reinforcement bars and transverse reinforcement which winds around the longitudinal reinforcement bars. Lifting handles, for example steel hooks, can be cast into the top surface of the concrete to allow for lifting the pile section from the mould after concrete hardening.
The invention also provides a method of assembling a concrete pile section, comprising joining first and second pile sections, each pile section comprising an end connector comprising:

an end plate covering an end of the pile section;
two recess blocks fixed to an inner part of the end plate;
two projecting pins fixed to an outer part of the end plate; and
a side pin for insertion through the two recess blocks, thereby to retain projecting pins of the other end connector which are inserted into the recess blocks,
wherein the recess blocks are arranged at two adjacent quarters of the end plate, and the projecting pins are arranged at the other adjacent quarters of the end plate,
wherein the joining comprises:
inserting the pins of one end connector into the recess blocks of the other end connector to mount the pile sections together; and
inserting a side pin into each end connector of the mounted concrete pile sections, into the same side face.

An example of the invention will now be described in detail with reference to the accompanying drawings, in which:

Figure 1 shows a known connector assembly for concrete pile sections in side view;
Figure 2 shows an end view of a pile section of Figure 1;
Figure 3 is used to explain a known manufacturing method;
Figure 4 shows a connector assembly of the invention for concrete pile sections in side view;
Figure 5 shows an end view of a pile section of Figure 4;
Figure 6 is used to explain the manufacturing method of the invention;
Figure 7 shows a design for the connecting pin in a further example of the invention;
Figure 8 shows an example of dimensions of the various components to enable the pin of Figure 7 to be used; and
Figure 9 shows how the pin of Figure 7 can be used to clamp components together.

Figures 4 and 5 show a concrete pile joint arrangement of the invention, and show the same views as Figures 1 and 2. Furthermore, the same reference numerals are used to denote components having the same function, and a description of the function of these components will not be repeated.
The joint arrangement of the invention has the two recess blocks 20 arranged in two adjacent quarters of the end plate, and the projecting pins 16 arranged in the other two adjacent quarters of the end plate.
This can be seen most clearly in Figure 5, which shows the projections in the top left and top right quarters of the end face of the end connector 14, and the recess blocks 20 and recesses 18 in the bottom left and bottom right quarters of the end face.
In this way, the two pins 16 and the two recesses 18 are aligned parallel to the sides (the top and bottom sides in the orientation of Figure 5) of the pile section. This means that a single pin which is inserted through the skirt side wall of the end connector can pass through both recess blocks and the pins located in those blocks. As a result, a single pin 26 can be inserted from one face only to make the connection for two pinrecess pairs, and this avoids obstruction of the face by the pile driver mast.
One side wall of the skirt of the end connector 14 is provided with an opening 40 which defines the pin entrance, and this opening 40 is aligned with the bores 22 in the two recess blocks 20.
The joint design of the invention further differs from the arrangement of Figure 1 and 2 in that the recess blocks 20 are made smaller, and the passageway 41 for the pin 26 is defined through part of the cast concrete as well as through the bores 22 of the recess blocks. A passageway therefore needs to be defined as part of the casting process.
The pile section is cast in the same way as explained with reference to Figure 2. However, during the casting process, an insert is provided through the opening 40 and through the two recess blocks 20 so that the passageway 41 is defined by the insert, in particular the passageway from the opening 40 to the first recess block 20 and between the two aligned recess blocks.
This insert 60 is shown in Figure 6. The insert is removed after the casting process, and the opening 40 can then be used for insertion of the pin 26.
The casting process is then conventional, and an inner reinforcement cage is again used, as well as defining the lifting hook 32.
In the joined pile, the two pins 26 are inserted from the same face. This can be achieved by having end connectors which are mirror images of each other. However, it can also be achieved with identical end connectors by providing an additional opening in the skirt at the location 42 as shown in Figure 5. One end connector can then be a 180 degree rotation of the other, and the insert can be inserted from the opposite side during casting, by mounting the end connector into the mould channel the opposite way up.
A further modification can be used to make the insertion of the pin 26 easier. With reference to Figure 5, when the pin is inserted, it passes through a portion of the hole in the concrete, then through a first projecting pin 16, then through a further concrete section between the projecting pins, through a second projecting pin 16, then through a final concrete section. If the pin 26 is a tight fit through all of these passageways, the insertion of the pin 26 becomes difficult.
This problem is resolved by providing a pin with different diameter sections, as shown in Figure 7. The pin 70 has a distal end part 72 of first diameter, for example 15mm. This part of the pin is for the further projecting pin/recess pair, and the openings in the projecting pin and recess of this pair are dimensioned appropriately.
A proximal end part 74 (i.e. at the end where the pin will be hammered) has a larger diameter, for example 16mm. This part of the pin is for the nearer projecting pin/recess pair, and the openings in the projecting pin and recess of this pair are again dimensioned appropriately.
The pin has two tapered transition regions 76 and these assist in driving the pin into the openings. As will be described below, the openings are designed not to be perfectly aligned so that the pins operate to tension the coupling.
Figure 8 shows the dimensions for the openings in the pins 16 and recess blocks 20. As shown, the 15mm diameter part of the pin is for insertion through 16mm openings, and the 16mm diameter part of the pin is for insertion through 17mm openings. Furthermore, the opening cast in the concrete can be larger than the pin, for example the casting pin can be an enlarged version of the pin of Figure 17, which has 17mm and 16mm diameter sections. The insert pin used for casting is thus a snug fit in the openings of the recess blocks, to prevent concrete spillage into the recess blocks, but provides a larger opening than the connecting pin size.
This means that when driving the pin into the joint, there is no resistance from the concrete bore defined by the insert pin 26.
In order to provide a strong coupling, even though the openings in the recess blocks and the projecting pins are larger than the connecting pin, the openings in the projecting pin and recess block are not aligned but are offset along the longitudinal axis. This is shown in Figure 9. Taking the example of the first pin/recess pair, with 17mm diameter, the distal 15mm diameter part of the pin passes through relatively easily, but the 16mm part of the pin forces the projecting pin and recess together, thereby clamping the parts together. This is because the overlap of the two openings is less than 16mm in height.
The tapered parts 76 enable the clamping to be effected smoothly.
The distal tapered part can engage the furthest projecting pin/recess pair, and then the proximal tapered part can engage the nearest projecting pin/recess pair, although this engagement may be in the opposite order or simultaneous.
In order to implement the offset explained above, the dimensions X and Y shown in Figure 8 are slightly different.
The dimensions above are only by way of example to explain the engagement of the pins and recesses, and it will be appreciated that the components can all be scaled to different sizes.
This pin design makes the connection operation easier, as there is less resistance to the driving of the pin, but the pin still provides a firm tensioned coupling between the projecting pins and recess blocks.
The example above shows a square cross section pile, but this is not essential. The materials and manufacturing process for the end plates will be routine and apparent to those skilled in the art.
Various other modifications will be apparent to those skilled in the art.

Claims

A concrete pile (32) comprising first and second concrete pile sections joined together by respective end connectors (14), each end connector comprising:
an end plate covering an end of the pile section;

two recess blocks (20) fixed to an inner part of the end plate; and

two projecting pins (16) fixed to an outer part of the end plate; and

a side pin (60) for insertion through the two recess blocks, thereby to retain projecting pins of the other end connector which are inserted into the recess blocks, characterized in that

the recess blocks are arranged at two adjacent quarters of the end plate, and the projecting pins (60) are arranged at the other adjacent quarters of the end plate, and wherein the openings (18) in the two recess blocks are aligned,

and wherein the side pin of one end connector extends into the same side face of the joined concrete pile as the side pin of the other end connector.
A concrete pile as claimed in claim 1, wherein the end plate (14) has a skirt into which the pile section is cast, wherein one side wall of the skirt is provided with an opening (18) which is aligned with openings in the two recess blocks, and wherein the side pin (60) is further for insertion through the opening in the skirt side wall.
A concrete pile as claimed in claim 1 or 2, wherein each recess block and each projecting pin is connected to an anchor bar (24) which extend in the longitudinal pile direction.
A concrete pile as claimed in any preceding claim, wherein the side pin (60) has a first, distal portion of a first diameter and a second, proximal portion (26) of a second larger diameter.
A concrete pile as claimed in any preceding claim, wherein the openings (18) in the two recess blocks of each end connector are of different diameters.
A concrete pile as claimed in claim 5, wherein the opening diameter of each recess block is larger than the diameter of the portion of the side pin (60) to be inserted through the recess block (20).
A concrete pile as claimed in any preceding claim, wherein the projecting pins (16) each have an opening (17), and wherein the projecting pins and recess blocks are designed such that, with a projecting pin of one end connector received in the recess block of the other end connector, the opening of the projecting pin is partially offset from the opening of the recess block.
A concrete pile as claimed in any preceding claim, wherein each pile section comprises:
a reinforcement cage; and

concrete cast around the cage cast into the skirt of the end connector (14),

wherein the cast concrete defines a bore extending from the opening in the side wall of the skirt to the first recess block (20) and between the first and second recess blocks.
A concrete pile (32) as claimed in claim 8, wherein the reinforcement cage comprises longitudinal reinforcement bars and transverse reinforcement winding around the reinforcement bars
A concrete pile (32) as claimed in claim 8 or 9, further comprising a lifting device extending from the same face of the pile section as the face into which the bore extends.
A method of assembling a concrete pile section, comprising joining first and second pile sections, each pile section comprising an end connector (14) comprising:
an end plate covering an end of the pile section;

two recess blocks (20) fixed to an inner part of the end plate;

two projecting pins (16) fixed to an outer part of the end plate; and

a side pin (60) for insertion through the two recess blocks, thereby to retain projecting pins of the other end connector which are inserted into the recess blocks,

wherein the recess blocks are arranged at two adj acent quarters of the end plate (14), and the projecting pins are arranged at the other adjacent quarters of the end plate,

wherein the joining comprises:
inserting the pins (60) of one end connector into the recess blocks of the other end connector to mount the pile sections together; and

inserting a side pin into each end connector of the mounted concrete pile sections, into the same side face.