GB1595629A

GB1595629A - Structural joints

Info

Publication number: GB1595629A
Application number: GB24679/78A
Authority: GB
Original assignee: Pilgrim Engineering Developments Ltd
Current assignee: Pilgrim Engineering Developments Ltd
Priority date: 1978-05-31
Filing date: 1978-05-31
Publication date: 1981-08-12
Also published as: DE2921803A1; JPS54158001A; FR2427503A2; AU4737379A; IT7923046A0; IT1166859B; NO791712L; NL7904260A

Description

(54) IMPROVEMENTS IN STRUCTURAL JOINTS (71) We, PILGRIM ENGINEERING DEVELOPMENTS LIMITED, a British company, of Beaufort House, St. Botolph Street, London, EC3A 7DX, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: The present invention relates to improvements in structural load-transmitting joints. It is concerned especially with a joint for fastening offshore platforms to piles sunk into the sea bed. However it can be applied to other forms of structural joints, for example, joints between elements of a framework. The invention is a modification of the invention disclosed in our Patent Application No.

30282/75 (Serial No. 1,569,104).

In the above mentioned application we described a pipe coupling. The present invention concerns the application of the principle of that pipe coupling to structural joints.

According to the present invention a structural load-transmitting joint comprises a structural tubular member and a sleeve for fitting around the structural tubular member, the sleeve carrying means for gripping the tubular structural member, the gripping means comprising a series of axially-spaced circumferentially-extending groove sections on the inside of the sleeve which accommodate jaw sectors with gripping edges, the groove sections being joined together to form one or more continuous channels and an expandable tubular member or members located in the groove behind the jaw sectors, the tubular member or members communicating with the exterior through bores extending through the wall of the sleeve, the arrangement being such that the interior of the tubular member or members can be filled through the bores with a hardenable composition to cause the gripping teeth of the jaw sectors to bite into the outer surface of the tubular structural member, and maintained under pressure until set.

Preferably the sleeve includes means for sealing the sleeve against the structural member at two axially spaced positions along the member on opposite sides of the gripping means, the sealing means comprising two annular grooves each of which accommodates an annular tyre, the interior of the tyres communicating with the exterior through bores in the wall of the sleeve, the arrangement being such that the annular tyres can be filled with a hardenable composition and maintained under pressure until set to maintain the sealing means in sealing contact with the outer surface of the structural tubular member.The sealing means enables the interface between the sleeve and the structural tubular member around the gripping means to be drained through a further bore in the wall of the sleeve and then filled with a hard-setting grout such as cement or an epoxy resin composition.

In some applications the sleeve may be formed as a single piece encircling the structural member in which case the groove sections of the gripping means may be formed by the convolutions of a helical groove and the tubular member may be a single helical tubular member, the interior of which communicates with the exterior of the sleeve through bores at its ends. In other cases the sleeve may be formed in two parts separated from one another along a longitudinal plane through the axis of the sleeve. The two parts may be coupled to one another along their longitudinal pair of edges by bolts which pass through flanges along the longitudinal edges. The latter arrangement may facilitate the placing of the sleeve in position under difficult conditions such as for example when repairing structural member.

In case of a sleeve formed in two parts as described above the groove section of the gripping means may be in the form of a continuous sinuous groove with groove sections extending from one longitudinal edge to the other, the groove sections being connected alternatively at opposite edges by semi-circular sections and the tubular member may be in the form of a separate single tubular member for each part of the sleeve, the interior of the tubular members communicating with the exterior through bores in the wall of the pipe at both ends.

In the case where the invention is used as a pile clamp, for an offshore structure, and a pair of sleeves according to the invention may be secured to the offshore structure and aligned axially with one another for receiving the pile so that the pile can be clamped to the structure at two vertically spaced positions. Usually there will be several piles securing structure to the seabed and the joint of the invention may be used for only one of the piles, the first to be driven into the seabed or it may be used for more than one of the piles.

Embodiments of the invention will now be described, by way of example, with reference to the accompanying drawings, of which: Figure 1 shows an elevation of a pile clamping arrangement according to the invention; Figure 2 shows a longitudinal section on an enlarged scale of one of the sleeves of the arrangement of Figure 1; and Figure 3 shows a transverse fragmentary cross-section on an enlarged scale of sleeve of Figure 2.

Referring to Figure 1 this shows a fragmentary view of an offshore structure 10 secured to the sea bed 11 by means of piles such as the pile 12 shows in Figure 1.

The offshore structure consists of a framework of tubular structural elements including corner legs such as the leg 13 shown in Figure 1. Secured to the corner leg 13 on brackets 14 near its lower end are two clamping sleeves 15. The sleeves 15 are aligned with one another in the axial direction and spaced apart vertically.

Each sleeve 15 comprises at its upper end an entry cone 16 to assist in guiding the pile as it is lowered into the sleeve.

As shown in Figure 2, two annular grooves 17 are provided in the inner surface of each of the sleeves 15 at its opposite ends. An annular elastomeric tyre 18 is accommodated in each of the grooves 17 and the interior of each tyre communicates with the exterior through two bores 19 in the wall of the sleeve.

One of bores 18 constitutes an inlet port for injection of an epoxy resin composition and is provided with a filling pipe 20 which is connected to a manifold 21 (see Fig. 1). The other bore 19 at the top of the sleeve constitutes an exhaust port for air and are provided with an air bleed valve (not shown).

Between the annular grooves 18 is a helical groove 22 in the inside surface of the sleeve 15. Many jaw sectors 23 of tough steel are accommodated in series in the groove 22. The jaw sectors 23 are a close fit in the grooves.

Fish plates 24 bridge the gaps between the jaw sectors. The jaw sectors have teeth on their inner surfaces in the form of shallow 0.005 to 0.010 inch grooves which provide gripping edges which bite into the outer surface of the pile to provide the required axial load-bearing capacity. In the groove 22 behind the jaw sectors 23 is a deformable nitrile rubber helical tube 25 which forms a load cell. The ends of the helical tube pass out through the bores 26 in the wall of the sleeve 15 to the exterior.

One end of the tube is connected to an air bleed valve (not shown) and to a return pipe (also not shown), the other is connected to the manifold 21 by a filling pipe 27.

The space between the sleeve 15 and the pile 13 is connected to the exterior by two further bores 28 extending through the wall of the sleeve. One of the bores 28 serves as an exhaust port and is fitted with an air bleed valve (not shown). The other bore 28 serves as a filling port and is connected by a filling pipe 29 to the manifold 21.

The manifolds 21 associated with the two coupling sleeves 15 are connected to a pump at the surface of the sea by a supply pipe 30 and incorporate remotely controlled valves whereby the supply pipe can be selectively connected to one or more of the filling pipes 20, 27 and 29.

To secure the offshore structure to the sea bed once it has been set in position, one may proceed as follows. The pile 13 is lowered into position, being threaded first through the upper coupling sleeve 15 and then through the lower coupling sleeve 15. Once in position it is driven into the sea bed. If a temporary clamping of the structure to the pile is required, for example, when the pile driving operation is interrupted by the onset of rough weather, hydraulic fluid may be pumped down the supply pipe, through the manifolds 21 and the filling pipes 27 and into the tubular members 25. The hydraulic fluid may conveniently be water.The pressure of the fluid expands the tubular members 25 which are constrained laterally by the helical grooves 22 and therefore forces the jaw sectors of each coupling sleeve into contact with the pile to clamp the pile in the two coupling sleeves and thus fix the pile to the offshore structure. When the weather has settled the clamping may be released by releasing the pressure and allowing the fluid to bleed away from the tubular members.

Once the pile has been driven fully into the sea bed a permanent clamping of the structure to the pile may be effected as follows. After purging any hydraulic fluid from the helical tubes, if necessary, a hardenable composition such as an epoxy resin composition is pumped through the supply pipe 30, the manifold 21 and the filling pipes 27 into the helical tubes 25. Each tube fills with the resin composition from one end, the resin composition displacing the air in front of it until the composition reaches the air bleed valve which it closes. The pressure of the resin in the tubes 25 is then raised to the pressure at which it is delivered from the pump causing the tube to expand and force the jaw sectors 23 against the outer surface of the pile. The edges of the teeth bite into the surface of the pile to grip the pile.

The epoxy resin composition is maintained under pressure until set so that the gripping force is maintained. Hardenable epoxy resin composition is then pumped through the manifolds and the filling pipes 20 into the tyres 18.

The resin composition displaces the air in the tyres and exhausts it through the air bleed valves. When the epoxy resin composition reaches the air bleed valve it automatically closes the valve so that the pressure of the composition in the tyres can be raised to the pressure at which it is delivered from the pump. Under this pressure the tyres which are of nitrile rubber expand out of the grooves and are pressed into sealing contact with the surface of the pile 13. The epoxy resin composition is then maintained under pressure until set.

To finish the coupling the sealed space between the pile and the sleeves which lies between the annular grooves 17 is drained of sea water and prepared as necessary, for example by washing down with a solvent, for the injection of a hard setting grout of cement or an epoxy resin composition. The grout is pumped down the supply pipe 30, through the manifolds 21, the filling pipes 29 and into the spaces. The grout is pressured before curing and on hardening provides rigid lateral support against any side forces and bending moments arising between the pipe and its clamp on the structure. The pressurising of the grout ensures minimum void spaces in the grout and interference pressures between the grout and pile and coupling surfaces.

The coupling provides a rapid fastening of piles or other tubular structural members, both for temporary and permanent clamping purposes. The coupling grips the pile or tubular member against axial loads by means of teeth making indentations into the pile surface. The coupling provides lateral location of the pile by means of a hard setting grout injected under pressure and contained between end pressurized seals. These seals also provide protection against ingress of sea warer and the resultant possibility of corrosion damage.

The arrangement offers substantial weight reductions compared with the current designs of sleeved, grouted pile joints, and that the weight savings and installation time savings will reduce the total installation costs.

It will be appreciated that other applications of the invention are possible such as for joining together tubular bracing elements of framework structures or for repairing damaged structural elements.

WHAT WE CLAIM IS:- 1. A structural load-transmitting joint comprising a structural tubular member and a sleeve for fitting around the structural tubular member, the sleeve carrying means for gripping the tubular structural member, the gripping means comprising a series of axiallyspaced circumferentially-extending groove sections on the inside of the sleeve which accommodate jaw sectors with gripping edges, the groove sections being joined together to form one or more continuous channels and an expandable tubular member or members located in the groove behind the jaw sectors, the tubular member or members communicating with the exterior through bores extending through the wall of the sleeve, the arrangement being such that the interior of the tubular member or members can be filled through the bores with a hardenable composition to cause the gripping teeth of the jaw sectors to bite into the outer surface of the tubular structural member, and maintained under pressure until set.

2. A joint according to claim 1 in which the sleeve has means for sealing the sleeve against the tubular structural member at two axially spaced positions along the member on opposite sides of the gripping means, the sealing means comprising two annular grooves, each of which accommodates an annular tube, the interior of the tube communicating with the exterior through bores in the wall of the sleeve, the arrangement being such that the tubes can be filled with a hardenable composition and maintained under pressure until set.

3. A joint according to claim 2 in which a hole is provided through the wall of the sleeve between the two annular grooves.

4. A joint according to any of claims 1 to 6 in which the sleeve is formed as a single piece encircling the tubular structural member and the groove sections of the gripping means are formed by the convolutions of a helical groove, the tubular member being a helical tube.

5. A joint according to claim 4 in which the helical tube communicates with the exterior through bores at both ends of the sleeve.

6. An assembly comprising an offshore structure and a joint according to any of claims 1 to 5, the tubular structural member comprising a pile driven into the sea bed and the sleeve being secured to the offshore structure.

7. An assembly according to claim 6 in which two such sleeves are secured to the offshore structure and aligned axially with one another, the pile extending through both sleeves.

8. A joint substantially as described hereinbefore with reference to Figures 1 to 3 of the accompanying drawings.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. under pressure until set so that the gripping force is maintained. Hardenable epoxy resin composition is then pumped through the manifolds and the filling pipes 20 into the tyres 18. The resin composition displaces the air in the tyres and exhausts it through the air bleed valves. When the epoxy resin composition reaches the air bleed valve it automatically closes the valve so that the pressure of the composition in the tyres can be raised to the pressure at which it is delivered from the pump. Under this pressure the tyres which are of nitrile rubber expand out of the grooves and are pressed into sealing contact with the surface of the pile 13. The epoxy resin composition is then maintained under pressure until set. To finish the coupling the sealed space between the pile and the sleeves which lies between the annular grooves 17 is drained of sea water and prepared as necessary, for example by washing down with a solvent, for the injection of a hard setting grout of cement or an epoxy resin composition. The grout is pumped down the supply pipe 30, through the manifolds 21, the filling pipes 29 and into the spaces. The grout is pressured before curing and on hardening provides rigid lateral support against any side forces and bending moments arising between the pipe and its clamp on the structure. The pressurising of the grout ensures minimum void spaces in the grout and interference pressures between the grout and pile and coupling surfaces. The coupling provides a rapid fastening of piles or other tubular structural members, both for temporary and permanent clamping purposes. The coupling grips the pile or tubular member against axial loads by means of teeth making indentations into the pile surface. The coupling provides lateral location of the pile by means of a hard setting grout injected under pressure and contained between end pressurized seals. These seals also provide protection against ingress of sea warer and the resultant possibility of corrosion damage. The arrangement offers substantial weight reductions compared with the current designs of sleeved, grouted pile joints, and that the weight savings and installation time savings will reduce the total installation costs. It will be appreciated that other applications of the invention are possible such as for joining together tubular bracing elements of framework structures or for repairing damaged structural elements. WHAT WE CLAIM IS:-

1. A structural load-transmitting joint comprising a structural tubular member and a sleeve for fitting around the structural tubular member, the sleeve carrying means for gripping the tubular structural member, the gripping means comprising a series of axiallyspaced circumferentially-extending groove sections on the inside of the sleeve which accommodate jaw sectors with gripping edges, the groove sections being joined together to form one or more continuous channels and an expandable tubular member or members located in the groove behind the jaw sectors, the tubular member or members communicating with the exterior through bores extending through the wall of the sleeve, the arrangement being such that the interior of the tubular member or members can be filled through the bores with a hardenable composition to cause the gripping teeth of the jaw sectors to bite into the outer surface of the tubular structural member, and maintained under pressure until set.