The present invention relates to a mounting system and method that can be used, for example in the installation of devices on the bed of a body of water such as the sea bed. The devices to be installed may, for example, be renewable energy devices that can be used to capture wave, tidal, current, wind or solar energy in offshore environments or may, for example, be devices used in oil or gas exploration or production, or in telecommunication systems.
There has been vast activity in recent years in the development of renewable energy technology. Many renewable energy devices systems are intended for installation offshore, for example wave power devices, wind turbines, water current devices and tidal devices. Many other devices also need to be installed on the sea bed, for example oil or gas installations or communication devices.
There can be significant technical difficulties in installing devices offshore, for example mounting devices on the seabed, as such devices are subject to significant wave, tidal and other forces both during installation and after use. The devices must be able to cope with the extreme conditions that they may encounter during their lifetime. Many devices will be subject to significant lateral or heave forces.
It is known to drive piles into the bed of a body of water and then mount devices to the piles. The usual way of mounting the devices is to grout them into place using concrete or similar material. Such grouting procedures can be difficult and messy, require calm sea conditions and require divers to perform many of the grouting operations. It is critical that the devices are aligned correctly while the concrete or other grouting material sets. If a device is subsequently to be removed it may be necessary to destroy the grouting material in order to remove the device.
In a first, independent aspect of the invention there is provided a mounting system comprising a base and a mounting structure for mounting to the base, wherein one of the base and the mounting structure comprises a bearing comprising a resiliently deformable member and having a bearing surface, the other of the base and the mounting structure comprises a further bearing surface for engagement with the bearing surface of the bearing, and the bearing is configured so that shear stress of the deformable member when the mounting structure is mounted to the base biases the bearing surface towards the further bearing surface. The shear stress may be in an engagement direction.
The mounting structure may be for attachment to, or may comprise, a further structure, for example a wave power device. The mounting structure may be for attachment to, or may comprise, a tidal energy device, a water current device, a wind turbine mast or other mast, an oil or gas production or exploration-related structure, or a structure relating to telecommunication installations. The mounting structure may be for installation on the bed of a body of water.
One of the base and the mounting structure may comprise a plurality of the bearings each comprising a resiliently deformable member and having a bearing surface, and the other of the base and the mounting structure comprises a plurality of the further bearing surfaces, each further bearing surface being arranged for engagement with the bearing surface of a respective one of the bearings.
Each of the plurality of bearings may comprise a discrete bearing and/or may be not in contact with each other bearing.
A first one of the bearings may be substantially opposed to a second one of the bearings, such that a reduction in compression of the first bearing causes an increase in compression of the second bearing.
The system may be configured so that reduction in compression of at least one of the bearings causes a release in shear stress, thereby to move the mounting structure and/or at least one of the bearings towards the base.
Lateral movement of the mounting structure in alternating directions may cause alternating bearing surfaces to move relative to corresponding further bearing surfaces thereby to move the mounting structure and/or the bearings towards the base.
In operation the lateral movement may be caused by action of waves, tides, currents or wind on the mounting structure or on a further structure attached to the mounting structure.
The mounting structure may have an engagement axis, the base may have an engagement axis and the mounting structure may be mounted to the base by moving the base and the mounting structure into contact with the engagement axis of the base and the engagement axis of the mounting structure substantially aligned.
The base and the mounting structure may be configured such that when the bearing surfaces and the further bearing surfaces are brought into contact without the at least one resiliently deformable member being under compressive and/or shear stress, there is a gap between an engagement surface of the mounting structure (for example a bottom surface of the mounting structure) and a corresponding surface of the base. The base and the mounting structure may be configured such that movement of the engagement surface into contact with the corresponding surface of the base (for example under the action of gravity on the mass of the mounting structure) causes compressive and/or shear stress in the at least one resiliently deformable member.
The shear stress of the deformable member that biases the bearing surface towards engagement with the further bearing surface may be shear stress in a direction substantially along the engagement axis, for example in a substantially downward direction along the engagement axis.
For the or each bearing, the bearing surface may be inclined with respect to the engagement axis of one of the base or mounting structure, and the further bearing surface may be inclined with respect to the engagement axis of the other of the base or mounting structure.
For the or each bearing and further bearing surface, the bearing surface may be inclined with respect to the engagement axis of one of the base or mounting structure by a bearing angle, and the further bearing surface may be inclined with respect to the engagement axis of the other of the base or mounting structure by a further bearing angle, and the bearing angle and the further bearing angle may be substantially identical.
For the or each bearing and further bearing surface, the angle between the bearing surface and the engagement axis of one of the mounting structure and the base may be less than the inverse tangent of the coefficient of friction between the bearing surface and the further bearing surface.
The base may be arranged so that when the mounting structure is mounted to the base the engagement axis of the mounting structure and the engagement axis of the base are aligned with the vertical.
The base and the mounting structure may be configured so that the bearing surface and the further bearing surface are arranged to be in sliding engagement with one another when the mounting structure is mounted to the base.
The at least one resiliently deformable member may have substantially different elasticity in different directions, optionally the different directions are a radial direction and an axial direction.
For the or each bearing, the ratio of the stiffness of the deformable member under compressive load to the stiffness of the deformable member under shearing load may be between 100:1 and 10,000:1, optionally between 1,000:1 and 10,000:1, optionally between 500:1 and 2,000:1, optionally greater than 1,000:1.
For the or each bearing, one side of the resiliently deformable member of the bearing may be attached to a body of one of the base and the mounting structure, and the bearing surface may comprise a substantially non-deformable material attached to the other side of the resiliently deformable material.
The substantially non-deformable material of the bearing surface may comprise a substantially rigid layer.
For the or each bearing and bearing surface, the bearing surface and/or the further bearing surface may comprise non-elastomer material, optionally at least one of steel, tungsten carbide, cobalt and/or chromium, further optionally tungsten carbide in a cobalt and chromium matrix.
The resiliently deformable member may comprise an elastomer. The resiliently deformable member may also comprise at least one non-elastomer.
The elastomer may comprise at least one of rubber, for example natural rubber, neoprene or polypropelene.
The resiliently deformable member may comprise a laminated structure, optionally comprising a plurality of elastomer layers interspersed with at least one non-elastomer layer.
The at least one non-elastomer layer may comprise a substantially rigid layer, optionally at least one plate.
The non-elastomer may comprise substantially rigid material, for example metal. The non-elastomer may comprise steel.
The non-elastomer may comprise substantially non-deformable material. The substantially non-deformable material may be bonded to the resiliently deformable member or members.
The resiliently deformable member may comprise a body of at least one first material and a surface layer of a second, different material on the body and comprising the bearing surface.
For the or each bearing and further bearing surface, the bearing surface and/or the further bearing surface may comprise non-elastomer material, optionally at least one of steel, tungsten carbide, cobalt and/or chromium, further optionally tungsten carbide in a cobalt and chromium matrix.
At least one of the bearing surface and the further bearing surface may be textured, for example at least one of grooved, ridged or roughened, thereby to provide a desired fiction coefficient.
One of the base and the mounting structure may comprise a male portion and the other of the base and the mounting structure may comprise a female portion, and the base and the mounting structure may be configured so that the male portion mates with the female portion when the mounting structure is mounted to the base.
The male portion may comprise a spigot and/or the female portion may comprise a socket.
One of the male portion and the female portion may comprise the bearing or each of the bearings and the other of the male portion and the female portion may comprise the further bearing surface or at least one of the further bearing surfaces.
The bearing or bearings may be formed and arranged so that when the male portion is inserted into the female portion, the resiliently deformable member is, or resiliently deformable members are, deformed and held in shearing tension in an axial direction of the mounting structure.
The bearing surfaces, or the further bearing surfaces, may be disposed circumferentially around the male portion and may slope radially inwards in the direction of insertion of the male portion.
The bearing surfaces and the further bearing surfaces may be formed for gripping contact when the male portion is inserted into the female portion.
The bearings may be disposed circumferentially around the female portion and project radially inwards therefrom; or the bearings may be disposed circumferentially around the male portion and project radially outwards therefrom.
The system may further comprise means for applying shear force to the or each deformable member. The means for applying shear force may be operable to apply shear force when the base and the mounting structure are not engaged together. The means for applying shear force may comprise at least one of a ring beam and a tension member.
The system may further comprise means for releasing the mounting structure from the base.
The releasing means may comprise at least one of:—means for applying force to one of the base and the mounting structure; means for changing the friction between the at least one bearing surfaces and the at least one further bearing surface, for example by lubricating the at least one bearing surface and/or the at least one further bearing surface; means for altering the compressive load between the at least one bearing surface and the at least one further bearing surfaces; or means for altering the angle of inclination of at the at least one bearing surface and/or the at least one further bearing surfaces.
The releasing means may comprise at least one of a plurality of jacks or a fluid supply means for providing fluid to the interface between the at least one bearing surface and the at least one further bearing surface.
In a further, independent aspect of the invention there is provided a bearing for attachment to a base or a mounting structure, the bearing comprising a resiliently deformable member and a bearing surface for engagement with a further bearing surface, wherein the bearing is configured so that shear stress of the resiliently deformable member biases the bearing surface in an engagement direction.
One side of the resiliently deformable member of the bearing may be for attachment to a body of one of the base and the mounting structure, and the bearing surface may comprise a substantially non-deformable material attached to the other side of the resiliently deformable material.
The substantially non-deformable material of the bearing surface may comprise a substantially rigid layer.
The bearing surface may comprise non-elastomer material, optionally at least one of steel, tungsten carbide, cobalt and/or chromium, further optionally tungsten carbide in a cobalt and chromium matrix.
The resiliently deformable member may comprise an elastomer. The elastomer may comprise at least one of rubber, for example natural rubber, neoprene or polypropelene.
The resiliently deformable member may comprise a laminated structure, optionally comprising a plurality of elastomer layers interspersed with at least one non-elastomer layer. The at least one non-elastomer layer may comprise a substantially rigid layer, optionally at least one plate.
The at least one resiliently deformable member may have substantially different elasticity in different directions, optionally the different directions are a radial direction and an axial direction.
In a further independent aspects of the invention there is provided a base or mounting structure comprising at least one bearing as claimed or described herein.
The base or mounting structure may have an engagement axis that is substantially aligned with an engagement axis of a further mounting structure or base when the base or mounting structure is mounted to the further mounting structure or base.
For the or each bearing, the bearing surface may be inclined with respect to the engagement axis. For the or each bearing, the angle between the bearing surface and the engagement axis of one of the mounting structure and the base may be less than the inverse tangent of a coefficient of friction between the bearing surface and a further bearing surface with which the bearing surface engages in operation.
The base or mounting structure may comprise a male portion or a female portion that comprises the bearing or each of the bearings. In the case where the male portion or female portion is a male portion, the bearing surfaces may be disposed circumferentially around the male portion and slope radially inwards.
The bearings may be disposed circumferentially around the female portion and project radially inwards therefrom; or the bearings may be disposed circumferentially around the male portion and project radially outwards therefrom.
The base or mounting structure may further comprise means for applying shear force to the or each deformable member, wherein the means for applying shear force may be operable to apply shear force when the base and the mounting structure are not engaged together.
In a further, independent aspect of the invention there is provided a method of mounting a mounting structure to a base, wherein one of the base and the mounting structure comprises a bearing comprising a resiliently deformable member and having a bearing surface, the other of the base and the mounting structure comprises a further bearing surface for engagement with the bearing surface of the bearing, and the method comprises bringing the base into contact with the mounting structure such that shear stress of the deformable member biases the bearing surface towards the further bearing surface. The shear stress may be in an engagement direction.
The base may be installed on the bed of a body of water.
The method may comprise mounting an energy conversion device, for example a wave energy conversion device, to the mounting structure. The method may comprise allowing a reduction in compression of at least one of the bearings causing a release in shear stress, thereby to move the mounting structure and/or at least one of the bearings towards the base
The method may comprise providing for lateral movement of the mounting structure in alternating directions causes alternating bearing surfaces to move relative to corresponding further bearing surfaces thereby to move the mounting structure and/or the bearings towards the base.
The lateral movement may be caused by action of waves, tides, currents or wind on the mounting structure or on a further structure attached to the mounting structure.
The mounting structure may have an engagement axis, the base may have an engagement axis and the method may comprise moving the base and the mounting structure into contact with the engagement axis of the base and the engagement axis of the mounting structure substantially aligned.
The method may further comprise applying shear force to the or each deformable member prior to bringing the base into contact with the mounting structure.
The method may further comprise releasing the mounting structure from the base by at least one of:—applying force to one of the base and the mounting structure; changing the friction between the at least one bearing surfaces and the at least one further bearing surface, for example by lubricating the at least one bearing surface and/or the at least one further bearing surface; altering the compressive load between the bearing surfaces and the further bearing surfaces; or altering the angle of inclination of at the at least one bearing surface and/or the at least one further bearing surface(s).
The releasing may comprise operating a plurality of jacks to apply force to the base or mounting structure, or providing fluid to the interface between the at least one bearing surface and the at least one further bearing surface.
In further independent aspects of the invention there is provided one or more of a system, a bearing, a base or a mounting structure substantially as herein described with reference to the accompanying drawings.
In another independent aspect of the invention there is provided a method substantially as herein described with reference to the accompanying drawings.
In a further, independent aspect of the invention there is provided a mounting for securing a structure to an underwater foundation comprising a spigot connectable in use to the structure, a socket of the underwater foundation for receiving the spigot, and a bearing for mating the spigot to the socket. The bearing may comprise a resiliently deformable member or resiliently deformable members. The deformable member or resiliently deformable members may be disposed circumferentially about the spigot and may project radially outwardly therefrom. The bearing may be formed and arranged so that when the spigot is inserted into the socket the resiliently deformable member is, or members are, deformed and held in shear stress for example in the axial direction of the mounting.
The bearing may comprise at least two contact surfaces on the resiliently deformable member or members. The contact surfaces may be disposed circumferentially around the spigot and may slope radially inwards in the direction of insertion of the spigot. The contact surfaces may be formed for gripping contact with corresponding sloping contact surfaces provided on the socket when the spigot is inserted.
The at least two contact surfaces on the resiliently deformable member or members may be made of portions of a substantially non deformable material bonded to, or otherwise engaged with, said resiliently deformable member or members.
The portions of a substantially non deformable material may be substantially wedge shaped to provide the sloping radially inwards contact surfaces.
The bearing may comprise a plurality of discrete resiliently deformable members. plurality of discrete resiliently deformable members may be disposed circumferentially about the spigot and may project radially outwardly therefrom.
The resiliently deformable members may comprise an elastomer.
At least one resiliently deformable member may have differing elasticity between the radial direction and the axial direction.
In a further, independent aspect of the invention there is provided a method of securing a structure to an underwater foundation comprising connecting a spigot as described and/or illustrated herein to the structure and mating the spigot to a socket of the underwater foundation using a bearing as described or illustrated herein.
There may also be provided an apparatus or method substantially as described herein with reference to the accompanying drawings.
Any feature in one aspect of the invention may be applied to other aspects of the invention, in any appropriate combination. For example, apparatus features may be applied to method features and vice versa.
Embodiments of the invention are now described, by way of non-limiting example, and are illustrated in the following figures, in which:—
A system 2 for mounting a structure to a base according to a first embodiment is illustrated in
In the embodiment of
In this case, the wave energy converter is a variant of the flap-type wave energy converters described in WO 2006/100436, WO 2009/44161, WO 2010/049708, WO 2010/084305, WO 2011/101102 and WO 2011/073628, each of which is hereby incorporated by reference.
In the embodiment of
It can be seen in this case that the tapered contact pads 10 are arranged circumferentially around, and project radially outwards from, the male portion of the mounting structure and the surfaces of the contact pads 10 slope radially inwards in the direction of insertion of the male portion. The tapered contact pads 12 are disposed circumferentially around the female portion and project radially inwards therefrom.
Each of the contact pads 10 forms part of a respective bearing 14 on the mounting structure 4. The surface of a contact pad 10 provides a bearing surface of the bearing 14. Each bearing 14 comprises a resiliently deformable member in the form of a laminated elastomeric structure 16 that, in this case, comprises an elastomer in the form of natural rubber laminated together with a series of steel plates. Each of the contact pads 10 is wedge shaped and has a tapered bearing surface.
In the embodiment of
The contact pads 12 on the base 6 are of similar structure to the contact pads 10 and again comprise a stainless steel body with a flame-applied coating of tungsten carbide in a cobalt and chromium matrix that provides a bearing surface. The contact pads 12 are also wedge shaped and have a tapered bearing surface.
Each of the mounting structure 4 and the base 6 can be considered to have a respective engagement axis, such that to mount the mounting structure to the base the mounting structure is moved into contact with the base, with the engagement axis of the base and the engagement axis of the mounting structure substantially aligned. In the embodiment of
It is a feature of the embodiment of
The elastomeric bearings are able to shear in a direction parallel to the aligned engagement axes at a relatively low load, and each of the wedged contact pads 10, 12 is free to move independently of the others. The wedged contact pads 10, 12 allow all of the bearing surfaces to be brought into contact, in spite of possible installation misalignments and manufacturing tolerances. The laminated construction of the elastomeric components then provides a stiff load path for the wave energy converter operational loads to be reacted into the base 6 in operation.
The faces of the contact pads 10, 12 are tapered to allow the base 6 and the mounting structure 4 to be brought together in an axial (in this case, vertical) direction. The tapers also allow lateral tolerances to be accommodated through shear in the bearings 14.
For lateral loads to be transferred successfully between the inclined bearing surfaces, the angles of the bearing surfaces are matched with the friction conditions of the surfaces. If the angle between the bearing surface and the vertical exceeds the inverse tangent of the friction coefficient, the bearing surfaces will slip. Therefore, the angles that the bearing surfaces make with the engagement axes is limited to less than the minimum friction angle at the interface, allowing a suitable margin, or offset angle, for safety.
Axial shear deformations are retained in the elastomeric bearings 14 after mating of the support structure 4 and base 6. The purpose of the residual shear deformation is to maintain all bearing surfaces in contact even once large operational loads are applied. Operational loads can cause both the elastomeric bearings 14 and the structures to deform, changing the load distribution on the bearing surfaces. Should an individual bearing 14 become completely unloaded, the restoring force stored by the shear stress in the elastomer causes the tapered bearing surfaces to slide in a direction which helps to maintain the bearing surfaces in contact.
The process whereby contact pads 10, 12 move to close gaps as the system is deformed under load also results in residual compressive pressures between the bearing surfaces once the load causing the deformation is removed. That can have three important consequences. Firstly, before the bearing surfaces can slide during subsequent load cycles it is necessary to overcome this preload. Additional movements are therefore suppressed unless larger forces are experienced than has previously been experienced. After an initial bedding-in period of the mounting structure 4 in contact with the base it is therefore not expected that any significant relative movement between the mounting structure 4 and the base 6 will be seen except under increasingly extreme sea conditions. This avoids continuous movements and so prevents wear on the bearing surfaces.
Secondly, once all of the pads 10, 12 are experiencing compressive load (also referred to as the pads being pre-stressed or pre-loaded) after insertion of the mounting structure 4 into the base 6, they can react to additional loads by an increase or decrease in the compressive pressure. This means that the bearings 14 are able to react to both positive and negative forces, meaning that fatigue loads are distributed between all of the bearings 14.
Thirdly, the preload in the bearings 14 creates friction at the interface between contact pads 10, 12 that needs to be overcome before the wave energy converter can be removed for maintenance. The steeper the angle of the tapers, and the higher the maximum coefficient of friction of the bearing surfaces, the more difficult breaking the connection between the mounting structure and the base becomes.
The movement of the male portion of the mounting unit 4 into engagement with the female portion of the base 6, and the subsequent effects on the bearings 14 of forces experienced by the system are now discussed with reference to
In
In
In
In
In some embodiments the buoyancy of the wave energy converter is then adjusted to its operational value, for example by flooding part of the flap with water, and the winch is disconnected. In some embodiments the wave energy converter has substantially neutral buoyancy in operation.
In
In
It can be understood from
In
It can be understood from
Next, an external lateral force F is applied in the opposite direction towards the left-hand side, as shown in
It can be seen from
Next, the force applied in left-hand direction increases to 2F, as indicated in
In
It can be understood from
Next, an external lateral force ½ F is applied towards the left-hand side, as shown in
In some modes of operation the mounting structure is allowed to embed itself into the mounting and experience lateral forces for a period of time, to enable the bearings to embed themselves further and the compressive load on the bearings to increase and the mounting structure is then secured to the base with other securing devices, for example mounting bolts.
It may be desired subsequently to remove the mounting structure 4 from the base 2, for example for replacement or maintenance. It is a feature of the embodiment of
The expected residual loads will vary with the size of the apparatus and the range of sea conditions that are actually experienced.
The mounting structure 4 may be released to float back to the surface, for example after pumping water out of chambers in the flap or, if necessary, otherwise increasing the buoyancy of the flap or other components connected to the mounting structure 4. However, the mounting structure is prevented from being released from the base 6 by the friction between the bearing surfaces 10a, 12a and 10b, 12b as illustrated schematically in
In order to release the mounting structure it may be necessary to apply much more heave force (for example, 1000s of tonnes), change friction conditions (for example lubricate the bearing surfaces), reduce compressive load at the friction interface or change the taper wedge geometry to allow easy release.
A system according to one embodiment for releasing the mounting structure 4 is illustrated schematically in
A system according to one embodiment for releasing the mounting structure 4 is illustrated schematically in
In the embodiment of
An alternative embodiment is illustrated in
The mounting structure is connected to a wave energy converter comprising a flap 50. The flap 50 is shown floating horizontally on the surface in
A magnified view of the male portion of the base unit, and further magnified views of the top row of bearings 60 and bottom row of bearings 60, are provided in
A further embodiment in which the bearings are mounted on arms of a mounting structure and project sideways is illustrated in
Further embodiments in which the bearings are mounted on the base, in this case a foundation, rather than the mounting structure are illustrated schematically in
A further alternative embodiment is shown in
Similarly to the embodiment of
A magnified view of the male portion of the base unit, and further magnified views of the top row of bearings 110 and bottom row of bearings 110, are provided in
A magnified view of the base unit 104 is shown in
d show the relative positions of the base unit 104 and the wave energy convertor (WEC) apparatus that includes the flap 100 and mounting structure 102. The flap 100 includes upper ballast compartments and ballast compartments near a hinge connection to the mounting structure 102.
At the first stage (
At the next stage (
At the next stage (
During the installation procedure of the embodiment of
At the next stage, the flap 100 is ballasted into operational condition by pumping water out of the upper compartments to increase pitch stiffness and pumping water into the hinge compartments chambers to decrease buoyancy. Any ballast installation equipment is then recovered.
A control and instrumentation umbilical is then connected, and the main WEC hydraulics are also connected together, and local pressure tests of hydraulic connections are conducted. The mooring and pull down equipment, and installation tools are then recovered. For example, as indicated in
With reference to
The WEC is then connected to moorings and subsequently returned to its temporary stability condition. The pre-shear cylinders can be reconnected and used to apply force to release the elastomeric pads, the ball grabs can be used to provide temporary stability, and an ROV torque tool can be used to release the clamp of the heave connection. A backup release mechanism is provided by the pin 126, and rigging can be attached and used to release the pin if necessary, in case the clamp fails.
Next, the ball grabs are released using a remote hydraulic release provided at a support vessel. The WEC then resurfaces. Tow lines are then connected, the moorings are disconnected and the WEC can be towed to shore by the support vessel.
In alternative embodiments, different materials may be used for the bearings and the bearing surfaces. The particular materials used can be selected to provide a desired friction, compressive stiffness and shear stiffness characteristics. For example, in some embodiments the elastomer used in the deformable member may comprise, for example, neoprene, polypropylene or any other suitable elastomer material. The deformable member may also include substantially rigid material, for example the steel plates as already described. However any other suitable substantially rigid and/or substantially non-deformable material may be used and may be bonded to the elastomer.
The angles of the tapered bearing surfaces can vary in different embodiments. In the embodiment of
The ratio of elastomer stiffness under compressive and shear loading of the elastomeric pads can be high, for example in the region of 1000 to 1 in some embodiments. The ratio is different in different embodiments. The loads experienced by the elastomeric structure or other resiliently deformable member are application dependent.
In embodiments, axial shear deformations of individual, compliant bearings, when combined with tapered contact surfaces, allow for multiple bearing surfaces to be brought into contact in spite of installation misalignments and manufacturing tolerances. This can allow for increased load sharing between multiple bearings.
If residual axial shear deformations are generated in compliant bearings during mating of the structure and foundation, all bearing surfaces can be maintained in contact even after loads are applied to the structure and cause it to deform. This occurs without any external intervention because if an individual bearing becomes unloaded, the restoring force from the pre-sheared compliant bearing causes sliding of the tapered contact surfaces to maintain contact. This sliding only happens during an initial “bedding-in” phase and after this there should be no relative motion between bearing surfaces. That can reduce wear.
The action described in the preceding paragraph pre-loads the connection so that reversing structural loads are resisted via fluctuating compressive pressures on all bearings, further distributing the loads.
Embodiments of the invention may be used to mount structures such as wave power devices (for example, wave energy convertors—WECs) but may also be used to install any structure requiring secure fixing to an offshore location. Suitable structures may include, for example, tidal energy devices, water current devices, wind turbine masts or other masts, oil or gas production or exploration-related structures, or structures relating to telecommunication installations. Embodiments of the invention may also be used on land.
Resiliently deformable (for example elastomer) parts of a bearing may assist in firmly and correctly locating a spigot in a socket and shearing stress (or other stored energy) acts to close gaps caused by larger lateral forces moving the spigot sideways. The spigot continuously “reseals” itself firmly in the socket in response to both small and large forces because of both the stored energy and the resilient compressibility of the resiliently deformable members.
Although the base of the embodiment of
In many circumstances the bearing is able to cope well with heave forces arising from action of waves, tides or currents, and is able to resist such heave forces effectively.
Use of the bearing in some embodiments may eliminate or reduce the use of concrete or other grouting material in the installation of a device at the bed of a body of water.
The mounting is expected to be secure and may require dedicated techniques to remove it.
The term shear stress as used herein is intended to encompass the term shear tension.
It will be understood that the present invention has been described above purely by way of example, and modifications of detail can be made within the scope of the invention.
Each feature disclosed in the description, and (where appropriate) the claims and drawings may be provided independently or in any appropriate combination.
Number | Date | Country | Kind |
---|---|---|---|
1210882.5 | Jun 2012 | GB | national |
1214962.1 | Aug 2012 | GB | national |
Filing Document | Filing Date | Country | Kind |
---|---|---|---|
PCT/GB2013/051629 | 6/20/2013 | WO | 00 |