NL2014952B1

NL2014952B1 - Method for installing an elongated member or an assembly thereof.

Info

Publication number: NL2014952B1
Application number: NL2014952A
Authority: NL
Inventors: Angelov Zdravko
Original assignee: Vizionz Holding B V
Priority date: 2015-06-10
Filing date: 2015-06-10
Publication date: 2017-02-13
Also published as: EP3307956B1; WO2016200261A1; DK3307956T3; EP3307956A1; NL2014952A

Abstract

The present invention is directed to a method for installing an elongated member or an assembly thereof, comprising the steps of: - providing an elongated member that comprises a peripheral wall and an inner space that extends in the longitudinal direction of said elongated member; - arranging said elongated member into or on a soil; - arranging a floatable member inside the inner space of said elongated member or assembly; - displacing said floatable member by providing and/or regulating liquid inside the inner space of the elongated member or assembly; and - bringing said floatable member in an engaged state with the elongated member or assembly when the liquid level inside said inner space has displaced said floatable member to a desired level.

Description

Method for installing an elongated member or an assembly thereof

The present invention is directed to a method for installing an elongated member or an assembly thereof. More specifically, it is directed to method for installing a monopile for e.g. a wind turbine. The assembly may be an assembly of such a monopile and a so-called transition piece.

In offshore wind, but also in onshore wind and oil and gas, large tubular members are used as a foundation for the support of the wind turbine or the top side of the structure. Typically one or more elongated steel members are used as direct support in the soil (e.g. a monopile) on which the remainder of the structure is positioned. Because of the large structures this foundation has to support (such as wind turbines or oil rigs), the steel members tend to become very large and heavy themselves in order to possess sufficient strength for the loads they have to resist. In addition, these support members are also subject to complex dynamic loads during operation i.e. multiple excitation frequencies caused by the wind, waves and currents that all occur simultaneously and are also changing in time, leading to increased fatigue of the steel members and a reduced lifetime.

As a consequence of their heavy weight and deteriorating steel strength over time, the foundation structures require, in the first place, large equipment for lifting and aligning during installation and, in addition, often additional strengthening at some point during their lifetime. It is thus desirable that the weight of the foundation and complexity of its installation are reduced to a minimum. A possible approach is to reduced the load and to reduce the need for equipment required during the initial installation and during any later strengthening.

In order to deal with the problem of installation and load reduction several approaches are developed. Up to now the classical approach is to use lifting cranes mounted on an offshore installation vessel to lift and position a steel foundation into place. The main drawback of this approach is that the equipment required gets increasingly heavy with the increasing size of turbines and foundations nowadays, and thus becomes too cumbersome and also very expensive. Moreover, the lifting and positioning operation gets very laborious and time-consuming, also further increases the cost of installation. A first measure for reducing the need for heavy lifting equipment is to split the foundation into two pieces - a primary elongated member (i.e. a monopile) driven into the ground first and a secondary structural element (i.e. a transition piece) separately positioned on top of the primary elongated member. In this way, the weight of the structure is distributed over the two pieces, e.g. the monopile and the transition piece, which are easier to lift separately. The main drawback of this design is that it introduces the need for an additional load bearing connection between the primary elongated member and the secondary structural element. This connection needs to be able to sustain the same heavy loads as the elements it connects and needs to be established in the more difficult conditions at sea. Currently, two main alternative designs are in use for establishing this load bearing connection: a flange and a grouted connection. For a flange, the opposite ends of the primary and secondary elements end in flanges which are bolted to each other. For a grouted connection, the ends of the primary and secondary elements are positioned such that they overlap over a length of several meters and grout (a type of concrete) is poured between them. As the grout sets and hardens, it establishes a long term connection between the two elements.

Currently, the grouted connection is preferred as it provides a flexible connection for a limited period of time during installation. The time the grout needs to set into a solid state allows for possible adjustments of the vertical alignment of the secondary element in the cases where the primary member is tilted too much after being driven in the ground. Being able to correct such a vertical misalignment is desirable as the wind turbine placed on top has very low tolerances for vertical misalignment (typically 1-2 degrees). With this however, the grouted connection introduces complications from the need for positioning. The adjustment of that position may be done for example with a crane or hydro cylinders, but that adds to the complexity and installation time. In addition, a grouted connection has the disadvantage that it doesn’t hold for a very long time when subjected to the complex dynamic loads typical for the offshore environment. It tends to disintegrate and let loose after years of operation, allowing the secondary structural element and turbine on top to tilt in the process.

An object of the present invention is to provide an installing method that is improved relative to the prior art and wherein at least one of the above stated problems is obviated.

Said object is achieved with the method for installing an elongated member or an assembly thereof according to the present invention, comprising the steps of: - providing an elongated member that comprises a peripheral wall and an inner space that extends in the longitudinal direction of said elongated member; - arranging said elongated member into or on a soil; - arranging a floatable member inside the inner space of said elongated member or assembly; - displacing said floatable member by providing and/or regulating liquid inside the inner space of the elongated member or assembly; and - bringing said floatable member in an engaged state with the elongated member or assembly when the liquid level inside said inner space has displaced said floatable member to a desired level.

Offshore, an elongate member is typically arranged into the soil, i.e. a monopile is driven into the soil. The invention also extends to elongate members that are arranged indirectly, e.g. via a support or foundation, on a soil. The soil or support or foundation seal the elongate member at its lower side, and the peripheral wall of the elongate member or assembly provides an inner space wherein a floatable member may be raised or lowered when liquid is brought into or taken out of said inner space. The floatable member is preferably floatable itself, but may also be made floatable via a floatable support body. It is to be noted that an already sealing floatable support member may trap a gas supply between the liquid level and the floatable member itself, resulting in the floatable member to be indirectly displaced when the liquid level is adapted. Especially offshore, water is readily available, and therefore the proposed method provides an installing method that is significantly simplified compared to the prior art installation methods described above (using for example heavy lifting equipment or welding).

According to a preferred embodiment, said floatable member is arranged on said elongate member or assembly. This allows said floatable member to be simultaneously placeable with said elongate member or assembly, reducing the number of hoisting steps required. This saves time and reduces the burden on expensive and energy-consuming machinery.

Although the elongate member may be filled using a pump, natural water pressure may be used for at least partially filling said inner space if, according to a further preferred embodiment, the method comprises the steps of: - installing said elongated member in a water body; - arranging at least one through hole in said peripheral wall of said elongated member, wherein said through hole is arranged at a level between the soil and the water level of said water body; - filling said inner space with water that is allowed to flow via the through hole into the inner space when the water level of said water body is higher than the water level inside said inner space; and - preventing water to flow back from the inner space through the through hole to outside the elongated member. Although a pump may be provided, this arrangement allows for easy and automatic filling via a pressure difference caused by a water level difference.

It is even more preferred if the water body is a tidal water body. Therefore, the method preferably comprises the step of installing said elongated member in a tidal water body. The tidal range may be used for at least partially filling said inner space if the floatable member is arranged at a level lower than high tide.

According to a further preferred embodiment, said through hole is arranged below the low tide water level of said tidal water body. This arrangement allows the use of the entire tidal range in displacing the floatable member. Even at low tide the through hole remains submerged and able to exchange fluid between the inner space of the elongated member and the tidal water body.

According to a further preferred embodiment, said through hole is provided with a valve configured for preventing water to flow from the inner space via the through hole to outside the elongated member. Preferably, this is a one-way valve or sealable valve.

According to an even more preferred embodiment, said floatable member is a sealing member. After the last installing step of bringing said floatable member in an engaged state with the elongated member or assembly when the liquid level inside said inner space has displaced said floatable member to a desired level, a sealing member will provide a substantially fluid tight confined space that may be pressurized. Pressurization of said confined space may provide additional advantages, such a pre-stressing the elongate member to increase its strength.

According to a further preferred embodiment, said sealing member is configured to provide a fluid tight seal in said inner space, preventing water flowing back via the through hole out of the inner space into the water body.

According to a further preferred embodiment, said method comprises the step of bringing said sealing member in a substantially fluid tight sealing state when the fluid level inside said inner space is at a desired level. It is noted again that there may be a compressed gas bubble between the liquid level and the sealing member, which generates an additional buoyancy force that can also easily be regulated.

In order to prevent air between the sealing member and the water level inside the elongated member, the sealing member is according to a further preferred embodiment brought in a substantially fluid tight sealing state when the water level is substantially at or above the seal position.

According to a further preferred embodiment, said method comprises the step of filling the inner space of said elongate member with liquid to at least a level substantially at or near the low tide water level of said tidal water body. In this context, a level substantially ‘at or near the low tide water level of said tidal water body’ is to be understood as anywhere in the range ±15% of the low tide water level. The advantage thereof is self-pressurization throughout the tidal cycle with a maximum at high-tide.

According to a further preferred embodiment, said method comprises the step of filling the inner space of said elongate member with liquid to a level substantially between the low tide and high tide water level of said tidal water body, more preferably wherein the inner space is filled to a level in the range of 25%-75% of the range between low and high tide water level of said tidal water body. This configuration provides a combination of the benefits of the cases at a low- tide level and at high-tide level in the ratio of the chosen position in comparison to the high-tide/low-tide levels. Thus, during low-tide the structure benefits from the added mass of the water and during high-tide the structure benefits from the created pre-stress in the elongated member.

The level of the liquid is chosen based on the desired ratio of the corresponding benefits.

According to a further preferred embodiment, said method comprises the step of filling the inner space of said elongate member with liquid to at least a level substantially at or near the high tide water level of said tidal water body. In this context, a level substantially ‘at or near the high tide water level of said tidal water body’ is to be understood anywhere in the range ±15% of the high tide water level. This adds the significant mass of the liquid that is enclosed inside throughout the tidal cycle with a maximum at low-tide, thus, acting as a mass damper in the system and reducing the loads.

If, according to a further preferred embodiment, said floatable member is a support member, it may be used to support members of the assembly. It may e.g. support a transition piece on a monopile, wherein said monopile forms the elongate member. In this way, a reduction of the load on the elongated member is achieved due to a part of the load being transferred directly from the supported member of the assembly to the floatable member and into the enclosed liquid instead of the walls of the elongated member. This has the advantage that the dimensions and mass of the elongated member may be reduced. This configuration would, in principle, also allow for the floatable member to be used for its carrying capacity due to its buoyancy for also lifting personnel working on site or materials used during the operation or repair of the installation.

According to a still further preferred embodiment, the elongate member or assembly and the support member comprise a mating tapered shape. The tapered engagement of the elongate member or assembly and the support member allows the support member to provide both support and sealing. The tapered engagement furthermore provides a self-tightening connection when pressurized from within the confined space. It is also advantageous that no welding is required to establish the connection of the support member to the elongated member.

According to a further preferred embodiment, an intermediate bridging member is arranged between the sealing member and the elongate member or assembly before the sealing member has reached its sealing state. This allows the diameter of the floatable element to be smaller than the diameter of a flange in the elongated member or assembly. In this way, the floatable member may be lowered by hoisting into the elongate member or assembly, passing downwards past the flange. After the intermediate bridging member is arranged on the (flange of the) elongate member, the floatable member is moved upwards and creates a sealing engagement with the intermediate bridging member that is now arranged between the elongate member or assembly and the floatable member.

According to a further preferred embodiment, a spreader member is provided, and wherein the support member and the spreader member comprise mating tapered surfaces which are engageable such that a radial force may be exerted on the support member via shear displacement of said mating tapered surfaces. This method achieves an engaged state of the floatable member without the need for welding on the inner wall of the elongated member or the need to maintain a liquid pressure underneath the floatable member after the installation has been completed.

Arranging the sealing member at a desired height is facilitated if, according to a further preferred embodiment, the floatable member is arrangeable on a support provided inside the elongated member. This method enables an engaged state of the floatable member without supporting on the elongated member or the need to maintain an elevated level of the liquid inside the elongated member after the installation has been completed. The support provides the ability to support the floatable member at a level substantially higher than the liquid level inside the elongated member through its elongated shape, i.e. it elevates the floatable member up while still itself being submerged in the liquid.

This also provides the additional safety advantage as the buoyancy force does not disappear even in the exceptional case where the pressurization means or sealing may fail in case of an emergency for example.

The use of a separate support also enables the production of the support from a separate and cheaper material than the floatable member itself, which is a practical benefit when the elevation distance is large.

According to a further preferred embodiment, said assembly comprises a monopile and a transition piece, and wherein said floatable member is arranged between the monopile and the transition piece such that it provides a force transferring member between the monopile and the transition piece. The floatable member is locked into place between the supported member, typically a transition piece, and the top of the elongated member, thereby providing continuous support. This reduces the dynamic load on the conventional connection between the monopile and transition piece (i.e. grout) and thus increasing its lifetime.

According to a further preferred embodiment, said method further comprises the step of removing or adding air between the sealing member and the water level inside said inner space of said elongated member via a valve or pump that is in fluid connection with the space directly under the sealing member.

According to an alternative embodiment of the method of the invention, the initial positioning of the floatable member is done by letting it float over the top edge of the elongated member during high-tide. For this purpose, the floatable member is initially placed to float on the outside fluid next to the elongated member driven into the soil. In this position it may be connected to the elongated member, said connection functioning as an anchor that prevents the floatable member of floating away. Once the level of the outside liquid increases to the high-tide and is sufficiently high above the edge of the elongated member, the floatable member is floated over the edge to the inside of the elongated member awaiting the low-tide and the positioning of the secondary structural element on top for the remainder of the installation procedure. The crossing over by the floatable member from the outside liquid to the inside liquid can be done manually or automatically by pulling the floatable member to the inside by the anchoring connection (either controlled by an operator or in a preprogrammed way). In this way the need for a crane for lowering and positioning is completely eliminated.

In a further embodiment of the invention the primary elongated member does not need to be driven into the soil before the pressurization means are used for lifting.

In the following description preferred embodiments of the present invention are further elucidated with reference to the drawing, in which:

Figure 1 is a schematic cross sectional view of the floating member according to a first embodiment;

Figure 2.1 shows a top view of a first embodiment for arranging the floating member inside the elongated member;

Figure 2.2 shows a top view an alternative embodiment for arranging the floating member inside the elongated member;

Figure 3.1 is a schematic cross sectional view of a first embodiment of the lowering step of the floatable member, wherein the floatable member is positioned separately from and after the elongated member;

Figure 3.2 is a schematic cross sectional view of an alternative embodiment of the lowering step of the floatable member, wherein the floatable member is positioned as one package with the elongated member;

Figure 3.3 is a schematic cross sectional view of a still further alternative embodiment of the lowering step of the floatable member, wherein the floatable member is positioned as one package with a secondary structural element;

Figure 4.1 is a schematic cross sectional view of a first embodiment of the floatable member in the floating position after lowering it in the elongated member, where the floatable member keeps floating due to its vessel shape;

Figures 4.2 and 4.3 show the step of adjusting the position of the floatable member from Figure 3.1 within the elongated member in upward and downward direction respectively with the use of a pump;

Figure 5.1 is a schematic cross sectional view of an alternative embodiment of the floatable member in the floating position after lowering it in the elongated member, where the floatable member keeps floating due to an entrapped second fluid (air);

Figure 5.2 shows the step of adjusting the position of the floatable member from Figure 3.2 within the elongated member in upward direction by the use of a pump;

Figure 6 is a schematic cross sectional view of an embodiment for arranging the floatable member as a support member for a secondary structural element;

Figure 7.1 and 7.2 show a schematic cross sectional view of the steps for arranging an alternative embodiment of the floatable member under a secondary structural element;

Figure 8 shows a schematic cross sectional view of a still further alternative embodiment of the floatable member for positioning at a greater height than the liquid level inside the elongated member;

Figure 9 shows three successive steps (a, b and c) of positioning the floatable member upward using the change in water level during tide, without any pump;

Figure 10 shows three successive steps (a, b and c) of positioning the floatable member downward using the tide, without any pump;

Figure 11 is a detailed cross sectional view of the sealing of the floatable member as a sealing member in the engaged state to the elongated member;

Figure 12.1 shows a detailed cross sectional view of an alternative sealing step of the floatable member to the elongated member, wherein several separate seals are positioned;

Figure 12.2 shows a detailed cross sectional view of a still alternative embodiment for the sealing step of the floatable member to the elongated member through a seal with a circular cross-section;

Figure 12.3 shows a detailed cross sectional view of an a still further alternative sealing step of the floatable member to the elongated member, wherein several separate seals with a circular cross section are positioned in order;

Figure 13a shows a schematic top view of the sealing step with modular seals, wherein a fluid tight connection of the floatable member is not required;

Figure 13b shows a side view of the floatable member embodiment from Figure 13a;

Figure 14.1a and 14.1b show a schematic top plane view and a cross sectional view respectively of the sealing step with modular seals that extend;

Figure 14.2 shows a schematic cross sectional view of an alternative embodiment for the modular extending seals of Figure 14.1;

Figure 15.1 shows a schematic cross sectional view of two alternative (a and b) embodiment of the floatable member for changing the lifting force at the time of design;

Figure 15.2 shows a schematic cross sectional view of two alternative (a and b) embodiments of the support for changing the lifting force on the floatable member at the time of design;

Figure 16.1 shows a schematic cross sectional view of two consecutive (a and b) states of adjusting the lifting force on the floatable member during operation through a pump;

Figure 16.2 shows a schematic cross sectional view of two consecutive (a and b) states of adjusting the lifting force on the floatable member and supporting a secondary structural member during operation through a pump;

Figure 17 shows a schematic cross sectional view of two consecutive (a and b) states of adjusting the lifting force on the floatable member during operation through a mechanical means;

Figure 18 is a schematic cross sectional view of the engaged state of the floatable member on top of the edge of the elongated member;

Figure 19 is a detailed cross sectional view of the floatable member with a merged seal;

Figure 20 is a schematic cross sectional view of the engagement step of the floatable member on top of the edge of the elongated member using a spreader;

Figure 21 is a schematic cross sectional view of the engagement step of the floatable member on top of the edge of the elongated member using a smaller spreader;

Figure 22 is a schematic cross sectional view of the engagement step of the floatable member on top of the edge of the elongated member using a floating support;

The cross sectional view of Figure 1 shows schematically a first embodiment of the installation method subject of the invention with a corresponding top view in Figure 2.1. According to this first embodiment, Figure 1 shows an elongated member 1 comprising a flange 2 arranged on the inside where the elongated member 1 is driven into a soil 10 and is in contact with a liquid 6 supporting a floatable member 3.

The elongated member 1 is in contact with the liquid 6, wherein the inner space of the elongated member 1 is filled with an inside liquid 610 to a certain initial liquid level inside 600 and the outside of the elongated member 1 is surrounded by an outside liquid 620. On the surface of the inside liquid 610 is positioned the floatable member 3 comprising a sloped edge 310 in its circumference, giving it a tapered shape, and a bottom wall 320 in contact with the inside liquid 610. The sloped edge 310 and the bottom wall 320 are able to be one unit or the sloped edge 310 and the bottom wall 320 are able to be two units attached to each other e.g. bolted.

According to a first embodiment of the invention, the floatable member 3 and its sloped edge 310 are substantially circular, but can also follow the inner shape of the elongated member 1 for as far as it deviates from a circular shape. The floatable member 3 is engineered such that it has enough buoyancy to float on the surface of the inside liquid 610 on its own. This floatability may be obtained by giving it a specific shape that ensures sufficient liquid displacement, by being manufactured from a material that has a lower specific weight than the inside liquid 610 the floatable member 3 is placed in or by using any other method that achieves the same result of the member 3 being able to float. According to this first embodiment, the floatable member 3 is intended to support at the least its own weight in the liquid 610, but it can also be used to support the weight of additional equipment or personnel on top of it and in this way be used as a platform, either during installation or at a later stage during maintenance works.

The floatable member 3 is connected via a fluid connection 27 to a pressurization means 5, for example a pump. The pressurization means 5 further comprises a feed line 9, able to feed fluid in or out, and a controller 99 and control line 98. The controller 99 provides a means of controlling the operation of the pressurization means 5 by sending control signals through the control line 98. It can be pre-programmed to do so, directly operated by installation personnel on site, operated remotely or configured to use input from the environment such as GPS coordinates, elevation information, (water)pressure, etc. This enables the automation of the complete installation process - including positioning, timing of steps, regulation of the created forces and engagement and disengagement - and reduces the need for personnel on site.

In this first embodiment the position shown in Figure 1 forms the starting position of the installation method after placing the floatable member 3 and before the floatable member is brought into an engaged state. Subsequently, the pressurization means 5 is used to adjust the level of the liquid 610 inside the elongated member 1 by pumping the outside liquid 620 from/to the outside through the feed line 9 to/from the inside liquid 610 through the fluid connection 27. Since the outside liquid 620 and the inside liquid 610 are separated by the soil 10 and the walls of the elongated member 1 this changes the level of the inside liquid 610 and in this way changes the vertical position of the floatable member 3 in the direction of the arrows. Although in this embodiment the elongated member 1 is surrounded by the outside liquid 620, it is also possible to apply the method without it by supplying liquid from a different source such as tank or adjusting the vertical position of the floatable member in different ways described in the alternative embodiments.

The flange 2, arranged on the inside of the elongated member 1, comprises a bottom contact surface 210 and an attachment surface 220. The bottom contact surface 210 faces the sloped edge 310 and has a substantially similar tapered shape. The attachment surface 220 connects the flange 2 to the inner wall of the elongated member 1 enabling the flange 2 and the elongated member 1 to be either one unit or two units attached e.g. bolted to each other.

On the sloped edge 310 is arranged an intermediate bridging member 4 which is comparatively flexible, able to absorb deformation and substantially follows the shape of the sloped edge 310 and bottom contact surface 210. At the desired level in vertical direction of the floatable member 3, the sloped edge 310 comes into contact with the bottom contact surface 210 of the flange 2 through the intermediate bridging member 4, bringing the floatable member 3 in an engaged state. The sloped edge 310 in combination with the shape of the bottom contact surface 210 provide a connection that does not require welding and gets tighter when the buoyancy force of the floatable member 3 is increased. Thus, the installation may be executed with limited to no use of a crane and no welding.

Figure 2.1 shows the sectional top view along the line A-A of Figure 1. In accordance with the first preferred embodiment, the flange 2 is shown attached to the inside wall of the elongated member 1 with a substantially circular cross section. Segments of the flange 2 are cut out in order to show the inside liquid 610 beneath it, filling the elongated member 1. The floatable member 3 is positioned on the surface of the inside liquid 610, said floatable member 3 comprising the sloped edge 310, giving it a tapered shape, and the pressurization means 5 with the connected feed line 9. The position of the pressurization means 5 may be either in the center of the floatable member 3 for an optimal balance of the center of gravity or off-center to free up space for other equipment or the free movement of personnel on the surface of the floatable member 3.

The inner diameter D of the flange 2 is shown to be larger than the outer diameter d of the floatable member 3 enabling the floatable member 3 to pass through the gap when lowered inside the elongated member 1 without touching the flange 2.

After the floatable member 3 is positioned below the flange 2, either the continuous member 401 or the segmented member 402 is positioned on top of the sloped edge 310 and below the bottom contact surface 210. The members 401 and 402 are dimensioned such that they cover the sloped edge 310 on the one side and fit underneath the bottom contact surface 210 on the other, in this way locking the floatable member 3 when lifted up by the inside liquid 610. To evenly distribute the load, several segments of the segmented member 402 are used which are preferably arranged around the perimeter of the floatable member 3. The segments of the segmented member 402 may be positioned in contact next to each other preventing any liquid flow or may have a space gap between them, providing only the contact between the sloped edge 310 and the bottom contact surface 210.

Figure 2.2 shows an alternative design of the sectional top view along the line A-A from Figure 1 wherein the members 401 or 402 are redundant. Similar to the first preferred embodiment of Figure 2.1, the flange 2 is again attached to the inside wall of the elongated member 1 which is filled with the inside liquid 610 supporting the floatable member 3. The floatable member 3 of Figure 2.2 is identical to the floatable member 3 of Figure 2.1 with the single difference that its outer diameter d is greater than the inner diameter D of the flange 2. This makes the members 401 and 402 obsolete, but requires the flange 2 to be connected to the elongated member 1 only after the floatable member 3 has been positioned in the elongated member 1 below the flange 2.

Figures 3.1, 3.2 and 3.3 show three alternative embodiments of the lowering step according to the invention of the floatable member 3 inside the elongated member 1. Prior to this step, the elongated member 1 comprising the flange 2 has been lowered into the liquid 6 and the inside liquid 610 fills the elongated member 1 up to a certain level. At this step the elongated member 1 is either already driven into the soil 10 or the elongated member 1 is not yet driven into the soil 10, depending on what is the most efficient method.

According to the first preferred embodiment shown in Figure 3.1, the floatable member 3 is not connected to the elongated member 1 at the lowering step, but is lowered with a separate lifting means 7 inside the elongated member 1. From Figure 3.1 it can be clearly seen that the elongated member 1 is not yet driven into the soil 10 when the lowering operation is performed. In this embodiment, the floatable member 3 has such dimensions that its outer diameter d does not exceed the inner diameter D of the flange 2, enabling it in this way to pass through the gap to a level below the flange in the direction indicated by the arrow.

Figure 3.2 shows an alternative execution of the lowering step, wherein the floatable member 3 is connected to the elongated member 1 via a fastening means 8 with pivot connections 88 at both ends. Together, the elongated member 1 and the floatable member 3 are lowered in the direction of the arrow into the liquid 6 with the common lifting means 7. Executing this step in such a manner provides the benefit of eliminating a dedicated lifting means 7 for the floatable member 3. In addition, in comparison to the embodiment from Figure 3.1, this eliminates the restriction on the outer diameter of the floatable member 3 relative to the inner diameter of the flange 2.

Figure 3.3 shows a schematic cross sectional view of a further embodiment of the lowering step of the floatable member 3, wherein the floatable member 3 is positioned as one package with a secondary structural element 1000. The floatable member 3 is fastened to the secondary structural element 1000 through the fastening means 8 with pivot connections 88 at both ends. Together, the secondary structural element 1000 and the floatable member 3 are lowered in the direction of the arrow on top of the elongated member 1 with the common lifting means 7. The elongated member 1 is at this point already positioned in the liquid 6 and filled with the inside liquid 610 to a certain level. After being lowered, the secondary structural element 1000 is on its turn connected to the elongated member 1 through the load bearing connection 22 (e.g. grout) forming an assembly 2000 comprising the elongated member 1 and the secondary structural element 1000.

Figures 4.1, 4.2 and 4.3 show the step of bringing the floatable member 3 from its initial position after being lowered in the elongated member 1 to an engaged state according the first embodiment of the invention. This execution is preferred in cases where the end-position of the floatable member 3 and the inside liquid 610 are desired to be at a different level in their end state compared to their initial state.

Figure 4.1 shows a schematic cross sectional view of the initial state of the elongated member 1 driven into the soil 10 and filled with the inside liquid 610 to an initial liquid level inside 600. In this step, the initial liquid level inside 600 is approximately equal to the level of the outside liquid 620. The elongated member 1 comprises two alternative installation levels for the floatable member 3, i.e. at a position above the initial liquid level inside 600 connected to an upper flange 201 or positioned below the initial liquid level inside 600 connected to a lower flange 202.

At the initial liquid level inside 600 is positioned the floatable member 3 which is supported by the inside liquid 610 through the bottom wall 320. For this purpose, the floatable member 3 has a preferred embodiment that enables it to freely float on such a liquid. The floatable member 3 further comprises the sloped edge 310 and is connected to the pressurization means 5 through the fluid connection 27. In preparation of the following steps, the pressurization means 5 is also connected to the feed line 9.

Figure 4.2 shows a schematic cross sectional view of the engaged state of the floatable member 3 at a first alternative position that is higher than the initial state of Figure 4.1. In Figure 4.2, first, the outer diameter of the floatable member 3 is increased in a dedicated, separate step after the moment of lowering in accordance with the first preferred embodiment by placing the intermediate bridging member 4 on the sloped edge 310. Then, the position of the floatable member 3 is adjusted in the upward direction of the arrow by pumping liquid from outside the elongated member 1 through the pump feed line 9, the pressurization means 5 and the fluid connection 27 to the inside liquid 610. This increases the initial liquid level inside 600 of the inside liquid 610 enclosed by the elongated member 1 and the soil 10 to a higher liquid level inside 601 that is above the initial liquid level inside 600.

The higher liquid level inside 601 is reached when the floatable member 3 reaches the level of the upper flange 201. The contact between the floatable member 3 and the upper flange 201 is established through an intermediate bridging member 4 and the bottom contact surface 210.

This step is completed by further increasing the volume of the inside liquid 610 until the floatable member 3 is sufficiently pressed against the upper flange 201 by the buoyancy force and is unable to move upwards anymore, as shown in Figure 4.2, reaching an engaged state.

In case of the present embodiment of the invention, the floatable member 3 also enables a fluid tight closing of the elongated member 1 and pressurization of the inside liquid 610 in the engaged state of the floatable member through the sloped edge 310. The slope of the edge 310 approximates the slope of the bottom contact surface 210 of the upper flange 201. In case the intermediate bridging member 4 is fluid tight the pressurization means 5 can be removed after installation.

Figure 4.3 shows a schematic cross sectional view of the engaged state of the floatable member 3 at a second alternative position that is below the initial state of Figure 4.1. In Figure 4.3 the position of the floatable member 3 is adjusted in the downward direction of the arrow by pumping the inside liquid 610 to the outside through the fluid connection 27, the pressurization means 5 and the pump feed line 9. This decreases the initial liquid level inside 600 of the inside liquid 610 enclosed by the elongated member 1 and the soil 10 to a lower liquid level inside 602 that is below the initial liquid level inside 600.

In accordance with the first preferred embodiment of the invention, the inside liquid 610 is pumped out until the floatable member passes through the gap of the lower flange 202. Next the outer diameter of the floatable member 3 is increased in a dedicated, separate step by placing the intermediate bridging member 4 on the sloped edge 310 and the inside liquid 610 is pumped back in the elongated member 1.

The lower liquid level inside 602 is reached when the floatable member 3 reaches the level of the lower flange 202. The contact between the floatable member 3 and the lower flange 202 is established through the intermediate bridging member 4 and the bottom contact surface 210. This step is completed by further increasing the volume of the inside liquid 610 until the floatable member 3 is sufficiently pressed against the lower flange 202 by the buoyancy force and is unable to move upwards anymore, as shown in Figure 4.3, reaching an engaged state. According to this embodiment, even if the intermediate bridging member 4 is not fluid tight, the pressurization means 5 can still be removed after installation.

Both embodiments of Figure 4.2 and 4.3 enable pressurization in the engaged state (in case the intermediate bridging member 4 is fluid-tight) and load reduction from the water column.

Figures 5.1 and 5.2 show a second preferred embodiment of the floatable member 3 for bringing it from its initial position, after being lowered in the elongated member 1, to an engaged state at a different level in vertical direction. This repositioning is shown for the situation wherein the engaged state is at a level higher than the initial position of the floatable member 3, but it applies equally for a level that is below the initial position.

Figure 5.1 shows a schematic cross sectional view of the initial state of the elongated member 1 again driven into the soil 10 and filled with the inside liquid 610 to the initial liquid level inside 600. In this step, the walls of the elongated member 1 and the soil 10 separate the inside liquid 610 from the outside liquid 620 wherein the initial liquid level inside 600 is approximately equal to the level of the outside liquid 620. The flange 2 is again attached to the elongated member 1, comprising the bottom contact surface 210, facing the inside liquid 610, and the attachment surface 220 through which it is attached to the inside wall of the elongated member 1.

According to the current embodiment, the floatable member 3 is again positioned inside the elongated member 1 and supported by the inside liquid 610. However, in this preferred embodiment, the floatable member 3 has a bell-like shape that enables it to float by entrapping a volume of a second fluid 12 (e.g. air) and in this way providing buoyancy. The floatable member 3 comprises the bottom wall 320 in the middle, the sloped edge 310 in the circumference and in addition a side wall 330 extending from it downwards and around the second fluid 12. In this floating state, the second fluid 12 displaces the inside liquid 610 below the floatable member 3 from the initial liquid level inside 600 downwards to an initial floatable member liquid level 603 that is proportional to the weight of the floatable member 3. The sloped edge 310 again has a slope approximating the slope of the bottom contact surface 210 of the flanges 2.

In case of the present embodiment of the invention, the pressurization means 5 with a connected feed line 9 is again attached to the floatable member 3, but in this case through a vertical support 28. In this way, the fluid connection 27 is not directly connected to the floatable member 3, allowing the liquid from the pressurization means to flow down the sloped edge 310 and into the inside liquid 610.

Figure 5.2 shows a schematic cross sectional view of the engaged state of the floatable member 3 at the level of the flange 2, a position that is higher than the initial state of Figure 5.1. Figure 5.2 clearly shows the intermediate bridging member 4 placed on the sloped edge 310 of the floatable member 3. In this way the diameter of the contact surface is broadened (see Figures2.1) and the contact is prepared between the sloped edge 310 of the floatable member 3 and the bottom contact surface 210 of the flange 2.

It will be seen from Figure 5.2 that the floatable member 3 is moved upwards in the direction of the arrow from the initial position in Figure 5.1 by the increased volume of the inside liquid 610. The initial liquid level inside 600 is risen to the higher liquid level inside 601 by pumping liquid from outside the elongated member 1 to the inside liquid 610 through the feed line 9, the pressurization means 5 and the fluid connection 27. The volume of the inside liquid 610 thus increases as the inside liquid 610 is closed off by the elongated member 1 and the soil 10. The engaged state shown in Figure 5.2 clearly shows the floatable member 3 in contact with the flange 2 and unable move upwards anymore by way of the intermediate bridging member 4.

According to this preferred embodiment, the pressurization means 5 can always be removed after the installation is complete and the intermediate bridging member 4 does not have to be fluid tight.

Figure 6 shows a schematic cross sectional view of the engaged state of the floatable member 3 where the floatable member 3 functions as a support for a secondary structural element 1000. As known from the prior art, the secondary structural element 1000 is positioned on top of the elongated member 1 and is connected through the load bearing connection 22 (e.g. grout) all together forming an assembly 2000. The secondary structural element 1000 typically comprises a top side 1020 and a vertical side wall 1030 both with a substantially circular cross section where the top side 1020 typically has a smaller diameter than the vertical side wall 1030. The diameter of the cross section of the vertical side wall 1030 is sufficiently larger than the diameter of the cross section of the elongated member 1 so as to create a gap for the bearing connection 22 in between. The top side 1020 is connected to the side wall 1030 through the sloped contact surface 1010, which has the diameter of the top side 1020 at one end and the diameter of the side wall 1030 at the other end, giving it a tapered shape.

In accordance with the invention, prior to placing the secondary structural element 1000, the floatable member 3 is positioned inside the elongated member 1 and is supported by the buoyancy force of the second fluid 12 inside (e.g. air) created in the inside liquid 610. This buoyancy force is created by the difference in liquid level inside the elongated member 1 between the initial liquid level inside 600 and the initial floatable member liquid level 603 below the floatable member 3. The inside liquid 610 may be in an open connection to the outside liquid 620 surrounding the elongated member 1 and that will not change the buoyancy force.

Next the load bearing connection 22 between the elongated member 1 and the positioned secondary structural element 1000 is established. The floatable member 3 is further equipped as shown and described in the context of Figure 5.1 and may be positioned through any of the operations shown and described in the context of the Figures 3.1, 3.2 or 3.3.

From Figure 6 it can be seen that the intermediate bridging member 4 is placed on the sloped edge 310 of the floatable member 3 and is in contact with the sloped contact surface 1010 of the secondary structural element 1000, following its tapered shape of both sloped edge 310 and the sloped contact surface 1010. In this way the floatable member 3 has reached an engaged state where the upwards buoyancy force that acts on the floatable member 3 is transferred as lift to the secondary structural element 1000 by way of the sloped edge 310, the intermediate bridging member 4 and the sloped contact surface 1010. The magnitude of this upwards lift can be varied to be either large enough to completely carry the weight of the secondary structural element 1000 or to only partially reduce the load from the secondary structural element 1000 on the load bearing connection 22 to a desired magnitude.

The engaged state shown in Figure 6 can be reached by performing the steps of placing the intermediate bridging member 4 and lowering the secondary structural element 1000 in any order relative to each other, depending on what is the most efficient method.

In this preferred embodiment of the invention, the load reducing effect on the load bearing connection 22 is achieved by the weight the floatable member 3 carries. This amount is adjustable by changing the initial floatable member liquid level 603 - increase it, for example trough a pump or pressure vessel (not shown), in case a greater support force is needed for example during extreme loading of the secondary structural element 1000 during a heavy storm or reduce it through a valve (not shown). In addition, this embodiment is utilizable without the use of pressurization means 5 and can be performed even before the elongated member is driven in the soil 10.

Figures 7.1 and 7.2 show an alternative embodiment of the invention and the steps for reaching the engaged state of the floatable member 3 as a support of the secondary structural element 1000 wherein an additional support 13 is used for increased buoyancy while the pressurization means 5 is not required after finishing the installation.

In Figure 7.1 the elongated member 1 is driven into the soil 10. Inside of the elongated member 1, a support 13 is placed and the floatable member 3 is lowered on top of it. Typically the support 13 is substantially rigid and light-weight, generating a large buoyancy force when submerged in liquid. Flo wever, optionally the support 13 can be flexible so it can be inserted after the floatable member 3 is placed on the surface of the inside liquid 610 for example as foam injected beneath the floatable member 3 or as a flexible balloon.

After the floatable member 3 is lowered inside the elongated member 1, the level of the inside liquid 610 is decreased with the pressurization means 5 and the floatable member 3 is thus lowered in the direction of the arrows. Figure 7.1 shows that after lowering the support 13 and positioning the floatable member 3 on top, a sufficient portion of the inside liquid 610 is pumped out of the elongated member 1. The inside liquid 610 is sucked in through the fluid connection 27 that has one end submerged in the inside liquid 610 and the other end connected to the pressurization means 5. The inside liquid 610 is then further pumped out through the feed line 9 for example to the outside liquid 620 or to a temporary holding tank. Since the inside liquid 610 is isolated from the outside liquid 620 through the soil 10 and the wall of the elongated member 1, the initial liquid level inside 600 has dropped to the lower liquid level inside 602. Thus the support 13 and the floatable member 3 are lowered in the direction of the arrows. Optionally the inside liquid 610 can be pumped out to such a low level that the support 13 comes to rest with its bottom side on the soil 10.

From Figure 7.1 can be clearly seen that the secondary structural element 1000 is only then lowered and connected to the elongated member 1 through the load bearing connection 22. Lowering the floatable member 3 and the support 13 has cleared free access to the load bearing connection so that work on it can be easily performed.

Figure 7.2 shows the next step of bringing the floatable member 3 in an engaged state by lifting the support 13 back up in the direction of the arrow using the inside liquid 610 and letting the floatable member 3 support the secondary structural element 1000, thus, reducing the load on the load bearing connection 22. Figure 7.2 shows that, after having positioned the intermediate bridging member 4 as shown and described in the context with Figure 6, the inside liquid 610 is pumped back in the elongated member 1 to the initial liquid level inside 600. The additional inside liquid 610 is supplied by the pressurization means 5 though the connected feed line 9 and the fluid connection 27. In this way, the increased level of the inside liquid 610 lifts the support 13 and the floatable member 3 through the high buoyancy, positioning the intermediate bridging member 4 against the secondary structural element 1000 and exerting a force that compensates the load on the wall of the elongated member 1 and the load bearing connection 22.

According to this preferred embodiment the floatable member 3 is in an engaged state at the initial liquid level inside 600, thus, not requiring pumping liquid to a higher level, eliminating the need to sustain that higher level in case of a leak. This enables the removal of the pressurization means 5 after the completion of the installation. This execution is preferred in cases where after completion of the installation, no difference in the liquid level inside and outside the elongated member can be sustained. Optionally the pressurization means 5 can completely be omitted in this step, provided that the elongated member 1 is driven sufficiently shallow in the soil 10 to allow slow seepage of the outside liquid 620 to the inside liquid 610 due to overburden pressure.

The preferred embodiment shown in Figure 7.2 is identical to the engaged state of the floatable member 3 of Figure 6 with the single difference that the floatable member 3 of Figure 6 does not have the additional support 13. This preferred embodiment also has the additional advantages that the floatable member 3 or the intermediate bridging member 4 does not have to be fluid-tight as it relies on the buoyancy force from the support 13. It also enables a cheaper implementation as the support 13 can be manufactured from a cheaper material than the floatable member 3.

In this preferred embodiment of the invention, the use of the support 13 accomplishes the benefit that the floatable member can be in the engaged state at the initial liquid level inside 600 and the pressurization means 5 can be removed after the installation is completed. The buoyancy of the support 13 itself sustains a constant upwards force on the floatable member 3 keeping it in the engaged state. In this preferred embodiment, the intermediate bridging member 4 is not required to be fluid-tight.

Figure 8 shows an alternative embodiment for the execution of the positioning step for heights significantly above the level of the inside liquid 610. In this preferred embodiment the elongated member 1 is again driven into the soil 10 and supports the secondary structural element 1000 through a load bearing connection 22 (e.g. grout). The floatable member 3 is in contact with and supports the secondary structural element through the intermediate bridging member 4. However, in this preferred embodiment, the support 13 beneath the floatable member 3 comprises one or more separate support elements that may be hollow and tubular to reduce the cost of material and production for large dimensions. Being open at the bottom and closed at the top, the support elements are dimensioned such that they can hold a volume of a second fluid 12 (e.g. air) or other buoyant material sufficient to generate a significant upward force on the floatable member 3. In this floating state, the second fluid 12 displaces the inside liquid 610 below the floatable member 3 from the initial liquid level inside 600 downwards to an initial floatable member liquid level 603 that is proportional to the weight of the floatable member 3.The buoyancy force generated by the support elements is transferred to the secondary member 15 through the floatable member 3 and the optional intermediate bridging member 4. This preferred embodiment, thus, provides a reduced load on the regular load bearing connection 22 by providing an additional support to the secondary structural element 1000 through the upward force of the support 13 and floatable member 3. Between the separate support elements 13, and if necessary between the support elements 13 and the inner wall of the elongated member 1, spacers 23 are placed to increase the stability and optionally provide increased friction under dynamic loading. The positioning step is executed similar to the way described in Figures 7.1 and 7.2, but this embodiment provides the option of reaching a greater height with a light-weight structure.

This method enables an engaged state of the floatable member 3 without supporting on the elongated member 1 or the need to maintain an elevated level of the inside liquid 610 after the installation has been completed (e.g. with a pump). The support 13 provides the ability to support the floatable member 3 at a level substantially higher than the initial liquid level inside 600 through its elongated shape - it elevates the floatable member 3 up while itself still being submerged in the inside liquid 610.

The use of a separate support 13 also enables the production of the support 13 from a separate and cheaper material than the floatable member 3 itself, which is a practical benefit when the elevation height difference between the secondary structural element 1000 and the initial liquid level inside 600 is large.

Figures 9 and 10 show an alternative embodiment of the positioning step of the installation method wherein the positioning of the floatable member 3 is done without the use of a support device. According to this preferred embodiment, the change of the level of the inside liquid 610, as it changes under the influence of the tide (high-tide, low-tide), is used to adjust the position of the floatable member 3 in a vertical direction. This execution is preferred in cases where after completion of the installation a changing difference in the liquid level inside and outside the elongated member is desired.

Figure 9 shows the adjustment of the position of the floatable member 3 in an upward direction by relying on the increasing water level at high tide. This preferred embodiment is beneficial in the cases where the level of the engaged state of the floatable member 3 is above the water level during the lowering step. The figures 9a, 9b and 9c show three consecutive steps of the positioning. In Figure 9a the elongated member 1 is shown already driven into the soil 10. The elongated member 1 comprises the upper flange 201 close to the upper end and the through hole 25 close to the bottom end. The upper flange 201 is positioned on the inside of the elongated member 1 and at the level of the high-tide water level HT. The through hole 25 is positioned below the level of the low-tide water level LT and comprises the two-directional valve 24 allowing the restriction of liquid flow through the through hole 25. The inside liquid 610 inside the elongated member 1 is connected to the outside liquid 620 surrounding the elongated member 1 through the through hole 25 and the valve 24. Through this connection, the initial liquid level inside 600 is established equalizing the inside liquid 610 and the outside liquid 620 at the low-tide water level LT. Figure 9a further shows the lowering step where the floatable member 3 is first lowered during low-tide with the lifting means 7. After this, the floatable member 3 is left to be supported by the inside liquid 610 and equipped with the intermediate bridging member 4.

Figure 9b again shows the inside liquid 610 in connection with the outside liquid 620 through the through hole 25 and the valve 24. The increased level of the outside liquid 620 to the level of the high-tide water level HT has also increased the level of the inside liquid 610 to a higher liquid level inside 601 by the liquid passing through the through hole 25 and entering the elongated member 1. When the high-tide water level HT is reached, the floatable member 3 has been lifted to the level of the upper flange 201 and is pressed against its lower end through the fluid tight intermediate bridging member 4 achieving the desired engaged state. The floatable member 3 may additionally be physically locked or bolted in this position to the upper flange 201.

Figure 9c shows the floatable member 3 in the engaged state during the low-tide of the next tidal cycle. In this engaged state the advantage is created that the floatable member 3 remains at its position by either the suction created by the floatable member 3, the water tight intermediate bridging member 4 and the upper flange 201 or by restricting the outflow through the valve 24 from the inside liquid 610 to the outside liquid 620. This adds the significant mass of the entrapped inside liquid 610 acting as a mass damper in the system, reducing the loads.

Figure 10 shows the adjustment of the position of the floatable member 3 in a downward direction by relying on the dropping water level at low tide. This preferred embodiment is beneficial in the cases where the level of the engaged state of the floatable member 3 is below the water level during the lowering step. Figures 10a, 10b and 10c show three consecutive steps of the positioning. In Figure 10a the elongated member 1 is shown already driven into the soil 10. The elongated member 1 comprises the lower flange 202 close to the lower end and the through hole 25 below it. The lower flange 202 is positioned on the inside of the elongated member 1 and at the level of the low-tide water level LT. The through hole 25 is positioned below the level of the low-tide water level LT and comprises the two-directional valve 24 allowing the restriction of liquid flow through the through hole 25. The inside liquid 610 inside the elongated member 1 is connected to the outside liquid 620 surrounding the elongated member 1 through the through hole 25 and the valve 24. Through this connection, the initial liquid level inside 600 is established equalizing the inside liquid 610 and the outside liquid 620 at the high-tide water level HT. Figure 10a further shows the lowering step where the floatable member 3 is first lowered during high-tide with the lifting means 7. After this, the floatable member 3 is left to be supported by the inside liquid 610.

Figure 10b again shows the inside liquid 610 in connection with the outside liquid 620 through the through hole 25 and the valve 24. The decreased level of the outside liquid 620 to the level of the low-tide water level LT has also decreased the level of the inside liquid 610 to a lower liquid level inside 602 by the liquid passing through the through hole 25 and entering the elongated member 1. When the low-tide water level LT is reached, the floatable member 3 has been lowered below the level of the lower flange 202 and once passed that level is equipped with the fluid tight intermediate bridging member 4.

Figure 10c shows the floatable member 3 in the engaged state during the high-tide of the next tidal cycle where the floatable member 3 is pressed against the lower end of the lower flange 202 achieving the desired engaged state. This creates the advantage that the floatable member 3 remains at its position and creates an overpressure in the inside liquid 610 created by the risen outside liquid 620 through the valve 24 of the through hole 25. This increased pressure acts as a pre-stress force, reducing the loads in the wall of the elongated member 1 below the level of the floatable member 3. The floatable member 3 may additionally be physically locked or bolted in this position to the lower flange 202.

In addition to the two extreme cases of the engaged state embodiments of Figure 9 and Figure 10, any intermediate configuration of the embodiments can also be applied. For example arranging a flange at a level in between the high-tide water level HT and the low-tide water level LT. This resulting configuration will provide a combination of the benefits from each of the extreme cases according to the ratio of the level of the flange and the high-tide/low-tide levels. Thus, for a certain period of time the benefit of the added mass and for the remaining period of time the benefit of the pre-stress.

Although in both embodiments of Figure 9 and 10 the order of the steps in relation to the tidal movements is different, both embodiments have in common that they utilize the change in the surrounding water level during the tide in order to position the floatable member without the use of an additional lifting means such as a crane.

Figures 11, 12.1, 12.2 and 12.3 show detailed cross section views corresponding to area B of Figure 4.2, of the sealing step between the flange 2 and the floatable member 3 in a fluid tight way.

Figure 11 shows the cross section view of the first preferred embodiment for the sealing step between the flange 2 and the floatable member 3. On the surface of the inside liquid 610 is positioned the floatable member 3 comprising the sloped edge 310 in its circumference, giving it a tapered shape, and the bottom wall 320 in contact with the inside liquid 610. The sloped edge 310 and the bottom wall 320 are able to be one unit or the sloped edge 310 and the bottom wall 320 are able to be two units attached to each other e.g. bolted. Pressurization means 5 are further attached to the bottom wall 320 through the fluid connection 27.

The flange 2, arranged on the inside of the elongated member 1, comprises a bottom contact surface 210 and an attachment surface 220. The bottom contact surface 210 faces the sloped edge 310 and has a substantially similar slope. The attachment surface 220 connects the flange 2 to the inner wall of the elongated member 1 enabling the flange 2 and the elongated member 1 to be either one unit or two units attached e.g. bolted to each other.

In this preferred embodiment, the sealing contact in the engaged state between the flange 2 and floatable member 3 is established through the fluid tight intermediate bridging member 4 along the circumference of the floatable member 3. In Figure 11 the inner diameter of the flange 2 is shown to be larger than the outer diameter of the floatable member 3 enabling the floatable member 3 to pass through the gap along the center line C when lowered inside the elongated member 1 without touching the flange 2. After the floatable member 3 is positioned below the flange 2 the fluid tight intermediate bridging member 4 is positioned on top of the sloped edge 310 and below the bottom contact surface 210. The fluid tight intermediate bridging member 4, which is relatively flexible and able to absorb deformation, is dimensioned such that it covers the sloped edge 310 on the one side and fits underneath the bottom contact surface 210 on the other and in this way substantially follows the shape of the sloped edge 310 and bottom contact surface 210.

Once the intermediate bridging member 4 has been positioned, the pressurization means 5 is used to increase the level of the inside liquid 610 by pumping liquid inside the elongated member 1 and in this way lifting the floatable member 3 upwards. At the designated level in vertical direction, the sloped edge 310 comes into contact with the bottom contact surface 210 of the flange 2 through the intermediate bridging member 4. The upwards buoyancy force from the floatable member 3 presses the intermediate bridging member 4 together, creating a fluid tight connection, which locks the floatable member 3 into position and brings it in the engaged state. In this engaged state the advantage is created that the sloped edge 310 in combination with the shape of the bottom contact surface 210 provide a connection that does not require welding and gets tighter when the buoyancy force of the floatable member 3 is increased.

The shown embodiment of the engaged state of the floatable member 3 provides a way for the floatable member 3, which is non-deformable and from one piece, to be positioned below a flange 2 with a larger diameter such that afterwards the floatable member 3 can still be tightened up against the flange 2 and create a fluid tight connection.

Figure 12.1 shows an alternative embodiment for the execution of the fluid tight sealing step wherein the intermediate bridging member 4 comprises several bridging member layers 403 along the circumference of the floatable member 3. In this embodiment, both the flange 2 and the floatable member 3 have seal edges 240 and 340 that face each other and prevent the bridging member layers 403 from slipping out when the pressure is applied and they are pressed together. The advantage of the multiple layers is in the ease of installation where the weight can be distributed over several layers, each installed one by one and being able to be carried by the installation personnel by hand.

Figure 12.2 shows a further alternative embodiment for the execution of the fluid tight sealing wherein the intermediate bridging member 4 has a circular cross section and the seal edges 240 and 340 have a shape that follows the curvature of the intermediate bridging member 4. This preferred embodiment eliminates any pressure concentration that may arise when the floatable member 3 is pressed against the flange 2 after increasing the pressure of the inside liquid 610.

Figure 12.3 shows a further alternative embodiment for the execution of the fluid tight sealing wherein the elements of Figure 12.1 and 12.2 are combined, using several bridging member layers 403 that have a circular cross section. The layers are placed to rest on the sloped edge 310 of the floatable member 3 after the floatable member is lowered in the inside of the elongated member 1. These layers can have cross sections with different diameters, optimizing for weight and best fit in the gap between the lower side of the flange 2 and the sloped edge 310. After the pressure in the inside liquid 610 is increased these multiple layers are pressed together forming a fluid tight connection.

Figures 13, 14.1 and 14.2 show alternative configurations for the execution of the sealing step of the method wherein the connection created between the flange 2 and the floatable member 3 is not required to be fluid tight.

Figure 13 shows a preferred embodiment with the intermediate bridging member 4 placed on the sloped edge 310 of the floatable member 3. Herein, the intermediate bridging member 4 does not form a continuous layer in the circumference of the floatable member 3, but comprise several separate bridging members that can be placed separately from each other. In a preferred embodiment, the intermediate bridging members 4 can be interconnected with a seal interconnection 20 (e.g. steel rope) to enforce a particular position relative to each other and keep them in place when compressed in the sealing step by the sloped edge 310 against the flange 2. In Figure 13b a perspective view of the preferred embodiment is shown and a top view thereof is shown in Figure 13 a.

Figure 14.1a shows a schematic top plane view of the intermediate bridging member 4 in a preferred embodiment wherein the bridging members can be repositioned mechanically during installation. The extension rail 11 supports the extended bridging member 405 and the unextended bridging member 404. During installation, the unextended bridging members 404 are extended to come into contact with the sloped edge 310 of the floatable member 3. Figure 14.1b shows the cross sectional view of this preferred embodiment, wherein the direction of the outwards extension of the unextended bridging member 404 is indicated by the arrow.

Figure 14.2 shows an alternative embodiment of the modular extending bridging member in the three steps of installation. In Figure 14.2a is shown the begin state with the unextended bridging member 404 placed on the sloped edge 310 and connected to the other bridging members through the extension rail 11 and a pivot connection 26. The direction of outward extension of the unextended bridging member 404 is indicated by the arrow. In Figure 14.2b, the next step is shown of the unextended bridging member 404 pivoting around the pivot connection 26 and sliding down the sloped edge 310 of the floatable member 3 in the direction of the arrow. In Figure 14.2c the end-state is shown, wherein the extended bridging member 405 has reached its lowest position by sliding down and is ready to be pressed up by the floatable member 3 into the engaged state.

Figures 15.1 and 15.2 show the next step of the installation method according to the invention - the regulation of the closing force in the upwards direction. Herein the regulation force is determined at designing by the geometry of the floatable member.

Figure 15.1 shows two alternative embodiments for the closing force regulation step in the installation method with the shape of the floatable member 3 in conformity with Figure 3.1. In both cases the elongated member 1 is completely filled with the inside liquid 610 and the volume displaced by the floatable member 3 determines the force exerted upwards on the intermediate bridging member 4 and transferred to the flange 2. Figure 15.1a shows an embodiment wherein the force exerted by the floatable member 3 upwards after the completion of the sealing step is lower than in the embodiment shown in Figure 15.1b because of the smaller liquid volume displaced by the floatable member 3.

Figure 15.2 shows two alternative embodiments of the closing force regulation step in the installation method with the shape of the floatable member 3 in conformity with Figure 3.2. Figure 15.2a shows an embodiment wherein the force exerted by floatable member 3 upwards after the completion of the sealing step is lower than in the embodiment shown in Figure 15.2b. In Figure 15.2b, the elongated member 1 is completely filled with the inside liquid 610 and the volume displaced by the support 13 is greater, in this way exerting a greater upwards force in the intermediate bridging member 4 and transferred to the flange 2.

Figures 16.1 and 16.2 show an alternative embodiment of the closing force regulation step by floatable member 3 on the flange 2 wherein the force can be changed at the time of installation and/or at a later moment.

Figure 16.1 shows a cross section of the two consecutive steps of applying one preferred embodiment of the invention wherein the upwards force exerted by the floatable member 3 on the flange 2 through the intermediate bridging member 4 is regulated by the changing volume of the second fluid 12 inside the floatable member 3. After completion of the sealing step of the method according to the invention, the floatable member 3 is in contact with the flange 2 through the intermediate bridging member 4 and has an initial floatable member liquid level 603 created by the second fluid 12 displacing the inside liquid 610 as shown in Figure 16.1a. Then the pressurization means 5 is used to pump additional volume of the second fluid 12 (e.g. air) underneath the floatable member 3 through the fluid connection 27. This lowers the level of the inside liquid 610 from the initial floatable member liquid level 603 to the adjusted floatable member liquid level 604 as shown in Figure 16.1b, in this way increasing the lifting force, pressing the floatable member 3 against the flange 2 and bringing the floatable member 3 into the engaged state.

Figure 16.2 shows a cross section of the two consecutive steps of applying another preferred embodiment of the invention for the regulation of the upwards force exerted by the floatable member 3 for the case where the elongated member 1 supports the secondary structural element 1000. After completion of the sealing step, the floatable member 3 is in contact with the secondary structural element 1000 and has an initial floatable member liquid level 603 created by the second fluid 12 displacing the inside liquid 610 as shown in Figure 16.2a. Then the pressurization means 5 is used to pump additional volume of the second fluid 12 (e.g. air) underneath the floatable member 3 through the fluid connection 27. This lowers the level of the inside liquid 610 from the initial floatable member liquid level 603 to the adjusted floatable member liquid level 604 as shown in Figure 16.2b, in this way increasing the lifting force, pressing the floatable member 3 against the secondary structural element 1000 and bringing the floatable member 3 into the engaged state. In this engaged state the secondary structural element 1000 can partially support its weight on the floatable member 3 instead of only on the load bearing connection 22.

Figure 17 shows a cross section of the two consecutive steps of applying another preferred embodiment of the invention wherein the upwards force exerted by floatable member 3 on the flange 2 through the intermediate bridging member 4 is regulated through a positioning means 16 (e.g. mechanical, hydraulic or otherwise). After the completion of the sealing step of the method, the space under the floatable member 3 comprises a support 13 and a second fluid 12 with an initial floatable member liquid level 603, wherein the support is connected to the floatable member 3 through a positioning means 16 and is positioned in its highest position as shown in Figure 17a. In the step of changing the closing force, the vertical positioning means 16 is used to push the support 13 further down into the inside liquid 610. In this the displaced volume inside the elongated member 1 may be increased, thereby raising the initial floatable member liquid level 603 to the adjusted floatable member liquid level 604. This increases the upward lifting force transferred from the support 13 through the positioning means 16 to the floatable member 3, thereby pressing the intermediate bridging member 4 into the flange 2 and bringing the floatable member 3 into the engaged state.

Figure 18 shows the cross sectional view of an alternative engaged state of the floatable member 3 by locking it into position on the top end of the elongated member 1 and underneath the secondary structural element 1000. According to this preferred embodiment, the initial liquid level inside 600 of the inside liquid 610 is first risen with the pressurization means 5, lifting the floatable member 3 up. The floatable member 3 is lifted in this manner until the intermediate bridging member 4, which is placed on the sloped edge 310 and is comparatively flexible and able to absorb deformation, is compressed against the secondary structural element 1000 in the direction of the arrows beyond its normal operating dimensions. This opens up a gap between the bottom end of the floatable member 3 and the top end of the elongated member 1. A contact support 17 (possibly pre-compressed) is then placed on the top end of the elongated member 1, providing support to the floatable member 3 placed on top of it, and the level of the inside liquid 610 is returned to the initial liquid level inside 600. This allows the flexible intermediate bridging member 4 to expand back to its operating dimensions, pushing the floatable member 3 back down and slightly compressing the contact support 17. In this engaged state, both the intermediate bridging member 4 and the contact support 17 are in slight compression and the load on the existing load bearing connection 22, between the elongated member 1 and the secondary structural element 1000, is reduced by transferring part of it through the intermediate bridging member 4, the floatable member 3 and the contact support 17 directly into the elongated member 1. The additional advantage of this installation is that the need for hydraulic jacks for the positioning of such a load reducing device are not required and can be omitted to reduce the installation time and cost.

Figure 19 shows a detailed cross sectional view of an alternative embodiment wherein the contact support 17 is connected and merged with the intermediate bridging member 4, providing the contact with both the elongated member 1 and the secondary structural element 1000 through an optional flange 2. The connection of the contact support 17 is tightened through the insertion of a stretching means, which can be for example the end of the floatable member 3.

Figure 20 shows another preferred embodiment wherein the floatable member 3 is brought into an engaged state through an inner spreader member 181 instead of using the liquid inside the elongated member 1. The cross sectional view in Figure 20 shows the floatable member 3 resting on top of the elongated member 1 through the contact support 17.

On the inner sloped edges 310 of the floatable member 3, an inner spreader member 181 is placed. The inner spreader member 181 is connected to the floatable member 3 through the bolted connection 19. The inner spreader member 181 can comprise of one single piece or several separate segments that are connected to each other. This connection can be realized either through direct contact of their side faces or through a dedicated connecting element, that can be rigid or flexible, such as a rod, a brace, a spring etc. The connection between the separate components of the inner spreader member 181 can be established between neighboring segments, but in some cases it may be more beneficial to be established between diametrically opposing segments.

On the outer sloped edge 310 of the floatable member 3, an intermediate bridging member 4 is placed that provides support to the secondary structural element 1000. During the installation, first the floatable member 3 is placed to rest on the contact support 17 and the intermediate bridging member 4 is placed on its outer sloped edge 310. Next, an inner spreader member 181 is placed on the top and inside of the floatable member 3 with the sloped edges 310 towards each other, so they are free to slide relative to each other following their tapered shape. The floatable member 3 and the inner spreader member 181 are then connected through a bolted connection 19. The inner diameter of the floatable member 3 and the outer diameter of the inner spreader member 181 are such that in the initial position of placement there is a gap between the top of the floatable member 3 and inner spreader member 181 in the axis of the bolted connection allowing for changes in the distance between the two. The bolted connection 19 is then used to tighten the inner spreader member 181 towards the floatable member 3 whereby their sloped edges slide against each other and the inner spreader member 181 lowers and thereby partially sinks in the floatable member 3. Because the inner spreader member 181 engages over its circumference via its sloped edge 310, it spreads out the floatable member 3 when it is lowered, and in this way presses the intermediate bridging member 4 into place against the secondary structural element 1000. This brings the floatable member 3 into the engaged state.

In an alternative embodiment shown in Figure 21, an outer spreader member 182 is used to bring the floatable member 3 in an engaged state. In this preferred embodiment the floatable member 3 is placed on the top end of the elongated member 1, resting on the contact supports 17, and the intermediate bridging member 4 is placed on top of the sloped edge 310 of the floatable member 3. Then, the outer spreader member 182, also comprising a sloped edge 310, is placed to the outside of the floatable member 3 between the intermediate bridging member 4 and the floatable member 3. The outer spreader member 182 and the floatable member 3 are in contact with each other through their sloped edges 310, free to slide relative to each other. The outer spreader member 182 is bolted to the top of the floatable member 3 through the bolted connection 19. By tightening the bolted connection 19 the outer spreader member 182 slides down and supporting on the sloped edge 310 presses the intermediate bridging member 4 against the secondary structural element 1000 bringing the floatable member into the engaged state.

Figure 22a shows a further preferred embodiment for the step of positioning and locking the floatable member 3 on the top end of the elongated member 1 using of an inside liquid 610. According to this preferred embodiment, the secondary structural element 1000 is supported by the elongated member 1 through the load bearing connection 22. The elongated member 1 is filled with the inside liquid 610 with an initial liquid level inside 600. The inside liquid 610 supports the floatable member 3 comprising a support edge 350 in its circumference and a support 13 ensuring a desired amount of liquid displacement. To the floatable member 3 is attached a pressurization means 5 (e.g. a pump) with a feed line 9.

During installation, the floatable member 3 is lowered in the inside liquid 610 and floats supported by the buoyancy of the support 13. Next, an intermediate bridging member 4 is placed on top of the support edge 350 and the pressurization means 5 is used to increase the level of the inside liquid 610, lifting the floatable member 3 up and pressing the intermediate bridging member 4 upwards against the walls of the secondary structural element 1000 beyond its normal operating dimensions. In order to prevent the intermediate bridging member 4 from sliding away under the compression towards the middle of the secondary structural element 1000, the support edge 350 may comprise a limiter 360. This compression of the intermediate bridging member 4 increases the space between the bottom side of the support edge 350 and the top end of the elongated member 1, where the contact support 17 is placed, possibly in a compressed and prestressed state.

Finally, the level of the inside liquid 610 is returned to the initial liquid level inside 600, for example by using the pressurization means 5 or any other convenient approach to extract the excess inside liquid 610, and the connection between the secondary structural element 1000 and the top end of the elongated member 1 is established through the support contact supports 17 circumventing the load bearing connection 22 and reducing the load on it.

In an alternative embodiment shown in Figure 22b, the floatable member 3 comprises a detachable support edge 355. This provides the additional benefit of being able the detach the floatable member 3 from the detachable support edge 355 after the installation is complete and remove the floatable member 3 while leaving the detachable support edge 355 in its place as a support for the secondary structural element 1000.

Although they show preferred embodiments of the invention, the above described embodiments are intended only to illustrate the invention and not to limit in any way the scope of the invention. Accordingly, it should be understood that where features mentioned in the appended claims are followed by reference signs, such signs are included solely for the purpose of enhancing the intelligibility of the claims and are in no way limiting on the scope of the claims. Furthermore, it is particularly noted that the skilled person can combine technical measures of the different embodiments. The scope of the invention is therefore defined solely by the following claims.

Claims

A method for installing an elongated member or an assembly thereof, comprising the steps of: providing an elongated member comprising a circumferential wall and an inner space extending in the longitudinal direction of the elongated member: in or on arranging the bottom of the elongate member; arranging a float member in the interior of the elongate member or assembly; moving the driver by supplying and / or regulating fluid in the interior of the elongate member or assembly; and bringing the driver into an engaged state with the elongate member or assembly when the fluid level in the interior space has moved the driver to a desired level.

The method of claim 1, wherein the driver is disposed on the elongate member or assembly.

Method according to claim 1 or 2, comprising the steps of: installing the elongate member in a water body; providing at least one bore in the peripheral wall of the elongate member, the bore being arranged at a level between the bottom and the water level of the body of water; filling the inner space with water that is allowed to flow into the inner space via the bore when the water level of the body of water is higher than the water level in the inner space; and preventing water from flowing back from the interior through the bore out the elongate member.

The method of claim 3, comprising the step of installing the elongate member in a tidal body of water.

The method of claim 4, wherein the piercing is arranged below the ebb water level of the tidal body of water.

6. Method as claimed in claim 4 or 5, wherein the bore is provided with a valve which is adapted to prevent water from flowing from the inner space through the bore to the outside of the elongate member.

A method according to any one of the preceding claims, wherein the driver is a sealing member.

The method of claim 7, wherein the sealing member is adapted to provide a fluid-tight seal in the interior space.

A method according to any of claims 7-8, comprising the step of bringing the sealing member into a substantially fluid-tight sealing state when the fluid level in the inner space is at a desired level.

Method according to any of claims 7-9, comprising the step of bringing the sealing member into a substantially fluid-tight sealing state when the water level in the inner space is substantially at or above the position of the seal.

A method according to any of claims 7-9, comprising the step of filling the interior of the elongate member with liquid to at least a level that is substantially at or near the ebb water level of the tidal body of water.

A method according to any of claims 7-9, comprising the step of filling the interior of the elongate member with liquid to a level that is substantially between the ebb and flow level of the tidal body of water, more preferably wherein the interior space is filled to a level in the range of 25% - 75% of the range between the ebb and flood water level of the tidal body of water.

A method according to any of claims 7-9, comprising the step of filling the interior of the elongate member with fluid to at least one level substantially at or near the flood level of the tidal body of water.

A method according to any one of the preceding claims, wherein the driver is a support member.

The method of claim 14, wherein the elongate member or assembly and the support member comprise a chamfered shape matched to each other.

A method according to any of claims 7-15, wherein an intermediate bridge member is arranged between the sealing member and the elongated member or assembly before the sealing member has reached its sealing condition.

17. Method as claimed in any of the claims 14-16, wherein a spreader member is provided, and wherein the support member and the spreader member comprise bevelled surfaces that are aligned with each other and that can be engaged such that a radial force via a shear displacement of the cooperating bevelled surfaces on the support member can be exercised.

A method according to any one of the preceding claims, wherein the driver is mountable on a support provided in the elongate member.

A method according to any one of the preceding claims, wherein the assembly comprises a monopile and a transition part, and wherein the driver is arranged between the monopile and the transition part such that it provides a force transmitting member between the monopile and the transition part.

A method according to any of claims 7-13, comprising the step of removing or adding air between the sealing member and the water level within the interior of the elongate member via a valve or pump which is in fluid communication with the space immediately below the sealing member state.