Patent Description:
The invention further relates to a method of assembling such an assembly of a first and a second member that each comprise at least one through hole.

The present invention is particularly suitable for offshore applications, e.g. for connecting a wind turbine to a monopile, a wind turbine to a transition piece, a transition piece to a monopile, as well as between members of a monopile or wind turbine, and jacket connections.

According to prior art applications in offshore, the members of such assemblies are provided with flanges which are connected using bolts of significant size. Currently M72 bolts are used for connecting a wind turbine tower to a monopile or transition piece. In a first step, these bolts are electrically tightened with <NUM>. In a second step, the preload is increased with hydraulic tools to <NUM>. The bolts itself are heavy and the tools for tightening the bolts is also heavy and hard to handle.

It appears that the actual preload on the bolts after some settling time is hard to predict and control, and may vary significantly. Although it is not exactly clear which factors influence the torque-tension relationship of the bolts, it may be concluded that installing the bolts using a "constant torque" method does not achieve satisfying results. Similar issues occur with tensioning systems for bolting. The preload on the bolts must be regularly checked and adjusted, periodically requiring significant maintenance work.

Furthermore, the bolts are arranged all around the circumference of the flanges, leaving only a very limited gap between adjacent bolts. A connection using flanges with bolts is insufficiently scalable to meet the ever increasing demands resulting from even larger wind turbines and greater depths as sea where they are installed.

International patent application <CIT> of Applicant proposes an assembly that is improved relative to a connection using flanges connected by bolts. This improved prior art assembly comprises:.

The United States patent application <CIT> is directed to an expansion pin system for construction of a wind turbine structural tower, and is considered the closest prior art. It discloses, in terminology of the present invention, a first and a second member, wherein the second member has a fork-shaped cross section with a main body and two substantially parallel walls that each comprise at least one through hole, wherein the first member is arranged between the two walls of the second member, having the through hole, and wherein said through hole of the first member and the through holes of the second member are aligned to define a channel. The expansion pin may be interpreted as a connector that is axially insertable in said channel to an end position and consecutively expandable radially relative to said channel, to connect the first and second member relative to each other. When the expansion pin system is inserted into the channel it results in an alignment of the through holes of the first and the second member.

The United States patent <CIT> discloses a configuration that shows some similarity to <CIT>. In terminology of the present invention, it discloses a first and a second member, wherein the second member has a fork-shaped cross section with a main body and two substantially parallel walls that each comprise at least one through hole, wherein the first member is arranged between the two walls of the second member, having the through hole, and wherein said through hole of the first member and the through holes of the second member are aligned to define a channel. A clevis bushing may be interpreted as a connector that is axially insertable in said channel to an end position and consecutively expandable radially relative to said channel. This clevis bushing, upon radially expansion thereof, clamps itself in a through hole of one wall of the fork-shaped second member, and furthermore presses the first member in axial direction against the other wall of the fork-shaped second member.

The European patent publication <CIT> discloses a number of adjustable locking devices located between segments of a cylindrical shell of a stator of an electric generator of a wind power turbine. These adjustable locking devices are configured to press the segments together circumferentially and lock the segments in a give position. The device of <CIT> fails to disclose a second member that has a fork-shaped cross section with a main body and two substantially parallel walls that each comprises at least one through hole, wherein a first member is arranged between the two walls of the second member, having the through hole.

The expansion bolt of United States patent <CIT>, the anchor bolt disclosed in <CIT>, and the United States patent <CIT>, which discloses a method for inserting rivets in a pocket knife with a needle like insertion tool, are acknowledged as further prior art.

An object of the present invention is to provide an assembly, 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 assembly according to claim <NUM> of the present invention.

As a result of the pre-tensioned connection between the first member and the second member any load fluctuations going through the connector are reduced significantly resulting in very low fatigue damage levels compared to a non pre-tensioned connection.

The United States patent application <CIT> fails to disclose that the connector, in an expanded state thereof, pushes the first member against the main body of the second member to define a pre-tensioned connection between the first member and the second member. After all, a male flange end which may be considered the first member, is arranged in between two flanges of a female end of the connector, with a free end of said male flange end being disposed at a distance from the connector. From a perspective of alignment of the holes, as obtained by the expansion pin of <CIT>, it makes perfect sense that the male flange end, i.e. the first member, has a free end. However, a perfect alignment is not desired in view of obtaining an optimal pre-tensioning of the connection between the first member and the second member.

Relative to the assembly of <CIT>), a user may insert a connector into the channel to an end position in a first step, followed by a further step of consecutively expanding said connector radially relative to said channel, to thereby connect the first and second member relative to each other. In this way, the connector may be accurately and easily placed in the channel by a user with very limited hassle or force. Only when the connector is placed in its desired end position, it is expanded in the channel to connect the first and second member relative to each other. Use of a connector according to the invention also makes specially machined contact surfaces with an inclination corresponding to an inclination of the radially displaceable actuator redundant.

Relative to the older prior art of bolted flanges, large scale (e.g. M72) bolts are redundant. Also, the body may be less bulky than a flange comprising through holes to accommodate a bolt. As a result, the assembly according to the invention, requires less material, is therefore more compact and lighter, and also more elegant. Whereas thick parts need to be forged, smaller parts may also be rolled, possibly allowing the members to be formed with alternative and more attractive manufacturing methods. Also, the assembly according to the invention is scalable, providing the opportunity to arrange multiple connectors in axial direction of the members.

A further advantage of the proposed assembly relative to bolted flanges, is the absence of these flanges, that would provide a significant mass outside the path where forces travel during driving the assembly into a ground using a hammer. The mass of conventional flanges may result in bending of the neck of the flanges. These bending stresses currently result in significantly reduced life time of the welds of these flanges when installed with a conventional impact hammer.

An even further advantage of the proposed assembly relative to bolted flanges, is that it may be applied for connecting members under the waterline. On the one hand, longitudinal members of a limited length may be used, allowing smaller ships to transport them to a desired location for an offshore construction.

The successively tightening the bolts of a bolted flange - which are typically tightened in multiple steps, as mentioned above - is very time consuming and labor-intensive. The proposed assembly is less labor-intensive and time consuming than a connection having bolted flanges.

According to a preferred embodiment, the connector, in the expanded state thereof, pushes against faces of the through holes of the second member that are directed away from the main body thereof to define the pre-tensioned connection between the first member and the second member.

According to a further preferred embodiment, in the expanded state of the connector, wherein the connection between the first member and the second member is pretensioned, the through hole of the first member is arranged at an offset relative to the through holes in the second member. As mentioned above, said through hole of the first member and the through holes of the second member define a channel, which means that said through holes are positioned in a way that they are "substantially" aligned. However, a preferred offset may guarantee that there always remains a slight misalignment of the through hole of the first member relative to the through holes of the second member. This is advantageous, because the offset, i.e. the slight misalignment in the channel, guarantees that the connection between the first member and the second member may be optimally pre-tensioned. After all, the connector is configured to expand in the channel, wherein the connector pushes the first member against the main body of the second member. In order to optimally push the first member towards the main body of the second member, it is beneficial if the side of the connector that is directed towards the main body does not come into contact with the inner walls of the through holes in the parallel walls of the second member. In this way, the side of the connector that is directed towards the main body can fully transfer its compressive force to the first member that is pressed towards and against the main body of the second member to obtain the desired pre-tensioning.

According to a preferred embodiment, the connector comprises:.

In the compacted state, play between the connector and the inner wall of the channel allows the connector to be easily inserted into the channel. Afterwards, a high axial clamping force may be provided by the connector, which has the advantage that the assembly is less susceptible for load variations. This is best understood when compared to how a bolted joint carries a direct load. An adequately pretensioned bolt can survive in an application that an untightened, or loose bolt, would fail in a short period of time. The bolt only 'feels' a small portion of the applied load.

The invention is furthermore directed to a method according to claim <NUM> of assembling a first and a second member that each comprises at least one through hole, said method comprising the steps of:.

In a preferred embodiment, the above mentioned method steps are preceded by the step of positioning at least one of said first and said second member by hoisting thereof, wherein a hoisting equipment engages at least one of the through holes of said respective first or second member. As the connector may be a separate unit that is only inserted into the channel during assembly, the through holes in the first and the second member may be effectively used during hoisting thereof.

In a further preferred embodiment of said method, an elongate member, preferably a rod, is arranged through at least one of the through holes to connect the respective first or second member to the hoisting equipment.

Further preferred embodiments are the subject of the dependent claims.

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

An example of an offshore construction comprising multiple connections C where an assembly according to the invention may be applied is shown in <FIG>. An offshore wind turbine tower <NUM> is supported by a supporting base structure <NUM> which is in <FIG> embodied as a monopile <NUM> with a transition piece <NUM>. The skilled person will understand that similar connections are present for alternative supporting base structures <NUM>, such as (not shown) jackets.

The connections C may be applied between separate members <NUM> of the monopile <NUM>, between the monopile <NUM> and the transition piece <NUM>, between the transition piece <NUM> and the turbine tower <NUM>, between members <NUM> of the turbine tower <NUM>, and between a rotor blade <NUM> and a hub of a rotor.

During use, a wind turbine <NUM> will be oriented such that the rotor blades <NUM> are optimally driven by the available wind power. The rotor blades <NUM> drive a (not shown) generator in the nacelle <NUM>, wherein the generator generates electricity. The wind turbine <NUM> causes alternating loads on any connection C in the construction, and dependent on the wind direction, specific parts of the connection C have to absorb most of the loads.

According to the prior art (<FIG>), an assembly <NUM> configured to connect a first member <NUM> and a second member <NUM> normally comprises flanges <NUM>, <NUM>. These flanges <NUM>, <NUM> are provided with through holes <NUM>, <NUM>, which are aligned. A bolt <NUM> and nut <NUM> assembly is then arranged through the aligned through holes <NUM>, <NUM>, and used to clamp the flanges <NUM>, <NUM> to each other. As already described, currently M72 bolts <NUM> are used for connecting a wind turbine tower <NUM> to a monopile <NUM> or transition piece <NUM>. The bolts <NUM> itself are heavy and the tools for tightening the bolts <NUM> are also heavy and hard to handle. Moreover, the preload on the bolts <NUM> must be regularly checked and adjusted, periodically requiring significant maintenance work.

In order to accommodate the through holes <NUM>, <NUM> and create an effective preload between both flanges <NUM>, <NUM>, the flanges <NUM>, <NUM> need to be relatively thick in both axial direction. In order to prevent that the flange becomes an effective lever when a significant tensile load is applied on the steel wall that is welded to flange <NUM> the flange also needs to be wide (in the radial direction).

The assembly according to the present invention comprises a first member <NUM> and a second member <NUM>, each comprising at least one through hole <NUM>-<NUM>. The through holes <NUM>-<NUM> may be directly arranged in the first member <NUM> and the second member <NUM>, and consequently flanges <NUM>, <NUM> as shown in <FIG> are redundant. This has several advantages, one of them being a saving of material. The second member <NUM> is made up out of an amount of material that is approximately also present in a single one of the flanges <NUM>, <NUM> of <FIG>. However, the material required for the first flange <NUM> in <FIG> is completely saved. Also, due to the absence of flanges <NUM>, <NUM>, there is less weight outside the line of travel of forces through the assembly. Moreover, a labour intensive and costly welding operation is prevented.

A taper angle at the bottom of second member <NUM> and a taper angle at the top of first member <NUM> allows for a certain amount of ovality in either member <NUM> or <NUM> to be forced back into a round shape under the force of gravity by pushing second member <NUM> into first member <NUM>.

In the shown embodiment, the first member <NUM> comprises one through hole <NUM>, and the second member comprises two through holes <NUM>, <NUM>. In the assembly, the through holes <NUM>-<NUM> of the first <NUM> and the second member <NUM> together define a channel <NUM>. A connector <NUM> is axially insertable in said channel <NUM> to an end position and consecutively expandable radially relative to said channel <NUM>, to connect the first member <NUM> and the second member <NUM> relative to each other.

The connector <NUM> comprises a compacted state (shown <FIG>), wherein the connector <NUM> has a size that is freely insertable into and out of the channel <NUM>, and a connecting state (e.g. shown in <FIG> and <FIG>) wherein the connector is expanded in the channel <NUM> to connect the first <NUM> and second member <NUM> relative to each other.

The description is this paragraph relates to the orientation shown in <FIG>, but the skilled person will understand the same principle may also be applied in other orientations, such as transverse or upside down relative to <FIG>. In the connecting state shown in <FIG>, the connector <NUM> contacts at its lower side with faces <NUM> formed at the lower side of the respective through holes <NUM>, <NUM> of the second member <NUM>. The upper side of the connector <NUM> contacts a face <NUM> that is arranged at the upper side of the through hole <NUM> in the first member <NUM>. In the expanded state of the connector <NUM>, the connector <NUM> pushes faces <NUM> of the second member <NUM> away from face <NUM> of the first member <NUM>. Consequently, the second member <NUM> is pushed downward relative to the first member <NUM>, and a clamping contact is formed between a face <NUM> defined by the upper side of the first member <NUM>, and a face <NUM> defined by the second member <NUM>. Thus, by expanding the connector <NUM>, a pre-tensioned connection between the first member <NUM> and the second member <NUM> can be formed. The faces <NUM>, <NUM>, <NUM>, <NUM> can be best seen in <FIG>. By having sufficient pretension, the load fluctuations going through the connector <NUM> are reduced significantly resulting in very low fatigue levels.

The connector <NUM> comprises at least one expansion block <NUM>, at least one wedge <NUM>, and an actuator <NUM> configured to displace the wedge <NUM> relative to the expansion block <NUM>. The wedge <NUM> has an inclined surface <NUM> facing the at least one expansion block <NUM>.

The connector <NUM> preferably comprises at least one wedge <NUM> that is arranged between two expansion blocks <NUM>, and more preferably the connector <NUM> comprises two wedges <NUM>. In the shown embodiment, two wedges <NUM> are arranged between two expansion blocks <NUM>. The two wedges <NUM> are symmetrically arranged with inclinations of the inclined surface <NUM> thereof directed away relative to each other.

The actuator <NUM> may be a bolt <NUM> that engages in a threaded recess <NUM> of the wedge <NUM>. Optionally a washer <NUM> may be placed between the head of the bolt <NUM> and the wedge <NUM>. By turning the bolt <NUM>, the wedges <NUM> may be pulled together over a distance corresponding to the thread of the bolt <NUM>. When two wedges <NUM> are used, the displacement is divided over both wedges <NUM>. The thread may be interpreted as a first transmission and the division over both wedges as a second transmission. Via the inclined surface <NUM>, which may be interpreted as a third transmission, the connector <NUM> is expanded, i.e. the expansion blocks <NUM> are pressed outward relative to each other when the wedges <NUM> move towards each other. One of the expansion blocks <NUM> engages with the faces <NUM> of the second member <NUM>, i.e. the lower expansion block <NUM> shown in <FIG>. The other expansion block <NUM>, i.e. the upper expansion block <NUM> shown in <FIG>, engages with the face <NUM> of the first member <NUM>. In this way, if the expansion blocks <NUM> are pressed outward relative to each other, the above described pre-tensioned connection between the first <NUM> and the second member <NUM> can be formed.

The inclined surface <NUM> of said wedge <NUM> may comprises an inclination with an angle of less than <NUM>°, preferably less than <NUM>°, more preferably less than <NUM>°, and most preferably equal to or less than <NUM>°, relative to a displacement direction of said wedge <NUM>. This displacement direction coincides with the longitudinal direction of the bolt <NUM>. By providing an inclination with a relatively flat angle, an axial clamping force Fc results after decomposition thereof in only a very limited radial force component. The relatively small value of the radial force component is typically less than the friction at the contact surface between wedge <NUM> and expansion block <NUM>, resulting in a self-locking contact between the wedges <NUM> and the expansion block <NUM> in the connecting state. As a result, the wedges <NUM> remain in place even if the bolt <NUM> forming the actuator <NUM> for originally displacing the wedges <NUM> would be loosened or even removed. Although it is preferable that the bolt <NUM> remains tightened, this self-locking aspect prevents that the bolt <NUM> may experience stress fluctuations during use. In this way, a reliable and fail-safe assembly is provided.

The expansion block <NUM> has a surface <NUM> of which at least a portion <NUM> is a contact surface with the wedge <NUM> having an orientation corresponding with the inclined surface <NUM> of said wedge <NUM>. When the orientation of the contact surface and the inclined surface <NUM> are substantially equal, a reliable mating interface is obtained.

If only a portion <NUM> of the surface <NUM> is a contact surface, the contact surface may remain constant over a displacement range of the wedge <NUM>. If the wedge <NUM> that is shown on the right side in <FIG> is moved inward, the contact surface will not further increase once its front edge <NUM> passes edge <NUM> of portion <NUM>.

As can be best seen in <FIG> and <FIG>, the first <NUM> and the second member <NUM> are overlapping tubular members and the through holes <NUM>-<NUM> are radially aligned relative to the tubular members to define the channel <NUM> that is radially extending. The first <NUM> and second member <NUM> have respective longitudinal axes <NUM>, <NUM> that are at least parallel, and preferably coincide (<FIG>). In the prior art situation shown in <FIG>, the nut <NUM> had to be accessible with tools. However, according to the present invention, an airtight platform <NUM> may be provided without preventing access to the connection between the first <NUM> and second member <NUM>. To the contrary, it is exactly this airtight platform <NUM> that may provide a comfortable support for a user to readily place connectors <NUM> in respective channels <NUM>.

A symmetrical force transmission may be obtained if, according to the shown preferred embodiment, the second member <NUM> has a fork-shaped cross section with a main body <NUM> and two substantially parallel walls <NUM> that each comprises at least one through hole. In this embodiment, the first member <NUM> is arranged between the two walls <NUM> of the second member <NUM>, having the through holes <NUM>, <NUM>, and said through hole <NUM> of the first member <NUM> and the through holes <NUM>, <NUM> of the second member <NUM> are positioned to define the channel <NUM>. The arrows in <FIG> indicate how a clamping force Fc is symmetrically distributed.

The channel <NUM> preferably has an elongate cross section extending in a longitudinal direction of at least one of said first <NUM> and said second member <NUM>. Relative to channels having a circular shape, such an elongate cross sectional shape provides a relatively large amount of material between successive channels <NUM> if multiple channels <NUM> and connectors <NUM> are arranged along a circumference of the first <NUM> and the second member <NUM>.

In a second embodiment of the invention, the wedges <NUM>' are only inclined on one side relative to a displacement direction of said wedges <NUM>', i.e. the upper side in <FIG>. The other side of each wedge <NUM>', i.e. the lower side in <FIG>, is substantially parallel to the displacement direction of said wedge <NUM>'. Expansion block <NUM>' has two substantially parallel sides, which allows it to be placed in advance of the wedge <NUM>' and other expansion block <NUM> of the assembly. Expansion block <NUM>' also better facilitate de-assembly.

A third embodiment of the invention, wherein a single wedge <NUM> is applied, is shown in <FIG>.

A fourth embodiment of the invention is shown in <FIG>. This embodiment combines a single wedge <NUM> according to the embodiment of <FIG> with an expansion block <NUM>'that has two substantially parallel sides according to the embodiment of <FIG>.

In a (not shown) embodiment, the expansion blocks <NUM> may be connected by a flexible member enclosing the space between the expansion blocks <NUM> where the wedges <NUM> are arranged. In such an enclosed space, lubricant may be added.

According to a fifth embodiment of the invention that is shown in <FIG>, the second member <NUM> is embodied as an assembly rather than a one piece element. The fork-shaped cross section is defined by the assembly of the main body <NUM> and the two substantially parallel walls <NUM>. The walls <NUM> partially extend along, and are connected to, opposite sides of this main body <NUM>. The walls <NUM> may be defined by a plurality of plates <NUM>. The plates <NUM> may comprise though holes <NUM> to allow a pin <NUM> to pass through said plates <NUM> and through a corresponding through hole <NUM> in the main body <NUM> of the second member <NUM>. In the shown embodiment, a bolt <NUM> and washer <NUM> are being used to clamp the plates <NUM> that define the side walls <NUM> to the main body <NUM>. The bolts <NUM> are preferably arranged on an inside of the tubular first <NUM> and second member <NUM> to allow easy access. There is a modest pretension between the main body <NUM> and the plates <NUM> that are arranged on opposite sides thereof. Upon tightening of the connector <NUM> the dominant load transfer path however is through an applied tensile force through the plates <NUM> that is transferred into a shear force in the pin <NUM>. Connector <NUM>, both plates <NUM> on the inner and the outer side of the second member <NUM> and pin <NUM> all form part of the pretension load transfer path. Consequently, very low load fluctuations are felt by these components when an external load is applied at the connection. In a preferred embodiment, each connector <NUM> is associated with an inner plate <NUM> and one outer plate <NUM>. The clamping action of the fifth embodiment is similar to the other embodiments.

Relative to second member <NUM> comprising a one piece fork-shaped cross section, an assembly according to the fifth embodiment has several advantages and disadvantages.

A disadvantage of the fifth embodiment is the open structure, formed by the plurality of separate plates <NUM>. This may limit the main use of the fifth embodiment to so-called inair conditions where the construction is not continuously exposed to salt spray, as would be the case in the so-called splash zone. If used in offshore applications, the fifth embodiment is preferably applied well above the splash zone, i.e. well above sea level. However, if a sealing is used in-between the plurality of separate plates <NUM>, this fifth embodiment may also find its use at the splash zone or even below. The individual plates <NUM> may also be designed so that the plates overlap one another at the interface to adjacent plates including an overlap that seals the interface and prevents water and/or air penetration.

On the other hand, the fifth embodiment also comprises a number of important advantages.

Firstly, it is not required to make a solid ring, which typically requires a forging process that - in the required sizes - may only be applied by a limited number of highly specialized companies. The plates <NUM> and pins <NUM> according to the fifth embodiment can easily be produced by most metal work shops allowing the essential part of the connection to be produced by a large number of companies.

Secondly, once a solid ring is forged, forming of a groove therein is time intensive and causes a significant amount of steel to be removed in a machining step. The production of plates <NUM>, however, has the benefit that no material needs to be removed in between the plates <NUM> as is the case with a solid forging that requires machining to remove the groove.

Thirdly, large forged rings are heavy and bulky, resulting in logistic challenges and costs. Plates <NUM> and pins <NUM> are easy to transport, and - because they may be made by a large number and broader range of companies - transport may be minimized if local metal work shops produce these parts.

Fourthly, the forged and machined ring needs to be welded to the second member <NUM>, thereby possibly deforming the face <NUM> of said second member <NUM>. This deformation may result in so-called waviness and may have a negative effect on the structural integrity of the connection since the resulting gap needs to be closed using the pre-stress applied by the connectors <NUM>.

Finally, increased flexibility is obtained if a number of plates <NUM> is provided with additional functionality, such as alignment functionality.

In the shown embodiments, the first <NUM> and the second member <NUM> are members of an offshore construction, more in particular of an offshore wind turbine construction <NUM>. Each of the first <NUM> and the second member <NUM> may be an upright member of a monopile <NUM>. It is however explicitly mentioned that the invention is not limited to offshore use. Especially the fifth embodiment as described above is particularly suitable for use in onshore wind turbine applications. Onshore, the combination of the limited diameter of tubulars that can be transported over the road, the ever increasing tower height to catch stronger winds, and growing wind turbines power ratings results in connections between tubulars that are exposed to very high load levels. These load levels may even exceed typical L-flange load levels. In comparison with conventional L-flange connections, the absence of two welds between flanges and tubulars and the absence of the expensive flanges themselves makes the invention, and especially the fifth embodiment, a commercially attractive solution even at lower load levels.

Alternatively, one of the first <NUM> and the second member <NUM> may be a rotor blade <NUM> of a wind turbine <NUM>, and the other of the first <NUM> and the second member <NUM> may be arranged on a hub, and by example said first <NUM> or second member <NUM> may be arranged on a (not shown) pitch bearing attached to a hub. Such pitch bearing is known in the art and include ball- or roller bearings. The connection between bearing and blade may be established via either an inner or an outer raceway of the bearing as the case may be on a two-raceway bearing. <FIG> shows this connection C, as well as many other places where a similar assembly may be applied as connection C.

The method of assembling the first <NUM> and the second member <NUM> that each comprise at least one through hole <NUM>-<NUM> according to the invention, comprising the steps of:.

Although not shown, the method of assembling may be preceded by the step of positioning at least one of said first <NUM> and said second member <NUM> by hoisting thereof, wherein a (not shown) hoisting equipment engages at least one of the through holes <NUM>-<NUM> of said respective first <NUM> or second member <NUM>. An elongate member, preferably a rod, may be arranged through at least one of the through holes <NUM>-<NUM> to connect the respective first <NUM> or second member <NUM> to the hoisting equipment.

The same through holes <NUM>-<NUM> may also be used for engagement with an installation tool.

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. <FIG> shows an offshore wind turbine tower construction, but the assembly according to the invention is not limited to offshore use, nor to wind turbine applications alone.

It is remarked that in the description of the shown embodiments, the lower member is denoted as the first member <NUM>, and that the upper member is denoted as the second member <NUM>. The skilled person will understand that the lower member could be interpreted as a second member <NUM> and the upper member could be interpreted as a first member <NUM> within the scope of the invention.

Claim 1:
Assembly, comprising:
- a first member (<NUM>) and a second member (<NUM>) of a wind turbine construction (<NUM>), wherein;
- the second member (<NUM>) has a fork-shaped cross section with a main body (<NUM>) arranged between two substantially parallel walls (<NUM>) that each comprise at least one through hole (<NUM>, <NUM>);
- the first member (<NUM>) is arranged between the two walls (<NUM>) of the second member (<NUM>), having the through hole (<NUM>, <NUM>);
- wherein a through hole (<NUM>) of the first member (<NUM>) and the through holes (<NUM>, <NUM>) of the second member (<NUM>) define a channel (<NUM>); and
- further comprising a connector (<NUM>) that is axially insertable into said channel (<NUM>) to an end position and consecutively expandable radially relative to said channel (<NUM>), to connect the first (<NUM>) and second member (<NUM>) relative to each other,
characterized in that
- the connector (<NUM>), in an expanded state thereof, pushes the first member (<NUM>) in a radial direction relative to said channel (<NUM>) against a face (<NUM>) of the main body (<NUM>) of the second member (<NUM>) to define a clamping contact and thereby a pre-tensioned connection in said radial direction relative to said channel (<NUM>) between a face (<NUM>) of the first member (<NUM>) and the face (<NUM>) of the main body (<NUM>) of the second member (<NUM>).