Jacket structure for offshore constructions The invention relates to a jacket structure for offshore con ^¬ structions, particularly a jacket structure for offshore wind turbines, having a number of axially extending first profiles and a number of second profiles extending in an angle rela ^¬ tive to the first profiles, whereby at least one first and/or second profile is at least partially hollow.

Offshore constructions for diverse structures to be installed in the sea are usually necessary in particular for wind power plants, that is wind turbines and represent a constructive challenge as the respective structure has to be erected on the seabed by means of an appropriate foundation. Thereby, jacket structures are well-known foundations since they rep ^¬ resent a constructively simple and feasible principle. Be ^¬ sides, jacket structures are comparatively cost-effective.

Yet, the mechanical stability of the jacket structures may represent a problem, in particular in long-term regards.

In order to account for the harsh conditions in the sea, the mechanical stability of the jacket structures is construc ^¬ tively counteracted by increasing the wall thicknesses of the respective profiles, that is particularly buckling sensitive areas of the jacket structure. Hence, strengthening of the jacket structure usually leads to an increased use of mate- rial resulting in an increase of costs.

Thus, the known principles of improving the mechanical sta ^¬ bility of jacket structures for offshore constructions are considered as not satisfying.

Hence, it is the object of the invention to provide a jacket structure for offshore constructions with improved mechanical properties . This is achieved by a jacket structure for offshore construc ^¬ tions as described above, wherein the hollow space of the at least one first and/or second profile is at least partially filled with a cured material.

The present invention provides a novel principle for increas ^¬ ing the mechanical stability of jacket structures by filling or grouting the hollow spaces particularly of the highly loaded profiles or portions of respective profiles with the cured material. In such a manner, the mechanical properties of the jacket structure or respective profiles may be im ^¬ proved, that is the jacket structure or respective profiles may be strengthened in a simple manner. Thereby, it is pos- sible to reduce wall thickness in the respective filled por ^¬ tions of the jacket structure as the required mechanical properties are not only defined by the profiles themselves but additionally by means of the cured material inside the respective hollow spaces of the profiles contributing to an optimised design and material use of the jacket structure as a whole. This is advantageous particularly regarding the use of metals such as mainly steel for building the profiles since it also contributes to a comparatively cost-effective construction .

Likewise, eigen frequencies of the profiles are proactively adjustable or controllable by the defined filling of the re ^¬ spective hollow spaces with the cured material. Thereby, critical collisions of eigen frequencies of different compo- nents of the offshore construction are avoided, that is with regard to the exemplary case of a wind turbine the superposi ^¬ tion of eigen frequencies or vibrations originating from the turbine blades and moving towards the jacket structure may be reduced .

Moreover, filling of the hollow spaces of the profiles with the cured material, which is advantageously not jeopardised by corrosive effects, leads to an improved corrosion resis- tance of the jacket structure or the respective filled pro ^¬ files.

A profile may be provided with a hollow space extending along its entire length or merely parts of it, that is in sections. Accordingly, the profiles may be deemed as fully or partially hollow pieces having a core or internal portions filled with the cured material. It is possible, that the entire jacket structure, that is every profile is at least partially or entirely filled with the cured material. Alternatively, only certain parts, that is especially buckling sensitive areas of the jacket struc ^¬ ture such as comparatively long first and/or second profiles or joints of first and/or second profiles for instance are filled with the cured material. Hence, the inventive jacket structure may range from only a part of a first or second profile being filled with the cured material to the entire jacket structure, that is every profile being completely filled with the cured material.

Cured or curable material in terms of the present invention relates to all types of materials which may undergo or have undergone a physical and/or chemical transformation from a liquid or viscous state into a solid or cured state under de ^¬ fined conditions.

It is of advantage, that communicating hollow spaces of at least two adjacently disposed first and/or second profiles are filled with the cured material. This preferred embodi ^¬ ment provides another advantageous aspect of the invention since the cured material filled in the respective hollow spaces of the abutting profiles may also serve as a connect ^¬ ing means and/or increasing the stability of joints between adjacently disposed profiles as the cured material extends between the respective communicating hollow spaces of the re ^¬ spective profiles. Of course, the joints of more than two first or second profiles may be strengthened in the same man- ner if the communicating hollow spaces extend through more than two respective profiles.

Generally, the first or second profiles may be connected by means of bolted-j oints , welded-j oints , plug connections or the like. Yet, it is possible that the cured material may serve as the only connecting means for the respective aligned profiles, that is no other connecting means than the cured material may be necessary in certain cases.

The connecting portions of the first profiles with the re ^¬ spective second profiles, that is in particular node portions of the jacket structure, are highly exposed to buckling.

Hence, it is advisable, when the first profiles are filled with the cured material in respective connecting portions with second profiles. In such a manner, these comparatively highly loaded, buckling sensitive portions may be mechani ^¬ cally strengthened. Favourably, the first and/or second profiles may be provided with a connecting portion for connecting with at least one further first or second profile. The connecting portions support a quick and secure attachment or alignment of abut ^¬ ting first or second profiles and therefore, are of advantage in regard to the erection or assembly of the entire jacket structure .

Thereby, the connecting portions are preferably provided at respective free endings of the first and/or second profiles. Yet, other locations with respect to the respective outer and/or inner diameter of the profiles are thinkable as well.

The connecting portions of the first and/or second profiles may build a plug-connection in such a manner that the respec- tive connecting portions at least partially overlap. Plug- connections represent a simple connecting principle, whereby a connection of two abutting profiles is achieved by one pro ^¬ file engaging the other, thereby building an overlapping re- gion. In dependence of the length of the overlap a plug- connection may offer a certain mechanical stability as well.

Thereby, an annular space may be provided by the respective connecting portions in the region of the overlap, whereby the annular space is filled with the cured material. In such a manner, the cured material serves to strengthen the mechani ^¬ cal stability of the plug-connection since it bonds the re ^¬ spective connected profiles together, that is the respective connecting portions of the profiles stick firmly to each other by means of the cured material. In order to increase the strength of the bond, the respective surfaces of the con ^¬ necting portions may be provided with a certain roughness or any other, particularly three-dimensional structure.

There are basically two ways of building the annular space. The annular space may be built by a cross-sectionally widened collar-like portion of a first or second profile, whereby a respective adjacently disposed profile at least partially en- gages in the collar-like portion. Since the collar-like por ^¬ tion has a greater cross-section than the engaging profile the annular space is accordingly provided between the inner diameter of the collar-like portion and the outer diameter of the respective engaging profile. Likewise, the collar-like portion may be perceived as a bulge or winged flange in which the cured material may be easily filled. Additionally, pos ^¬ sible hollow spaces in the inside of the respective profiles may also be filled with the cured material. Alternatively, the annular space may be built by a cross- sectionally tapered portion of a first or second profile, whereby a respective adjacently disposed profile at least partially encompasses the tapered portion. In this case, the annular space extends in the inside of the respective pro- files of the jacket structure, that is it radially extends between the respective inner diameter and the tapered outer diameter of the respective connecting portions of the adja ^¬ cently disposed profiles. Likewise, only the annular space may be filled with the cured material or additionally, hollow spaces of the respective profiles may be filled with the cured material as well. Additionally or alternatively, the connecting portions may be provided with flange-like portions, whereby the flange-like portions comprise at least one bore for accommodating con ^¬ necting means, particularly bolts. In such a manner, respective aligned profiles may be connected by means of the bolts, particularly long bolts since the bolts may not only pene ^¬ trate through respective bores of directly abutting profiles, but may also extend through the entire length of a number of profiles, so that one bolt may firmly hold more than two aligned profiles together. The bores and bolts may be pro- vided with corresponding threads. The flange-like portions may extend in radial inward or outward direction.

Since the cured material contributes to the mechanical prop ^¬ erties of the respective profile, it is possible that the filled portions of the first and/or second profiles have a reduced wall thickness in comparision to the non-filled por ^¬ tions of the first and/or second profiles. Hence, the me ^¬ chanical properties of the respective profiles are not low ^¬ ered although the profiles comprise a reduction of wall thickness since the cured material serves as a mechanical stabilitsation of the respective profiles.

Favourably, the cured material is a curable cement-based ma ^¬ terial, particularly mortar or concrete. Cement-based mate- rials are easy to handle and transport and therefore may be easily filled into the respective hollow spaces of the pro ^¬ files. Curing or hardening of cement-based materials is a well-known and controllable process so that hardening is achievable with a high degree of reproduction. All types of cement-based materials or cements may be used. Further, it is of advantage, that the cured cement-based materials do not encounter any corrosive reactions with the highly corrosive conditions of the sea. Generally, other materials such as filled- or non-filled polymeric resins for instance may be applicable as well.

It is thinkable, that the cured material comprises reinforce- ment materials, particularly metal rods or metal rebars . In such a manner, particularly plain or deformed steel bars, steel wires and/or steel fabric or mesh may improve the me ^¬ chanical behaviour of the cured material particularly regard ^¬ ing its tension strength. The named metal components may comprise a defined coating or may be galvanised in order to increase their corrosion resistance. Of course other metals than iron-based metals are also applicable.

Aside, the invention relates to a wind turbine comprising a jacket structure as described above.

In the following the invention is described in detail as ref ^¬ erence is made to the figures, whereby: Fig. 1 shows a cut-out view of an inventive jacket struc- according to a first exemplary embodiment invention ;

Fig. 2 shows the detail of fig. 1 ;

Fig. 3 shows a cut-out view of an inventive jacket struc ^¬ ture according to a second exemplary embodiment of the invention;

Fig. 4 shows a cut-out view of an inventive jacket struc ^¬ ture according to a third exemplary embodiment of the invention;

Fig. 5 shows a cut-out view of an inventive jacket struc ^¬ ture according to a fourth exemplary embodiment of the invention; Fig. 6 shows a cut-out view of an inventive jacket struc ^¬ ture according to a fifth exemplary embodiment of the invention; and Fig. 7 shows a cut-out view of an inventive jacket struc ^¬ ture according to a sixth exemplary embodiment of the invention.

Fig. 1 shows a cut-out view of an inventive jacket structure 1 according to a first exemplary embodiment of the invention. The jacket structure 1 is preferably used as a foundation structure for an offshore wind turbine and essentially com ^¬ prises a number of axially extending first profiles 2 and a number of second profiles 3 extending in an angle a relative to the first profiles 2. The first and second profiles 2, 3 are preferably made of a stainless steel material.

According to the embodiment shown in the figures 1, 2 the second profiles 3 are built as hollow or tube-like pieces, that is they define a hollow space 4 within their inside. In order to increase the mechanical properties of the second profiles 3, particularly in buckling sensitive areas, the hollow spaces 4 are filled or grouted with a cured cement- based material 5, that is mortar or concrete for instance. As is discernible, the hollow spaces 4 may communicate with each other so that the cement-based material 5 is filled within all second profiles 3 building a cross.

Filling of the hollow spaces 4 of the second profiles 3 re- suits in a number of advantages since it improves the me ^¬ chanical strength of the respective second profiles 3 and consequently, the jacket structure 1 as a whole. Further, wall thickness can be reduced in the respective filled por ^¬ tions of the second profiles 3 since the cement-based mate- rial 5 contributes to the mechanical properties of the re ^¬ spective second profiles 3. Hence, the material use may be reduced which contributes to a cost-effective, yet mechani ^¬ cally stable constructive design of the jacket structure 1. Likewise, the undesired and dangerous superposition of eigen frequencies or vibrations propagating from other parts of the wind turbine like the rotor blades (not shown) for instance to the jacket structure 1 may be avoided or at least reduced. Moreover, the cement-based material 5 may serve as a certain corrosion protection since cement-based materials do not en ^¬ counter any corrosive attacks. Of course, one or more first profiles 2 could be filled with a cement-based material 5 in the same manner if they are pro ^¬ vided as hollow or tube-like pieces which will be shown later . As a result, by providing the jacket structure 1 with hollow first or second profiles 2, 3 a tailor-made mechanical behav ^¬ iour of the jacket structure 1 is achievable, since particu ^¬ larly highly loaded components or areas of the jacket struc ^¬ ture 1 may be proactively and directedly filled or grouted with a mechanical reinforcement, that is the cement-based ma ^¬ terial 5. Thereby, the cured cement-based material 5 is in ^¬ ventively considered as a construction element directly from the beginning of the planning of the jacket structure 1 and thus, represents an essential component of the jacket struc- ture 1 particularly regarding its mechanical behaviour.

Fig. 3 shows a cut-out view of an inventive jacket structure 1 according to a second exemplary embodiment of the inven ^¬ tion. In this embodiment the first profiles 2 are partially hollow, that is they define a hollow space 4 filled with the cement-based material 5 in the connecting portions with the second profiles 3, that is the areas of contact between the first profiles 2 and second profiles 3. These portions are known as highly buckling sensitive areas of the jacket struc- ture 1. Hence, these highly loaded portions of the first profiles 2 are stabilised and strengthened due to the filling with the cement-based material 5. Fig. 4 shows a cut-out view of an inventive jacket structure 1 according to a third exemplary embodiment of the invention. This embodiment relates to another positive aspect of grout ^¬ ing communicating hollow spaces 4 of adjacently disposed pro- files such as first profiles 2 for instance regarding fig. 4. The first profiles 2 are provided with connecting portions for connecting with further first profiles 2 at their free endings. The connecting portions may support pre-alignment of the first profiles 2 and may also offer a certain mechani- cal joint since they provide a plug-connection of the axially abutting first profiles 2 in such a manner that the respec ^¬ tive connecting portions at least partially overlap.

As is discernible from fig. 4, an annular space 6 is provided by the respective connecting portions in the region of the overlap. Thereby, the annular space 6 is filled with the ce ^¬ ment-based material 5 which leads to a strengthening of the connection of the respective adjacently disposed first pro ^¬ file 2, 2 ' . The annular space 6 is built between a cross- sectionally tapered portion 7 of the lower first profile 2 and the adjacently disposed upper first profiles 2', which encompasses the tapered portion 7 of the lower first profiles 2. In other words, the respective connecting portions of the first profiles 2, 2 ' differ in their diameter since the con- necting portion of the lower first profile 2 is tapered. It has a reduced cross-section, whereas the connecting portion of the upper first profile 2 ' has a normal diameter or cross- section, that is the annular space 6 is built between the in ^¬ ner diameter of the connecting portion of the upper first profile 2 ' and the outer diameter of the connecting portion of the lower first profile 2. Of course, the remainder of the communicating hollow spaces 4, 4' of the first profiles 2, 2 ' may also be grouted with the cement-based material 5. The same principle is applicable for respective second pro- files 3 as well.

Fig. 5 shows a cut-out view of an inventive jacket structure 1 according to a fourth exemplary embodiment of the inven- tion. The embodiment according to fig. 5 depicts a like principle to the one in fig. 4, whereby the essential differ ^¬ ence lies in the location of the annular space 6. According to fig. 5, the annular space 6 is built by a cross- sectionally widened collar-like portion 8 of the lower first profile 2, whereby the adjacently disposed upper first pro ^¬ file 2 ' at least partially engages in the collar-like portion 8. Likewise, the annular space 6 is filled with the cement- based material 5 so that the first profiles 2, 2 ' are firmly held in place and relation to each other.

As is further discernible, the hollow spaces 4, 4' of the abutting first profiles 2, 2 ' do not communicate with each other (indicated by separation line 9) . Yet, the respective hollow spaces 4, 4' are completely filled with the cement- based material 5 in each case.

Fig. 6 shows a cut-out view of an inventive jacket structure 1 according to a fifth exemplary embodiment of the invention. In this case, the adjacently disposed first profiles 2 are connected by means of a bolted connection. Therefore, the first profiles 2 are provided with radially inwardly extend ^¬ ing flanges 10 each comprising bores, whereby long-bolts 11 penetrate through the bores. As can be seen from fig. 6, one bolt 11 may extend from a flange 10' of an upper first pro ^¬ file 2 ' to a flange 10 of a lower first profile 2, thereby extending through all flanges of respective profiles in be ^¬ tween the upper and lower first profiles 2', 2. Thus, only one bolt 10 may stably connect more than two adjacently dis- posed first profiles 2. Of course one bolt 11 may also con ^¬ nect only directly abutting first profiles 2. The bolt 11 is fastened by means of appropriate screw nuts 12 or the like. Bores and bolts 11 may be provided with threads. Again, the communicating hollow spaces 4 of the respective first profiles 2 are filled with the cement-based material 5 in order to increase the strength of the connection of the first profiles 2. Of course, the principle according to the embodiment shown in fig. 6 also applies to second profiles 3.

Fig. 7 shows a cut-out view of an inventive jacket structure 1 according to a sixth exemplary embodiment of the invention. The embodiment according to fig. 7 indicates, that all pro ^¬ files of the jacket structure 1, that is all first profiles 2 and second profiles 3 may be completely filled or grouted with the cement-based material 5. Moreover, regarding the hollow spaces 4 of the first profiles 2, reinforcement means such as metal, that is particularly steel rods or rebars 13 may be provided. The reinforcement means increase the me ^¬ chanical stability of the cement-based material 5 in particu ^¬ lar in regard of tensile forces. The metal reinforcement may comprise different shapes, that is may comprise any kind of shape ranging from simple rods to complex three-dimensional structures such as fabrics or meshes.

The inventive jacket structure 1 may be erected essentially in two different ways. On the one hand, the respective hol ^¬ low spaces 4 of the first and/or second profiles 2, 3 are filled or grouted with the curable liquid or viscous, par ^¬ ticularly cement-based material 5 in a first step. Subse ^¬ quently, curing or setting of the cement-based material 5 takes place as a second step. In a third step, the first and/or second profiles 2, 3 including the cured cement-based material 5 are placed on the seabed, that is respective foun ^¬ dation piles or the like for instance. Thereon, assembling of the remainder of the jacket structure 1 is performed. Ac- cording to this embodiment, first and second profiles 2, 3 already containing the cured cement-based material 5 within their inside, that is the respective hollow spaces 4 are as ^¬ sembled to erect the jacket structure 1. On the other hand, the erection of the jacket structure 1 may be accomplished by initially non-filled first and second pro ^¬ files 2, 3, that is the respective hollow spaces 4 do not contain any cured or cement-based material 5 while assembling the first and second profiles 2, 3 in a first step. In this embodiment, the second step comprises filling of the respec ^¬ tive hollow spaces 4 directly after erection of the jacket structure 1, that is after proper mounting or assembling of the first and second profiles 2, 3, with the curable liquid or viscous material, which cures or sets in a subsequent third step.

Both alternatives relate to the direct assembly process of the jacket structure 1 and merely differ in the point at which the respective hollow spaces 4 of the respective first and/or second profiles 2, 3 are being filled with the cur ^¬ able, particularly cement-based material 5 or at which curing of the curable material takes place. According to the inven- tion, the filling of the hollow spaces 4 of the respective first and/or second profiles 2, 3 with the curable material which is to be cured before or after installation of the re ^¬ spective first and/or second profiles 2, 3 is proactively em ^¬ bedded in the constructive design of the jacket structure 1. Thus, the inventive jacket structure 1 or its manufacturing process distinguishes from any retrofitting or renovation activities .