Bridge span comprising a wind turbine rotor blade

Abstract

Bridge span comprising: a first girder that is formed by at least a part of a first wind turbine rotor blade, wherein the at least a part of the first wind turbine rotor blade comprises, as seen along the length thereof, a proximal section, a distal section and a central section, wherein the central section is arranged in between the proximal and distal sections, and wherein the proximal section has a higher bending stiffness compared to the distal section; a bridge deck structure that is arranged for supporting traffic thereon, wherein said bridge deck structure extends in substantially a same longitudinal direction as the at least a part of the first wind turbine rotor blade and is connected to the at least a part of the first wind turbine rotor blade; and a plurality of supports that support the at least a part of the first wind turbine rotor blade at at least three support locations along its length; characterized in that a first support location is arranged at the proximal section, a second support location is arranged at the central section and a third support location is arranged at the distal section; and wherein a distance between the first and the second support locations is larger than a distance between the second and third support locations.

Description

[0001] Bridge span comprising a wind turbine rotor blade

[0002] The current invention relates to a bridge span, in particular comprising a first girder that is formed by at least a part of a first wind turbine rotor blade, and a bridge structure comprising a plurality of said bridge spans.

[0003] Since the initial developments of wind energy in the 1970’s, an increasing number of wind turbines have been installed for generating ever larger amounts of renewable energy. Many wind turbines that were installed in the 1990’s and early 21st century are at the end of their lifetime and are being replaced by newer and larger types of wind turbines. Many of the components of wind turbines, such as the steel towers and frame structures of the nacelles can be easily recycled. The rotor blades, which have typically been made from fibre-reinforced polymer (FRP) composite materials, comprising glass fibres and resin, are however difficult to recycle, such that they are either to be processed in waste incinerators or stored in large “blade graveyards”. In recent years many ways of repurposing the rotor blades, or parts of the rotor blades, have been developed, which vary from children’s playgrounds, canopy’s and even form the girders for pedestrian bridges.

[0004] Such a bridge is for instance disclosed in patent publication GB2588990A, wherein a bridge span is formed by arranging a bridge deck that is connected to a wind turbine rotor blade, such that the wind turbine rotor blade forms the girder of the bridge span. The spans of these pedestrian bridges are, however, limited due to the requirements with respect to the eigenfrequencies of the bridge. In order to prevent the bridges from resonating due to the thereover passing pedestrians that provide for an average vertical excitation up to around 3 Hz, it is typically required that the eigenfrequency is above 5 Hz, unless the accelerations of the bridge are sufficiently low. Due to the fact that the rotor blades are stiffest in a first section near the blade root and relatively flexible towards the blade tip, typically only a limited part of the blade length can be effectively used, such that relatively large parts of the rotor blades cannot be repurposed as girders.

[0005] It is a goal of the current invention to provide for a bridge span comprising a first girder that is formed by at least a part of a first wind turbine rotor blade wherein an increased length of span can be obtained, wherein at least some of the before mentioned problems are at least partly alleviated.

[0006] This goal is achieved by a first aspect of the current invention that relates to a bridge span comprising: a first girder that is formed by at least a part of a first wind turbine rotor blade, wherein the at least a part of the first wind turbine rotor blade comprises, as seen along the length thereof, a proximal section, a distal section and a central section, wherein the central section is arranged in between the proximal and distal sections, and wherein the proximal section has a higher bending stiffness compared to the distal section; a bridge deck structure that is arranged for supporting traffic thereon, wherein said bridge deck structure extends in substantially a same longitudinal direction as the at least a part of the first wind turbine rotor blade and is connected to the at least a part of the first wind turbine rotor blade; and a plurality of supports that support the at least a part of the first wind turbine rotor blade at at least three support locations along its length; characterized in that a first support location is arranged at the proximal section, a second support location is arranged at the central section and a third support location is arranged at the distal section; and wherein a distance between the first and the second support locations is larger than a distance between the second and third support locations.

[0007] Due to the decreasing stiffness of the wind turbine rotor blades over the length of the blade from the blade root section to the bade tip, rotor blade bridges according to the prior art typically only employ the stiffest region (i.e. having the larger cross-section) of the rotor blade, in order to be able to get a bridge span satisfying the design requirements, in particular the eigenfrequency requirement. The remaining, less stiff, part of the rotor blade is typically cut-off and discarded. The inventor has, surprisingly, found that by using the less stiff part of the wind turbine rotor blade and arranging the third support location, a further stiffening effect of the wind turbine rotor blade can be obtained, allowing to increase the primary span of the bridge span, wherein the primary span extends between the first and second support locations.

[0008] Hence, the bridge span according to the first aspect thereby differs from the bridge spans according to the prior art in that the wind turbine rotor blade, or the part of the wind turbine rotor blade, that is arranged as the girder is supported at at least three points, as specified above, along the length of the wind turbine rotor blade. The first, stiffer, part of the wind turbine rotor blade, that is defined as being arranged in between the first and second support locations, can thereby define the primary span of the bridge. The second, more flexible part of the wind turbine rotor blade, that is defined as being arranged in between the second and third support locations, thereby serves as an auxiliary support part for the first, stiffer part. In fact, as the distance between the second and third supports is shorter than the distance between the first and second supports, the second part of the wind turbine rotor blade has a stiffening effect on the first part of the rotor blade, as it effectively acts as an additional (rotational) spring at the second support. This stiffening effect thereby leads to, effectively, an increase in the eigenfrequency of the bridge span, such that a larger primary span may be obtained when compared to arranging the rotor blade on only two spaced apart supports as in the prior art.

[0009] It is noted that, as wind turbine rotor blades are formed to have a certain shape, bend and twist, they are typically not fully straight. As such, the longitudinal direction of the bridge deck structure, that is connected to (i .e. supported by) the at least a part of the wind turbine rotor blade (i .e. a full and / or partial wind turbine rotor blade), will typically not be exactly parallel to the wind turbine rotor blade along its full length, nonetheless, they do extend in substantially the same longitudinal direction (i.e. parallel ±5°). In practice, the outer distal end of the wind turbine rotor blade (i.e. the blade tip) is highly flexible, in particular in the flap-wise direction, such that, in case a partial rotor blade is used, the outer distal end (blade tip) is typically the part that is removed from the rotor blade, whereas the blade root (i.e. the part that is normally used for connecting the rotor blade to the rotor hub of the wind turbine) is typically retained as this is a stiff part of the blade.

[0010] It is preferred that the distance between the second and third support locations is in the range of 10% - 90%, preferably 30% - 80%, more preferably 40% - 70%, most preferably 50% - 60%, of the distance between the first and second support locations. Due to the continuously decreasing stiffness of the wind turbine rotor blade, both in flap-wise as in edge-wise direction, over the length of the blade, as seen from the blade root, or seen from the position of maximum distance between the leading and trailing edge, towards the blade tip, the ratio between the respective distances is dependent on the specific rotor blade used (and / or the respective part of the rotor blade that is used), however, a smaller ratio typically leads to an increased added stiffness effect on the primary span, such that the length of the primary span may be further increased. The limit case, obviously being a clamped connection of the wind turbine rotor blade at the second support. However, the smaller ratio also leads to higher forces acting on the supports, and thereby leading to higher forces acting on the rotor blade at the support locations. As the rotor blade itself is a hollow and relatively thin walled structure, it may not be able to cope with too high forces, such that the optimal ratio will typically not lead to a too small distance between the second and third support locations.

[0011] Preferably, the at least a part of the first wind turbine rotor blade comprises a blade root section that is arranged for connecting it to a rotor hub of a wind turbine; and wherein the first support location is at the blade root section of the at least a part of the first wind turbine rotor blade. As was described above, the blade root section of a wind turbine rotor blade is a section having a high stiffness that is arranged for being able to transfer relatively high forces and moments to the rotor hub, such that this section is highly beneficial to reuse in the bridge girder.

[0012] Although the bridge span may comprise only a first girder that is, for instance, arranged underneath, trough, or above the bridge deck structure in a substantially central position of the bridge deck structure, it is preferred that the bridge span comprises a second girder that is formed by at least a part of a second wind turbine rotor blade and wherein said bridge deck structure is connected to the at least a part of the second wind turbine rotor blade. The second girder, in the form of at least a part of a second wind turbine rotor blade allows to arrange the bridge deck structure such that it extends in between the respective wind turbine rotor blades (or the respective parts thereof), such that the overall height of a bridge comprising such a bridge span may be reduced, when compared to arranging the bridge deck structure on top of the at least a part of the first wind turbine rotor blade. Nonetheless, if the width, rather than the height of the bridge is the limiting factor, the bridge deck structure may also be arranged on top of the respective wind turbine rotor blades (or the respective parts thereof). It is further noted that the bridge deck structure may be substantially horizontally arranged in a cross-section perpendicular to the longitudinal direction.

[0013] It is then preferred that the at least a part of the second wind turbine rotor blade is oriented to be substantially in a same direction and, preferably, spaced apart from the at least a part of the first wind turbine rotor blade and, preferably, wherein the blade root sections of the at least a part of the first wind turbine rotor blade and the at least a part of the second wind turbine rotor blade are arranged at a same longitudinal end of the bridge span, such that respective support locations on the at least a part of the first wind turbine rotor blade correspond to respective support locations on the at least a part of the second wind turbine rotor blade. Hereby, the bridge deck structure is easily mounted in between the respective wind turbine rotor blades, such that the hereabove described benefits are obtainable.

[0014] Preferably, the bridge deck structure is connected to the at least a part of the first wind turbine rotor blade, and preferably also the at least a part of the second wind turbine rotor blade, at a plurality of connection points that are spaced apart the length of the at least a part of the respective wind turbine rotor blade; preferably wherein said connection points are spaced apart no further than 8 meters, preferably no further than 5 meters, more preferably no further than 3 meters, most preferably no further than 2 meters. The bridge deck structure and wind turbine rotor blade(s) are thereby connected over their lengths, such that a favourable transfer of forces is obtained, and such that a stiff overall structure is obtained.

[0015] It is preferred that the connection points are formed in the spar cap of the at least a part of the first wind turbine rotor blade, and preferably also in the spar cap of the at least a part of the second wind turbine rotor blade. The spar cap is relatively stiff, thick and solid part of the rotor blade such that is able to bear and transfer the connection forces, which are typically point-forces acting at a discrete location and / or relatively small area, between the deck structure and wind turbine rotor blade(s).

[0016] Preferably, the bridge deck structure is a plate-like structure, that is preferably made from steel, crosslaminated timber (CLT) or fibre-reinforced polymer (FRP) composite. A plate-like structure is beneficial as it increases the horizontal stiffness of the bridge and allows that the deck structure then transfers inplane shear forces, which is not the case when perpendicular beams are used in the bridge deck structure as a deck support. Steel, cross-laminated timber (CLT) or fibre-reinforced polymer (FRP) composite are relatively lightweight and stiff materials, such that a bridge deck structure having sufficient capacity is achieved, while still being relatively lightweight. A fibre-reinforced polymer composite deck may for instance be formed by arranging a foam based core layer that is arranged between upper an lower layers of FRP material. For example, a more traditional concrete-based bridge deck would add too much mass, such that the eigenfrequency requirements for the bridge could potentially not be met, or could only be met at the cost of reducing the length of the primary span. In a preferred embodiment, the bridge deck structure is shaped to have a pre-camber, preferably along the longitudinal direction. Another criterium that has to be met is a maximum downward deflection that the bridge span may have. By arranging the bridge deck with a pre-camber (i.e. a pre-constructed upward deflection), the structure may be loaded with higher loads before the maximum downward deflection is reached, such that the bridge span may also support heavier traffic, such as motorized vehicles (e g. trucks, cars, vans, etc). Hence, said bridge span is preferably a foot- and / or bicycle bridge span, or wherein said bridge span is a road bridge span for supporting motorized vehicles Additionally, or alternatively, the bridge deck structure may have a pre-camber in a transverse direction, i.e. in the crosssection perpendicular to the longitudinal direction. In general, pre-camber is also beneficial for draining water from the bridge span.

[0017] Preferably, at least one support of the plurality of supports comprises a load spreading member that is arranged for transferring support forces over a predefined surface area of the outer surface of the at least a part of the wind turbine rotor blade at the respective support location, in particular wherein an inner side of the load spreading member is shaped to correspond to the outer surface and / or comprises a channelshaped section having a substantially U- or J-shaped cross-section for receiving the outer surface therein. Such a load spreading member may be formed from steel, concrete or a fibre-reinforced composite material (or a combination of these) and can thereby provide for a larger area of contact between the support and the wind turbine rotor blade, such that peak forces on the relatively thin wall of the wind turbine rotor blade are prevented. The load spreading members are therefore preferable formed to correspond to the outer shape of the wind turbine rotor blade at the respective support location, such that a close fit between the support and the wind turbine rotor blade is obtained that enable an even further improved transfer of forces between the rotor blade and the support.

[0018] In a preferred embodiment, the badge span is formed as a double bridge span having the primary span that extends between the first and second support locations and a secondary span that extends between the second and third support locations. The secondary span may thereby serve as the approach span, whereas the primary span can extend, for instance over one direction of a two-line highway or canal.

[0019] In an alternative preferred embodiment, said bridge span is formed as a single bridge span having a single span that extends between the first and second support locations and wherein said second and third support locations are supported by a single footing structure and / or abutment. This enables to obtain a single span bridge having a larger primary span than would be obtainable using only two support locations along the length of the rotor blade, as was explained above.

[0020] In a preferred embodiment, the distance between the first and third support locations is in the range of 50

[0021] - 95%, preferably 55% - 85%, more preferably 60% - 80%, most preferably 70% - 75%, of the length of the full wind turbine rotor blade. Hereby, more of the wind turbine rotor blade is repurposed when compared to the bridges according to the prior art.

[0022] In a second aspect, the disclosure relates to a bridge structure comprising a first and second bridge span according to any of the preceding embodiments, wherein the first bridge span is oriented in a first direction and the second bridge span is oriented in a second, opposite, direction; wherein the blade root sections of the first and second bridge spans face each other; and wherein the bridge deck structures of the first and second span align for forming at least one continuing traffic lane over the respective bridge deck structures. Hereby, a traffic bridge can, for instance, be obtained that is able to span two-directional double-laned highways using end-of-life blades of approximately 35 - 40 meter, as a primary span per bridge span of 17 meters is obtainable, such that this allows to span the two lanes and an emergency lane using the primary span. Approximately 20 to 25 years ago, 35 - 40 meter blades were the state-of-art, such that most of currently discarded blades fall in the range. Combined with the fact that a large portion of the highways in Europe comprise two main lanes per direction, the discarded blades can be used for bridging over a large part of these highways.

[0023] It is preferred that the blade root sections of the first and second bridge spans that directly face each other are not directly structurally interconnected. Even though the blade roots are typically comprised with a ring of bolt holes directly formed in the blade root section for allowing bolts to be mounted therein, coupling a pair of blade roots requires adding a relatively complex, and costly, interface, while it does not necessarily lead to an increased length of the primary span. It is further noted, that the respective bridge deck structures of the first and second bridge spans are, preferably, also not directly structural interconnected to each other. A gap between the respective bridge deck structures may be covered and / or filled with a compressible seal to prevent water and chemicals from entering such gap, while still allowing for movement of the individual bridge.

[0024] The present disclosure is further illustrated by the following figures, which show exemplifying embodiments of the bridge span according to the disclosure, and are not intended to limit the scope of the disclosure in any way, wherein:

[0025] - Figure 1 shows a schematical view of an embodiment of a bridge structure according to the second aspect.

[0026] - Figure 2A shows the structural model of the bridge structure of figure 1.

[0027] - Figure 2B shows an underlying structural model of the primary span for explaining the additional stiffness that the secondary span provides.

[0028] - Figure 3 schematically shows the eigenmodes for various single span and double span configurations.

[0029] - Figure 4 shows the three-dimensional mode shape corresponding to the critical eigenfrequency of the bridge span according to the disclosure. - Figure 5 shows, in a three-dimensional cross-sectional perspective view, a bridge deck structure that is connected to one of the wind turbine rotor blades forming a girder of the bridge span.

[0030] - Figure 6 shows, in a three-dimensional cross-sectional perspective view, a support that comprises an embodiment of a load spreading member for supporting the wind turbine rotor blade forming a girder of the bridge span.

[0031] - Figures 7A - 7C show, in three-dimensional cross-sectional perspective views, various embodiments of load spreading members.

[0032] Figure 1 shows a frontal view of a bridge structure 1 comprising a pair of bridge spans 2,3 that, as seen in the side view, can be considered as substantially mirror-symmetric with respect to mirror-line M (although it is noted that the wind turbine rotor blades 10 themselves cannot be physically mirrored). The bridge structure 1 is seen to extend over two-directional double-laned highway 100 that comprises a total of four lanes arranged in a pair of double lanes per direction, wherein each double lane 101 is arranged with an emergency lane 102 to the side. In the central reservation a central pier 43 is arranged, whereas to the sides of the emergency lanes 102 an additional of set of piers 42 is provided. A primary span 21 , 31 of each bridge span 2,3 extends between the central pier 43 and the pier 42, its length being indicated by Li . A secondary span of each bridge span 2,3 extends between the pier 42 and the abutment 41, its length being indicated by L2.

[0033] A respective bridge span 2,3 is seen to comprise a (partial) wind turbine rotor blade 10, whose blade root section 11 is supported, at a first support location 51 on wind turbine rotor blade 10, on the central pier 43. The wind turbine rotor blade 10 further comprises a leading edge 13 that is, in the current embodiment, directed in a downward direction (i.e. in the direction of gravity). At the opposite side of the wind turbine rotor blade 10 the trailing edge 14 is comprised, wherein a maximum edge height 12 of the blade is at a position of maximum distance between the leading and trailing edges. It is further noted that the shape of wind turbine rotor blades may vary between designs and manufactures, but can in general be considered known to the skilled person, although a special emphasize is put to the fact that a rotor blade becomes more slender towards the blade tip (i.e. the longitudinal outer end at the opposite end of the blade root section 11), such that the stiffness (in both edge-wise and flap-wise direction) will typically decrease (for flap-wise from the blade root section 11, for edge-wise from the maximum edge height 12) towards the blade tip.

[0034] A wind turbine rotor blade 10 forms a first girder of each bridge span 2,3 and is supported at (at least) three locations along the length of the blade. A first support location 51, as was discussed above, is arranged at the blade root section 11 that defines the proximal end of the wind turbine rotor blade 10 and is commonly used for interconnecting the wind turbine rotor blade 10 to a rotor hub of a wind turbine. A second support location 52 is arranged at a distance Li of the first support location 51, such that the therein between arranged part of the bridge span 2,3 is the primary span 21 ,31 of the respective bridge span. At the second support location 52 the wind turbine rotor blade 10 is supported, in the current embodiment, on pier 42. At a distance of L2of the second support location 52 along the length of the wind turbine rotor blade 10, a third support location 53 is arranged that is, in the current embodiment, supported on an abutment 41. The part of the bridge span 2,3 that extends between the second and third support locations 52, 53 forms, in the current embodiment, the secondary span 22, 32. The sum of the respective lengths Li, L2of the primary span 21,31 and secondary span 22,32 is defined as the total length LT, which is substantially equal to the distance between the first and third support locations 51, 53, if one neglects the size of the supports. It is furthermore noted that, in the shown embodiment, the blade root sections 11 of the respective wind turbine rotor blades 10 that are arranged in line with each other are not directly structurally interconnected, as was explained above.

[0035] Figure 2A shows a simplified abstract view of the bridge structure 1, and a visualization of the underlying structural model 1’. The abutment 41 is modelled as a hinged-support, whereas the respective piers 42, 43 are model as roller-supports. Typically, the primary span 21, 31 is the most important of the respective spans, as this defines the width of the primary clearance underneath the bridge span 2,3. Due to the decreasing stiffness of the wind turbine rotor blades 10, rotor blade bridges according to the prior art typically only employ the stiffest region (i.e. having the larger cross-section) of the rotor blade 10, in order to be able to be able to get a bridge span satisfying the design requirements, in particular the eigenfrequency requirement. The remaining, less stiff, part of the rotor blade 10 is typically cut-off and discarded. The inventor has, surprisingly, found that by using the less stiff part of the wind turbine rotor blade and arranging the third support location 53, a further stiffening effect of the wind turbine rotor blade 10 can be obtained, allowing to increase the primary span 21 , 31 of the bridge span.

[0036] This effect, is visualized in figure 2B, showing a single bridge span 2 of the bridge structure 1 and the simplified structural model 2” of the respective single bridge span 2 for the first eigenmode Mi (M as a visualization of a three-dimensional finite element model as shown in figure 4).

[0037] The further stiffening effect can be explained as follows. With reference to figure 3, various single span and double span configurations are shown. For simplicity, the respective spans shown in figure 3 comprise girders having an constant cross-section along the entire length. The upper configuration A shows the eigenmode Msfor a single span bridge 21 ’ that is supported at two support locations 51, 52 arranged at the respective longitudinal outer ends of the span. The lowest configuration C, which is shown on top of configuration B, is a double span 21 ’, 22’ that is supported at three supports locations 51, 52, 53’ that are evenly spaced from each other (i.e. both spans have equal length Li). The mass and stiffness of the spans 21’, 22’ are equal to each other and equal to the mass and stiffness of the single span 21’ shown in A Therefore, the first eigenfrequencies (of configuration A and C) are identical and the modeshape Msis equal to halve of the modeshape of MD, in other words, the second span 22’ does not add to the dynamic stiffness (i.e. impedance) of the first span 21’, such that the eigenfrequency of the single span bridge from A is equal to the double span bridge from C.

[0038] However, if the lengths of the spans are not equal, as is shown in B, then the shortest span (for simplicity of the explanation again assuming a girder having a constant cross-section along the entire length), i.e. second span 22, does add to the dynamic stiffness of the first span 21, such that the eigenfrequency of the first span 21 is increased and the modeshape Mi is also different In this respect, it is seen that the point of contraflexure C is also shifted, with respect to the modeshape MD, from the second support location 52 towards a position in between the first and second support locations 51, 52. The first eigenmode Mi that is indicated in configuration B in figure 3 is seen to comprise a bending of the primary span 21 in a first direction and a bending of the secondary span 22 in a second, opposite, direction. The required deformation of the second span 22 thereby effectively mobilizes the impedance of the secondary span 22 to act as an additional impedance on the first span 21.

[0039] The shorter the secondary span 22, as was explained above, the higher the additional stiffness effect will become, whereby in the limit case, the hinge-support at the second support location 52 effectively becomes a clamped connection. This effect also occurs when using a wind turbine rotor blade 10 as girder, although due to the more complex geometry of the blade, the effect of the second span on the first span is dependent on the actual geometry and mechanical properties of the blade. Hence, the added dynamic stiffness effect of the secondary span 22 can be modelled using an additional rotational spring 22” at the second support location 52. In practice, the ratio L2 / LI should be between 10% and 90%, with an optimum at around 50% - 60%, as indicated above.

[0040] Figure 4 shows the first eigenmode Mi ’ as a three-dimensional perspective visualization of a three- dimensional finite element model of the bridge span 2. The bridge span 2 comprises a first and second wind turbine rotor blade 10, 10’ that are arranged such that their longitudinal directions extend substantially along the longitudinal direction I of a bridge deck structure 60 that is arranged in between the respective wind turbine rotor blades 10, 10’. The rotor blades 10, 10’ extend from substantially the same longitudinal position in the same longitudinal direction, wherein the blade root sections 11, 11’ are thus arranged at the same longitudinal outer end 23 of the bridge span 2. The first, second and third support location 1, 52, 53 are arranged at substantially the same positions along the lengths of the respective rotor blades 10, 10’.

[0041] Figure 5 shows that bridge deck structure 60 that is connected to one of the wind turbine rotor blades 10 forming the girder of the bridge span 2,3. The bridge deck structure 60 is seen to comprise a bridge deck 61 for supporting traffic (e g. persons, bikes, cars, (light) trucks, etc ) thereon. In the current embodiment, the bridge deck 61 is formed from a solid plate, such as a cross-laminated timber (CLT), or a FRP sandwich-type plate, for instance formed from fibre reinforced polymer (FRP) upper and lower layers that are arranged around a foam core, preferably having a thickness in the range of 160mm - 500 depending on the size of the deck structure span (i .e. the width of deck structure) and type of traffic, although thinner or thicker plates may also be envisioned. The bridge deck structure 60 is seen to comprise a plurality of, preferably evenly, spaced apart connections, formed by the connection bodies 62, that allow to connect (by glue, bolts, screws, plugs and / or any combination thereof) the bridge deck structure 60 to the wind turbine rotor blade 10. The connections are then preferably arranged in the spar caps 16 of the rotor blade 10, as this is a stiff and reinforced section of the rotor blade that effectively forms, together with the shear web(s) 17, its backbone. Relatively high point-loads can thereby be effectively transferred between the rotor blade 10 and the bridge deck structure.

[0042] Figure 6 shows, in more detail, the structural details at the second support location 52, although this may be applied at any of the support locations 51, 52, 52. In order to distribute the support forces that are transferred between the respective support, in the current embodiment pier 42, and the wind turbine rotor blade 10, a load spreading member 71 is arranged on top of the pier 42. The load spreading member 71 is seen to comprise a pre-shaped plate, for instance of steel and / or a fibre-reinforced composite, that is arranged to substantially exactly fit a part of the outer surface of the wind turbine rotor blade 10 at the second support location 52. The pre-shaped plate may also be formed to have a substantially J- or U- shaped cross-section allowing the wind turbine rotor blade 10 to fall within the U-shape, thereby allowing for an even further improved load spreading. The load spreading member 71 is arranged to abut and / or connect to the wind turbine rotor blade 10 at the spar cap 16, which is able to transfer the high support forces and may be connected to the spar cap 16 by glue, bolts, screws, plugs and / or any combination thereof.

[0043] Figures 7A - 7C show various alternative embodiments of a load spreading member 72, 73, 74, which all share the common concept of providing an enlarged and stiffened area of contact between the supports and the wind turbine rotor blades 10. Load spreading member 72 extends from the spar cap 16 to the leading edge 12, whereas load spreading member 73 forms around the leading edge 12 by having the substantially J- or U-shaped cross-section. Load spreading member 74 is then arranged to be only at the location of the spar cap 16.

[0044] All possible suitable combinations of the above described embodiments are also part of the current disclosure. Additionally, the present invention is not limited to the embodiments shown, but also extends to other embodiments falling within the scope of the appended claims.

Claims

Claims1. Bridge span comprising: a first girder that is formed by at least a part of a first wind turbine rotor blade, wherein the at least a part of the first wind turbine rotor blade comprises, as seen along the length thereof, a proximal section, a distal section and a central section, wherein the central section is arranged in between the proximal and distal sections, and wherein the proximal section has a higher bending stiffness compared to the distal section; a bridge deck structure that is arranged for supporting traffic thereon, wherein said bridge deck structure extends in substantially a same longitudinal direction as the at least a part of the first wind turbine rotor blade and is connected to the at least a part of the first wind turbine rotor blade; and a plurality of supports that support the at least a part of the first wind turbine rotor blade at at least three support locations along its length; characterized in that a first support location is arranged at the proximal section, a second support location is arranged at the central section and a third support location is arranged at the distal section; and wherein a distance between the first and the second support locations is larger than a distance between the second and third support locations.

2. Bridge span according to claim 1, wherein the distance between the second and third support locations is in the range of 10% - 90%, preferably 30% - 80%, more preferably 40% - 70%, most preferably 50% - 60%, of the distance between the first and second support locations.

3. Bridge span according to any of the preceding claims, wherein the at least a part of the first wind turbine rotor blade comprises a blade root section that is arranged for connecting it to a rotor hub of a wind turbine; and wherein the first support location is at the blade root section of the at least a part of the first wind turbine rotor blade.

4. Bridge span according to any of the preceding claims, wherein the bridge span comprises a second girder that is formed by at least a part of a second wind turbine rotor blade and wherein said bridge deck structure is connected to the at least a part of the second wind turbine rotor blade.

5. Bridge span according to claim 4, wherein the at least a part of the second wind turbine rotor blade is oriented to be substantially in a same direction as the at least a part of the first wind turbine rotor blade and, preferably, wherein the blade root sections of the at least a part of the first wind turbine rotor blade and the at least a part of the second wind turbine rotor blade are arranged at a same longitudinal end of the bridge span, such that respective support locations on the at least a part of the first wind turbinerotor blade correspond to respective support locations on the at least a part of the second wind turbine rotor blade.

6. Bridge span according to any of the preceding claims, wherein the bridge deck structure is connected to the at least a part of the first wind turbine rotor blade, and preferably also the at least a part of the second wind turbine rotor blade, at a plurality of connection points that are spaced apart the length of the at least a part of the respective wind turbine rotor blade; preferably wherein said connection points are spaced apart no further than 8 meters, preferably no further than 5 meters, more preferably no further than 3 meters, most preferably no further than 2 meters.

7. Bridge span according to 6, wherein said connection points are formed in the spar cap of the at least a part of the first wind turbine rotor blade, and preferably also in the spar cap of the at least a part of the second wind turbine rotor blade.

8. Bridge span according to any of the preceding claims, wherein the bridge deck structure is a plate-like structure, that is preferably made from steel, cross-laminated timber (CLT) or fibre-reinforced polymer (FRP) composite.

9. Bridge span according to any of the preceding claims, wherein the bridge deck structure is shaped to have a pre-camber.

10. Bridge span according to any of the preceding claims, wherein at least one support of the plurality of supports comprises a load spreading member that is arranged for transferring support forces over a predefined surface area of the outer surface of the at least a part of the wind turbine rotor blade at the respective support location, in particular wherein an inner side of the load spreading member is shaped to correspond to the outer surface and / or comprises a channel-shaped section having a substantially U- or J- shaped cross-section for receiving the outer surface therein.

11. Bridge span according to any of the preceding claims, wherein said bridge span is formed as a double bridge span having a primary span that extends between the first and second support locations and a secondary span that extends between the second and third support locations.

12. Bridge span according to any of the preceding claims 1 - 9, wherein said bridge span is formed as a single bridge span having a single span that extends between the first and second support locations and wherein said second and third support locations are supported by a single footing structure and / or abutment.

13. Bridge span according to any of the preceding claims, wherein the distance between the first and third support locations is in the range of 50 - 95%, preferably 55% - 85%, more preferably 60% - 80%, most preferably 70% - 75%, of the length of the full wind turbine rotor blade.

14. Bridge span according to any of the preceding claims, wherein said bridge span is a foot- and / or bicycle bridge span, or wherein said bridge span is a road bridge span for supporting motorized vehicles.

15. Bridge structure comprising a first and second bridge span according to any of the preceding claims, wherein the first bridge span is oriented in a first direction and the second bridge span is oriented in a second, opposite, direction; wherein the blade root sections of the first and second bridge spans face each other; and wherein the bridge deck structures of the first and second span align for forming at least one continuing traffic lane over the respective bridge deck structures.

16. Bridge structure according to claim 15, wherein the blade root sections of the first and second bridge spans that directly face each other are not directly structurally interconnected to each other; and / or wherein the respective bridge deck structures of the first and second bridge spans are not directly structural interconnected to each other.

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