NL2037726B1

NL2037726B1 - Bridge span comprising a slanted wind turbine rotor blade

Info

Publication number: NL2037726B1
Application number: NL2037726A
Authority: NL
Inventors: Anne Maria Kloeg Boris
Original assignee: Univ Delft Tech
Priority date: 2024-05-21
Filing date: 2024-05-21
Publication date: 2025-11-27
Also published as: WO2025242548A1

Abstract

Bridge span extending in a longitudinal direction, the bridge span comprising: a ﬁrst girder that is forined by at least a part of a ﬁrst wind turbine rotor blade comprising a longitudinal axis that extends in a longitudinal direction; a bridge deck structure that is arranged for supporting trafﬁc thereon that extends longitudinally in substantially the same longitudinal direction as the at least a part of a ﬁrst wind turbine rotor blade and is substantially horizontally arranged in a cross-section perpendicular to the longitudinal direction, Wherein said bridge deck structure is connected to the at least a part of a ﬁrst wind turbine rotor blade; Wherein the at least a part of a ﬁrst wind turbine rotor blade is arranged in a slanted orientation around the longitudinal axis with respect to the bridge deck structure.

Description

Bridge span comprising a slanted wind turbine rotor blade

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 that is arranged in a slanted orientation with respect to the bridge deck structure, and a bridge structure comprising a plurality of said bridge spans.

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 recveled. 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 gravevards™. 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.

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. By arranging the wind turbine rotor blade, in particular its chord line, in the vertical orientation, the largest bending stiffness of the blade is used for supporting the span of the bridge, such that the largest possible span is obtainable. Many of the currently decommissioned wind turbines comprise blades in the order of 35 — 40 meters length, which theoretically could result in a bridge span of around 15 meter length.

A downside, however, is that the maximum chord of these blades is around 3 to 3.5 meters, thereby leading to either a very high bridge in case the rotor blade is arranged above, or below the deck structure, in order to allow for the required minimum clearance below the bridge. Alternatively, the rotor blades can protrude through the deck, or be arranged at the sides of the deck. In the former case, this leads to a separation in the middle of the deck, rendering a bridge with limited use. and in the latter case, this effectively leads to creating a bridge with very high side walls, which takes away any view for users and may even lead to triggering claustrophobic effects for certain users.

Arranging the blades in a horizontal arrangement, such that the chord line (i.e. a virtual line that can be drawn between the trailing and leading edges at maximum chord) is arranged substantially horizontally, results in a significant loss of stiffness, such that only very small spans are achievable.

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 relatively large spans are achievable, a non- obstructed bridge deck is obtainable and wherein the overall height of the bridge structure is limited, wherein at least some of the before mentioned problems are at least partly alleviated.

This goal is achieved by a first aspect of the current invention that relates to bridge span extending in a longitudinal direction, the bridge span comprising: a first girder that is formed by at least a part of a first wind turbine rotor blade comprising a longitudinal axis that extends in a longitudinal direction; a bridge deck structure that is arranged for supporting traffic thereon that extends longitudinally in substantially the same longitudinal direction as the at least a part of a first wind turbine rotor blade, and is substantially horizontally arranged in a cross-section perpendicular to the longitudinal direction, wherein said bridge deck structure is connected to the at least a part of a first wind turbine rotor blade; wherein the at least a part of a first wind turbine rotor blade is arranged in a slanted orientation around the longitudinal axis with respect to the bridge deck structure.

In order to achieve the maximum possible span using at least a part of a first wind turbine rotor blade, the chord line is to be oriented vertically, as was discussed above. The edge-wise (1.e. in the direction along the chord line) stiffness of a wind turbine rotor blade is, depending on specific blade type and longitudinal coordinate along the blade and with the exception of the blade root section, typically 3 to 8 times as stiff as the flap-wise stiffness. It was, however, found that by arranging the at least a part of a first wind turbine rotor blade at a slanted orientation with respect to the bridge deck structure, the height that the rotor blades take up can be significantly reduced, while the loss of stiffness is only limited. This can be explained as follows.

Assuming a wind turbine rotor blade has an edge-wise stiffness that is three times (i.e. n = 3) the flap- wise stiffness and the rotor blade is slanted (i.e. rotated around its longitudinal axis), such that the chord line is offset by 45° from a vertical orientation wherein it aligns with gravity. If this rotor blade is analysed in isolation of the rest of the bridge span structure. it will have a stiffness in vertical direction (i.e. parallel to the direction of gravity) that is roughly the average of the stiffness in the edge-wise and flap-wise direction (thus resulting in n = 2). Besides a vertical deflection due to the vertical loads applied, such as a self-weight or pedestrian applied load, this rotor blade would also have a horizontal deflection, purely as a result of the slanted orientation of the cross-section. However, if the bridge as a whole is considered, the horizontal deflection will experience an additional stiftness due to, for instance, the bridge deck structure. As the bridge deck structure has a certain bending stiffness in both directions and the axial stiffness of the bridge deck will want to limit the horizontal deflection of the wind turbine blade it is connected to, such that the bridge deck structure effectively acts as a lateral support. For such a rotor blade that is rotated at 45° without lateral support, the deflection would be twice as large compared to the vertical orientation, but the (ideal) lateral support limits this to a factor 1.5. As such, the reduction of the vertical stiffness due to rotating the wind turbine rotor blade along its longitudinal axis is reduced, while at the same time (assuming the 45° slanted angle), the effective height of the wind turbine rotor blade will be reduced by approximately the square root of 2, such that the height at maximum chord could be reduced from, for instance, 3.5 meters to approximately 2.5 meters, which is beneficial.

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 tvpically 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.

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 extends in substantially the same longitudinal direction as the at least a part of a first wind turbine rotor blade, wherein said bridge deck structure interconnects the at least a part of a first wind turbine rotor blade and second girder. A second girder to will improve the lateral support, such that the effective reduction in vertical stifthess is reduced.

Preferably, said bridge deck structure is arranged in between, and connected to the at least a part of a first wind turbine rotor blade and second girder.

It is further preferred that the second girder is formed by at least a part of a second wind turbine rotor blade, said at least a part of a second wind turbine rotor blade comprising a longitudinal axis extending in substantially the same direction as the longitudinal direction; and wherein the at least a part of a second wind turbine rotor blade is arranged in a slanted orientation around the longitudinal axis with respect to the bridge deck structure. This enables to repurpose more discarded wind turbine blades in an effective manner, while adding to the lateral support of the first wind turbine rotor blade. Preferably, the at least a part of a second wind turbine rotor blade is substantially identical to the at least a part of a first wind turbine rotor blade and slanted in the opposite direction with respect to the at least a part of a first wind turbine rotor blade. In case the at least a part of a second wind turbine rotor blade is slanted in the opposite direction and is a same type and part of rotor blade as the at least a part of a first wind turbine rotor blade, a downward deflection of the bridge span will cause that the first and second blades would want to deflect horizontally in opposite directions. The two (at least partial) wind turbine rotor blades thus restrain each other’s horizontal deformation as tie forces that are transferred though the deck structure that is arranged in between the respective wind turbine rotor blades to pull the two wind turbine rotor blades together. Not only do the wind turbine rotor blades then pull inward to prevent horizontal deflection, they also (as a result of the slanted orientation of the cross-section) pull upward, which in turn limits to total vertical deflection. As a result, the stiffness of the two bridge girders combined, in the form of oppositely slanted and interconnected wind turbine rotor blades, is higher than that of two separate girders.

In a preferred embodiment, the at least a part of a first wind turbine rotor blade has a first chord line, as determined at the location of maximum chord of the at least a part of a first wind turbine rotor blade, wherein the first chord line is an imaginary straight line joining the leading edge and trailing edge of the cross section of the at least a part of a first wind turbine rotor blade, as taken at the location of maximum chord; wherein the at least a part of a first wind turbine rotor blade is slanted such that the first chord line is at a first pitch angle of 10° - 60°, preferably 15° - 50°, more preferably 20° - 45°, even more preferably 25° -— 40°, most preferably 30° - 35°, wherein the first pitch angle 1s defined as the angle between the direction of gravity and the first chord line, wherein it is noted that said first pitch angle is an absolute value; preferably, wherein the at least a part of a second wind turbine rotor blade is slanted such that the second chord line is at a second pitch angle of 10° - 60°, preferably 15° - 50°, more preferably 20° - 45°, even more preferably 25° — 40°, most preferably 30° - 35°, wherein the second pitch angle is determined substantially similar to the first pitch angle, wherein it is noted that said second pitch angle is an absolute value: and preferably, wherein said second pitch angle is in the opposite rotational direction around a respective longitudinal axis as the first pitch angle. Within the given ranges of pitch angles, an effective trade-off between the vertical stiffness and the reduction in height is obtained. A too low pitch angle, will have a negligible effect on the reduction of height, whereas a too high pitch angle will result in a too large loss of vertical stiffness of the respective girders. In particular in the range between 30° and 45° a pitch angle is found that poses the ideal trade-off between height and stiffness for the most common cases.

Itis further preferred that the absolute value of the first and second pitch angles is different, preferably wherein they differ in a range of 0.1° — 10°, more preferably 2° - 8°, most preferably 4° - 6°. The cross- section of the wind turbine rotor blade is typically not symmetrical along the chord line. In particular, the trailing edge will be slightly biased towards one side. In order to compensate for this effect, a slight difference in the (absolute values of the) first and second pitch angels can be applied.

In a preferred embodiment, the bridge deck structure is shaped to have a pre-camber along the 5 longitudinal direction. At a suspended section of the bridge span that is arranged in between the respective supports at the outer longitudinal ends of the bridge span, the bridge deck structure is thereby given an upward deflection, such that it extends above a virtual straight line that can be drawn between the respective supports. Another criterium, apart from the minimum eigenfrequency, 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.

The pre-camber may be obtained by arranging the at least a part of a first wind turbine rotor blade and the second girder with a substantially horizontally acting tensional preload for urging the at least a part of a first wind turbine rotor blade and the second girder towards each other. As was described above, these tie- forces will also urge the slanted wind turbine rotor blades in an upwards direction, thereby automatically obtaining the desired pre-camber. Preferably, the substantially horizontally acting tensional preload is transferred through the bridge deck structure. This eliminates the need for arranging an additional system for setting the tensional preload.

It is preferred that 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.

This enables an effective transfer of tie-forces between the slanted wind turbine rotor blades through the bridge deck structure.

It is then further preferred that 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. The spar cap is relatively stiff, thick and solid part of the rotor blade such that is able to bear and transfer the tie-forces through the discrete connection points, 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).

Preferably, 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. A plate-like structure is beneficial as it increases the horizontal stiffness of the bridge and allows that the deck structure then transfers in- plane 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.

As was noted that, 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.¢. 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. In particular, more modern blades (i.e. less than 15 years old) tend to have a pre-curvature (i.e. a pre-camber) in the flap-wise direction to compensate for the inward bending due to the wind forces acting on them. To obtain an as usable straight deck structure, the blade is preferably oriented to be slightly non-parallel.

Therefore it is preferred that the longitudinal axis of the at least a part of the first wind turbine rotor blade is arranged at a first primary angle, wherein a primary angle is an angle around a vertical axis that is substantially perpendicular to the longitudinal direction, with respect to a central longitudinal axis of the bridge deck structure, wherein said first primary angle is in the range of 0.1° — 5°, preferably 0.5° - 4°, more preferably 1° - 3°, most preferably 1.5° - 2°; and/or wherein the longitudinal axis of the at least a part of the first wind turbine rotor blade is arranged at a first secondary angle, wherein a secondary angle is an angle around a horizontal axis that is substantially perpendicular to the vertical axis, with respect to a central longitudinal axis of the bridge deck structure, wherein said first secondary angle is in the range of 0.1° — 2°, preferably 0.2° - 1.5°, more preferably 0.3° - 1°, most preferably 0.4° - 0.8°; and, preferably, wherein said the longitudinal axis of the at least a part of the second wind turbine rotor blade is arranged at a second primary angle with respect to a central longitudinal axis of the bridge deck structure, wherein said second primary angle is in the range of 0.1° — 5°, preferably 0.5° - 4°, more preferably 1° - 3°, most preferably 1.5° - 2°, wherein said first primary angle is in the opposite direction of the second primary angle; and/or preferably, wherein the longitudinal axis of the at least a part of the second wind turbine rotor blade is arranged at a second secondary angle with respect to a central longitudinal axis of the bridge deck structure, wherein said second secondary angle is in the range of 0. 1° — 2°, preferably 0.2° - 1.5°, more preferably 0.3° - 1°, most preferably 0.4° - 0.8°. Note that the angles are given as absolute values.

In a second aspect, the disclosure relates to a bridge structure comprising a first and second bridge spans 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 a 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 16 meters is obtainable, such that this allows to span the two lanes and an emergency lane using the primary span. Approximately 20 - 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.

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 lead to an increased eigenfrequency of the respective bridge spans. 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.

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: - Figure 1 schematically shows a three-dimensional perspective view of an embodiment of a bridge span according to the disclosure. - Figure 2 schematically shows a cross-sectional view of the bridge span of figure 1. - Figure 3 schematically shows a three-dimensional perspective view of an embodiment a bridge structure according to the current disclosure. - Figures 4A and 4B schematically show, in a three-dimensional perspective and cross-sectional view, an embodiment of the bridge span that comprises a pre-camber. - 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. - 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.

- Figures 7A — 7C shows, in three-dimensional cross-sectional perspective views, various embodiments of load spreading members.

Figure 1 schematically shows a three-dimensional perspective view of an embodiment of a bridge span 2 that comprises a pair of (partial) wind turbine rotor blades 10, 10° that are supported at the longitudinal outer ends 21. 22 of the bridge span 2 on respective supports 41, 42. 42’. A first set of substantially U- shaped supports 41, 42 supports the second partial wind turbine rotor blade 10, and a second set of substantially U-shaped supports 42° (inner support 41 not visible at the first longitudinal outer end 21) supports the second partial wind turbine rotor blade 10°. Due to the asymmetric cross section of the wind turbine rotor blades 10, 10° near the second outer end 22 of the bridge span 2, the first and second outer supports 42, 42° are shaped slightly differently for receiving the rotor blades 10, 10° therein. As the inner supports 41 are arranged for receiving the substantially cylindrically shaped blade root sections 11 therein, the inner supports 41 are substantially similarly shaped. The first supports 41 are arranged to support the respective blade root sections 11 of the wind turbine rotor blades 10, 10°. The partial wind turbine rotor blades 10, 10° are directed in substantially the same longitudinal direction L such that the bridge deck structure 60, that extends in the longitudinal direction I, is arranged in between the respective wind turbine rotor blades 10, 10°. The bridge deck structure 60 is connected to, and supported by, the wind turbine rotor blades 10, 10°, such that these act as the girders of the bridge span 2. The girders are thus formed by the partial wind turbine rotor blades 10, 10°, each having a longitudinal axis II, II” that extends in substantially the same direction as the longitudinal direction I.

The wind turbine rotor blades 10, 10° comprise a leading edge 13 that is, in the current embodiment, directed in an inward and downward direction (i.e. inwardly with respect to the longitudinal axis I). At the opposite side of the wind turbine rotor blades 10. 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 13, 14. 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 of the wind turbine rotor blade 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.

The wind turbine rotor blades 10, 10° are shown to be arranged in a slanted orientation around their respective longitudinal axes IL II" with respect to the bridge deck structure 60. Figure 2, which shows a cross-section as taken through the respective locations of maximum edge height 12, shows that the chord lines C, C’ (te. a virtual line that is drawn between the leading and trailing edges 13, 14) of the respective partial wind turbine rotor blades 10, 10° are arranged at respective angles a, a’ with respect to a vertical (that is in the current embodiment substantially perpendicular to the bridge deck structure 60). In the current embodiment, the respective angles a. o” are around 35°, whereby the first angle o may be chosen slightly larger (i.e. in between 2° - 3°) due to the incoming curvature of the cross-section towards the trailing edge, and/or the second angle of may be chosen slightly smaller (i.e. in between 2° - 3°).

The effect of the slanted orientation is, as is already described above, that the height h of the rotor blades 10, 107 1s reduced, whereas the effect on the stiffness of the girders may be kept limited. Obviously, the slanted orientation does come with an increased width W‚W’ of the girders, that together with the width

Wh of the bridge deck structure 60, defines the overall width of the bridge.

Figure 3 schematically shows a three-dimensional perspective view of an embodiment a bridge structure 1 comprising a first and a second bridge span 2, 2° (as shown in figures 1 and 2) that are arranged almost mirror-symmetric with respect to each other around the mirror-plane III. The bridge structure 1 is however not fully mirror-symmetric, as the rotor blades 10, 10 themselves cannot be physically be mirrored. Rather, the bridge structure 1 is rotational symmetric around axis IV that is substantially vertical and parallel to the mirror-plane III (due to the asymmetry in the rotor blade 10 design). The bridge spans 2, 2” are thus arranged such that the respective blade root sections 11 of the respective wind turbine rotor blades 10, 10° that are in line with each other face each other. The bridge structure 1 may, for safety of the passing traffic and to protect the wind turbine rotor blades 10, 10° from accidental impacts, further be arranged with balustrades 80 that are arranged along the sides of the bridge deck structure 60.

Figures 4A and 4B schematically show, in a three-dimensional perspective and cross-sectional view, an embodiment of the bridge span that comprises a pre-camber along the longitudinal direction I, wherein the degree of pre-camber is highly exaggerated for display purposes. Similar in that, due to the slanted orientation of the wind turbine rotor blades 10, 10°, a vertical force applied to the wind turbine rotor blades 10, 10° results in a horizontal and vertical deformation (i.e. displacement) due to the bending of the rotor blades 10, 10°, a horizontal force that is applied to the (slanted) wind turbine rotor blades 10, 10° also results in horizontal and vertical deformation (i.e. displacement). As the wind turbine rotor blades 10, 10° are slanted in an outward direction, i.¢. wherein the trailing edge 14 extends outwardly, as seen along the horizontal direction IV, with respect to the leading edge 13, urging the wind turbine rotor blades 10, 10° towards each other, for instance by applying a horizontally acting tensional pre-load Fie (i.e. horizontal tie-force). results in a horizontal inward displacement Uy, and a vertical upward displacement

U, due to then bending of the (slanted) wind turbine rotor blades 10, 10°. The obtained vertical upward displacement U, thereby gives the desired pre-camber of the bridge span 2 along the longitudinal direction I, which is beneficial when designing a bridge that is to cope with heavier traffic such as cars and/or trucks.

The tie-forces Fi. may be introduced by arranging a bridge deck 61 having a reduced width when compared to the distance between the wind turbine rotor blades 10,10” at their respective locations where the connection members 62 are to be connected to the wind turbine rotor blades 10,107. A bridge deck structure 60 comprising a substantially plate-like bridge deck 61 that is formed from, steel, cross- laminated timber (CLT) and/or fibre-reinforced polymer (FRP) composite material, or a combination thereof, is highly suitable for arranging the pre-load between the respective wind turbine rotor blades 10,10.

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 steel plate, cross-laminated timber (CLT) plate, 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. The bridge deck 61 preferably has 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. This thereby also allows to effectively transfer the tie-forces between the respective wind turbine rotor blades 10.107, as was described above.

Figure 6 shows, in more detail, the structural details at the second support location 52, although this may be applied at any of the supports 41,42,42°. In order to distribute the support forces that are transferred between the respective support 42, and the wind turbine rotor blade 10, a load spreading member 71 is arranged on top of the support 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 support 42. 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.

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 1s then arranged to be only at the location of the spar cap 16.

Al possible suitable combination 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

Conclusions

1. A bridge span extending in a longitudinal direction, the bridge span comprising: a first girder formed by at least a portion of a first wind turbine rotor blade having a longitudinal axis extending in a substantially longitudinal direction; a bridge deck structure suitable for carrying traffic thereon, extending longitudinally in substantially the same longitudinal direction as the at least a portion of a first wind turbine rotor blade and being substantially horizontal in a cross-section perpendicular to the longitudinal direction, the bridge deck structure being connected to the at least a portion of a first wind turbine rotor blade; characterised in that the at least a portion of a first wind turbine rotor blade is disposed in an oblique orientation about the longitudinal axis relative to the bridge deck structure.

2. The bridge span of claim 1 comprising a second girder extending in substantially the same longitudinal direction as the at least part of a first wind turbine rotor blade, the bridge deck structure connecting the at least part of a first wind turbine rotor blade and the second girder.

3. A bridge span as claimed in claim 2, wherein the second girder is formed by at least a portion of a second wind turbine rotor blade, the at least a portion of a second wind turbine rotor blade comprising a longitudinal axis extending in substantially the same direction as the longitudinal direction; and the at least a portion of a second wind turbine rotor blade being disposed in an oblique orientation about the longitudinal axis relative to the bridge deck structure.

4. A bridge span as claimed in claim 3, wherein the at least part of a second wind turbine rotor blade is substantially identical to the at least part of a first wind turbine rotor blade and is slanted in the opposite direction relative to the at least part of a first wind turbine rotor blade.

5. A bridge span according to at least one of the preceding claims, wherein the at least part of a first wind turbine rotor blade has a first chord line as determined at the location of the maximum chord of the at least part of a first wind turbine rotor blade, the first chord line being an imaginary straight line connecting the leading edge and the frailing edge of the cross-section as taken at the location of the maximum chord of the at least part of a first wind turbine rotor blade; wherein the at least part of a first wind turbine rotor blade is inclined such that the first chord line is at a first pitch angle of 10° - 60°, preferably 15° - 50°, more preferably 20° - 45°, even more preferably 25° - 40°, most preferably 30° - 35°,

where the first pitch angle is defined as the angle between the gravity direction and the first chord line.

6. A bridge span according to at least claim 3, wherein the at least part of a second wind turbine rotor blade has a second chord line as defined at the location of the maximum chord of the at least part of a second wind turbine rotor blade, the second chord line being an imaginary straight line connecting the leading edge and the trailing edge of the cross-section, as taken at the location of the maximum chord, of the at least part of a second wind turbine rotor blade; wherein the at least part of a second wind turbine rotor blade is inclined such that the second chord line is at a second pitch angle of 10° - 60°, preferably 15° - 50°, more preferably 20° - 45°, even more preferably 25° - 40°, most preferably 30° - 35°, the second pitch angle being defined substantially equal to the first pitch angle; and preferably, wherein the second pitch angle is in the opposite direction of rotation about a respective longitudinal axis as the first pitch angle.

Bridge span according to at least claim 4, wherein the absolute value of the first and second pitch angles are different, preferably differing in a range of 0.1° - 10°, preferably 2° - 8°, preferably 4° - 6°.

8. Bridge span according to at least one of the preceding claims, wherein the bridge deck structure is shaped such that it has a pre-camber in the longitudinal direction.

9. Bridge span according to at least claim 2, wherein the at least part of a first wind turbine rotor blade and the second girder are provided with a substantially horizontally acting tensile prestress to urge the at least part of a first wind turbine rotor blade and the second girder towards each other.

10. Bridge span according to claim 9, wherein the substantially horizontally acting tensile prestressing is transferred by the bridge deck structure.

IL. Bridge span according to at least one of the preceding claims, wherein the bridge deck structure is connected to the at least part of the first wind turbine rotor blade, and, preferably, when dependent on at least claim 3. also to the at least part of the second wind turbine rotor blade, at a plurality of connection points distributed over the length of the at least part of the respective wind turbine rotor blade: preferably wherein the distance between the connection points is not more than 8 metres, preferably not more than 5 metres, more preferably not more than 3 metres, and even more preferably not more than 2 metres.

12. Bridge span according to claim 11, wherein the connection points are formed in the spar cap of the at least part of the first wind turbine rotor blade, and preferably also in the spar cap of the at least part of the second wind turbine rotor blade.

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

Bridge span according to at least one of the preceding claims, wherein the longitudinal axis of the at least part of the first wind turbine rotor blade is at a first primary angle with respect to a central longitudinal axis of the bridge deck structure, wherein a primary angle is an angle about a vertical axis that is substantially perpendicular to the longitudinal direction, with respect to a central longitudinal axis of the bridge deck structure, wherein the first primary angle is between 0.1° and 5°, preferably between 0.5° and 4°, more preferably between 1° and 3°, and even more preferably between 1.5° and 2°; and/or wherein the longitudinal axis of the at least part of the first wind turbine rotor blade is at a first secondary angle, wherein a secondary angle is an angle about a horizontal axis that is substantially perpendicular to the vertical axis, with respect to a central longitudinal axis of the bridge deck structure. wherein the first secondary angle is between 0.1° and 2°, preferably between 0.2° and

1.5°, more preferably between 0.3° and 1°, and even more preferably between 0.4° and 0.8°; and, preferably, wherein the longitudinal axis of the at least part of the second wind turbine rotor blade is disposed at a second primary angle relative to a central longitudinal axis of the bridge deck structure, wherein the second primary angle is between 0.1° and 5°, preferably between 0.5° and 4°, more preferably between 1° and 3°, and even more preferably between 1.5° and 2°, wherein the first primary angle is in the opposite direction of the second primary angle; and/or preferably, wherein the longitudinal axis of the at least part of the second wind turbine rotor blade is disposed at a second secondary angle relative to a central longitudinal axis of the bridge deck structure. wherein the second secondary angle is between 0.1° and 2°, preferably between 0.2° and 1.5°, more preferably between 0.3° and 1°, and even more preferably between 0.4° and 0.8°.

15. Bridge span according to at least one of the preceding claims, wherein the bridge span is a pedestrian and/or bicycle bridge span or wherein the bridge span is a road bridge span.

A bridge structure comprising a first and second bridge span according to at least one 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 leaf root sections of the first and second bridge spans face each other; and wherein the bridge deck structures of the first and second spans are aligned to form at least one continuous roadway over the respective bridge deck structures.

17. The bridge structure of claim 16, wherein the directly opposed leaf root sections of the first and second bridge spans are not directly structurally connected to each other; and/or wherein the respective bridge deck structures of the first and second bridge spans are not directly structurally connected to each other.