U.S. patent application number 15/974822 was filed with the patent office on 2019-04-11 for precast concrete post tensioned segmented wind turbine tower.
The applicant listed for this patent is WIND TOWER TECHNOLOGIES, LLC. Invention is credited to JAMES D. LOCKWOOD, WILLIAM D. LOCKWOOD.
Application Number | 20190106856 15/974822 |
Document ID | / |
Family ID | 50024107 |
Filed Date | 2019-04-11 |
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United States Patent
Application |
20190106856 |
Kind Code |
A1 |
LOCKWOOD; JAMES D. ; et
al. |
April 11, 2019 |
PRECAST CONCRETE POST TENSIONED SEGMENTED WIND TURBINE TOWER
Abstract
The present disclosure is directed to
Inventors: |
LOCKWOOD; JAMES D.;
(BOULDER, CO) ; LOCKWOOD; WILLIAM D.; (DAYTON,
OH) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
WIND TOWER TECHNOLOGIES, LLC |
BOULDER |
CO |
US |
|
|
Family ID: |
50024107 |
Appl. No.: |
15/974822 |
Filed: |
May 9, 2018 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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14868053 |
Sep 28, 2015 |
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15974822 |
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13957596 |
Aug 2, 2013 |
9175670 |
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14868053 |
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61742070 |
Aug 3, 2012 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
E04H 12/342 20130101;
F03D 13/20 20160501; E02D 27/425 20130101; F05B 2240/912 20130101;
E04H 12/12 20130101; F03D 13/22 20160501; Y02E 10/728 20130101;
E04H 12/16 20130101 |
International
Class: |
E02D 27/42 20060101
E02D027/42; E04H 12/34 20060101 E04H012/34; F03D 13/20 20060101
F03D013/20; E04H 12/16 20060101 E04H012/16; E04H 12/12 20060101
E04H012/12 |
Claims
1-18. (canceled)
19. A precast concrete tower for supporting a wind turbine,
comprising: a base member positioned to support a tower; a series
of precast concrete annular tower segments supported by the base
member forming a vertical stack of the tower segments; match-cast
annular joints between the annular tower segments, the joints
comprising: a connecting face of a first segment of the plurality
of annular tower segments has a characteristic of being cast
against an adjacent segment in the plurality of annular tower
segments.
Description
CROSS REFERENCE
[0001] This application is a continuation of U.S. patent
application Ser No. 14,868,053, filed on U.S. Sep. 28, 2015,
entitled "PRECAST CONCRETE POST TENSIONED SEGMENTED WIND TURBINE
TOWER, which claims the benefit of priority to U.S. patent
application Ser. No. 13/957,596 filed on Aug. 2, 2013, entitled
"PRECAST CONCRETE POST TENSIONED SEGMENTED WIND TURBINE TOWER," the
contents of which are herein incorporated by reference in their
entireties.
BACKGROUND OF THE INVENTION
[0002] The existing methods of constructing wind towers vary
depending on whether the materials are steel or concrete. The
decision process used to select steel or concrete depends on the
geographic location, regional resources and access to the wind farm
site. Steel wind towers are commonly built through bolting of steel
tubular sections together at intermediate flanges. The heights of
steel towers are often limited by the diameter of the steel tubular
sections that can be physically transported from the location of
the steel fabricator to the wind farm site without significant
modifications to existing roads, bridges, rail infrastructure,
hauling equipment and other physical constraints. These limitations
typically result in steel member diameters to approximately 20 ft.,
which in turn limits the tower height to approximately 300 ft.
using conventional strength steel. Energy production from a wind
tower has been typically shown to increase by increasing the height
of the tower as a result of improved consistency in laminar wind
flow. To increase the height of steel towers, some developers are
installing concrete pedestals underneath the base of the steel
tower.
[0003] Concrete towers being constructed today by using precast
methods and cast in place methods. The advantages of concrete
towers are they can be constructed using regional labor and
materials and typically do not have height limitations as a result
of transportation constraints since these towers can be fully
fabricated on site. Cast in place construction methods utilize
vertically extending formwork to support the pouring of fresh
concrete into the forms at height. Restrictions to this method are
the reduced speed of construction and sensitivity to inclement
weather. Existing precast concrete techniques commonly precast the
elements in a manner that results in vertical and horizontal
joints, requiring joining of the elements during construction with
grout. In this solution, post-tensioning in both directions can
often be required to achieve a durable tower structure.
[0004] Other precast solutions involve the grinding of the annular
horizontal concrete surfaces to achieve a quality load bearing
connection. The segments are commonly precast offsite or nearby to
the tower farm. The vertical post-tensioning is commonly located
inside the concrete wall where it is anchored. The common geometry
of a concrete wind tower is tapered, creating additional complexity
in the forming system and placement of reinforcing and
post-tensioning geometry. The challenges inherent to the existing
steel and concrete tower designs and construction methods are their
limitation on geometry in the case of steel towers and the
complexity of the concrete towers.
SUMMARY OF THE INVENTION
[0005] This invention improves the construction of a precast
concrete wind tower through its design and pre-casting methods. One
primary feature of the invention is the forming of a stepped tower,
whereby transition rings or annular anchor members or donut
sections are used to transfer the post-tensioning tendon forces
into the sections of the tower. The donut segments perform as
intermediate diaphragm segments for the post-tensioning and
transition zones for the change in tower diameter or horizontal
cross-section. This feature eliminates the requirement for
post-tensioning anchor blisters external to the inside of the tower
wall to anchor the post-tensioning tendons. The axial loads and
bending moments as a result of the step change in tower diameter or
cross-section are resisted by the transition donut sections. The
transition donut sections also allow for vertical tower sections
having a constant or uniform geometry between the donut sections
which significantly simplifies both the site pre-casting operation
and the installation of the precast tower segments. Each precast
segment is match-cast against the previously cast segment to
achieve a match cast joint, eliminating the need for a secondary
operation in the field to secure the joint mechanically or the need
for using grout.
[0006] The tower structure segments are precast using match casting
techniques where each segment connecting face is cast against its
adjacent segment. Segments are typically designed to have similar
weights, so that the lifting equipment used on site is optimized
during the placement of segments. The tower segments may be uniform
or constant in diameter or cross-section over a length of segments
and between segment joints for producing segments for the stepped
tower geometry or be tapered to result in a tapered tower shape
where the top of the tower is a smaller diameter than its base and
linearly tapered. The precast segments may be cast on site using a
formwork system that is mobile. The formwork is designed and
fabricated such that the end of the form is the actual segment
previously cast, constituting the match cast face. The formwork can
be moved to position it against each segment cast. As a segment is
cast and after being used to match cast the next segment, it is
moved from the immediate casting area to the casting yard for
storage until used in the tower.
[0007] Alternatively, each tower segment being cast can be moved
and the formwork held stationary during the match casting process.
In both circumstances, segments are only required in the immediate
casting area during casting or match casting. The number of forms
required on site is a function of the casting production rate
required. Only a limited amount of space (only two segments in
length) is required to establish the match casting operation from
one form. In all cases, a regional precaster may be used to
fabricate the segments away from the site and then transport the
segments to the site. However, it is considered advantageous to
have the option to cast on site and to obtain concrete from a site
operated batch plant or ready mix company. Precast segments are
placed onto shims to level the base segment prior to stacking
others on top. The base segment, once leveled, is then grouted
between the precast base concrete segment and the foundation
element.
[0008] To increase shear capacity across joint and align joints
upon placement, shear keys are cast into the segments interfaces
with the adjoining segment. To ease placement and create a tightly
sealed seal between segments, epoxy is placed onto the joints prior
to joining together. In a design option where tendons are located
inside and adjacent the concrete wall, the epoxy also serves to
better seal the joint during the grouting operation of the
post-tensioning tendon ducts. When the precast segmental tower
experiences external wind loads on the blade and tower structure,
the bending moment existing at the base of the tower is largely
resisted in tension by post-tensioning tendons that extend from the
tower into the foundation element.
[0009] The use of post-tensioning tendons are used to reinforce the
precast segmental tower at the most effective locations along the
height of the tower to resist the tension in the tower under
externally applied loads. The tendon locations are vertically
tiered and anchored to provide the post-tensioning forces where
loads are higher. Example: Where bending moments and resulting
forces are higher towards the base of the tower under applied
loads, the post-tensioning quantities are also higher to counter
these applied loads. The tendons terminate over or along the height
of the tower into the annular donut sections which act as internal
diaphragms. External tendons to the concrete and inside the tower
chamber may be used alone or in combination with internal tendons
placed within tubes or ducts inside the concrete walls of the
tower.
[0010] To facilitate any requirements for additional intermediate
anchor zones for the vertically placed post-tensioning tendons,
annular diaphragm rings or anchor members may be cast into the
tower segments to anchor internal tendons. When external tendons
are used, these diaphragm rings or members serve to anchor tendons
and can also be used to deviate or terminate the tendons or allow
them to pass through. For internal tendons within the concrete
wall, the diaphragm ring or anchor member serves as an annular
blister to the concrete where the tendon can exit the concrete wall
and be stressed and anchored.
[0011] The connection of a steel tip adapter that supports the
nacelle and blades is achieved using a precast segment that
contains a concrete diaphragm cast into the segment. The top of
this segment is flat in the area of the steel to concrete
connection. In the event that a steel tower section, as in a hybrid
tower, is placed above the precast concrete tower, the precast
diaphragm segment is located just below the intersection of the two
structures. The diaphragm segment is dimensioned such that its
weight is compatible with the tower segment weights to optimize the
crane or equipment used to install each segment. Other criteria
that affects the geometry of the top diaphragm is the location of
the bolt circle used to secure the nacelle of top tower section to
the precast tower. To achieve an efficient transition of forces
from the loads at top of the precast tower to the precast tower
walls, the tendons anchored in the precast tower may be extended
into the top of the diaphragm and anchored. The bolts connecting
the nacelle or top tower section can then be anchored to the
underside of the concrete diaphragm.
DESCRIPTION OF THE DRAWINGS
[0012] FIG. 1 is a stepped segmental concrete wind tower composed
of precast concrete segments 47, 47; and 47'', transition donut
sections 50 and 50', a tip adapter 33 and a foundation type 30 or
32.
[0013] FIG. 2 illustrates a fragmentary section taken on the line
2-2 of FIG. 3 and showing a shear key configuration 49 which may be
match cast and used to transfer shear across the segmental joints
29 under transverse loads to the tower and to assist in the
alignment of one segment placed against the adjacent segment.
[0014] FIG. 3 is a fragmentary section taken on the line 3-3 of
FIG. 1 and an internal post-tensioning cables 34 connected to a
transition donut section 50 with adjacent tower segments 28 and 28'
attached by transverse shear key joints 29 that are match cast.
[0015] FIG. 4 is a fragmentary section of internal post-tensioning
cables 34 connected to an alternate transition donut section 48
with adjacent segments 28 and 28' attached by transverse shear key
joints 29 that are match cast.
[0016] FIG. 5 is a fragmentary section of external post-tensioning
cables 35 for a transition donut section 50' with adjacent tower
segments 28 and 28' attached by transverse shear key joints 29 that
are match cast.
[0017] FIG. 6 is a fragmentary section of external post-tensioning
cables 35 for an alternate transition donut section 48 with
adjacent tower segments 28 and 28' attached by transverse shear key
joints 29 that are match cast.
[0018] FIG. 7 is a vertical section of tower segments having
annular diaphragm rings or anchor members where the external
post-tensioning tendons 35 terminate or tendons 37 pass through the
annular anchor members cast within the precast segments.
[0019] FIG. 8 is a section taken on the line 8-8 of FIG. 7 and
showing where the external post-tensioning tendons terminate
35.
[0020] FIG. 9 is a section taken on the line 9-9 of FIG. 7 and
showing where the external post-tensioning tendons 35 terminate or
tendons 37 pass through the annular diaphragm or anchor member.
[0021] FIG. 10 is a section taken on line 10-10 of FIG. 7 and
showing where the external post-tensioning tendons 35 terminate or
tendons 37 pass through the annular diaphragm or anchor member.
[0022] FIG. 11 is a vertical section of tower sements having
annular diaphragm rings or anchor members where the internal
post-tensioning tendons 34 terminate or pass through the annular
diaphragms or anchor members located within the precast tower
segments.
[0023] FIG. 12 is a section taken on line 12-12 of FIG. 11 and
showing where the internal post-tensioning tendons 34
terminate.
[0024] FIG. 13 is a section taken on the line 12-12 of FIG. 11 and
showing where the internal post-tensioning tendons 34 terminate or
tendons 36 pass through the annular diaphragm or anchor member.
[0025] FIG. 14 is a section taken on the line 14-14 of FIG. 11 and
showing where the internal post-tensioning tendons 34 terminate or
tendons 36 pass through the annular diaphragm or anchor member.
[0026] FIG. 15 is a fragmentary section of tower segments 28
attached to a foundation base 30.
[0027] FIG. 16 is a fragmentary section of tower segments 28 seated
on shims 31 on the foundation base 30 to properly align the
vertical geometry prior to placing the subsequent segments
above.
[0028] FIG. 17 is a fragmentary section of tower segments 28 with
grout 44 poured between the bottom base precast segment 28 and the
foundation base 30.
[0029] FIG. 18 is a plan view of a base 30 and showing the tendons
38 that connect the tower structure to the foundation base.
[0030] FIG. 19 is a fragmentary section taken on the line 19-19 of
FIG. 18 and showing the connection of the bottom tower segment 28
to the foundation base 30 with U-shape hoop portions 39 of the
tendons.
[0031] FIG. 20 is a fragmentary section taken on the line 19-19 of
FIG. 18 and showing the connection of the bottom tower segment 28
to the foundation base 30 with tendons 38 having L-shape
configuration and terminating at the outside of the foundation with
terminals 40.
[0032] FIG. 21 is a fragmentary section taken on the line 21-21 of
FIG. 22 and showing precast segment 55 where a nacelle 41 for the
tip adapter 33 attaches to the tower structure with external
post-tensioning tendons 35.
[0033] FIG. 22 is a plan view of the FIG. 21 and depicting how
anchor rods or bolts 42 attach the nacelle 41 and tip adapter
33.
[0034] FIG. 23 is a fragmentary section taken on the lie 21-21 of
FIG. 22 and showing precast segment 55 with the nacelle 41 and tip
adapter 33 attached to the tower structure with the internal
post-tensioning tendons 34.
[0035] FIG. 24 is a plan view of FIG. 23 and depicting how the
anchor rods 42 attach the tip adapter 33.
[0036] FIG. 25 shows another embodiment of a hybrid tower that uses
match casting concrete tower segments supporting a steel tower 33
with the bottom tower segment placed on top of a precast or
cast-in-place concrete pedestal 46.
[0037] FIG. 26 is a section of the tower taken on the line 26-26 of
FIG. 25 and having match cast segments with flat sides to form
either the stepped tower of FIG. 1 or the hybrid tower of FIG. 25,
and
[0038] FIG. 27 is a section taken on line 27-27 of FIG. 25 and
showing match cast segments having internal and external
post-tensioning tendons 34 & 35.
DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS
[0039] A stepped tower is shown in FIG. 1 and is assembled using
annular and cylindrical precast concrete tower segments 47, 47' and
47'' with transverse (horizontal) joints 29 (FIGS. 3 & 4) that
are match cast together to achieve a precision fit between adjacent
segments. The match cast joint detail 45 is shown in FIG. 2 and
incorporates a shear key configuration used to transfer shear
across the segmental joints under transverse loads to the tower and
to assist in the alignment of one segment with each adjacent
segment. Epoxy is applied onto the bottom surface of the joint 45
of FIG. 2 prior to closing the gap 49 between the two segments. The
epoxy serves the purpose of a lubricant during the segment
placement operation and also as a sealing of the joint after the
epoxy cures.
[0040] At each step or change in diameter of the tower structure, a
transition annular donut member or segment or anchor member 48, 50,
50' (FIGS. 3-6) transfers the forces through the geometry
transition and also serves as an anchorage zone for the vertical
post-tensioning tendons 34. The transition donut or anchor member
may be used for internal post-tension tendons 34 located inside the
concrete wall of the tower structure, as shown in FIGS. 3 & 4,
or for external post-tensioning tendons 35, as shown in FIGS. 5
& 6 outside the tower wall within the tower chamber. The
annular transition donut or anchor member 50 has a frusto-conical
outer surface 51 (FIG. 5) and is also match cast at 29 against its
adjacent tower segments 28 and 28' to provide a precision fit
during installation of the segments. In the design of
post-tensioning tendons 34 placed inside the tower wall (FIGS. 3
& 4), the tendons 34 below the transition donut segment 50 pass
upwards through the donut segment and may either curve inwards to
anchor inside the tower chamber, as shown in FIG. 3, or extend
straight upwards, anchoring on the outside of the tower segment 48,
as shown in FIG. 4. In the design of external post-tensioning
tendons 35, as shown in FIGS. 5 & 6 within the tower, the
tendons 35 enter the transition donut segment or 50 from outside of
the concrete tower wall and are placed close to or adjacent the
wall.
[0041] The most efficient layout of post-tensioning in the tower
includes intermediate points to anchor the tendons 35. This is
achieved by using annular internal and integral anchor members or
diaphragm rings 52 or 52', as shown in FIGS. 7 & 11. For
external post-tensioning, the anchorages or tendons 35 either
terminate or pass through the annular anchor members or diaphragm
rings located within the precast segments. As a result of the
increased bending moments at the base of the tower and reducing
along the tower's height, a higher concentration of post-tensioning
tendons 35 are shown in FIG. 10 than in FIGS. 8 & 9. The
annular anchor member or diaphragm is cast directly into a tower
segment with the tendon tubes or ducts located and incorporated
into the segment. The annular diaphragm rings 52 or 52'may also
serve as deviation points for the external tendons 35 if necessary
to avoid equipment or other interferences located inside the tower
structure near the walls. For internal post-tensioning as shown in
FIG. 11, the annular anchor members or diaphragms rings 52' are
located within a segment and its bottom shape may be tapered to
follow the trajectory of the tendon and exiting the tower wall. The
use of an annular diaphragm ring 52' allows the internal tendons 34
to exit the tower wall and anchor without having to deviate the
tendon transversely within the tower wall to fixed location. This
allows the post-tensioning to be more effective with reduced
friction losses that commonly accompany tendon deviations. The
higher concentration of tendons 34 and external tendons 36 in FIG.
14 in comparison to FIGS. 12 & 13 is a result of the higher
bending moments that exist in the tower closer to the base 30.
[0042] The bottom side of the base precast tower segment 28 of FIG.
15 is shimmed with shims 31, as shown in FIG. 16, engaging the
foundation structure 30 to properly align the vertical geometry
prior to placing the subsequent tower segments above. Once aligned,
grout 44 (FIG. 17) is poured between the bottom of the base precast
segment and the foundation structure 30. A shallow recess or trough
formed within the top of the foundation during the foundation
concrete pour can be used to contain the grout and fill the void
between the bottom of the precast base tower segment 28 and the
foundation 30.
[0043] The geometry of the tendons shown in FIG. 18 that connect
the tower structure to the foundation structure 30 are comprised of
either a U-shape hoop configuration 39 (FIG. 19) or an L-shape hook
configuration 38 shown in FIG. 20. In the hoop configuration, both
ends of the same tendon are stressed from the anchorages located
inside the tower structure. A benefit of the tendon configuration
of FIG. 20 is that the compressive force of the tendons reduces the
shear stresses in the concrete foundation structure 30 when the
tendons hook back upwards and have terminals 40 on the surface the
foundation 30. A benefit of the tendon configuration of FIG. 19 is
that the hoop tubes or ducts for the tendons occupy less space in
the foundation structure 30 than the ducts for the tendons 38 shown
in FIG. 20. In both tendon configurations, the tendons 38 & 39
will typically be stressed from the anchorages inside the tower.
The L shaped tendon 38 shown in FIG. 20 can be stressed both from
the inside of the tower and from the face of foundation to maximize
the force in the tendon in the foundation structure. These tendons
for both configurations can also be stressed from the top of the
precast concrete segment 51 shown in FIGS. 1, 21 & 23.
[0044] The top precast segment 55 of the tower, shown in FIGS. 1,
21 & 23, connects the tower structure to a tip adapter 33 (FIG.
1) provided by the turbine supplier. The connection is accomplished
by anchoring the post-tensioning tendons 34 or 35 into a recess or
cavity on top of the segment 55 and using anchor rods or bolts 42
to connect the steel flange ring 41 of the tip adapter 33 to the
underside of the segment 55. This connection is applicable for both
external tendons 35 of FIGS. 21 & 22 and internal tendons of
FIGS. 23 & 24. To provide access from inside the tower to the
inside of the tip adapter, a diaphragm opening is provided.
[0045] The use of match casting segments can be used to construct a
hybrid tower whereby a steel tower 33 (FIG. 25) and tower segments
47 are placed on top of a precast concrete pedestal 46 shown in
FIG. 25. The cross sectional geometry of the annular match cast
segments may be round (FIG. 1) or flat sided (FIG. 26) for the
stepped tower of FIG. 1 or the hybrid tower of FIG. 25. In the case
of a flat sided tower, the post-tensioning tendons 34 or 35 are
located along the flat sides of the tower as shown in FIGS. 26
& 27. These tendons can be designed for placement inside the
tower wall or external to the tower wall, according to the space
available inside the tower. When using the flat walls of FIG. 27,
the tower may be tapered more easily than a round or cylindrical
structure. Using flat walls, a tapered tower section 46 is provided
as the base section before changing to a constant or uniform
cross-sectional geometry.
[0046] While the forms of segmental wind turbine towers herein
described constitute preferred embodiments of the invention, it is
to be understood that the invention is not limited to these precise
forms, and that the changes made therein without departing from the
scope of the invention as defined in the appended claims.
* * * * *