Note: Descriptions are shown in the official language in which they were submitted.
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BRIDGE SYSTEM AND METHOD INCLUDING FOUR SIDED CONCRETE
BRIDGE UNITS ADAPTED FOR PROMOTING SEDIMENTATION
CROSS-REFERENCES
[0001] This application claims the benefit of U.S. Provisional
Application Serial
No. 61/535,565, filed September 16, 2011, which is incorporated herein by
reference.
TECHNICAL FIELD
[0002] The present application relates to the general art of precast
concrete bridge
and culvert units, and to the particular field of four-sided bridge and
culvert units.
BACKGROUND
[0003] Overfilled bridge structures are frequently formed of precast
reinforced
four-sided concrete units commonly referred to as arch units, arch culverts,
box units or
box culverts. As used herein the terminology four-sided bridge unit
encompasses all of
such structures. The units are used in the case of bridges to support one
pathway over a
second pathway, which can be a waterway. Four-sided bridge units have a bottom
wall
structure that facilitates on-site placement with reduced need for foundation
preparation.
[0004] In the past, the four-sided bridge units of overfilled bridge
structures have
been constructed with bottom wall structures having a generally planar and
continuous top
surface and a generally uniform thickness. There is an increasing demand for
construction
efforts to provide more natural environments and/or to decrease impact on
wildlife.
[0005] A four-side bridge unit adapted to create a more natural
environment
through the pathway defined by the bridge units and/or adapted to reduce
impact on fish
migrations would be desirable.
SUMMARY
[0006] In one aspect, a method of providing an environmentally appealing
region
for water flow along an surrounded pathway tunnel is provided. The method
involves:
providing a plurality of four-sided concrete bridge units in abutting
relationship to create a
surrounded pathway tunnel, one end of the tunnel located upstream along a
water path and
an opposite end of the tunnel located downstream along the water path;
allowing water to
flow through the surrounded pathway tunnel during a rain or other flow event;
and
providing a multiplicity of the four-sided bridge units with a corresponding
bottom wall
structure that interacts with the flowing water and earthen material in the
flowing water
such that capture and settling of the earthen material at locations along the
tunnel occurs to
produce a more natural water flow pathway along the tunnel.
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[0007] The bottom wall structure of each of the multiplicity of the four-
sided
bridge units may be provided with a plurality of through openings such that at
least forty
percent of the bottom wall structure is open. For example, at least fifty
percent of the
bottom wall structure of each of the multiplicity of the four-sided bridge
units may be
open.
[0008] A lip structure may be provided at a top portion of at least some
of the
through openings, the lip structure facing upstream.
[0009] The plurality of openings of each bottom wall structure may be
arranged in
rows that extend along a span of the respective four-sided bridge unit.
[0010] The plurality of openings may be formed in the shape of elongated
slots,
each elongated slot defining a row, such that multiple beams are formed in the
bottom wall
structure and also extend along the span. At least one beam with a height that
is greater
than a height of another beam, the higher beam interacting with the flowing
water and
earthen material to reduce flow velocity and thereby enhance settling out of
earthen
material. By providing a lip structure along at least one beam, the lip
structure extending in
an upstream direction into an adjacent elongated slot, wash out of earthen
material that has
settled in the adjacent elongated slot can be limited.
[0011] The plurality of openings may be provided as multiple series of
openings,
each series of openings forming a respective row. By staggering openings of
adjacent
rows, nesting of the openings is achieved. By providing upper lip structure
along one or
more edges of at least some of the openings, the lip structure extending into
its respective
opening, wash out can be limited.
[0012] By providing the bottom wall structure of each of the multiplicity
of the
four-sided bridge units with a recessed portion, a low flow channel through
which marine
life can travel is created.
BRIEF DESCRIPTION OF THE DRAWINGS
[0013] Fig. 1 is a perspective view of one embodiment of a four-sided
bridge unit;
[0014] Fig. 2 is an end elevation of the bridge unit of Fig. 1;
[0015] Fig. 3 is a cross section along line 3-3 of Fig. 2;
[0016] Fig. 4 is bottom view of the bridge unit of Fig. 1;
[0017] Fig. 5 is a cross-sectional view of two bridge units of Fig. 1
arranged edge
to edge;
[0018] Fig. 6 is an enlarged partial view of the cross-section of Fig. 5;
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[0019] Fig. 7 shows a partial cross-section of an embodiment of a unit
with both
upstream and downstream facing lips;
[0020] Fig. 8 shows a partial cross-section of an embodiment of a unit in
which the
beams all have a common height;
[0021] Figs. 9 and 10 show perspective views of another embodiment of a
four-
sided bridge unit in which continuous haunches are provided in the corners
where the
bottom wall meets the side walls;
[0022] Fig. 11 is a perspective view of yet another embodiment of a four-
sided
bridge unit;
[0023] Fig. 12 is an end elevation of the bridge unit of Fig. 11;
[0024] Fig. 13 is a cross section along line 13-13 of Fig. 12;
[0025] Fig. 14 is bottom view of the bridge unit of Fig. 11;
[0026] Fig. 14A is a partial cross-section along line 14A of Fig. 14;
[0027] Fig. 15 is a perspective view of still another embodiment of a
four-sided
bridge unit;
[0028] Fig. 16 is an end elevation of the bridge unit of Fig. 15;
[0029] Fig. 17 is a cross section along line 17-17 of Fig. 16;
[0030] Fig. 18 is bottom view of the bridge unit of Fig. 15;
[0031] Figs. 19A-B show another embodiment of a bridge unit;
[0032] Fig. 20A-C show another embodiment of a bridge unit;
[0033] Fig. 21A-C show another embodiment of a bridge unit;
[0034] Fig. 22 shows a plurality of four-sided units arranged along a
water flow
path; and
[0035] Fig. 23 shows a schematic end elevation of the system of Fig. 22
as buried.
DETAILED DESCRIPTION
[0036] Referring to Figs. 1-4, a four-sided precast concrete bridge unit
10 is shown.
In the illustrated embodiment bridge unit 10 is formed by a generally
horizontal extending
bottom wall 12, substantially vertically upward extending side walls 14 and 16
at the ends
of the bottom wall and a top wall 18 having a generally arch-shaped
configuration.
However, four sided bridge units having top walls other than arch-shaped
(e.g., flat top
walls) are also contemplated. Likewise, side walls other than vertical are
possible. As
used herein, the terms "length" and "span" of an individual unit or portions
of the unit
refers to a horizontal dimension extending parallel with the direction of
arrow 20 (which is
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substantially perpendicular to a horizontal through axis 22 of the unit) and
the terms
"width" and "depth" of the individual unit or portions of the unit refer to a
horizontal
dimension extending parallel to the through axis 22. As used herein the term
"arch" and
"arch-shaped" when referring to the top of an arch unit means a curved shape
(including
constant radius curves, curves with multiple radii, curves with continuously
varying radius)
or any top wall shape that is higher in the middle of the top wall as opposed
to where the
top wall meets the side walls (e.g., an inverted V-shape or a combination of
three or more
planar segments angularly arranged with respect to each other to produce a
vaulted top wall
or a combination of curved segments and flat segments that produce a vaulted
top wall).
[0037] The bottom, top and side walls are preferably precast as a single
monolithic
structure in a single casting operation. However, in certain implementations,
one or more
walls may be cast separately and then connected together by suitable
connecting structure
(e.g., reinforcing bars or by casting one or more elements separately and then
placing that
cast element in the formwork that is used to cast the final structure).
[0038] The bottom wall 12 of the unit 10 is shaped and configured to
facilitate both
sedimentation within and passage of marine life once the unit is installed.
Specifically, the
bottom wall 12 includes a plurality of elongated, spanwise extending through
openings that
extend completely through the thickness of the bottom wall 12. As shown, each
elongated
opening 24 has a length Lo that is at least about sixty percent of the overall
width of the
unit Lu (e.g., Lo is at least about 70% of Lu, such as for example, between
80% and 95% of
Lu). However, other variations are possible. Intermediate beams 26 separate
the elongated
openings 24 and serve to maintain a rigid connection between the lower ends of
the side
walls 14 and 16. Edge located beams 28 are also provided, thereby providing a
continuous
peripheral support surface at the lower side of the bottom wall. The lower
surface of each
beam 28 is preferably in common plane with the continuous peripheral support
surface to
provide added stability and distribution of loads. As shown, roughly about 40%
to 60%
(e.g., about 45% to 55%) of the lower side of the bottom wall makes up the
support or
resting surface of the bridge unit and the remainder (about 60% to 40%) is
open via the
openings 24. However, other variations are possible. Lengthwise extending
reinforcement
may be provided in each of the beams for structural integrity, with some
continuity
provided between that reinforcement and the reinforcement of the vertical side
walls.
[0039] As seen in Fig. 3, where the anticipated water flow direction
through the
bridge unit is shown by arrow 30, the combination of the beams 26, 28 and the
openings 24
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are configured to promote sedimentation at the bottom of the bridge unit.
Specifically, the
beams 26 and one of the beams 28 are formed with a lip structure 32 and 34
that overhangs
the adjacent opening 24 and extends from the beam in an upstream direction.
Also, one or
more of the beams 28 has a thickness or height that exceeds that of the
adjacent beams 26
and/or 28. The effect of this configuration is best described with reference
to Figs. 5 and 6,
where Fig. 5 shows two units 10 in edge to edge relationship as such units
would typically
be installed on a job site and Fig. 6 shows an enlarged partial view with a
flow pattern.
[0040] As seen in Fig. 5, the edge located beams 28" (located at the
upstream flow
edge of the units) lack any upstream facing lip structure while the edge
located beams 28'
(located at the downstream flow edge of the units) incorporates an upstream
facing lip
structure. In this manner, when two units 10 are installed edge to edge, there
is no lip
structure to interfere with the placement and the adjacent beams 28' and 28"
combine to
form effective beam that is similar in overall configuration and size to
intermediate beam
26'. In this regard, the width of the beam structures 28' and 28" is
preferably smaller than
the width of beam structures 26' and 26" (e.g., on the order of about 50% to
about 60% of
the width of beam structures 26' and 26") so that the overall width of the
effective beam is
more consistent with the overall width of the beams 26' and 26". The height of
beams 26"
is greater than the height of beams 26', 28' and 28" as shown. Beams 26', 28'
and 28" have
the same thickness or height and beams 26" may have a thickness or height that
is about
110% to about 140% greater (e.g., about 120% to about 130% greater). However,
variations are possible. The width WL of the lip structure may be on the order
of about
10% to 20% of the overall width Wo of the opening 24. In the illustrated
embodiment, a
tapered surface 36 connects the vertical side surface 38 of the beam with the
protruding
edge of the lip.
[0041] Referring to Fig. 6, as water flows through the units the higher
beams tend
to reduce the velocity in the vicinity 40 of an opening 24 which tends to
cause sediment to
drop out of the flow and into the opening. The lip structure 32 helps prevent
washout of
any sediment that builds up in the openings 24. The lip structures 32 and 34
of the shorter
beams 26' and 28' also help prevent washout in respective openings and creates
respective
areas 42 and 44 of lower velocity that can promote sedimentation.
[0042] In the illustrated embodiment, the connection of every other beam
to the
vertical side wall includes a haunch 46, which may include reinforcement, to
resist the
moment loads in the corners. Placing the haunches in a spaced apart manner,
rather than
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providing a continuous haunch, can also help promote sedimentation. However,
continuous haunches are also contemplated for some applications, as reflected
in the
embodiment of Figs. 9 and 10. In this embodiment, the relative length of the
slotted
openings 24 (as compared to overall length of the unit) is smaller than that
shown in Fig. 4
in order to accommodate the haunch 46. Moreover, Figs. 9 and 10 show a four-
sided
bridge unit with a flat top wall structure rather than an arched top wall
structure.
[0043] While the embodiment of Figs. 1-6 contemplates upstream facing
lips only,
in an alternative embodiment downstream facing lips may also be provided on
the beams as
shown in Fig. 7. Likewise, embodiments in which all the beams have a common
height are
contemplated, as shown in Fig. 8.
[0044] Referring again to Figs. 1, 2 and 4, and regardless of the
relative height of
the plurality of beams, each of the beams may be formed with a section 48 of
reduced
thickness to create a low flow channel through the unit, making it easier for
marine life
(e.g., fish) to travel through the unit. The reduced thickness sections 48 may
be formed
without any lip structures.
[0045] An alternative embodiment of a four-side bridge unit 50 adapted
for
sedimentation is shown in Figs. 11-14. As shown, the bottom wall 52 of the
bridge unit 50
includes a plurality of openings 54. The openings are arranged in a plurality
of lengthwise
extending rows 56 and 58, with the rows 56 and 58 arranged in an alternating
and
staggered relationship that provides some nesting of the openings of one row
into the
spaces between the openings of another row. The openings are distributed along
a
lengthwise extending mid-portion Lo of the bottom wall 52 that represents
between about
50% to about 80% of the overall length Lu of the bottom wall of the unit. In
this manner,
the bottom wall lacks any openings in roughly about the first 10% to 25% of
the extent of
the bottom wall from its ends. Reinforcement 60 may be located in this area
for structural
integrity. Likewise, as the edges of the bottom wall are continuous,
lengthwise
reinforcement 62 may be included along such edges as well. About 75% to about
90% of
the bottom wall in the mid-portion Lo may be open space, while only about 55%
to about
70% of the overall area of the bottom wall (as viewed from the bottom) may be
open space.
As shown in Fig. 14A, the openings 54 may include lip structure to promote
sedimentation
and reduce washout effects. The lip structure may be upstream facing lip
structure 66,
downstream facing lip structure 64 and/or lengthwise facing lip structure 68.
[0046] A further embodiment of a four-sided bridge unit 70 is shown in
Figs. 15-
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18. In this embodiment the openings 74 of the unit actually include rows of
partial
openings along each edge. The partial openings 74' are preferably about one
half the size
of a regular opening such that when one unit is abutted with another unit the
partial
openings combine to effectively form an opening similar in size and shape to
the openings
74. The mid-point arrangement of the openings along the length of the bottom
wall 72 may
be similar to that of the embodiment of Figs. 11-14, with reinforcement 76 in
the end areas
of the bottom wall 72. However, due to the edge openings 74', no reinforcement
is
provided in the mid-section where the openings are located. The openings 74 of
the unit 70
may also include lip structure as described relative to Fig. 14A.
[0047] It is to be clearly understood that the above description is
intended by way
of illustration and example only and is not intended to be taken by way of
limitation, and
that changes and modifications are possible. For example, other possible unit
configurations are reflected in Figs. 19A-B, 20A-C and 21A-C. For reference,
the unit 90
of Figs. 19A-B includes lengthwise extending openings 82 having ends adjacent
the side
walls 84, alternatingly raised 86 and lowered 88 beams and upstream facing
lips, with no
haunches or gusseting between the bottom wall and the side walls. The unit 90
of Figs.
20A-C is similar to that of Figs. 19A-B but also includes reduced thickness
sections in the
beams to provide a low flow channel 92. The unit 100 of Figs. 21A-C includes
beams and
slots with ends spaced from the side walls, and no haunches or gussets, such
that the corner
areas between the bottom wall and the side walls form low flow areas.
[0048] Fig. 22 shows a plurality of four-sided concrete bridge units,
which could be
any of the unit configurations previously described, in abutting relationship
to create a
surrounded pathway tunnel 110. One end 112 of the tunnel is located upstream
along a
water path 114 and an opposite end 116 of the tunnel is located downstream
along the
water path 114. Fig. 23 shows the units in profile as buried in earthen
material 118. Fig.
23 could also represent a series of buried units used for the purpose of storm
water
collection, with infiltration into the surrounding earth occuring through the
openings in the
bottom walls of the units.
[0049] Other embodiments are contemplated and modifications and changes
could
be made without departing from the scope of this application.
[0050] What is claimed is:
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