Note: Descriptions are shown in the official language in which they were submitted.
CA 0222~729 1997-12-23
ARCH BRIDGE FOR WATER CROSSING
FIELD OF THE INVENTION
This invention relates to a novel pre-assembled arch bridge
design. More particularly, this invention pertains to a novel design of
arch bridge which is environmentally friendly, and can be pre-assembled
and shipped cost-efficiently to remote locations and used in the construc-
tion of roads across creeks and rivers, with minimum damage caused to
river and stream beds and fish habitat.
BACKGROUND OF THE INVENTION
Building new forest access roads encompasses a number of
problems not found in normal roadbuilding. Sites are remote and
construction materials are at a premium. Roadbed preparation varies
from excavating muskeg to blasting bedrock. Environmental concerns
are becoming the most important aspect in opening up Canada's forests.
Permanent water crossings on access roads and logging roads
in remote areas are usually round corrugated steel pipe culverts or
bridges built of pressure treated timber and steel beams. In selecting the
type of structure, the owner tries to meet several objectives: to carry
road traffic safely, incur low initial cost, incur minim~l m~intenance and
cause minim~l impact on fish habitat. The various governmental bodies
review and approve all water crossings on Crown land to ensure that the
structures are safe for public use and environmental impacts are kept
within acceptable bounds.
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Keeping streambeds natural in fish spawning areas is a major
concern of fisheries biologists. Building a full round structure, and
burying the invert can be costly and difficult and can significantly disrupt
the streambed. Often the lower third of these structures is supposed to
5 go where there is bedrock. Blasting is costly, and definitely not green.
A type of remote area creek or river crossing is an arch
culvert with steel plate footings. The arch culvert is typically a semi-
circular corrugated steel shell. The open bottom is positioned down-
10 wardly and the corr lg~te~l steel shell forms an arch over the stream. Inaddition to the regular semi-circular shape, a low profile section is
available to reduce road fill. Arch culverts have generally required a
cast-in-place concrete footing wall to support the arch. Arch culverts are
preferred by fisheries biologists over round pipes because they m~int~in
15 the natural stream substrate and flow velocities simulate those in the
natural channel. The arch shape allows the required water opening to be
provided with a lower road height than would be the case with a round
pipe, thus a saving in fill materials. However, arch culverts have not
been a favoured type of structure on access roads because of the
20 difficulties associated with pouring concrete at remote locations, often
below water level.
SUMMARY OF INVENTION
The invention is directed to a pre-engin~ered, pre-assembled
arch bridging system for enabling bridges to be constructed across
environmentally sensitive streams comprising: (a) an arch member; (b)
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a connection flange member adjoining each side of the base of the arch
member; (c) a footing plate member positioned at the base of each side
of the arch member, below the respective connection flange member; and
(d) a lateral cross-strut member positioned below the respective footing
5 plate members and connecting the respective footing plate members
together.
The arch member can comprise at least two arch sections
axially connected together in series. The arch member can have a 180~
10 periphery. The arch section can be formed of hot dip galv~ni7e~1
corrugated steel. The two bases of the arch can have connection flanges
which can be corr~ te~l.
The footing plate members can have an "L-shape" cross-
15 section, a "U-shape" or "Z" shape cross-section. The footing plate
members can be constructed of corrugated plate.
The cross strut members can have an "L-shape" cross-section
or a "U-shape" cross-section.
The arch section members, the connection flange members,
the footing plate members and the cross strut members can be connected
together by bolts or by welding. The footing plate members can be
connected end-to-end by splice plates.
CA 0222~729 1997-12-23
The arch section members, connection flange members,
footing plate members and the cross strut members can have pre-punched
bolt holes for receiving the bolts.
The cross struts and the footing plate members can be
"twinned" to provide greater strength.
BRIEF DESCRIPTION OF DRAWINGS
In drawings which illustrate specific embodiments of the
invention, but which should not be construed as restricting the spirit or
scope of the invention in any way:
Figure 1 illustrates an isometric view of an arch bridge
according to the invention.
Figure 2 illustrates a plan view of an arch bridge according
to the invention.
Figure 3 illustrates a section view taken along section line A-
A of Figure 2.
Figure 4 illustrates an enlarged detail of circle area "B" of
Figure 3.
Figure 5 illustrates an enlarged detail of circle area "C" of
Figure 3.
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Figure 6 illustrates an enlarged detail of circle area "D" of
Figure 2.
Figure 7 illustrates an end view of an alternative design of
5 arch bridge with dual footings at each base.
Figure 8 illustrates an enlarged view of the dotted oval area
of Figure 7, with Option A footing plate comprising back-to-back L-
shape footing plates on a cross strut.
Figure 9 illustrates an enlarged view of the dotted oval area
of Figure 8 with Option B footing plate comprising back-to-back "L-
shape" footing plates on a short cross strut with a long strut on the
inward facing "L-shape" footing plate.
Figure 10 illustrates an enlarged view of the dotted oval area
of Figure 8 with Option C footing plate comprising an inverted "L-shape"
footing plate coupled with an upright "L-shape" footing plate and short
and long struts.
DETAILED DESCRIPTION OF SPECIFIC
EMBODIMENTS OF INVENTION
Figure 1 illustrates an isometric view of an arch bridge
25 according to the invention. As seen in Figure 1, the arch bridge 2 is
constructed of a linear series of semi-circular full-periphery hot dip
galv~ni~e~l corrllg~te-l steel arch sections 4, which are positioned with a
CA 0222~729 1997-12-23
common axis and bolted together along adjacent intersecting connection
slots 6. The bolts 7 are secured in spaced series through pre-punched
holes along the lengths of the respective intersecting connection slots 6.
In this way, an arch bridge of any prescribed length can be constructed,
5 simply by bolting together the required number of semi-circular full-
periphery arch sections 4 in series.
The lower ends of the arch sections 4 are finished with
corrugated connection flanges 8 with pre-punched bolt holes. These
10 corrugated connection flanges 8 provide lateral reinforcing strength to the
lower edges of the arch sections, and retard lateral bending. Thus, the
dimensional integrity of the arch sections 4 is sustained.
Each corrugated connection flange 8 rests on and is
15 connected to a respective L-shaped galvanized steel footing plate 10. The
flanges 8 are pre-punched and provide an economical connection
mechanism with the underlying footing plates 10. The corrugated
connection flange 8 on each side of the base of the arch section 4 is
bolted to the respective footing plate 10 by a series of bolts 7, preferably
20 of the same size as the bolts 7, which are used to connect the series of
arch sections 4 together at the respective intersecting connection slots 6.
In this way, only one size of bolts is required for assembling the entire
arch culvert 2.
The respective footing plates 10 in turn rest on and are
connected to cross struts 12, which are located in lateral series along the
open base of the arched sections 4. Preferably, there is a cross strut 12
CA 0222~729 1997-12-23
for every second arch section 4. However, the number of cross struts
will vary depending on load conditions that the arch bridge must meet.
The cross struts 12 are formed of galvanized angle steel. The footing
plates 10 are bolted to the cross struts 12 at appropriate locations by
5 welding or by bolts, which can be of the same size as bolts 7 used to
connect together the series of arch sections 4, and to connect the flanges
8 to the footing plates 10. Alternatively, the bolts can be of a different
size. The series of cross struts 12 provide lateral stability, prevent
erosion of the footing plates 10 after installation, m~int~in the span and
10 rise of the structure during transport and backfillin~, and add bending
strength to the steel footing plates 10.
To provide additional linear stability to the arch bridge 2, a
steel stiffening channel 14 is bolted along the crest of the length of the
15 arch sections 4. Thus, the combination of the stiffening channel 14,
corrugated connection flanges 8, and footing plates 10 ensure a strong
dimensionally stable arch bridge 2, notwithst~n-lin~ that it has an open
bottom. Nonetheless, the open bottom is important because it improves
fish passage and m~int~in~ aquatic habitat, something that standard
20 corrugated steel pipe does not do.
Figure 2 illustrates a plan view of the arch bridge 2. In
particular, Figure 2 illustrates how the series of arch sections 4 are
connected together at the intersecting connection slot lines 6. The
25 corrugated connection flanges 8 on either side of the arch sections 4 are
bolted by bolts 7 to the respective parallel pair of footing plates 10.
Figure 2 also illustrates the lateral cross struts 12 which are connected
CA 0222~729 1997-12-23
between the parallel pair of footing plates 10 by bolts 7, and are arranged
in series along the length of the arch bridge 2. The longitu~lin~l
stiffening channel 14, which is bolted at the crest of the series of arch
sections 4 is illustrated in dotted lines. Figure 2 also illustrates rectangu-
5 lar splice plates 16, which are formed of hot dipped galvanized steel andare welded at the connecting ends of the respective parallel pair of
footing plates 10. As with the series of arch sections 4, which can be
connected together at the connection slots 6 to construct arch bridges of
any specified length, the combination of footing plates 10, which are
10 connected together by splice plates 16, enable the footing plates 10 to be
of any prescribed length.
Figure 3 illustrates a section view taken along section line A-
A of Figure 1. As seen in Figure 3, the arch section 4 is a precise semi-
15 circle sp~nnin~ 180~. This design ensures that the base regions on eachside of the arch section 4 are vertical, which ensures maximum load
bearing capability for the arch. The corrugated connection flanges 8
protrude laterally from each side of the base of the arch section 4 and
provide lateral strength. The flanges are pre-punched with holes to
20 receive assembly bolts 7. As seen in Figure 3, the "L" footing plates 10
are positioned at the base of each side of the arch section 4. The pre-
punched flanges 8 provide a convenient method of securing the arch 4 to
the footing plates 10. The pair of footing plates 10 in turn rest on and
are connected to the lateral cross strut 12. The "J" shaped stiffening
25 channel 14 is shown at the crest of the arch section 4.
CA 0222~729 1997-12-23
Figure 4 illustrates an enlarged detail of circle area "B" of
Figure 3. The design and dimensions of the footing plate 10 and the
cross strut 12 are shown in clear detail. The bolt (not shown) passes
through pre-drilled holes in corrugated connection flange 8, footing plate
5 10 and cross strut 12 along "C/L bolt" centreline shown in Figure 4.
Figure 5 illustrates an enlarged detail of circle area "C" of
Figure 3. Figure 5 is similar to Figure 4, but is reversed since it depicts
the opposite side of the base of the arch section 4. The construction and
10 connection of the corrugated connection flange 8, footing plate 10 and
cross strut 12 as illustrated in Figure 5 is the same as that discussed
previously in association with Figure 4.
Figure 6 illustrates an enlarged detail of circle area "D" of
15 Figure 2, and in particular, clearly illustrates how a pair of footing plates 10 are connected end to end, by rectangular splice plate 16, which is
welded in place. Alternatively, splice plate 16 can be bolted to the
adjoining ends of the pair of footing plates 10. A cross strut 12 is also
visible in Figure 6.
Figure 7 illustrates an end view of an alternative design of
arch bridge with dual footings at each base.
Figure 8 illustrates an enlarged view of the dotted oval area
25 of Figure 7, with Option A footing plate comprising back-to-back L-
shape footing plates on a cross strut.
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Figure 9 illustrates an enlarged view of the dotted oval area
of Figure 8 with Option B footing plate comprising back-to-back "L-
shape" footing plates on a short cross strut with a long strut on the
inward facing "L-shape" footing plate.
Figure 10 illustrates an enlarged view of the dotted oval area
of Figure 8 with Option C footing plate comprising an inverted "L-shape"
footing plate coupled with an upright "L-shape" footing plate and short
and long struts.
The alternative designs of double footing plates enable the
footing plates to be expanded to cover more area (with higher loads or
to suit low load bearing situations) or to be strengthened by coupling the
footing plates. Also, the short and long struts enable the overall arch
bridge to be strengthened so that dimensional stability is increased.
The arch bridge 2, according to the invention, offers the
following advantages over conventional bridging methods:
1. The arch bridge 2 retains the natural stream bottom and
preserves aquatic habitat.
2. Each structure can be completely pre-assembled in fully-
equipped assembly and fabrication shops to reduce field
installation time and overall project costs.
3. The arch bridge is very versatile and can be pre-engineered
to meet a variety of live loads under a wide range of covers.
CA 0222~729 1997-12-23
4. The cross strut design 12 m~int~in~ the span and rise of the
structure during transport and installation, reduces the
potential for galvanized plate footing scour, and improves
fish passage.
5. All components are hot-dipped galvanized to ensure long-
lasting performance.
6. The open bottom elimin~tes the problem of pipe bottom
corrosion which often follows abrasion of the galv~ni7e~1
plating by sand and gravel.
The aggregate sum of the components of the arch bridge
design according to the invention, when pre-assembled and bolted
together, forms a pre-engineered bridging system which m~int~in~ shape
and rise, reduces bending of footing plates during shipping and creates
15 an environmentally friendly structure that reduces disturbance to
streambeds, m~int~in~ aquatic habitat and offers a cost effective method
of bridging streams.
Arch bridges according to the invention are recommended at
20 sites with less than a 5% gradient and offer a minimllm allowable bearing
capacity of 160 kPa. The arch culvert 2 is not recommended in areas
prone to unpredictable flows or in high velocity streams.
Typical Standard Specifications
Footings Plates: 343 mm wide x 6.4 mm thick unequal-leg angles
Cross Struts: Min. 112 mm x 79 mm angle
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Arch Sections: 610 mm wide sections with 68 x 13 mm corrugations,
51 mm wide flanges, and pre-punched 11 mm dia.
slotted connection holes; or 125 mm x 25 mm, or 76
mm x 25 mm ~nmll~r or helical full periphery sec-
tions.
Option: 152 mm x 51 mm corrugations.
Stiffening Channel: 116 mm x 76 mm x 40 mm complete with pre-
punched connection holes.
Spans can range from 400 mm to 3600 mm.
A11 components to CSA G401-93. Footing plates hot-dipped
galv~ni7e~1 to CSA G164. Zinc rich paint touch-up permitted after
assembly of components.
CA 02225729 1997-12-23
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CA 0222~729 1997-12-23
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Installation
Prior to placement of the arch bridge 2, which will be sold
under the trade-mark Mini-Span, the footing plate foundation should be
5 uniformly graded, with good quality granular material to ensure even
footing support throughout the structure. Once the stream bed is
prepared, the pre-assembled arch culvert 2 can be lowered into position.
Upon placement, the structure must be backfilled in 200 mm uniform lifts
with a uniformly graded good quality granular backfill and compacted to
10 95% standard Proctor density. Proper installation is essential to ensure
long term performance.
EXAMPLES
Armtec Construction Products has produced and tested a
prior experimental arch culvert design that used a footing plate made of
thick gauge (7 mm) corrugated steel plate. No concrete footings were
needed as the steel plate footings of the arch design rested directly on the
soil. The Ontario Ministry of Natural Resources (OMNR) was involved
in the installation of two crossings using this experimental design.
Whitewood Creek Arch Culvert
This project involved the replacement of an existing decayed
timber bridge on a heavily used forest access road near Thunder Bay,
Ontario. A hydrology analysis determined that the opening size to pass
flood flows was a single 7'3" (2200 mm) diameter pipe culvert. The
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arch culvert had to have the same end area or larger. An arch size of
10'0" span by 5'3" rise by 60' long (3050 mm x 1600 mm x 18.3 m)
was selected. Due to its lower height, the arch could fit the crossing
with the existing road grade whereas using a round pipe would have
5 entailed raising the road by 2 feet (600 mm). In accordance with the
m~mlf~cturer's recommendations, the design specified a footing elevation
1'0" (300 mm) below streambed.
The arch culvert was pre-assembled in two 30 foot (9.1 m)
10 sections. It was bolted together from 0.12" (3 mm) thick multi-plate
sections. The unbalanced channel was bolted to the 27" (686 mm) wide
steel footing plate. Transverse steel cross angles measuring 4" x 4" x
3/8" (100 mm x 100 mm x 10 mm) were installed between footing plates
to facilitate shipping.
The original plan was to excavate two side trenches and
embed the footing plate 300 mm below streambed. During construction,
however, large boulders or bedrock were encountered and excavation for
the footings was not possible without blasting.
A field decision was made to leave the cross angles in place
and set the footing on the streambed. They would act as struts to resist
the lateral earth pressure. A gravel pad was prepared to fill in low areas
and ensure uniform footing support. A geotextile was laid on the outside
25 footing and foundation before backfilling to prevent any future loss of
backfill material.
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The experimental arch culvert opening provided a good
substrate for fish inhabiting the stream. The cross angles that were left
in place did not appear to block fish migration or water flow. Probably,
bedload sediment will raise the streambed elevation to cover the cross
5 angles.
Saymo Lake Arch Culvert
An experimental arch culvert installation at Saymo Lake was
10 undertaken to replace an existing 36" (900 mm) diameter culvert pipe
which had collapsed on a forest access road north of Sault St. Marie,
Ontario. The arch culvert was installed to pass water under the road
where it crosses a bay of Saymo Lake. The collapse of the original
culvert resulted in water flowing over the road causing roadbed material
15 to be contiml~lly washed downstream.
A marsh, located upstream of the installation, was considered
excellent fish and wildlife habitat and a standard culvert installation
would have resulted in the upstream water level being re~ ce~l by several
20 feet. To avoid this, the design used the upstream cofferdam as a base for
a water level control weir. The weir was protected from erosion with
rip-rap and to create a drop inlet into the culvert. Migration of fish
through the culvert was not a concern.
An arch size of 7'6" span by 3'9" rise by 44'0" long (2280
mm x 1140 mm x 13.4 m) was selected for the crossing. Pipe thickness
was 0.12" (3 mm). The arch size was chosen to allow the footing to be
CA 0222~729 1997-12-23
embedded to the required depth in the streambed while ensuring the
a~ro~liate hydraulic opening remained. The footing plate was 17" (426
mm) wide.
The installation took place over a period of three days. On
day 1, sandbags for the upstream cofferdam were prepared and all
material was transported to the size. Some pre-assembly was completed
on the first day, including the attachment of the unbalanced channel to
the strip footing sections and assembly of the 10' (3048 mm) arch ring
sections.
On the second day, the road was closed for construction.
The site was isolated and dewatered using an upstream sandbag
cofferdam and a downstream silt curtain. The road fill was removed to
the required footing grade and bottom width. Some bed preparation was
required to level the foundation near the downstream end of the culvert
installation. This was accomplished by placing a geotextile on the lake
bottom and depositing compacted granular fill in low areas. A down-
stream apron was created with rip rap placed over geotextile to match the
existing lake bed elevation. The strip footings, with unbalanced channel
attached, were lifted into position.
The pre-assembled arch sections were then placed and
connected to the unbalanced channel. In doing so, two plates were left
off to create openings or hatches for backfillinE inside the arch. Rip rap
was then placed through the hatches and distributed so that a minimum
1' (300 mm) depth of material remained between the footings. Once the
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required rip rap had been placed inside the culvert, the two rem~inin~
plates were installed to complete the arch culvert. The culvert was then
backfilled, with compaction. The road was opened to traffic at the end
of the second day.
The two experimental arch culvert designs demonstrated that
they were good alternatives to round culverts where there are fish habitat
concerns or where road fill height limitations prevent the use of a
conventional round culvert pipe.
As will be apparent to those skilled in the art in the light of
the foregoing disclosure, many alterations and modifications are possible
in the practice of this invention without departing from the spirit or scope
thereof. Accordingly, the scope of the invention is to be construed in
15 accordance with the substance defined by the following claims.
