BOLIVIA BRIDGE MANUAL
Brianne Connolly
Ben Gagne
Catherine Joseph
Magdalena Kelleher
TABLE OF CONTENTS
Justification for specific dimensions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
Materials List . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
Flow rate calculations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
Force calculations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6-10
Details . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11
Construction sequence and timeline . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .12
Operation and Maintenance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13-14
2
JUSTIFICATION FOR SPECIFIC DIMENSIONS
Culvert size:
We chose to use the 2 meter diameter culverts and cut them in half so we could have
optimal flow and reduce our material costs. The culverts will each be 4.556 m long. This
will allow for a 3.048 m roadway as well as a retaining wall with a 45° angle top, while
still allowing 0.5 m of culvert extending beyond the wall.
Width of the Roadway:
Our roadway is 3.048 meters (10ft) wide; an appropriate width for the level of traffic of
the site. Making the bridge too wide would create unnecessary costs, however a bridge
that was too narrow would not meet the purpose of the bridge. We concluded that 10
feet would be a suitable width for the bridge.
3
MATERIALS LIST
Item
2000mm metal pipe
culverts
Amount
Total Cost
Acquired from:
6 (sliced in half)
$8615
Oruro
4.556m long
Portland Cement
Oruro
Aggregate (concrete)
Soil
Oruro
29.0442
m3
--
Riverbed excavation
$220
Oruro
--
--
Local Scrap Wood
120 L Gas Concrete mixer
1
$1000
Oruro
Level (18”)
2
$5
Oruro
20-30
$245-$365
Oruro
5
$430bs
Oruro
total
Crushed Stone (Gravel)
8.092 m3
7 truckloads
Wood – concrete forms
Equipment Needed
Shovels (flathead)
Wheelbarrows
Notes:
Total Costs were converted from “bs” to “$.”
We overestimated on all costs by rounding up to the nearest five or zero on all
estimates. Also, we will have more than enough soil from the riverbed excavation for
filling in around the culverts.
Assumptions for culverts:
We assumed the price was in dollars and that a 2m diameter pipe would cost 1.5 more
that a 1m diameter pipe. We also assumed the cost was per meter. Our cost does not
include cost of cutting or delivery.
4
FLOW RATE CALCULATIONS
To calculate the volumetric flow rate of the river we used Manning's formula,
 k  2/3
V    Rh S 1 / 2
n
where k is equal to 1.0 because we're using SI units, n is the manning coefficient of
roughness, Rh is the hydraulic radius, and S is the slope of the riverbed. We used the
manning coefficient of 0.035 which is used for floodplains, pastures, and farmlands.
The hydraulic radius is equal to A/P, where A is the cross sectional area and P is the
wetted perimeter. We calculated the river's cross sectional area with AutoCAD, which
yielded an area of 18.9554 m2, as well as the wetted perimeter, which was 56.9150 m.
The slope S was determined by using a point on the cross section and a point prior to it.
This equaled 0.0455 m/m.
By plugging in these numbers into Manning's formula, we found the velocity of the river
to be 2.9 m/s. We then took this velocity and plugged it into the continuity equation:
Q = AV, where Q is flow rate, A is the cross sectional area, and V is the velocity. The
final flow rate came out to be 55.5062 m3/s.
Once we determined the max flow rate of the river, we looked into figuring out the flow
rate going through the half culverts to make sure we had a sufficient number. To do
this, we used Dr. Kabala's colebrook.m file to calculate volumetric flow rate allowed by
semi-circular, 2-meter diameter culverts for our riverbed conditions.
This yielded a flow rate of 5.13568 m3/s per culvert. Based on this number, we
determined that 10.8 culverts were needed. Therefore our ultimate design has 11 halfculverts.
5
FORCE CALCULATIONS
6
7
8
9
10
DETAILS
Detailed description of Construction Timeline Step 4:
Our sequence for placing the culverts will be a sequential and simultaneous process.
The first stage of the process will be to set the form for the first two strip footings, pour
the concrete, place rebar, and place the first culvert in the forms. The concrete will be
poured into the first footing, securing the culvert in place. The form for the first section
of the concrete wall will be cut and placed, and the concrete for the wall will be poured.
Once the wall has had time to set, a second crew will begin filling around the culvert
with compacted soil while the first crew begins on the third strip footing and placing the
second culvert. Once the second footing has been poured and the concrete wall has
been poured and had time to set, the soil crew will follow behind. This process will
continue as the bridge is built across the river. By the time both crews reach the other
side, the strip footings, culverts, concrete wall, and compacted soil fill will all be in
place. The construction process will then continue with the placing of the angled
concrete wall/curb. (Please refer to CONSTRUCTION SEQUENCE AND TIMELINE)
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CONSTRUCTION SEQUENCE AND TIMELINE
Task
Day
1. Obtain materials on list
1
2. Have pipes cut and delivered
1
3. Dig out riverbed to achieve flat bed
1
4. Sequence for placing culverts
15
a. Set forms for strip footing
b. Pour concrete (partial) and place rebar
c. Place culverts in forms
d. Pour concrete in forms (securing culverts)
e. Cut and place concrete retaining wall forms(inlet & outlet)
f. Pour concrete in wall forms
g. Place soil fill between retaining walls (compacted)
5. Place angled concrete wall/curb
23
6. Place crushed stone to prep for roadway
26
7. Lay concrete roadway
28
12
OPERATION AND MAINTENANCE
Safety factors:
We have added safety factors in various aspects of our design. We must also consider
other failure modes for culverts and prepare for these failures in the chance that they
occur. The most common failure modes for culverts are insufficient capacity, plugging,
and embankment erosion.
Preventative Measures
Insufficient capacity:
-
Install armoring and wing-walls at the entrance and outlet of the culvert to
increase pressure of the flow through culverts.
-
Install a relief culvert.
Plugging:
-
Install an entrance debris deflector.
-
Install a sediment catch basin upstream.
-
Install a relief culvert.
Embankment Erosion:
-
Place riprap to reduce embankment erosion.
-
Shape culvert entrance to match embankment slope.
-
Construct flared end section to direct flow.
How Often:
Maintenance of the bridge will require periodic bridge inspections. At the time of
completions, an initial inspection will occur. The purpose of this inspection is to
reevaluate site conditions and identify deficiencies that may not have been identified
during construction. This includes reevaluation of erosion, debris guards, and grades of
banks.
Routine inspections will be regularly scheduled, occurring every two years during the dry
season. Inspection of equipment of bridge evaluation tools will occur first (cleaning
tools, visual aid tools, measuring equipment, safety equipment, etc.). The bridge
inspector will inspect the bridge for fractures, structural deficiencies, failures in the
metal culverts, and will identify changing conditions.
Interim inspections will occur every six months to identify any quickly changing
conditions with the bridge. These inspections may be performed by local (or district)
trained inspectors. During these inspections, the inspector should also remove any
debris from the debris guards to allow for maximum flow through the culverts.
13
Damage inspections will be performed as needed, generally as a result of environmental
damages, fires, collisions, or severe floods. Underwater inspections may be performed
as needed during low water seasons. Wading techniques may be used for this
inspection. In-depth inspections may also be performed to investigate deficiencies
found during routine inspections.
It will also be useful to develop in information database containing all data gathered
during bridge inspections. This will help in monitoring load-bearing capacities of the
bridge.
Operation Costs:
Cost to operate the bridge will be composed of pay for a bridge inspector and funds for
future bridge repairs. This will be proportional to the average pay rate for bridge
inspectors in Bolivia and the cost of materials for the future repairs necessary. There
will be no daily operation cost for the bridge.
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