Transcript Bill Stone-

Live Load Effect in Reinforced
Concrete Box Culverts Under Soil Fill
Sarah Orton, Erik Loehr, Andrew Boeckmann, and Garrett Havens
University of Missouri
1
Research Motivation
Load Rating required for all bridge size culverts (span >
20ft)
In the case of culverts under deep fill, effect of dead load
much greater than live load – negligible live load effect
Missouri has approximately 3000 culverts. About 700
(23%) have fill depths greater than 6 ft.
Impact – significant reduction in number of man hours
required to load rate culverts and reduction of
unnecessary load posting of culverts
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2
Research Methodology
10 culverts were selected for testing
Culverts ranged in fill depth from 2.5 feet to 13.5 feet
Determine the fill depth which Live Load becomes
negligible
Live Load utilized a Dump Truck loaded and parked at
specific locations to maximize strains
Effects of loadings were recorded via strain transducers,
and an accelerometer attached to the underside of the
culverts
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3
Research Methodology
Tests were conducted in Two Rounds.
Five culverts with similar geometrics but varying fill
heights made up first round
Second round focused on various cell sizes, arrangements
and design loads at depths near where live loads become
negligible during the first round
Computer models of each culvert were created to fully
analyze the results
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4
Culverts
10 culverts with fill depths from 2.55 ft to 13.25 ft were
tested
Culverts were built between 1954 and 2001
Design Load H10 and H15
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Bridge #
County
Route
Cell
Size
Year
Built
Design
Load
Design
Fill
Actual
Fill
Clear
Height
Slab
Thickness
Wall
Thickness
Skew
2.75
9.5
11
11.5
0
5.0
7.5
10.5
8
0
8
9.75
10
11
13.5
15.5
9.5
9.5
10
0
15
15
8
7.5
6
10
8
11
10
10.5
12
11
8
8.5
8
9
7.5
15
0
10
0
10
L0525
Callaway
RT F E
2x12'
1953
Phase 1 Culverts
H 15
2.58
N0936
Pettis
RT J S
2x12'
1960
H 15
A2869
R0015
P0622
Macon
Boone
Callaway
MO 3 S
RT NN
RT O E
2x11'
2x13'
2x12'
1972
1962
1954
A6330
N0793
N0502
X0749
N0059
Audrain
Montgomery
Montgomery
Boone
Gasconade
RT AA
RT J S
MO 94
RT O S
RT Y E
3x14
2x14
3x15
2x12
2x10
2001
1962
1958
1947
1957
H 15
6
6.48
H 15
7.8
8.15
H 10
11.51
13.25
Phase 2 Culverts
3
2.547
1.82
2.555
3.82
4.491
H 10
5.11
6.35
H 10
6.1
8.25
5
4
Instrumentation
Each culvert was instrumented with 12 strain
transducers, 11 LVDTs , and one accelerometer to
capture maximum strains and displacements as truck
moved over culvert
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6
Phase 1
Phase II
Live Loading
Truck loaded to approximately 50 kips was positioned in
7 static positions above the culvert to induce maximum
strains and displacements in gages
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Position 1
Centered over
secondary span
Position 2
Rear tire in
middle of
secondary span
Position 3
Centered
middle wall
7
Position 4
Front rear tire
middle primary
span
Position 5
Centered over
primary span
Position 6
Rear tire in
middle of
primary span
Position 7
Centered over
far wall
Results from data - Strains
Maximum strain measured in top slab vs fill depth
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1.0 E-05 ~ 40 psi
8
Results from data - LVDT
Maximum displacement vs fill depth
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9
Conclusions
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Culvert testing was successful and reasonable trends
found in both strain and displacement data
Culvert design is very conservative, especially at
shallower fill depths
A possible point for cutoff of load rating is around 6 ft.
10
Future Research
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NCHRP Study selected to evaluate Live Load Impact on
Culverts
Expand study to other states?
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11
Reduce need for load rating in deep fill culverts
Improve load rating procedures
Reduce over-conservatism in design of culverts by
better understanding load distribution through soil and
pavement