final report on field testing and analysis of bridge ...€¦ · three crc deck-girder approach...
TRANSCRIPT
FINAL REPORT ON
FIELD TESTING AND ANALYSIS
OF BRIDGE 01496A
FOR YAMHILL COUNTY
Christopher Higgins, PhD
Mary Ann Triska
October 20, 2010
2
Bridge Description
Lambert Slough Bridge #01496A crosses Lambert Slough in Yamhill County, OR, and is
the only bridge to provide access to and from Grand Island, OR. The bridge combines
prestressed concrete girders, conventionally reinforced concrete deck-girders (RCDG), and
conventionally reinforced concrete (CRC) box girders. The drawings for the bridge are
dated 1963. There are eight spans: two prestressed girder approach spans (span lengths =
70 ft) on the west side, three CRC box girder main spans (span lengths=90, 120, 90 ft), and
three CRC deck-girder approach spans on the east side (span lengths = 64 ft). The spans
support a roadway width of 24 ft. There are 5 girder lines in the prestressed spans, four
web stems in the box girder spans, and 4 girder lines in the RCDG spans. The RCDG
girders are 14.5 in. x 54 in., uniform and prismatic except from the diaphragms to the
continuous support locations (bents 7 and 8) where the web width increases in a linear
taper. Diaphragms are located at the 1/3 points along the RCDG spans. The box girder
webs are 10 in. x 78 in., uniform and prismatic except where they increase in width at the
continuous support locations. Internal diaphragms are located at the quarter points in the
boxes along the spans. The reinforced concrete deck is 6.5 in. thick over the RCDG and
box girder spans and an asphalt wearing surface is applied to the bridge. The specified
concrete compression strength was 3300 psi and the reinforcing steel was specified as
ASTM A305 intermediate grade (nominally 40 ksi yield stress) deformed round bars.
Crack Identification and Mapping
Visual inspection of the downstream face of the exterior girders was performed to identify
cracks and select instrument locations. Flexural and diagonal cracks were observed to
correspond to those previously reported and marked on the girder surface (Burgess and
Niple 2004). No visible cracking was observed on the exterior face of the prestressed
concrete girders. The prestressed girder spans could not be completely inspected due to
growth of vegetation and access limitations near the western side of the bridge. As would
be expected, diagonal cracks were concentrated near support locations and vertically
oriented cracks were closer to midspan locations. The crack sizes, orientations, density and
3
locations correspond to similar aged bridges inspected by the investigators on other Oregon
highways and interstates.
Instrumentation of Bridge
After inspection, locations were selected for instrumentation. At selected crack locations,
strain gages and displacement transducers were installed. Crack locations were selected
based on the width and orientation of the cracks and to coincide as best as possible with
locations that were of similar distance from the face of the support. These criteria
facilitated subsequent load distribution estimates. Strain gages were installed to measure
the reinforcing steel stress at the crack locations. Strain gages were installed by chipping
into the concrete and exposing the embedded reinforcing steel at the crack locations. The
actual amount of concrete removed varied based on the concrete cover, but typical concrete
removal provided an exposed reinforcing length of approximately 3 to 4 in. overall,
centered about the crack, as illustrated in Fig. 1. The width of the excavation was
approximately 2 to 3 in. permitting preparation of the rebar surface for bonding strain
gages. The deformation pattern on the reinforcing steel was not removed to install the
strain gages, as the strain gage size (Measurements Group strain gage EA-06-062AQ-350,
with a gage length of 1/16 in. and gage factor of 2.105) permitted installation within the
deformation pattern. This strain gage was a bondable type gage with a 350 Ohm resistance.
A typical installation of a strain gage and position sensor is also shown in Fig. 1. Strain
gages applied to the reinforcing steel were installed in 7 different locations on the bridge.
Both flexural bars and stirrups were instrumented. A single surface concrete strain gage
was applied near a vertically oriented crack tip near the deck soffit as seen in Fig. 2. This
crack is the same one that crosses the two other strain gages which were applied to the
flexural reinforcing steel in the box girder. The instrumented locations are illustrated
schematically in Fig. 3. As seen here, only the downstream exterior girders/web and the
downstream interior girder/web were instrumented. Symmetry of structural responses was
assumed and test trucks were positioned as described subsequently to enable prediction of
load distribution. Displacement sensors were mounted across the cracks to monitor crack
motions. These were applied relatively close to the location of the strain gages as seen in
Fig. 1.
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The strain gages and displacement sensors were connected to a Campbell Scientific
CR9000 data logger. This is a high-speed, multi-channel, 16-bit digital data acquisition
system. Resolution for the strain measurements was greater than 5.84E-7 strain and for
displacements was 0.0001 inch. In order to reduce noise and prevent aliasing in the data,
both analog and digital filters were employed. During the ambient monitoring period, data
were sampled at 100 Hz. During controlled truck tests, data were sampled at 200 hz. The
system recorded sensor readings and converted signals into corresponding strains and crack
displacements. Data from sensors were archived for retrieval and post-processing.
Testing Methods
Two different types of live load data were collected: response under ambient traffic loading
and response under controlled truck loading. The strains and crack displacements generated
by normal traffic flow were recorded over a period of 9.57 nonconsecutive calendar days
from August 25 to September 24, 2010. The system also recorded individual event
histories when strain thresholds exceeded 50 microstrain ( at sensor location CH_8. For
each trigger event, data were recorded for several seconds prior to and following the
trigger. The four largest events recorded during the ambient traffic monitoring period are
shown in Fig. 4a, b, c and d.
Controlled truck loading tests were conducted using a heavily loaded Yamhill County
maintenance truck and trailer, as shown in Fig. 5a. The axle weights and spacing are shown
in Fig. 5b. Traffic was temporarily halted using a flagging crew so that the control truck
would be the only vehicle on the bridge during data collection. The control truck passed
over the bridge at several designated speeds and lane positions. Test speeds varied from
slow (approximately 5 mph), to fast (in the range of 30 to 40 mph). Lane locations
included placing the truck in the lane, straddling the truck over the center-line stripe, and
placing the truck in the opposite lane going the wrong direction. Lane positions and the
corresponding truck positions relative to the girder/box stem locations are illustrated in Fig.
6. During each pass of the control truck, reinforcing steel strains and crack motions were
recorded for each of the instrumented locations. Peak strain values for each of the test runs
are summarized in Tables 1a and 1b for the eastbound and westbound passes, respectively.
5
Strain ranges measured for each of the test runs are summarized in Tables 2a and 2b for the
eastbound and westbound passes, respectively. The measured time-history response data
for all instruments and loading positions and speeds for the test truck with trailer are shown
in Appendix A.
Ambient Traffic Induced Reinforcing Steel Stress
Ambient traffic-induced strains at each of the instrumented crack locations were monitored
at each bridge for a period of 9.57 days. The strain-ranges and numbers of cycles recorded
at the instrumented locations are shown in Fig. 7. The largest single strain-range measured
was approximately 135 microstrain (corresponding to 4.3 ksi) at location CH_8 (a flexural
reinforcing bar on the interior girder of the RCDG). The largest strain range measured on a
box girder was also 135 microstrain (corresponding to 4.3 ksi) at location CH_4 (a stirrup
on the box girder). The measured strain ranges were converted to stress ranges using the
modulus of elasticity of steel (29,000 ksi) and concrete (~3,625 ksi). Then, using Miner’s
Rule (Miner, 1945), the variable amplitude stresses were described as an equivalent
constant amplitude stress-range for each of the instrumented locations:
3 3 itot
ieqv SR
N
nSR [1]
where SRi is the ith stress-range, ni is the number of cycles observed for the ith stress-range,
and Ntot is the total number of cycles at all stress ranges. The equivalent constant amplitude
stress-ranges were below 1.0 ksi at all locations, as seen in Table 3. These relatively small
equivalent constant amplitude stress ranges are small compared to those measured in
previous research on other 1950’s vintage RCDG bridges (Higgins et al. 2004) and
indicate high-cycle fatigue of the embedded reinforcing steel is unlikely.
6
Field Measured Dynamic Influence/Impact
As vehicles move across the bridge at highway speeds, the static force effects may be
amplified due to the dynamic response of the structure under the moving load and/or due to
impact of the wheels on the deck surface due to uneven approaches or deck surface
imperfections. An impact/dynamic coefficient was determined using the control test truck
data at each of the reinforcing steel strain locations. Impact coefficients were calculated as
the ratio of the peak strain produced by the truck as it moves in the marked lane at traveling
speed over the peak strain when the truck moves in the marked lane slowly (5 mph) across
the bridge. Impact coefficients were determined only for the cases when the truck was over
the instrumented section of the bridge (westbound inlane and eastbound in the wrong lane).
The impact coefficients are reported in Table 4. As seen in Table 4, there were cases when
the dynamic effects reduce the stress amplitude (ratios less than 1.0). The largest
controlling impact coefficient for the box girder was 1.12 (shear) and in the RCDG was
also 1.12 (flexure). These are less than that recommended by the AASHTO LRFR
provisions (typically taken as 1.2).
Field Measured Load Distribution
Distribution of shear and moment across the multiple girders/boxes on each of the bridges
was inferred from the relative magnitude of the peak measured strains in each girder across
the instrumented section of the bridge. Distribution of shear and moment was determined
from maximum measured strains for the truck passages at a slow speed (5 mph) in each of
the lane positions. Distribution factors were determined for a single truck in the various
lane positions and for two trucks in adjacent lane positions by superposition of the single
lane cases. The strain at a given section of the bridge was divided by the sum of the strains
on all girders at the section to determine the distribution factor. Theoretical 2-lane
positioning was also investigated by mirroring results from the single-lane test results.
Distribution factors based on strain measurements for the bridge are shown in Table 5. The
worst case load distribution factors for shear in the RCDG were approximately 0.42 for
one-lane loaded and 0.54 for two-lanes loaded (this is found by taking twice the value
shown in the table for the two lane loaded case to account for analysis and design practice
7
that uses a single lane loading to compute load effects in the bridge members). Shear
distribution in the box girder could not be determined as only the exterior stem was
available for instrumentation. The worst case load distribution factors for moment in the
RCDG were approximately 0.43 for one-lane loaded and 0.52 for two-lanes loaded. The
worst case load distribution factors for moment in the box girders were approximately 0.32
for one-lane loaded and 0.56 for two-lanes loaded. The distribution factors calculated here
represent the proportion of the statical force effect (shear or moment) on the bridge
assigned to an individual girder/box at the section under consideration when either one or
two trucks are in possible lane positions. The measured distributions are lower than would
be expected from the AASHTO design provisions (better load distribution than assumed at
design).
LRFR Rating and Risk Index Factors
The instrumented sections of the bridge were evaluated per AASHTO-LRFR and using the
OSU risk index methodology (Higgins et al. 2004). Ratings and risk indices were
computed for the 105.5 kip test truck configuration used for field testing (Fig. 5b). This
truck is believed to be consistent with the expected operational conditions on the bridge in
the future. The analysis methodology is described below.
Distribution factors for shear and moment were based on the field measured values. Two
lane distribution factors were used as these are the maximums in Table 5 (must take twice
the value shown in the table for the two lane loaded case). The maximum field measured
impact factors of 1.12 were applied to both shear and flexural load effects (from Table 4).
The resistance of these sections was computed per AASHTO-LRFD section 5.8 which uses
modified compression field theory (MCFT). The sectional capacity depends on a number
of variables including the concrete and rebar material strength (both transverse and
longitudinal steel), stirrup spacing, amount of flexural steel (including partially developed
bars), and the flexural resultant moment arm. The design drawings show class “A” 3300
psi concrete compressive strength and ASTM A305 “Intermediate Grade” deformed
reinforcing bars that correspond to 40 ksi yield. Because some cracks are diagonal, the
available longitudinal rebar areas crossing the diagonal crack is located at the beam soffit
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for the locations considered. Further, the statical shear and moment at the section are
computed at vertical cuts taken at mid-length of the diagonal cracks. The diagonal crack is
idealized as originating at the flexural tension steel (near bottom of the web) and is
assumed to be 45o for the purpose of determining the available steel areas and the location
for performing statics. The RCDG span was evaluated at two sections corresponding to the
instrumented sections: 31 ft and 7.4 ft east of Bent 6. The box girder span was evaluated at
two sections corresponding to the instrumented sections: 33 ft and 7.1 ft west of Bent 6.
The box girder section was treated as an equivalent deck-girder considering the outside
stem with only 1/6 of the available flexural steel in the lower flange attributed to this
section. In all cases the skin steel was neglected. AASHTO-LRFD MCFT curves were
developed at each of the instrumented sections. The resistance factor used with the shear-
moment interaction capacity curve was 0.9 for subsequent LRFR checks.
The flexural steel plays a key role in the shear-moment interaction capacity of the section,
and, where available, partially developed flexural steel was used. The amount of partially
developed steel was determined by taking the ratio of the available rebar embedded length
at the intersecting plane of the crack (considering the controlling lengths available on each
side of the crack) to the AASHTO-LRFD computed development length (straight bar
development per 5.11.2.1). Once the available flexural steel was determined, the effective
flange width was computed per AASHTO-LRFD 4.6.2.6. These were then used to compute
the AASHTO-LRFD MCFT nominal capacity envelopes per 5.8.3.3.
Load and Impact Factors
Dead load on the bridge was computed by estimating the total weight of the bridge and
distributing the weight evenly to all four girders as a uniformly distributed load. The
computed service-level weight of components (DC) was 1.66 kips/ft for the RCDG and
2.13 kips/ft for the box girder. A 2 in. thick asphalt wearing surface (DW) was assumed for
the bridge and this weight was also assumed to be evenly distributed to all four girders as
0.11 kips/ft. The dead load factors used in the rating analyses was 1.25 for DC and 1.5 for
DW. The dead load factor (applied to DC and DW) used in the risk index calculation is
1.0.
9
Analyses were performed using the test truck configuration illustrated in Fig. 5b. Oregon
specific live load factors (Groff, 2006) were used to compute AASHTO-LRFR consistent
rating factors. The Oregon-specific live load factor for the 105.5 kip GVW truck was used
with the value of 1.25 for ADTT<500.
Risk indices were computed using unfactored live and dead loads and an AASHTO-MCFT
nominal moment-shear interaction bias factor of 1.1 and a coefficient of variation of 7.4%,
based on full-scale test results designed to reflect 1950’s vintage detailed reinforced
concrete girders (Higgins et al. 2004).
Rating Factor and Risk Index Results
At each of the sections identified, the available capacity was compared with the demands
to determine the LRFR ratings and OSU risk indices for each of the 4 instrumented
sections. Results are shown in Figs. 8 to 11. As seen here, the instrumented sections rate
well according to the LRFR method and have low risk indices. These indicate the sections
are sufficient to safely carry the loads represented by the test truck. The box girder near
midspan shows the least conservative outcomes, although the analysis made conservative
assumptions that it operates as an individual girder rather than a box section (and used only
the exterior stem in the analysis).
Discussion
Based on the largest measured ambient traffic-induced responses (Fig. 4a, b, c, and d) and
the test truck measured responses (Appendix A and Table 1a and 1b) on the instrumented
sections of the bridge, it appears that the bridge is currently operating at the expected load
levels considered in the potential near-term developments on the island. The measured
strains and projected equivalent stress magnitudes and ranges are relatively small and well
below the service level stresses for which the original designers would likely have
designed. The strain ranges and numbers of cycles are also relatively low by comparison to
other similarly aged bridges instrumented by the research team. If the present operating
conditions were to remain, the bridge would likely continue to operate indefinitely, barring
unforeseen natural or manmade hazards.
10
If the bridge were subjected to higher numbers of heavier load cycles, of the numbers
considered in the proposed applications: 148 trips per weekday, rounded to 150 trips =
39,107 trips annually = 1,955,350 trips in a 50 year life, the anticipated effect on the
embedded reinforcing steel can be estimated. Considering the ambient traffic stress ranges
collected, there would conservatively be approximately 9.57days * 150trips/day=1,436
additional events at each location that would have been measured at stress ranges (taking
the maximum from either Table 2a or 2b and assuming all days of measurement were
weekdays) representative of the test truck. Artificially adding these into the results
collected, the resulting equivalent stress ranges were recalculated and are shown in Table
7. As seen here there is a modest increase in the equivalent stress ranges, but they are still
of sufficiently low magnitude such that fatigue of the embedded steel is not likely even
with the increased volume and magnitudes. Based on field measurements of in-service
bridges and laboratory tests of large-size concrete girders under high-cycle fatigue we
expect that a 50 year service life on an interstate bridge will have equivalent damage
represented by 2 million cycles of repeated load causing stirrup stresses of around 14 ksi
(Higgins et al. 2007). The present and expected operating stresses are well below this
value. They were also well below the AASHTO fatigue threshold of 20 ksi (and 10 ksi at
bends) for fatigue of reinforcing steel. Another possible long-term performance question is
bond fatigue. Under large repeated service level stresses, bond fatigue may occur whereby
the steel-concrete bond softens around crack locations and crack widths can grow over
time. Given the projected reinforcing steel stresses described above, bond fatigue damage
is not likely. However, routine periodic inspections should continue to identify new
cracking and monitor existing larger width cracks to identify changes that may occur over
time.
Summary and Conclusions
Bridge 01496A was instrumented, monitored under ambient traffic loads, and tested under
controlled truck loads. The test truck load magnitude was expected to be similar to that
proposed in the possible near-term development. Based on the field work, analysis of data,
and analytical evaluation of the sections considered, the following conclusions are made:
11
The bridge is presently operating at the projected load levels considered in the
proposed near-term development on the island.
Presently, the measured stress ranges and numbers of cycles are small and few,
respectively.
Under the present operating conditions, the bridge should continue operational
performance well into the future, barring unforeseen natural or manmade hazards.
Increasing the volume of heavy truck traffic will produce marginal increases in the
equivalent stresses in the bridge. These stresses are sufficiently small so that
continued operational performance of the bridge is expected.
Based on LRFR rating and OSU risk indices determined at the instrumented
sections, the bridge is sufficient to safely carry the expected load magnitudes
represented by the test truck.
Routine periodic inspections should continue to identify new cracking and monitor
existing larger width cracks on the spans to identify changes that may occur over
time.
12
References
Groff, R., (2006). ODOT LRFR Policy Report: LiveLoad Factors for Use in Load and Resistance Factor Rating (LRFR) of Oregon’s State-Owned Bridges. ODOT Bridge Engineering Section, Salem OR. Higgins, C., A.-Y. Lee, T. Potisuk, and R.W.B. Forrest. (2007). “High-cycle Fatigue of Diagonally Cracked RC Bridge Girders: Laboratory Tests” ASCE Journal of Bridge Engineering, Vol. 12, No.2, pp. 226-236. Higgins, C., T. H. Miller, D. V. Rosowsky, S. C. Yim, T. Potisuk, T. K. Daniels, B. S. Nicholas, M. J. Robelo, A.-Y. Lee, and R. W. Forrest. (2004). Assessment Methodology for Diagonally Cracked Reinforced Concrete Deck Girders. FHWA-OR-RD-05-04, Final Report, SPR 350, SR 500-091. Miner, M. A. (1945). “Cumulative Damage in Fatigue,” Journal of Applied Mechanics, Vol. 12, Trans. ASME Vol. 67, pp. A159-A164.
13
Table 1a – Maximum strain measurements for test truck with trailer eastbound.
Direction BOX BOX BOX BOX RCDG RCDG RCDG RCDG
of Concrete Flex Ext Flex Int Shear Shear Ext Shear Int Flex Ext Flex Int
Travel Speed Position CH_1 CH_2 CH_3 CH_4 CH_5 CH_6 CH_7 CH_8
EB Slow inlane 2 21 31 12 4 2 27 51
EB Slow Center 3 26 39 35 9 10 66 99
EB Slow wronglane 6 39 40 77 16 15 125 91
EB Fast inlane 2 26 35 15 5 1 39 64
EB Fast Center 2 28 41 34 7 7 62 94
EB Fast wronglane 2 38 41 77 16 15 113 102
Maximum Strain (microstrain)
Table 1b – Maximum strain measurements for test truck with trailer westbound.
Direction BOX BOX BOX BOX RCDG RCDG RCDG RCDG
of Concrete Flex Ext Flex Int Shear Shear Ext Shear Int Flex Ext Flex Int
Travel Speed Position CH_1 CH_2 CH_3 CH_4 CH_5 CH_6 CH_7 CH_8
WB Slow inlane 4 35 40 77 14 15 119 97
WB Slow Center 2 22 36 25 7 6 51 92
WB Slow wronglane 2 20 29 16 5 4 25 50
WB Fast inlane 3 35 37 86 13 15 121 99
WB Fast Center 2 23 36 34 8 7 62 98
WB Fast wronglane 1 23 30 19 5 2 34 64
Maximum Strain (microstrain)
Table 2a – Strain range measurements for test truck with trailer eastbound.
Direction BOX BOX BOX BOX RCDG RCDG RCDG RCDG
of Concrete Flex Ext Flex Int Shear Shear Ext Shear Int Flex Ext Flex Int
Travel Speed Position CH_1 CH_2 CH_3 CH_4 CH_5 CH_6 CH_7 CH_8
EB Slow inlane 6 30 43 30 5 7 38 59
EB Slow Center 7 33 51 42 10 18 77 107
EB Slow wronglane 12 46 51 95 24 23 137 98
EB Fast inlane 6 35 47 33 7 5 51 75
EB Fast Center 5 36 52 41 9 14 77 105
EB Fast wronglane 7 45 52 86 22 20 128 114
Strain Range (microstrain)
Table 2b – Strain range measurements for test truck with trailer westbound.
Direction BOX BOX BOX BOX RCDG RCDG RCDG RCDG
of Concrete Flex Ext Flex Int Shear Shear Ext Shear Int Flex Ext Flex Int
Travel Speed Position CH_1 CH_2 CH_3 CH_4 CH_5 CH_6 CH_7 CH_8
WB Slow inlane 10 43 50 92 22 23 134 108
WB Slow Center 6 31 47 33 10 9 65 103
WB Slow wronglane 6 29 40 31 6 7 38 59
WB Fast inlane 9 41 47 99 20 20 137 112
WB Fast Center 5 31 48 40 9 16 78 110
WB Fast wronglane 6 32 42 34 7 5 50 76
Strain Range (microstrain)
14
Table 3 – Equivalent stress ranges from ambient traffic data.
Table 4 – Impact coefficients based on strain measurements for test truck with trailer.
BOX BOX BOX BOX RCDG RCDG RCDG RCDG
Travel Concrete Flexural Exterior
Flexural Interior
Shear Shear Exterior
ShearInterior
Flexural Exterior
FlexuralInterior
Direction CH_1 CH_2 CH_3 CH_4 CH_5 CH_6 CH_7 CH_8
WB 0.87 1.00 0.94 1.12 0.93 0.96 1.02 1.02
EB 0.33 0.96 1.04 1.00 0.98 0.95 0.90 1.12
Table 5 – Load distribution percentages based on strain measurements for test truck with trailer.
Direction of Travel
Loading Scenario
Bridge Member
Load Effect
ExteriorGirder/ Stem
InteriorGirder/ Stem
InteriorGirder/ Stem
Exterior Girder/ Stem
Applied to Loading Case
Westbound One Lane RCDG Shear 37% 41% 10% 13% For one lane statics
Westbound Two Lanes
RCDG Shear 25% 25% 25% 25% For two lane statics
Westbound One Lane RCDG Moment 41% 33% 17% 9% For one lane statics
Westbound Two Lanes
RCDG Moment 25% 25% 25% 25% For two lane statics
Westbound One Lane Box Girder
Moment 28% 32% 24% 16% For one lane statics
Westbound Two Lanes
Box Girder
Moment 22% 28% 28% 22% For two lane statics
Eastbound One Lane RCDG Shear 11% 6% 40% 42% For one lane statics
Eastbound Two Lanes
RCDG Shear 27% 23% 23% 27% For two lane statics
Eastbound One Lane RCDG Moment 9% 17% 31% 43% For one lane statics
Eastbound Two Lanes
RCDG Moment 26% 24% 24% 26% For two lane statics
Eastbound One Lane Box Girder
Moment 16% 24% 30% 30% For one lane statics
Eastbound Two Lanes
Box Girder
Moment 23% 27% 27% 23% For two lane statics
Equivalent Channel Stress Range
ID (ksi) Material Span CH_1 0.026 Concrete Box Girder CH_2 0.64 Flexural Steel Box Girder CH_3 0.73 Flexural Steel Box Girder CH_4 0.60 Stirrup Box Girder CH_5 0.28 Stirrup RCDG CH_6 0.24 Stirrup RCDG CH_7 0.59 Flexural Steel RCDG CH_8 0.73 Flexural Steel RCDG
15
Table 6 – Anticipated equivalent stress ranges for proposed operational level with trucks having load
effects consistent with the test truck (105.5 kips GVW).
Equivalent Channel Stress Range
ID (ksi) Material Span CH_1 0.039 Concrete Box Girder CH_2 1.24 Flexural Steel Box Girder CH_3 1.48 Flexural Steel Box Girder CH_4 1.66 Stirrup Box Girder CH_5 0.63 Stirrup RCDG CH_6 0.48 Stirrup RCDG CH_7 1.88 Flexural Steel RCDG CH_8 1.95 Flexural Steel RCDG
16
Fig. 1‐ Example of instrumented section with stain gage on reinforcing bar and displacement sensor across crack (flexural reinforcing bar in box girder shown).
Fig. 2‐ Concrete surface strain gage on exterior face of box girder stem near soffit of deck.
17
Strain gage and displacement sensor
Strain gage
CH7 StrainCH17 Disp
Gird
er1
Gird
er2
Gird
er3
Gird
er4
Bent 9
Bent 8
Bent 7
Bent 6
CH8 StrainCH18 Disp
CH6 StrainCH12 Disp
CH5 StrainCH16 Disp
CH4 StrainCH15 Disp
Web
1
Web
2
Web
3
Web
4
Bent 6
Bent 5
Bent 4
Bent 3
CH2 StrainCH21 Disp
CH1 StrainConcrete
Flow
Tra
velD
irect
ion
Wes
t-B
ound
Tra
velD
irec
tion
We
st-B
oun
d
CH3 StrainCH22 Disp
Spa
n6
RC
DG
Spa
n7
RC
DG
Spa
n8
RC
DG
Spa
n3
Box
Gird
erS
pan
4B
ox
Gird
erS
pan
5B
oxG
irde
r
Fig. 3‐ Schematic of instrumentation locations and channel identifications.
18
Time (sec)
Str
ain
(
)
0 3 6 9 12 15 18 21 24 27 30-20
0
20
40
60
80
100
120
140CH_1CH_2CH_3CH_4CH_5CH_6CH_7CH_8
Fig. 4a – Large ambient traffic event WB 9/9/2010, 9:11 am. Maximum strain = 121 microstrain: CH_7.
Time (sec)
Str
ain
(
)
0 3 6 9 12 15 18 21 24 27 30-20
0
20
40
60
80
100
120
140CH_1CH_2CH_3CH_4CH_5CH_6CH_7CH_8
Fig. 4b – Large ambient traffic event WB 9/9/2010, 3:36 pm. Maximum strain = 127 microstrain: CH_7.
19
Time (sec)
Str
ain
(
)
0 3 6 9 12 15 18 21 24 27 30-20
0
20
40
60
80
100
120
140CH_1CH_2CH_3CH_4CH_5CH_6CH_7CH_8
Fig. 4c – Large ambient traffic event WB 9/21/2010, 2:30 pm. Maximum strain = 123 microstrain: CH_8.
Time (sec)
Str
ain
(
)
0 3 6 9 12 15 18 21 24 27 30-20
0
20
40
60
80
100
120
140
CH_1CH_2CH_3CH_4CH_5CH_6CH_7CH_8
Fig. 4d – Large ambient traffic event EB 9/21/2010, 5:01 pm. Maximum strain = 126 microstrain: CH_8.
20
Fig. 5a‐ Loaded test truck with trailer for controlled tests of bridge.
Test Truck with Trailer: GVW=105.0 kips
GVW: 49.1 kips
Sin
gle
Dro
p
Sin
gle
Dua
l
Sin
gle
Sin
gle
Dua
l
Dua
l
Ste
er
GVW: 55.9 kips
Fig. 5b‐ Test truck axle spacing and weights.
21
RCDG Spans 6, 7, and 8: Section looking east
In lanes
On/over lane markers
Lane Markers
In lanes
On/over lane markers
Box Girder Spans 3, 4, and 5: Section looking east
Fig. 6‐ Illustration of test truck positions relative to supporting bridge structure.
22
Strain Range ()
Nu
mb
er o
f C
ycle
sYamhill Bridge #01496A
Ambient Traffic 9.57 days of data
5 6 7 8 9 10 20 30 40 50 60 70 80 90100 2001
2
3
57
10
20
30
5070
100
200
300
500700
1000
2000
3000
50007000
10000
CH_1CH_2CH_3CH_4CH_5CH_6CH_7CH_8
Fig. 7‐ Number of cycles and corresponding strain ranges for ambient traffic.
Moment (kip-ft)
Sh
ear
(kip
s)
0 250 500 750 1000 1250 1500 1750 2000 2250 25000
20
40
60
80
100
120
140
160
180
200
Mn, VnMn, VnMu, Vu for LRFR
Fig. 8a ‐ LRFR rating for RCDG at 31 ft from Bent 6.
23
Moment (kip-ft)
Sh
ear
(kip
s)
0 300 600 900 1200 1500 1800 2100 2400 27000
25
50
75
100
125
150
175
200
225 Mn, VnExpected Mean Mn, VnM, V Service Levels-3 sigma Mn, Vn-5 sigma Mn, Vn
Fig. 8b – OSU Risk Index for RCDG at 31 ft from Bent 6.
Moment (kip-ft)
Sh
ear
(kip
s)
0 200 400 600 800 1000 1200 14000
25
50
75
100
125
150
175
200
Mn, VnMn, VnMu, Vu for LRFR
Fig. 9a ‐ LRFR rating for RCDG at 7.4 ft from Bent 6.
24
Moment (kip-ft)
Sh
ear
(kip
s)
0 200 400 600 800 1000 1200 1400 16000
25
50
75
100
125
150
175
200Mn, VnExpected Mean Mn, VnM, V Service Levels-3 sigma Mn, Vn-5 sigma Mn, Vn
Fig. 9b – OSU Risk Index for RCDG at 7.4 ft from Bent 6.
Moment (kip-ft)
Sh
ear
(kip
s)
0 300 600 900 1200 1500 1800 2100 2400 2700-25
0
25
50
75
100
125
150
175
200
225
Mn, VnMn, VnMu, Vu for LRFR
Fig. 10a ‐ LRFR rating for box girder at 35 ft from Bent 6.
25
Moment (kip-ft)
Sh
ear
(kip
s)
0 300 600 900 1200 1500 1800 2100 2400 2700 3000-25
0
25
50
75
100
125
150
175
200
225
250
Mn, VnExpected Mean Mn, VnM, V Service Levels-3 sigma Mn, Vn-5 sigma Mn, Vn
Fig. 10b – OSU Risk Index for box girder at 35 ft from Bent 6.
Moment (kip-ft)
Sh
ear
(kip
s)
0 200 400 600 800 1000 1200 1400 1600 18000
20
40
60
80
100
120
140
160Mn, VnMn, VnMu, Vu for LRFR
Fig. 11a ‐ LRFR rating for box girder at 7 ft from Bent 6.
26
Moment (kip-ft)
Sh
ear
(kip
s)
0 200 400 600 800 1000 1200 1400 1600 1800 20000
20
40
60
80
100
120
140
160
180Mn, VnExpected Mean Mn, VnM, V Service Levels-3 sigma Mn, Vn-5 sigma Mn, Vn
Fig. 11b – OSU Risk Index for box girder at 7 ft from Bent 6.
27
APPENDIX A
28
Time (sec)
Str
ain
(
)
20 28 36 44 52 60 68 76 84 92 100-20
0
20
40
60
80
100
120
140CH_1CH_2CH_3CH_4CH_5CH_6CH_7CH_8
Fig. A1‐ Strains for westbound in‐lane, slow speed, test truck with trailer.
Time (sec)
Dis
pla
cem
ent
(in
)
20 28 36 44 52 60 68 76 84 92 100-0.0005
-0.00025
0
0.00025
0.0005
0.00075
0.001
0.00125
0.0015
0.00175
0.002
0.00225
0.0025CH_12CH_13CH_14CH_15CH_16CH_17CH_18
Fig. A2‐ Crack displacements for westbound in‐lane, slow speed, test truck with trailer.
29
Time (sec)
Str
ain
(
)
15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30-20
0
20
40
60
80
100
120
140CH_1CH_2CH_3CH_4CH_5CH_6CH_7CH_8
Fig. A3‐ Strains for westbound in‐lane, fast speed, test truck with trailer.
Time (sec)
Dis
pla
cem
en
t (i
n)
15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30-0.0005
-0.00025
0
0.00025
0.0005
0.00075
0.001
0.00125
0.0015
0.00175
0.002
0.00225
0.0025CH_12CH_13CH_14CH_15CH_16CH_17CH_18
Fig. A4‐ Crack displacements for westbound in‐lane, fast speed, test truck with trailer.
30
Time (sec)
Str
ain
(
)
40 48 56 64 72 80 88 96 104 112 120-20
0
20
40
60
80
100
120
140CH_1CH_2CH_3CH_4CH_5CH_6CH_7CH_8
Fig. A5‐ Strains for westbound over center stripe, slow speed, test truck with trailer.
Time (sec)
Dis
pla
cem
ent
(in
)
40 48 56 64 72 80 88 96 104 112 120-0.0005
-0.00025
0
0.00025
0.0005
0.00075
0.001
0.00125
0.0015
0.00175
0.002
0.00225
0.0025CH_12CH_13CH_14CH_15CH_16CH_17CH_18
Fig. A6‐ Crack displacements for westbound over center stripe, slow speed, test truck with trailer.
31
Time (sec)
Str
ain
(
)
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15-20
0
20
40
60
80
100
120
140CH_1CH_2CH_3CH_4CH_5CH_6CH_7CH_8
Fig. A7‐ Strains for westbound over center stripe, fast speed, test truck with trailer.
Time (sec)
Dis
pla
cem
en
t (i
n)
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15-0.0005
-0.00025
0
0.00025
0.0005
0.00075
0.001
0.00125
0.0015
0.00175
0.002
0.00225
0.0025CH_12CH_13CH_14CH_15CH_16CH_17CH_18
Fig. A8‐ Crack displacements for westbound over center stripe, fast speed, test truck with trailer.
32
Time (sec)
Str
ain
(
)
50 55 60 65 70 75 80 85 90 95 100 105 110 115 120 125 130-20
0
20
40
60
80
100
120
140CH_1CH_2CH_3CH_4CH_5CH_6CH_7CH_8
Fig. A9‐ Strains for westbound wrong lane, slow speed, test truck with trailer.
Time (sec)
Dis
pla
cem
ent
(in
)
50 55 60 65 70 75 80 85 90 95 100 105 110 115 120 125 130-0.0005
-0.00025
0
0.00025
0.0005
0.00075
0.001
0.00125
0.0015
0.00175
0.002
0.00225
0.0025CH_12CH_13CH_14CH_15CH_16CH_17CH_18
Fig. A10‐ Crack displacements for westbound wrong lane, slow speed, test truck with trailer.
33
Time (sec)
Str
ain
(
)
20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40-20
0
20
40
60
80
100
120
140CH_1CH_2CH_3CH_4CH_5CH_6CH_7CH_8
Fig. A11‐ Strains for westbound wrong lane, fast speed, test truck with trailer.
Time (sec)
Dis
pla
cem
en
t (i
n)
20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40-0.0005
-0.00025
0
0.00025
0.0005
0.00075
0.001
0.00125
0.0015
0.00175
0.002
0.00225
0.0025CH_12CH_13CH_14CH_15CH_16CH_17CH_18
Fig. A12‐ Crack displacements for westbound wrong lane, fast speed, test truck with trailer.
34
Time (sec)
Str
ain
(
)
40 48 56 64 72 80 88 96 104 112 120-20
0
20
40
60
80
100
120
140CH_1CH_2CH_3CH_4CH_5CH_6CH_7CH_8
Fig. A13‐ Strains for eastbound in lane, slow speed, test truck with trailer.
Time (sec)
Dis
pla
cem
en
t (i
n)
40 48 56 64 72 80 88 96 104 112 120-0.0005
-0.00025
0
0.00025
0.0005
0.00075
0.001
0.00125
0.0015
0.00175
0.002
0.00225
0.0025CH_12CH_13CH_14CH_15CH_16CH_17CH_18
Fig. A14‐ Crack displacements for eastbound in lane, slow speed, test truck with trailer.
35
Time (sec)
Str
ain
(
)
20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40-20
0
20
40
60
80
100
120
140CH_1CH_2CH_3CH_4CH_5CH_6CH_7CH_8
Fig. A15‐ Strains for eastbound in lane, fast speed, test truck with trailer.
Time (sec)
Dis
pla
cem
ent
(in
)
20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40-0.0002
0
0.0002
0.0004
0.0006
0.0008
0.001
0.0012
0.0014
0.0016
0.0018
0.002CH_12CH_13CH_14CH_15CH_16CH_17CH_18
Fig. A16‐ Crack displacements for eastbound in lane, fast speed, test truck with trailer.
36
Time (sec)
Str
ain
(
)
40 48 56 64 72 80 88 96 104 112 120-20
0
20
40
60
80
100
120
140CH_1CH_2CH_3CH_4CH_5CH_6CH_7CH_8
Fig. A17‐ Strains for eastbound over center stripe, slow speed, test truck with trailer.
Time (sec)
Dis
pla
cem
ent
(in
)
40 48 56 64 72 80 88 96 104 112 120-0.0002
0
0.0002
0.0004
0.0006
0.0008
0.001
0.0012
0.0014
0.0016
0.0018
0.002CH_12CH_13CH_14CH_15CH_16CH_17CH_18
Fig. A18‐ Crack displacements for eastbound over center stripe, slow speed, test truck with trailer.
37
Time (sec)
Str
ain
(
)
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20-20
0
20
40
60
80
100
120
140CH_1CH_2CH_3CH_4CH_5CH_6CH_7CH_8
Fig. A19‐ Strains for eastbound over center stripe, fast speed, test truck with trailer.
Time (sec)
Dis
pla
cem
ent
(in
)
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20-0.0002
0
0.0002
0.0004
0.0006
0.0008
0.001
0.0012
0.0014
0.0016
0.0018
0.002CH_12CH_13CH_14CH_15CH_16CH_17CH_18
Fig. A20‐ Crack displacements for eastbound over center stripe, fast speed, test truck with trailer.
38
Time (sec)
Str
ain
(
)
30 35 40 45 50 55 60 65 70 75 80 85 90 95 100 105 110-20
0
20
40
60
80
100
120
140CH_1CH_2CH_3CH_4CH_5CH_6CH_7CH_8
Fig. A21‐ Strains for eastbound wrong lane, slow speed, test truck with trailer.
Time (sec)
Dis
pla
cem
en
t (i
n)
30 35 40 45 50 55 60 65 70 75 80 85 90 95 100 105 110-0.0005
-0.00025
0
0.00025
0.0005
0.00075
0.001
0.00125
0.0015
0.00175
0.002
0.00225
0.0025CH_12CH_13CH_14CH_15CH_16CH_17CH_18
Fig. A22‐ Crack displacements for eastbound wrong lane, slow speed, test truck with trailer.
39
Time (sec)
Str
ain
(
)
5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25-20
0
20
40
60
80
100
120
140CH_1CH_2CH_3CH_4CH_5CH_6CH_7CH_8
Fig. A23‐ Strains for eastbound wrong lane, fast speed, test truck with trailer.
Time (sec)
Dis
pla
cem
ent
(in
)
5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25-0.0002
0
0.0002
0.0004
0.0006
0.0008
0.001
0.0012
0.0014
0.0016
0.0018
0.002CH_12CH_13CH_14CH_15CH_16CH_17CH_18
Fig. A24‐ Crack displacements for eastbound wrong lane, fast speed, test truck with trailer.