bridge no 027601 - bditest.com · aashto lrfr approach. review of the load test results indicated...

BRIDGE LOAD RATING

PREPARED FOR

RHODE ISLAND

DEPARTMENT OF TRANSPORTATION LINCOLN, RI

LOUISQUISSET PIKE BRIDGE (RI 146)

OVER

WASHINGTON HIGHWAY

BRIDGE NO. 027601

PRE-RETROFIT

DATE OF RATING: 10/2011

POST-RETROFIT

DATE OF RATING: 03/2012

PREPARED BY:

BRIDGE DIAGNOSTICS, INC.

1995 57th

Court North, Suite 100

Boulder, CO 80301

303.494.3230

www.bridgetest.com

http://www.bridgetest.com/

FIELD TESTING AND LOAD RATING REPORT:

LOUISQUISSET PIKE BRIDGE – RIDOT #276

LINCOLN, RI

SUBMITTED TO:

AECOM USA, Inc. 10 Orms Street, Suite 405

Providence RI 0290

www.aecom.com

SUBMITTED BY:

BRIDGE DIAGNOSTICS, INC.

1965 57th

Court North, Suite 106

Boulder, CO 80301

303.494.3230

www.bridgetest.com

June 2012

http://www.bridgetest.com/

LOAD TESTING AND LOAD RATING REPORT –RIDOT BRIDGE 027601: LINCOLN, RI III

REPORT INDEX

REPORT INDEX ................................................................................................................................................... III

EXECUTIVE SUMMARY ................................................................................................................................... IV

SUMMARY OF BRIDGE RATING .................................................................................................................... VI

BREAKDOWN OF BRIDGE RATING ............................................................................................................. VII

LOCATION PLAN ................................................................................................................................................ IX

DESCRIPTION OF BRIDGE ................................................................................................................................ X

1. LOAD TESTING .............................................................................................................................................. 11

1.1 STRUCTURAL TESTING PROCEDURES ................................................................................................ 11 1.2 PRELIMINARY INVESTIGATION OF TEST RESULTS .............................................................................. 22

2. RATING ANALYSIS ASSUMPTIONS AND CRITERIA ........................................................................... 33

2.1 MODE LING, ANALYSIS, AND DATA CORRELATION ........................................................................... 33 Modeling Procedures: .......................................................................................................... 33 2.1.1

Model Calibration Results .................................................................................................... 35 2.1.2

2.2 LOAD RATING PROCEDURES .............................................................................................................. 46 2.3 TRUCK LOAD COMBINATIONS AND CONFIGURATIONS ...................................................................... 53

3. EVALUATION OF RATING AND RECOMMENDATIONS ..................................................................... 60

3.1 LOAD RATING RESULTS: ................................................................................................................... 60 3.2 CONCLUSIONS AND RECOMMENDATIONS .......................................................................................... 63

4. REFERENCES & AVAILABLE PLANS ....................................................................................................... 65

4.1 REFERENCES ...................................................................................................................................... 65 4.2 AVAILABLE PLANS ............................................................................................................................ 66

A. INSPECTION REPORT .................................................................................................................................. 77

B. APPENDIX B – PHOTOS ................................................................................................................................ 88

C. APPENDIX C – QUALITY CONTROL/QUALITY ASSURANCE ........................................................... 92

D. APPENDIX D – COMPUTER INPUT & OUTPUT ...................................................................................... 93

E. APPENDIX E – TESTING REFERENCE INFORMATION ...................................................................... 98

E.1. SCANNED FIELD NOTES ..................................................................................................................... 98 E.2. EQUIPMENT SPECIFICATIONS ........................................................................................................... 103

LOAD TESTING AND LOAD RATING REPORT –RIDOT BRIDGE 027601: LINCOLN, RI IV

EXECUTIVE SUMMARY

In 2009, Bridge Diagnostics, Inc. (BDI) was contracted by AECOM, Inc. in coordination with

the Rhode Island Department of Transportation (RIDOT) to perform live-load testing and

subsequent load rating on the Louisquisset Pike Bridge (RIDOT Bridge #276) in Lincoln, RI.

The goal of this project was to obtain and then utilize field measurements to verify and calibrate

an analytical model from which accurate load ratings could be obtained. As a result of the load

testing and rating performed in 2009, it was found that a flawed reinforcement detail roughly

located at the 2/3 span locations caused the structure to have very low critical ratings in positive

moment (HL-93 rating of 0.34).

This conclusion resulted in emergency repairs that involved strengthening the 2/3 span

regions with a Tyfo® SCH-41-2X carbon fiber reinforced polymer (CFRP) system. Once this

retrofit was completed, additional load testing on the structure was performed in January 2012 to

determine the post-retrofit structural behavior and to determine if the retrofit was a success.

The BDI Wireless Structural Testing System (STS-WiFi) was used to measure strains,

displacements, and rotations on the superstructure while the bridge was subjected to a moving

truck load. The resulting response data was examined and evaluated in a qualitative manner,

compared to the data previously collected in 2009, and then used to calibrate a finite-element

model of the structure. The calibrated model was in turn used to develop load ratings using the

AASHTO LRFR approach.

Review of the load test results indicated that the live-load responses were of good quality and

also provided evidence that the bridge was acting in a linear-elastic manner; despite the fact that

severe degradation was observed at several locations along the superstructure. A very good

correlation was obtained by the linear-elastic analysis after the bridge model was calibrated,

further indicating that the recorded responses were linear. It was also found that the test truck

crossed the structure at 55 mph with negligible dynamic effects. This observation indicated that

the use of the AASHTO standard 33% impact factor resulted in conservative ratings.

On the whole, it was found that the structural responses did not significantly change between

the 2009 and 2012 tests. However, during the model calibration process it was found that the

optimized rotational restraint at the supports did in fact reduce by a noteworthy amount (10-

30%). This change in optimized behavior could have been caused by a variety of factors

including the fact that the rotation sensors were not used in the previous 2009 testing, from

which rotational restraint can best be captured. Additionally, the 2009 and 2012 tests were

performed at different times of the year with very different ambient conditions. Regardless of

what caused this change in behavior, this rotational restraint was reduced further for rating in

order to ensure conservative rating values.

During both sets of load tests (2009 & 2012), the ribs were found to be acting fully composite

with the deck; which means that these members have been able to retain their composite action

for 70 years with a wide range of loading conditions. This observed behavior was validated in

terms of capacity by evaluating the ribs’ ability to transfer horizontal shear to the deck. It was

found based on the AASHTO LRFD Bridge Design Specifications 5th

Edition – 2010 that there

was enough interface shear transfer capacity between the deck and the ribs that composite

behavior could be relied upon throughout of the structure.

LOAD TESTING AND LOAD RATING REPORT –RIDOT BRIDGE 027601: LINCOLN, RI V

In general, the critical ratings for the majority of the rating vehicles were controlled by shear

in an interior rib near the pier at the location where the stirrup spacing changes from 12” to 18”.

The one exception to this rating trend was the AASHTO specialized hauling vehicle SU7 which

was controlled in negative moment at the face of the north abutment. The structure failed the

LRFR design rating criteria (for the HL-93 design loading) at the inventory level but nearly

passed the criteria at the operating level (note: the critical HL-93 operating level rating for shear

was nearly satisfactory at RF=0.96). All of the AASHTO legal/hauling loads had satisfactory

ratings with the one exception being the SU7 rating for negative moment of 0.97. Lastly, it was

found that the structure failed the LRFR rating criteria for the majority of the RIDOT permit

loads with the exception of the single-trip permit loads (RI-OP2 and RI-OP3). The overall

critical rating of 0.63 was controlled by shear in an interior rib under the loading of the blanket

permit truck RI-BP4.

It was expected that the structure would not meet the AASHTO LRFR design rating criteria

since this structure was built in 1942 and therefore not designed to LRFD standards. The

AASHTO legal load rating results indicate all trucks that fit within the AASHTO legal load

envelope can safely cross the structure at normal speed. Additionally, the rating results showed

that the majority of the RIDOT permit trucks cannot safely cross the structure at normal speed.

Although the structure now has satisfactory ratings for many of the rating vehicles, BDI still

recommends that frequent thorough inspections take place to monitor the escalation of the

observed structural degradation.

It is important to note that the aforementioned ratings are applicable to the bridge in its

current condition. This means that the ratings provided by BDI utilized the composite behavior

and stiffness of the ribs as observed in the live-load tests. It is likely that since the ribs have

retained their composite action for approximately 70 years, they will continue to retain it for

years to come. However in the unlikely event that the composite bond between the ribs and the

deck began to diminish, the composite rating factors would eventually become invalid. To

accommodate this situation, non-composite ratings were generated for HL-93 design loading as a

general reference. However, it is very important to state that the provided non-composite rating

factor was provided only as a very general comparison. This is because if the structural

degradation gets to the point where the composite action diminishes, many of the other model

assumptions besides the composite behavior would most likely be suspect as well (e.g., the

rotational restraint of the frame system, the rib and deck stiffness, etc.).

Lastly, it should be noted that load ratings were calculated for the interior ribs only, and were

not calculated for the abutment legs or the pier columns. This was due to the fact that the

substructure did not control the previous load ratings, and very little structural degradation was

seen at these locations. This decision was supported by AECOM.

This report contains details regarding the instrumentation and load testing procedures, a

qualitative review of the load test data, a brief explanation of the modeling steps and results, and

a summary of the load rating methods and results.

LOAD TESTING AND LOAD RATING REPORT –RIDOT BRIDGE 027601: LINCOLN, RI VI

SUMMARY OF BRIDGE RATING

Town: Lincoln

Route Carried: Eddie Dowling Highway

Owner: Rhode Island

Maintained By: Rhode Island

Bridge No: 027601

Crosses: Washington Highway (116)

Year Built: 1942

Year(s) Rebuilt/Rehab: Rehab2011

VEHICLE

TYPE RF

RL

(TONS)

POSTING

(TONS)

HL-

93

INV 0.74 --- ---

OPER 0.96 --- ---

H-20 1.22 24.4 ---

Type 3 1.16 29.0 ---

Type 3S2 1.21 43.6 ---

Type 3-3 1.29 51.6 ---

SU4 1.17 31.6 ---

SU5 1.08 33.5 ---

SU6 1.06 36.8 ---

SU7 0.97 37.6 37.1

RI-BP1 0.71 27.0 22.3

RI-BP2 0.75 28.1 24.1

RI-BP3 0.67 35.1 27.7

RI-BP4 0.66 42.9 30.6

RI-OP1 0.88 49.7 46.8

RI-OP2 1.02 81.6 ---

RI-OP3 0.96 108.5 106.5

LRFR Evaluation Factors

Surface Roughness Rating N/A

Governing Condition Factor, φc 0.85

System Factor, φb 1.0

ADTT 3500

Posting Analysis

Posting Recommendation (Y/N): Y

Governing RF 0.66

Governing Load Model RI-BP4

QA/QC

Load Rating Engineer

Name Brice Carpenter


License # N/A

Load Rating Checked

By

Brett Commander

PE#9396


Signature

Quality Assurance By Brett Commander

Load Rating Date 3/23/2011

Please check the following boxes that apply:

[X] Bridge load rating is not governed by deck rating

[X] Bridge load rating is not governed by substructure rating

[X] Connections do not control the load rating

[ ] Exterior girder controls the load rating

[ ] Bridge Plans do not exist; load rating based on judgment and current rating

[ ] As-built rating

[X] As-inspected rating

[ ] Recommend Proof load test due to limited available information (Note: only if bridge requires posting)

LOAD TESTING AND LOAD RATING REPORT –RIDOT BRIDGE 027601: LINCOLN, RI VII

BREAKDOWN OF BRIDGE RATING

Town: Lincoln Bridge No: 027601

Route Carried: Eddie Dowling Highway Crosses: Washington Highway (116)

Owner: Rhode Island Year Built: 1942

Maintained By: Rhode Island Year(s) Rebuilt/Rehab: Rehab2011

AASHTO RATING LOADS

RATING FACTORS (RF) & LOADS (RL, Tons)

BRIDGE COMPONENT:

CONTROLLING ACTION

DESIGN LOAD (STRENGTH I)

LEGAL LOADS

(Strength I)

HL-93 Rating

Form H20 TYPE 3 TYPE 3S2 TYPE 3-3 SU4 SU5 SU6 SU7

CONTROLLING LOCATION Inventory Operating

Ribs: +M

0.84 1.09 RF 1.26 1.36 1.34 1.63 1.34 1.25 1.13 1.05

@ CFRP Retrofitted Region RL 25.2 34.0 48.2 65.2 36.2 38.8 39.3 40.7

Ribs: -M

0.75 0.97 RF 1.51 1.28 1.22 1.30 1.32 1.18 1.06 0.97

@ Face of Abutment RL 30.2 32.0 43.9 52.0 35.6 36.6 36.8 37.6

Ribs: V

0.74 0.96 RF 1.22 1.16 1.21 1.29 1.17 1.08 1.06 1.00

@ spacing = 18” RL 24.4 29.0 43.6 51.6 31.6 33.5 36.8 38.8

Non-Composite Ribs**: M-

0.42 0.54 RF --- --- --- --- --- --- --- ---

@ Face of Abutment RL --- --- --- --- --- --- --- ---

**- HL-93 Non-Composite Ribs Ratings were provided for reference only and do not accurately reflect the structural behavior

observed at time of testing.

LOAD TESTING AND LOAD RATING REPORT –RIDOT BRIDGE 027601: LINCOLN, RI VIII

RIDOT PERMIT LOADS

RATING FACTORS (RF) & LOADS (RL, Tons)

BRIDGE COMPONENT:

CONTROLLING ACTION

RI PERMIT TRUCKS

(Strength II / Service I)

CONTROLLING LOCATION Rating

Form

RI – BP1 RI – BP2 RI – BP3 RI – BP4 RI – OP1 RI – OP2 RI – OP3

Str II Sev I Str II Sev I Str II Sev I Str II Sev I Str II Sev I Str II Sev I Str II Sev I

Ribs: +M RF 0.82 1.45 0.86 1.59 0.8 1.55 0.83 1.58 1.07 1.6 1.28 1.84 1.41 2.02

@ CFRP Retrofitted Region RL 31.2 55.1 32.3 59.6 41.9 81.2 54.0 102.7 60.5 90.4 102.4 147.2 159.3 228.3

Ribs: -M RF 0.82 1.64 0.82 1.65 0.67 1.35 0.82 1.64 0.89 1.49 1.41 2.13 1.13 1.70

@ Face of Abutment RL 31.2 62.3 30.8 61.9 35.1 70.7 53.3 106.6 50.3 84.2 112.8 170.4 127.7 192.1

Ribs: V RF 0.71 --- 0.75 --- 0.72 --- 0.63 --- 0.88 --- 1.02 --- 0.96 ---

@ spacing = 18” RL 27.0 --- 28.1 --- 37.7 --- 41.0 --- 49.7 --- 81.6 --- 108.5 ---

LOAD TESTING AND LOAD RATING REPORT –RIDOT BRIDGE 027601: LINCOLN, RI IX

LOCATION PLAN

(Source: Google Maps, 2012)

RIDOT 027601

LOAD TESTING AND LOAD RATING REPORT –RIDOT BRIDGE 027601: LINCOLN, RI X

DESCRIPTION OF BRIDGE

Bridge Number: 027601

Owner: Rhode Island

Maintained By: Rhode Island

Location: Lincoln

Route Carried: Eddie Dowling Highway (RI 146)

Feature Intersected: George Washington (RI 116)

Latest NBI Inspection Date: 10/17/2011

Field Verification Date (if applicable): 1/24/2012

Date of Construction: 1942

Bridge Type: Reinforced Concrete Rigid Rib with CFRP

Original Design Loading: HS20 (Per Inspection Report)

Date(s) of Rebuild/Rehab: Rehab(2011)

Description of Rebuild/Rehab: CFRP Strengthening (2011)

Posting: None

Superstructure: 18 R/C haunched ribs spaced at max of 5’-0” with

diaphragms at third points, Cast-in-place deck, stand-

alone deck panel between ribs I and J (essentially

creating two parallel structures)

Substructure: Concrete abutments and integral columns

Bearings: N/A

Bridge Spans: 54’-8” clear

Bridge Skew: 42.0º

Bridge Width: 84’-4”out-to-out

Roadway Width: 34’-0” (each – two roadways)

Roadway Surface: Bituminous

Curbs: Concrete curbs along sidewalks

Sidewalk/Walkway/Median: Concrete Sidewalk supported by brackets

Utilities: None

Bridge Railing: Meets Standards

Approach Railing: Meets Standards

Deck Condition: 4 Poor

Superstructure Condition: 4 Poor

Bearing Condition: N/A

Abutment Condition: 5 Fair

LOAD TESTING AND LOAD RATING REPORT –BRIDGE 027601: LINCOLN, RI 11

1. LOAD TESTING

1.1 STRUCTURAL TESTING PROCEDURES

The Louisquisset Pike Bridge (Rhode Island Bridge #027601) is a two-span continuous,

reinforced concrete rigid frame bridge that carries Eddie Dowling Highway (RI 146) over

Washington Highway (RI 116) in Lincoln, RI. The bridge has a concrete cast in-place deck with

a bituminous concrete wearing surface, and has a 42° skew. The superstructure consists of

eighteen haunched framed ribs (denoted as “ribs” hereafter) spaced at a maximum of 5’-0”, with

a stand-alone deck panel between Ribs I and J (essentially creating two parallel structures). Each

span has a clear-span length of 54’-8”, and the overall structure length is 118’-0”. In July of

2009, this structure was load tested and subsequently rated by BDI. It was found that the

structure had a poor rating due to a flawed reinforcement detail near the 2/3 span location. Due to

this discovery, the structure was strengthened with a Tyfo® SCH-41-2X carbon fiber reinforced

polymer (CFRP) system in these regions and retested to provide evidence that the retrofit was

successful.

Although an in-depth visual inspection was not performed by BDI, structural degradation was

extremely clear. The 2012 special inspection report rated the bridge deck and superstructure in

“poor” condition (4) and the substructure in “fair” condition (5). Significant spalling and

cracking was observed in nearly all of the ribs, and the reinforcing steel was exposed and found

to have up to 10% section loss in multiple locations.

During testing, the BDI Wireless Structural Testing System (STS-WiFi) was used to measure

strains, displacements, and rotations on the superstructure. The following are descriptions of the

instrumentation (Figure 1.1-7).

38 Surface-Mounted Strain Transducers were installed along eight gage lines (denoted as

Sections 1-1 through 8-8 in Figure 1.1-8 thru Figure 1.1-15). These gages were placed

along the side of the ribs (near the top and bottom of a given rib) near the support and

midspan locations of both spans (see Figure 1.1-1 and Figure 1.1-2). Note that strain

gages were not placed along the bottom surface of the ribs due to the poor condition of

these regions. Extended twenty-four inch gage lengths were used at all locations. These

gages extensions allowed strain responses to be recorded over a larger length, which

helped to reduce localized effects like micro-cracking, cracking, nearby spalling, etc.

10 Cantilevered Displacement Sensors were mounted to the bottom of selected ribs at the

midspan of both spans and each sensor’s reference chain was attached to a concrete

masonry unit (CMU) placed on the roadway directly below the sensor (see Figure 1.1-3

and Figure 1.1-4). These sensors were used measure the vertical deflections of the ribs at

midspan.

4 Tiltmeter Rotation Sensors were mounted to the side of selected ribs near both the north

abutment and the interior pier in order to capture the rotational behavior near the supports

(see Figure 1.1-5).

Once the instrumentation was installed, a series of controlled live-load tests were completed.

During testing, data was recorded on all channels at sample rate of 40 Hz as the test vehicle (a 3-

axle dump truck) crossed the structure at approximately 3 to 5 mph. The truck’s longitudinal

position was wirelessly tracked so that the response data could later be viewed as a function of


vehicle position. This step was critical for the analysis phase as it allowed responses to be

related to a truck position rather than just an arbitrary point in time. Once the semi-static tests

were completed, one “high speed” test run was performed with the test truck crossing the

structure at a typical speed (~55 mph). This additional test was performed in order to obtain

dynamic data from the structure. This dynamic data was later used to provide evidence of the

actual impact characteristics of the bridge approaches at the time of testing.

Test runs were performed with the test truck traveling in the southbound direction along four

different lateral positions referred to as Paths Y1 through Y4, which are shown in Figure 1.1-16.

In this figure, the distance denoting the locations of the lateral truck positions were measured

(perpendicular to the roadway) from the test reference location (designated as the BOW -

“Beginning of World”) to the center of either the driver’s side (“D”) or passenger side (“P”) front

tire. Note that the test reference location (BOW) was positioned at the northwest corner of the

bridge along the outside edge of the parapet, as shown in Figure 1.1-6.

Information specific to the load tests can be found in Table 1.1-1, and scanned field notes are

also provided in Appendix E.1 for additional reference. The test vehicle’s gross weight, axle

weights, and wheel rollout distance (required for tracking its position along the structure) are

provided in Table 1.1-2, while a vehicle “footprint” of the test truck is also shown in Figure

1.1-17. The vehicle weights were obtained from certified scales at a local gravel pit, and all

vehicle dimensions were measured in the field at the time of testing.

BDI would like to thank AECOM Inc. and ARIES Inc. for their help in scheduling, planning,

and completing the testing project!

Table 1.1-1 Structure description & testing notes.

ITEM DESCRIPTION

STRUCTURE NAME Louisquisset Pike Bridge

BDI Project Number 110801-RI

TESTING DATE January 24th, 2012

CLIENT’S STRUCTURE ID # 027601 (#276)

LOCATION/ROUTE Eddie Dowling Highway (RI 146) over George Washington

Highway (RI 116)

STRUCTURE TYPE R/ C Rigid Frame w/ CFRP retrofit at 2/3 points

TOTAL NUMBER OF SPANS 2

SPANS TESTED 2

TEST REFERENCE LOCATION

(“BEGINNING OF WORLD”

(“BOW”)) (X=0,Y=0)

Northwest corner of bridge, Outside edge of parapet

(Figure 1.1-6)

TEST VEHICLE DIRECTION South

TEST BEGINNING POINT Front axle at X = -16’-1”

LATERAL LOAD POSITIONS Y1 = 39’-4” (D), Y2 = 27’-2” (D), Y3 = 17’-2” (D), Y4 = 6’-11”

(P), - Measurements from the test reference location

NUMBER/TYPE OF SENSORS 38 strain transducers, 10 displacement sensors, & 4 rotation

sensors


ITEM DESCRIPTION

SAMPLE RATE 40 Hz – Semi-static testing

100 Hz – High speed testing

NUMBER OF TEST VEHICLES 1

VEHICLE PROVIDED BY: Aries

TRAFFIC CONTROL PROVIDED BY: Aries

ACCESS PROVIDED BY: Aries

TOTAL FIELD TESTING TIME 1 Day

TEST FILE INFORMATION

FILE NAME LATERAL

POSITION FIELD COMMENTS

Br276_Y4_1.dat Y4 Good, little drifty

Br276_Y4_2.dat Y4 Good



Br276_Y2_1.dat Y2 Good, missed 1 click near

end of test

Br276_Y2_2.dat Y2 Good, drifty

Br276_Y1_1.dat Y1 Good, drifty


Br276_Y2_HS.dat Y2 Good, truck data ~80-100

seconds into test


Figure 1.1-1 Surface-mounted strain sensor near the bottom of a rib (Typical).

Figure 1.1-2 Surface-mounted strain sensor near the top of a rib (Typical).


Figure 1.1-3 Displacement sensor installed at midspan without reference chain.

Figure 1.1-4 Overall view displaying displacement sensors’ reference chains.


Figure 1.1-5 Rotation sensor installed near pier (typical).

Figure 1.1-6 Picture of Test Reference Point Location (Beginning of World -BOW).


Figure 1.1-7 Instrumentation plan view with overall gage locations and types.


Figure 1.1-8 Cross-sectional view of Section 1-1 with gage ID’s, and Channel ID’s.





Figure 1.1-16 Truck Path Information.


Table 1.1-2 Test Vehicle Information.

VEHICLE TYPE TANDEM REAR AXLE DUMP TRUCK

GROSS VEHICLE WEIGHT (GVW) 75.3 kips

WEIGHT/WIDTH - AXLE 1 18.6 6’-10”

WEIGHT/WIDTH – AXLE 2 28.35 kips 7’-2”

WEIGHT/WIDTH – AXLE 3 28.35 kips 7’-2”

SPACING: AXLE 1 - AXLE 2 19’-0”

SPACING: AXLE 2 – AXLE 3 4’-5”

WEIGHTS PROVIDED BY Aries

AUTOCLICKER POSITION Passenger – 3rd

axle

WHEEL ROLLOUT 5 REVS 56’-4”

WHEEL CIRCUMFERENCE 11.27’

# CRAWL SPEED PASSES 8

# HIGH SPEED PASSES/SPEED 1 55 mph

VEHICLE PROVIDED BY Aries

Figure 1.1-17 Test Vehicle Footprint.


1.2 PRELIMINARY INVESTIGATION OF TEST RESULTS

All of the field data was first examined graphically to determine its quality and to provide a

qualitative assessment of the structure's live-load response. Some of the indicators of data

quality included reproducibility between identical truck crossings, elastic behavior (strains

returning to zero after truck crossing), and any unusual-shaped responses that might indicate

nonlinear behavior or possible gage malfunctions. In addition to providing a data "quality

check", the information obtained during the preliminary investigation was used to determine

appropriate modeling procedures and helped establish the direction that the analysis should take.

Overall the measured strain and displacement responses were of an expected magnitude with

a maximum displacement of about 0.023in and peak strain values of approximately 28µε. The

2012 results closely matched the responses measured in 2009, which is described further below.

This sub-section of the report provides a summary of the investigation results of post-retrofit test.

Several representative response histories are provided below to illustrate specific structural

behavior.

REPRODUCIBILITY AND LINEARITY: Responses from identical truck paths were very

reproducible as shown in Figure 1.2-1 through Figure 1.2-3. In addition, all responses

appeared to be linear with respect to load magnitude (truck position), and a vast majority of

recorded responses returned to zero, indicating that the structure was acting in a linear-elastic

manner. Some strain responses showed slight drift, but this was a result of the breezy

conditions during the field tests rather than non-linear behavior of the structure. Figure 1.2-1

displays the midspan strain response histories on Rib B in the south span for all truck paths.

Similarly, Figure 1.2-2 and Figure 1.2-3 display midspan displacements of the south span and

rotations near the north abutment for Rib E. All of the response histories had a similar

degree of reproducibility and linearity, indicating that the data collected was of good quality.

OBSERVED COMPOSITE BEHAVIOR: Top and bottom strain measurements taken at several

locations throughout the structure indicated that the ribs were behaving composite with the

deck during testing. Figure 1.2-4 shows a top and bottom gage response history from the

midspan of Rib E in Span 1, where it is clear that the top gage is located near the neutral axis,

indicative of composite behavior. Based on the structural plans, it was unclear if this

composite behavior was intended. Nonetheless, because the structure has retained this

composite action for nearly 70 years, it was considered reasonable to account for this

behavior in the field-verified rating as long as there is sufficient horizontal shear transfer

between the deck and ribs.

CONTINUITY BETWEEN SPANS: A notable amount of continuity was observed in the measured

responses, which was likely due to the ribs being cast integrally with the interior support

columns. Figure 1.2-5 displays the responses from a gage near an interior support on Rib D

for all truck paths. Continuity is typically identified as a negative response in a span while

the adjacent span is loaded. This important behavior was considered during the bridge

analysis.

ROTATIONAL RESTRAINT AT SUPPORT LOCATIONS: As expected, significant levels of end-

restraint were noted in the live-load responses due to the fixed-end nature of the rigid frame

design. Generally, end-restraint is observed as a negative response when the crossing truck is

away from the gage location but still on the same span, as shown in Figure 1.2-6. Often, end-


restraint cannot be relied upon for rating purposes because it tends to be impermanent and

unreliable under heavy loads. In this case however, the end-restraint is a result of the framed

connections at the ends of the ribs rather than friction between the superstructure and

substructure or a locked bearing. Therefore, this behavior was also found to be reliable

enough to consider throughout the bridge evaluation.

OUT-OF-PLANE BENDING: Due to the poor condition of the bottoms of the ribs, BDI was

forced to place the bottom strain transducers on the sides of the ribs rather than centered on

the bottoms, as is normal procedure. As a result, the strain sensors were somewhat subjected

to out-of-plane bending effects of the ribs in addition to the expected in-plane bending

effects. This was not a problem near the supports, but visibly affected the midspan gages as

shown in Figure 1.2-7. When the midspan strain responses (affected by out-of plane

bending) were directly compared to the corresponding midspan displacement responses

(which are NOT affected by out-of-plane bending), it was clear that the strain responses were

slightly distorted and the load distribution was subsequently affected. For this reason,

midspan displacement responses were weighed much more heavily than the midspan strain

responses during the finite-element model calibration process.

LATERAL LIVE LOAD DISTRIBUTION: The apparent lateral live-load distribution in each of the

spans was very good. Due to the heavy 42° skew of the structure the load distribution was

not symmetric between truck paths, but it did include nearly the entire width of the structure.

One exception to this was the longitudinal expansion joint in the deck between Ribs F and G.

Load test data indicated that this joint was indeed working as an expansion joint and very

little load was transferred from one side to the other. This is seen in Figure 1.2-8, which

compares two midspan displacement responses from Rib F; one is from a truck path on the

same side of the expansion joint, while the other is from a truck path on the opposite side of

the expansion joint. While some load transfer did occur, the relative magnitudes indicate that

the expansion joint was very flexible. Further evidence of movement in the expansion joint

was the visible cracking in the deck wearing surface directly above the expansion joint,

which is shown in Figure 1.2-9.

IMPACT/DYNAMIC EFFECTS: Data was recorded from one high-speed truck crossing (~55mph)

along Path Y2, and a direct comparison of the high-speed and slow-speed crossings was

made to provide a qualitative assessment of the dynamic effects. The intent of this test was

not to obtain a field based impact factor, but rather to indicate the extent of conservatism

applied by the design code impact factors. It should be noted that a considerable amount of

additional testing including different vehicles and vehicle speeds would be required to obtain

a realistic impact factor. Figure 1.2-10 shows the midspan strain histories of Rib E for the

slow and high speed tests along Path Y2. The high-speed test was found to produce very

similar peak strains as the slow speed tests, with the primary cause of variation being slight

lateral offset between the two types of tests. This offset was due to the difficultly involved in

maintaining the exact same truck position while traveling at 55 mph. Overall, the dynamic

component of the high speed tests was negligible, which indicates that the LRFD

specification of 33% for dynamic amplification is rather conservative. This very low

observed impact is noteworthy since significantly larger dynamics were recorded during the

2009 testing (see Figure 1.2-11). It should be noted that the test truck used in the 2009 testing

was approximately 18 kips lighter than the truck used in the 2012 testing, which would

explain some of the reduction in dynamics (i.e., typically the heavier the vehicle the smaller

the dynamics). However, the majority of this change in behavior is believed to be caused by


the new asphalt overlays at each of the bridge’s approaches, as shown in Figure 1.2-12,

which now allow traffic to make smoother transitions when traveling on and off the bridge.

COMPARISON BETWEEN 2009 & 2012 LOAD TEST RESPONSES: It was found the structure’s

responses and corresponding behavior did not significantly change in the year and a half that

past between the two sets of load tests. This can be observed in the response comparisons

provided in Figure 1.2-13 through Figure 1.2-16. Note that since the truck weights varied

substantially between the two tests, the 2009 test data was adjusted by the ratio between the

rear-axle weights used in the two different test sets (1.43). This adjustment helped provide a

somewhat normalized comparison. Although this qualitative comparison provided evidence

that the structural live-load behavior had not significantly changed, possible changes in

structural behavior were further investigated during the modeling calibration process.


Figure 1.2-1 Linear elastic behavior and reproducibility of test strains.

Figure 1.2-2 Linear elastic behavior and reproducibility of test displacements.

Path Y4 Responses

Path Y3 Responses

Path Y2 Responses

Path Y1 Responses

Path Y4 Responses

Path Y3 Responses

Path Y2 Responses

Path Y1 Responses


Figure 1.2-3 Linear elastic behavior and reproducibility of test rotations.

Figure 1.2-4 Example of observed composite behavior.

Low response in top

gage indicates that

gage is near neutral

axis


Figure 1.2-5 Example of continuity between spans.

Figure 1.2-6 Example of end-restraint at the abutments.

Negative moment near the

abutment while the truck is

still in the span indicates

end-restraint

Negative moment near the

pier while the truck is in

the adjacent span indicates

continuity between spans


Figure 1.2-7 Example of out-of-plane bending effects on midspan strains.

Figure 1.2-8 Load transfer across longitudinal expansion joint between Ribs F and G.

Larger Strain Response under Truck Path

Y4 Loading due to out-of-plane bending

effects

Larger Vertical Displacement Response

under Truck Path Y3 loading since out-of-

plane bending is not involved in this

measurement type

Displacement response when

directly loaded

Displacement response when load is

across deck joint


Figure 1.2-9 Full-length cracking in wearing surface directly above expansion joint (2009

testing).

Figure 1.2-10 2012 Load Test - Slow and high-speed strain response comparison

(impact/dynamic effects).

2012 High Speed Test

Data


Figure 1.2-11 2009 Load Test - Slow and high-speed strain response comparison

(impact/dynamic effects).

Figure 1.2-12 Picture of new approach bituminous overlay (Source: 2011 inspection

report).


Figure 1.2-13 Load Test Response Comparison – Midspan Strain – Span 1 – rib F.

Figure 1.2-14 Load Test Response Comparison – Midspan Strain – Span 1 – rib E.


Figure 1.2-15 Load Test Response Comparison – Midspan Displacement – Span 1–Rib E.

Figure 1.2-16 Load Test Response Comparison – Midspan Displacement – Span 2–Rib E.


2. RATING ANALYSIS ASSUMPTIONS AND CRITERIA

2.1 MODE LING, ANALYSIS, AND DATA CORRELATION

The primary goals of creating a field-calibrated finite-element model of a structure are to 1)

gain a better understanding of its current condition and behavior; 2) accurately predict its

response to any load configuration; and 3) subsequently evaluate the structure’s ability to safely

carry the given load configurations. To achieve these goals, the analytical model must first be

constructed and modified so that it reproduces the structural responses measured under a known

load. This section briefly describes both the methods and findings of the modeling of the

Louisquisset Pike Bridge. A list of modeling and analysis procedures specific to this bridge are

provided in Table 2.1-1.

NOTE: The procedures described below were first used during the modeling process for the

bridge analysis performed in 2009. The most recent 2012 analysis was started using the 2009

calibrated model as the initial reference point. All of the modeling assumptions in this older

model were reviewed and compared to the newly obtained data to determine if any of the

structural behavior changed between the two test sets.

MODELING PROCEDURES: 2.1.1

First, insight gained from the qualitative data investigation, described in Section 1.2, was used

to create an initial finite-element model. Note that the data review was purely qualitative and was

performed by simply analyzing the data in graphical form. A qualified and experienced engineer

visually detected key behaviors, both typical and atypical, that were deemed to be significant

enough to be taken into account during the modeling process. This identification of key

variables/behaviors was an important step, as it dictated the general direction of the modeling

process.

Figure 2.1-1 2-D plan view of FE model with truck loading at the abutment.

A quasi three-dimensional analytical model of the structure, shown above in Figure 2.1-1, was

created using BDI’s WinGEN finite-element modeling software. Once the initial model was

created, the load test procedures were then reproduced using BDI’s WinSAC structural analysis

and data correlation software. This was done by moving a two-dimensional “footprint” of the

test truck across the model in consecutive load cases, illustrated on the left side of Figure 2.1-1,

which reproduced the tests run along the designated truck paths used in the field.


Additionally strain, displacement, and rotation sensor locations were defined on the model

having the same sensor identifications and locations that were employed in the actual load test.

The analytical responses of this simulation were then compared to those measured during the

load tests to initially validate all the data input into the model. After the initial model’s input was

determined to be accurate, it was then calibrated until an acceptable match between the measured

and analytical responses was achieved. This calibration involved an iterative process of

optimizing certain material properties and boundary conditions until the structure was

appropriately and realistically modeled.

The following are descriptions of some of the modeling procedures/assumptions used in the

analysis of the Louisquisset Pike Bridge:

RIB SECTIONS: The rigid ribs in both spans were broken into 54 sections each, essentially

creating individual one-foot beam segments. This amount of refinement allowed for an

accurate representation of the parabolic nature of the ribs, and enabled the precise assignment

of specific capacities. This was extremely important as load ratings of reinforced concrete

structures are often governed by changes in moment steel or changes in the shear steel stirrup

spacing.

The shims (“haunch” or gap fillers) above the ribs in Span 1(northern span) were modeled as

12” wide rectangles placed on top of the beams. The respective depths of each shim element

were calculated based on the structural plans and were modeled accordingly. This modeling

procedure helped account for any additional stiffness provided by the “haunch” and made the

dead load responses much more accurate. Likewise, the small haunch above the ribs in Span

2 was also modeled, although this did not have as significant of an effect.

DECK: The deck sections were modeled with shell elements and assigned their respective

thicknesses to account for the varying stiffness values and dead load effects. The expansion

joint between Ribs F and G was modeled as a very narrow strip of plate elements with an

extremely low stiffness. Note that any interaction with the eastern bridge structure was not

modeled, although the dead load from the connecting slab was included for rating.

The sidewalk was modeled as a single plate element spanning from Ribs A and B, and was

assigned a very low stiffness. According to the as-built plans, the sidewalk is “resting” on

top of the main deck slab with expansion material between the two elements. This means

that very minimal live-load applied to the roadway will get transferred to the exterior fascia

rib (Rib A), but the dead load from the sidewalk was still applied to Ribs A and B for rating.

SUPPORT LOCATIONS: The abutment legs and pier columns were modeled as springs at the

respective center of bearings of the ribs. The springs were initially given rotational stiffness

based on simple column stiffness calculations, and were later optimized to pinpoint the actual

effective rotational restraint.

The rib elements spanning between the center of bearings and the springline of the ribs

(width of the columns) were assigned extremely high stiffness values. In reality, these

sections are still part of the abutment legs and/or pier columns, so bending effects in these

regions were considered to be negligible.


Table 2.1-1 Analysis and model details.

ANALYSIS PARAMETER ANALYSIS DETAILS

ANALYSIS TYPE - Linear-elastic finite element - stiffness method.

MODEL GEOMETRY - Quasi-3D composed of shell elements, eccentric beam elements, and

translational and rotational springs.

NODAL LOCATIONS

- Nodes placed at the ends of all frame elements.

- Nodes at all four corners of each plate element.

-Nodes placed at each spring location.

MODEL COMPONENTS

- Plates for all deck, sidewalk, and expansion joint elements.

- Frame elements for ribs and diaphragms.

- Non-eccentric springs with both translational and rotational stiffness

representing each rib’s bearing condition.

LIVE-LOAD - 2-D footprint of test truck consisting of 10 vertical point loads. Truck paths

simulated by series of load cases with truck moving at 2-foot increments.

DEAD-LOAD

- Self-weight of structure.

- 35 lb/ft2 to account for the 3” bituminous wearing surface.

- 338 lb/ft applied to Rib I to account for the deck panel connecting the west

bridge structure to the east bridge structure.

TOTAL NUMBER OF

STRAIN COMPARISONS - 56 gage locations x 296 load positions = 16,576 response comparisons

MODEL STATISTICS

- 3,842 Nodes

- 5,848 Elements

- 233 Cross-section/Material types

- 296 Load Cases

- 56 Gage locations

ADJUSTABLE

PARAMETERS FOR MODEL

CALIBRATION

1. Effective Modulus: Ribs (E)

2. Effective Modulus: Deck (E)

3. Effective Modulus: Deck over interior pier (E)

4. Effective Modulus: Sidewalk (E)

5. Rotational Stiffness: North Abut Spring (My)

6. Rotational Stiffness: Pier Springs (My)

7. Rotational Stiffness: South Abut Springs (My)

8. Torsional Stiffness: Abut Wall (J)

MODEL CALIBRATION RESULTS 2.1.2

The goal of the calibration process was to accurately match the responses at every gage

location for every load condition by modifying various stiffness parameters of the model. The

same level of importance was applied to the minor load responses as was applied to the

maximum values. Realistic representation of the load transfer could only be verified by matching

responses throughout the entire structure with complete load cycles.

The optimization process relies on an engineer’s ability to determine what stiffness values

might be different than what is typically assumed. The engineer must also define reasonable

upper and lower limits for each variable. This process usually entails visual examination of the

response comparison histories and determining what structural parameters would influence the

response behavior so as to obtain a better correlation. Typically, there are many manual


iterations determining the correct set of properties to adjust and is a function of the engineer’s

experience and the complexity of the structure. An optimization algorithm built into the analysis

program then automates the iterations so as to obtain the stiffness values that provide the best

solution.

The following outline describes what stiffness parameters were adjusted, along with

discussions of the effect on the structural performance.

Rib Stiffness: Modeling of R/C elements must take into account any slight modeling errors

(i.e., actual member size, actual haunch properties, etc.) as well as any variability in

properties such as crack quantity and density, depth of rebar, actual strength of concrete, etc.

As a result, the calibrated stiffness properties are the “effective properties”, and may not be

the “actual” material properties. For example, the overall Young’s Modulus of the ribs was

most likely in the range of 3,000-3,500 ksi, but an “effective” modulus of 4,500 ksi was

obtained due to the low response magnitudes observed in the live-load tests.

It should also be noted that all rib element stiffness values were optimized together as one

collective parameter. Because it would be impossible to optimize the stiffness of each beam

segment individually due to the extreme variability of structural degradation, it was deemed

most appropriate to develop one overarching rib stiffness value. This procedure produced an

“average” stiffness that most accurately represented the rib system as a whole. Note that this

stiffness was primarily based on the global type measurements (e.g., midspan displacement

and rotations near the supports), which were considered to be more reliable than the strain

measurements and overall had a very high correlation with the final model (R2=0.990).

Deck Stiffness: Similar to the rib optimization approach, the deck sections including the

sidewalk were optimized to achieve the “effective deck stiffness”. This optimization mostly

affected the lateral load distribution characteristics of the structure. Because the continuity

computed near the interior support using the 2009 final model was overestimated when

considering the 2012 data, the deck near the interior pier was optimized separately from the

other deck elements. The optimized stiffness value for the typical deck of about 3500 ksi

was within in the expected range and produced lateral load distribution characteristics very

similar to those obtained from the load tests (see Figure 2.1-15). Additionally, the low deck

stiffness value near the pier of approximately 450 ksi provided evidence that the deck was

more flexible over this support; which indicates the deck had a high density of cracks in the

negative moment region.

As previously mentioned, the expansion joint and sidewalk elements were optimized

separately from the main slab due to their different geometric and material properties. The

expansion joint was optimized manually to generate the correct load transfer characteristics.

The optimized value of nearly zero stiffness indicated that it was indeed behaving as a true

expansion joint and very little load was transferred from one side to the other. Similarly, the

stiffness of the sidewalk optimized to a negligible value, which indicated that the exterior

fascia girder (Rib A) was carrying little to no live load. This was entirely expected due to the

construction details previously discussed in the Modeling Procedures subsection.

Support Spring Stiffness: As expected, this structure had a significant amount of end-restraint

at the abutments and pier due to the rigid frame design. Although estimated rotational

stiffness values were assigned in the initial model based on the column dimensions, all spring

stiffness values were optimized to account for variations due to additional factors such as

connection details, cracking in the pier columns, or soil pressure behind the abutment legs.


In fact, all rotational stiffness values increased from their theoretical levels, indicating a very

high degree of fixity at all support locations.

It should be noted that the end-restraint at the south abutment was calibrated to be

approximately 30% less than the optimized value from the 2009 analysis; while the north

abutment and pier springs were found to be similar (within 10%) between the 2009 and 2012

testing. Overall, the calibrated spring constants decreased in the more recent analysis.

This change in optimized behavior could have been caused by a variety of factors including

the fact that the rotation sensors were not used in the previous 2009 testing, from which

rotational restraint can best be captured. Additionally, the 2009 and 2012 tests were

performed at different times of the year with very different ambient conditions. Regardless of

what caused this change in behavior, this rotational restraint was reduced further for rating in

order to ensure conservative rating values.

Following the optimization procedures, the model produced a correlation coefficient of 0.974,

which can be considered an excellent match for a reinforced concrete structure and especially for

one that is in such poor visible condition. The parameter and model accuracy values obtained

with the 2012 load test data in the initial field verified model, in the 2009 final calibrated model,

and in the 2012 final calibrated model are provided in Table 2.2.

The final 2012 model closely matched the member displacements, strains, and rotations, as

shown in the comparison plots provided in Figure 2.1-2 through Figure 2.1-14. Note that in

these comparison plots the measured responses are represented as solid lines while the computed

responses are shown as discrete markers of similar color. Additionally, the model’s midspan

lateral distribution of displacement closely matched that of the actual structure as shown in

Figure 2.1-15. The response values shown in this figure correspond to the longitudinal load

positions producing the maximum responses at Section 2-2 for each load path. Note that in this

distribution plot the computed displacement values are defined as “Analysis Path #” in the

legend while the measured responses were defined as the corresponding data file name (e.g.,

Br276_Y1_2).


Table 2.2 Model accuracy & parameter values.

MODELING PARAMETER INITIAL FIELD-VERIFIED

MODEL W/ 2012 DATA

2009 FINAL CALIBRATED

MODEL W/ 2012 DATA

2012 FINAL CALIBRATED

MODEL W/ 2012 DATA

Effective Modulus

- R/C Ribs E [ksi]

- Deck E [ksi]

- Deck over pier E [ksi]

- Sidewalk E [ksi]

3,200

3,200

3,200

1,000

4,496

2,936

2,936

0.7

4,500

3,525

450

0.1

Spring Rotational Stiffness

- North Abutment My [kip-in/rad]

- Pier My [kip-in/rad]

- South Abutment My [kip-in/rad]

8.00E6

2.00E6

8.00E6

5.04E+07

1.92E+07

3.46E+07

4.64E+07

1.71E+07

2.31E+07

Effective Torsional Stiffness

- Abutment Wall J [in4]

69,120

2,549,000

897,800

ERROR PARAMETERS ALL DATA ALL DATA ALL DATA

Absolute Error 106,380.3 30,327.7 29,938.7

Percent Error 97.2% 6.2% 6.4%

Scale Error 7.7% 3.3% 2.9%

Correlation Coefficient 0.960 0.971 0.974

ERROR PARAMETERS ALL DATA BUT TOP GAGES ALL DATA BUT TOP GAGES ALL DATA BUT TOP GAGES

Absolute Error 102,759.5 27,367.5 27,265.1

Percent Error 97.1% 5.8% 6.1%

Scale Error 7.3% 2.5% 2.2%

Correlation Coefficient 0.960 0.973 0.976


Figure 2.1-2 Example strain comparison– Section 1-1 - All Truck Paths.

Figure 2.1-3 Example rotation comparison– Section 1-1 - All Truck Paths.



Figure 2.1-5 Example displacement comparison– Section 2-2 - All Truck Paths.



Figure 2.1-13 Example displacement comparison– Section 7-7 - All Truck Paths.



Figure 2.1-15 Midspan Lateral Load Distribution Comparison- Section 2-2 - All Truck

Paths.


2.2 LOAD RATING PROCEDURES

The end goal of producing an accurate model was to predict and evaluate the structure's actual

live-load behavior when subjected to design or rating loads. This approach is essentially

identical to standard load rating procedures except that a "field verified" FE model is used

instead of a typical girder-line analysis. This section briefly discusses the load rating procedures.

Once a finite-element model has been calibrated to field conditions, engineering judgment

must be used to address any existing conditions that may change over time or that may be

unreliable/unrealistic at the ultimate strength limit state and/or under heavy loads. In this case,

the parameters that were adjusted for rating were the calibrated rotational restraint at the supports

and the deck stiffness near these regions.

In the rating model, deck elements were “cracked” near the abutments and the interior pier in

order to simulate the expected condition of the deck at ultimate state. This cracking near the

supports was modeled by reducing the deck stiffness near the supports to an extremely low value

(50 ksi). This assumption ensured non-composite negative moment responses for the ribs, and

likewise helped produce conservative positive moment ratings. Next the rotational restraint at the

supports was reduced by 25% to ensure that this behavior was not overestimated during the

rating process. It was found that this restraint reduced by 10-30% between the 2009 and 2012

tests. It should be noted that the 2009 load tests were performed in July while the 2012 tests were

performed in January. Some of the observed variation in behavior was thought to due to the

different ambient conditions present during these different times of the year. Regardless of what

caused this change in behavior, the additional 25% reduction in rotational restraint was found to

be a conservative assumption with respect to positive flexure.

Due to the composite behavior observed in the live-load tests, it was necessary to determine if

this behavior could be relied upon for rating. It was found that very little reinforcement that

connects the deck to the ribs was present (typically double #4 bars at 32”), which led to the

conclusion that the structure was possibly designed as a non-composite structure. It was

desirable however, to produce a load rating that was consistent with the structural performance

observed during the load tests. The fact that the ribs were fully composite during both sets of

load tests means that these members have been able to retain their composite action for nearly 70

years with a wide range of loading conditions. If the bond between the ribs and the deck had

previously broken, it would have been detected during the load tests. Therefore an examination

of a composite load rating was warranted. Justification for composite action was determined by

investigating the horizontal shear transfer at the bonds between the deck and ribs and between

the concrete shims (gap fillers) in the north span and the ribs.

To validate the use of T-beam type sections for capacity, the ribs were evaluated in terms of

their ability to transfer horizontal shear to the deck. This was accomplished by calculating the

interface (horizontal) shear resistance of the bond between the ribs/deck and the shims (5.8.4.1 of

the LRFD Specs). The cohesion factor, c, and the friction factor, µ, necessary for calculating the

interface shear resistance of the concrete and reinforcing steel were taken at 0.24 ksi and 1.0,

respectively. The use of these factors was based on the assumption of “normal-weight concrete

placed against a clean concrete surface, free of laitance, with surface intentionally roughened to

an amplitude of 0.25in.” It should be noted that there was a change in this portion of the

AASHTO LRFD specs between the third and fifth edition, in which the cohesion factor for this

assumed case was changed from a value of 0.1 ksi to 0.24 ksi. This change in the expected


cohesion actually altered the conclusion of the composite behavior evaluation previously made

during the 2009 rating procedures. Since the cohesion was more than doubled in the most recent

edition of the LRFD spec, it was determined that the roughened shims and the small amount of

reinforcement in these regions provided enough shear transfer for the ribs to be considered

composite with the deck throughout the structure. Therefore, the observed composite behavior

was validated using the LRFD specs and the subsequently used for rating. Note, design non-

composite design ratings were provided as a general reference.

Moment and shear capacities were calculated for all interior rib segments using the AASHTO

LRFD Bridge Design Specifications 5th

Edition – 2010 and ACI 440.2R-08. Structural as-built

plans, multiple inspection reports, CFRP retrofit drawings and design details, and a 2009 rating

report were provided to BDI by AECOM, and were also used as resources. The following

assumptions were made during the rating of this structure:

Based on the age of the structure and information provided in the previously mentioned

sources, the reinforcing steel yield strength was assumed to be 33 ksi while the concrete

compressive strength was assumed to be 2.5 ksi.

The positive and negative moment reinforcing bars were assumed to be #11’s rather than

the 1 ½” square bars specified in the plans. This was based on visual evidence of round

bars taken from several pictures of spalled areas on the ribs.

A 10% section loss in the positive moment reinforcement was assumed for all sections

during the calculation of the positive moment capacities, with the exception of the CFRP

strengthened sections. This somewhat conservative assumption was based on the most

recent inspection, which showed regions with approximately 10% section loss of this

bottom reinforcement.

Positive moment capacities used for the primary ratings assumed T-beam sections

(composite). As additional analysis, capacities were also calculated for the beams based on

rectangular sections (non-composite). This was done to provide AECOM with an estimate

of the bridge ratings (HL-93 only) if the composite behavior of the structure were to

dissipate.

Positive moment capacities in the CFRP strengthened sections assumed that no extra

strength was provided in the 2’-0” CFRP development regions that contain the additional

CFRP in a U-wrap around the sides of the ribs. Additionally, it was assumed that the CFRP

was fully developed in the 10’ between the development regions.

All negative moment capacities were calculated based on the steel near the top of the ribs

only and did not consider the reinforcement present in the deck. This slightly conservative

assumption was made based on the notion that the deck near the supports would be heavily

cracked at the ultimate strength state which may cause the ribs and the deck to start acting

independently.

The shear capacity of the superstructure was taken as the minimum of the available vertical

shear capacity of the ribs themselves and the available vertical shear capacity based on the

interface shear transfer between the deck and the ribs (through the shims in Span 1). It was

determined that the shear capacity of the ribs themselves controlled over the capacities

based on the interface shear capacity; therefore the shear capacities used for rating were

based solely on the ribs themselves.


The ribs’ shear capacities were based on the Simplified Procedure for Nonprestressed

Sections given in Section 5.8.3.4.1 of the previously referenced manual.

Based on the “poor” condition of the ribs and the deck as specified in the 2007 inspection

report, a condition factor of 0.85 was used for all ratings, even the positive moment ratings

of the CFRP strengthened section.

The live-load factors for the legal and permit loads were based on the ADTT of 3500

(based on the inspection report).

An impact factor of 33% was applied to all live-load responses with the exception of two

RIDOT permit vehicles (RI-OP3 and RI-OP4) that specify a maximum impact factor of

20%. This assumption was found to be conservative since during the 2012 load tests

negligible dynamics were recorded during the high speed test. This was notable since fairly

high dynamics were recorded during the 2009 tests. The new approaches, completed

between the 2009 and 2012 tests, were the likely cause of the reduction in dynamics. Since

the dynamic behavior could change over time due to deterioration of the approaches, it was

decided that the standard AASHTO impact factors should be used for rating

The Service I rating factors did not consider the reinforcing steel stress limit of 0.90Fy, but

rather utilized the option to limit unfactored moments to 75% of the nominal flexural

capacity. This option is provided in Section C6A.5.4.2.2b of The Manual for Bridge

Evaluation 1st Edition.

All of the cross-section dimensions, reinforcing information, and material properties used in

calculating capacities are provided in an accompanying spreadsheet

(RI276_XSections_Capacities_2012.xls). Moment and shear capacity values for a few selected

locations have also been provided in the report in Table 2.2-1 through Table 2.2-6.

Load ratings were performed on the revised calibrated model according to AASHTO LRFR

methods (see Table 2.2-7 for load factors and impact factors corresponding to the applicable

limit states). Lateral vehicle positions were defined per AASHTO specifications in Section

3.6.1.1.1 of the AASHTO LRFD Bridge Design Specifications 5th

Edition. This section declares

that in situations where the traffic lanes are less than 12.0 ft. wide, the number of design lanes

shall be equal to the number of traffic lanes and subsequently the width of the design lane shall

be taken as the width of the traffic lane. For rating purposes, the rating traffic lanes were

assumed to be in the same position as the current traffic lanes, and the design truck was assumed

to be located anywhere within its lane, as long as the minimum 4.0 ft spacing was maintained

between trucks. A summary of lateral load positions and load combinations can be seen below

in Figure 2.3-1, Figure 2.3-2, and Figure 2.3-3. Multiple presence factors were applied to one

lane, two lane, and three lane loading conditions as 1.2, 1.0, and 0.85 respectively. Figure 2.3-5

through Figure 2.3-7 provide summaries of the AASHTO rating vehicles and RIDOT Permit

Load rating vehicles used in the rating process, while Figure 2.3-4 provides the HL-93 design

loading configurations. It is important to note that the RI-OP1, RI-OP2, and RI-OP3 permit

truck ratings were calculated using a single lane loading condition only and did not include the

1.2 single-lane multiple presence factor as per RIDOT LRFR Guidelines.

Structural dead loads were automatically applied by the modeling program’s self-weight

function. An additional dead load of 35 lb/ft2 was applied to entire roadway to account for the 3”

thick bituminous wearing surface, and another dead load of 338 lb/ft was applied to Beam 9 to

account for the weight of the independent slab section connecting the east and west bridge

structures.


Table 2.2-1 Selected rib segment positive moment T-beam capacities (ΦMn, k-in).

MEMBER NUMBER OF

BARS

EFFECTIVE

AREA OF

STEEL, (IN2)

DEPTH TO

STEEL (IN)

EFFECTIVE

FLANGE

WIDTH (IN)

FACTORED

MOMENT

CAPACITY

(KIP-IN)

Span 1, Midspan 5 7.02 55.8 60 9,718

Span 1, Edge of

fully developed

retrofit – Pier side*

2 2.81 55.4 60 3,898

Span 2, Midspan 5 7.02 37.7 60 6,510

Span 2, Edge of

fully developed


2 2.81 47.0 60 3,302

* - Capacity locations represent sections without CFRP at edge of the fully developed retrofit

section closest to the pier.

Table 2.2-2 Selected rib segment negative moment capacities (ΦMn, k-in).

MEMBER NUMBER OF

BARS

AREA OF

STEEL, (IN2)

DEPTH TO

STEEL (IN)

EFFECTIVE

FLANGE

WIDTH (IN)

FACTORED

MOMENT

CAPACITY

(KIP-IN)

Span 1,

Face of Abut 5 7.80 63.2 24 11,947

Span 1,

Face of Pier 8 12.48 62.5 24 18,416

Span 2,

Face of Abut 5 7.80 63.2 24 11,947

Span 2,

Face of Pier 8 12.48 62.5 24 18,416


Table 2.2-3 Selected CFRP strengthened rib segment positive moment T-Beam capacities

(ΦMn, k-in).

MEMBER

STRENGTH

REDUCTION

FACTOR Φ**

EFFECTIVE

AREA OF

STEEL,

(IN2)

AREA OF

CFRP

(IN2)

DEPTH TO

STEEL (IN)

FACTORED

MOMENT

CAPACITY

(KIP-IN)

Span 1, Center of

Retrofit 0.814 7.02 1.92 53.3 6,831

Span 1, Edge of

fully developed


0.815 2.81 1.92 54.8 7,025

Span 2, Center of

Retrofit 0.811 7.02 1.92 41.4 5,299

Span 2, Edge of

fully developed


0.812 2.81 1.92 45.7 5,853

* - Capacity locations represent sections strengthened with CFRP at edge of the fully developed

retrofit section closest to the pier.

** - Strength reduction factors were calculated according to Equation 10-5 of ACI 440.2R-08

which was based on a relationship between the strain in the steel and the steel’s yielding strain.

Table 2.2-4 Selected rib segment non-composite positive moment capacities (ΦMn, k-in).

MEMBER NUMBER OF

BARS

EFFECTIVE

AREA OF

STEEL, (IN2)

DEPTH TO

STEEL (IN)

EFFECTIVE

FLANGE

WIDTH (IN)

FACTORED

MOMENT

CAPACITY

(KIP-IN)

Span 1, Midspan 5 7.02 27.1 24 4,390

Span 1, Edge of

fully developed

retrofit – Pier side

2 2.81 37.1 24 2,840

Span 2, Midspan 5 7.02 27.6 24 4,932

Span 2, Edge of

fully developed

retrofit – Pier side

2 2.81 36.5 24 2,519


Table 2.2-5 Selected non-composite negative moment capacities (ΦMn, k-in).

MEMBER NUMBER OF

BARS

AREA OF

STEEL, (IN2)

DEPTH TO

STEEL (IN)

EFFECTIVE

FLANGE

WIDTH (IN)

FACTORED

MOMENT

CAPACITY

(KIP-IN)

Span 1,

Face of Abut 5 7.80 62.7 24 -11,848

Span 1,

Face of Pier 8 12.48 61.6 24 -18,147

Span 2,

Face of Abut 5 7.80 62.7 24 -11,848

Span 2,

Face of Pier 8 12.48 61.6 24 -18,147

Table 2.2-6 Selected rib segment vertical shear capacities (ΦVn, kips).

MEMBER NUMBER OF

STIRRUPS

AREA OF

STEEL, (IN2)

STIRRUP

SPACING

(IN)

EFFECTIVE

SHEAR

DEPTH

EFFECTIVE

VERTICAL

SHEAR

CAPACITY

(KIPS)

Span 1,

~10 from Abut 2 0.44 18 40.4 96.7

Span 1,

~10’ from Pier 2 0.44 18 37.8 90.6

Span 2,

~10 from Abut 2 0.44 18 40.4 96.7

Span 2,

~10’ from Pier 2 0.44 18 37.8 90.6


Table 2.2-7 AASHTO LRFR Applied load factors.

LIMIT STATE DESCRIPTION LOAD/IMPACT

FACTOR

Strength I

γDC (Structural Component) 1.25

γDW (Field-Verified Wearing Surface) 1.50

γLL (Design Load - Inventory Level) 1.75

γLL (Design Load - Operating Level) 1.35

γLL (Legal Loads) 1.75

Design Load Impact Factor 33%

Legal Load Impact Factor 33%

Strength II


γDW (Field-Verified Wearing Surface) 1.50

γLL (Blanket Permit) 1.75

γLL (Single-Trip Permit) 1.46

Impact Factor (<150kips) 33%

Impact Factor (>150 Kips) 20%

Service I


γDW (Wearing Surface) 1.0

γLL (All Permit Loads) 1.0

Impact Factor (<150kips) 33%

Impact Factor (>150 Kips) 20%


2.3 TRUCK LOAD COMBINATIONS AND CONFIGURATIONS

Figure 2.3-1 Three-lane loading combinations.


Figure 2.3-2 Two-lane loading combinations.


Figure 2.3-3 Single-lane loading combinations.


Figure 2.3-4 HL-93 design loading configurations (AASHTO MBE).


Figure 2.3-5 AASHTO Legal Live Load Truck Configurations.


Figure 2.3-6 AASHTO Specialized Hauling Live Load Truck Configurations.


Figure 2.3-7 Rhode Island Permit vehicle configurations (RIDOT LRFR Guidelines).


3. EVALUATION OF RATING AND RECOMMENDATIONS

3.1 LOAD RATING RESULTS:

A complete set of load ratings, which consisted of all rating vehicles and limit states, was

performed using the adjusted rating model, as explained in the previous section. In general, the

critical ratings were controlled by shear in a Span 2 interior rib near the pier at the location where

the stirrup spacing changes from 12” to 18”. Note that all of the critical shear ratings were

controlled by the edge one-lane loaded condition.

The critical inventory level load ratings for the HL-93 design loading were found to be

unsatisfactory (RF<1.0) for all rated actions (M+, M-, V); however the LRFR design operating

level ratings were found to be nearly satisfactory for all actions (note: the critical HL-93

operating level rating for shear was nearly satisfactory at RF=0.96). Deficient HL-93 load ratings

were expected since this structure was built in 1942 and therefore not designed to current

AASHTO LRFD standards.

All of the AASHTO legal loads (H20 truck, “Type 3” trucks, and the specialized hauling

“SU” vehicles) had satisfactory ratings with the one exception being the SU7 rating for negative

moment of 0.97. These results indicate all trucks that fit within the AASHTO legal load

envelope can safely cross the structure at normal speed.

It was found that the majority of the RIDOT permit loads had unsatisfactory rating factors

with the exception of the RI-OP2 and RI-OP3 trucks. The critical permit rating of 0.63 was

controlled by shear under the loading of the blanket permit truck RI-BP4. These results shows

that the majority of the RIDOT permit trucks cannot safely cross the structure at normal speed.


Table 3.1-1 Critical ratings and responses for Strength I and II limit states.

LIMIT

STATE RATING VEHICLE

POSITIVE MOMENT NEGATIVE MOMENT VERTICAL SHEAR

RF Tons Responses*

RF Tons Responses*

RF Tons Responses*

DL LL DL LL DL LL

ST

RE

NG

TH

I

HL-93

(comp)

Inventory 0.84 N/A 2188 2096

0.75 N/A -4509 -3550

0.74 N/A 39.6 23.9

Operating 1.09 0.97 0.96

HL-93

(non-comp)

Inventory 0.48 N/A 2203 1471

0.42 N/A -6078 -4319

0.68 N/A 41.5 24.5

Operating 0.62 0.54 0.88

H20 1.26 25.2 433 1142 1.51 30.2 -4526 -1764 1.22 24.4 39.6 14.5

Type 3 1.39 34.8 588 975 1.28 32.0 -4526 -2082 1.16 29.0 39.6 15.3

Type 3S2 1.44 51.8 433 1005 1.22 43.9 -4526 -2172 1.21 43.6 39.6 14.6

Type 3-3 1.88 75.2 433 766 1.30 52.0 -4526 -2048 1.29 51.6 39.6 13.6

SU4 1.34 36.2 433 1230 1.32 35.6 -4526 -2313 1.17 31.6 39.6 17.3

SU5 1.30 40.3 433 1273 1.18 36.6 -4526 -2585 1.08 33.5 39.6 18.7

SU6 1.19 41.4 433 1384 1.06 36.8 -4526 -2878 1.06 36.8 39.6 19.0

SU7 1.13 43.8 433 1461 0.97 37.6 -4526 -3140 1.00 38.8 39.6 20.2

ST

RE

NG

TH

II

RI-BP1 0.82 31.2 588 1655 0.82 31.2 -4526 -3245 0.71 27.0 39.6 24.9

RI-BP2 0.90 33.8 588 1514 0.82 30.8 -4526 -3230 0.75 28.1 39.6 23.6

RI-BP3 0.87 45.6 433 1648 0.67 35.1 -4526 -3960 0.72 37.7 39.6 24.7

RI-BP4 1.04 67.6 433 1387 0.82 53.3 -4526 -3249 0.63 41.0 36.5 30.5

RI-OP1 1.07 60.5 588 1517 0.89 50.3 -4610 -3541 0.88 49.7 39.6 24.1

RI-OP2 1.45 116.0 560 1257 1.41 112.8 -4508 -2510 1.02 81.6 39.6 23.0

RI-OP3 1.70 192.1 560 1073 1.13 127.7 -4508 -3152 0.96 108.5 39.6 24.4

* - The responses provided in this table are un-factored but do include impact considerations.


Table 3.1-2 Critical ratings and responses for Service I limit state.

Limit State Rating Vehicle

Positive Moment Negative Moment

RF Tons Responses*

RF Tons Responses*

DL LL DL LL

Service I

RI-BP1 1.45 55.1 433 1751 1.64 62.3 -4526 -3245

RI-BP2 1.59 59.6 433 1605 1.65 61.9 -4526 -3230

RI-BP3 1.55 81.2 433 1648 1.35 70.7 -4526 -3960

RI-BP4 1.58 102.7 1603 1661 1.64 106.6 -4526 -3249

RI-OP1 1.60 90.4 588 1517 1.49 84.2 -4609 -3540

RI-OP2 1.84 147.2 1586 1434 2.13 170.4 -4508 -2510

RI-OP3 2.03 229.4 1586 1302 1.70 192.1 -4508 -3152

* - The responses provided in this table are un-factored but do include impact considerations.


3.2 CONCLUSIONS AND RECOMMENDATIONS

Load test results indicated that the live-load responses were of good quality and also provided

evidence that the bridge was acting in a linear-elastic manner, despite the fact that severe

degradation was observed at several locations on the superstructure. A very good correlation

was obtained by the linear-elastic analysis after the calibration process, further indicating that all

responses were linear. Lastly, it was found that the test truck crossed the structure at 55 mph

without causing significant dynamic effects. This observation indicates that the use of the

AASHTO standard 33% impact factor resulted in conservative ratings.

Overall, it was found during the qualitative data review that the structural responses did not

significantly change between the 2009 and 2012 tests. However, during the model calibration

process it was found that the optimized rotational restraint at the supports did in fact reduce by a

noteworthy amount (10-30%). This change in optimized behavior could have been caused by a

variety of factors including the fact that the rotation sensors were not used in the previous 2009

testing, from which rotational restraint can best be captured. Additionally, the 2009 and 2012

tests were performed at different times of the year with very different ambient conditions.

Regardless of what caused this change in behavior, this rotational restraint was reduced further

for rating in order to ensure conservative rating values.

During both sets of load tests (2009 & 2012), the ribs were found to be acting fully composite

with the deck; which means that these members have been able to retain their composite action

for 70 years with a wide range of loading conditions. This observed behavior was validated in

terms of capacity by evaluating the ribs based on their ability to transfer horizontal shear to the

deck. It was found based on the AASHTO LRFD Bridge Design Specifications 5th

Edition –

2010 that there was enough interface shear transfer capacity between the deck and the ribs that

composite behavior could be relied upon throughout of the structure.

It should be noted that there was a crucial change related the development of composite action

between the editions of the AASHTO LRFD specs used in the 2009 and 2012 analyzes (3rd

and

5th

editions respectively). This key change involved a 240% increase in the expected cohesion

between the concrete of the deck and the shims used to determine the interface shear transfer

capacity. This increase in expected cohesion made it possible to comfortably state that the

observed composite behavior could in fact be relied upon throughout the structure, which was

not the case in the 2009 analysis.

In general, the critical ratings for all of the rating vehicles considered were controlled by shear

in a Span 2 interior rib near the pier at the location where the stirrup spacing changes from 12” to

18”. All of these critical shear ratings were controlled by the edge one lane loaded condition.

The structure failed the LRFR design rating criteria (for the HL-93 design loading) at the

inventory level but essentially passed at the operating level (note: the critical HL-93 operating

level rating for shear was nearly satisfactory at RF=0.96). All of the AASHTO legal loads had

satisfactory ratings with the one exception being the SU7 rating for negative moment of 0.97. It

was found that the structure failed the LRFR rating criteria for the majority of the RIDOT permit

loads with the exception of the single-trip permit loads (RI-OP2 and RI-OP3). The overall

critical rating of 0.63 was controlled by shear under the loading of the blanket permit truck RI-

BP4.

It was expected that the structure would not meet the HL-93 rating criteria since this structure

was built in 1942 and not designed to current LRFD standards. The AASHTO legal load rating

results indicate all trucks that fit within the AASHTO legal load envelope can safely cross the


structure at normal speed. Additionally, the rating results showed that the majority of the RIDOT

permit trucks cannot safely cross the structure at normal speed. Note however that if very slow

crossing speeds are considered, the impact considerations could be reduced or essentially

neglected. If this consideration is employed most of the RIDOT permit vehicles would have

satisfactory ratings. Therefore, these vehicles could possibly be considered to safely cross the

structure as long as they crossed at a very low speed. This decision however would need to be

evaluated further and made by the bridge owner. Although the structure now has satisfactory

ratings for many of the rating vehicles, BDI still recommends that frequent thorough inspections

take place to monitor the escalation of the observed structural degradation.

It is important to note that the aforementioned ratings are applicable to the bridge in its

current condition. This means that the ratings provided by BDI utilized the composite behavior

and stiffness of the ribs as observed in the live-load tests. It is likely that since the ribs have

retained their observed composite action for approximately 70 years, they will continue to retain

it for many years to come. However in the unlikely event that the composite bond between the

beams and the shims (gap fillers or “haunch”) began to diminish, the composite rating factors

would eventually become invalid. To accommodate this situation, non-composite ratings were

generated for HL-93 design loading as a general reference. However, it is very important to state

that the provided non-composite rating factor was provided only as a very general comparison.

This is because if the structural degradation gets to the point where the composite action

diminishes, model assumptions other than the composite behavior would most likely be suspect

as well (e.g., the rotational restraint, the rib and deck stiffness, etc.).

It should be noted that load ratings were calculated for the ribs only, and were not calculated

for the abutment legs or the pier columns. This was due to the fact that the substructure did not

control the previous load ratings, and very little structural degradation was seen at these

locations. This decision was supported by AECOM.


4. REFERENCES & AVAILABLE PLANS

4.1 REFERENCES

American Concrete Institute (ACI). (2008). “ACI 440.2R.-08 Guide for the Design and

Construction of Externally Bonded FRP Systems for Strengthening Concrete Structures",

Washington, D.C.

American Association of State Highway and Transportation Officials (AASHTO), (2011).

"AASHTO LRFD Bridge Design Specifications, 5th Ed.", Washington, D.C.

American Association of State Highway and Transportation Officials AASHTO, (2008). "The

Manual for the Bridge Evaluation, 1st Ed.", Washington, D.C.

Commander, B., (1989). "An Improved Method of Bridge Evaluation: Comparison of Field Test

Results with Computer Analysis." Master Thesis, University of Colorado, Boulder, CO.

Goble, G., Schulz, J., and Commander, B. (1992). “Load Prediction and Structural Response."

Final Report, FHWA DTFH61-88-C-00053, University of Colorado, Boulder, CO.

Schulz, J.L. (1989). “Development of a Digital Strain Measurement System for Highway Bridge

Testing." Master’s Thesis, University of Colorado, Boulder, CO.

Schulz, J.L. (1993). “In Search of Better Load Ratings." Civil Engineering, ASCE 63(9), 62-65.

State of Rhode Island Department of Transportation (RIDOT), (2009). “TAC 0134 Guidelines for

Load and Resistance Factor Rating (LRFR) of Highway Bridges”.


4.2 AVAILABLE PLANS

Figure 4.2-1 Emergency Repair Details – General Notes (Source: AECOM, Inc)


Figure 4.2-2 Emergency Repair Details – General Plan (Source: AECOM, Inc)


Figure 4.2-3 Emergency Repair Details – Repair Location (Source: AECOM, Inc)


Figure 4.2-4 Emergency Repair Details – Repair Details Sheet 1 (Source: AECOM, Inc)


Figure 4.2-7 Original As-Builts – Location Plan (Source: AECOM, Inc)


Figure 4.2-8 Original As-Builts – Elevations (Source: AECOM, Inc)


Figure 4.2-9 Original As-Builts – Construction Plan (Source: AECOM, Inc)


Figure 4.2-10 Original As-Builts – Rib Ribs (Source: AECOM, Inc)


Figure 4.2-11 Original As-Builts – Reinforcement Plan (Source: AECOM, Inc)


A. INSPECTION REPORT

Figure A-1 2007 Inspection Report – Page 1


Figure A-5 2007 Inspection Report – Page5


B. APPENDIX B – PHOTOS

Figure B-1 Bridge 276 – West Elevation – During CFRP Strengthening (Source: 2011

Inspection Report)

Figure B-2 Bridge 276 – West Elevation – During CFRP Strengthening (Source: 2011

Inspection Report)


Figure B-3 Bridge 276 – Bridge Roadway – During CFRP Strengthening (Source: 2011

Inspection Report)

Figure B-4 Bridge 276 – Typical Repairs – During CFRP Strengthening (Source: 2011

Inspection Report)


Figure B-5 Bridge 276 – Example of deterioration near repairs – During CFRP

Strengthening (Source: 2011 Inspection Report)

Figure B-6 Bridge 276 – Example of deterioration including steel section loss – During

CFRP Strengthening(Source: 2011 Inspection Report)


Figure B-7 Bridge 276 – Example of extent of rib spalling – During CFRP Strengthening

(Source: 2011 Inspection Report)

Figure B-8 Bridge 276 – Example of delamination of rib concrete – After CFRP

Strengthening (Source: 2012: Special Inspection Report)


C. APPENDIX C – QUALITY CONTROL/QUALITY ASSURANCE

Several quality checks were performed to ensure the accuracy of the provided load ratings and

supplementary information. For example, a complete review of the previous 2009 ratings

(involving a load test data comparison, bridge model review, capacity calculation review, and

rating assumption review) was performed before the current ratings were run. Additionally, all of

the current load-rating calculations were independently reviewed including a model verification

and worksheet review.

Load rating calculations, described above, were performed and checked by the following

individuals, who vouch for both the accuracy and validity of the provided load rating results for

the Louisquisset Pike Bridge (Rhode Island Bridge #027601) in its current condition. NOTE: The

load rating results presented in this report correspond to the structure at the time of testing.

Therefore, if structural deterioration occurs or the bridge structure changes in any way the results

of this project can no longer be considered valid.

Load Rating Engineer Name: Brice Carpenter Load Rating Checked By: Brett Commander - PE#9396

Load Rating Professional Engineer Signature: ________________________________________

Quality Assurance By: Brett Commander Load Rating Date: 3/23/2011


D. APPENDIX D – COMPUTER INPUT & OUTPUT

The following is a complete list of BDI WinSAC input and output files, along with the

capacity computation excel sheet that are included on a referenced CD. Note that the input files

contain all of the rating model information: geometry (nodal coordinates, element definition and

connectivity), section properties (cross-section properties for every member group), loading path

definition (a series of loadings as the rating vehicle was moved across the model), and rating info

(load factors, member capacities, and envelope combinations). The output files contain force

envelopes for all elements rated and all appropriate actions along with a rating summary for

every member group.

Strength I Input Files

1. RI276_2012_HL93_HS20_c.inp – This BDI WinSAC input file contains all data used in

computing the critical Strength I ratings for the HL93 loading (HS20 truck plus lane load)

assuming composite behavior.

2. RI276_2012_HL93_HS20_nc.inp – This BDI WinSAC input file contains all data used in

computing the critical Strength I ratings for the HL93 loading (HS20 truck plus lane load)

assuming non-composite behavior.

3. RI276_2012_HL93_tandem_c.inp – This BDI WinSAC input file contains all data used

in computing the critical Strength I ratings for the HL93 loading (design tandem plus lane

load) assuming composite behavior.

4. RI276_2012_HL93_HS20_Neg_c.inp – This BDI WinSAC input file contains all data

used in computing the critical Strength I negative moment ratings at the interior support

for the HL93 loading (Double HS20 truck plus lane load) assuming composite behavior.

5. RI276_2012_H20_c.inp – This BDI WinSAC input file contains all data used in

computing the critical Strength I ratings for the H20 legal loading assuming composite

behavior.

6. RI276_2012_Type_3_c.inp – This BDI WinSAC input file contains all data used in

computing the critical Strength I ratings for the Type 3 legal loading assuming composite

behavior.

7. RI276_2012_Type_3S2_c.inp – This BDI WinSAC input file contains all data used in

computing the critical Strength I ratings for the Type 3S2 legal loading assuming

composite behavior.

8. RI276_2012_Type_3-3_c.inp – This BDI WinSAC input file contains all data used in

computing the critical Strength I ratings for the Type 3-3 legal loading assuming

composite behavior.

9. RI276_2012_SU4_c.inp – This BDI WinSAC input file contains all data used in

computing the critical Strength I ratings for the SU4 special hauling loading assuming

composite behavior.



composite behavior.




composite behavior.



composite behavior.

Strength II Input Files

1. RI276_2012_RI_BP1_c.inp – This BDI WinSAC input file contains all data used in

computing the critical Strength II ratings for the RIDOT blanket permit loading RI-BP1











5. RI276_2012_RI_OP1_c.inp – This BDI WinSAC input file contains all data used in

computing the critical Strength II ratings for the RIDOT single-trip permit loading RI-

OP1 assuming composite behavior.







Service I Input Files

1. RI276_2012_RI_BP1_s.inp – This BDI WinSAC input file contains all data used in

computing the critical Service I ratings for the RIDOT blanket permit loading RI-BP1













computing the critical Service I ratings for the RIDOT single-trip permit loading RI-OP1








Strength I Output Files

1. RI276_2012_HL93_HS20_c.rto – This BDI WinSAC output file contains force envelope

and rating data calculated during the Strength I rating of the HL93 loading (HS20 truck

plus lane load) assuming composite behavior.

2. RI276_2012_HL93_HS20_nc.rto – This BDI WinSAC output file contains force

envelope and rating data calculated during the Strength I rating of the HL93 loading

(HS20 truck plus lane load) assuming non-composite behavior.

3. RI276_2012_HL93_tandem_c.rto – This BDI WinSAC output file contains force

envelope and rating data calculated during the Strength I rating of the HL93 loading

(design tandem plus lane load) assuming composite behavior.

4. RI276_2012_HL93_HS20_Neg_c.rto – This BDI WinSAC output file contains force

envelope and rating data calculated during the Strength I rating of the (Double HS20

truck plus lane load) assuming composite behavior.

5. RI276_2012_H20_c.rto – This BDI WinSAC output file contains force envelope and

rating data calculated during the Strength I rating of the H20 legal loading assuming

composite behavior.

6. RI276_2012_Type_3_c.rto – This BDI WinSAC output file contains force envelope and

rating data calculated during the Strength I rating of the Type 3 legal loading assuming

composite behavior.

7. RI276_2012_Type_3S2_c.rto – This BDI WinSAC output file contains force envelope

and rating data calculated during the Strength I rating of the Type 3S2 legal loading


8. RI276_2012_Type_3-3_c.rto – This BDI WinSAC output file contains force envelope

and rating data calculated during the Strength I rating of the Type 3-3 legal loading


9. RI276_2012_SU4_c.rto – This BDI WinSAC output file contains force envelope and

rating data calculated during the Strength I rating of the SU4 special hauling loading












Strength II Output Files

1. RI276_2012_RI_BP1_c.rto – This BDI WinSAC output file contains force envelope and

rating data calculated during the Strength II rating of the RIDOT blanket permit loading

RI-BP1 assuming composite behavior.










5. RI276_2012_RI_OP1_c.rto – This BDI WinSAC output file contains force envelope and

rating data calculated during the Strength II rating of the RIDOT single-trip permit

loading RI-OP1 assuming composite behavior.







Service I Output Files

1. RI276_2012_RI_BP1_s.rto – This BDI WinSAC output file contains force envelope and

rating data calculated during the Service I rating of the RIDOT blanket permit loading













rating data calculated during the Service I rating of the RIDOT single-trip permit loading

RI-OP1 assuming composite behavior.







Capacity Calculation File

1. RI276_XSections_Capacities_2012.xlsx – This Microsoft Excel file contains the cross-

sectional information and resulting capacities for the interior every ~1’ section that used

to calculatBDI WinSAC output file contains force envelope and rating data calculated

during the Service I rating of the RIDOT blanket permit loading RI-BP1 assuming

composite behavior.


E. APPENDIX E – TESTING REFERENCE INFORMATION

E.1. SCANNED FIELD NOTES

Figure E.1-1 Scanned Pre-retrofit Notes- Page 1.


Figure E.1-2 Scanned Pre-retrofit Notes- Page 2.


Figure E.1-3 Scanned Notes- Page 3.


E.2. EQUIPMENT SPECIFICATIONS

SPECIFICATIONS: BDI STRAIN TRANSDUCERS

Effective gage length: 3.0 in (76.2 mm). Extensions available for use on R/C structures. Overall Size: 4.4 in x 1.2 in x 0.5 in (110 mm x 33 mm x 12 mm). Cable Length: 10 ft (3 m) standard, any length available. Material: Aluminum Circuit: Full wheatstone bridge with four active 350 foil gages, 4-wire hookup. Accuracy: ± 2%, individually calibrated to NIST standards. Strain Range: Approximately ±4000 . Force req’d for 1000 : Approximately 9 lbs. (40 N). Sensitivity: Approximately 500 /mV/V, Weight: Approximately 3 oz. (88 g), Environmental: Built-in protective cover, also water resistant. Temperature Range: -60°F to 250°F (-50°C to 120°C ) operation range. Cable: BDI RC-187: 22 gage, two individually-shielded pairs w/drain. Options: Fully waterproofed, Heavy-duty cable, Special quick-lock connector. Attachment Methods: C-clamps or threaded mounting tabs & quick-setting adhesive.


SPECIFICATIONS: BDI WIRELESS STRUCTURAL TESTING SYSTEM

Channels 4 to 128 (Expandable in multiples of 4) Hardware Accuracy ± 0.2% (2% for Strain Transducers) Sample Rates 0,1 – 500 Hz

(Internal over-sampling rate is 19.5-312 kHz) Max Test Lengths 21 minutes at 100 Hz.

128K samples per channel maximum test lengths Gain Levels 1, 2, 4, 6, 16, 32, 64, 128 Digital Filter Fixed by selected sample rate Analog Filter 200 Hz, -3db, 3

rd order Bessel

Max. Input Voltage 10.5 Volts DC Battery Power 9.6 NiMH rechargeable battery

(Programmable low-power sleep mode) Alternative Power 9-48 Volts DC input Excitation Voltages Standard: LVDT/Other:

5 Volts DC 5.5 Volts DC

A/D Resolution 0.3uV bit (24-bit ADC) PC Requirements Windows XP or higher PC Interface Wi-Fi Ethernet 802.11b: 10/100 Mbps Auto Zeroing Sensors automatically zero before each test Enclosures Aluminum splash resistant Sensor Connections All aluminum military grade, circular bayonet “snap” lock Vehicle Tracking BDI AutoClicker, switch closure detection Sensors BDI Intelliducer Strain Transducer

Also supports, LVDT’s, foil strain gages, accelerometers, Load Cell’s and other various DC output sensors Single RS232 serially-interfaced sensor

On-Board PC Processor: RAM:

520 MHz Intel XScale PXA270 64MB

Dimensions Base Station: STS 4-Channel Node:

10” x 6” x 4” 11” x 3.5” x 3.23”


SPECIFICATIONS: BDI AUTOCLICKER

3 Handheld Radios Motorola P1225 2-Channel (or equal) modified for both “Rx” and “Tx”. Power 9V battery

Mounting Universal front fender mounting system Target Retroreflective tape mounted on universal wheel clamp Bands/Power VHF/1 Watt or UHF/2 Watt Frequencies User-specified Data Acquisition System Requirements

TTL/CMOS input (pull-up resistor to 5V)

Output Isolated contact closure (200V 0.5A max switch current)

bridge no 027601 - bditest.com · aashto lrfr approach. review of the load test results indicated...

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