BRIDGE SESSIONS. Innovative Bridge Applications AND Physical Testing for Bridge Load Rating. ICEA Midyear Meeting July 10, 2003

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ICEA Midyear Meeting July 10, 2003

BRIDGE SESSIONS

BRIDGE SESSIONS

Innovative Bridge Applications

Innovative Bridge Applications

AND

AND

Physical Testing for Bridge Load

Physical Testing for Bridge Load

Rating

Rating

ICEA Midyear Meeting

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Session Speakers

Session Speakers

Session Speakers

z Justin Doornink, Ph.D. Student

z Travis Konda, Ph.D. Student

z Van Robbins, M.S. Student

z J. S. Ingersoll, WHKS & Co.

z Terry Wipf, ISU

z F. Wayne Klaiber, ISU

z Brent Phares, CTRE

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ICEA Midyear Meeting July 10, 2003

Evaluation and Use of an

Evaluation and Use of an

Integrated Bridge Load

Integrated Bridge Load

Testing/Rating System

Testing/Rating System

Brent M. Phares, Terry J. Wipf, F. W. Klaiber and D. L. Wood

Bridge Engineering Center Iowa State University

Scott Neubauer

Office of Bridges and Structures Iowa Department of Transportation

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The Problem

The Problem

The Problem

z Posted bridges and bridges with

unknown strength and behavior

z Limited financial resources

z Code equations that are usually very

conservative at predicting bridge behavior

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The Problem

The Problem

The Problem

z Unknown bridge conditions

– Load distribution

– End restraint

– Edge stiffening

– Composite action

– Effectiveness of specific bridge details

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The Solution

The Solution

The Solution

z Use physical testing to understand the

specific characteristics of each bridge

z Use field collected data to calibrate a

computer constructed model of the bridge

z Use the accurate, calibrated computer

model to determine bridge response to rating vehicles and other loads

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An Integrated Testing System

An Integrated Testing System

An Integrated Testing System

z Hardware and software suite

z Integrated and seamless through all

steps – Field testing – Data presentationModel generationModel calibration – Rating

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Data Collection Hardware

Data Collection Hardware

Data Collection Hardware

z Hardwired strain gages with variable

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Data Collection Hardware

Data Collection Hardware

Data Collection Hardware

z Strain gage junction box

– Balance and control strain gages

Collect and

temporarily store data

– Communicate with PC

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Data Collection Hardware

Data Collection Hardware

Data Collection Hardware

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Data Collection Hardware

Data Collection Hardware

Data Collection Hardware

z Power unit and PC

– Power and control entire system

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Software Suite

Software Suite

Software Suite

z WinGRF

– Relates truck position with strain data

Prepare visual summaries of data

» Strain

» Neutral axis location » Curvature

Allows engineer to study the data for behavioral

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Software Suite

Software Suite

Software Suite

z

WinGEN

Construct bridge model

» Overall geometry

» Material characteristics » Section properties

» Support conditions

Define loading conditions

– Establish optimization parameters

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Software Suite

Software Suite

Software Suite

z WinSAC

– Performs analysis

Performs optimization calculations

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Hardwired strain gages Wireless truck position indicator Engineering based data interpretation Structural modeling Model analysis and optimization with field collected data Accurate Assessment

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Diagnostic Testing of a Bridge

Diagnostic Testing of a Bridge

Diagnostic Testing of a Bridge

z Boone County

Bridge #11 on L Road

z 38 ft - 10 in. single

span

z Eight girders with

timber deck

z Damaged exterior

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Instrumentation

Instrumentation

Instrumentation

z 40 Intelliducers at 20 locations used z Focused on: – Composite action – End restraint – Load distribution z Instrumented:

– Six of eight girders

L4 L8 L10 L9 L3 L2 L1 L7 L6 L5 L14 L18 L20 L19 L13 L12 L11 L17 L16 L15 Abutment BearingL South

C

Abutment BearingCL North

2'-6" 2'-6" 19'-5" Section - Instrumented 9'-5.5" 9'-11.5" Y1 8'-10.6"

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Load Position

Load Position

Load Position

z Three different load paths defined - loaded

truck tandem axle dump truck

z Each path addressing a key attribute

Abutment BearingCL South Abutment BearingCL North

Y2 Y3 Girders N 11'-11" 2'-6.375" 2'-6.375" 2'-6.375" 2'-6.375" 2'-6.375" 2'-6.375" 2'-6.375" 38'-10" 15'-8"

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Test Results-Minimal End

Restraint

Test Results

Test Results

-

-

Minimal End

Minimal End

Restraint

Restraint

-250 -200 -150 -100 -50 0 50 100 150 200 250 0 10 20 30 40 50 60 70 Truck Position, ft Microstrain

Bo tto m Flang e, Lo catio n L4 To p Flang e, Lo catio n L4 Bo tto m Flang e, Lo catio n L8 To p Flang e, Lo catio n L8

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Test Results-Transverse

Symmetry

Test Results

Test Results

-

-

Transverse

Transverse

Symmetry

Symmetry

-250 -200 -150 -100 -50 0 50 100 150 200 250 0 10 20 30 40 50 60 70 Truck Position, ft Microstrain

To p Flang e, Path Y1, Lo catio n L10 Bo tto m Flang e, Path Y1, Lo catio n L10 Bo tto m Flang e, Path Y3 , Lo catio n L5 To p Flang e, Path Y3 , Lo catio n L5

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Modeling

Modeling

Modeling

z Model created using WinGen

z Based on plan geometry and field

measurements

z 3 total element groups

Steel girder stiffness (Iy) – Timber deck stiffness (E)

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Modeling Results

Modeling Results

Modeling Results

z All elements groups optimized

– Girders found to have higher stiffness than code predicted

– Deck found to have less stiffness than code predicted

– Approximately 8% fixity

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Typical Modeling Results

Typical Modeling Results

Typical Modeling Results

-250 -200 -150 -100 -50 0 50 100 150 200 250 0 10 20 30 40 50 60 70 Truck Position, ft Microstrain

Bo tto m Flang e Analytical To p Flang e Analytical Bo tto m Flang e Exp erimental To p Flang e Exp erimental

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Typical Modeling Results

Typical Modeling Results

Typical Modeling Results

-250 -200 -150 -100 -50 0 50 100 150 200 250 0 10 20 30 40 50 60 70 Truck Position, ft Microstrain To p Flang e Analytical Bo tto m Flang e Analytical To p Flang e Exp erimental Bo tto m Flang e Exp erimental

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Rating

Rating

Rating

z Traditional AASHTO LFD Calculations z HS-20 Load Vehicle z Shear limit: – 3.94 Inventory – 4.22 Operating z Flexural limit: – 0.92 Inventory – 1.52 Operating

z Physical Test Based

Calculations z HS-20 Load Vehicle z Shear limit: – 4.78 Inventory – 7.61 Operating z Flexural limit: – 1.31 Inventory – 1.54 Operating

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Results of testing

Results of testing

Results of testing

z Impact of damaged member verified

z Increased rating

– 42.4.% for flexure

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Conclusions

Conclusions

Conclusions

z System is well suited to rating “typical”

highway bridges – Materials » Steel » Concrete » Timber(?) – Type: » Simple span » Continuous span » Truss

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Acknowledgements

Acknowledgements

Acknowledgements

z Sponsor: Iowa Department of

Transportation, Highway Division and the Iowa Highway Research Board

z Sponsor: USDA FPL and FHWA

z DOT Office of Bridges and Structures

z Buchanan and Winnebago Counties

z Delaware County

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Acknowledgements

Acknowledgements

Acknowledgements

z Tama County z Cedar County z Butler County z Blackhawk County

z ISU Research Laboratory Manager

z ISU graduate and undergraduate

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Load Testing At the Iowa D.O.T.

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Reason’s for Load Testing Bridges

Reason’s for Load Testing Bridges

 To Evaluate the Need for Posting

ÂTo Create a Model of a Bridge for determining

Heavyload Capacity

ÂTo Determine the Effectiveness of a

Strengthening System

ÂTo Determine the Need for a Strengthening

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Oversized Loads

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Scott Neubauer, P.E. Bridge Rating Engineer

Office of Bridges and Structures Iowa D.O.T.

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