TURNER-FAIRBANK HIGHWAY RESEARCH CENTER NDE Research Ongoing Projects and Response Based Load Rating...

TURNER-FAIRBANK HIGHWAY RESEARCH CENTERTURNER-FAIRBANK HIGHWAY RESEARCH CENTER

NDE Research

Ongoing Projects and Response Based Load Rating

The Office of Research, Development, and Technology (RD&T)Turner-Fairbank Highway Research Center (TFHRC)

McLean, VA

Rebecca Curtis, NDE Research Program [email protected]

NDE Research

Ongoing Projects and Response Based Load Rating

The Office of Research, Development, and Technology (RD&T)Turner-Fairbank Highway Research Center (TFHRC)

McLean, VA

Rebecca Curtis, NDE Research Program [email protected]


NDE ResearchNDE Research

NDE Research Projects• Current and Proposed Projects

Response Based Site-Specific Load Rating• Potential Benefit• Project Overview• Research Plan• Findings to Date


• Gusset Plate Testing Program– Develop inspection procedures for

single- and multi-layer gusset plates– Single-layer plates will be investigated

with Pocket and Phased Array UT– Currently selecting available

technologies for multi-layer gusset plates

– Ongoing Project with completion in late 2012

NDE Research ProjectsNDE Research Projects


NDE Research ProjectsNDE Research ProjectsBarrier Inspection Protocols• Identify typical highway barrier and bridge railing

configurations and critical components subject to deterioration

• Evaluate existing technologies and instruments for accurately detecting and measuring concrete voids and corrosion damage on reinforced concrete highway barriers and bridge railings

• Development of a decision making protocol for visual and advanced reinforced concrete highway barrier and bridge railing inspection

• Project under development


• NDE Web Manual– Comprehensive Collection of NDE

techniques and methods– Provides assistance to State DOT’s in

proper selection and application of NDE technologies for highway systems

– Initial content completed– Web platform development in

progress with completion in early 2012



• BINS Update (BINS II)

– Bridge Inspectors Non-Destructive Evaluation Showcase course currently offered through NHI (fees waived for 1 year)

– Incorporate participant and expert comments to improve class

– Scope of Work for BINS II under development



LRFR Procedures for Response Based Load Rating

LRFR Procedures for Response Based Load Rating

Potential BenefitProject OverviewResearch PlanFindings To DatePotential Questions


LRFR Response Based Load RatingLRFR Response Based Load Rating

Potential Benefit• Based on current rating methods, about 114,000 bridges

nationwide are or should be load-posted• Accurate assessment of a bridge’s true load carrying

capacity is needed so that unnecessary load postings are avoided



Project Overview• Response-based load ratings combine the beneficial

aspects of site-specific characterization of live loads using methods such as WIM technology and a static load test

• This approach can significantly refine some of the biggest uncertainties in bridge load ratings, namely: nature of traffic loads on a particular bridge, and the response of the bridge to the applied loads



Project Overview – Key Issues to Solve• Requirements for collecting strain data under ambient

traffic that will meet LRFR reliability thresholds• Procedures and processes for utilizing the measured

strain data to derive LRFR rating factors that are suitable for inclusion in the AASHTO Manual for Bridge Evaluation



Research Plan – Task 1: Data Collection (In progress)• Develop protocols for strain data collection – identifying

what, how, when, where and for how long data needs to be collected

• Define how the data can be used to produce ratings consistent with LRFR reliability targets

• Identify sensors and data gathering technologies that are commercially available that will collect long term field measurements



Research Plan – Task 2: Lab Investigation• Prepare a detailed work-plan to suit the approved data

collection system• Develop rating equations and algorithms for using

response based data to derive LRFR ratings



Research Plan – Task 3: Field Investigation• Take field measurements with actual bridge traffic• Use Long Term Bridge Performance Pilot Bridges for

validating field data collection protocols• Refine protocols based on validation tests• Compare with analytical ratings



Research Plan – Project Deliverables• Prepare recommended LRFR procedures for response-

based ratings• Prepare AASHTO ballot item for T-18 consideration and

suitable for inclusion in the AASHTO MBE Section 6


LRFR Response Based Load RatingLRFR Response Based Load RatingFindings To Date (highlights)• Three months of data collection is initially proposed,

although this will be evaluated and verified during the project• Strain gages must be placed in location of maximum effect• Two strain gages should be placed in each location to

account for the change in strain through the cross-section• The “base” procedure will assume that there are plans and

the material properties are known• The procedure will provide insight whether the assumed

material properties are accurate• The procedure can be modified to address structures

without plans with additional testing field measurement


LRFR Response Based Load RatingLRFR Response Based Load RatingPotential Questions• How is this proposed method superior to static load tests, using

roadway WIM or developing a finite element model?• The procedure will be less disruptive of traffic than a static

load test.• The rating will be based on the actual loads crossing the

bridge rather than the rough estimates of legal loads and overloads in the LRFR

• The strain data will collect ambient traffic data for the route that contains the structure in question, which may not be available from a stationary WIM station and can be installed with less cost and disruption than a roadway WIM station


LRFR Response Based Load RatingLRFR Response Based Load RatingPotential Questions• How much of an improvement can we expect?

• It is expected that the response based data will reduce the uncertainties in the response side of the equation by half.

• How much will this cost?• The equipment cost will be a one-time purchase, and

commercially available equipment is being investigated• The process will be evaluated to determine how to apply

on a route/network level to maximize the benefit


LRFR Response Based Load RatingLRFR Response Based Load RatingPotential Questions• How often will the response data need to be collected?

• The procedure will be based on a 5 yr time frame similar to the MBE. Effects of longer intervals will be evaluated on test bridges

• Can this method be used to evaluate permits?• The primary goal will be to develop a procedure to

address ambient traffic. A procedure for permit analysis will be developed, although it may require more effort than the “base” process such as calibration of the response with a known vehicle


www.fhwa.dot.gov/research/www.fhwa.dot.gov/research/

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