TURNER-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 Manager

TURNER-FAIRBANK HIGHWAY RESEARCH CENTER NDE Research NDE Research Projects Current and Proposed Projects Response Based Site-Specific Load Rating Potential Benefit Project Overview Research Plan Findings to Date

TURNER-FAIRBANK HIGHWAY RESEARCH CENTER 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 Projects

TURNER-FAIRBANK HIGHWAY RESEARCH CENTER NDE Research Projects Barrier 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

TURNER-FAIRBANK HIGHWAY RESEARCH CENTER 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 NDE Research Projects

TURNER-FAIRBANK HIGHWAY RESEARCH CENTER 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 NDE Research Projects

TURNER-FAIRBANK HIGHWAY RESEARCH CENTER LRFR Procedures for Response Based Load Rating Potential Benefit Project Overview Research Plan Findings To Date Potential Questions

TURNER-FAIRBANK HIGHWAY RESEARCH CENTER LRFR 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

TURNER-FAIRBANK HIGHWAY RESEARCH CENTER LRFR Response Based Load Rating 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

TURNER-FAIRBANK HIGHWAY RESEARCH CENTER LRFR Response Based Load Rating 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

TURNER-FAIRBANK HIGHWAY RESEARCH CENTER LRFR Response Based Load Rating 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

TURNER-FAIRBANK HIGHWAY RESEARCH CENTER LRFR Response Based Load Rating 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

TURNER-FAIRBANK HIGHWAY RESEARCH CENTER LRFR Response Based Load Rating 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

TURNER-FAIRBANK HIGHWAY RESEARCH CENTER LRFR Response Based Load Rating 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

TURNER-FAIRBANK HIGHWAY RESEARCH CENTER LRFR Response Based Load Rating Findings 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

TURNER-FAIRBANK HIGHWAY RESEARCH CENTER LRFR Response Based Load Rating Potential 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

TURNER-FAIRBANK HIGHWAY RESEARCH CENTER LRFR Response Based Load Rating Potential 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

TURNER-FAIRBANK HIGHWAY RESEARCH CENTER LRFR Response Based Load Rating Potential 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

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