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Research and Development (R&D) Project Sites

Project Information
Project ID:   FHWA-PROJ-11-0039
Project Name:   Radiographic Inspection of Gusset-Plate Connections
Project Status:   Completed
Start Date:  May 9, 2011
End Date:  November 1, 2012
Contact Information
Last Name:  Ocel
First Name:  Justin
Telephone:  202-493-3080
E-mail:  justin.ocel@dot.gov
Office:   Office of Infrastructure Research and Development
Team:   Bridge and Foundation Engineering Team [HRDI-40]
Program:   Innovative Bridge Research and Deployment
Laboratory:   Structures Laboratory
Project detail
Roadmap/Focus area(s):   Infrastructure Research and Technology Strategic Plan and Roadmap
Project Description:   The project needs to evaluate existing radiographic inspection technologies and post-processing for inspection of gusset-plated truss connections. The project would have to evaluate and recommend techniques needed to produce effective images through multiple gusset plates, and then demonstrate the ability to determine where different density changes (i.e., corrosion loss) exist. This would include recommendations for radiation intensity, required number of images, required standoff distances, etc.  Finally, the technique should be deployable without the need to shut down traffic for radiation concerns if at all possible. This project will run in parallel with the National Cooperative Highway Research Program project (NCHRP 12-84) research and use two of those research specimens on which to test the technique.
Goals:   To determine the efficacy of using radiographic testing (RT) for the inspection of multilayered gusset-plated connections to find corrosion hidden from typical visual inspections.
Background Information:   The National Transportation Safety Board (NTSB) outlined five safety issues as part of the I-35W bridge (Minneapolis, MN) collapse investigation. One of the safety issues was the apparent inadequate use of technologies to assess the condition of gusset plates on truss bridges. This applies in particular to the inability for inspectors to quantify section loss on the interior surfaces of gusset plates of congested connections. The National Transportation Safety Board (NTSB) recommended ultrasonic nondestructive evaluation to determine section loss. However, ultrasonic inspection can only reliably determine thickness through one steel plate, though gusset plate connections often utilize multiple layers of thinner steel plates to define the total gusset plate. Radiographic inspection has the ability to perform density measurements through multiple steel plates, and in terms of gusset plate inspection, may be far superior to ultrasonic techniques. Radiographic inspection is not a new technology, but new developments in digital film and computer post-processing of digital images make the technology easier and faster to use effectively. In addition, the inherent shielding of the steel connection itself reduces the standoff distances to where traffic shutdowns would not be necessary.
Product Type:   Techbrief
Test Methodology:   Full-scale experimental.
Expected Benefits:   Reduced inspection time and more reliable assessment of remaining section in multilayered gusset plates.
Deliverables: Name: Final report.
Product Type(s): Techbrief
Description: This report will be written by the contracted agency and will include a description of their radiographic testing inspection method, results attained, and interpretations of the data collected.
Publication URL(s):
FHWA Topics:   Roads and Bridges--Asset Management
TRT Terms:   Radiography
Gusset Plates
Steel Bridges
FHWA Disciplines:   Structures
Subject Areas:   Bridges and other structures
Maintenance and Preservation


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