Tools for Determining Yield Stress of In-Service Gusset Plates

There is no recognized nondestructive testing method currently available to establish the yield stress of plate materials in the field. Typically, the minimum yield stress of steel is obtained using tensile coupons tested in accordance with ASTM E8. However, to collect samples for testing is destructive and most bridge owners are reluctant to remove samples from in-service guest plates. To overcome this limitation, a practical device that can estimate the yield stress of bridge steel plates was developed in this research program. The prototype device is fabricated from titanium which has very high strength and relatively low weight to facilitate field portability. The hand-held device uses a manually actuated hydraulic cylinder to apply an out-of-plane load to the free edge of a steel plate. The applied load, measured with a load cell, creates bending deflection of the plate that is measured with a displacement sensor. The applied load and plate displacement measurements are collected with a portable data acquisition system. Both the prototype device and data collection system are self-contained and require no external power source. This portability allows a bridge inspector to collect and analyze data in the field. The acquired load and deformation data are used to estimate the yield stress as the deflections become nonlinear at the onset of plate yielding. The load and deformation responses are calibrated to finite element analyses and empirical reference tests. Based on statistical analysis of results with the prototype device over a range of plate materials and thicknesses, a yield stress reduction factor of 0.85 was developed to ensure that the predicted yield stress would not exceed the actual yield stress with 1/10,000 probability when three replicate tests are performed. The device is capable of testing mild steel plates up to 1 in. thick. After testing, there are imperceptible residual displacements on the plate at the defined yielding threshold. These characteristics provide a nondestructive method to estimate the yield stress of bridge steel plates in the field which was previously not possible and as such is a technological breakthrough.

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  • Supplemental Notes:
    • This NCHRP-IDEA investigation was conducted by Oregon State University, Corvallis. Distribution, posting, or copying of this PDF is strictly prohibited without written permission of the Transportation Research Board of the National Academy of Sciences. Unless otherwise indicated, all materials in this PDF are copyrighted by the National Academy of Sciences. Copyright © National Academy of Sciences. All rights reserved
  • Authors:
    • Higgins, Christopher
    • Pflaum, Therese M
  • Publication Date: 2014-6


  • English

Media Info

  • Media Type: Digital/other
  • Edition: Final Report
  • Features: Figures; Photos; References; Tables;
  • Pagination: 35p
  • Serial:
  • Publication flags:

    Open Access (libre)

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Filing Info

  • Accession Number: 01535235
  • Record Type: Publication
  • Report/Paper Numbers: Highway IDEA Project 161
  • Files: TRIS, TRB, ATRI
  • Created Date: Aug 27 2014 9:38AM