The Kentucky Transportation Cabinet (KYTC) maintains over two hundred steel bridges constructed with types of steel which are unknown. Kentucky Transportation Center (KTC) researchers have developed a procedure for determining steel tensile properties (0.2% yield strength and ultimate tensile strength) which can be used to help identify unknown steels. The procedure involves extracting small coupons from the lower flanges of steel deck girder bridges. Coupons are then machined into sub-sized tensile testing specimens and suitable shapes for chemical analyses. Sub-sized tensile tests returned values generally comparable to those provided in mill certifications of steels purchased for laboratory trials. Several analytical methods — X-ray fluorescence (XRF) spectroscopy, laser-induced breakdown spectroscopy (LIBS) and arc-spark optical emission spectrometry (OES) — were tested for accuracy against chemical analyses in the mill certifications. All of the methods proved capable of characterizing steel chemistries.

Researchers performed an in-depth review of all obtainable ASTM/AASHO/AASHTO standard structural steel specifications issued from 1900 through 2016. These were incorporated into a spreadsheet along with periodic revisions. Catalogued data include year of specification/revision issuance, material type, thickness, yield and tensile strengths, and steel chemistries (including 15 potential elements). This data set was incorporated into a database management program that can be used by agency officials to devise potential classifications based on ASTM/AASHO/AASHTO standard structural steel specifications.

For validation, coupons were extracted from two bridges with known (carbon) steel types and two bridges with unknown steels. Tensile tests were performed on sub-sized specimens cut from the coupons and 0.2% offset yield and ultimate tensile strengths were determined. Steel chemistries were analyzed using a laboratory XRF unit. The database management system was used to identify the known carbon steels (with slight modification made to the tensile values of one steel). The system also identified the two unknown steels as being high-strength, low-alloy types.

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The contents of this report reflect the views of the authors, who are responsible for the facts and accuracy of the data presented herein. The contents do not necessarily reflect the official views or policies of the University of Kentucky, the Kentucky Transportation Center, the Kentucky Transportation Cabinet, the United States Department of Transportation, or the Federal Highway Administration. This report does not constitute a standard, specification, or regulation. The inclusion of manufacturer names or trade names is for identification purposes and should not be considered an endorsement.