Investigation of Material Properties for Load Rating of Historical Bridges

Abstract

More than 6,500 material test observations of historical reinforcing steel bars, structural steel, and concrete were compiled from the Texas Department of Transportation (TxDOT) database. Statistical distributions were fitted to represent the strengths of concrete and different grades of steel from given eras. Strength values to be used in load ratings of historical bridges were determined based on the 5th-percentile strengths from these distributions. For bridges built prior to 1954, the data support a yield strength increase of up to 40% for reinforcing steel bars based on this approach. The compressive strength used for load ratings of bridges built prior to 1959 could be increased by up to 20% compared with the current guideline. Specific recommended values are applicable to load ratings of Texas bridges, whereas the statistical framework is applicable generally.