Evaluation and Repair of Wrought Iron and - Purdue e-Pubs ...

138rectangular in shape. These eyebars had been visually damaged in the collapse of thebridge. The specimens from the Adams Mill Covered bridge were machined from rounddiagonal tension members that had been replaced with steel diagonals in the bridge.From the micrographs taken of the historic wrought iron, it was determined thatthe microstructure consists mainly of ferrite particles along with numerous deposits ofimpurities. A majority of these impurities are categorized as slag, or iron oxide that isdispersed in elongated deposits throughout the metal leading to a fibrous structure in themetal.A chemical analysis of the wrought iron revealed a carbon content lower thanmost mild carbon steels. However, the wrought iron had relatively high excess quantitiesof silicon, phosphorous and sulfur. The excess amount of silicon found in the chemicalanalysis is what comprises the slag that is dispersed throughout the metal. The excesssilicon and could be an important indicator to determine if the metal is historic wroughtiron.The Rockwell B hardness test was performed on wrought iron samples from theBell Ford Bridge. The average of all the resulting hardness values was 70 with a standarddeviation of 6.5. It was difficult to determine a correct correlating tensile strength fromthis hardness value due to the lack of previous hardness testing data performed onwrought iron relating hardness to tensile strength. If the metal was a nonaustenitic steel,the correlating tensile strength would be 61 ksi, which is higher than the tensile strengthdetermined for the wrought iron. Therefore, the hardness of the wrought iron may be lessthan a typical structural steel.The tensile strength, yield strength, modulus of elasticity, and percent elongationfor wrought iron were determined from tensile coupon testing that was completed duringthis study. These values were determined for each tensile testing coupon test andaveraged together. The average tensile strength, yield strength, modulus of elasticity and