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

38The Bell Ford Bridge consisted of timber compression members and wrought irontension members. The wrought iron tension members were the same size and shape aseach other and made of the same material found in many wrought iron truss bridges. Itwas believed that testing these tension members would provide a reasonable estimate ofthe material properties of the wrought iron used in other historic wrought iron bridges.The wrought iron tension members donated to this research project consisted offive bottom tension bars, also known as eyebars. Figure 3.2 is a photograph of eyebars,arbitrarily labeled one, two and three. These eyebars had been severely damaged in thecollapse of the bridge. Two of them had been heat straightened in some areas while thethird had only been heat straightened on the far end and was still disfigured. Figure 3.3 isa photograph which includes eyebars four and five. These eyebars had not encounteredas much visible damage as eyebars one, two and three.Other material that was tested in this study came from the Adams Mill CoveredBridge in Carroll County, Indiana. This bridge was built in 1873 by the WheelockBridge Company. Similarly to the Bell Ford Bridge, it is also a covered bridge thatutilizes wrought iron members in tension. The pieces utilized for testing from this bridge,however, consisted of round tension rods that were the diagonal members of the AdamsMill Covered bridge. These tension rods were replaced with steel tension rods and thewrought iron was then stored. This stored wrought iron was donated for research. Figure3.4 shows the round wrought iron tension rods from the bridge.3.2 MicrostructureThe specimens used to determine the microstructure of wrought iron weremachined from two of the eyebars of the Bell Ford Bridge. Eyebar one and two wereheat straightened and had some visible damage. From each eyebar, a piece about oneinch square was cut from an area that had not been heat treated or visibly damaged. The