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

1235.5 Evaluation and Repair of Corrosion DamageThe slag in wrought iron helps the metal to be very resistant to corrosion. Whilein open air, the material will develop a patina that turns into a pitted surface but typicallydoes not progress inward to create section loss (Griggs 1999). However, the materialdoes corrode when it is frequently covered in soil or water, which is a commonoccurrence at the connection joints in a historic truss bridge.Since the connection joints in historic wrought iron bridges typically collectheavy moisture and debris, eyebars and diagonal members that frame into theseconnections typically experience heavy corrosion. In some cases, half of the originalthickness of the end of an eyebar is lost due to heavy corrosion, as can be seen in Figure5.9. If heavy corrosion is present in an existing bridge the corroded area should becleaned and repaired, or the member should be replaced.Also eyebars can develop severe corrosion at the eye connection from thecollection of water. This corrosion reduces the cross section of the eyebar connectionand lowers the load capacity. If considerable section loss is found at an eyebar endconnection it is beneficial to either replace or repair the eyebar. One method that couldbe used to repair this severe corrosion is filling in the corroded area with filler weldmaterial.This corrosion repair was evaluated experimentally in this study. Two differentcorrosion patterns were modeled. The first pattern modeled was section loss fromcorrosion on the edge of eye connection similar to the repair seen in Figure 5.10. For thiscorrosion repair, material was removed from the eyebar connection (Eyebar A) in thesame pattern as the corrosion to half the thickness of the eyebar, as seen in Figure 3.25.Then a filler weld was utilized to fill the removed area. A detailed description of thewelding process used is described in Appendix D.