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

member repair procedures, but it did lead to abetter understanding of the need for moreknowledge concerning the behavior of historicwrought iron.Material and mechanical testing wascompleted on wrought iron bridge members fromtwo existing bridges in Indiana. This testingincluded: micrographs, chemical analysis,hardness testing, tensile coupon testing, charpyimpact testing, tensile testing of eyebar endconnection, and some limited fatigue testing. Themicrographs that were taken helped to develop abetter understanding of the microstructure of themetal. The chemical analysis completed lead to adetermination of particular elements that arecommonly found in historic wrought iron.Hardness testing, tensile coupon testing, charpyImplementationUpon completion of this research study,recommendations were developed to aid in theinspection and rehabilitation of existing historictruss bridges consisting of wrought iron tensionmembers.1. When inspecting an old, existing bridgeit is important to know the type of materials forthe bridge members. For bridges consisting ofwrought iron members, it is helpful to determinethe year and manufacturer of the bridge. Avisual inspection of the surface of the materialafter it has been thoroughly cleaned can be usedto aid in determining if the material is wroughtiron. Chemical and mechanical testing are alsodesirable, if possible, to determine specificmaterial properties.2. Dynamic loading and previous repairscan cause members to move and the connectionsto develop an unsymmetrical loading. When thisoccurs, forces are not equally distributed throughthe connection, resulting in some members withan unsafe amount of load placed on them whileothers become loose and slack. If it is decided torehabilitate a bridge and the connections areunsymmetrical, it would be beneficial to movethe members and add spacers to the joint to holdthem in place, and thereby ensure that force isequally distributed through each member in thefuture.3. When inspecting a bridge it is importantto check the condition of the pins and determinetheir load capacity. If the pins are severelycorroded, deformed, and/or control the loadimpact testing, and fatigue testing helped todetermine many common material properties.Eyebar end connection testing lead to a betterunderstanding of the load distribution and forcetransfer behavior for one particular bridgemember connection.Testing was also performed on differenttypes of repairs that might be typically utilized inthe field. These repairs included: memberstraightening with heat, straightening withoutheat, welding to join two members, and fillerwelding to restore section loss from corrosion.This testing, along with articles found in theliterature search, helped lead to the developmentof some procedures and suggestions that could beused to repair historic wrought iron bridgemembers.capacity of the bridge, it is recommended thatthey be replaced with a stronger material.4. Upon inspecting an existing historicwrought iron truss bridge, it is not uncommon tofind severe corrosion near the joints of thebridge. The eyebars and diagonals should bechecked thoroughly for section loss fromcorrosion. If severe section loss has occurred theengineer should consider either replacement orrepair of the member. Repair of a corrodedmember could involve one of two procedures.One option is to grind the corroded areas toclean metal and then use a filler weld repairprocedure similar to the one developed in thisresearch project. The second option involvesremoving the corroded section entirely andwelding on a new steel section using a fullpenetration groove weld.5. Slack or elongated members are alsoprevalent in existing wrought iron truss bridges.It is important to shorten these members toensure that load is being distributed evenly to allthe members in the bridge. This should be doneby removing the needed amount of material fromthe center of a wrought iron member and thenjoining the pieces together using either a boltedsplice plate or a full penetration groove weld.Member shortening, however, may not beneeded for members, such as zero-forcemembers, that do not actively participate in theload path of the structure.6. Vehicle collisions often result in thedeformation, and even fracture, of the membersin an existing wrought iron bridge. When25-1 06/04 JTRP-2004/4 INDOT Division of Research West Lafayette, IN 47906