Historic wrought iron and steel bridges are being replaced at an alarming rate. Those that remain are often rehabilitated using inappropriate techniques or are downgraded for limited highway traffic or pedestrian use. Lansing Community College in Lansing, Mich., is using a PTT Grant to develop and provide training based on modern and historic technologies to address the national need for preservation expertise in preserving historic metal truss structures.
While there are currently efforts to preserve bridges constructed between 1850 and 1950, most misguidedly assume the historic technology that created them is no longer available, leading to the use of inappropriate techniques. This lack of knowledge has led to the rapid destruction and replacement of historic wrought structures.
The college’s project, guided by the Secretary of the Interior’s Standards for Rehabilitation, plans to solve this problem by combining three different training components. One of these is the development of a three-day workshop designed to inform attendees about effective preservation techniques for restoring historic metals. The workshop will also demonstrate successful manufacturing processes, which include using original construction techniques and applying modern steel fabrication techniques to historic preservation.
These processes and techniques include electric arc and oxygen fuel welding, flame straightening, removal of rivets using carbon arc gouging or a “rivet buster,” the historic hot riveting process, and a specialized procedure for removing pack rust. All of these methods have been effective in recent restoration projects in Michigan, Indiana and Ohio.
The college also plans to produce two educational videos and training courses dealing with restoration of historic metals and hot riveting to disseminate these techniques to a wide audience.
According to J. Patrick Harshbarger, senior historian for the TranSystems Lichtenstein Corporation, there is a strong need for this type of training.
“The workshop fills a national preservation need to better understand and be sensitive to historic metal-truss bridge fabrication technologies, with both training on the history of iron metallurgy and truss technology, along with hands-on practical training in using the relatively lost art of riveting, along with careful application of welding technology, to make non-destructive and compatible repairs that limit the loss of a truss bridge’s historic fabric,” he said.
Harshbarger said the curriculum–targeted toward preservationists, contractors, state-level transportation officials and engineers–will give a better understanding of how to properly restore and preserve historic bridges.
Principal Investigator Vernon Mesler will also lead a project team with expertise in historic metals preservation, welding, curriculum development, and professional training for industry. Mesler will have access to an experienced faculty of welding instructors, machinists, and support staff to assist with the preliminary research and preparation for the workshop demonstrations, conference planning, video production, and development of training courses.
The project began in March 2009 and will be completed the three-day workshop in March 2010.