Mike Wenning’s Top 5 Tips for Historic Bridge Restoration

Besides the obvious issue of wastefulness, if American society continues to demolish all of its buildings, bridges, and other structures to make way for brand new ones, what is left? What will remain of our civilization’s history and culture in years to come if everything is no more than 50 or 100 years old?

When it comes to bridges, the following options exist: maintenance, rehabilitation, restoration, or replacement. So why not just tear an old bridge down to make way for a new structure? While it’s true that in some cases it makes more sense to demolish a bridge and start over—because of cost, new safety standards, or increased vehicle usage—valid reasons do exist for retrofitting and restoring historic bridges. Some of these reasons include maintaining cultural history; promoting tourism (as symbols of cities); creating a sense of identity, community belonging, and pride; and, in some cases, cost savings.

We spoke with GAI Consultants’ (GAI) historic bridge restoration authority Mike Wenning, PE, who has rehabilitated more than 425 bridges in his career, many of them historic. Below he shares his top five tips for completing a successful historic bridge restoration project—safely, on time, and on budget.

  1. Treat Permitting and Review Agencies as Partners Instead of Adversaries
    A number of review and permitting agencies, or “Save our Bridge” groups, are heavily involved in historic bridge restoration projects. Examples of these groups include State Historic Preservation Offices and the U.S. Department of the Interior. It’s important to view them as partners in the process, as friends rather than foes, because they bring additional information and perspective to the project that can help create a better end result. And the more they’re included, the smoother the restoration process.
  2. Develop a Solid Understanding of the Environmental and Permitting Requirements
    Historic bridge restoration projects are outside the zone of what many engineers consider a “normal project,” and there are often unfamiliar issues to address. It’s critical to get a handle on environmental and permitting requirements, because unfamiliarity with them can create project roadblocks, such as difficulty obtaining Section 106 permits.

“If we don’t start saving things now, there will be nothing left of our early culture in 500 – 1,000 years. And bridges—wooden, truss, and arch—were definitely part of the early culture in the U.S. They’re the most prominent part of our roadway system. You don’t notice the pavement. But bridges are time capsules of the knowledge, the materials, and the economy of the time.”

Mike Wenning, PE
  1. Obtain a Sufficient Project Budget for Bridge Materials Testing
    With historic bridge restoration projects, one can never have enough information. Different materials—iron, steel, or concrete—have different strengths, often with inconsistent compositions because the individual plants of the era used different recipes. Also, at times, a bridge can be tested and the particular material may have significantly more strength (sometimes double) than what was previously specified. So a decent materials testing budget can provide a lot of important information; it can detect what and how many destructive components exist (such as chlorides), where those properties are located, and it can also show the level of remaining bridge strength.
  2. Go The Extra Step to Locate the Original Bridge Plans and Specifications
    In most cases, a historic bridge is so old that the government agency responsible for maintaining it has moved multiple times and/or lost or misplaced records. But finding the original bridge plans and specifications is invaluable, because it makes the design portion much easier. Otherwise, a restoration team could potentially spend weeks taking field measurements on a historic bridge.
  3. Curate a Library of Historic Bridge Details to Fill in Missing Information
    In the past, many engineers tended to use the same details over and over. So even if the original plans and specs are not found (per tip #4 above), and the exact details of what’s in a particular bridge are not known, developing and referring to a library of historic bridge details can help provide a good guess based on other bridges that that particular engineer designed during that era. “For example,” says Mike, “all Warren truss bridges have the same steel pattern. They might be different sizes, but they’re going to be in a certain order. That’s just how James Warren designed his bridges.” He adds, “One of the things I’ve done is accumulate a lot of partial sets of plans for Daniel Luten, an American bridge builder and engineer. I’ve restored about a dozen of his bridges, and whenever I have a gap in the plans of a particular historic bridge I am working on, I can refer to that library to try to fill in the missing information.”

For more information on GAI’s historic bridge restoration services, contact Director of Transportation Services Mike Wenning, PE at 317.570.6800.


About Mike Wenning, PE

Mike-Wenning-EMPhotoMike is currently serving a three-year term as a Director of the Midwest Bridge Preservation Partnership (MWBPP). Sponsored by the American Association of State Highway and Transportation Officials, in cooperation with the Federal Highway Administration, MWBPP consists of representatives from regional, state, and local highway agencies; provincial transport agencies; and industry suppliers, consultants, and academia. MWBPP’s mission is to develop strategies and actions to prevent or delay bridge deterioration and disseminate that information amongst the different transportation agencies throughout the country.


For related information, check out the following article:

GAI Engineer Authors Book, Tells Visual Story of “City of Bridges” | November 24, 2015

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