A National Perspective on Evaluating Strategies for Historic Truss Bridge Projects between Rehabilitation and Removal/Mitigation

Focus Area

Historic Preservation/Cultural Resources


Community & Cultural Concerns




Under $99k


Under 1 year

Research Idea Scope

Description: It is generally recognized that not all historic truss bridges can be rehabilitated in place or relocated because of structural condition, financial costs, or public interest in preservation in-place. Alternatives to the standard rehabilitation/mitigation methods have yet to be investigated in a meaningful way or to synthesize alternative approaches used in the past by state Departments of Transportation. The rehabilitation of historic bridges has been the subject of many publications and extensive discussions since at least the 1970s. Traditionally, the publications and discussions have focused on best practices in rehabilitating the historic structure of the bridge or on relocation/adoption. These discussions have arisen as mitigation measures for proposed undertakings under Section 106 (36 CFR 800) of the National Historic Preservation Act and Section 4(f) of the US Department of Transportation Act of 1966. Strategies for rehabilitation generally consist of engineering approaches to preservation of trusses in place by widening, supplementing or augmenting the structural components and/or substructure of truss bridges or removal (and sometimes relocation) of the structure. The dialog primarily deals with engineering methods rehabilitation as mitigation. There is, however, a gray area between the generally followed methodology of preservation/adaptive reuse (rehabilitation) and removal (demolition of relocation) of historic truss bridges that has yet to be thoroughly investigated and considered. This involves non-traditional practices that could incorporate historic bridge components in a visual or non-structural fashion that preserves the appearance of a truss bridge if not the actual function of the structure. While portions of the historic structure may be preserved as part of non-historic structures, consideration needs to be given to aesthetics and the false impression the structure might give observers. Ultimately, the debate should be whether this method truly mitigates impacts to an historic truss bridge. Objective: The goal of this research is to investigate alternate approaches in developing plans to utilize components of historic truss bridges as an alternative to preservation for mitigation purposes. These methods could then, in practice, be considered by state DOT’s in their negotiations with State Historic Preservation Offices as options to rehabilitation as potential mitigation during the Section 106 process when rehabilitation is not a structurally or financially feasible option. Related Research: Much has been written about the rehabilitation of historic truss bridges since 1980. Six documents were reviewed for this research proposal in regards to addressing the research needs question: is this method a viable alternative to rehabilitation or removal/mitigation for historic truss bridges. Are there any case studies in the states where this approach was utilized and what the results of that process include. The available literature is, for the most part, case studies for specific truss bridge rehabilitation projects, while a few address the subject on more general terms. All involve rehabilitation as mitigation, not the utilization of parts of the historic structures in a non-historic manner. Chamberlin, William P., 1999. Historic Highway Bridge Preservation Practices: A Synthesis of Highway Practice. NCHRP Synthesis No. 275. Transportation Research Board. National Academy Press. DeMond, Gregory F., 1996. Aesthetic Guidelines for Older Bridges. Transportation Research Record 1549. HNTB Architects, Engineers, Planners. p. 42-47. McKeel, Walter T., Miller, Ann B., Clark, Katherine S., 2007. Best Practices for Rehabilitation and Moving of Historic Metal Truss Bridges. Journal of the Transportation Research Board, No. 1991. Transportation Research Board of the National Academies, p. 71-77. Taavoni, Shahin, 1994. Upgrading and Recycling of Pin-Connected Truss Bridge by Pin Replacement. Transportation Research Record 1465, Kennedy, Porter & Associates, Consulting Engineers, p. 16-21. Zuk, William, Newlon, Howard H., McKeel, Wallace T., 1980. Methods of Modifying Historic Bridges for Contemporary Use. Virginia Highway & Transportation Research Council, VHTRC 80-R48. Zuk, W., McKeel, W.T. Adaptive Use of Historic Metal Truss Bridges., 1981. Transportation Research Board, National Research Council, National Academy of Sciences. Tasks: Research objectives include the following tasks •Create a multi-disciplinary team with expertise in historic bridge rehabilitation projects to investigate the question of whether utilizing components of historic truss bridges rather than rehabilitation constitutes a feasible method of mitigation. •Conduct a more detailed review of the literature regarding the rehabilitation/mitigation of historic truss bridges in regards to preservation and reutilization of structural components to determine the feasibility of incorporating and displaying parts of historic bridges rather than the entire structure. •Identify what bridge components could be used in this method and how that potential type of mitigation may function as mitigation. •Create a database documenting the data derived from this study, including examples of where this type of mitigation was used. Implementation: Rehabilitation has been the standard mitigation for historic truss bridges for many years. However, rehabilitation is not always cost effective or structurally feasible. Other methods could conceivably be used to create a bridge that, at least at first glance, appears to be historic, but only incorporates elements of the bridge. These elements would function in a visual capacity and not be functioning structural components of the replacement bridge or may be used on a new structure that is not even located at the historic site. Is this a viable method or is it just a bad idea? Findings derived from this study would determine when and if this is a worthwhile mitigation option or something that should not be considered in the Section 106 process.

Urgency and Payoff

State DOTs are often encouraged by preservation organizations, stakeholder groups, and state historic preservation offices to consider non-traditional means of mitigating or preserving historic truss bridges – not just the dichotomy of rehabilitation vs. removal. This research will provide a valuable perspective that state DOTs can use in Section 106 consultation and in dealing with stakeholders.

Suggested By

Jon Axline Montana Department of Transportation

[email protected]