MnDOT LRRB Development of Cost-Effective Timber Bridge Repair Techniques for Minnesota

Research Project


MnDOT LRRB Development of Cost-Effective Timber Bridge Repair Techniques for Minnesota


Principal investigators: Brent Phares, 515-294-5879, (project list), Iowa State University

Project status


Start date: 02/01/13
End date: 11/30/15


Report: November 2015, Development of Cost-Effective Timber Bridge Repair Techniques for Minnesota NA (*pdf)

Related publications:

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Sponsor(s): Minnesota Department of Transportation

About the research


The primary objective of this work is to provide formal guidance to county engineers throughout Minnesota for repairing timber bridge components. The benefit of having such a resource will be measured by improving the overall condition of the transportation system and reducing system failures through implementation by local officials.

As is often the case, funds required to complete repairs are limited and, as a result, any method used must not only be structurally feasible but also economically feasible. This report provides bridge owners and caretakers several routine maintenance and repair options aimed to meet the goals of simplicity and affordability.

The economic impact of repairing timber bridges was assessed for multiple scenarios: a comparison was made between the net present value of repair at varying repair costs over time and the net present value of varying reconstruction costs over time. Through this exercise, for each scenario, a point in time was identified when repair or reconstruction makes most economic sense.

An additional assessment of overall costs (direct plus indirect) was completed, which included the increased user costs due to bridge posting or closure. This assessment made clear that when indirect costs are included, the benefits of maintaining or repairing a bridge to prevent posting or closure become great.

A standalone manual, Cost-Effective Timber Bridge Repairs: Manual for Repairs of Timber Bridges in Minnesota, was also developed for this project.

2711 S. Loop Drive, Suite 4700, Ames, Iowa 50010-8664
Phone: 515-294-9501 ~ Fax: 515-294-0467
The Bridge Engineering Center is administered by Iowa State University's Institute for Transportation.

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