OPERA project: Increasing the capacity of slab-span timber bridges
The Exchange regularly highlights projects completed under the LRRB’s Local Operational Research Assistance Program (Local OPERA). A condensed sample from the 2006 OPERA annual report is reprinted below. For a copy or the report, please visit www.mnltap.umn.edu/opera.
Local OPERA helps to develop innovations in the construction and maintenance operations of local government transportation organizations. Learn more about the program and apply for OPERA funding online at www.mnltap.umn.edu/opera, or contact Jim Grothaus, Minnesota LTAP director, 612-626-1077, mnltap@umn.edu.
Problem: Owners of the approximately 1,300 treated timber bridges in Minnesota are looking for inexpensive and easy ways to increase the load capacity and serviceability of existing timber bridges to accommodate both the increased number and size of vehicles now depending on local road systems.
Solution: Apply University of Minnesota research analyzing the relationship between load distribution and the transverse stiffness of longitudinal slab-span timber deck systems.
Procedure: On bridge 86511 (CSAH 12 over Buffalo Creek in Marysville Township), existing mid-span spreader beams were relocated to the quarter-points of the respective spans, and then larger spreader beams were installed at the center point of the spans, as well as a spreader beam at the other quarter-point of each span. The bridge was resurfaced and crack control joints were sawed at each support.
Results: Increasing the number and size of spreader beams increased bridge capacity and performance, resulting in an inventory rating increase.
Approximate Cost: $24,400 ($10,000 approved for project)
Implementation: No plans to use currently, but will consider use of technology as bridges need improvement.
Project leader: Wayne Fingalson, P.E., Wright County Department of Highways.