Evaluation of Retrofit Procedures for Nail-Laminated and Stringer Bridges

Project summary:

The cost of retrofitting rural bridges is often significantly less than the cost of replacement. Restricted funding for rural infrastructure makes these procedures very attractive. However, if retrofit procedures are to be a viable option, a number of questions must be resolved. These questions include: What is the condition of the substructure of the bridge and will the pilings, stringers and deck survive another 30 to 40 years of service? How much improvement in load distribution will be observed after retrofit? Will the composite action between the retrofit deck and the old deck continue after a number of years of service? The research in this project will address these issues by evaluating two bridges in Sibley County. Bridge No. L2642 is a nail-laminated bridge and was retrofitted with a transverse deck during the summer of 1992. The deck and grout have gone through three winters and should be load-tested again to determine if the bridge has maintained the same load distribution performance. Bridge No. 6641 is a stringer bridge which must be made wider and stiffer as part of the upgrading that is being done to Sibley County Road #8. A transverse deck will be placed over the existing transverse deck. The bridge will also be widened. The bridge will be load-tested before and after retrofit and the improvements load distribution will be determined.