Estimating the Impacts of Preservative Ports on Bridge Tie Strength

Abstract Scale models of wooden bridge timbers were broken in bending to assess the impact of holes drilled along their length to permit the addition of wood preservatives. The results indicate that the holes have minimal impact. However, the common practice of cutting “daps” on the underside of the beams to accommodate the supporting beams appears to have substantial strength-reducing effects. Railroads could consider using borate ports to improve the life of their bridge timbers and reducing the depth of, or eliminating, daps.