Capacity Evaluation of a Severely Distressed and Deteriorated 50-Year-Old Box-Beam

Safety of adjacent box-beam bridges with distressed and deteriorated beams became a greater concern after the failure of a fascia beam of this bridge type in Pennsylvania, in 2005. As a proactive measure, eight box-beam bridges built in the 1950’s were inspected. Earlier routine inspection reports documented longitudinal cracking at the soffit of a fascia beam of Hawkins Road Bridge. Built in 1957 the bridge carries Hawkins Road over the I-94 freeway in Jackson County, Michigan. In 2006, following a repair decision for replacing the fascia, the beam with the distress was salvaged and the capacity was evaluated through load testing. Remaining prestress calculations showed 77% of the initial prestress that is 3% less than the final prestress used for the design according to the bridge specifications. Concrete modulus of elasticity was evaluated as 5,200ksi and the nominal compressive strength as 8,300 psi. Analysis of load test data indicated that a bridge with such a beam is safe to operate if the transverse connectivity is sufficient for load distribution as envisioned in the design. A major challenge however, is assessing the effectiveness of the load distribution through the transverse connectivity. Further, the importance of identifying concealed corrosion, and quantifying material properties and load distribution is highlighted.