Rehabilitation of a Concrete Tied Arch Bridge

The John Mack Bridge, constructed in 1929, crosses the Big Arkansas River in Wichita, Kansas. The bridge is generally in good condition except for the arch hangers, which exhibited extensive cracking of the concrete encasement. The cracks are all in the vertical direction and originate mostly at the top or bottom of the hangers and progressed the length of the members. The cracks vary from very fine, less than 1 mm, to cracks 3 mm wide. It is the condition of the hangers which caused concern for the structural capacity of the bridge, resulting in a call for designs to rehabilitate the structure. In order to further analyze this complex structure, a diagnostic load test was performed using a pre-weighted test vehicle at various positions on the bridge. Measurements of strains induced in both the concrete and steel were made.