ABSTRACT
ABSTRACT: On December 13, 2000, two of the three girders of the northbound Hoan Bridge carrying I-794 in the City of Milwaukee developed full depth brittle fractures, leaving the span near collapse. The bridge was immediately closed to all traffic. On December 28, 2000 the most critically damaged section of the northbound roadway was removed by explosive demolition. A forensic investigation was performed jointly between FHWA’s Office of Infrastructure R&D, Lehigh University and Lichtenstein Consulting Engineers (Lichtenstein) for the Wisconsin Department of Transportation. The forensic investigation concluded that the sudden brittle fracture originated in the lower shelf plate joint assembly and traveled the length of a vertical 3.05 m (10 ft) steel “I” girders in a single cycle. The joint assembly at this point was highly constrained. The Hoan Bridge brittle fracture was the first of its kind ever observed in the United States and is likely to have an impact on bridges with similar details nationwide. Following an emergency inspection and retrofit, the southbound roadway was re-opened to limited two-way traffic in February 2001. A fasttrack $7.8 million contract designed by Lichtenstein for the permanent retrofit of all three-girder spans and the replacement of the demolished northbound span was completed in October 2001. This paper will present an overview of the bridge failure, the forensic investigation findings and present the design of the emergency and permanent retrofits of the Hoan Bridge.
