Approach-Span Failure of the Hoan Bridge as a Case Study for Engineering Students and Practicing Engineers

On the morning of December 13, 2000, all three steel girders in a three-girder approach span of the Hoan Bridge in Milwaukee, Wisconsin, fractured. Two of the three girders had a fracture propagate completely through the 3.05-m-deep girders. The bridge was adequately designed and fabricated according to existing code specifications. The failure was caused by the geometric arrangement of the lateral bracing connection into the web of the girders that created a highly constrained condition and prevented yielding of the girder web when overloaded (a situation known as constraint-induced fracture). Other brittle fractures had been observed in steel bridges and ship structures in the United States, which also resulted from this condition. However, the Hoan Bridge attracted more publicity as it was near collapse. The failure of this bridge can serve as a case study for students and professionals. This paper describes the failure and its causes and suggests engineering lessons to be learned. The unique details of the failure offer the opportunity to promote critical thinking and problem solving at levels appropriate to undergraduate students, graduate students, and practitioners, through investigating the cause of failure, emphasizing the lessons learned, and highlighting the resulting change to engineering practice through modifications to code provisions.