Center for Transportation Studies, University of Minnesota
Reported evidence suggests that failure of gusset plates initiated the collapse of the I-35W Bridge in Minneapolis,
Minnesota. The particular gusset plates were at a panel point designated as U10. Therefore, a computational study
was conducted on the condition of the U10 gusset plates at the time of bridge collapse. The primary objectives of
this study were: (1) to evaluate previous research and existing design methods for gusset plate connections; (2) to
examine the mechanical condition of the U10 gusset plates at the time of the collapse; (3) to examine possible
scenarios that led to the collapse of the entire bridge; and (4) to identify research needs to improve the design
methods for gusset plate connections. The forces delivered to panel point U10 were reproduced using available
information of the bridge. The truss forces were introduced to detailed nonlinear, three-dimensional finite element
models to calculate stress and strain states of the gusset plates. The results indicate that substantial portions of the
U10 gusset plates were yielded at the time of collapse, confirming earlier findings from federal and state
investigations. Insufficient strength of the gusset plate, along with weight increase due to past deck reconstruction
and construction material and equipment staged on the day of collapse, were identified as the main contributing
factors to the substantial yielding. It is important to note that, even with the weight increase, the gusset plates
would not have yielded substantially if the gusset plates had adequate thickness. The results also suggest that the
interaction of compression and shear played an important role in the gusset plate failure and should be addressed in
gusset plate design. This interaction is not well understood based on available research.
The National Science Foundation and Center for Transportation Studies, University of Minnesota
Liao, Minmao; Okazaki, Taichiro.
A Computational Study of the I-35W Bridge Collapse.
Center for Transportation Studies, University of Minnesota.
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