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Abstract: This article discusses issues of structural design revealed by the collapse of I35W Bridge on August 1st, 2007. The article is based on analysis of the original bridge design drawings, a series of detailed finite elements computations, and material evidence disclosed by National Safety Transportation Safety Board (NTSB) official investigation. These issues include (i) redundancy considerations for multi-span bridge; (ii) reason for under-designed bridge elements; (iii) effects of lateral force on gusset plates' load capacity in a steel-truss structure; (iv) criterion of gusset plate's stability and thin-plate theory-based model for load-rating. This analysis concludes that the lessons learned from the I35W Bridge collapse may have certain significance for the safety assessments of similar steel bridges. According to recent surveys, there are scores of this kind of aged bridges that are still in service [38, 41].