How to Demolish a Bridge
SMRTR summary
Blowing up a bridge sounds simple. It is anything but. When Iowa and Illinois replaced the aging Interstate 74 bridges spanning the Mississippi River between Moline and Bettendorf, the real engineering challenge wasn't building the stunning new arch bridges. It was taking the old ones down safely.
The original spans, built in the 1930s and 1950s, were crumbling. Transportation Secretary Ray LaHood once called one "one of the worst bridges I've seen in America." But demolishing them meant protecting endangered mussels, keeping a busy shipping channel open, and managing the hidden stresses locked inside aging steel.
Engineers had to model the bridges' entire construction history, sometimes consulting old magazine articles, just to understand where forces were hiding. Crews removed the deck in careful, symmetrical stages. They even built new structural elements mid-demolition to keep workers safe.
The explosive finale, severing suspension cables and towers with precisely placed shaped charges, was almost anticlimactic compared to everything that came before. Almost.
SMRTR provides this summary for quick context. The original article belongs to Practical Engineering.
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