Dive Brief:

• Opening of a new eastern span of the Bay Bridge between Oakland and San Francisco shifts attention to taking down the 77-year-old steel-truss bridge that it replaced.
• A state bridge engineer calls the intricately balanced steelwork "the world's largest armed bow and arrow."
• Missteps in the demolition process could send steel members and rivets flying into San Francisco Bay and into the new bridge adjacent to the old one, and could injure or kill workers.

Dive Insight:

Taking down the old bridge is being done by combining information from the bridge's design with computer programs to analyze how it can be undone without precipitating a virtual explosion of unbalanced members. A factor that adds to the complexity is that engineers are unsure how the steel made in the early 20th century will respond to changes in the loads on it as parts are removed.