Willis (formerly Sears) Tower. Photo © Hedrich Blessing
When Chicago was still celebrating the end of the Civil War, the city had a population of roughly 200,000 people. The most memorable structure from that era, the Water Tower, was still three years from construction. Today, 150 years later, the city’s population has grown by more than 1,200 percent, and the city’s tallest building, the Willis Tower, is more than 1,300 feet taller than the height of Chicago’s tallest building in 1866.
This is all to say a lot can change in 150 years. Which makes our question, from engineer Bill Muscat, pretty challenging: What do we do in 150 years when our current buildings are too old? What do we do with an old Willis Tower?