ABSTRACT
The designer, the planner, and the systems operator must always keep in mind that things could go wrong. Just as the “price of liberty is eternal vigilance,” the price of resilience is a restless mind. Even when everything appears to have been taken into consideration, the hidden flaw may still arise. When LeMessurrier designed the Citicorp tower in Manhattan, 59 stories high, he believed that he had thought of everything, including a “mass damper” on the top to keep the building from swaying too much. But a call from a student got him thinking about the structure, and he began checking his assumptions. One assumption was that the welded structure would resist a quartering wind. He discovered that the contractor, however, had used rivets instead of welds. The building was at risk. The student’s question led to extensive repairs. But now the building was safe, wasn’t it?
