Structural engineers inspecting Christchurch’s six steel structures designed with eccentric bracing to resist seismic loads found that five performed well in the shallow Canterbury earthquake that devastated the city on Feb. 22. But the engineers are curious about why two eccentric-braced bays of a three-story parking garage did not fare well—one fractured and the other deformed. The garage did not collapse, thanks to redundancy in the overall structure. “This is the first time the level of excitation of an earthquake was at least as large as or has exceeded the design basis in an area where steel, eccentrically braced frames
Arch dams, classically curved monoliths situated in narrow valleys, are not as common as other types of dams, such as embankment dams and gravity dams. ENR takes a look at some of the biggest arch dams in the world, both completed and under construction.