Photo courtesy of the NPS Inspectors used rappelling techniques to assess repairs for the 555-ft-tall obelisk. The magnitude-5.8 earthquake that rattled most of the eastern U.S. on Aug. 25 created new cracks and spalling in the upper sections of the 555-ft, 5-in.-tall Washington Monument in the nation's capital. While the extent of quake-related damage was not a surprise, the size of several spalls was larger than expected, says a forensic engineer who conducted an inspection for the U.S. National Park Service.The survey team of Wiss, Janney, Elstner Associates Inc., Northbrook, Ill., extracted any spalls that represented a potential fall hazard
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.