In seismic zones, construction of concrete high-rises keeps getting easier, thanks to advances in high-strength reinforcing steel used for confinement of high-strength concrete. The first use of 100-ksi rebar, in a just-opening 31-story tower in Seattle, is getting pretty high marks from the structural engineer and rebar fabricator. And the first use of a more price-competitive 90-ksi rebar in a project in nearby Bellevue, Wash., is getting even higher marks. Slide Show Photo: Cary Kopczynski & Co Avalon Towers benefited from the lower cost of the material, which was produced using standard methods. The advantage of using the material on
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.