The Council on Tall Buildings and Urban Habitat has decided to measure a building’s height from the level of the “lowest, significant, open-air, pedestrian entrance,” to accommodate multi-use skyscrapers with several main entrances at different levels. The group also has decided to eliminate its height-to-roof category—acknowledging that fewer tall buildings have easily measurable, distinct roof elevations. Under the new criteria, the 800-meter-plus Burj Dubai, currently set to open as the world’s tallest building in January, will now be measured from the lowest of its three main entrances. Also, under the new criteria, the recently completed Trump International Hotel & Towers
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.