As the Federal Railroad Administration pursues regulations regarding inspection of concrete railroad ties, the Massachusetts Bay Transportation Authority last month launched a $91-million project to replace 147,000 concrete ties that began failing in just 10 years. Photo: Courtesy VHB Thousands of precast concrete ties began to fail in just 10 years. In 1997, the MBTA chose concrete over timber ties because Rocla Concrete Tie Inc., a Denver-based precast-concrete manufacturer, claimed they had a 50-year life span compared to 30 years for timber ties. But in 2007, several thousand ties began cracking and crumbling, disrupting train service on the 61-mile Old
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.