Metrorrey's linea 2 extension viaduct: A revolution for light-rail precast concrete segmental bridges

Metro of Monterrey's new 6.6-km-long (4.1 mi) linea 2 extension viaduct in Monterrey, Mexico, completed in September 2008, includes a revolutionary concept for precast concrete segmental light-rail bridges developed by Juan Jose Goni Baamonde. The 37-m-long (121 ft), 9.2-m-wide (30 ft) typical spans have a U-shaped cross section that allows the two rail tracks to be placed within the structure envelope, which reduces noise, danger of derailment, and visual impact. In addition, the typical segment contains only 45 kg of structural reinforcement per cubic meter of concrete (76 lb/yd(3)) concrete with 10M (no. 3) bars, whereas most current light-rail segmental bridges typically contain concrete with a density of about 120 kg/m(3) (200 lb/yd(3)). This was accomplished with a unique use of transverse and longitudinal internal tendons. The concept offers a viable and more economical alternative to the typical box-girder cross sections for light-rail bridged.