B1 - Boston Central Artery

Modern Continental Construction was awarded the $187 million contract for viaducts and ramps, including construction of the I-93 Mainline from the cable-stayed bridge north of the Charles River to the existing I-93 viaduct at existing Bent 33. It also includes construction of ramp structures forming an interchange connecting Route 1, Storrow Drive and I-93 roadways.

The main construction of the viaducts and ramps is comprised of 1,539 precast segmental box girder segments for over 15,200 linear feet of elevated structures. This project is extremely complex with dual level span-by-span construction, multi-level precast post-tensioned straddle bents, balanced-cantilever erection over rail traffic with radii as small as 200 feet, and box girders cast-in-place on falsework.

The project can be divided into two segments; those spans erected span-by-span and those erected in balanced cantilever. The ramps and viaduct that are relatively straight are erected span-by-span. These spans are typically 150 feet long and use a combination of internal and external tendons and are erected with a self-launching overhead gantry supplied by NRS Strukturas of Norway. The 300 foot long gantry weighs 400 tons and was designed specifically for the requirements of this project. Construction of Ramps NS and SN has been completed and opened to traffic.