DMRC Phase 3 Line 7 - Special Spans near Welcome Station

As part of Phase III of the Delhi Mass Rapid Transit System (MRTS), the Delhi Metro Rail Corporation (DMRC) constructed Line No. 7, the Mukundpur — Yamuna Vihar Corridor. This corridor, spanning over 55 km, covers a significant area of Delhi along the Ring Road, connecting various operational Delhi Metro lines. A section of the alignment, between Karkardooma and Gokulpuri, featured an elevated viaduct, including six elevated stations.

Due to time constraints, the contractor opted to build a two-span composite steel bridge near Welcome Station. This option was more expensive than a concrete bridge, which would have taken longer to construct. The contractor engaged us to create an optimized design for a concrete bridge, to demonstrate the cost difference with the steel bridge and support a claim for additional costs from the owner.

We proposed a three-span balanced cantilever concrete bridge, with a span arrangement of 40m - 85m - 63m, to accommodate the existing railway lines below. The box girder was cast-in-place using a form traveler. The depth of the single-cell box girder was variable, with 6m at the main piers and 2.9m at the mid-span and ends. Due to strict railway clearance requirements, we leveled the soffit of the main span within the clearance envelope and transitioned to the support using a linear profile. The primary piers were supported by nine 1.2m diameter bored piles, while the expansion piers used four bored piles. Despite the accelerated 3-month schedule, including the preparation of the bill of quantities (BOQ), we successfully optimized the design. This highlighted potential savings when compared to the steel alternative, resulting in a successful claim by the contractor for $500,000.