Structure of the new movable railway bridge on Pamban island

A new Tower Vertical Lift bridge on Pamban Island (India) replaces the existing “Scherzer” Rolling Bascule bridge within the railway line that connects the island to the Indian subcontinent across the Palk Strait. The lift span of the new bridge consists of a 77.5 m simply supported structure composed of two lateral steel Warren trusses of variable depth and a platform 10.3 m wide, holding two railway lines. The lift movement of the bridge is carried out through two sets of electromechanical systems placed in two towers 40 m high, located at the ends of the lift span, which hold the machinery in their upper part. The choice of this system responds to the criteria of reliability and robustness. Also, the high incidence of marine corrosion in the bridge location has been decisive in the design. The existing bridge is a national icon in South India; therefore, the aesthetic has been a fundamental condition.