Upon the opening of phase 2 of the Chennai metro rail, an array of 63 steel bridges will facilitate the passage of driverless trains, strategically placed over various structures such as buildings and flyovers. These steel girders, each spanning significant lengths, are a solution where vertical clearance poses limitations for conventional concrete viaducts supported by pillars.
Recently, a 40-meter-long steel girder was installed, weighing 222 tonnes, above Chennai’s bypass flyovers on Mount-Poonamallee High Road. This installation is part of the Porur to Poonamallee Bypass phase-2 construction, set for public access between 2025 and 2028.
The spokesperson for CMRL, L Girirajan, emphasized the advantage of steel girders requiring less depth compared to their concrete counterparts, aiding in situations where vertical clearance is restricted. Stressing the safety equivalence of both steel and concrete girders, Girirajan highlighted their adaptability to varying constraints.
Moreover, the installation of longer steel spans not only circumvents costly environmental studies but also minimizes the need for numerous piers, thus positively impacting the visual aesthetics of these crossings.
Highlighting the efficiency of steel girder installations, officials noted the faster setup but acknowledged the necessity of conducting these installations during night hours to manage potential traffic diversions. The recent installation in Porur was strategically executed during low-traffic periods, ensuring minimal disruption to commuters.
The installation of these steel bridges demands heavy lifting machinery like 500-metric-ton cranes and constant vigilance throughout the construction process.