One of the greatest challenges to long-span bridge engineering is the forces of nature. Recent catastrophic events around the world reinforce the fact that nature can be destructive to infrastructure. At the Padma Bridge site in Bangladesh, AECOM used state-of-the-art technology and innovative disaster prevention and mitigation solutions to tackle some severe challenges.
Padma Bridge – a 6.15km long, combined rail-road river crossing.
At 6.15 kilometers (3.8 miles) in length, the Padma Bridge is a landmark structure and one of the longest river crossings in the world. The Padma River is the third largest river in the world, and has the largest volume of sediment transport.
During monsoon seasons, the Padma River becomes fast flowing and is susceptible to deep scour, requiring deep-pile foundations for bridge stability. The Padma Bridge site is also in an area of considerable seismic activity, resulting in significant earthquake forces being exerted on the bridge. This combination, together with other forces of nature, posed a unique challenge.
The multipurpose Padma Bridge detailed design project has been successfully completed. AECOM developed alternative concrete deck forms, including an extradosed concrete truss bridge, a concrete girder bridge and a steel truss bridge. In all cases, a two-level structure was chosen, having significant advantages over a single level structure. These included segregated highway and railway envelopes to offer enhanced safety, improved operation, inspection, maintenance, and emergency evacuation procedures, as well as efficient provisions for utilities. With the railway in the lower deck, the structural depth beneath the railway is reduced, allowing the lengths of the railway approach viaducts for tie-in at the north and south banks to be minimized. With a two-level structure the construction cost is reduced, making the structure more efficient.