Many people may have seen the Padma Bridge but may not have realized the challenges behind it. You may wonder what else there is to be challenging. Big bridges are common in many countries. But no, it is not just any river. It is the mighty Padma. Just as one cannot understand the immensity of the Padma River, similarly, one cannot understand the challenges behind the Padma Bridge. That's why you need to know the story behind it.
General overview
The Padma Bridge is a two-story road-rail multipurpose bridge. It is a composite steel truss bridge with two levels that carry a 4-lane highway on the upper deck level for fast-track transportation and a freight single-track railway on the lower deck level. The multipurpose bridge incorporates numerous capacities, such as a gas pipeline, broadcast communications, and a high-voltage control transmission line.
The dream linking bridge, using more than 3.6 billion dollars of resources, is the most challenging infrastructure project the Government of Bangladesh has ever undertaken. The bridge was regarded as an A-category project by the World Bank, ADB, and JICA, the main financial backers.
Geography and Natural Challenges
With 6.15 kilometers (3.8 miles) in extension, the Padma Bridge is the one and only bridge infrastructure linking Bangladesh's southwest and northeastern regions. It spans the Padma with a complex topology. The Padma River is the third-largest river in the world and has the highest amount of sediment transportation.
At the start of the monsoon season, the Padma River becomes fast-flowing and prone to extensive scour. For that, the bridge required deep-pile foundations for stability. The Padma project site resides in a considerable seismic activity zone. Consequently, large seismic forces are exerted on the bridge. This threat and other forces of nature posed a unique challenge.
Design Challenges
China Major Bridge Engineering Co. Ltd. (CMBECL) acquired the construction tender for our dream project. But they couldn’t comprehend the sheer complexity of designing around the huge river depths. So the major design work was handed over to AECOM. AECOM teamed up with SMEC Bangladesh, ACE Consultants, and the Bangladesh Bridge Authority (BBA) to prepare design reports. Dr. Robin Sham, director of global long-span and specialty bridges at AECOM New Zealand, and the Hong Kong team faced many challenges as the lead design consultant for the project. Dr. Jamilur Reza Chowdhury led the 11-member consultant team from the bridge authority.
They devised that in all situations, a two-level structure was chosen because it offers considerable advantages over a single-level one. These comprised separate highway and railway envelopes for greater security, better operation, inspection, maintenance, and emergency evacuation procedures, as well as efficient utility provisions. With the railway on the lower deck, the structural depth beneath the railway is lowered, allowing for shorter railway approach viaducts for tie-in at the north and south banks. A two-level building reduces construction costs while increasing structural efficiency.
Constructor’s Nightmare
Though the Padma Bridge project’s deadline was expected to end in four years, the contractor, CMBECL, could not finish work before the deadline. They finished it in 8 years. For many reasons, this delay happened, notably:
1. The river bed is about forty meters below the water of the Padma River. Forty meters is about 131 feet. Ten feet is usually one story high. As such, the height of the piers from the water surface to the bridge span can be compared to that of a 13-story building.
Then the bridge's piers (generally speaking, the columns, which are called piers in civil engineering language) should be a 13-story building.
Now just imagine 42 pillars on top of a riverbed. Each has six piles beneath it. Steel spans were placed on each of the pillars, totaling 41 spans.
2. River training was another key problem contractors faced in implementing this project. Almost USD 1 billion was spent on river training works on the Janjira and Mawa banks to prevent the river course from drifting.
The riverbed changes a lot due to water flows. The riverbed may scour up to 62 meters or 200 feet. Therefore, the foundation was built in such a way that it can sustain the load even if the riverbed scours down to 62 meters.
Success
After overcoming so many obstacles and challenges, the construction ended on June 23, 2022. The bridge stands tall, signifying national pride.
Impact
The coordinate course through the Padma Bridge gives a portal for rural and agricultural businesses in the southwest to the Dhaka-Chattogram financial hallway. The bridge will increase the region’s yearly net residential income (GDP) by 2.5 percent and the nation’s general GDP by more than 1.3 percent.
Now you know what it took to design and implement the impossible. The Padma Bridge holds strong in the foundation of all workers’s hopes.
Writer
Sadi Reza,
Keywords: challenge, river, riverbed, Padma, project, railway, piers, feet, spans, deck.
Category: Feature.
References:
1. Rahman, M. T. U., & Kabir, S. B. (2022). The Padma Multipurpose Bridge: construction challenges and sustainable management. ResearchGate. https://doi.org/10.47981/j.mijst.10(02)2022.389(09-21
2. Rahman, M. T. U., & Kabir, S. B. (2022). The Padma Multipurpose Bridge: construction challenges and sustainable management. ResearchGate. https://doi.org/10.47981/j.mijst.10(02)2022.389(09-21
3. AECOM. (2022, August 15). Padma Bridge | AECOM. https://aecom.com/projects/padma-bridge/
4. Islam, Md. (n.d.). General and design features of the Padma Multipurpose Bridge. In https://iabse-bd.org. IABSE-JSCE Joint Conference on Advances in Bridge Engineering-II, Dhaka, Bangladesh. https://iabse-bd.org/old/94.pdf
5. Roundtables. (2017, April 15). Padma Bridge Age: A New Lifeline of Development. The Daily Star.
6. Bridge, D. S. P. O. P. (2022). “From an engineering point of view, Padma Bridge is one of the most challenging projects in the world.” The Daily Star. https://www.thedailystar.net/supplements/the-daily-star-plus-padma-bridge/news/engineering-point-view-padma-bridge-one-the-most-challenging-projects-the-world-3055796
7. Fice, R. S. P. C. (n.d.). Structure magazine | Padma Bridge. https://www.structuremag.org/?p=524
