About Padma Bridge
Padma Bridge is a great architect in Bangladesh History. The engineering of Padma Bridge is conducted by the China Major Bridge Engineering Co. Ltd. The construction starts on 26 November 2014, and the construction ends at 23 June 2022. The bridge was inaugurated on 25 June 2022 by the Prime Minister of Bangladesh Sheikh Hasina.
The length of the main bridge is 6.15 kilometres. The bridge is 10,642 kilometres long, with 41 spans connected to 42 supports, and is the 122nd longest bridge in the world. The length of the railway viaduct is 0.5321 kilometres. It is the longest bridge in Bangladesh and will drastically cut the distance and travel time between Dhaka and the Mongla port. After the Amazon River in Brazil, the Padma is the second biggest river with a high current (roughness) in the world. It will play a significant role in regional and global trade. The distance between each pillar of the bridge is 150 metres, with the deepest piling in the world at 128 metres. 2015 saw the beginning of work on the 6.15-kilometer-long bridge, which will be finished in December 2021. The Padma multifunctional bridge connects 19 districts of the southwestern area of Bangladesh, which is home to 30 million people, to Dhaka and other sections of the nation. The construction of the Bridge at a cost of Taka 30,193.6 crore ($3.6 billion) was totally financed by the Government of Bangladesh. According to the Bangladesh Ministry of External Affairs (MoFA), the bridge is not part of China’s Belt and Road Initiative, and no bilateral or multilateral foreign finance has been used to finish this multifunctional project.
There are very few people in Bangladesh, who have not seen Padma face to face. When you see Padma, what do you see? Its width?? width of course. Because the depth, the magnitude of the stream is not so easily understood.
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About The Engineering of Padma Bridge: The Column
Do you know how deep the river is? The bottom of the river is about 40 meters below the water. meter but not fit 40 meters is about 131 feet. 10 feet is usually one storey high. As such, the height of the water surface from the bottom of the Padma river is equal to a 13-story building.
Then the bridge columns (which are actually called piers in civil parlance) should be equal to 13 story building. But if the column is not attached to the ground, the stream of Padma, the column will be washed away. What do you think, the 13-story long column will not float? go bro This is Padma. So the column should be embedded in the ground. How much will you build? The soil below Padma is of sand type, soft mud type. Not as hard as a rock. The bedrock is thought to be about 8km below. 8 km is the height of Mount Everest! So don’t even dream of going to bedrock. In many countries, bedrock is found very little down. Building any structure in their country is much less expensive because their foundations are very easy to build and cost less.
About The Engineering of Padma Bridge: The Pile and Scour
However, how much should be paid for the Padma river bridge pile?
When there is excess flow during the monsoons, the sand-like soil beneath the Padma is washed away. This is called scour. The highest recorded scour of Padma river is 65 m (approx) (or 61 m). It means that 65 meters of soil has been washed away from the bottom of the river. Means 213 feet. It means that the soil of the same height as a 21-storey building has been washed away. (I don’t believe myself, how did so much soil wash away!) No other river has the record of washing away about 21 floors of soil or transporting such a large amount of sediment (particles of soil) of the Padma. In this situation, to get the ground under the water, you have to go down 13+21=34 floors!
Then the columns you have to provide for the bridge must be more than 40+65=105 meters long! Means a 34-story building longer than the column!
Now, the scour is more in some parts of the river, less in some places. You are not sure, how much scour your column of Padma bridge will be exposed (exposed), will not be embedded in the ground, as a result your long column will be washed away!
An average of 120 meters of piles have been provided for this purpose. 120 meters means almost a 40-story building! Piles, as tall as this 40-story building, have been installed. (When I first heard the word 120 meters, I thought I heard it wrong, it must be 120 feet. Later, after hearing it many times, I understood that it is not 120 feet, but meters!)
It went to the depth of the pile! Now let’s see how the size of the pile is, how is the sap. The piles are round. Round 40-story building as long as the cylinder! The diameter of this cylinder is 3 m. I mean almost from the floor to the ceiling of your room! It is diameter!
The piles are made of steel sheets. Quite thick (I don’t remember the thickness, 70/60 mm or more less/more) these sheets are rolled into cylinders. This cylinder will be attached at a geometric rate. Means with one meter long cylinder, one meter long and one part. Now with this two meter long cylinder, another two meter long cylinder. In this way, a pile is made by pairing a pile with a length equal to 20 floors and a pile equal to 20 tala!
Who do you think picked up these huge tall piles? Who put them? Superman? Special hammers are brought from Germany for these piles. I heard that a hammer was made for the Padma Bridge. Special crane, special hammer! The Elahi case is going on in Mawa-Jazira.
These piles are hollow. After planting in the ground, they will be filled with sand. The piles can rust, although the erosion will be 10 millimeters in 100 years. 50/60mm will still be there. (It is tested, how much corrosion will occur if rusted) Design life of Padma bridge is 100 years. It means that in 100 years the thickness of the pile will not be reduced except in sha Allah. These piles are actually called caissons. In pure civil engineering terms
So much for the story of a pile! Do you think the columns of our saintly Padma Bridge, which we call piers, will stand on this one pile? What if the soil under this pile moves? If the pile breaks! For this there will be 6 piles under each column. As a spider has 8 legs in 8 directions, the piles of this pier (column) will spread in 6 directions.
Piles shall be placed vertically but not in the ground. To be inserted in a curved, inclined manner. will be inclined in the ratio 1H:6V. So 120 meters long pile, bent and inserted, the feet of 6 of them will be far, far away in 6 directions. The soil of these 6 directions #InshaAllah will not be washed together (scour). Since they will be inclined, their load carrying capacity will also increase a little. It’s a bit like how journalists who report during cyclones are seen with both feet on either side, far apart. If standing upright, there is danger of overturning in the wind. This is done because the lateral load that comes (wind load) is easier to stand if you stand with two feet together, if you put two feet on both sides it is easier to stand, the load can be resisted more. This is also an engineering plan. So, these 6 piles will also take more lateral load just for being inclined. (Lateral load means that coming from the side, like the shock of the current).
Again, only because of the inclination, the 120m long pile will go 118.3m underground. Because when a stick is bent, its height decreases even though its length remains the same. For example, if the ladder is attached to a vertical wall, the higher the head of the ladder is, if the ladder is tilted, the head of the ladder will fall further. Same is the case with Pyle.
A program named PIGLET was used while designing these piles. The optimum / most efficient pile is found with this program. This study is done on three types of pile foundations. These three types of foundations are:
1. 6 raking steel tubular piles
2. 8 raking steel tubular piles
3. 12 cast in situ vertical concrete piles
It can be seen from the study, the foundation of 6 inclined steel piles is the most efficient. (raking means inclined)
These 6 piles will have a pile cap. You will see this thing floating in the water. But it is not floating at all! It usually stands on 6 legs (piles). This pile cap is so big, a family of 3/4 can live in this space! A very rough estimate says there is more than 900 square feet! That means a pile cap larger than 900 square feet. This pile cap is entirely of concrete. I have no idea about the thickness/height.
The piles below the two piers will be slightly different. Vertical bored concrete pile is supposed to be. Which will go as deep as 80 meters. This means that these piles will not be inclined, but will go straight under the water. These will be concrete piles, like the normal columns of our houses. The funnest part is, these piles will be cast into the water! Means will pour concrete in the water! But the concrete column will not float! Brother, there is this technology! In case of this pile, 12 piles will be placed under a pier.
Pier or bridge columns will stand on this pile cap. This pier is entirely made of concrete. reinforced concrete. The entire bridge will have 41 piers. However, there may be a change in pile design/number due to not finding solid soil without mud in the river bed at Mawa end. The number of peers may increase to 42/43. I heard such strange talk in many news reports. That which will be most effective, which will cost the least, will be implemented in practice.
About The Engineering of Padma Bridge: The Span
The span will sit at the head of this pier. The length of each span is 150 meters. Means, say from Bata Signal to Kantabon Mor, two span length.
For this span design, analytical models (on computer, with analysis software) of 3 types of spans are made and checked, which one will provide the highest safety at the lowest cost. There were three spans: 120 m, 150 m and 180 m. Among them 150m span was the most efficient so actually 150m span was installed.
These spans are Warren type still truss girder and concrete on upper deck. All the spans together are 6,150 meters. That is, the entire length of the bridge is 6.15 km. Meaning the entire Padma Bridge is: Science Lab Bus Stand to Kalyanpur Bus Stand or Shahabagh to Mohakhali Flyover. (approximately)
Padma Bridge is a double span bridge. The train will pass through the still truss. Rail line is dual gauge. Means broad gauge and meter gauge, both types of trains can cross Padma Bridge. The railway line of our country’s western side (Rangpur Rajshahi, Kushtia Khulna side) is broad gauge. And the rest of the railway lines across the country are meter gauge. One type of rail cannot run on another rail line. But with dual gauge these two types of rail can run. So any railway in Bangladesh can run through Padma Bridge. There will be an emergency access point so that if there is any problem in the train, people can be taken off the train and taken to a safe place.
Again, this is no ordinary railway line. Provision has been made for two containers to be transported in it. Railways in Bangladesh usually take one container. But it is being done here so that in future trains can go with one container on top of another i.e. double-decker container. The load-carrying capacity of the main bridge had to be increased to accommodate these double-decker containers. That load will actually be taken first by rail line, rail to truss, truss to pier (column), pier to pile. This required the pile to be made stronger, and as a very natural result, the cost increased.
A concrete deck will sit on top of this two-story bridge. means the roof. The car will run over it. The lightest material possible to construct the deck will be used. Deck, means the road over the bridge will be 22 meters or 72 feet wide. Cars will run in four lanes here.
Seismic isolation bearing is used before installation of E span. Without it, the energy that an earthquake would have hit the structure with would be greatly reduced. The technology used here is Base Isolation, in which the foundation will move during an earthquake but the bridge above will not move. There will be a system of movement. This is called a pendulum bearing. It is being used. Can slide with it. Will be back again. It is used in many places in the world. However, it has never been used in such a large project. Due to this technology the number of piles, size of pile cap is reduced to some extent.
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About The Engineering of Padma Bridge: The Utilities
Some utilities will also cross the river through the bridge! There will be a gas transmission line. Optical fiber and telephone lines will go. And of course the electric line will go.
This is just the bridge. Only Padma Bridge. But much more remains in the project like river management works, approach road works. Now let’s look at them.
It is not enough to build a bridge. Bridges have to be connected to existing roads on which vehicles are plying. This connecting road is the approach road. This approach road to Padma Bridge is twice the length of the bridge itself. 12 km. The construction of this approach road was done by a company of the country, Abdul Monem Limited. The work on this approach road included the connection with the National Highway from Jazira. Similarly, the road that was close to Mawa was brought to the international level. And service area. Which is the main office of this huge construction site. Offices and residences will be built here during and after construction. Among them, five bridges are required on the connecting road at the Jazira end. The length of these bridges alone adds up to about a kilometer.
This work was also difficult from the engineering point of view. Jazira road was once a grazing area. soft soil Roads over such soft ground are problematic, as the road will buckle in places and as a result the pitched road above will break. Then any road again has to be kept well above the flood level. That is, from the flood records, the highest level of water can be found. Then it will be seen, at a certain time (perhaps in the next 100 years), the maximum amount of water can rise in flood. Then the road will be built in such a way that there is a road above the highest water level.
For this reason, a high place like a dam has been made by dumping soil. Then an attempt has been made to increase the density of the soil under the road. The machine had to be brought from Germany for this work. The name is sand compaction pile. It is not technically difficult. Enters like a pipe inside the soft soil. A machine is pressed from above inside the pipe. The bottom of the pipe is closed. In this process, the soil moves downward. And when the pipe is lifted again, sand is thrown from it. Thus the density of the soil is increased. It is hoped that when a vehicle moves, the road will not be blocked. Many tests have been done. The car is running, no problem. The work of this approach road is almost complete now.
Two huge construction yards have been built for the Padma Bridge at Mawa and Jajira, at either end. I have no doubt that it would take all day to walk around the entire construction yard. For this huge construction yard and approach road, a huge amount of land had to be acquired. 13,000 houses where about 74,000 people lived, were damaged for the project. Seven resettlement areas have been allocated for these people on both sides of the river. Their houses, mosques, schools, markets have all been built there.
Many trees around Padma river have been cut down for this construction yard, approach road, resettlement area and service area. Forestry has also been done for this. As of December 2015, 70,452 trees had been planted. This was the responsibility of the forest department.
About The Engineering of Padma Bridge: The River Management
Another very important function of Padma Bridge is river management. Let’s see first, what is river governance and why is it necessary.
The river broke and formed. The river changes its course. Now the bridge remained at Mawa Jazira, the river may have changed its course and gone somewhere else. Then Padma Bridge will become like the broken bridge of Jamalpur. (In Jamalpur, there is a bridge called Bangga Brij, where the river has broken the edge of the river and moved away, but the bridge remains in its original place.) So that there is an edge on both sides of the Padma Bridge, and that there is an approach road on that edge; That is why the work of river management is being done so that vehicles can get down from the bridge.
River management refers to the structural work done to protect the course and banks of the river. Means to protect the edge when bricks or stones or anything like that is used, to protect the edge. By analyzing the flood time data of different years, it is found that 1 lakh 40 thousand cubic meters of water can go to the sea through Padma every second for the next 100 years. (It means that if we could stop the water flow of Padma, its water for 20 seconds, then one crore six million people of Greater Dhaka city would have drinking water for one day.) This much water goes to the sea through Padma, it is the second highest in the world. First Amazon. Padma is number two. This water should be taken from under the bridge. Arrangements should be made so that the water can flow under the bridge to the Bay of Bengal. If this water is somehow trapped, it will simultaneously flood upstream (west-north side of the river) and at the same time this water will put a lot of pressure or push on the bridge. It would be very natural for the bridge to fail as a result.
These are the challenges of river governance. There are very few contractors in the world who can do this.
When tenders were called for the Padma Bridge river management works, only 3 companies submitted tenders.
1. Hyundai Engineering and Construction Ltd of South Korea
2. Jan De Nul N.V. of Belgium
3. Sinohydro Corporation Ltd of China
Sinohydro got this tender in July 2014.
River dredging is going on in this work. Dredging is the removal of silt from the bottom. So that there is less obstruction in the flow of water. So that more amount (higher volume of water) can go. It is expected that the pressure of water on the edge will be reduced a little. 10 million cubic meters will be dredged at Mawa end. And 40 million cubic meters will be dredged at the Jazira end.
More than 100 feet dredging has to be done in this river. under water It has already been calculated how the river bank will be under water. According to that, the soil on the banks of the river should be cut. Special dredger has to be used for that. Which is GPS controlled, the underwater soil can be calculated and cut by itself.
As another part of river management, stones, concrete blocks and geo bags are being thrown on the banks of the river. 8.5 lakh tonnes of stone is required at Mawa end and 30 lakh tonnes of stone will be dumped at Jazira end. 3,907,500 GIO bags weighing 800 kg will be dropped. 17,267,500 GIO bags weighing 125 kg will be dropped. Total number of cc block (cement concrete block) is 13,301,248.
The river management work at Mawa end will cover 1.6 km. And 12.4 km at Jazira end. The reason why there is so much work in the Jazira region can be understood by looking at the map of Bangladesh. The reason is that the water comes from the north-west with great speed and hits the Jazeera side more. Here, the water flows south-eastward.
Again, the soil type at Mawa site is slightly clayey or loamy. The Jazira site on the south side does not contain clay. There are silt, sand and sandy loam soils. It is more likely to corrode if the current is high. So this river management has been done on the Jazeera site for about 10 and a half kilometers. And Mawa site is only one and a half kilometers. In 2016, Mawa site unexpectedly experienced sudden erosion. Then some more work is done.
The issue of river governance is very difficult. Because scours in rivers can go so deep that some protection may be provided upstream. It was seen that the soil was washed away from below. Then the bank will collapse from above. Because there is no support below, the soil of the support has been washed away. For this, stones, concrete blocks and some new technology geo textile bags have been used from far below.
But a monstrous river like Padma which scours 65 meters, I am confused as to how much it can be governed, or what or how much profit is gained by governing it. However, the effort cannot be stopped for this of course. You have to keep trying.
The river management work may now have to continue forever. The contract will be renewed or a new tender will be issued. Otherwise, this bridge is difficult to sustain. Every structure needs to be taken care of. Or not last. I read somewhere a long time ago that Bangladesh’s national parliament is like petting the elephant of the poor. Its maintenance costs a lot. New elephants are coming to the country now! Anyway, these prove that the country is no longer so poor!
About The Engineering of Padma Bridge: The Feasibility Study
A report called prefeasibility study of this project was given in 2000. The initial feasibility study report of the entire project was given in 2005. Feasibility study can be said in very simple words, to calculate how much money will be poured behind it, how profitable it is, or whether it is profitable at all. Or where and how to get the most benefits for the least amount of money.
The objective of the Prefeasibility Study was to find the most suitable location for the Padma Bridge. During the planning of the Padma bridge in this stage, preliminary surveys were carried out at two places—Paturia-Daulatdia, another one was Mawa-Jazira.
The consulting firm was told, our main objective is to cross the river. So that vehicles can go up or down the river. The consulting firm first studied bridges and tunnels. It turned out that tunnels cost a lot more in terms of investment. Then the tunnel disappeared, the bridge remained to cross the river.
From 2001, the feasibility study started with funding from JICA. Site selection has started again. Studying from Goland to Chandpur, it was found that Mawa-Jazira site is the best.
Many things have to be considered in Feasibility Study, one is which direction will attract more traffic, that is exactly where people need the road the most, or more people need it. The second is where the course of the river is relatively less variable. Padma can move a kilometer or two every year. For this, to select a site, one has to see which one has been stable for a long time, meaning the river has been in the same place for a long time. In this case too, Mawa-Jazira was found to be a suitable place. The Feasibility Study (FS) recommended a preliminary design comprising a prestressed concrete extradosed bridge with railway provision.
However, the entire project is divided into two parts.
Phase 1: From Project Design to Tendering
Phase 2: Construction
Phase 1 which means this Padma Bridge (About The Engineering of Padma Bridge) designing work started in 2009. A team of national and international experts headed by AECOM was formed for the detailed design of Padma Bridge. The team also included SMEC International, Northwest Hydraulic Consultants and ACE Consultants, with additional assistance from Aas Jakobsen and HR Wallingford. Bangladesh Bridge Authority constituted a panel, consisting of 5 national and 5 international level experts. The task (About The Engineering of Padma Bridge) of this panel was to review the design of Padma Bridge as well as illustrate on About The Engineering of Padma Bridge after a certain period of time.
BS 5400 (British bridge design code) code is used for designing. Because its load and other things match the traffic conditions of Bangladesh.
A shipping study is done while designing the bridge by illustrating on About The Engineering of Padma Bridge. The study is such that if there is enough space under the bridge, all the ships sailing in Bangladesh will be able to pass under the bridge. According to the Bangladesh Inland Waterway Transport Authority (BIWTA) report, the highest recorded height of water during the flood should be 18.3 meters (60 feet), with a minimum of 3 spans. But here too there was trouble.
Padma is an unpredictable river. Padma sometimes carries huge amounts of soil from the bottom with the current. Sometimes a lot of silt comes with the current. Sometimes the river breaks its banks and changes its course. It was seen that the bridge stayed in one place, the river broke and changed course and went to the other side. As a result, building the bridge was almost futile. Sometimes the river suddenly wakes up. It was found that the three spans which were built 60 feet high for the passage of the ship, got up there, the passage of the ship was blocked. Because all other spans are not that high. Ships cannot pass under them. That’s why it was very critical to guess that if the span is high enough to pass a ship for the next 100 years (the design life of Padma Bridge), it will last, the char will not wake up under it, and the ship will be able to pass. Therefore, it was later decided that the number of spans should be increased as high as the ships go. All the spans along the roughly 4.8 km of river will be built high enough to allow ships to pass under any of them.
Again, the Padma river is a very droughty river. Along with its tendency to scour the riverbed and its location in an earthquake-prone area, the bridge has been, or is, facing considerable challenges in its design and construction. During the design of Padma Bridge, detailed earthquake studies were carried out. Buet did this to illustrate on About The Engineering of Padma Bridge. Two levels of earthquakes are studied.
1. Operating level earthquake: 65% chance of it happening once in 100 years. It is worse than the few earthquakes that occur in Dhaka or the country, but less harmful than the next level.
2. Contingency level earthquake: This earthquake is of very severe level. It comes once in 475 years. The probability of this happening is 20% in the 100 year design life of the bridge.
(These are all probability, data analysis. Maybe, maybe not. But it will happen, mathematics says so on About The Engineering of Padma Bridge.)
A three dimensional non linear time history dynamic analysis, using a modified Penzien model was adopted.
By selecting suitable/efficient seismic parameters from this study, the bridge is designed with them.
About The Engineering of Padma Bridge: The Challenges
The poor condition of the submerged soil and the thin clay layer made the issue more difficult. Therefore, the construction of the Padma Bridge over the huge river was a formidable obstacle.
But the engineers accepted the challenge, overcame it, and realised the ambition, establishing a precedent for future construction projects in the country and abroad.
They employed around thirteen technologies and conducted tests that had never been conducted before.
The two-story, 6.15-kilometer bridge is built of steel and concrete. The bridge was designed by Aicom, Spec International, ACE Consultants Ltd, and North West Consultations Ltd, while China Major Bridge Engineering Company was granted the building contract (MBEC).
The building work was divided into five sections:
The main bridge, river training, the Zajira approach road and chosen bridge-end facilities, the Mawa approach road and selected bridge-end amenities, and the establishment of service zones on either bank.
Up to 40 piers have been constructed beneath the bridge, with two more on each bank. Under each pier, steel piles with a three-meter diameter have been driven 122 metres down into the world’s deepest riverbed.
Prof. Shamim Z. Basunia, leader of the Padma Bridge project’s council of experts, described the Padma as a “unique” river owing to its geological characteristics and stated that the construction of the Padma Bridge was a test of skill and bravery.
The poor condition of soil at the Mawa end presented the greatest technical difficulty. Engineers were required to either avoid the clay layer or pile three metres above it. The thickest and deepest piles in the world were utilised for this project. “According to the Chinese company’s advice, steel was then cut into smaller plates in China. Engineer Shafiqul Islam, project director of the Padma Multipurpose Bridge, remarked, “Bangladeshi engineers went there and stayed there to monitor the work.”
Plates from the heaps were the first to arrive from that location. They had a diameter of 10 feet. The bent and welded construction of these pipes. Engineer Shafiqul Islam noted that the majority of welders were Bangladeshis. Each pile required an average of 20,000 to 30,000 blows to be hammered into position. Five state-of-the-art hydraulic pile hammers were deployed, including the biggest one in the world, manufactured by the German company Menk. Between the steel superstructure and the concrete pier foundation, modern Friction Pendulum Bearings (FPB) are used to support the steel superstructure of the bridge. Engr Shafiqul stated that such bearings have never been utilised anyplace in the world and can survive an earthquake of magnitude 9.0. The bearings of the Padma Bridge can support more than 10,000 tonnes, which is more than any other structure in the world.
Both banks of a 14-kilometer stretch of the Padma River have been constructed. Each geo bag weighs 800 kilogrammes and is used to safeguard the bridge. According to Engr Shafiqul, the government spent a total of Tk 900 billion on river training, the biggest amount spent on such activities worldwide. In addition to foreign resources, several indigenous materials including as cement, steel, geo bags, bricks, sand, and paints were utilised in the construction of the Padma Bridge. Local businesses of world calibre, like Bashundhara Cement, supplied the materials for the project.
Approximately 14,000 domestic and foreign labourers, engineers, and consultants worked around the clock to make the dream a reality. There were approximately 1,200 local engineers, 2,500 foreign engineers, 7,500 local employees, 2,500 foreign employees, and 300 local and foreign consultants.
The main challenges of this bridge were about the engineering of Padma Bridge:
– River management work
– Annual floods
– Its presence in an earthquake-prone area
– Deep pile foundation
– Soft clay at the bottom of the river
– Extreme scour depth
– Rehabilitation of affected people
– To ensure that the project does not harm the nature/environment
– Acquisition of land
– After awarding contracts to so many companies, maintaining coordination among them
– Construction of Padma Bridge with own funding.
This is all about the engineering of the Padma Bridge (About The Engineering of Padma Bridge )or Padma multi-purpose bridge.
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