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Project Report

On

Mahatma Gandhi Setu

Made by : Sunny

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A view of Mahatma Gandhi Setu

Official name Mahatma Gandhi SetuLocale Patna, Bihar, IndiaMaintained by Bihar governmentDesigner Gammon IndiaDesign Girder bridgeMaterial Concrete & steelTotal length 5575meterWidth 25 meterNumber of spans 47Piers in water 40Clearance below 265Construction begin 1972Construction end 1982Opened May 1982Toll yesClosed No

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Introduction

Mahatma Gandhi Setu (also called Gandhi Setu or Ganga Setu) is a bridge over the river

Ganges connecting Patna in the south to Hajipur in the north of Bihar. Its length is

5,575 meters (18,291 ft.) and it is the longest river bridge in India. It was inaugurated in

May 1982 by the Prime Minister, Mrs. Indira Gandhi.

Gandhi Setu is an engineering marvel in its own. Constructing a bridge over the Ganga

near Patna where width of the river is enormous was always going to be a

challenging one. It took a decade to finish the construction work. The work was started in 1972, though this was sanctioned in 1969

only.

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Planning and Significance

The bridge was approved by the Central Government in 1969 and built by Gammon India Limited over a period of ten years, from 1972 to 1982. It was built in connect North Bihar with the rest of Bihar. Before this bridge was constructed, Rajendra Setu, opened in 1959, was the only link to North Bihar. Since then, the Vikramshila Setu has also been built across the Ganges. Two more rail-cum-road bridges are currently under construction, between Digha and Sonepur and at Munger.

The Indian postal department issued a commemorative postage stamp on Landmark Bridges Of India: Mahatma Gandhi Setu of denomination 0500 Paise on 17 August 2007.

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Gandhi Setu: An engineering marvel

Asia’s longest river bridge, Mahatma Gandhi Setu, popularly known as the Gandhi or Ganga Setu, is a marvel of both engineering de sign and technology. Inaugurated by the then Prime Minister Indira Gandhi in 1982, the 5.75km-long bridge became the lifeline of north Bihar.

Touted as a true engineering marvel, a miracle of equilibrium and graceful in appearance, it was constructed by Gammon India with an expenditure of Rs 87.22 crore. The river bridge has 45 intermediate spans of 121.065 metres each and one span of 65.530 metres on both sides. The technology used in the bridge was prestressing —

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cantilever slabs with hinge bearings and box girder.

It took over a decade to construct this wonderful feat of engineering genius. Though the project was sanctioned in 1969 by the Central government, construction work could begin in 1972

Cont…. In fact, before the inauguration of the Setu, north Bihar-bound people from Patna had to negotiate the Ganga either using a boat, a ship or a steamer. The only other option was taking a long and tiring rail route. So the basic purpose of the Setu was to cut short the travelling time from the state capital to north Bihar.

The view of river Ganga flowing down majestically below is simply breathtaking. Hundreds of pedestrians and over 40,000 vehicles ply every day across the longest cantilever bridge of Asia. Since its

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inauguration in 1982, the Gandhi Setu has been the passage of myriad activities. While brisk business is carried on at the one end of the bridge in the capital town itself, the same is happening in the various districts and towns of north Bihar. Both the markets together provide livelihood for over 1, 00,000 people. Besides, thousands of people visit these markets from far off places every day. All acknowledge the role of this towering bridge in their business and daily life, creating a bond between two generations.

Cont…However, the Setu is now stressed beyond limit under the weight of heavy vehicles constantly plying over it from Patna and North Bihar and threatening its existence.

Two pillars of the bridge developed cracks four years ago, only 26 years after it was inaugurated. It wasn't supposed to,

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considering that it was flaunted as an engineering marvel that would serve people for at least a century.

Poor maintenance, coupled with wear and tear caused by the unprecedented surge in traffic, has made the structure vulnerable. If a larger crack develops, it will sever the lifeline between the state capital and north Bihar.

"For us the Setu is our lifeline. If there is further damage, the entire communication network with north Bihar will be paralysed," said principal secretary, road construction department, Pratyay Amrit.

Engineering Details

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The bridge consists 45 intermediate spans of 121.065 meters (397.19 ft.) each and a span of 65.530 meters (214.99 ft.) at each end. The deck provides for 7.5 meters (25 ft.) wide two lane roadways for IRC class 70 R loading with footpaths on either side. The cantilever segmental construction method was adopted to construct this mega bridge.

Longest bridge in India

The Mahatma Gandhi Setu Bridge over the river Ganga in Patna is the world's longest

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river bridge. The bridge spans over 5.575 km from Hajipur at the north end to Patna at the south end. Patna is located on the south bank of the river Ganga. Patna has a very long riverline, and it is surrounded on three sides by rivers Ganga, Sone, and Punpun. Just to the north of Patna across the river Ganga flows the river Gandak.

Patna is a historic city and an important pilgrimage center for Sikhs, Buddhists, and Jains. Patna houses one of the five Sikh Takhats -Takhat Patna Sahib. The Buddhist and Jain pilgrim centres of Vaishali, Rajgir or Rajgriha, Nalanda, Bodhgaya and Pawapuri are all nearby. It is the ideal gateway for all the places on this circuit.

Efforts on to repair Gandhi Setu's superstructure

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It's a very challenging task for us as due to the structure of the bridge, nobody could know how to change the superstructure. So, for the first time in the country and probably in the world as well, the superstructure is being repaired," said Amrit.

Interestingly, neither any of the pillar of the bridge is damaged nor its foundation is weakened, but the problem is with the distressed hinges and finger-type expansion joints - a failing of pre-stressed technology. Stands 44 to 46 are being repaired and the work is going on continuously for some days now, he added.

Since trucks' entry has been completely banned, state's traders are facing heavy loss. For, they are forced to bring their goods to Muzaffarpur, Darbhangha, Motihari and all other regions on this part of the Ganga by

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smaller trucks after paying heavier freight as the rate for smaller vehicles is higher. When asked if there is any alternative arrangement for the heavy vehicles, Amrit said a firm "no". "We expect when the Mokama bridge will be functional, the traders will be relieved," he said, adding the department has also been requesting the Railways to expedite the repair works of the Rajendra Pul so that it could be made open for heavy vehicles.

The 40-pier bridge was inaugurated in May 1982 by the then prime minister Indira Gandhi. At that time, its life span was stated to be over 80 years. But heavy traffic volume estimated at over 30,000 vehicles a day and lack of timely maintenance have resulted in tearing apart of its hinges well ahead of time.

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Rehablitation of Mahatma Gandhi Setu in Patna

1. Introduction

The Mahatma Gandhi Bridge was constructed about 25 years ago over the Ganges River in order to connect patna to the other side of river. Once completed it was supposed to be the part of N.H 19 and comes directly under Central Government of India. It is one of the longest bridge in india. The bridge has 46 spans each with length 120m. Each span has two cantilever beams on both sides which are free to move at the ends. It has two lanes one upstream and the other downstream each with a width of around 6m. Both the lanes are also free from each other and are not connected anywhere. It was constructed by using 3 meter pre-casted parts being joined at both ends to complete the span. The Spans are connected by using a Protrusion which is free to move longitudinally also along the river flow. In upwards and downwards direction it is such that it allows vibration to transfer smoothly to the next span while vehicular movement without much discreteness. It is shown in fig.

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Due to heavy traffic movement and being the only bridge to cross ganges river the bridge is used heavily now. Hence it has started vibrating with a higher amplitude than it was designed to. Also in many spans the cantilever beams were found to have sagged at ends.

2. Rehabilitation Keeping the structural health prospective in mind it was decided for immediate rehabilitation of the bridge to provide extra strength to the spans so that it bear the existing vehicular load according to the IRC.

2.1. For Rehabilitation the following steps were proposed:- External Pre-stressing of the bridge using 9 steel cables in a bunch. It was decided to pre-stress from 6 places starting from the end towards the center portion as shown in fig. It has to be done on both ends along the width rather than in centre making it at 12 places in each cantilever. In each cable a load of 16 tons, or 450Kg/cm3 jack pressure, individually has to be given. All these cables are to be enclosed within pipes and then filled with cement mortar to make it permenant. The anchor are to be made permanent by enclosing it with a cement cube. These cables will further lift the cantilever beams and support the structure.

Fig.1

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Fig 1. The cables positioning along the span of bridge.

Grouting of cracks wherever they are visible. It has to be done by putting nozz

Stitching of spans by using steels jackets in some spans whose condition is not good.

2.2. The Rehabilitation Process The external pre-stressing is done using steel cables anchored at both ends of the span. 9 of these cables are bunched together at one place and anchored using steel structures bolted to the bridge by means of permenant anchors as shown in Picture Set 1.

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Picture set 1. The steel structures and anchors at the site.

These are situated at 6 places through the cantilever beam so that the bridge can be lifted at all places uniformly. Each of these cables is then stressed from both the ends by using clamping jack and hydraulic pump system shown in Picture set 2.

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Picture set 2. The cable holding jack and the hydraulic pump system powered by electricity. This stressing is done to on both sides of the cable and simultaneously to cables at both ends of the width. Hence at a time 2 cables are stressed. This is done to make the load distribution symmetric on the span which is important to avoid any kind of load developed locally in the span. All stressing is done in a very systematic manner. Each of these cables is given a load of 450Kg/cm3 in steps of 50Kg/cm3. After stressing all the cables in all the six places over the cantilever the whole system of buched cables is packed with cement mortar and made permanent. After stressing the span looks like in Picture Set 3.

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Picture set 3. The span after final external Pre-Stressing by cable bunches.

3. Instrumentation

For Measuring the effectiveness of external Prestressing following testing was also carried out in the bridge spans.

3.1. Strain measurements:-

Strain Gauges were installed at 24 places as follows. As each cantilever span is pre-stressed the strain in the span is relived and to correctly measure all the strain change in the top, bottom, and the two side slabs strain gauges were installed at these parts. There were total six cross-sections were identified, 3 in each arm of the span. At each cross-section one was installed at the bottom of the

top slab, one at the top of soffit slab and the other two on the two walls on either side. The gauge placement plan is shown in Fig 2.

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Figure 2. The Strain Gauge placement plan. The gauges were named according to there positions. Each cross-section was named from A to F starting from patna side. At each cross-section the one at the top is suffixed by a T, the one at the bottom by B, the one in the upstream direction side wall by U and the one in the downstream direction side-wall by D. Hence AT will be the

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gauge at top and in A cross-section, BB will be gauge at bottom in B cross-section and likewise.

3.1.1. Different elements used for Strain measurement

The strain gauges used are PL-90-11 TML make

Picture 4. The PL-90-11 TML made Strain-Gauge.

The adhesive which is used for sticking it to the concrete surface is CN-E type adhesive of TML make.

The wires used for strain measurement are three wire cored type.

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The switcher unit is a HBM Germany make which can be used for 10 half-bridge strain gauges and 4 full bridge gauges. Hence for 24 strain gauge measurements we need 3 of these switcher units as we are using it in a half-bridge configuration.(Picture 5)

Picture 5. The HBM Germany made Selector Unit used for selecting the strain gauge

The read-out instrument is P3 Strain Indicator and recorder, of Vishay Micro-Measurements make, which has 4 channel inputs. So we can connect four of switcher units to it. It can be set for any bridge configuration. It gives readings directly in micro-strains.

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(Picture 6)

Picture 6. The Vishay P3 strain indicator used to indicate the strain gauge readings

A dummy gauge has to be made using a concrete block, made of the same concrete as of the testing surface, and a strain gauge installed over it. This is required for completing the Wheatstone bridge circuit and also to compensate the effect of self-heating of the strain gauge on readings.(Picture 7)

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Picture 7. The Dummy Gauge prepared on a different concrete block whose strain is independent of concrete.

General accessories like acetone, soldering unit, wires, fewikwik, tape, clamps, screw drivers etc. are required while installing the strain gauges

3.1.2. Procedure for Strain-Gauge installation:-

1. The surface is first marked properly as to where exactly the strain gauge is to be placed.

2. This surface is then grinded well to remove all the loose concrete and dust so that the gauge can be fixed on a hard concrete surface.

3. It is then cleaned thoroughly and then the marking is done again which got erased due to grinding using the end lines.

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4. In order to make the surface very smooth and fill small unevenness it is applied with Araldite and levelled.

5. After the araldite surface is hardened it is rubbed

with sand paper to make it further plain. It is then again cleaned with acetone to remove the sand paper remnants.

6. The Strain-Gauge Adhesive i.e. CN-E is applied over the gauge and it is then glued slowly and carefully so that no kinks are formed it is then applied pressure slowly by keeping a paper, supplied with the gauge, until it is smoothly bonded to the surface.

7. The connections are made using the dummy gauge and the core wire. Dummy gauge block is clamped to the surface near to the strain-gauge. Dummy gauge is required to complete the Half-Wheatstone Bridge and compensate for the deviation caused by self-heating of the gauge. It can be seen in Picture Set 8

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Picture Set 8. The dummy gauge connections and final placement.

8. The other end of the wire is then soldered to the connecting port of the switching unit. Switching unit is basically used to switch between different gauges. In one switching unit 4 full bridges can be connected and switched between and up to 10 half bridges can be connected and switched between. By using this switching unit only one read out instrument is required to get the readings. Otherwise it will be too demanding and tedious. 9. The readout instrument has 4 channel inputs and hence 4 switching units can be connected directly. In this case we have only 3 inputs so we will use 3 channel input. It gives readings directly in micro-strains.

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Picture 9. The whole setup including 3 Switcher Units and strain indicator used for strain measurements.

10. When all the instruments are in place readings can be taken. The readings are taken before and after external stressing of cables. It should indicate that what relive of strains we are achieving.

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3.2. Deflection measurements:-

When the span is externally prestressed by cables it causes the tip of the cantilever arms to move up with respect to the middle of the center of span. The cables pull the arms upward due to the stressing done. To confirm this it is necessary to note down the initial deflection and the final deflection after prestressing by cables. This is done by putting water tubes at both ends of the span. Three pipes are used two at the ends along the width of arm and one at the middle. The initial and the final readings are taken on a scale with a least count of 1mm on both sides of all 3 pipes. The difference between one side reading and the other side reading gives the deflection and comparing the deflections before and after stressing we can get the effective change caused by Pre-Stressing.

3.3. Temperature measurements Temperature variations throughout the day are quite significant. As they cause the stress to increase or relive and also the deflection in the cantilever arms to vary. It is important to consider the effect of temperature. For this purpose PT type sensors are installed at the surface inside and outside the bridge. The ambient temperature thermometer is also installed outside and inside the bridge span. A temperature cycle is performed and all the readings i.e. the strains, the deflections and temperature is noted down one day before the day stressing is planned to be done. These readings become the basis for the correction required due to temperature variations.

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The readings of before stressing and after stressing are compared according to the time and temperature at which they are taken. This further refines the readings to find efficacy of Pre-Stressing.

Gandhi Setu's span to be rebuilt

Commuting through Mahatma Gandhi Setu has become dangerous as its span number 44 on the western flank is heavily damaged and literally dropping. It is all set to be demolished and reconstructed.

Traffic had considerably eased on the Asia's longest road bridge after the toll plaza had been closed. But traffic movement has been severely impaired on the lifeline of north Bihar following the stone mastic asphalt (SMA) laying work, also called stone-matrix asphalt, on the bridge.

"Tender for reconstructing span 44 has been passed and the demolition work will start within a month," said road construction minister Nand Kishore Yadav on Wednesday.

It may be mentioned that SN Bhobe and Associates had submitted a report to the NHAI on this span and the need

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for its replacement.

"The setu is RCD's biggest concern. However, the ongoing SMA laying work is very important as it will help reduce the weight of the PCC road. This work can be undertaken only in parts. Hence, both the eastern and western lanes are now undergoing SMA work. This has hampered the traffic movement. Span 44 will be demolished very soon and it will further cause inconvenience to the commuters. Incidentally, the work will continue till October-November. However, most of the traffic snarls are due to overtaking of vehicles," said RCD secretary Pratyaya Amrit.

Cont……

As suggested by SN Hobe & Associates for repairing the bridge, the SMA work has been undertaken as it provides deformation resistant, durable surfacing material, suitable for roads having heavy traffic. The stone skeleton is filled with bitumen mastic to which fibres are added to provide adequate strength to bitumen and prevent drainage of binder during transport, said an RCD engineer.

"To deal with traffic jam, the foremost need is to keep the

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traffic moving as this will not only ease the pressure but also give the travellers a psychological relief. Though they would be covering a larger distance, at least they will reach their destination without facing traffic snarls. We are always in touch with Vaishali district administration and cops to man the movement on the setu for smooth flow of traffic. However, frequent overtakes and breakdown of heavy vehicles often lead to huge traffic jam," said Patna district magistrate N Saravana Kumar.

The bridge has been been in trouble recently due to faults in the technology used, the lack of maintenance and ever increasing traffic volume on the bridge. Two pillars of the bridge developed cracks, much to the surprise of all, as it was considered to serve flawlessly for a century. One way or either at some place over the bridge is always under maintenance, causing heavy traffic jam. It is estimated that roughly 40,000 vehicle use this bridge everyday. It is hoped that once Ganga Rail-cum-Road Bridge, that is under construction, starts operating, the load on the Gandhi Setu will ease. Nevertheless, the bridge is a wonderful feat of engineering, and one should always try to enjoy the ride over it, at least once.

Bridges across the Ganges in Bihar

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The Ganges divides the state of Bihar in two parts. The mighty river makes communication between the two parts a difficult task.

The first effort to bridge the gap was Rajendra Setu in 1959. The next bridge across the Ganges in Bihar was the 5,575 meters (18,291 ft.) Mahatma Gandhi Setu, the longest bridge in India at the time of its commissioning in 1982. It was followed by Vikramshila Setu near Bhagalpur. The fourth bridge across the Ganges in the state is the Ganga Rail-Road Bridge.

is also under construction.] A 5.575 km long bridge, under construction, will connect Bakhtiyarpur and

A bridge has been planned across the Ganges to connect Arrah and Chhapra. A road bridge parallel to the existing rail and road bridge, Rajendra Setu, has also been planned.[

 

Ganga Rail-Road Bridge

Ganga Rail-Road Bridge is an under-construction Bridge across river Ganges, connecting Digha Ghat in Patna and Pahleja Ghat in Sonepur in the Indian state of Bihar. Upon completion in March 2015, the bridge would provide easy Roadway and Railway link between Northern and Southern parts of Bihar.

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The projectPresently, Rajendra Setu is the only bridge that carries railway tracks across the Ganges in the state of Bihar. It was opened in 1959.

Initially sanctioned as a rail bridge, the Ganga Rail Bridge project was converted to a rail-cum-road bridge in 2006. Total cost of the project was put at 13,890 million, out of which 8,350 million was for the rail part, and 5,540 million was for the road part. It was expected to be completed in five years.

When completed, the 4,556 meters (14,948 ft.) bridge would be amongst the longer bridges in India. The total length of construction, including approaches, would be 20 km. It would be a K-truss bridge.

According to a media report the bridge is expected to be completed by 2017. Railways is working hard to complete Ganga Rail-Road Bridge project within the stipulated time of March 2015 to ease the huge traffic flow on the Mahatma Gandhi Setu.

Entry of 10-wheelers banned on Gandhi Setu

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With Rajendra Pul across the Ganga connecting Mokama and Barauni already closed for heavy vehicles for the last six months due to its weakened structure, the blanket ban on entry of 10-wheel trucks on Mahatma Gandhi Setu near Hajipur from Monday to save the bridge from further damage is bound to hit the economy of north Bihar region hard as it would create scarcity and increase the prices of all industrial goods for which it entirely depends on outside supply.

Vaishali DM Vinod Singh Gunjiyal confirmed on Monday that the ban had been made effective with immediate effect on the basis of a letter from the chief engineer of Bihar Pul Nirman Nigam. He said he had asked SP, Vaishali, to stop the entry of all trucks with 10 wheels and above. The step has been taken to save the bridge from further damage.

Reacting sharply to this ban, president of North Bihar Chamber of Commerce and Industry (NBCCI), Motilal Chhaparia said on Monday that traders will be forced to bring their goods to Muzaffarpur, Darbhangha, Motihari and all other regions on this part of the Ganga by smaller trucks after paying heavier freight as the rate of freight is higher for smaller vehicles. He suggested the government should immediately take the help of the Army to build a pontoon bridge by the side of the existing bridge to divert the traffic and repair the damaged portion of the bridge at the earliest.

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Architecture

This bridge was built by Gammon India Limited. It consists 46 spans of 121 meters (397 ft.) each and 2 spans of 63 meters (207 ft.) at each end. The deck provides for a 7.5 meters (25 ft.) wide two lane roadways for IRC class 70 R loading with footpaths on either side.

The cantilever segmental construction method is adopted to construct this mega bridge. 650 million or 65 crore (at 1972 prices of India) rupees of public tax money were spent on constructing this bridge. The 5.575 km long architecture of Mahatma Gandhi Setu consists 46 spans of 121.065 Meter each and 2 spans of 63.53 Meter at each end. The deck provides for a 7.5M wide 2 lane roadway for IRC class 70 R loading with 2M wide footpaths on either side

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Mahatma Gandhi Setu bridge, Patna, Bihar: facts, Photos

Before Mahatma Gandhi setu was built in Patna, people going to north Bihar had to cross river Ganga by boat, a ship or a steamer. Other option left with the people was to take a rail route which was very long. But with inauguration of Gandhi Setu in Patna, this distance and pain of traveling to north Bihar was greatly reduced. Its importance can be judged from the fact that more than 40,000 vehicles pass this bridge everyday.

But the sad part is that Mahatma Gandhi setu in Patna is not in good condition now. Its many pillars have developed cracks due to bad maintenance, huge amount of traffic on this bridge.

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Bibliography en.wikipedia.org/wiki/Mahatma_Gandhi_Setu

wikimapia.org › India › Bihar › Hajipur

www.go4patna.com/index.../287- mahatma - gandhi - setu -bridge-patna

www.nativeplanet.com › Bihar ›

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Patnamons.wikimedia.org/.../File:Gandhi_Setu_Bridge_in_Patna,_India.jp..

www.thecolorsofindia.com › Interesting Facts › Infrastructure

www.biharspider.com