The Maitri Setu (Friendship Bridge), also called the Gateway of Northeast, was inaugurated by Indian Prime Minister Narendra Modi and Bangladesh Prime Minister Sheikh Hasina on March 9. The bridge is of economic importance to the region and will link Tripura in India with Bangladesh. The Friendship Bridge is expected to strengthen relations and connectivity between India and Bangladesh. Here is a report on that project. ________ The Friendship Bridge will play an important role in the proposed economic corridor that will connect India, Bangladesh, China and Myanmar and boost trade and commerce among these countries. Further, the remote and quiet town of Sabroom in Tripura will benefit massively.It will connect Tripura with Chittagong Port in Bangladesh, which is 70 km from the border. Agartala, the capital of the state, will become one of the Indian cities located close to an international seaport, unlocking untapped markets of other eastern and south-eastern economies.The bridge is a harbinger of economic opportunities for the two countries. Completed: March 2021 Length: 1,888 m Developer: National Highways and Infrastructure Development Corporation (NHIDCL) Contractor: Dineshchandra R Agrawal Infracon Consultant: ASC InfratechInitial brief The project was awarded to Dineshchandra R Agrawal Infracon on 31 March 2017, by the National Highways and Infrastructure Development Corporation (NHIDCL) at an estimated cost of Rs 82.57 crore. The project was planned as a link road and bridge taking off from NH-44 at Sabroom (India) to Baraiyaghat-Magarcheri Road (Bangladesh) across river Feni. In the Indo-Bangladesh Joint Communique of January 2010, the prime ministers of the two countries had decided to develop land customs stations (LCS) at Sabroom-Ramgarh and Demagiri-Thegamukh and had agreed to undertake measures to strengthen infrastructure. This bridge will help operationalise the two LCSs. The project comprises the construction of a viaduct cum extradosed bridge with a total length of 422 m that includes 180 m length of extradosed bridge with a span configuration of 50+80+50, and a viaduct in approaches with a length of 242 m (55 m on the Indian side and 187 m on the Bangladesh side). The project also includes approach roads of 1.1 km and 0.3 km towards the Indian side and Bangladesh side, respectively. The extradosed bridge was planned as a balanced cantilever construction with the concrete cast in place with the help of a CLC gantry. The foundation of the bridge is 1.2 m diameter bored cast-in-situ piles. The approach viaduct is a continuous two and three span units with individual spans approximately 29 m with a steel beam composite structure with a cantilevered diaphragm. The design challenge Considering the nature of the structure and the construction time constraint because of the monsoon, the bridge was designed expeditiously to ensure timely completion. Also, the bridge had to be designed keeping in mind the fact that it lies in Seismic Zone V as per Indian Standard. This made the design more complicated. To remedy this situation, the extradosed bridge was planned as an integral structure. However, the middle span of the bridge was 80 m and the substructure height was comparably small, making it very stiff. To make it flexible, the pile cap was lowered below the low water level. The bridge could not be designed as a single cell box as the extradosed bridge has a width of 14.8 m and has two planes of cable. A double cell box would also have resulted in additional diaphragm requirement at the stay cable location. Hence, it was decided to have a three cell box superstructure. “It was also difficult to erect PSC girders, especially towards the Bangladesh side, as it was not possible to move heavy cranes across the river. For this, we planned for a steel composite structure,” shares Ankit Agrawal, Director, Dineshchandra R Agrawal Infracon. The bridge was designed on MIDAS software. Cable system The extradosed bridge has two planes of cable and three cables each. The lower pylon is flared to accommodate the three cell box superstructure. The upper pylon is 9 m high. The cable system used is DSI with DYNA Link on the pylon. Ensuring timely delivery The stipulated completion period for the project was 30 months. But, in Tripura, the monsoon starts in March and ends in October, bringing down the actual time for construction to only six months a year. The two sides of the bridge are separated by the international border with no check post; the nearest location for the transport of material and machine was at least 40 km away. This issue was resolved by making a temporary bridge across the Feni and extending the boundary fencing of the Indian side along the right of way (ROW) of the project up to the Bangladesh side of the bridge. Given the time constraint, two pairs of CLC gantries were used to facilitate timely construction. The bridge was constructed in very challenging conditions, which included adhering to all security protocols of the international border, flash floods in the river during the monsoon and, above all, the Covid-19 pandemic. Labour requirement “Specialised labour was required for the project, which was not available locally,” Agrawal additionally informs us. “On average, about 200 labourers were mobilised during peak time and works were executed with all safety precautions, including PPE kits.” - By Praharshi Saxena