Kolkata disaster throws up questions on maintenance of Bengal’s old bridges, flyovers
While ministers and state government officials refrained from commenting on possible reasons that led to collapse of the Majherhat bridge, local people and experts blamed lack of maintenance.
Collapse of a section of the 40-year-old Majerhat bridge in south Kolkata on Tuesday not brought back memories of the Vivekananda flyover collapse that claimed 27 lives at crowded Jorasanko in the heart of central Kolkata on March 31, 2016 but also raised uncomfortable questions about the condition of old bridges in Kolkata.
A portion of the under-construction flyover at Jorasanko caved in, killing 27 people and injuring more than 90. A few hours after the crash, an official of the construction company, Hyderabad-based IVRCL, described the disaster as an “act of God.” The statement led to a free-for-all in the run-up to the Assembly polls.
While ministers and state government officials refrained from commenting on possible reasons that led to collapse of the Majerhat bridge, local people and experts blamed lack of maintenance.
“A few years ago, subsidence was detected in a portion of Majerhat bridge and Eastern Railway authorities repaired the portion,” a state public works department (PWD) official said on condition of anonymity.
Incidentally, after the Vivekananda flyover collapse, chief minister Mamata Banerjee instructed the state Public Works Department (PWD) to form an inspection committee comprising officials from various departments and agencies and inspect every bridge and flyover in Bengal every month. Tuesday’s incident somehow indicated that this was not being done.
“The Majerhat bridge carried the load of more heavy vehicles and containers since the area is close to the Kolkata port. When we are looking at a structure this big, girders, cross-girders, bearings et al should be periodically inspected and repaired,” said structure engineering and Jadavpur University professor Partha Pratim Biswas.
“It is possible that extensive digging that was done by the Metro Railway authorities for the Joka Metro extension project not far from Majerhat bridge. This could have resulted in rainwater gushing through underground tunnels and weakening the base of the old structure,” a structural engineer said on condition of anonymity since he is working with a PSU.
“The Majerhat bridge in more than 30 years old and it is a concrete structure that needs less maintenance than a steel structure. In this case, nobody can question the quality of material and craftsmanship. It is only the age factor that can we can take into account. But the state government was aware of the age factor that ails many old bridges. It also got a survey done by experts from Indian Institute of Technology (IIT) Kharagpur. However not much was done,” said the structural engineer.
“Majerhat bridge should not be taken as a case in isolation. A portion of the flyover connecting Ultadanga to VIP Road in east Kolkata collapsed on March 3, 2013 because of design failure that was not detected even three after it was constructed and opened to traffic. Acting on the survey report, the state government repaired portions of the Chingrighata flyover in east Kolkata and Sukanta Setu in south Kolkata,” the engineer added.
In March 2013, a huge portion of the Ultadanga flyover collapsed at 4:30 am. There was hardly any traffic and only a truck fell into the canal below the flyover. The driver and two other passengers were rescued. Urban Development Minister Firhad Hakim said at that time that a crack was detected in the flyover one-and-a-half years ago and examined by experts from Jadavpur University. The problem detected was not related to maintenance but a technical one, he said.
Experts who conducted probe at the site of Vivekananda flyover in 2016 blamed design flaw and use of inferior material for the disaster. They dismissed the construction company’s initial argument that the incident was an “act of God.”
In April, 2016, structural and civil engineers with decades of experience in building bridges across the country, told HT that structural flaw of a T-shaped pillar - technically a cantilever pier -led to the collapse. A cantilever bridge rests on structures that project horizontally into space only on one end.
“The design of the pier head (the t-junction) was inadequate. The arms simply buckled under pressure of the steel and concrete,” Achyut Ghosh, a bridge expert and visiting professor at IIT Kharagpur, Jadavpur University and IIEST in Shibpur, told HT on April 2. 2016. “The bridge was yet to be inaugurated, and therefore, there were no pressure of vehicles that a functioning flyover carries. This proves that it was simply a design failure,” added Ghosh.
“This was preventable. It can’t be called an accident,” he added.
Experts also pointed out that cantilever piers are one of the most unstable structures and are usually avoided. If absolutely necessary they are meticulously designed and need perfect implementation with strict quality check of materials.
“It appears to be a technical failure. What was running on two pillars (at the start of the bridge) has converged on to one pillar. But this single pillar did not have adequate strength,” said professor Arun Chakravarti of IIEST, Shibpur.
Incidentally, lack of maintenance or inferior material are not the only factors that ails old bridges in Kolkata.
In December 2017, Kolkata Metropolitan Development Authority conducted emergency repairs on 50-year-old Dhakuria bridge in south Kolkata as rats had chewed into its foundation at both flanks. “The foundation faced risk a few years ago because rats chewed away soil from its base. Repairs had to be carried out. Gaps appeared on the road surface because certain portions caved in,” said a KMDA official on condition of anonymity. Like Majerhat bridge, Dhakuria bridge too runs over the tracks of Eastern Railway’s south suburban section.
First Published: Sep 05, 2018 07:42:31