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Corroded nuts and bolts likely contributed to the collapse of the Shivaji statue by causing a failure in steel members forming the frame inside the statue, according to a structural engineer.
“Ankles' of a statue, where the weight of the entire structure comes to rest upon, are most critical for stability and hence, require special attention during the design stage,” said Amresh Kumar, a structural engineer with a consultancy.
While officials have claimed that winds blowing at speeds of 45 kmph caused the collapse, wind speeds up to almost three times these are accounted for while designing a structure, according to the Bureau of Indian Standards.
“In this statue's case, external factors such as loads or climatic conditions do not appear to have caused trouble. Rather, corrosion in the nuts and bolts, as mentioned in the PWD report, could have caused a failure of steel members making up the frame inside the statue,” Kumar said.
On August 20, an assistant engineer at the Maharashtra Public Works Department (PWD) had written to Naval commander Abhishek Karbhari, Area Coastal Security Officer and Area Civil-Military Liaison Officer, pointing out that the nuts and bolts used in fixing the statue on the fort were catching rust because of exposure to ocean winds and rains.
“While steel members forming a structure - in this case, the statue's frame - are commonly protected against corrosion, the nuts and bolts used in connecting these members are commonly ignored, leaving them more vulnerable due to exposure to the environment,” Kumar said.
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He recommended that along with members, nuts and bolts also be protected, either by painting or galvanising, especially in coastal regions where the air is rich in moisture and salt, and is therefore, more corrosive. Galvanisation refers to applying a protective layer of zinc on steel or iron, usually by dipping them in molten zinc.
“Statues are, in essence, tall and slender structures supported on a compacted base, in which anchor bolts are closely or densely packed. Special attention, therefore, needs to be given to 'ankles' during the design stage, such that the statue's centre of gravity is maintained and does not cause tensions at the base,” he explained.
