How safe are our bridges?

Cracks and sinking have raised sharp questions about the reliability of the newly commissioned flyovers and other elevated structures in Kochi

It is a very bad time for the newly-commissioned flyovers and bridges in Kochi, with a dozen of them wracked by cracks and sinking.

The symptoms became full-blown following the discovery of a few dozen cracks on the Palarivattom flyover which was built as late as 2016 by Roads and Bridges Development Corporation of Kerala Limited (RBDCK), with KITCO as consultant. The findings of the Ministry of Road Transport and Highways (MoRTH) were vindicated by further technical studies done by experts from IIT-Chennai and the Vigilance and Anti Corruption Bureau (VACB).

It is uncertain when the flyover will be reopened to traffic after repairs. Experts are also sceptical of rehabilitating the structure using the costly ‘carbon fibre wrapping’ technology since they fear it may eventually have to be pulled down if that fails.

Bigger issues

The problems are just the tip of the iceberg as cracks were detected a week ago on the surface of two overbridges built by the PWD, both of which were commissioned over a year ago — one linking Kundannur with Nettoor and the Kannangattu bridge that links Edakochi with KUFOS. They happened to be less of a threat to the bridge structure since they occurred on the ‘wearing course’ that was provided over their deck. This is a substitute for bitumen surfacing to protect the structural concrete of the bridge deck from damage caused by moving vehicles and rainwater.

Even worse is in store for Kochiites as the one-year-old overbridge next to the Vallarpadam container transshipment terminal was closed to traffic for a month after motorists complained of unusual jerks. The bridge was built by the Cochin Port Trust using a Central grant and handed over to the National Highways Authority of India (NHAI) in February 2018. The approach portion of the bridge is sinking and it has to be rectified, port officials said.

Interestingly, all these structures suffered damage while they were within the defect-liability period, during which contractors are duty-bound to repair and restore them.

The overbridge parallel to the Bolghatty-Vallarpadam bridge and the Moolampilly-Kothad bridge too had been shut down for over a year after they suffered structural damage within months of their commissioning. They were built by the same contracting firm for NHAI.

Vyttila flyover

The discovery of cracks on the pedestals of the Vyttila flyover, which is built by the PWD (NH Wing), too has set alarm bells ringing. Officials swiftly stepped into damage-control mode, explaining that they were only temporary structures to rest the girders. “These [pedestals] will be dismantled when the post-integral beam is constructed. Another option is to support the girders using thick wooden blocks. But they might slip when girders are launched into place,” said a senior PWD official.

Responding to concerns expressed by the same consultancy firm (Nagesh Consultants) designing both the Palarivattom and Vyttila flyovers, the PWD has directed IIT-Palakkad to vet the design and suggest corrections, if any, for the Vyttila flyover which is slated for commissioning in December. “The PWD has a full-fledged design team. But it most often churn out conventional design which makes bridges look bulky. It is thus that private firms are relied on,” official sources said. The extensive proliferation of cracks on the Palarivattom flyover has given enough and more ammunition to people who see the lighter side in everything. They churned out dozens of trolls, ranging from one which said cement was being sprinkled atop the structure as sparsely as salt to season a dish to another which caught the change in expression of actor Mohanlal when he came to know that a police station was built by the same contracting firm that built the flyover. But there is no doubt that the whole of Kerala has been shaken by reports of cracks developing on the Palarivattom flyover and other structures in busy corridors.

Experts blamed shoddy design aimed solely at unduly cutting cost, slack vetting and supervision, apart from grave omissions in adhering to good construction practices as reasons for the damage that several newly-built flyovers and bridges suffer.

Caution thrown to the wind

“Inadequate attention to design can prove disastrous like what happened to the Palarivattom flyover. The factor of safety must be at least 50% more than the expected load that a structure will have to carry,” said an official who was associated with the construction of over half-a-dozen bridges in Kochi.

“This is because they often have to bear overloaded goods carriers, which cause severe deflection. Structurally weak constructions are thus prone to cracks. A higher factor of safety is also recommended since workmen deployed by many contractors may not be sufficiently skilled. There may be flaws in supervision too. In the case of the Palarivattom flyover, it is evident that KITCO threw caution to the wind while vetting its design,” the official said.

‘Adopt good practices’

Varghese A. Johns, a veteran civil engineer who worked for over 30 years in Singapore and West Asia, spoke of elaborate but well-established construction practices that must be adhered to for such elevated structures.

“There has to be a design-basis report which states the philosophy of design and the materials to be used. Then there must be a design system analysis and value engineering practice, followed by detailed engineering in which peer review / proof checking of the design is done. This is followed by preparation of tender documents, which must have detailed design drawings, materials to be used, and planning and scheduling of each component. The possibility of entrusting a sub-contractor and his qualifications too must be included,” he said.

The obligations of the client and contractor, preparation of quality manual and appointment of quality team too must be specified. Quality managers must ideally report to the government and not the client. Shoddy project management is all too evident at Palarivattom.

There must also be proper documentation and fixing of accountabilty. File notings must be made of even verbal instructions. KITCO should have ensured all this, Mr. Johns said.

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Printable version | Mar 26, 2020 2:10:48 AM | https://www.thehindu.com/news/cities/Kochi/how-safe-are-our-bridges/article28237445.ece

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