Opinion Gujarat bridge collapse: We need an audit of ageing infrastructure

At the time of construction, the bridge was designed in accordance with the working stress method as per the then-applicable Indian Roads Congress (IRC) codes. These codes prioritised strength, safety factors, and material durability (for example, quality of concrete cover, exposure class), rather than an explicitly defined service life period. Usually, properly executed prestressed concrete structures undergo less vibration and shaking while crossing the bridge. Crack-free prestressed member is a must for long-term performance.

It was a prestressed girder failure mostly from the centre, which broke the span in two pieces. Usually, girders are more critical than piers in this type of a bridge as the latter is subjected to an axial compression while the girder is subjected to tension in the bottom. Concrete material is very strong in compression while very weak in tension. Further, deterioration in the concrete starts from the bottom of the slab and the girder, which aggravates the situation.

The sudden and catastrophic failure of the prestressed concrete girder type bridge might be because of the corrosion of prestressed cables, especially due to moisture ingress — through poor quality of cover concrete and cracking, poor grouting of cementitious material into duct, fractures or cracks in the wall of the duct, which leads to corrosion of prestressed cables.

Prestressed concrete girders rely on tensioned steel cables (tendons) to maintain compressive stress in concrete. When multiple tendons lose their load-carrying capacity, the bridge girder behaves like a non-prestressed member, becoming structurally inadequate. Once these cables lose tension, the girder can no longer carry its design loads, and a sudden, brittle collapse becomes a real risk. The corrosion of ordinary reinforcing steel in the soffit of the girder due poor quality of cover concrete also contributes significantly to failure.

Prevention strategies

To prevent failures like the Gujarat bridge collapse, the following bridge maintenance strategies are strongly recommended for such types of prestressed concrete structures.

First, there should be routine visual inspections (every six to 12 months) to check for cracking, spalling, rust staining, exposed reinforcements, water seepage, and joint displacement.

Second, vibration and dynamic monitoring, including installation of accelerometers or vibration sensors to detect frequency shifts, are needed. Vibration analysis gives early warning signs of prestressed tendon deterioration.

Third, as a part of load management, the administration should install weigh-in-motion sensors to monitor and control axle loads in order to prohibit or restrict overloaded vehicles on aging bridges. Non-destructive testing (NDT) at 5-10 minute intervals, which includes half-cell potential testing to assess corrosion activity in the tendons, should be conducted. Ultrasonic pulse velocity testing or impact echo testing can detect internal cracks and magnetic flux leakage or ground-penetrating radar for hidden corrosion and voids in grouted ducts.

Fourth, a long-term digital bridge health monitoring system should be implemented for data tracking in critical parts of the bridges’ structures. Finally, elastomeric protection coating shall be applied to cover concrete, especially in the bottom of the slab and girder at an interval of five years to protect steel reinforcement against corrosion.

Proper structural strengthening, prompt timely inspection and regular maintenance of such structures is only the solution to prevent such accidents. Forensic structural investigation must be carried out by conducting core extractions to know the compressive strength of concrete. Corrosion analysis of ordinary reinforcement and prestressed cables, prestressed tendon testing, and anchorage zone inspection can help determine the failure.

Such accidents can possibly be prevented with the right systems and regular attention. I hope that beyond the emergency response, this collapse leads to a wider audit of ageing infrastructure — not just in Vadodara, but across the country. We need to remember that bridges, like all structures, have a lifespan. When that lifespan nears its end, no matter how well they were built, they require more than just repairs — they need serious review, monitoring, and, when necessary, timely replacement.

The writer is Head, Department of Applied Mechanics and Structural Engineering, MS University of Baroda, Vadodara