BENGALURU: Vegetation growing from cracks, retaining-wall surfaces pointing to possible moisture ingress, cracking and reinforcement corrosion (rust and breakdown of steel bars inside concrete) at the KR Puram cable-stayed bridge have raised concerns, while also raising questions over whether authorities are carrying out regular maintenance. Senior officials from the Bengaluru East City Corporation pointed out that the bridge surface is maintained by the corporation, while its structures that is above the railway track are the responsibility of the railway department.
One of Bengaluru’s technically significant structures, it was commissioned in 2003. The bridge carries four lanes of traffic over the Krishnarajapuram railway station on a 106-metre cable-stayed main span.
Chandrashekar Sharma, General Manager (Technical), STRUCT REHAB Pvt Ltd, said that vegetation emerging through structural or retaining concrete is not just a housekeeping issue. It can indicate cracks, joints, voids, porous concrete or pathways through which moisture has entered, and root growth can progressively widen openings and retain moisture, accelerating deterioration.
Agreeing with him, a senior engineer from Greater Bengaluru Authority’s Road Infrastructure wing said the bridge was designed for the traffic and loading conditions of early 2000s. Bengaluru’s eastern corridor has since undergone substantial urban and traffic growth, and the bridge now operates in a far more intense environment.
“There is something called Structural Health Monitoring (SHM) of Bridges and Flyovers. The growth of trees and their roots becoming stronger by the day is evidence that these factors have not been given prominence. An assessment of all the bridges should be done on priority,” said the engineer.
The assessment should weigh current traffic volume and composition, heavy commercial-vehicle movement, traffic loading and induced vibration, present lane usage and repeated loading, congestion-related effects, and changes in road geometry, drainage and surrounding development to establish whether current operational loading and structural condition remain compatible with the bridge’s original design basis and any subsequent modifications.
The engineer added that a bridge of this age (23 years) should not be judged on visual appearance alone and a comprehensive assessment should be established.
“Its present load-carrying capacity, actual condition of structural concrete, extent and rate of reinforcement corrosion, loss of reinforcement cross-section where corrosion has occurred, development and severity of structural cracks, concrete strength and uniformity, depth and extent of carbonation, chloride penetration, wherever relevant, concrete cover and reinforcement location, condition of bearings, condition of expansion joints, condition of stay cables, anchorages and associated components, possible loss of prestress or tension in relevant components, excessive deflection or abnormal deformation, foundation and substructure condition, and possible settlement, condition of piers, abutments, retaining structures and deck, drainage and waterproofing deficiencies, present traffic loading against original design assumptions.
The objective is to move from visible deterioration to measured engineering evidence,” the engineer said. The assessment should be led by an independent, technically competent bridge/structural engineering team, supported by appropriately accredited testing facilities, he added.
Sharma said several major bridges and elevated structures across the city have now been in service for decades, while traffic volumes, vehicle weights and environmental exposure have grown substantially. Modern repair and rehabilitation technology offers many options for extending service life, but is only effective when the problem is correctly diagnosed first, he added.
A systematic city-wide programme can identify all major aging bridges, flyovers, Railway Over Bridges and Railway Under Bridges and elevated structures and classify them by age, traffic importance, structural condition, deterioration rate and consequence of failure, prioritising detailed assessment and rehabilitation accordingly. The aim is to shift the prevailing pattern, like complaint-driven temporary repair, to deterioration-based management and another complaint to a structured cycle like inventory inspection, structural analysis, diagnosis, repair and design, rehabilitation, corrosion protection monitoring and periodic reassessment, Sharma said.