Metro viaduct flaw: Repair work to last 10 days, cause morning delays

BENGALURU: Namma Metro commuters faced delays on the Purple Line for a second successive day on Thursday, after a delay in repair work on a ‘honeycomb concreting defect’ in the viaduct near Trinity Station.
A Bangalore Metro Rail Corporation Ltd (BMRCL) spokesperson said services between MG Road and Byappanahalli were affected from 5am to 7am due to the repair work near Trinity Station.However, operations were unaffected on the line between MG Road and Mysore Road. The delay was less severe than on Thursday, when operations were restored only at 10.20am.

BMRCL is carrying out repairs on the honeycomb formation in the viaduct above pier No. 155 on the Purple Line after operations halt at 11pm. The system operator has put up metal pillars adjacent to the pier to shore up the viaduct.

Alignment hitch?
Honeycombing is a relatively common defect in reinforced cement concrete (RCC) structures, but it emerged on Thursday that there could be another, albeit not yet major, problem in the line at the spot. BMRCL spokesperson BL Yeshwanth Chavan said the work would take around 10 days to complete because it has to be carried out at a height of more than 12m from ground level, with temporary supports and a platform for work around the pier. “After mapping the strength of the concrete, we will have to rectify a minor aberration in girder alignment by replacing bearings and strengthening the cross-beam,” he said. The girder alignment aberration, experts warned, could lead to “serious distress” is it is not corrected. “This means that the pre-stressed girders may not be properly seated on the bearings or the bearings may not be functioning properly,” said Prof JM Chandra Kishen of the department of civil engineering, Indian Institute of Science. “If this is not rectified it may lead to serious [structural] distress.”
BMRCL to suspend operations on the Purple Line on December 22-23 for extended hours?
Though BMRCL officials maintained that there was no threat to the structure, they continued to operate trains at less than 20kmph, instead of the normal 45kmph, near Trinity Station. “We are working overnight to complete repair work in a phased manner,” BMRCL managing director Ajay Seth said. “The first phase of the work is likely to be completed before 5am on Friday but there may be some morning disruptions if it is delayed. Services will be normal from Saturday.” He said they are also considering suspension of operations MG Road and Byappanahalli on the Purple Line for a long duration on the weekend of December 22-23 to carry out major, final repair work. “It will be difficult to complete repairs only during nonoperational hours so we may have to impose longer blocks during the weekends for major work,” Seth said. “We are charting out a minute-to minute plan.” “There is nothing to worry about the safety of the structure,” he said. “This honeycombing is an isolated case. We are carrying out the repairs in consultation with experts.”
Navayuga Engineering Company Ltd started work on the section between Baiyappanahalli and MG Road in 2007 and the stretch became operational in 2011. The defect liability period is only for two years, officials said, so the company cannot be held accountable for any structural flaw.
Machines stuck in traffic
BMRCL, which detected the structural flaw in one of the viaducts near Trinity Station on the Purple Line on Sunday night, more than two days before Wednesday’s scare, planned to complete repairs before services started on Wednesday morning. The work was delayed after machinery got stuck in traffic snarls on the way to the spot near Trinity Station from KR Puram and Mahadevapura. “Construction trailers and other machinery were bought from construction firm ITD Cementation India, which is building the Baiyappanahalli-Whitefield stretch, but it was held up in traffic,” BMRCL MD Ajay Seth said. “This delayed the work.” ITD Cementation India is also carrying out the initial repair work.
Ridership dips by 9K
There was a slight decline in the number of passengers on the Purple Line on Wednesday after messages on social media about glitch in the viaduct near Trinity Station stoked safety fears. BMRCL officials said Metro’s ridership on the line declined to 2,02,000 on Wednesday from 2,11,000 on Tuesday — a drop of 9,000 passengers. BMRCL spokesperson BL Yeshwanth Chavan said the slight reduction in passengers was mainly due to cancellation of services on Wednesday morning. “Normally, we operate 66 trips and 11 short loop trips between 5am and 11am,” he said. “During the same period on Wednesday we operated 46 trips and 22 short loop services.” Stating that safety of the passengers would remain top priority for BMRCL, Chavan said the affected portion was small and would not compromise overall structural safety.