KARACHI, Sept 19: Yet another overhead bridge among the busiest ones in the city was partially closed to traffic after it developed a huge crater.
The Natha Khan overhead bridge, which has developed a wide crater in its deck flap, appears to be the second bridge in less than a month to have sustained damage, creating scare among motorists and leading general public to believe that bridges and flyovers are not safe.
Similar damage to a section of the Liaquat Flyover earlier this month has led to the closure of a major portion of the main thoroughfare leading to the Super Highway. As the repair work is still under way, the damaged portion of the flyover is closed to traffic for weeks together.
Though the other portion of the Natha Khan bridge has been kept open, clogging has slowed down the traffic on it considerably. It may be pointed out here that the portion which has sustained damage had been built by KDA in the early '90s. The Liaquat Flyover was constructed in April 2001 by M/s National Construction.
Asked about the reasons of craters that are developing in a newly-built bridge or flyover, the Adviser to the City Nazim on technical affairs, Salim Azhar, told Dawn, that the nature of damage in both the cases was same, i.e. a hole in deck flap. He attributed the damage to the movement of heavy vehicles, mainly fully loaded trawlers. He pointed out that such bridges are designed keeping in view model loads.
"Although the designed concrete strength of both the bridges is 3,750 per square inch (PSI) which is standard practice worldwide. The city government has now decided to increase the strength of all the under-construction bridges, such as the Shahrah-i-Quaideen and FTC flyovers, to 5000 PSI mainly because there is no check on the movement of trawlers, long vehicles and other cargo vehicles which often carry the load beyond their own capacity."
In reply to a question whether any other flaws have been observed in the construction of old bridges, he replied in the negative, saying that except for failure of deck flaps in the two flyovers, no flaws had been found as yet in their super structures, foundation, girders, etc.
The city government, on a directive by City Nazim Niamatullah Khan, has already hired the services of engineering consultants for the rehabilitation of all old bridges and flyovers to ensure that such incidents did not happen in future, said Mr Azhar, adding that the consultants were supposed to suggest measures and implement them to make the facilities safe and sound.
Asked how much time will it take to get the Natha Khan bridge crater plugged, he said that a meeting under the chairmanship of city nazim was scheduled for Monday where the matter would be discussed and a decision to this effect taken.
However, DCO Mir Hussain Ali told Dawn that efforts were being made to get the bridge repaired within the next three days. Asked that when would the Liaquat Flyover would fully be reopened to traffic, Mr Azhar said that the concrete filling work had already been completed but it would still take another week to reopen the portion as the concrete had to be dried and properly set to gain strength.
About the report prepared by the city government's monitoring committee on Liaquatabad Flyover, he said that it would also be presented to the city nazim on Monday. The committee, headed by Mr Azhar, has already got done the cubic test of the concrete sample, taken from the damaged portion of the flyover, in order to ascertain the quality of material used in the construction.
