Precast U shaped girders to reduce the construction time of metro phase-2 elevated corridor
Posted on: 24/Oct/2019 10:02:13 AM
Sensational piece of news is the time for construction in the metro phase- 2 elevated corridors would be brought down by more than 80 percent.
It is revealed that this reduction in the construction time would be brought out by the installation of precast U shaped girders between the pillars. Information is the use of the girders is being undertaken in the elevated section of the 9 km north Chennai line under construction. By the month of June in 2020, 118.9 km phase-2 would begin.
An official explained the difference between the precast box shaped girders that were used in the construction of phase-1and the ‘U’ shaped precast girders that would be used in phase-2 construction.
The point to be noted is the box girders made of multiple precast segments used in the 45km phase -1 corridor took 4 to 5 days to assemble between the 2 pillars that were 20 m to 25 m apart. He added that ‘U’ shaped precast girders could be assembled in a day.
It is worthy to note that a ‘U’ girder would form an entire span of a viaduct between 2 pillars in a single piece of around 25m in length that would be precast in a casting yard and assembled on site.
On the other hand, box girders have many small precast segments each about 2.5 m long and are assembled together between the 2 pillars. Point is they take more time for construction. The construction costs would be the same and change in the girders would not reduce the cost. This was according to an official.
For cantilever corridors, CMRL also uses I-girder and these would stand on a single row of columns and I-girder would provide support to the concourse and platform levels. Seven of the 9 km is elevated corridor in the phase-1 extension between Washermenpet and Wimco Nagar.
It must be taken into account that in phase-2, 76.3 km of the118.9 km would be elevated and U shaped girders would rest on the pier cup. By the year 2025, 52 km of phase-2 stretch would be ready. It must not be forgotten that the elevated corridors of Delhi, Mumbai and Kochi have U shaped girders. Point is the change in the girder type for the elevated corridors would be advantageous.
It was revealed by a metro rail official that to assemble the girder in phase-1 extension line gantry is being used instead of cranes. He added that except of 300 m rest of the 7 km elevated corridor in north Chennai is ready and how by June 2020 the line would be ready. Important point to be noted is U- girders due to their sizes posed problems during transportation from the yard.
