Delhi Metro Introduces Girder Launcher With Transporter: How It Will Help

Delhi Metro authorities began the launching work on the Janakpuri West – RK Ashram Marg corridor, which is currently under construction, and introduced a specially designed launcher attached with a transporter for the launch of U-girders on the elevated section. The Delhi Metro Rail Corporation (DMRC) states this as an ''innovation in its construction technology'' used for the first time in the country, and is likely to expedite the pace of construction work on the upcoming corridors of Delhi Metro Phase IV.  (Also Read: Tunneling Drive For Delhi Metro's Janakpuri West-R K Ashram Marg Corridor Started )
 

Why was the use of U-girders challenging for Delhi Metro?

• The installation of U-girders was done with the help of two cranes having a capacity 350/400T which were placed at each pier location, in the earlier phases of construction.
• The U-girders were transported at each pier location with the support of a long trailer with an approximate length of 42 metres. This process was challenging for the metro authorities in the congested urban areas of the national capital.
• This is because the positioning of the heavy capacity cranes occupy a lot of space. Moreover,  transporting the U-girders of 28 metres in length with long trailers was also difficult as the roads in the national capital region usually witness heavy traffic volumes. 
• These limitations would inhibit the use of U-girders in construction activities for Delhi Metro, even though U-girders are the most suitable structures for viaducts in terms of cost and time.
   

How is the new technology of 'Launcher with Transporter' - helpful for construction?

• The new launcher with transporter is fully electric with a higher output, compared to the conventional launchers or cranes. The transporter carries the U-girder from one designated point and moves on the rails laid over the erected U-girders, to add more girders from the feeding point to the launcher.
• As a result of this process, the U-girders are to be transported on the trailer only up to the feeding point identified at a suitable location and not for the entire length of the track. This results in a much less consumption of space. 
• The new launcher is 62 metre long having a total weight of 230T, according to Delhi Metro. It can negotiate gradients up to four per cent and 200 metre radius curves. Whereas, the transporter which transports the girder is 41.75 metre long having a total weight of 35T, which can travel with a speed of three km per hour at no load and at two km per hour at full load. 
• The output of the new technology is higher as compared to the conventional method of the launching of U-girders. On average, four-to-six U-girders per day can be erected with the new launcher, whereas, with the conventional method, around two U-girders could be done in congested spaces of Delhi or other areas in the national capital region.
• Moreover, the erection work of U-girders with the conventional cranes could only be done during night hours as it requires the blocking of roads to position the cranes. Whereas, with the new launcher, the girders are transported with the transporter over the erected viaduct without any interface with the road from a single identified feeding point.

The launcher was made operational on Monday, July 5, for the construction of a 9.5 kilometre long viaduct from Mukarba Chowk to Ashok Vihar covering four metro stations - Majlis Park, Bhalswa, Azadpur, and Ashok Vihar, and a connection to the depot from Majlis Park.