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Service Life of Elevated Metro
Written By blrsri - 9 October, 2009
Bangalore Analysis Transportation Infrastructure Flyovers and underpasses
There have been numerous debates on wether we take metro underground or do we have it on elevated structures..these have been mostly related to the following:
1. Number of tree cut and properties damaged
2. Cost of going underground
The first is not anymore a point of discussion as BMRCL has proved that equal/more number of trees will be cut for going underground.
The second point on cost is valid because the claim is going underground escalates the cost by 3 times.
However, there is a third point on the life of elevated structures itself..
There are many references on google that the 'service life' of concrete bridges is about 75 years maximum..so does that mean the metro will be functional only for the next 75 years?
Is it because of this reason most metros around the world just go underground?
Parts of Red line in Boston was constructed in 1912 and they have extended since then..most of the line is underground with some part at grade..
So wouldnt it make more sense that we go underground for most parts of namma metro now, though its gonna cost us more?
COMMENTS
blrsri - 17 October, 2009 - 16:10
..and we may not be in a position to afford underground now..lets see if our future generations can do any better!
Elevated Metro - Can be maintained
Naveen - 10 October, 2009 - 00:46
Blrsri,
With a U/G metro, trees can be replanted once construction is over + we will not have ugly viaducts obstructing the skyline everywhere. The only problem is that U/G construction costs are very high.
It does not necessarily mean that Namma Metro will only last about 75 years since much of it is above the ground.
Viaducts can be maintained for very long periods - the bridges in New York across Manhattan & other boroughs (such as Brooklyn bridge) are very old & are being maintained by periodic replacement of weaker sections & corrosion resistant coating, etc.
Metros in many cities across the world are U/G since they could afford them so, I guess ! Also, perhaps, to retain open spaces & road widths. In New York, the "subway" is elevated in many areas outside Manhattan (Brooklyn, Queens, Bronx, etc.). In Washington DC also, the Metro surfaces from below ground & even runs elevated in some parts. Similarly, the Path system in NJ is U/G, but also has sections that are on surface - so, it's all usually dependent on the terrain, finances, projections & needs as decided at the time of construction that finally results in the outcome, I guess.
Even the "Underground" in London has a lot of it that is not below the ground, as do the Metros in Berlin, Munich or Singapore.
I agree that UG is the best - but the costs are too high for Indian cities in our current economic situation - since there are many other priorities that also need to be attended to.
Service Life of Elevated Metro - Same as Underground tunnels
gopi - 10 October, 2009 - 16:46
Most of the cities has U/G in CBD and surfaces above once the network is out of the CBD. This I think will help since the metro can take any route, without the constraints of the existing road network.
Regarding the life of UG or above ground the materials used for construction is still concrete and steel. The difference might be that the tunnel will have to deal with the chemicals in the soil and the water, where as viaduct's should deal with weather. There should not be any difference in the life time of the structures.
advantages of ug metro over elevated metro
ssheragu - 11 October, 2009 - 14:48
ssheragu
I have done some loud thinking on the benefits of UG metro over ELEVATED metro; these are given below.
BENEFITS / Advantages of Underground Metro over Overhead Metro
1. Space requirement: construction of overhead metro requires a lot more space than construction of an underground metro;
2. Demolition of structures it required demolishing a lot more structures than underground metro;
3. Loss due to Traffic snarls: the losses it creates by way of traffic snarls is much more than that for underground metro;
4. Traffic Deviations: inconvenience due to traffic jams are much more than that for underground metro
5. Aesthetics: there is no comparison in aesthetics between underground metro and overhead metro; an underground metro is much more colorful, neat and orderly than an overhead metro; thus its revenue generation by way of tourism is much more than that of an overhead metro
6. Cost Factor: since the life of any city is practically without any bound, no cost will be too big for any city; plus the cost of UG underground can be recovered in 10 or 15 years time
7. Moreover, the metro can be planned in such a way, that, if there are a total of 10 lines in the metro, only 2 lines can be completely elevated; the rest 8 lines can be completely underground.
AT ANY RATE IT IS NOT AT ALL ADVISABLE TO HAVE PART OF A LINE ELEVATED AND THE REST OF THE LINE UNDERGROUND
many thanks
Srinath Heragu
ssheragu - 17 October, 2009 - 05:03
ssheragu
Happy Diwali to all of Praja
blpraj, you have given a good critical analyses of elevated versus ug metro; it makes it quite evident that a meeting with Sivasailam is absolutely necessary at the earliest;
considering our interest in metro, I would be happy to arrange a meeting with Sivasailam, if someone can provide his conatct nos. (I had earlier, but I have misplaced)
many thanks
Srinath Heragu
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