For high rise builldings in Bangalore, are higher floors riskier in the event of an earthquake ?

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	For high rise builldings in Bangalore, are higher floors riskier in the event of an earthquake ? Asked by : Ram Sharma, Software Developer, Infosys Technologies Functional Area : Infrastructure Keywords : earthquake high rise buildings structural safety Activity: Question posted: 10 18 2009 08:27:45 +0000, 2 answers, 1225 views, last activity 07 06 2010 20:18:08 +0000	Answer

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I am planning to purchase an apartment on the 14th storey of a 19-storeyed residential building from one of the leading construction companies in Bangalore. I chose a higher floor because it can provide more air, light and less pollution. However I have some concerns regarding the structural safety of the building, in particular the seismic safety. I have 2 particular questions in this regard:

1) I would like to know if higher floors are riskier in the event of any earthquake. My limited understanding on this matter says that the threat to life and property due to earthquakes is same at all the floors in a high rise building, unless the soil undergoes liquefaction (in which case the building may topple and the higher floors will bear the brunt of the collapse). I have verified that the soil at the site of the proposed building is safe against liquefaction. So I think there should not be any reason for me to sacrifice the advantages of living on higher floors.

Please advise if I am wrong.

2) The Builders declare that their high rise structure complies with the building code for Zone II, and that the building can withstand tremours upto scale 5 (richter scale).

Given this I would like to know if Zone II compliance (bangalore falls in zone II) guarantees that the building will not collapse in the event of an MCE (maximum credible earthquake). In particular I would like to know:

-- What maximum magnitude of tremour will the building withstand without significant damage and continue to be habitable.

-- At what earthquake magnitude will the building be damaged so that it is not safe to be inhabited further.

-- At what magnitude will the building collapse completely.

-- Is the building is likely to collapse in case Bangalore experiences tremours of magnitude 6.3 ?

I would appreciate if any expert in civil / structural engg. could help me with my queries.

Thanks and Regards

Rams

If properly designed, I don't think that high rise building would be risky. However there are three things to be observed. First if this high rise building has car parking facilities in the ground floor supported by columns only then the design of column must be compatible to withstand the earth quack. In Gujurat most of the high rise building collapsed due to inadequate design of such columns.

Secondly, I was bit worried by the fact that the building is designed as per Zone-II as Bangalore falls under Zone-II category. Many designers prefer to design one category ahead of the zone the area falls. Ideally such a high rise building should be compatible with Zone-III specifications.

Third & important one is quality of workmanship.Many buildings fails due to sub-standard workmanship despite a robust design & constructed by big companies. Real estate sector is yet to follow a strict quality control system. There are very few company who adhers to quality control & rest other focus on speedy construction at the cost ofquality.

It is really hard to say which magnitude is fatal & which soil condition is more damaging. The hard & robust soil base may induce huge vibrations compared to soft soils. In such a case a smaller magnitude would build cracks & building may collapse.On the other hand soft soil may absorb much of shocks & may result in to settlement only allowing time to escape.

The building reffered is 19 stories. I donot know whether thisis built on concrete pillers. If it is a framed RCC structure surely I would find my self uncomfortable. I would suggest buildings more than ten floor must be a steel structure to withstand earth quack & wind pressure. However many high rise buildings have survived bt many too collapsed.

I would have an honest suggestion. If your planning for apartments,do not chose Buildings more than six floor if it is a RCC framed structure. If you can afford go for simplex or duplex houses. The steel structure buildings are entering in to India & perhaps started in Mumbai. In Bangalore this technology will reach with in ten years. Then you can fulfill your dream to live high. You can chose even 100th floor as I always belive that these are much safer.

However the above is my personal opinion.

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by Biranchi Narayan Acharya, Chief Manager (Projects), Simplex Infrastructures Ltd | 10 19 2009 13:17:44 +0000

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2 Answers for "For high rise builldings in Bangalore, are higher floors riskier in the event of an earthquake ?"

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Answered by Ram Sharma, Software Developer, Infosys Technologies | 10 19 2009 16:06:41 +0000

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