IS 1893 code query

The query below pertains to Indian seismic code. Your opinion is requested in the matter enumerated below. Most of my work experience has been gained while working with American earthquake codes ( ASCE-7, UBC ,CBC ) and therefore that is the perspective I carry while reading the Indian code and therefore a need to seek opinion.
The way the American codes have been formulated it is clear that the earthquake forces as calculated from the codes are at strength level and accordingly the code recommends a factor of 0.7 ( 1/1.4) for load combinations at service level for earthquake forces ie if a comparison of wind and EQ shear is to be done then the EQ base shear as calculated from code should be multiplied by a factor of 0.7 . ( reference section 2.3 and 2.4 of ASCE-7-05 )
In my reading of IS 1893-Part 1 2002 ( I admit that my experience with Indian code is very limited ) it appears that the way the earthquake force is calculated based on seismic zone factor which in turn is related to effective peak ground acceleration- and the force so obtained is reduced by response modification factor R . The earthquake force so obtained has to be a strength level force unless Indian code writers have included a factor ( either in seismic zone factors or R values or ½ factor used in formula given in section 6.4.2 of IS 1893 2002 ) to bring it down to service level.
The load combinations in IS 875 /IS800 or IS 456 basically treat both earthquake and wind at service level

Request to clarify if EQ force as calculated by IS 1893 is to be treated at service level or at strength level.


#1 submitted by admin on Fri, 12/09/2011 - 09:20

Please post this in general forum to get answer from community.