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[siempu.rahul31]

Hi,
We know that Response Reduction factor 'R' is damage by engineering, we take R=3 for concrete & R=5 for steel, What happens if we take R =4 or 5 for concrete.

[maulesh]

Dear ER,

Response reduction factor is measure of ductility of structural system. If we take higher R value then we have lesser seismic force by considering higher ductility.

We have to careful while selecting R value for particular structural system. We can take R as 5 but we have to make sure such level of ductility will achieve vide detailing (junction/confin renf)....etc....

Thanks
Maulesh

[Manoharbs_eq]

Response reduction factor for different type of buildings is different.

R=3 for OMRF
R=5 for SMRF
R=4 for steel frame with con brace
R=5 for steel frame with ecc brace etc.,,


Kindly go through IS1893-part1 and part 4 for values.


RGDS
Manohar

[gpsarathyy]

Dear Sefian,

We can consider R= 5 for concrete structure, provided we are following ductile detailing as per 13920.

Regards,
G.Parthasarathy

[Dr. N. Subramanian]

Dear Er Rahul,

You can not take Response Reduction factor 'R', arbitrarily. They are based on statistical studies. Response Reduction factors are related to the ductility of the structures (read the excellent book authored by Paulay,T. and Priestley, M.J.N. Seismic Design of RC and Masonry Structures, John Wiley, 1992, 744 pp.). If a structure is more ductile, we can take greater R value. Thus R value is more for steel (more ductile) and less for  concrete (less ductile). Also concrete structures with ductile detailing is assigned greater R than concrete structures with no ductile detailing.

Read also the enclosed paper


Best wishes,
NS

[Yogesh.Pisal]

Dear Er Rahul,

Different "R" values are proposed by different codes. Variation is mainly due to the assumptions / considerations while proposing the value of "R".

e.g. If you see ASCE then you will find higher value of R, but these values include damping also (as they do not have different damping for different materials).

Hence, if you are designing the building using IS456 / IS13920 then you can refer the "R" as proposed by IS1893 Part 1 & 4. Further, if you are designing by IS800:2007 then you can follow the "R" proposed by Chapter 12.

Regards,
Yogesh Pisal