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nishants.iitk SEFI Member
Joined: 14 Apr 2014 Posts: 2
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Posted: Thu Nov 19, 2020 11:54 am Post subject: IS1893 - Different Response Reduction in X and Y |
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In X direction, we have well distributed Shear Wall system (distributed evenly throughout the length of building). In Y direction however, we have moment frames and walls at central core (so dual system).
Is it ok to take R = 4 in X and R = 5 in Y direction and design and detail accordingly? or is there any challenge? |
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satishkemkar General Sponsor
Joined: 23 Nov 2012 Posts: 38
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Posted: Fri Nov 20, 2020 10:37 am Post subject: |
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If structure false in zone iii iv or v , ductile detailing compusary as per table 9 of IS 1893 note 1. therfore use of responce reduction R =5 is must.
Responce reduction factor depends on the ductility of structure.
if we adopt detailing as per IS 13920 we can use R factor 5
in your case Shear walls will be available in both x and y direction however stiffness of shear walls will be different in both directions.
if you are designing as ordinary frame with shear walls then you can consider as R=4
or
if you are designing special moment resisting frame with shear wall then
R should be 5
in my opinion , both directions you can use same responce reduction factor. |
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md zeeshan ali Progressive Member
Joined: 12 Nov 2013 Posts: 42
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Posted: Fri Nov 20, 2020 3:03 pm Post subject: Different Response in different direction. |
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Dear Sir,
IS Code 1893 don't allow different Response Reduction factor in different direction. Earthquake has no direction defined so better use one response reduction factor.
Best Regards
Zeeshan Ali. |
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pradeep joshiaaa SEFI Member
Joined: 13 Jul 2010 Posts: 16
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Posted: Fri Nov 20, 2020 7:57 pm Post subject: IS1893 - Different Response Reduction in X and Y |
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As per your Query-
Case 1 - X= Direction -Shear wall Domination
Y = Direction - Dual System (Shear Wall - Resist 75 % Design Base Shear & Frame System - Resist 25 % Design Base Shear )
This Means that overall Stiffness is dominated by Stiffer Component Shear wall. Therefore only R= 4 should be used in both Directions.
Incase in Y direction is Non Dual System then relaxation in R can be done.
Regards
Pradeep Joshi
pradeepjoshiaaa@gmail.com |
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sakumar79 ...
Joined: 18 Apr 2008 Posts: 713
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Posted: Sat Dec 19, 2020 11:55 am Post subject: |
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Dear Sir,
Rather than looking at this as what R to use, I think the first question is if such a system is really okay or not. IMHO, it is better not to do shear walls only in one direction. Either you do the building with shear walls in both ways or you go for a SMRF in both directions.
Senior Engineers with experience in earthquake behaviour research are requested to post their thoughts on this more pertinent query.
Yours sincerely
S Arunkumar |
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