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IS1893 - Different Response Reduction in X and Y

 
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nishants.iitk
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PostPosted: Thu Nov 19, 2020 11:54 am    Post subject: IS1893 - Different Response Reduction in X and Y Reply with quote

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
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Joined: 23 Nov 2012
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PostPosted: Fri Nov 20, 2020 10:37 am    Post subject: Reply with quote

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
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PostPosted: Fri Nov 20, 2020 3:03 pm    Post subject: Different Response in different direction. Reply with quote

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
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PostPosted: Fri Nov 20, 2020 7:57 pm    Post subject: IS1893 - Different Response Reduction in X and Y Reply with quote

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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