Response Modification Coef.

[MOOK]

If you have 3 story building, Response medication factor for the first floor is R = 5, the second floor R= 4, and the third floor R = 3.

What is the design value of the response modification factor for the first floor?

Some Reference used 4 and the other used 3.

What do you think?

Thanks

 

[McEngr]

If you have 3 story building, Response medication factor for the first floor is R = 5, the second floor R= 4, and the third floor R = 3. What is the design value of the response modification factor for the first floor?

Some Reference used 4 and the other used 3.

What do you think?

Thanks

Hi Mook, ASCE 7 Section 12.2.3.2 states it pretty well. The least R value in that direction shall be used with a few exceptions. I would use 3, but if the 3 conditions are met, you may use the value for each line of resistance. Perhaps one example was a flexible diaphragm with 2 or less stories and the other was a rigid diaphragm? Just playing detective...

 

[MOOK]

Hi McEngr

I hope you doing well

McEngr, actually the point here it is not flexible or rigid diaphragm. The point is if R for certain floor has to be less than any floor above or just less than the direct floor above.

Thanks

 

[McEngr]

Hi McEngrI hope you doing well

McEngr, actually the point here it is not flexible or rigid diaphragm. The point is if R for certain floor has to be less than any floor above or just less than the direct floor above.

Thanks

I believe the answer lies in the section previous to the one I posted: 12.2.3.1 states that no story shall have an R-factor greater than any story above that story, therefore I interpret it as 3. Therefore, you may use 3 for the whole system.

 

[Genuine_Opinion]

If you have 3 story building, Response medication factor for the first floor is R = 5, the second floor R= 4, and the third floor R = 3. What is the design value of the response modification factor for the first floor?

Some Reference used 4 and the other used 3.

What do you think?

Thanks

If upper stories posse more or less the same rigidity as the lower ones, 12.2.3.1 mentions to use the least of all R values we got. (which is 3 in our case).

However, if upper story/stories are flexible compared to the lower ones with two conditions for "two-stage procedure" are met; the portion of structure with upper flexible stories can be analyzed with its R value separately and the end results be amplified with appropriate ratio. These results then be added as reactions for the analysis of the lower portion with its own R value.

This is what I can think of based on the info we have, Mook. Let me know what you think.