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# Civil Engineering/calculation of Torsional Irregularity Factors Ax

Question
QUESTION: Good day sir

I am designing a building B+G+14F, Dynamic analysis is being done for the structure,

I need to override the eccentricities for Spectrum Analysis (torsional irregularity)

while calculating the Ax coefficients according to UBC 1997
Ax factor is calculated by equation
Ax = [Dmax / (1.2 Dave)]2

In the above equation displacement values need to considered
from static case "EQXP-EQXN","EQYP-EQYN" or
from SPECTRUM CASES SPECX, SPECY

kindly clarify the dought

Thanks & Regards
Azhar

There is no evidency about this matter but as a matter of fact there is no real difference between the results. But it is obvious that to move to more sophisticated methods need to control results from more general methods then you should tyry with static method.

Regards
beh

---------- FOLLOW-UP ----------

QUESTION: Good day sir

1.
I have done one trial for comparison of the results for a building
i found there is a good difference between the results
from static case EQXP,EQYP &
from SPECTRUM CASES SPECX, SPECY

kindly suggest which values need to considered?

2.
secondly as suggested
"to move to more sophisticated methods need to control results from more general methods then you should try with static method".
so to which methods i need to move/use ?

Thanks & Regards
Azhar Khan

Dear Azhar

The results of static and modal are different but their effect on eccentrencity shall not be because of the same eccentrencity of stiffness and mass centers which are the same for both method.

You should use static method to calculate the random eccentric moments.

Regards
beh

Civil Engineering

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