Distribution of Lateral Forces of each floor 2

[pete600]

In determining the lateral distribution of seismic forces on each floor, do you recalculate the relative rigidities of each @ each floor?

Thanks in advance

"God grant me the serenity, to accept the things I cannot change, the courage to change the things I can, and the wisdom to know the difference" -Reinhold Niebuhr

 

[pete600]

To be more specific if I am using a 1 kip dummy load, would I apply that dummy load to a braced frame or moment frame at each floor to determine a floor specific rigidity?



"God grant me the serenity, to accept the things I cannot change, the courage to change the things I can, and the wisdom to know the difference" -Reinhold Niebuhr

 

[jike]

I recommend doing a 3D analysis rather than 2D (unless floors are identical).

 

[bobby83]

In theory, I would say the answer is yes. The flexure/shear component of the stiffness changes with the slenderness of the frames. However, if the building is very simple and regular, it is safe to assume that the relative stiffnesses is constant for every floor.

 

[KootK]

I would also say that the answer is yes. Moreover, the updated rigidity distribution impacts not just the distribution of seismic load applied to the floor bing considered but also triggers a redistribution of any story shear coming in from above. Computers and approximations are both great ways to expedite the work.

I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.

 

[pete600]

Thanks for the responses.

"God grant me the serenity, to accept the things I cannot change, the courage to change the things I can, and the wisdom to know the difference" -Reinhold Niebuhr