how to achieve 25% Rule for Dual System with SMRF?

[xnyzhangshulu]

For Dual System with RC shear wall and RC frame, ASCE7 code requires the story shear be distributed to the shear walls and moment frames in proportion to their relative rigidities, but still moment frames shall be designed to no less than 25%. How to achieve this in ETABS?

 

[ASCE07]

Step 1) Delete your shear walls and save this model as a separate file. Multiply your rho with four.(rhox4), this will reduce your Cs to 25% of the original. Proportion your moment frame for this 25% of total base shear.

Step 2) Now in your original model use these sizes as minimum. And run the model with regular rho value.

you are done!

 

[xnyzhangshulu]

hi, ASCE07
Thanks for your comments.
For the step 1, I have the following doubt. If a beam was supported by the shear walls, the beam will become unstatic once the shear walls were deleted. How to deal with this question?