25% Rule for Dual System with SMF

[xnyzhangshulu]

Please help me to comprehend ASCE7-05 section 12.2, "Dual System with Special Moment Frames capable of resisting at least 25% of prescribled seismic forces". It's unclear that each floor of SMF shall resist 25% of base shear or story shear forces. How to define the "prescribled seismic forces"?
BTW, for dual system with special RC shear wall and RC frame, how to achieve this in ETABS?
Thanks in advance!

One conference proceeding paper, Earthquake-Resisting Dual Systems and the 25% Rule by Jon D. Magnusson maybe helpful. But I can't download it. Can anybody help me?

 

[slickdeals]

25% of the story forces.

 

[whyun]

Older codes simply required 100% of the story shear taken by the concrete walls and 25% of that into the moment frames. Newer codes require 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%.

 

[xnyzhangshulu]

Hi, slickdeals.
Thanks for your answer. Do you have any papers or books to prove the "25% of the story forces"?