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SOFT Story??

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Hello everyone:

I have shear walls as the only lateral force resisting system in a 10 story RC building.  Separate gravity frames are provided to carry the vertical loads (DL + LL).  The cross-section of the walls remain the same from 1st-5th floor and then it  is reduced to have a smaller cross-section from 6th-10th floor.  The first floor height is 30' while the other floors are only 10' tall.

If I have a taller (30') first story for this structural system, should I expect the structure to have a soft story at the 1st floor level?  

I know that if I had a Special Moment Resisting Frame as my LFRS, then under this circumstance, I would definitely have a softer and a weaker 1st floor.  I have done nonlinear "unit-shear" push-over analysis on these systems to substantiate my results.  

Since the behavior of the shear wall structure will be like a vertical cantilever, I was wondering whether I would have a softer first floor.  

My understanding is that the first floor in case of the shear wall structure will not be a "weak" story as there will be no design shear strength variation across the 1st and 2nd floor level of this structure.  This is because, the design shear strength of the wall is what will govern the lateral story strength of this shear wall structure and not the shear required to develop flexural hinges.   

I will appreciate your comments and or thoughts in this regard.

Thanks very much in advance,


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