Stiffness Reduction for Walls
Stiffness Reduction for Walls
(OP)
Hi Guys,
I am sure most of us here are familiar with the stiffness modification factor stipulated in ACI 318-14.
For beams and columns, the application of stiffness modifiers can be easily incorporated into ETABS analysis by modifying the respective moment of inertia.
My question here is how can we correctly apply stiffness modification for walls. As per CSI Wiki Page, it basically says that we modify f11=f22=0.70 for uncracked wall.
I am a bit skeptical with CSI recommendations. The reduction of f11 and f22 also indirectly corresponds to a reduction in axial stiffness of the wall. This contradicts ACI 318 recommendations that there should be no modifications to gross cross-sectional area.
I am wondering how do you guys approach this. Do you just use CSI recommendations of reducing f11 and f22?
I am sure most of us here are familiar with the stiffness modification factor stipulated in ACI 318-14.
For beams and columns, the application of stiffness modifiers can be easily incorporated into ETABS analysis by modifying the respective moment of inertia.
My question here is how can we correctly apply stiffness modification for walls. As per CSI Wiki Page, it basically says that we modify f11=f22=0.70 for uncracked wall.
I am a bit skeptical with CSI recommendations. The reduction of f11 and f22 also indirectly corresponds to a reduction in axial stiffness of the wall. This contradicts ACI 318 recommendations that there should be no modifications to gross cross-sectional area.
I am wondering how do you guys approach this. Do you just use CSI recommendations of reducing f11 and f22?





RE: Stiffness Reduction for Walls
I typically start by modifying the stiffness in f11 and f22. If there is significant axial loads on the walls, I will consider going back and double checking the local axis and changing the modifier in the axial direction back to 1.
RE: Stiffness Reduction for Walls