Cantilever Rigid Diaphragm
Cantilever Rigid Diaphragm
(OP)
Hi fellow Eng-Tippers,
Please refer to the attachment. I have a structure where the concrete shear walls are not symmetrically located in one direction, creating a 'cantilever' diaphragm (Gridline 1 to Gridline 2).
Would you break the slab into two areas (when determining center of rigidity, center of mass) and design accordingly or would you design as one slab (despite having only a 'sliver' of slab between the two main cores?) What special considerations are there? Your thoughts and concerns?
Thank you.
Please refer to the attachment. I have a structure where the concrete shear walls are not symmetrically located in one direction, creating a 'cantilever' diaphragm (Gridline 1 to Gridline 2).
Would you break the slab into two areas (when determining center of rigidity, center of mass) and design accordingly or would you design as one slab (despite having only a 'sliver' of slab between the two main cores?) What special considerations are there? Your thoughts and concerns?
Thank you.






RE: Cantilever Rigid Diaphragm
Mike McCann
MMC Engineering
RE: Cantilever Rigid Diaphragm
I would definitely treat it as one slab.
RE: Cantilever Rigid Diaphragm
Mike McCann
MMC Engineering
RE: Cantilever Rigid Diaphragm
Mike McCann
MMC Engineering
RE: Cantilever Rigid Diaphragm
BA
RE: Cantilever Rigid Diaphragm
I can't imagine how the entire slab (from Grid 1 to Grid 3) can act as one rigid body given the thin sliver of slab between the main cores. If I were to treat slab between Grid 1 and Grid 2 as a separate diaphragm cantilever, I would get much higher forces on the walls due to eccentricity. Your thoughts?
RE: Cantilever Rigid Diaphragm
Just analyze the diaphragm as a propped cantilever, with the left side of the big cores being a roller and the small core at the right side being a pin. The simplified model is thus determinate, and you get a big reaction at the roller, which makes the shear through the narrow slab section small.
RE: Cantilever Rigid Diaphragm
BA
RE: Cantilever Rigid Diaphragm
RE: Cantilever Rigid Diaphragm
BA
RE: Cantilever Rigid Diaphragm
Perhaps GalileoG can enlighten us as to what type structure this represents. If it is a mezzannine slab in the atrium of a high rise, perhaps this level can be bypassed in the lateral load model.