Concrete Shear Wall Building

[Ice82]

Hi all

I'm modeling a 3 storey building which has shear walls resisting lateral load and the floors are pt slabs and composite beam - metal deck system.

So I'm using SAP 2000. I started off modeling only the elements that I was using to resist the lateral loads i.e. the shear walls as well as a concrete slab on each floor with appropriate thickness. The model was only meant for lateral analysis so I believed I could leave out columns and beams that are only used for transferring vertical loads.

But now I find that all 12 modes are out of plane bending of my slabs. Am I mistaken and should I include columns and steel beams in my model? I thought they would make my building stiffner and should be thought as secondary elements.

Well, maybe someone can give me some advice on the topic.

cheers.

 

[Stazz]

I know in Risa-3d there is an option to define diaphragms as "In plane bending only". Is there an option in SAP 2000 for this? If not, try releasing the out of plane forces on the plate elements - Mx, My and keep only the shears Vx, Vy.

I thought the standard practice was to assume a rigid diagragm for these slabs. If the shear wall orientations in your building is irregular then you might need to model the slabs stiffness but if there is symetry then it might be ok to model the floors as rigid.

 

[TamerArafat]

i didn't understand,

why wouldn't you use all the structure as a frame, it will reduce the steel and concrete quantities and stresses in the building, and will provide with extra rigidity against earthquakes and winds.