PT Slab Property Modifier

[benjaman]

What Slab property modifier do you guys use for PT slab modelling in ETABS, note model will be for lateral analysis, not slab design.

Thanks

 

[rscassar]

The stiffness modifier that best represents the behavior of the slab element. Thin slabs up to 250thk generally F11,F22,F12,M11,M22,M12 = 0.25 to 0.35. As the slab get's thicker this number would get up to 0.5 to 0.7

 

[Agent666]

F11/F22/F12 are the in-plane axial and shear stiffness, I wouldn't be reducing those for a slab intended to act as a diaphragm under a lateral analysis?

You'd only typically reduce the flexural properties to suit whatever your effective cracked stiffness was if you were trying to capture the shell stiffness contributing under lateral load cases. Typically, though I'd usually just use a "membrane" shell element type and just rely on the lateral system provided to carry all of the lateral load.

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