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Stiffness modifier for insulation panel in ETABS

Stiffness modifier for insulation panel in ETABS

Stiffness modifier for insulation panel in ETABS

(OP)
Dear All,

If I define the wall as precast sandwich insulation wall panel (max thermal transmittance, U-value of 0.57 W/m2K), what could be the value of stiffness modifier to be specified in ETABS to obtain an actual behavior??

Thank you,

RE: Stiffness modifier for insulation panel in ETABS

Not sure what thermal U-values have to do with the price of eggs in China...

In any case, sounds like you're looking to model 'load distribution panels.' CSI Guidance

Few options here:

1) Use null shells, as per link above.

2) Use a thin shell if you need it to be meshed or a membrane if you don't. Make it say 1mm steel plate. Reduce axial membrane stiffness to 1e-5 so it doesn't contribute to lateral stiffness. You couldn't even back calculate what the equivalent steel plate thickness is to account for the weight of the insulation panel (~0.25 kPa = ~3mm steel plate). Reduce bending stiffness in one direction to simulate one-way load distribution.

RE: Stiffness modifier for insulation panel in ETABS

(OP)
Dear Trenno,

It is a load bearing precast concrete walls that consist of two concrete layers joined by stainless steel connectors with an insulating layer between them. The insulation layer is continuous over the entire surface area.


RE: Stiffness modifier for insulation panel in ETABS

AkshikaS,

For the cross-section that you have added, the stiffness modifiers should resemble the way the structure behaves.

Modifiers I would be thinking something like:

Membrane, mass & weight modifiers no more than 0.75 of modifier that would be applied for a 200thk wall (150mm / 200mm).
Bending modifiers even further as you have two thin panels instead of 1 insitu panel. 0.1 of modifier that would be applied for a 200thk wall. (65^3+85^3)/200^3.

RE: Stiffness modifier for insulation panel in ETABS

(OP)
Dear rscassar,
Why do we calculate like this (65^3+85^3)/200^3.? Could you please explain me?. Thank you.

RE: Stiffness modifier for insulation panel in ETABS

Cause the bending stiffness is calculated depth^3. Cause you have create a 65mm panel and an 85mm panel without any coupling between the two of them, the stiffness is calculated each panel individually.

RE: Stiffness modifier for insulation panel in ETABS

(OP)
Thank you rscassar. :)

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