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# Civil Engineering/Effective Stiffness (Base Isolation)

Question
QUESTION: Dear Sir,

From what i know, the "effective stiffness" for Base Isolation is determined from Hysteresis Loop. Where can I find Hysteresis Loop curve in ETABS 2013? I'm using Response Spectrum Curve analysis base on EUROCODE 8 standard, in which the curve is already defined in the system. Thanks.

Regards,
JV

You should use a secant stiffness according to the hysteresis loop of the base isolation system. For Rubber bearing base isolation the stiffness is related to thickness of the base isolation device and elasticity properties of the rubber. There are no specified hysteresis for this matter. There are not like steel and cement and material like these. Their characteristics come from tests. Each company has its own product which is tested and documented. You can find instances in the Internet.

Regards
BEH

---------- FOLLOW-UP ----------

Base Isolation Propert
QUESTION: Dear Sir,

Thank you for your reply. It makes me more understand. By the way, how to determine the "effective stiffness, keff" based on the image attached below? Can it be related to the Yield Stiffness or Compression Stiffness? Thank you Sir.

Regards,
JV

Dear Jv

The table cant be read but you should essentially calculate the lateral stiffness of the device based on shear stiffness of the rubber layers.

Regards
BEH

Civil Engineering

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