Autodesk Robot Structural Analysis

[#1]

Ive run two seismic analysis under Eurocode 8 ; the first one with behaviour coeff = 3.90 and the second with behaviuour coefficient = 1.00 ; ive got slitly the same results in term of displacement at the stories table.

so , Please confirm that the displacement calculated at the stories table are the elastic one , and they should be multiplied by the behaviour coefficent in order to the obtain the correct ones when doing seismic analysis ( with behaviour coefficient greater than 1.00)

In advance Thank you.

[#2 · Accepted solution]

Displacements in EC8 are in case of design spectrum already multiplied by behaviour coefficient q.

In case of T>TB it results (independently from q value) in displacements equal to displacements from elastic spectrum.

If some vibration modes with significant mass participation are observed for T<TB it may result in slight differences of displacements depending on q value - as it the screen captures attached to your post.

This effect results from comparison of analogous branches of elastic (formula (3.2)) and design (formula (3.13)) spectrum - the difference between them is more than just division by q, as in other branches of spectra.

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[#3]

Hi pp2008,

regarding "Displacements in EC8 are in case of design spectrum already multiplied by behaviour coefficient q."

This is a valid statement only for stories tables or also to nodal displacements table and diagrams for bars (deformation) ?

Thanks.

[#4]

 RRufino:

This is a valid statement only for stories tables or also to nodal displacements table and diagrams for bars (deformation) ?

Yes, it is a valid statement also for nodal displacements and diagrams for bars.

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Regards,