Reactions direction in seismic result

[m_zaman]

Hi 

I have some problems with reaction direction in seismic analysis.

In reaction table I can't see the uplift force( minus force).

Could you please help me to understand how can I consider uplift?

[Pawel.Pulak · Accepted solution]

Hi,

in case of seismic analysis using response spectra method results are given for qudratic combinations. When calculating quadratic combinations (square root of the sum of squares or more advanced types like CQC) the information about sign is lost. It is what is seen on your screen capture.

In Robot this information can be restored specifying main mode - see the attached screen capture. In such case quadratic combinations of results are multiplied by the sign of appropriate result for selected vibration mode (the main or dominating one).

In case of default settings of job preferences (results for quadratic combinations saved inside a project) it is necessary to re-run analysis after setting the main mode.

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