Hi Friends,

I try to understand the assumptions of Caesar II for the dynamic seismic analysis with spring hangers. CII has given the examples to analyze the dynamic system with spring hanger. In “Dynamic input and analysis” help file, the assumption is that all the supports move with the defined ground motion and the piping system catches up to the supports. So my understanding is that for the dynamic response, CII assumed all piping system is fixed on the ground or the buildings (no spring hanger) so the piping system has same response spectra. For calculating the piping system stiffness and flexibility, CII uses the spring hanger rates as support stiffness information (both +y and –y directions).

My question is for what kind of spring hanger systems the assumption is accepted? I think if the system only has few hangers, it is OK. But if the system is mainly supported by spring hangers and rod hangers, can we still use this assumption and use CII to do the dynamic analysis? If not, what kind of way is acceptable for the dynamic analysis?

Thanks,