Dear Members,

While performing Modal Analysis, we came to have one query as below, request to look once & help us.

Bases on Piping Code 31.3, for Stress & force calculations in Static Analysis, the Modulus of Elasticity at Cold Temp (EC) shall to use. NOT EH at OPE/ DESIGN TEMP.

1) Can this EC / EH affect to Natural Frequency in Dynamic Analysis?

2) After Static Analysis, save the file as Dynamic & IF we change from EC to EH at OPE temp,since,in Modal analysis user has to check the LNF(Low Natural Frequency) of Piping system output, here in Modal analysis, no external forces are to be considered like same as time history & spectrum analysis.

As per my knowledge, Modal analysis is based on distribution of Masses of Piping (Concentrated, Insulation, Fluid Density) thru proper supporting & fine breakdown of piping via additional nodes only.

So, question is whether we can use EH at( Hot Design / OPE)case where LNF need to check based on project specification for MODAL ANALYSIS?

We tried here to check, the output LNF at EH (elastic modulus at high temp) is lower than the use of EC (elastic modulus at Cold temp)

Is this correct approach or my understanding is not correct?

Hope to have your experts thoughts for this query.

Regards
SND