hi all,

currently I am working on a sigle line piping system connecting two equipments. I am checking the seismic effects on that system and I am facing a problem i do not know how to sort out; once I check the "included mass data" I see that in some cases there is a 42% added force to my system I increase the frequency cut off to 800HZ and the percentage falls into 11% and remains the same value even for higher frequency cut offs. the highest stresses are still on a psuedo case.
I really do not know how to deal with this situation. i wonder if anyone could give me a useful suggestion.

Regards
pooria1978

What's the highest stress component - pseudostatic or missing mass? These are different. The pseudostatic component is caused by differential deflections. This would indicate you do not have the same shock spectrum for all of yoru system. Check you system displacements at your support points.

thanks for your reply,

the highest stress component is pseudostatic. my system comprises a piping line sitting on a steel frame ( Y and Lim are Cnode to the frame), I made sure that the start node of the spectrum was the start node of the input and I left the other cells blank so I think all of my system is under the same shock wave but I still get the insane results.