Dear Dave or other experts,
I need to have a better understanding and explanation on how Caesar calculates the stress for Pseudo-static component at node 40 in the attached picture. Does Caesar somewhat consider the maximum relative displacements (i.e 20” between STR 1 and 2) in stress calculation?

I’m using Spectrum method. To simplify the case, I assumed that the cut off frequency is 1 Hz so that the pipe has only one mode of vibration in the analysis. I also assumed that the friction is 0 so the pipe can slide. I’m not interested in explanation for method of modes combination, dynamic/static load combination, or the amount of mass included etc.

Thanks in advance,

I assume you are entering that 10 inches as the seismic anchor motion (ASM) for shocks 1 & 2 and zero for the ground shock.
In addition to the inertial component, the program will calculate the response to each individual ASM and then sum these individual ASM responses according to your Control Parameter settings - either absolute or SRSS.
Your node 40 will see a Shock1 ASM component and a Shock2 ASM component (with the anchor at 60, I believe there will be no response from the Ground Shock). But the ASM will be a combination of (10" at 10 with 0" at 60) and (10" at 60 with 0" at 10). To that, add the inertial component to get your total response.