Dear Mr. Diehl,

I have a question on the equation given in B31E/ 3.4 Design by Analysis and I kindly ask you to give a personal opinion.

More or less, my question is continuing the old question of Marco posted here.

In B31E equation, M_seismic is the elastically calculated resultant moment amplitude due to seismic load, including inertia and relative anchor motion.
The seismic loading input is to be specified by the engineering design in accordance with the applicable standard (such as ASCE 7) or site-specific seismic.

The question is related to the form of equation that – I think- is based on Allowable Stress Design approach.
If true, I would remark that within ASCE 7 "2.4 Combining Nominal Loads using Allowable Stress Design" there is a factor of 0.7=1/1.4 applied to E= earthquake load. If I understand well, this multiplication by a factor of 0.7 (or dividing by 1.4) is based on the fact that ASCE 7 "E" load is counted for strength level, so the practice is to correct it when count it for ASD method. So ASCE 7 apply a method correction when working with ASD.
Is applying ASME B31E a similar correction?

My doubt is coming up from other references as FEMA 451 chapter 13.4 "analysis of piping systems" which is based also on ASD, where it appears that this correction would be done by dividing Fp (The seismic design force applied in the horizontal direction) by 1.4 and considering the design relative seismic displacement as Dp/1.4Rp where Dp is the relative seismic displacement.

For sure, I have no intention to mix the requirements of FEMA 450/451 with ASME B31E.
However, I can understand the logic of FEMA but I have no idea on how B31E equation has been developed; I just would think that in B31E there is an ASD method (is it?) with a high allowable- that maybe already includes a correction.

Would you please to give your opinion on how B31E equation should be applied ?
Is the B31E intention to apply the seismic loads calculated under ASCE 7 as they are given there- and nothing more?

Thank you.

My best regards.