Seismic loads application B31.1

Dear all!!

According to ASME B31.1,section 104.8.2, when calculating stresses due to earthquake "only one half the earthquake moment range" must be used. What does it mean? To use only one half of the seismic load? Or does it refer to the fact that the earthquake is a cycling load, so it produces moments, i.e, from -30 to +30 and designer must use 30? Or the designer should use, when calculating stresses, one half of the moment, that is to say 30/2 = 15?
When entering seismic load in CAESAR, must it be the full load or one half of it?

As you see I find that paragraph very confusing.

Best regards and thanks in advance

Your seismic analysis, whether static g or response spectrum, produces results that can be considered amplitude. So a moment at a node, if listed as 100, should be read a +/- 100. One half of the moment range (quoting 104.8.2) gets you back to the original amplitude (100 in this case).

At this time, seimic loads are considered primary and the mode of failure due to seismic load is yield, not fatigue. That's why you use amplitude rather than range.

I see no reason to divide anything by two in CAESAR II - input or output.