Is there any value to inputting negative and positive seismic anchor movements in all four directions (X for S1, -X for S2, Z for S3, -Z for S4) or is having two positive orthogonal directions (just X and Z) sufficient to calculate SAM loads? Does the negative value ever change any results or is it even necessary?
Also, since seismic differential displacement is a displacement stress (not occasional). Why does Autopipe compare SAM stresses to the occasional stress allowable and not the expansion stress allowable. The code is ambiguous on this topic, and I want to know Bentley's thought process for having SAM stresses compared to the occasional allowable.