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How do I retrieve the seismic forces which are in-plane to semi-rigid diaphragms?

ANSWER: To retrieve membrane forces which occur in-plane to semi-rigid diaphragms when user-defined seismic loads are applied to a structure, loads should loads may be directly applied either to floors as distributed loads, or at discrete points according to seismic mass distribution. User-defined seismic loads should not be applied to ETABS  (v9 and v13) automatically distribute the auto wind forces by redistributing wind load to 10 points along the Wind direction for a semi-rigid diaphragm because the software will then concentrate and apply seismic load as a point load only at the center of massmodel. For auto seismic load cases, seismic loads are spread over to every point which has mass so stress concentration can be avoided in a semi-rigid diaphragm model.