Ground Level
The Criteria - Ground Level command is used to explicitly state the story at which the ground level meets the structure. The default is the base of the structure but with this command but the ground level can be set to any story except the top most story.
To select a story other than the base, select the At Story Level option and select the story from the drop-down list.
To return to the default (the base) of the structure, select the At Base option.
Note: If a story level is specified as the ground level, diaphragms at that story and all diaphragms at all stories below are "locked" against lateral translation and rotation. Also, only nodes attached to diaphragms at these stories are restrained and nodes not attached to any of these diaphragms are not restrained.
Click the OK button to affirm the changes made. Click Cancel to return to the settings as they existed prior to making changes.