A. To check for inter-story drift
To instruct the program to check the drift between adjacent stories against a code-defined ratio, use the following procedure.
Story drift is calculated as the relative horizontal displacement of two adjacent floors in a building. Inter-story drift can also be expressed as some factor times the story height. The allowable factor generally varies from one country code to another and may also vary depending on the type of loading. For example, in IS 1893: 2002 for seismic loading the allowable limit for inter-story drift is 0.004 times the story height whereas in IS 875 for wind loading it is 0.002 times the story height.
The drift at a particular story level in either lateral direction is calculated as the average of all the joint displacements present in that floor level. However if floor diaphragm is present, the drift is calculated at the center of mass (i.e,. master joint) of the floor.
Post Analysis Commands tool in the
Analysis Data group on the
Analysis and Design ribbon tab.
The Analysis/Print Commands dialog for post-analysis commands opens.
- Select the Story Drift tab in the Analysis/Print Commands dialog.
- Enter an Allowable Drift Factor value. This is the drift ratio value as specified by the applicable building code.
- Check the After Current option to insert the print command following the currently selected command within the Post Analysis Print - Whole Structure dialog. Otherwise, the print command will be added to the end of the STAAD input file.
- Click Add. The command is added to the STAAD Input file.
- Click Close.