STAAD.Pro Help

TR. Identification of Floor Level

The following two ways can identify floor level:

  • Program calculated
  • User defined

For regular building which has well defined floors (i.e., does not contain shear wall, staggered flooring, etc), STAAD.Pro can identify floor level on its own. However, if floor level is not so well defined, it is better to define floor height to have more accurate result for the purpose of torsion and soft story checking.

Program calculated

In general, STAAD.Pro identifies floor levels in order of increasing magnitude of Y-coordinates of joints.  The program sorts different values of Y-coordinates, from minimum to maximum values, in ascending order and consider each Y-coordinate value as each floor level.  This is the method used by the DEFINE UBC or similar load generation features.

This feature has been enhanced to identify the beam-column junctions at each floor level, as identified by the method above.  If no beam-column junctions are identified at that level, a floor level will not be considered at that level in the structure.  Where beam-column junctions are found, the program identifies two beams, at the same level which span in two different directions from the same beam-column junction.  If this true, this identified floor level will be considered as truly existing floor level in the structure.

The enhanced feature for finding floor level is being used by lateral load generation feature for response spectrum analysis and soft story checking as per IS1893-2002 code. For response spectrum analysis, story drift and soft story checking is performed only when floor heights are specified.

User defined

Floor heights should be defined before using the DEFINE command for any primary response spectrum load case. The following general format is used for a user-defined floor height:

    h1; h2; h3; …;hi -
    hi+1; …;hn
(BASE hb)


h1hn The different floor heights in current length unit and n is the number of floor levels.
BASE hb The base level with respect to which 1st story height will be calculated. If hb is not defined, the minimum Y-coordinate value present in the model will be taken as base level.

User-defined floor heights are used by lateral load generation for response spectrum analysis and soft story checking as per IS1893-2002 code.

See TR.32.12.2 Generation of Seismic Loads for an example of the correct usage of this command.
Note: Floor height values cannot be used when the FLOOR DIAPHRAGM is used. Refer to TR.28.2 Floor Diaphragm for details.