**WARNING: WALL AREA command should be present with ST = 4. Ref Clause 7.6.2b.

Clause 7.6.2b is for calculating time period  for structures with structural wall.

There is a term called Aw which is the effective area of the walls in the first storey of the building. To calculate this Aw, the program requires some wall data which you need to provide (length and width) when you are using ST4 in the tabular format as shown below.

Hi Abhishek, 

my building size is 39.475 x 39.5 x 19.9 m, kindly clarify wall area entry dimensions consideration in staad for the following case. thank you in advance. 

Wall area entry is used to specify wall dimensions for calculating effective cross section area of wall in the first story of the building. These should specify the walls which resist seismic force along the global direction (X or Z) of the seismic load only. w is the width of the wall and l is the length of the wall. So, your entry is not correct. the width will be the thickness of wall and length will be length of the wall in that direction.

Wall area entry is used to specify wall dimensions for calculating effective cross section area of wall in the first story of the building. These should specify the walls which resist seismic force along the global direction (X or Z) of the seismic load only. w is the width of the wall and l is the length of the wall. So, your entry is not correct. the width will be the thickness of wall and length will be length of the wall in that direction.

Thank you Abhisek