Applies To
	Product(s):	STAAD Advanced Concrete Design
	Version(s):	All
	Environment:	N/A
	Area:	Concrete Design
	Subarea:	Column & Shear Wall
	Original Author:	Abhisek Mandal, Bentley Technical Support Group

How RCDC calculates Boundary element length as per IS-13920-2016.?

Boundary elements are provided for ductile walls as per IS 13920. Zoning of reinforcement is done around
the boundary element. The initial length of the boundary element is arrived at as per following procedure:
i. Value Po is calculated Po = 0.8 x (0.85 x Fck x Ac + Fy x Ast)
ii. The largest axial force Pu in earthquake combination is determined
iii. Length of boundary element is determined based on the above two values as
a. If Pu< 0.15 x Po then length of the boundary element = 0.15 x Lw.
b. If Pu> 0.35 x Po then length of the boundary element = 0.25 x Lw.
c. If 0.15 x Po <Pu< 0.35 x Po the interpolate between 0.15 to 0.25 Lw .
The above is based on a few international papers and recommendations in the ACI code.
Reference has also been made to an IIT-Kanpur publication IITK-GSDMA-EQ22-V3.03, example 9.