Applies To
	Product(s):	STAAD Advanced Concrete Design
	Version(s):	Connect Edition
	Environment:
	Area:	Concrete Design
	Subarea:	Slab Design
	Original Author:	Abhisek Mandal, Bentley Technical Support Group

There is a form in RCDC (IS 456) slab design to input the permissible limit of l/d ratio for two-way slabs.  (With defaults as 28 for SS and 32 for continuous.).  However, these values are  not valid if the loading class in more than 3 kPa and spans up to 3.5 m.  Please clarify.

 RCDC is a design software. the recommended values of L/D are available in design settings. i.e. for Two way simply supported slab it is 35 x 0.8 = 28 and for continuous slab it is 40 x 0.8  = 32. refer below snap from IS code.

Please note that option of changing the L/D factors are available in software as per user requirements. we understand that the above ratio available in code has certain limitation of span and loadings. Thus L/D ratio are available to modify by user. User can take the decision on the same and proceed with the design. it is always a user choice to select the L/D ratio which suits the design.