Applies To
	Product(s):	STAAD.Pro
	Version(s):	All
	Environment:	N/A
	Area:	Steel Design
	Subarea:	IS 800:2007
	Original Author:	Surojit Ghosh Bentley Technical Support Group

I am using IS800:2007 code. How can I perform deflection check using service load cases?

Since STAAD.Pro SS6 version, it is necessary to specify the service load envelope before the design parameter command to perform the deflection check. Else deflection check is not performed by the program and a warning message will be printed in the output file as --

**WARNING- Deflection check of member # xx will not be performed as service envelope not provided.

For IS800:2007 code, the design routine can do deflection checks based on SERVICEABILITY LOAD ENVELOPES and strength checks based on STRENGTH LOAD ENVELOPES as part of the same design cycle. One needs to define serviceability envelope and strength envelope first consisting of the appropriate cases and then define a LOAD LIST ENV command  for the design to consider these as explained below. 

For example, if you have defined strength load combination cases 100 to 120 and serviceability combination cases 200 to 210, to perform the deflection check along with the strength check, you need to first define the load envelopes as --

DEFINE ENVELOPE
100 TO 120 ENVELOPE 1 TYPE STRENGTH
200 TO 210 ENVELOPE 2 TYPE SERVICEABILITY
END DEFINE ENVELOPE

In the next step, you need to use the LOAD LIST ENV command and specify those envelopes as --

LOAD LIST ENVELOPE 1 2

PARAMETER 1

CODE IS800 LSD

< Specify all design parameters including the deflection check parameters - DFF, DJ1, DJ2>

CHECK CODE ALL

STAAD then use load cases 100 to 120 for strength checks and load cases 200 to 210 for deflection check. DFF parameter is necessary to perform the deflection check. By default, the value of DFF is considered as zero which means deflection check will be skipped. DFF value should be provided according to Table 6 of IS800:2007 code and assigned to the members for which deflection check is required. If service load envelope is defined but DFF parameter is not specified, deflection check will not be performed.

NOTE : In any older version of STAAD (SS5, SS4 version etc.), the above mentioned criteria was not necessary. In those versions, one could include the LOAD LIST <load case numbers> command and deflection check parameters and the program used to report the deflection check results.