Serviceability and Strength check for the same load combination


	Applies To

	Product(s):	STAAD.Pro
	Version(s):	ALL
	Environment:	ALL
	Area:	Steel Design
	Subarea:	American Design Codes
	Original Author:	Sye Chakraborty, Bentley Technical Support Group

Can I do serviceability and strength check for the same load combination ?

Yes you can do that. You need to create two separate load combinations each comprising of same load cases combined with the same combination factors. Subsequently define two load envelopes and label one of these load combinations as serviceability and other as strength. Henceforth ask for a design using both envelopes using the LOAD LIST ENV command.

An example is provided next

…

LOAD 1 DEAD LOAD

MEMBER LOAD

1 UNI Y -0.75

LOAD 2 LIVE LOAD

MEMBER LOAD

1 UNI Y -0.45

LOAD COMB 3 SERVICE LOAD

1 1.0 2 1.0

LOAD COMB 4 STRENGTH LOAD

1 1.0 2 1.0

PERFORM ANALYSIS

UNIT INCHES KIP

DEFINE ENVELOPE

3 ENVELOPE 1 TYPE SERVICEABILITY

4 ENVELOPE 2 TYPE STRENGTH

END DEFINE ENVELOPE

LOAD LIST ENV 1 2

PARAMETER 1

CODE AISC UNIFIED 2005

METHOD ASD

DFF 240 ALL

FYLD 50 ALL

UNT 140 ALL

UNB 140 ALL

TRACK 1 ALL

CHECK CODE ALL

FINISH

The software would then check the members for deflection considering load combination 3 ( or serviceability load envelope 1 ) and check the members for strength considering load combination 4 ( or strength load envelope 2 ) as part of the same code check.

You may also find the following wiki useful

https://communities.bentley.com/products/ram-staad/w/structural_analysis_and_design__wiki/20793/strength-serviceability-check-in-design