Applies To
	Product(s):	STAAD.Pro
	Version(s):	ALL
	Environment:	ALL
	Area:	Analysis
	Subarea:	Direct Analysis
	Original Author:	Sye Chakraborty, Bentley Technical Support Group

 

Can I run a DIRECT ANALYSIS with INACTIVE MEMBER specification applied to some members ?

 

Yes you can run a DIRECT ANALYSIS in a model with INACTIVE MEMBER specification assigned to certain members. A typical use case for that would be to deactivate braces, which are supposed to take tension only, from cases where they develop compression force. In such situations, carry out a DIRECT ANALYSIS first with these members specified as TRUSS members. Check the member forces to find out, for which load cases the axial forces in these members come out as compressive. Use the INACTIVE MEMBER command to deactivate these members for these cases and rerun the analysis. The members can be active for other cases for which they develop tension force.

 

An example demonstrating how INACTIVE MEMBERs can be used in conjunction with DIRECT ANALYSIS is attached. In the example the braces 9 to 14 are supposed to behave as tension only members. Hence all of these members are deactivated for the load case 1 which is a gravity load. The members are deactivated selectively for the cases 2 and 3 ( gravity + lateral load ) such that members that are in tension, are the only ones that are active for the load case.

 

communities.bentley.com/.../Direct_5F00_Analysis_5F00_with_5F00_Inactive_5F00_Members.STD