Question regarding StaadPro CE file

Question

Hello everyone, 
 
 I am modeling a steel joists truss in Staad pro CE but I am having trouble on how to resolve the warnings and errors. I have a double angle for the top chord and custom section properties for the bottom chord since staad did not have the section I was looking for. I modeled the diagonal members as steel pipes. The truss is simply supported, pin and roller. I am getting many instability warnings. Any way I could reduce these warnings. I know I cant resolve all of them. I also added a spec, "MEMBER TRUSS" for all members, by adding the MEMBER TRUSS spec, does that eliminate the need to release the members for moment? 
 
 I have attached the model to this discussion. 
 New staad pro ce user!

Steel Joist Design Model_AC.STD

Abhisek M · Answer

Hello Angel, 
 I believe you are trying to design the model as a TRUSS where the members will be subjected to only axial force. If that is the case, I would suggest changing the first line in input command file to STAAD TRUSS from STAAD SPACE. Also, you need to delete the truss specifications you have used. Yes, truss means member will be subjected to only axial force, but in a STAAD SPACE model you can not release all the members meeting at a node or provide truss spec to all of them meeting at a node. This will provide instability. I have noticed that you have modelled the top and bottom chord as continuous members and those have no connections with the vertical members. Ideally in analytical model of STAAD, all members will be connected to the intermediate nodes to form a proper load path. SO, in this case you need to break the beams at every node point to establish proper connectivity. 
 I have made all these changes in the attached file and you will find zero warnings and errors in the attached modified file. 
 Steel Joist Design Model_AC_Modified.STD

Question regarding StaadPro CE file

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