Superposition of two models in staad pro

Question

Dear All, 
 I am new member of the forum and am looking for some answers in regards to one of my Staad Pro models. 
 Greatly appreciate some information from you all experienced engineers. 
 
 Can we super-postion two models in Staad Pro? 
 I have 
 1. Model-1 with some DL and Prestressing loads with a roller condition at one end support. ( for stage-1 during structure erection) 
 2. Model-2 with all other DL+LL and wind loads as applicable to the whole structure. The support conditions are changed to pinned ( post erection) 
 I would like to get the member forces from model -1 to be super-positioned with model-2 ( or superposition member forces from these two models). Can STAAD carry out this task? 
 Thanks in advance for your suggestions. 
 Regards 
 David Chacko

Kris Sathia · Answer

It should be possible to do that with the INACTIVE MEMBER command. 
 
First, define the entire model (which you are referring to as model-2). Next, use the INACTIVE MEMBER command to switch off portions that are part of model2 but not model1. Also, specify the supports corresponding to model 1. 
 
This will be followed by the load cases meant for model 1. Then a PERFORM ANALYSIS command followed by CHANGE. 
 
The CHANGE command tells STAAD to re-activate all the members that were inactivated earlier. We now have the full model-2. Next, specify the supports and load cases meant for model 2. Then a PERFORM ANALYSIS command followed by CHANGE. 
 
Specify the combination cases using the LOAD COMBINATION syntax. Once again, provide a PERFORM ANALYSIS command followed by CHANGE.