Thank you very much for your help, I think it's going to work well with me,
I know the way to do that,
but actually there are somethings I can't understand about STAAD:
1. In my model the aligned beams in real should be one beam (not 3 as modeled) , but to connect it into the Aluminum rail I had to create nodes,so a 3 beams created instead of 1 beam, the question now: Am I going to get a correct analysis and design after doing that????
2. The load due to PV's weight is subjected directly into the Aluminum rail (just like a purlin) , and then the load is going to be transferred to aligned beams (like the rafters), and then into the columns, so my question, how can I explain this to STAAD???
I'll be very thankful for your answers to my questions =')