Hi. I have a question. How should I treat as horizontal brace a cable with each end connected to two turnbuckles with eye and hook? What member property and member specification should I use? Is it TENSION-ONLY member? How about the member sizing?
Model the cable using beam element, assign a cross section and assign cable specification to it as outlined in the wiki below
You would also assign the MEMBER TENSION specification to it. There is no design of cable elements in STAAD.Pro but you can always look at the axial force developed in the cable and compare that to the allowable axial tension to determine if it is adequate. Else you would need to use a different diameter cable.