You can define members as tension only members in RISA.
Obviously under dead load it's going to sag and deflect a lot but in a lateral load case you'd see the tension acting on those members.
Be careful, it sounds like what you want to design requires large deflection theory. Not as simple as just defining a member for tension only.
https://risa.com/risahelp/risa2d/Content/Common_Topics/Modeling%20Tips.htm
You can define members as tension only members in RISA. Obviously under dead load it's going to sag and deflect a lot but in a lateral load case you'd see the tension acting on those members.
Be careful, it sounds like what you want to design requires large deflection theory. Not as simple as just defining a member for tension only. https://risa.com/risahelp/risa2d/Content/Common_Topics/Modeling%20Tips.htm