Cable Rod failing due to KL/r?

Question

Hello all, 
 I have a Canopy model with cable stays modeled as solid bars. They are currently failing due to "L/R-EXCEEDS" - I believe this refers to KL/r compression analysis. I do not understand why STAAD is analyzing the rods under compression when I specifically assigned these members as tension only using the MEMBER TENSION command. What I also noticed is even if I increase the Fy =36 ksi to 50 ksi, the tensile strength does not effect at all the design, only if I change the diameter size. I'm not sure why this is happening either. 
 Currently, the rods are modeled as 2" diameter solid rods (inner diameter = 0). They are assumed to work with 3/4" - 1" diameters. 
 
 Any help would be greatly appreciated. I uploaded the model below. 
 Thanks! 
 ~Pascual 
 LCL Canopy Rev-06.std

Modestas · Answer

Whenever you are using tension/compression only members, the loads should be combined using the REPEAT LOAD instead of LOAD COMB. More details can be found here: https://communities.bentley.com/products/ram-staad/w/structural_analysis_and_design__wiki/3441/member-tension-and-combination-load-cases-tn

Sye · Answer

When slenderness is the failure criteria, changing tensile strength would not make a difference. The code recommends that Kl/r should be less than 300 for tension members however this recommendation need not be satisfied for tension rods. So you may just set the TMAIN parameter to a higher value ( say 400 )for these rods to pass the code check.