A tension member will not fail because of its slenderness ratio but may flap about if the tension is alternately applied and released. An example of this is a cross braced frame where each diagonal member is designed to resist tension only; a change in direction of force on the frame causes a stressed member to be suddenly released while its companion becomes stressed.
I don't think it's going to fail because of the L/r ratio explicitly, but it might fail because a tension member with a very high L/r ratio is going to be quite flexible and prone to vibrating and wobbling, possibly causing fatigue-related issues down the road (at least that's my understanding). I assume this is building-related, but for bridges AREMA and AASHTO both limit L/r for tension members to 200 or 240.
In addition to what BA mentioned, handling is an issue with extremely slender tension members. When L/r exceeds 300 (the suggested limit retired mentioned from AISC), it's more likely that the material will be damaged as it flops around like a wet noodle on the site.
No limit on KL/r for cable members. But, AISC does suggest limiting the KL/r ration for rods, and single angles and such. I haven't looked this up lately. But, if member serves me correct, it's not because of a capacity issue, but that they tend to get easily damaged / kinked. Hence the recommendation (not rule) about KL/r < 300.
Also, I believe some iterations of RISA enforce this recommendation. Though it can be changed in Tools - Preferences / Application Settings.
Thank you all, Really appreciated,
It seems that the member was failing due to the suggested value L/R exceeds 300 in STAAD and it turned to be that I can turn this check off in STAAD.
