Roof Bracing

[flin8812]

Hi all,
1) I was told that single bracings at roof carry both compression and tension loads.However, cross-bracings only take tension loads.
Why might the reasons be for the difference?

2) Plus, why is a CHS a better selection for roof bracings when you have non-hollow steel rods as an option?
What would happen if I decided to use z-sections? Why does buckling sometimes take precedent over bending? Could someone provide
me an example if it's true?

Arrrgh...I'm so confused.

Ask me to clarify these questions if you don't understand what I'm asking.

Cheers.

 

[structSU10]

1. cross bracing is just designed as tension only members - the other brace is allowed to buckle. Single braces must act in both tension and compression.

2. this is a purlin you are talking about? if a member has a long enough unbraced length the phenomenon of lateral-torsional buckling usually controls. This is when a beam moves laterally and twists.

Are you a structural engineer, or just looking into something? bracing of members is important, and understanding stability of structural members is needed to have an idea as to what is required / how to best handle the situation. If you want more theoretical knowledge "Structural Stability: Theory and implementation" by Cehn and Lui is a good reference. Otherwise "Guide to Stability Design Criteria for Metal Structures, 6th edition" from SSRC is another good book that also includes 'real' design situations.