Steel roof diaphragm

[ABDSUU]

Hello,

I have this steel roof that rafter is levelled while purlins are at a 3 degree slope with up to 800mm higher than the rafer.

Now my question is in regard to the roof diaphragm. I don't think I can use the rakers that supports the purlins together with rafter to form a diaphragm since they are at different level. Rather, I should have wind beam all around together with brace at rafter level. Am I wrong? Is there anything I miss?

 

[hokie66]

The roofing is for shedding water, not for resisting lateral forces.

Those tall purlin cleats need to be stiffer, perhaps angles. Or better still, rake the rafter with the roof slope.

You need a bracing system, typically forming horizonatal trusses, to distribute the wind forces to the vertical walls or bracing.

 

[HTURKAK]

You are wright .. if the rafters are also at 3 degr slope, the purlins could also serve for horizontal struts.. In this case, you need horizontal bracing at rafter level with extra struts and wind beams .. If you post the full plan with some descriptive sketches etc. you could get better responds..