Ductwork Supports

[DLB203]

Hello,

I am a vent engineer of 6 years based in the UK and have recently embarked on a new design with some limited external DW144 ductwork that is no higher than 10m from ground level.

The structural engineer has asked whether some relative displacement is allowable between supports on our DW144 ductwork. I see no reference to anything that states any allowable displacements in any of the related standards. I have not been asked this question on any previous project. Is there a standard solution or code that structural engineers work to when designing a support structure for external ductwork? Any advice welcome.

 

[milkshakelake]

I think they're just asking as a matter of course. Us structural engineers don't want things to be too rigid and get bent out of shape due to natural deflections of a structure, but we also don't want things moving too much.

I'm not sure about European or UK standards. Closest I can get is in IBC 2021 table 1604.3 Deflection Limits. The center of a structural span can deflect up to l/240 in most cases, where l is the span. That means at the ends of the span, the deflection is closer to zero. I think the engineer wants to make sure your ductwork can handle this level of difference in deflection. If everything deflected equally, they wouldn't care, but that's not how real life works.



This deflection has almost nothing to do with you. It's caused by the weight of building materials, superimposed dead load (like partitions and tiles), and live load. But it does affect the ductwork since it has to be connected to the structure or floor by necessity.