Purlin Outwards Capacity vs "No Cladding" capacity?
Purlin Outwards Capacity vs "No Cladding" capacity?
(OP)
Purlin tables typically list two capacities. 1. inwards capacity (where cladding restrains the critical flange) and 2. outwards capacity, where there the cladding is on the non-critical flange.
Does outwards capacity depend upon cladding on the non-critical flange? Presumably the cladding provides *some* rotational and lateral stiffness to the purlin, I'm just not sure whether the tables are including it or not.
Does outwards capacity depend upon cladding on the non-critical flange? Presumably the cladding provides *some* rotational and lateral stiffness to the purlin, I'm just not sure whether the tables are including it or not.






RE: Purlin Outwards Capacity vs "No Cladding" capacity?
I believe some utilize FE analysis to validate tabulated values.
In a more simplistic sense, I would consider the cladding to not provide torsional resistance, only translational, but it acts as a "stabilizing" load (loads away from shear centre in outwards mode, assuming it is the cladding applying the load). Together with bridging, the cladding will provide a couple and thus torsional restraint (bit of a lean on effect I suspect, if no direct load path provided), hence increased capacity for increased number of bridging.
Toby
RE: Purlin Outwards Capacity vs "No Cladding" capacity?
Put more simply - is "outwards capacity" ok to use if there's no cladding at all?
For simplicity let's assume 0 bridging
RE: Purlin Outwards Capacity vs "No Cladding" capacity?
RE: Purlin Outwards Capacity vs "No Cladding" capacity?
perpendicular on top of the purlins.RE: Purlin Outwards Capacity vs "No Cladding" capacity?
RE: Purlin Outwards Capacity vs "No Cladding" capacity?
RE: Purlin Outwards Capacity vs "No Cladding" capacity?
Have you called the manufacturer?
RE: Purlin Outwards Capacity vs "No Cladding" capacity?
RE: Purlin Outwards Capacity vs "No Cladding" capacity?
RE: Purlin Outwards Capacity vs "No Cladding" capacity?
That AISI factor does sound similar to the tables in the stramit and lysaght purlin tables I'm familiar with. The outwards load is often around 60% of the inward.
So in the case of AISI specs, my question is - would it be appropriate to use that factor if there is no cladding, or should a lower factor be used?
RE: Purlin Outwards Capacity vs "No Cladding" capacity?
RE: Purlin Outwards Capacity vs "No Cladding" capacity?