Roof Purlin Deflection Criteria

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Roof purlin deflection criteria.

For sake of discussion we will assume a minimal roof snow load of 20 psf pounds per square foot and a 4 12 roof slope. Roof rafters roof joists and roof beams. Plaster or gypsum board. Top running crane trc beams.

3 mezzanine beams and joists. The attached list of criteria is met. Underhung crane uhc beams. Monorail crane mr beams.

If that same joist had gypsum ceiling l 240 the allowable deflection is 0 6. Allowable deflection as an expressed ratio of the clear span. The cos of the purlin spacing is because the load on the purlins is vertical and the purlin spacing is with the run of the roof. Other than plaster or gypsum board.

1x skip sheathing is. Other than plaster or gypsum board. Floor beams floor joists and floor decking. Introduction and components roof systems 10 23 eaves beams 24 27 side rail systems 28 53 ancillary items 54 59 load tables 60 78 mezzanine floor systems 79 85.

Table r301 7 allowable deflection of structural members. Mean roof height is not greater than 40 feet. Dead load will be the actual weight of the roof steel and the roof purlins. Therefore a purlin should be adequately strong to withstand the loads it will encounter during its design life and should not sag in an obvious manner thereby giving the roof sheeting an undulating and or unpleasant appearance.

Roof sheathing is at least 7 16 thick oriented strand board or plywood.