Roof Purlin Deflection Criteria

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Roof purlin deflection criteria.

Underhung crane uhc beams. 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. This post will be focusing on design of steel purlin using cold formed sections. Floor beams floor joists and floor decking.

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. 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. Plaster or gypsum board. Mean roof height is not greater than 40 feet.

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. Dead load will be the actual weight of the roof steel and the roof purlins. Table r301 7 allowable deflection of structural members. Allowable deflection as an expressed ratio of the clear span.

Roof sheathing is at least 7 16 thick oriented strand board or plywood. Z section purlins 10 c section trimmer 51 side rails 28 7 metsec uk leaders in the design and manufacture of engineered and bespoke purlin and side rail building solutions. Roof rafters roof joists and roof beams. 3 mezzanine beams and joists.

Other than plaster or gypsum board. Monorail crane mr beams. Other than plaster or gypsum board. Top running crane trc beams.

For example the allowable deflection of a 12ft span floor joist with plaster l 360 is 0 4 12ft divided by 360.