huangyhg

tension pullout of sheet metal screws
i'm looking at a connection where i have a #14 screw fastening two pieces of sheet metal siding together. both siding sections have stiffeners. they will be acting compositely spanning about 6'. my concern is leeward wind suction acting at the exterior siding. how would i calculate the pullout capacity of the connection? obviously, the local yielding of the sheet metal around the screw is going to govern, not the screw itself. what area do i take for yielding around the screw? or am i looking at this the wrong way?
thanks

screw manufacturers publish ultimate pullout values for different material gauges and screw sizes. normally a safety factor of 4 is used to determine allowable pullout.
if you are in north america, the naspec governs the design of cold-formed steel, similar to how aisc is used for hot-rolled structural steel. there are equations for designing screw connections in chapter e. you can also check with specific screw manufacturers but then you will be designing with their numbers, not generic numbers. note also that you need to check pull-over as well as pull-out, though that may not govern your case.
here is a table exerpt from one of the manuals referred to, put out by the metal stud manufacturer's association, and based on an icbo er report no. 4943 from june of 1992:
mike mccann
mmc engineering
i needed this type of information a few days ago and called fastenal's technical services and they provided tested pullout values and the equations for non-tested values for the fasteners i had selected. i'm sure other suppliers, such as hilti, have the same services available.

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