I need to make a temporary work platform to go between two steel joists 8ft apart where the platform would be around 12in wide. To be on the safe side the platform should be able to support 2 adults, so say 400lb. I was thinking of making a simple box beam from 12mm constructional ply as I have enough available. My question is how deep should the beam be to support the required load?
This is not a sagulator calculation. It is intended for box beams.
Weight load as follows: 8ft span : 12in width : 2x4 Douglas Fir : 40lb psf live load : 20lb psf dead load
Range (dependent of weight distribution) Maximum moment, Mmax: 427-480 (ft:lb) Maximum shear force, Vmax: 120-240 (lb) Nailing pattern: 5in on center
If doubling plywood, glue and nailing should be spaced no closer than 2in from lower layer.
EDIT - HOW I CAME UP WITH VALUES: I was a General B Contractor and I have an app that calculates the formula based on materials(plywood and 2x?) used, what type of live and dead loads required, span length, width and returns the strength values of Mmax and Vmax based on various 2x? and nailing patterns. I based it on his 12mm plywood, 2x? douglas fir, with a live load of 40lb psf and 20lb psf dead load. The range is based on weight distribution whether evenly distributed or in one spot.