#### siggy_7

##### Full time tool collector, part time woodworker

I found the following properties for structural grade OSB/3: 16.4MPa bend strength parallel to span, 8.2MPa perpendicular to span, 1MPa planar shear. Do these figures sound about right?

I did some calcs per m width (parallel to span). Using basic beam theory, for a uniformly distributed load of 150kg/m^2, the max bending moment is wL^2/8 = 123Nm. The second moment of area I is bd^3/12; for d=0.018m this gives I = 4.86x10^-7m^4. Maximum distance from neutral axis y = 0.009m, therefore the maximum bending stress = 123 * 0.009 / 4.86E-7 = 2.28MPa, which is well within the bending strength of the board. The maximum shear force is wL/2 = 608N, for a cross-sectional area of 0.018m^2 the shear stress is 608 / 0.018 = 33.8kPa, again well within the material strength.

If my calculations are correct then 18mm OSB should comfortably take a 150kg/m^2 load with plenty in reserve. I read somewhere that wood can creep if it's continuously loaded above 50% of its strength but again I think I'm within this limit. Any thoughts on whether my calculations are reasonable and what I'm considering is sensible much appreciated.