EWPAA Structural Plywood and LVL Design Manual - Engineered ...

5. Critical Load Action EffectsLoad Case 1 Load Case 2UDLwwSpan, LSpan, LSpan, LSpan, LM max = 49wL 2 /512Vmax= 9wL/16∆max = wL 4 /(72.3EI)M ma x = -wL 2 /8Vmax= 5wL/8∆max = wL 4 /(185EI)ConcentratedLoadPPPSpan, LSpan, LSpan, LSpan, LM max = 13PL/64Vmax= -19P/32∆max = PL 3 /(66.7EI)M max = 6PL/32Vmax= 11P/16∆max = PL 3 /(110EI)Note:The shear strength limits were also considered when high concentrated loads act at, or close to asupport joist. Applying the theory for beams on elastic foundations, Paulet (1945) as expanded in “LoadDistribution in Wooden Floors Subjected to Concentrated Loads” by N.H. Kloot and K.B. Schuster –Division of Forest Products, CSIRO 1965, indicates that load distribution will result in concentratedloads applied close to supports being less critical for shear strength than a centrally appliedconcentrated load.For example, for a floor consisting of 300 x 40mm F8 joists at 400 mm centres, spanning 2400 mm and24 mm F11 structural plywood flooring, the ratio of joist stiffness to flooring stiffness is {E j.I j.L 3 (spacing) /E f.I f.L 3 (span)} = 0.18, which results in a reaction on the joist under the concentrated load equal to 60%of the applied load. As 20% of the applied load is transferred to the joist/s either side of the appliedload, the expected plywood shear force is 60% of the applied load which is less than the 11/16 th of theapplied load used when a central concentrated load is applied on each span. (reference: AssumptionsUsed and An Example Calculation of Allowable Point Live Loads, 1990, Adkins & Lyngcoln).57