Determination of Allowable Working Stresses for Vertically Laminated Beams

Working stresses were developed for triplicate vertical laminated Idaho white pine beams using actual tests and statistical procedures. Knots were measured, the probability of their location determined, and their effect on strength of the actual beam defined. Arguments are stated for vertical vs. horizontal lamination of beams. The full-sized beams were laminated to assure that the weakest portion of the beam was located in the middle third of the beam. Beams were tested in third point loading. Data were reduced by 9/16 for load and 0.604 for miscellaneous other conditions which included depth effect. Test results plotted for MOR or MOE vs. Ig – sum of the I of knots /Ig show that a first degree curve best fits MOR and a third degree curve best fits MOE data. Working stress thus derived are f = 2000 psi, MOE = 1,500,000 Psi, horizontal shear = 150 psi. The method used to obtain these data is suggested as an alternate to existing procedures.

You must be logged in to download any documents. Please login (login accounts are free) or learn how to Become a Member