Achieving equivalence in floor deflection performance with differing lumber grading systems

Contemporary design of wood floor systems requires that they be strong enough as well as stiff enough. Stiffness, which most often governs the design, is evaluated as bare joist performance based on an average value of modulus of elasticity (MOE). Two engineered lumber grading systems are considered: visual stress rating (VSR) and machine stress rating (MSR). Corresponding groups of VSR and MSR may have the same average MOE but the variability is much lower in the MSR case. This study simulated hole floors in groups of 500 and investigated the lower ranges of floor stiffness for each grading system. With stiffness measured by span-deflection ratios and 10th percentile comparison criteria, the results suggest that equivalence in floor deflection performance between grading systems can be achieved with MSR lumber having lower average MOE than VSR lumber.

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