Snow Load Factors For Lrfd

Snow load factors are critically examined for use in load and resistance factor design (LRFD). Specifically examined are the effects on structural reliability of the change in the basic ground load to roof load conversion factor from 0.8 to 0.7 and recent statistical data concerning the conversion factor. Using the recent data on the groundload to roof‐load conversion factor, statistics are obtained for the one‐year and fifty‐year snow load. Based on these statistics, the reliability index is on the order of 1.6 when snow load controls the design. Increasing the snow load factor from 1.6 to 2.0 increases the reliability index to roughly 2.0. Also examined is the use of extreme value theory to model the 50‐year snow load. It is determined that a direct application of extreme value theory leads to inaccurate estimates of structural reliability.