b'THE OFFICIAL NFBA MAGAZINEcontinued from page: 25ASCE 7-16 vs. ASCE 7-22 Snow load example 2. Increased Thermal Factor:The thermal factor The practical distinctions between the two versionsfor ventilated roofs has increased.of the standard are demonstrated in this example. The example in Minneapolis, however, demonstrates Design Criteria: a decrease in roof snow load, despite the increase in the thermal factor.Shop building (Risk Category II) Summary and ConclusionVentilated flat roof with R-25 insulation or betterASCE 7-16 Thermal factor, C t= 1.1 The move to reliability-targeted ultimate ground RESEARCH & TECHNOLOGY(ASCE 7-16, Table 7.3-2) snow loads, incorporating an expanded dataset ASCE 7-22 Thermal factor, C t= 1.2 and risk-specific mapping, addresses the inherent (ASCE 7-22, Table 7.3-2) inconsistencies of the previous uniform-hazard method.These changes ensure more consistent ASCE 7-16 Snow load importance factor, I s=1.0 structural safety nationwide, improved accuracy ASCE 7-22 Snow load importance factor, I s= N/A in load determination, and a significantly reduced number of case-study areas.The changes are significant Exposure factor, C e= 1.0 and create a strong potential for miscommunication Dead load on roof, D = 10 psf between old ground snow loads with a 1.6 load factor, Flat roof snow load, ASCE 7-16: pf = 0.7 C eC tI sp gand new ultimate ground snow loads with 1.0 load (ASCE 7-16, Eq. 7.3-1) factor.Specifically, using old ground snow loads with new load factors is a critical error that will result in Flat roof snow load, ASCE 7-22: pf = 0.7 C eC tp gseverely under-designed buildings. Verifying that (ASCE 7-22, Eq. 7.3-1) the correct version of ASCE 7 is selected in design Table 1 summarizes the results of this example forprograms is now even more important.The safe and four different cities. In three out of the four cities,effective application of these major updates hinges on staying informed, promptly adjusting design the roof snow load calculated using ASCE 7-22practices and software, and maintaining strong, clear increased by 25% to 53% compared to ASCE 7-16communication among all professionals involved in standard.This increase is attributed to two specificthe design process.design factors which have changed in ASCE 7-22:1. Higher Ground Snow Loads: The ground snow loads, even when converted from the ultimate to ASD levels, have increased at the three selected locations.Table 1: Example of snow loads on flat roofs using ASCE 7-16 and ASCE 7-22 specifications Ground SnowRoof SnowASD Load CombinationsChange DeadLoadLoad(positive LocationLoadASCE 7-16ASCE 7-22value ASCEASCEASCEASCEindicates 7-16 7-22 7-16 7-22 D+SD+0.7Sincrease) (psf)(psf)(psf)(psf)(psf)(psf)(psf)% Baltimore, MD10255919.349.629.344.753% Boston, MA10406530.854.640.848.218% Detroit, MI10203715.431.125.431.825% Minneapolis, MN10505838.548.748.544.1-9%26 / FRAME BUILDER - VOL6 4'