b'YOUR TOOLKIT FOR BUILDING EXCELLENCEunderstanding that certain code minimums mayowner or other stakeholder could elect to use Risk not be adequate for performance of the buildingCategory III or IV instead. throughout its useful life. A Risk Category less than the highest applicable The design loads required are primarily a functioncategory should NEVER be used. For example, a of the buildings: Risk Category II building should never be designed 1.Location (climate and which AHJ governs)as a Risk Category I building. Also, a building storing first responder vehicles should be a Risk 2.Size / shape / features of the building,Category IV building and nothing less.3.Risk Category Some Specific Design Load DecisionsRisk CategoryI, II, III, or IV Consideration must be given to the design loads The buildings Risk Category relates to the riskfrom all potential sources, including wind, snow, associated with unacceptable performance ofice, floods, and earthquakes. Since wind loads will a building and must be known to establish thegovern lateral loads in most Post-Frame projects, minimum required design loads.and since snow loads are the source of maximum vertical loads in many regions, a few comments A brief overview of the four Risk Categories: are provided for each of these sources.I.The lowest level allowed by codes and standards,Wind Loadsintended for low importance buildings thatThe Design Wind Speed, designated as V (Velocity) represent a low risk due to very limited (or no)in units of miles per hour [mph], is determined human occupancy. Certain temporary facilitiesbased on the buildings location and Risk Category. and minor storage facilities may qualify forThe building site Exposure Category (typically it this category. should be C but may also be B or D) and II.Default Category, this is for all buildings exceptother variables will affect how the Design Wind those designated as I, III, and IV. Speed is converted to a velocity wind pressure III. Buildings that represent a substantial hazard(designated asq h[psf]). This velocity pressure is to human life including certain buildings withused in the analysis of structural components and capacity for more than 250 occupants and otherthe main wind-force resisting system.higher risk scenarios listed in the building code. The Enclosure Classification could be: Enclosed, IV. Buildings designated as essential facilitiesPartiallyEnclosed,PartiallyOpen,orOpen. including fire, rescue, ambulance, and policeInternal wind pressures for a Partially Enclosed stations(andassociatedvehiclestorage),building will be much higher than for buildings of emergencyshelters,surgerycenters,andother enclosure classifications and require stronger other highest importance scenarios listed inand/or stiffer primary and secondary framing the building code. members in the building to meet strength and serviceability requirements.One option for achieving increased buildingSnow Loadperformance is to assign a higher Risk Category for the building than required. For example, ifThe Ground Snow Load (designated as p G[psf]) Risk Category II would apply to a building, thewill be assigned for the building location by ASCE continued on page: 14 FRAME BUILDER - NOV2022 / 13'