CE495 Seminars in Civil Engineering Partially Enclosed University of Southern California

Enclosed University of Southern California

CE495 Seminars in Civil Engineering Partially Enclosed University of Southern California

26.1PROCEDURES
26.1.1Scope.Buildingsandotherstructures,includingthemain windforceresistingsystem(MWFRS)andallcomponents andcladding(C&C)thereof,shallbedesignedandconstructed toresistthewindloadsdeterminedinaccordancewith Chapters26through31.Theprovisionsofthischapterdefine basicwindparametersforusewithotherprovisionscontainedin thisstandard.
26.1.2PermittedProcedures.Thedesignwindloadsfor buildingsandotherstructures,includingtheMWFRSand C&Celementsthereof,shallbedeterminedusingoneofthe proceduresasspecifiedinthissection.Anoutlineoftheoverall processforthedeterminationofthewindloads,includingsection references,isprovidedinFig.26.1-1.
26.1.2.1MainWindForceResistingSystem.Windloadsfor theMWFRSshallbedeterminedusingoneofthefollowing procedures:
DirectionalProcedureforbuildingsofallheightsasspeci-fiedinChapter27forbuildingsmeetingtherequirements specifiedtherein;
EnvelopeProcedureforlow-risebuildingsasspecifiedin Chapter28forbuildingsmeetingtherequirementsspeci-fiedtherein;
DirectionalProcedureforBuildingAppurtenances(rooftop structuresandrooftopequipment)andOtherStructures (suchassolidfreestandingwallsandsolidfreestanding signs,chimneys,tanks,opensigns,single-planeopen frames,andtrussedtowers)asspecifiedinChapter29;or
WindTunnelProcedureforallbuildingsandallother structuresasspecifiedinChapter31.
26.1.2.2ComponentsandCladding.WindloadsonC&Con allbuildingsandotherstructuresshallbedesignedusingoneof thefollowingprocedures:
AnalyticalProceduresprovidedinParts1through6,as appropriate,ofChapter30;or
WindTunnelProcedureasspecifiedinChapter31. BASICWINDSPEED,V:Three-secondgustspeedat33ft (10m)abovethegroundinExposureC(seeSection26.7.3)as determinedinaccordancewithSection26.5.1.
BUILDING,ENCLOSED:Abuildingthathasthetotalarea ofopeningsineachwall,thatreceivespositiveexternalpressure,
lessthanorequalto4sqft(0.37m2)or1%oftheareaofthat wall,whicheverissmaller.Thisconditionisexpressedforeach wallbythefollowingequation: Ao<0.01Ag;or4sqftð0.37m2Þ ;whicheverissmaller; whereAoandAgareasdefinedforOpenBuildings.BUILDING,LOW-RISE:Enclosedorpartiallyenclosed
buildingthatcomplieswiththefollowingconditions:
Meanroofheighthlessthanorequalto60ft(18m).
Meanroofheighthdoesnotexceedleasthorizontal dimension.
BUILDING,OPEN:Abuildingthathaseachwallatleast 80%open.Thisconditionisexpressedforeachwallbythe
equationAo≥0.8Ag,where
Ao=totalareaofopeningsinawallthatreceivespositiveexternalpressure,inft2(m2);and
Ag=thegrossareaofthatwallinwhichAoisidentified,inft2(m2).
BUILDING,PARTIALLYENCLOSED:Abuildingthat complieswithbothofthefollowingconditions:
Thetotalareaofopeningsinawallthatreceivespositive externalpressureexceedsthesumoftheareasofopenings inthebalanceofthebuildingenvelope(wallsandroof)by morethan10%.
Thetotalareaofopeningsinawallthatreceivespositive externalpressureexceeds4ft2(0.37m2)or1%ofthearea
ofthatwall,whicheverissmaller,andthepercentageof openingsinthebalanceofthebuildingenvelopedoesnot exceed20%.
Theseconditionsareexpressedbythefollowingequations:Ao>1.10Aoi
Ao>4ft2ð0.37m2Þor
>0.01Ag;whicheverissmaller;andAoi∕Agi≤0.20 whereAoandAgareasdefinedforOpenBuilding;
Aoi=sumoftheareasofopeningsinthebuildingenvelope(wallsandroof)notincludingAo,inft2(m2);and
Agi=sumofthegrosssurfaceareasofthebuildingenvelope(wallsandroof)notincludingAg,inft2(m2).

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