b"THE OFFICIAL NFBA MAGAZINEcontinued from page: 19 End wall Stiffness, k e= 465 + 3150 = 3615 lb/in (End well Stiffness, Building 1) Stress unities are calculated using NDS 2018 Equation 3.9-3 for bending and axial compression (individual bending The lateral stiffness of the primary frame is determinedAnalysis of Resultsand axial checks were also performed).Posts below grade are assumed to be continuously braced by compacted soil.The wet-use factor of 0.7 is applied only to a post segment located below grade.Above grade, posts are by applying a horizontal load, P, at the eave line and Frame:Knee braces significantly increased the braced by wall girts and metal siding to prevent buckling in the plane of the wall.The unbraced length for post dividing this load by the resulting frame displacement,ase , from NDS Appendix G, Table buckling in the plane of the truss is calculated using the buckling length coefficients, Klateral stiffness of the primary frames. G1: The coefficients are 0.8 for posts without knee braces and 0.65 for posts with knee braces.Analysis and design k = P/[10] are done in Visual Analysis 21 by Integrated Engineering Software, Inc., (IES, 2023).The results of the analysis are Eave Load: Rotationalrigidityatthetopofposts summarized in Table 4 and compared in Table 5. The roof and walls are sheathed with light gage corrugatedcreated by knee braces attracts a higher metal panels with an effective shear modulus, G eff , of varyingpercentage of wall load up the post into Analysis of Results magnitude.Enwalls have no openings.The horizontal stiffnessthe frame and the diaphragm.This can be Frame:Knee braces significantly increased the lateral stiffness of the primary frames. of the diaphragm is calculated using EP484.2, Equation 3: seen by a significant increase in eave load Eave Load:Rotational rigidity at the top of posts created by knee braces attracts a higher percentage of wall load C h= G eff(cos)(b h ,s)[11] (up to 45% increase).If eave load, R, was up the post into the frame and the diaphragm.This can be seen by a significant increase in eave load RESEARCH & TECHNOLOGYcalculated using Clause 6.3 of EP484.3, the (up to 45% increase).If eave load, R, was calculated using Clause 6.3 of EP484.3, the post fixity Forexample,C h forthe40x80x16buildingfactors, determined by structural analysis, would be as tabulated below: withG eff of1260lb/iniscalculatedasfollows:post fixity factors, determined by structural C h= 1,260 (cos 14.04)(40/8) = 6,112 lb/in.(Diaphragmanalysis,wouldbeastabulatedbelow:Stiffness, Building 1) Post Fixity FactorsPrescribedDetermined by Structural AnalysisHorizontal stiffness of the bare frame at each 40ft, 60ft(EP484)and 80ft endwall is 465 lb/in, 697 lb/in and 2,857 lb/in,Building Description 40' Wide 60' Wide 80' Widerespectively.The bare frame stiffness in the 40-foot wideBuildings without knee braces 0.375 0.41 0.41 0.43and 80-foot wide buildings was determined by structuralBuildings with knee braces, no slip 0.375 0.60 0.60 0.59models and was estimated for the 60-foot building usingBuildings with knee braces, with slip 0.375 0.58 0.58 0.55a 60/40 ratio multiplied by the stiffness of the 40-footDeflections: Knee braces reduced horizontal eave deflection building.Endwall posts are continuous to the top chord Deflections:Knee braces reduced horizontal eave deflection in Buildings 1 and 5 by up to 33% when joint slip is in Buildings 1 and 5 by up to 33% when joint of truss, and have the same size, spacing and foundationconsidered and by 38% when no slip is considered.This is an expected behavior.In Buildings 2, 3 slip is considered and by 38% when no slip is as the sidewall posts. The horizontal stiffness of theand 4, however, knee braces have a negative effect on horizontal eave deflection, increasing the deflection by up to 23% with slip and 26% without slip.This behavior may appear counter intuitive and considered.This is an expected behavior.In metal siding and secondary framing is calculated usingshould be noted. the product of the effective shear modulus, G eff , and theBuildings 2, 3 and 4, however, knee braces have Diaphragm:Knee braces increased load demand on end walls in Buildings 2, 3 and 4 by up to 27%, and increased a negative effect on horizontal eave deflection, building width to eave height ratio.The total endwallload demand on the diaphragm by up to 25%.In Buildings 1 and 5, this trend is reversed.increasing the deflection by up to 23% with stiffness is taken as the sum of the bare frame stiffnessAt windward post, knee braces reduced load demand on the foundation.At leeward posts, the results Foundation:slip and 26% without slip.This behavior may and stiffness of the metal siding assembly.For example,are mixed. Knee braces reduced load demand on the foundation in Buildings 2, 3 and 4, but increased the load demand in Buildings 1 and 5.Changes in load demand on the foundation are significant and appear counter intuitive and should be noted. the endwall stiffness of Building 1 is calculated as follows: range from 33% reduction to 39% increase. Diaphragm:Kneebracesincreasedloaddemand Posts:In buildings with 40-foot-span trusses, knee braces have mostly a positive effect on stress unities.In In Plane Stiffness of Bare Frame = 465 lb/in (from abuildings with 60-foot and 80-foot-truss spans, knee braces have a negative effect on stress unities.on endwalls in Buildings 2, 3 and 4 by structural model) The stress unities in posts above grade in Buildings 3, 4, and 5 with knee braces are controlled by up to 27%, and increased load demand gravity loads (D+S); load combinations with wind load are not controlling the design.Posts with knee Horizontal Stiffness of Siding Assembly = 1,260 lb/inbraces in Building 4 failed by up to 38% while posts in the same building but without knee braces onthediaphragmbyupto25%.In (40/16) = 3150 lb/in passed by 0.94 stress unity. Buildings 1 and 5, this trend is reversed. Endwall Stiffness, k e= 465 + 3150 = 3615 lb/inFoundation:At windward post, knee braces reduced load (Endwall Stiffness, Building 1) demand on the foundation.At leeward posts, Stress unities are calculated using NDS 2018 Equationthe results are mixed. Knee braces reduced 3.9-3 for bending and axial compression (individualload demand on the foundation in Buildings bending and axial checks were also performed).Posts2, 3 and 4, but increased the load demand in below grade are assumed to be continuously braced byBuildings 1 and 5.Changes in load demand compacted soil.The wet-use factor of 0.7 is applied onlyon the foundation are significant and range to a post segment located below grade.Above grade,from33%reductionto39%increase. posts are braced by wall girts and metal siding to prevent buckling in the plane of the wall.The unbraced length forPosts:In buildings with 40-foot-span trusses, knee post buckling in the plane of the truss is calculated usingbraces have mostly a positive effect on stress the buckling length coefficients, K e , from NDS Appendixunities.In buildings with 60-foot and 80-foot-G, Table G1: The coefficients are 0.8 for posts withouttruss spans, knee braces have a negative effect knee braces and 0.65 for posts with knee braces.Analysison stress unities.The stress unities in posts and design are done in Visual Analysis 21 by Integratedabove grade in Buildings 3, 4, and 5 with Engineering Software, Inc., (IES, 2023).The results of theknee braces are controlled by gravity loads analysis are summarized in Table 4 and compared in Table 5.(D+S); load combinations with wind load 20 / FRAME BUILDER - MAY2023"