Designation:D3957−09(Reapproved2015)StandardPracticesforEstablishingStressGradesforStructuralMembersUsedinLogBuildings1ThisstandardisissuedunderthefixeddesignationD3957;thenumberimmediatelyfollowingthedesignationindicatestheyearoforiginaladoptionor,inthecaseofrevision,theyearoflastrevision.Anumberinparenthesesindicatestheyearoflastreapproval.Asuperscriptepsilon(´)indicatesaneditorialchangesincethelastrevisionorreapproval.INTRODUCTIONThesepracticesarebasedontheassumptionthatstructuralmembersinlogbuildingscanbestress-gradedbymethodsthatderivefromacceptedstandardsforconventionalsolidsawnlumberandroundtimbers.Itisassumedthatthematerialtobegradedbearsenoughsimilaritytoeithersawnlumberorroundtimber,bothindimensionalpropertiesandinuse,towarrantapplicationofstress-gradingstandardswrittenforsawn-lumberorround-timber,orboth.Thesepractices,suchasPracticesD245andD2899,cannotbeapplieddirectlybecausethestructuralmembersusedinlogbuildingsaregenerallyneitherperfectlyrectangularnorperfectlyroundinsection.Thesepracticesusecertainconventionsregardingcross-sectionaldimensionsthatmakeitpossibletoextendestablishedstress-gradingmethodologiestocoverthemembersusedinlogbuildings.Wherelogmembercharacteristicsdeviatefromsawnlumberorroundtimberstandards,theremaybeuncertaintyastotheexacteffectofthedeviationonstrengthproperties.Tocompensateforthisuncertainty,somedesignstressvaluesarehereinderivedwithpracticesthatare,byengineeringjudgment,conservative.Thephilosophyguidingthisapproachisthatwhiletheabsenceofexperimentaldatamaymakeameasureofconservatismunavoidable,thereliabilityofdesignstressvaluesmustnotbeachievedthroughwoodqualityorsizerequirementsthatareanunnecessaryburdenonthewoodresource.Ingeneral,thesawing,cutting,andshavingrequiredtobringapiecetoitsfinalshapemustbecompletedbeforeitcanbevisuallygradedusingtheprinciplesinthesepractices.Smallcutsmaybeallowedaftergradingifitcanbeshownthateither(1)thecutsdonotaffectthegrade,or(2)thegradetakestheadditionalcutsintoconsideration.Bothsawnlumbersta...
