b'ENGINEERS CORNERCISC provides this column as part of its commitment to the education of those interested in the use of steel in construction. Neither CISC nor the author assumes responsibility for errors or oversights resulting from the use of the information contained herein. Suggested solutions may not necessarily apply to a particular structure or application and are not intended to replace the expertise of a licensed professional engineer or architect.Question 1:WhatarethedifferentgradesofsteelinFigure1(a).Thisgenerallyoccursduring covered in ASTM A709?construction while the top compression flange is Charles Albert, P.Eng.not yet braced by the deck.Manager of TechnicalAnswer: ASTM A709 steel is used mainly for bridges Publications & Services, CISC and has been referenced in CSA S6 since the 2014 edition. It is an umbrella standard that includes thegradeslistedbelow.Foreachdesignation, the first number indicates the minimum specified yield stress, F y, in ksi, and the second number [in brackets] in MPa.36 [250]Corresponds to ASTM A36/A36M.50 [345]Corresponds to ASTM A572/ASTM A572M grade 50/345.50S [345S]Has a maximum yield stress and a FIGURE 1maximum yield-to-tensile ratio, useful for seismic (a) Gravity Loading(b) Wind Upliftapplications. It corresponds to ASTM A992/A992M and is generally available in shapes.50W[345W]HasenhancedatmosphericTheelasticbucklingmomentmaybedeterminedBETTERcorrosion resistance (weathering steel). This gradeaccording to Lateral Buckling of Beams, J.W. Clark corresponds to ASTM A588/A588M. and H.N. Hill, ASCE Journal of the Structural Division,BUILDINGHPS 50W [HPS 345W], HPS 70W [HPS 485W], HPSVol. 86, July 1960: SOLUTIONS100W[HPS690W]High-performancesteels withlowcarboncontent,resultinginimproved weldability,toughnessandcorrosionresistance. These grades are available in plates only.50CR[345CR]Stainlesssteelwithimproved EQUATION 1corrosionresistance.ItcorrespondstoASTM A1010/A1010M.where2= 1.13 and C 2= 0.45 for simply supported When notch-tough material is required, ASTM A709beamswithuniformlydistributedloading.TheOur clients know they can count on our experienced team and grades can be ordered with the addition of a suffixmagnitude of g is the vertical distance between tospecifythetypeoftensioncomponent(Tforthe shear centre and the point of application ofoutstanding products and services to make all their buildingsnon-fracturecriticalorFforfracture-critical).Andthe load, or d/2 where d is the beam depth. Forbettercommercial, industrial, institutional, and multi-residential. foreachtypeofcomponent,theimpacttestinggravity loading, the sign of g is negative whenCanam solutions are specially tailored to your project needs,temperature zone (1, 2 or 3) is specified. loading is applied above the shear centre. Another common situation involves wind uplifteven the most complex. QuestionsonvariousQuestion 2: When loading is applied on the topon a roof beam, as shown in Figure 1(b). In this case, aspectsofdesignandflange of an unbraced beam segment, CSA S16:19theunbracedbottomflangeisincompression constructionofsteelClause13.6.1(a)statesthatthedestabilizingand the upward load on the top flange exerts a buildings and bridges areeffect can be taken into account using a rationalstabilizingeffect.ThesignofginEquation1 welcome.Theymaybeanalysis. Could you provide a reference? wouldthenbepositive,increasingthemoment submittedviaemailtoresistance.info@cisc-icca.ca.CISCAnswer:WhenloadingisappliedabovetheAlternatively,S16:19providesasimple receives and attends to ashearcentre,adestabilizingmoment(Pxa)(although conservative) method to account for the large volume of inquiries;isinducedasthecross-sectionrotatesduringdestabilizing effect by using2= 1.0 and C 2= 0 and onlyaselectedfewarelateral-torsional buckling, decreasing the beamsan effective unbraced length of 1.2L for flexurally published in this column. momentcapacity.Atypicalsituationinvolvingsimplysupportedendsor1.4Lforotherend gravityloadingonafloorbeamisillustratedrestraint conditions. AS canam-construction.com8|SUMMER 2020 ADVANTAGE STEEL 1-866-466-8769'