b'FEATUREWELD EFFECTIVE PROPERT IES FOR HSS CONNECTIONSBy Dr. Kyle Tousignant,Assistant Professor, Department of Civil & Resource Engineering, Dalhousie UniversityFORHOLLOWstructuralsection(HSS)FIGURE 1 : CHS-to-CHS X-connection test specimensconnections, welds can be designed either to achieve the capacity of the connected branch member wall or to be fit for purpose (i.e. to resist the forces present in the branch member). The latter approach typically results in smaller, more economical welds, but it requires the use of weld effective properties. Weld effective propertiesaccountfortheinherentnon-uniform loading of the weld perimeter in an HSS joint, which is primarily due to differ-ences in the relative flexibility of the chord member in the direction of the applied load from the branch.Over the last 30 years, research has been conductedtodetermineweldeffective(a) CHS-to-CHS X-connection (b) weld geometrypropertiesforrectangularhollowsection (RHS)connections,includinggappedand overlappedK-connections,T-,Y-andX-(or Cross-)connections,andmoment-loadedFIGURE 2:Testing arrangementT-connections.In2010,recommendationsanexperimentaltestingprogramwas basedonthisresearchwereadoptedascarried out at the University of Toronto to design rules in Section K4: Welds of Platesestablish weld effective lengths for axially andBranchestoRHSofAISC360-10(nowloadedCHST-,Y-,andX-connections. Section K5, in AISC 360-16). In Canada, similarAsetof12connectiontestspecimens, methods to calculate weld effectiveness (i.e.fabricatedfromlarge-sizeASTMA500 weld effective properties for RHS connections)dual-certifiedGradeB/CHSS,were areavailableinPacker&Henderson(1997).designedtobeweldcritical(i.e.to These are referenced in Part 3: Connectionsfail by weld fracture) under axial tension and Tension Members of the 11th edition ofappliedtothebranches,asshownin the CISC Handbook. However, AISC 360 andFigure 1a. The chord members were HSS Packer&Henderson(1997)arebothsilent10.750.500andHSS16.000.500, concerningweldeffectivepropertiesforwith branches (inclined at 90 or 60 to circular hollow section (CHS) connections. Thisthe chord) selected to obtain branch-to-isbecauseuntilrecentlynosupportingchord width ratios () ranging from 0.25 to research had been performed.0.47 and branch-to-chord thickness ratios ()rangingfrom0.60to0.99.Welding EXPERIMENTAL TESTINGprocedure specifications were developed With the financial support of CISC and the(inconjunctionwithtrialsectioning) federal government, and in-kind supporttoachieveminimalbutadequateroot fromWaltersGroupandAtlasTube,penetration, and a professional fabricator 14|FALL 2019 ADVANTAGE STEEL'