Randy Kissell, P.E. TGB Partnership

1 Designing Aluminum Structures 11 Aluminum Structural Member Design Randy Kissell, PartnershipDesigning Aluminum Structural Members2 Outline1 Introduction2 Aluminum alloys and tempers3 Aluminum material properties4 Aluminum structural design overview5 Axial tension6 Axial compression7 FlexureDesigning Aluminum Structures 21. IntroductionWhy learn aluminum structural design?To design aluminum structuresTo better understand steel structural designDesigning Aluminum Structures3 Designing Aluminum Structures4 Examples of Aluminum Structures Curtain walls and storefrontsRoofing and canopiesSpace framesTanks and vessels (corrosive & cryogenic)Portable structures (scaffolding, ladders)Highway products (signs, light poles, bridge rail)Designing Aluminum Structures 3 Designing Aluminum Structures5 Science Land Egg (164 wide)

2 Courtesy of TemcorDesigning Aluminum Structures6 Science Land Eggcourtesy of TemcorDesigning Aluminum Structures 4 Designing Aluminum Structures7 The Aluminum AssociationFounded in 1933, 50+ members are the major US producersAA writes most standards on aluminum; has worldwide influenceContact: Wilson Blvd, Suite 600 Arlington, VA 22209 703-358-2960; pubs 301-645-0756 2010 Aluminum Design ManualDesigning Aluminum Structures8 Designing Aluminum Structures 5 Designing Aluminum Structures9 Aluminum Design Manual (ADM)Now issued every 5 yearsLatest edition is ADM 2010 Previous editions in 2005, 20001stedition (1994) was compilation of several AA pubs previously issued separately; most importantly, the Specification for Aluminum Structures(SAS)Designing Aluminum Structures10 Aluminum Design Manual ContentsThe Aluminum Design Manual (ADM) provides aluminum structural design toolsPart I Specification for Aluminum StructuresPart II CommentaryPart III Design GuidePart IV Material PropertiesPart V Section PropertiesPart VI Design AidsPart VII Illustrative Examples Designing Aluminum Structures 6 Designing Aluminum Structures11 Specification for Aluminum Structures(SAS)

3 The Specification for Aluminum Structuresis Part I of the Aluminum Design ManualSAS is also called the Aluminum Specification Adopted in BOCA, UBC, SBC, and IBCIt s the source of all aluminum structural design requirements in the USDesigning Aluminum Structures12 Specification for Aluminum Structures(SAS)2010 edition is a major rewriteIt s a unified Specification, with both:Allowable Strength Design For buildings and bridgesLoad and Resistance Factor Design For buildings only Load factors from ASCE 7 (= + )Designing Aluminum Structures 7 Designing Aluminum Structures132010 Specification for Aluminum Structures (SAS)A. General ProvisionsB. Design RequirementsC. Design for StabilityD. Design of Members for TensionE.

4 Design of Members for Compression F. Design of Members for FlexureG. Design of Members for ShearH. Design of Members for Combined Forces and TorsionJ. Design of ConnectionsDesigning Aluminum Structures142010 Specification for Aluminum Structures (SAS)L. Design for ServiceabilityM. Fabrication and ErectionAppendices1. Testing3. Design for Fatigue4. Design for Fire Conditions5. Evaluation of Existing Structures6. Design of Braces for Columns and BeamsNew in 2010 Designing Aluminum Structures 8 Designing Aluminum Structures152. Aluminum Alloys and TempersWrought alloy designation systemAluminum temper designation systemMaterial specifications Designing Aluminum Structures16 Aluminum Isn t Just One ThingLike other metals, aluminum comes in many alloysAlloy = material with metallic properties, composed of 2 or more elements, of which at least one is a metalDifferent aluminum alloys can have very different propertiesAlloying elements are usually < 5%Designing Aluminum Structures 9 Designing Aluminum Structures17 AlloysAlloys of iron are called steel Carbon < or it s cast ironC, Cr, Ni, Mb, Cu, Ti usedAlloys of aluminum are called aluminum alloys Si, Fe, Cu, Mn, Mg, Cr, Ni, Zn.

5 Ti usedDesigning Aluminum Structures18 Designating Aluminum vs. SteelSteel is identified by ASTM no. and gradeExample: ASTM A 709 Grade 50 Steel ASTM specs are for one alloy and a few products (for example, shapes and plate)Aluminum is identified by AA no., temper, and productExample: 6061-T6 sheetAluminum ASTM specs are for many alloys and one product ( , ASTM B 209)Designing Aluminum Structures 10 Designing Aluminum Structures19 Wrought Alloy Designation SystemNumberMain AlloyStrengthCorrosion1xxx> 99% AlFairExcellent2xxxCuHighFair3xxxMnFairG ood4xxxSiGoodGood5xxxMgGoodGood6xxxMg SiGoodGood7xxxZnHighFair8xxxothersDesign ing Aluminum Structures20 Wrought Alloy Key1stdigit denotes main alloying element3rdand 4thdigits are sequentially assigned2nddigit denotes a variationExample:2319 is AlCu alloy (2xxx), variation on 22192319 composition is identical to 2219 except slightly more Ti (grain refiner to improve weld strength).

6 Both have CuDesigning Aluminum Structures 11 Designing Aluminum Structures211xxx Alloys (pure Al)Common uses:Electrical conductorsCorrosive environmentsExamples1060 ( aluminum)1100 ( aluminum)Pro: corrosion resistant, good conductorsCon: Not very strongDesigning Aluminum Structures222xxx Alloys (Al-Cu)Common UsesAircraft parts, skinsFasteners Example2024 Pro: StrongCon: Not very corrosion resistant; hard to weldDesigning Aluminum Structures 12 Designing Aluminum Structures233xxx Alloys (Al-Mn)Common UsesRoofing and sidingGutters and downspoutsExamples3003, 3004, 3105 Pro: Formable, good corrosion resistanceCon: Not that strongDesigning Aluminum Structures244xxx Alloys (Al-Si)Common UsesWelding and brazing filler metalExample4043 Pro: Flows wellCon: Lower ductilityDesigning Aluminum Structures 13 Designing Aluminum Structures255xxx Alloys (Al-Mg)Common UsesMarine applicationsWelded plate structures Examples5052, 5083 Pro: Strong, even when weldedCon: Hard to extrude.

7 Those with 3%+ Mg can have corrosion resistance issuesDesigning Aluminum Structures266xxx Alloys (Al-Mg2Si)Common UsesStructural shapesPipe Examples6061, 6063 Pro: Good combination of strength and corrosion resistance, very extrudableCon: Lose considerable strength when weldedDesigning Aluminum Structures 14 Designing Aluminum Structures277xxx Alloys (Al-Zn)Common UsesAircraft parts Two classesWith copper (example: 7075)Without copper (example: 7005)Pro: Very strong (7178-T6 Ftu= 84 ksi)Con: Not very corrosion resistant; hard to weldDesigning Aluminum Structures28 How Alloys are StrengthenedAlloying elements (Mg is good example)Treatment:Strain hardening (cold working)Heat treatmentHeat treatable: 2xxx, 6xxx, 7xxxNon-heat treatable.

8 1xxx, 3xxx, 5xxxDesigning Aluminum Structures 15 Designing Aluminum Structures29 Annealed ConditionBefore tempering, alloys start in the annealed condition (-O suffix)Annealed condition is weakest but most ductileTempering increases strength, but decreases ductilityMost alloys are annealed by heating to 650oF (melting point is about 1100oF)Designing Aluminum Structures30 Strain HardeningMechanical deformation at ambient tempsFor sheet and plate, deformation is by rolling to reduce the thicknessSome non-heat treatable alloys undergo a stabilization heat treatmentPurpose: to prevent age softeningOnly used for some Al-Mg (5xxx) alloysDesigning Aluminum Structures 16 Designing Aluminum Structures31 Strain Hardened TempersTemperFtu(ksi) Description5052-O25 Annealed5052-H3231 hard5052-H3434 hard5052-H3637 hard5052-H3839 Full hardDesigning Aluminum Structures32 effect of Strain Hardening 5052 Designing Aluminum Structures 17 Designing Aluminum Structures33 Heat Treating1) Annealed material is solution heat treated6061-O is heated to 990oF, then quenchedResulting temper is 6061-T42) Solution heat treated material is precipitation heat treated (artificially aged)

9 6061-T4 is heated to 350oF and held for 8 hrsResulting temper is 6061-T6 Designing Aluminum Structures34 Heat Treatment TempersT1 through T4: naturally aged (6005-T1)T5 through T9: artificially aged (6063-T6)Artificial aging makes the stress-strain curve flatter after yield, which affects the inelastic buckling strengthDesigning Aluminum Structures 18 Designing Aluminum Structures35 Tempers Summarized-H is for strain hardened tempers1xxx, 3xxx, 5xxx alloysHigher 2nddigit: stronger, less ductile-T is for heat treated tempers2xxx, 6xxx, 7xxx alloysT4 = solution heat treatedT5 and greater = precipitation heat treatedDesigning Aluminum Structures36 ASTM Wrought Aluminum SpecificationsB 209 Sheet and PlateB 210 Drawn Seamless TubesB 211 Bar, Rod, and WireB 221 Extruded Bars, Rods, Wire, Profiles and TubesB 241 Seamless Pipe and Seamless Extruded Tube B 247 Die Forgings, Hand Forgings.

10 Rolled Ring Forgings Designing Aluminum Structures 19 Designing Aluminum Structures37 ASTM Wrought Aluminum SpecificationsB 308 Standard Structural Profiles B 316 Rivet and Cold Heading Wire and Rod B 429 Extruded Structural Pipe and Tube B 928 High Magnesium Aluminum Alloy Sheet and Plate for Marine and Similar Service (has corrosion resistance reqs)There are others not included in SAS, including some used structurallyDesigning Aluminum Structures383. Aluminum Material PropertiesStrengthsModulus of Elasticity, Poisson s RatioDuctilityEffect of Welding on PropertiesDesigning Aluminum Structures 20 Designing Aluminum Structures39 Aluminum s Stress-Strain CurveAfter yield, plastic behavior Linear region at low strainsslope is Aluminum Structures40 Yield StrengthAluminum doesn t exhibit a definite yield point like mild carbon steel stress-strain curve is more like high strength steel offset is used to define yieldGage length for yield is 2 in.