George Olive - Aluminum Structures Compatibility Mode

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Aluminum Structures

November 10, 2008

George Olive, P.E.

[email protected]



•• Aluminum’s attributes• um num compare to tee

• Material designations• Finishes

•

Aluminum Structures 2



•• Your experience• s quest ons anyt me




•

and Silicon’

(8.1%)• ever oun ree n na ure• The oxide, Alumina (Al 2O3) occurs

naturally as ruby and sapphire




Histor of Aluminum• Name proposed by Sir Davy in

• Finally isolated in 1825• Hall-Heroult process (1886)

allowed commercial quantitiesto be produced

• Aluminum production requireslarge amounts of electricity Photo - ALCOA




Histor of Aluminum• Washington monument cap

s one s a um num• First used in construction in1930’s

• Wide construction usestarted in 1950’s – extrusions commonlavailable

Photo - ALCOA




•• Automobiles• urta n wa

• Storage tanks Photo - BOEING

• Highway signs

Aluminum Structures 7Photo – ENCLOS Corp



tons x 1000)

Transportation 2211 31.8

Packa in 1467 21.1

Construction 1015 14.6

Total 4693 67.5




• 3.• Increased strength and ductility at low

• Corrosion resistance• Strength from 10 to 80 ksi tensile ultimate• Can be extruded




•




Aluminum – Steel Comparison

• Aluminum is corrosion resistant, similar to

• Aluminum is 1/3 of the weight of steel• Aluminum Modulus of Elasticity is 1/3 that

of steel• Aluminum available in non-standard

sha es• Aluminum is more costly per pound




– •

material

base material strength near weld• a or y o s ee s apes are compac• Majority of aluminum shapes are not

compact




Extrusions• Made by heating and then pushing a solid

• Dies are round, up to ~ 30”• Open, hollow, and combinations shapes

are possible• Can design a new shape for a specific

application




•

– www.aluminum.org – ,

US producers

worldwide influence




•

Association – . . – Provides information on cladding systems

• Doors• Curtain wall




• nd ,

• Designing Aluminum Structures Seminar – ASCE Kissell – Usually presented in several cities each year

– On-line version available from ASCE




•• Aluminum is made into many alloys• oy=a su stance compose o two or

more metals or of a metal and a nonmetaln ma e y un e• Different aluminum alloys can have very

different material properties• Allo in elements are usuall less then 5%




• , , , , , , , ,

used

temper




• Number Main Allo Stren th Corrosion

1xxx 99%+ Al Fair Excellent2xxx Cu Hi h Fair3xxx Mn Fair Good

4xxx Si Good Good5xxx Mg Good Good6xxx Mg Si Good Good

7xxx Zn High Fair8xxx others




• st • 3 rd and 4 th and sequentially assigned• n g t enotes o var at on




•• Used in electrical connectors• us – oo con uctor

• Negative – Weak strength




•• Aircraft sheathing• us – oo strengt

• Negative – Poor corrosion resistance




•• Gutters and siding• us – very orma e

• Negative – Relatively weak




•• Boats and docks• us – trong

• Negative – Difficult to extrude




•

silicide) alloy

• Plus – Strong and corrosion resistant• Negative – Large strength loss when

welded




•• Aircraft framing• us – ery strong

• Negative – weak resistance to corrosion




•

• Heat treatment• om nat on o met o s

• Only series 2xxx, 6xxx, and 7xxx are heattreatable.




•

• Examples: 6063-T6, 3003-H14• s or stra n ar ene

• T is for heat Treated• O is annealed conditioned•

ductility




Aluminum S ecial Finish• Aluminum forms an oxidation layer when

• Natural layer is relatively soft•

with current applied forms hard anodized –




Specification for Aluminumtructures ( A )

• – Combined specification in 2010 version – – Currently parts IA & IB in Aluminum Design

• Adopted by BOCA, UBC, SBC, and IBC

• s e t on n• Now updated every 5 years




•

• III Design Guide – ps or es gn

• IV Materials – Describes alloys and tempers

• V Material Properties – Mechanical and physical




•

– For standard shapes (Channels, beams, tees,

• VII Design Aids –

• VIII Illustrative Examples of Design

– 31 examples using the SAS




•

Work in Building Construction




• -

point where yield is apparent.




• .

determine yield strength




Aluminum Stren th• Aluminum shapes are generally non-

• Need to check for all buckling modes – ong, stort ona , an oca .




•

shape




•

conservatively checks elements with ends, .

• Can use software to improve allowable.




•

free at: http://www.ce.jhu.edu/bschafer/

formed steel




Weldin effects

• Other than alloying, aluminum’s strength isa result of strain hardening or artificial aging

• The heat from welding erases these effects• Welding reduces strengths:

– For –H tempers, down to –O (annealed) – For –T tempers, usually down to –T

• Some 2xxx and 7xxx allo s aren’t weldable

• Weld affected zones are assumed to extend1” from the actual weld




Design Aids




Desi n Aids




• , y .

• Safety factor for fracture, n u = 1.95• a ety actor or connect ons, . n u = .




•

application,

usually limited to L/175, based on glass

• Roof and siding limits are usually L/60


George Olive - Aluminum Structures Compatibility Mode

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