Draft

3.2Aluminum 61

3.1.2 ReinforcingSteel

14 Steelis alsousedas reinforcingbarsin concrete,Table3.2. Thosebarshave a deformation

ontheirsurfaceto increasethebondwithconcrete,andusuallyhave a yieldstressof 60 ksi

1

.

BarDesignation Diameter Area Perimeter Weight

(in.) (in

2

) in lb/ft

No. 2 2/8=0.250 0.05 0.79 0.167

No. 3 3/8=0.375 0.11 1.18 0.376

No. 4 4/8=0.500 0.20 1.57 0.668

No. 5 5/8=0.625 0.31 1.96 1.043

No. 6 6/8=0.750 0.44 2.36 1.5202

No. 7 7/8=0.875 0.60 2.75 2.044

No. 8 8/8=1.000 0.79 3.14 2.670

No. 9 9/8=1.128 1.00 3.54 3.400

No. 10 10/8=1.270 1.27 3.99 4.303

No. 11 11/8=1.410 1.56 4.43 5.313

No. 14 14/8=1.693 2.25 5.32 7.650

No. 18 18/8=2.257 4.00 7.09 13.60

Table3.2:Propertiesof ReinforcingBars

15 Steellosesitsstrengthrapidlyabove 700deg.F (andthus mustbe properlyprotectedfrom

re),andbecomesbrittleat30 deg.F

16 Steelis alsousedas wirestrandsandropes forsuspendedroofs,cable-stayed bridges,fabric

roofsandotherstructuralapplications. Astrandis a helicalarrangement of wiresarounda

centralwire.Aropeconsistsof multiplestrandshelicallywoundarounda centralplasticcore,

anda modulusof elasticity of 20,000ksi,andanultimatestrengthof 220ksi.

17 PrestressingSteelcableshave anultimatestrengthupto 270ksi.

3.2 Aluminum

18 Aluminumis usedwheneverlight weightcombinedwithstrengthis animportant factor.

Thoseproperties,alongwithitsresistanceto corrosionhave madeit thematerialof choice

forairplanestructures,light roof framing.

19 Aluminummemberscanbe connectedby riveting,boltingandto a lesserextent by welding.

20 Aluminumhasamodulus of elasticity equalto 10,000 ksi(aboutthreetimeslower

thansteel),a coecient of thermalexpansionof 2: 4  10

 5

anda density of 173lbs=ft

3

.

21 Theultimatestrengthof purealuminumis low (13,000psi)butwiththeadditionof alloys

it cangoup.

1

Stirrupswhich areusedas verticalreinforcement to resistshearusuallyhave a yieldstressof only 40 ksi.