Draft

Chapter 3

STRUCTURAL MATERIALS

1 Proper understandingof structuralmaterialsis essentialto bothstructuralanalysisandto

structuraldesign.

2 Characteristicsof themostcommonlyusedstructuralmaterialswillbe highlighted.

3.1 Steel

3.1.1 StructuralSteel

3 Steelis analloyof ironandcarbon. Itspropertiescanbe greatlyvariedby alteringthe

carboncontent (alwayslessthan0.5%)orby adding otherelements such assilicon,nickle,

manganeseandcopper.

4 Practicallyallgrades of steelhave a YoungModulusequalto29,000ksi, density of 490

lb/cuft, anda coecient of thermalexpansionequalto 0: 65  10

 5

/degF.

5 Theyieldstressof steelcanvaryfrom40 ksito 250ksi.Mostcommonlyusedstructuralsteel

areA36(yld= 36 ksi)andA572(yld= 50 ksi),Fig.3.1

6 Structural steelcan be rolledinto a widevariety of shapes andsizes. Usuallythe most

desirablemembersarethosewhich have a largesectionmoduli(S) in proportionto theirarea

(A), Fig.3.2.

7 Steelcanbe bolted,rivetedor welded.

8 Sectionsaredesignatedby theshape of theircrosssection,theirdepthandtheirweight. For

exampleW 27  114 is a Wsection,27 in.deepweighing 114 lb/ft.

9 Commonsectionsare:

Ssectionswerethe rstonesrolledin Americaandhave a slope ontheirinside
angesurfaces

of 1 to 6.

Wor wide
angesectionshave a much smallerinnerslope which facilitatesconnectionsand

rivetting.Wsectionsconstituteabout50%of thetonnageof rolledstructuralsteel.

C arechannelsections

MCMiscellaneouschannelwhich cannotbe classi edas a C shape by dimensions.