CE 2352 DESIGN OF STEEL STRUCTURES

CE 2352DESIGN OF STEEL STRUCTURESUNIT I INTRODUCTION07/01/2015CONTENT FOR TODAYIntroductionCommon steel structuresMerits and demerits of steel structuresProperties of structural steelCharacteristics of structural steelTypes of steel sectionsConsiderations in steel designLoads and combinationsStructural analysisCE 2352 Design of Steel Structures - UNIT 1 (1) Prepared by Ruby Freya2INTRODUCTIONSteel plays important role in automobiles, shipping, machinery, construction Iron, steel, stainless steel has different aspectsStructural steel can be hot rolled or cold formedSteel as high strength per unit mass.Steel can be mild steel and high tensile steel (IS 2062)DesignationE250 yield strengthFe400 ultimate tensile strengthCE 2352 Design of Steel Structures - UNIT 1 (1) Prepared by Ruby Freya3INTRODUCTIONSteel is an alloy consisting mostly of iron, with a carbon content between 0.2 % and 2.14 % by weight.Small % of manganese, sulphur (brittleness), phosphorous (brittleness), chrome (corrosion and temperature resistance) , nickel (corrosion and temperature resistance) and copper (corrosion resistance) are also availableMelting point 2750 degree FahrenheitSteel can be recycled.A sustainable construction materialStructures with better quality and longer lastingAesthetically distinctiveCE 2352 Design of Steel Structures - UNIT 1 (1) Prepared by Ruby Freya4

INTRODUCTIONIRON CARBON PHASE DIAGRAMIn general, increasing carbon content increases the strength but reduces ductility.Ferrite (): Iron in a BCC structure. Maximum solubility of carbon in ferrite is low (0.02%C). Ferrite has relatively low strength but is very ductile.Austenite: Iron with a FCC structure. Due to FCC structure, more carbon atoms can be accommodated. Maximum solubility of carbon in austenite is 2.11%.Cementite (or iron carbide): This forms when solubility of carbon in solid iron is exceeded. Fe3C contains 6.67%C. Cementite is present in all commercial steels. Iron carbide has high strength but little ductility.Pearlite: Lamellar structures of ferrite and cementite. Gives the hardness characteristicsCE 2352 Design of Steel Structures - UNIT 1 (1) Prepared by Ruby Freya5Manufacture of steel6

CE 2352 Design of Steel Structures - UNIT 1 (1) Prepared by Ruby FreyaVideo

Semi finished productsCE 2352 DSS - UNIT 1 (1)7

INGOTSLABBLOOM BILLETCE 2352 Design of Steel Structures - UNIT 1 (1) Prepared by Ruby Freya8

COMMON STEEL STRUCTURESCE 2352 Design of Steel Structures - UNIT 1 (1) Prepared by Ruby Freya9COMMON STEEL STRUCTURESRoof trusses for factories, auditoriumsCrane girders and gantry girdersSheds in railway stations and bus standsPlate girder and truss bridges for railways, roads, footpathsTransmission towers for microwave and electric powerWater tankschimneys

CE 2352 Design of Steel Structures - UNIT 1 (1) Prepared by Ruby Freya10

COMMON STEEL STRUCTURES

CE 2352 Design of Steel Structures - UNIT 1 (1) Prepared by Ruby Freya11

COMMON STEEL STRUCTURESCE 2352 Design of Steel Structures - UNIT 1 (1) Prepared by Ruby Freya12

COMMON STEEL STRUCTURES

CE 2352 Design of Steel Structures - UNIT 1 (1) Prepared by Ruby Freya13

COMMON STEEL STRUCTURESCE 2352 DSS - UNIT 1 (1)14

CE 2352 DSS - UNIT 1 (1)15

MERITS OF STEEL STRUCTURESHigh strengthEconomic structureLighter structureUniform properties homogeneityFollows Hookes law up to proportionality limitDuctile large deformationToughnessExtension of structuresCE 2352 Design of Steel Structures - UNIT 1 (1) Prepared by Ruby Freya16MERITS OF STEEL STRUCTURESHigh qualityAestheticLow maintenanceRe usableDismantled and re erected easilyFast track constructionResistant to insectsEconomic materialCE 2352 Design of Steel Structures - UNIT 1 (1) Prepared by Ruby Freya17MERITS OF STEEL STRUCTURESFactory madeQuality controlGas and water tightScrap valueEasily strengthened or retrofitted

CE 2352 Design of Steel Structures - UNIT 1 (1) Prepared by Ruby Freya18DEMERITS OF STEEL STRUCTURESHeat conductivity, fire spray protection, board protection, intumescent coating, concrete encasementCorrosion resistance by barrier coatings, inhibitive primer coatings, sacrificial primers, periodic anti corrosive paintingMaintenance costSusceptible to bucklingfatigueCE 2352 Design of Steel Structures - UNIT 1 (1) Prepared by Ruby Freya19PROPERTIES OF STRUCTURAL STEELPHYSICAL PROPERTIESDensity = 7850 kg/m^3Modulus of elasticity = 2x10^5 MpaModulus of rigidity = 0.769x10^3 MpaPoissons ratio = 0.3Coefficient of thermal expansion = 12x10^-6 /degree CCE 2352 Design of Steel Structures - UNIT 1 (1) Prepared by Ruby Freya20PROPERTIES OF STRUCTURAL STEELMECHANICAL PROPERTIESUltimate strength or Tensile strengthProof or yield stressDuctilityToughness capacity to absorb energy

CE 2352 Design of Steel Structures - UNIT 1 (1) Prepared by Ruby Freya21Structural Steel - PropertiesCE 2352 Design of Steel Structures - UNIT 1 (1) Prepared by Ruby Freya22Elastic Limit:Transition from elastic to inelastic behaviorYield Point:Stress Fy at the elastic limit

Structural Steel - PropertiesCE 2352 Design of Steel Structures - UNIT 1 (1) Prepared by Ruby Freya23Residual Strain:Permanent deformation after unloadingStructural Steel - PropertiesCE 2352 Design of Steel Structures - UNIT 1 (1) Prepared by Ruby Freya24

If Yield Point not Clearly Defined0.2% Method0.2% StrainDraw line parallel to elastic partCE 2352 Design of Steel Structures - UNIT 1 (1) Prepared by Ruby Freya25UTM and servo controlled UTMASTM testing methodology coupon test , dumbell shaped specimenHigh strength steel has small elongation and mild steel has larger elongationLimit of proportionalityElastic limitUpper yield point and Lower yield point depends on cross sectionPlastic yieldingStrain hardeningAtoms re orient to rescue the material Ultimate stressNeckingFailureStructural Steel - PropertiesCE 2352 DSS - UNIT 1 (1)26Structural Steel Sectional / Geometric PropertiesAreaMoment of Inertia about x-x and y-y axisRadius of gyrationSection modulusPlastic modulus

Structural Steel - CharacteristicsCE 2352 Design of Steel Structures - UNIT 1 (1) Prepared by Ruby Freya27Elasticity:Ability of metal to return to its original shape after loading and subsequent unloadingFatigue:Cycling loading and unloading stresses material above its endurance limit and leads to failureDuctility:Deformation without fracture beyond the elastic limit (ineleastic behavior)High DuctilityToughness:Combination of strength and ductilityHigh toughnessStructural Steel - SectionsTypical Hot Rolled Steel ShapesCE 2352 Design of Steel Structures - UNIT 1 (1) Prepared by Ruby Freya28

Structural Steel - SectionsTypical Cold-Formed Light Gage Steel ShapesCE 2352 Design of Steel Structures - UNIT 1 (1) Prepared by Ruby Freya29

Structural Steel - SectionsIS specified sections

CE 2352 Design of Steel Structures - UNIT 1 (1) Prepared by Ruby Freya30I SectionISJB (Indian Standard Junior Beam), ISLB(Light Beam), ISMB(Medium Beam), ISWB(Wide Flanged Beam), ISHB(Heavy weight Beam)ChannelISLC, ISJC, ISMCAngleISA equal angle and unequal anglePipeFlatsRods

Structural Steel - SectionsBuilt-Up MembersCE 2352 Design of Steel Structures - UNIT 1 (1) Prepared by Ruby Freya31

CONSIDERATIONS IN STEEL DESIGNSections should be available in marketAccess to exposed elements for repairSize and shapeBucklingMinimum thicknessConnection designs

CE 2352 Design of Steel Structures - UNIT 1 (1) Prepared by Ruby Freya32Design LoadsCE 2352 Design of Steel Structures - UNIT 1 (1) Prepared by Ruby Freya33

Most important and difficult task is the accurate estimation of loads applied to a structure over its life Second most difficult is to determine load combinations LOADSDead Load IS 875 part 1Live Load IS 875 part 2Wind Load IS 875 part 3Earthquake Load IS 1893Erection LoadAccidental LoadCrane loadSnow loadHydrostatic and earth pressureCE 2352 Design of Steel Structures - UNIT 1 (1) Prepared by Ruby Freya34LOADS COMBINATIONSDL + LLDL + LL + WL or ELDL + WL or EL

CE 2352 Design of Steel Structures - UNIT 1 (1) Prepared by Ruby Freya35STRUCTURAL ANALYSISCE 2352 Design of Steel Structures - UNIT 1 (1) Prepared by Ruby Freya36Find internal forces developed axial forces and momentsElastic analysisPlastic analysisAdvanced analysisDynamic analysisTHANK YOUCE 2352 Design of Steel Structures - UNIT 1 (1) Prepared by Ruby Freya37Steel properties, classification, applications

Quiz How many design philosophies are there? Why so many types?

Topics for next lectureDesign philosophiesLimit State Design ConceptsDiscussion on latest code (IS800-2007)