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Presenter: MattBrown,P.E.

RISAWebinar

UnderstandingandOptimizingHotRolledSteelDesigninRISA

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INTEGRATEDPROGRAMS

RISAFloor5.1

RISA3D9.1

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AISC36005(13th EditionSteelConstructionManual)

AISCDesignGuide#9(Torsion)

AISCDesignGuide#11(Vibration)

REFERENCEDCODES

ImagescourtesyofAISC.org

http://www.aisc.org/store/p-1578-Steel-Construction-Manual-Thirteenth-Edition.aspx

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TodaysTopics

DirectAnalysisMethod

WarpingTorsion

SingleAngles

FloorVibrations

SteelJoists

OVERVIEW

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AISCSpecificationChapterC

StabilityAnalysisandDesign

DIRECTANALYSISMETHOD

AISCSpecificationAppendix7

DirectAnalysisMethod

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DirectAnalysisRequirements

1. SecondOrderAnalysis(P ,P )

2. StiffnessReduction

(EI*,

EA*)

3. NotionalLoads

REQUIREMENTS

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EXAMPLEPROBLEM

CantileverColumn

W12x45

200kGravityLoad

10kLateralLoad

120Tall

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P ANALYSIS

InitialShear: 10k

InitialMoment: (10k)*(12ft)=120ftk

InitialDeflection: =0.981

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P ANALYSIS

BendingDeflection: =0.981

ShearDeflection: =0.035

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P ANALYSIS

FinalShear: 11.6k

FinalMoment: 139ftk

FinalDeflection: 1.182

16%IncreaseoverFirstOrder

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P ANALYSIS

FinalShear: 12.5k

FinalMoment: 140ftk

FinalDeflection: 1.216

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DirectAnalysisRequirements

1. SecondOrderAnalysis(P ,P )

2. StiffnessReduction

(EI*,

EA*)

3. NotionalLoads

REQUIREMENTS

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STIFFNESSREDUCTION

FlexuralStiffness AxialStiffness

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DirectAnalysisRequirements

1. SecondOrderAnalysis(P ,P )

2. StiffnessReduction

(EI*,

EA*)

3. NotionalLoads

REQUIREMENTS

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NOTIONALLOADS

PerAISCCodeofStandardPractice

ErectionToleranceforColumns

(outofplumb)=H/500

NotionalLoad(N)=P/500

P

N

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DirectAnalysisRequirements

1. SecondOrderAnalysis(P ,P )

2. StiffnessReduction(EI*,EA*)

3. NotionalLoads

REQUIREMENTS

K=1.0

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TraditionalDesign DirectAnalysis

M=120kft M=152kft

K=2.1 K=1.0

Reqd Shape: Reqd Shape:

W12x40 W12x45

COMPARISON

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WarpingTorsion

affectsWideFlange

andChannelShapes

WARPINGTORSION

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IdealizeastwoWTsections,

eachinminoraxisbending

WARPINGTORSION

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SINGLEANGLES

GeometricBending PrincipalBending

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FLOORVIBRATION

FloorVibrationProcedure:

1. Determinedampingweight

2. Determinebeamnaturalfrequency

3. Calculateexpectedacceleration

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FLOORVIBRATION

DampingWeight

BeamSelfWeight

+SlabWeight

+RealisticSuperimposedLoad(11psf?)

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FLOORVIBRATION

AllowableAcceleration

Basedon65lbexcitationforce(footfall)

0.5%gforOffices,Residences,Churches

1.5%gforShoppingMalls

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STEELJOISTS

w P

ActualLoad

EquivalentUniformLoad

w

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Presenter: MattBrown,P.E.

AdditionalResources AISCPublications

RISA3DHelpFile/Manual

www.risanews.com

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