nascc 2007 - aisc 13th edition specification
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8/18/2019 NASCC 2007 - AISC 13th Edition Specification
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Josh Plummer, S.E.Josh Plummer, S.E.
Director of Training & SupportDirector of Training & SupportFoothill Ranch, CA Foothill Ranch, CA
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Electronic Automation of theElectronic Automation of the
AISC 13 AISC 13thth EditionEdition
Analysis Methods of Chapter CAnalysis Methods of Chapter C
Direct Analysis MethodDirect Analysis Method(Appendix 7)(Appendix 7)
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Summary of New RequirementsSummary of New Requirements
•• Must Account for GeometricMust Account for GeometricImperfections (Out ofImperfections (Out of PlumbnessPlumbness))
•• Must Account for 2Must Account for 2ndnd Order EffectsOrder Effects
(P(P-- ∆ ∆ & P& P--δδ))•• Must Include Member StiffnessMust Include Member Stiffness
Reductions Due to Residual StressesReductions Due to Residual Stresses
•• Use of KUse of K--Values Can Be Eliminated inValues Can Be Eliminated in
Most CasesMost Cases
Analysis MethodsAnalysis Methods
Of Chapter COf Chapter C
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Methods Meeting RequirementsMethods Meeting Requirements
11stst Order AnalysisOrder Analysis
Amplified 1Amplified 1stst Order AnalysisOrder Analysis
General 2General 2ndnd Order AnalysisOrder Analysis
Direct Analysis Method (Appendix 7)Direct Analysis Method (Appendix 7)
Analysis MethodsAnalysis Methods
Of Chapter COf Chapter C
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11stst Order AnalysisOrder Analysis (Section C2.2b)(Section C2.2b)
•• Only Allowed WhenOnly Allowed When•• PPr r ≤≤ 0.5P0.5Pyy (LRFD)(LRFD)
•• PPr r ≤≤ 0.3125P0.3125Pyy (ASD)(ASD)
•• Must Include Minimum Notional Load inMust Include Minimum Notional Load in ALL ALL Load CombinationsLoad Combinations
•• NNii = 2.1(= 2.1(ΔΔ // L)YL)Yii ≥≥ 0.0042Y0.0042Yii
•• Must Apply BMust Apply B11 Amplifier to all Member Amplifier to all Member
MomentsMoments
•• BB11 = C= Cmm/(1/(1-- αα
PPr r /P/Pe1e1))≥≥
11
Analysis MethodsAnalysis Methods
Of Chapter COf Chapter C
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Amplified 1Amplified 1stst Order Analysis (C2.1b)Order Analysis (C2.1b)
•• Qualifies as a 2Qualifies as a 2ndnd Order AnalysisOrder Analysis
•• MMr r = B= B11MMntnt + B+ B22MMltlt•• PPr r = P= Pntnt + B+ B22PPltlt
BB11 = C= Cmm/(1/(1-- ααPPr r /P/Pe1e1)) ≥≥ 11
BB22 = 1/(1= 1/(1--((αΣαΣPPntnt//ΣΣPPe2e2)))) ≥≥ 11
++ The Additional Requirements ofThe Additional Requirements ofGeneral 2General 2ndnd Order AnalysisOrder Analysis
Analysis MethodsAnalysis Methods
Of Chapter COf Chapter C
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General 2General 2ndnd Order AnalysisOrder Analysis
Any Method That Accounts for Any Method That Accounts for PP--ΔΔ & P& P--δδ
Additional Requirements: Additional Requirements:
1.1. ASD Analysis Shall Be Carried Out Under 1.6 ASD Analysis Shall Be Carried Out Under 1.6x Load Combinations (Results Divided by 1.6)x Load Combinations (Results Divided by 1.6)
2.2. Must Include Minimum Notional Load in AllMust Include Minimum Notional Load in AllGravity Load CombinationsGravity Load Combinations
3.3. Must Use KMust Use K--Factors for Moment FrameFactors for Moment FrameColumns If (2Columns If (2ndnd Drift / 1Drift / 1stst Drift) > 1.1Drift) > 1.1
Analysis MethodsAnalysis Methods
Of Chapter COf Chapter C
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Direct Analysis MethodDirect Analysis Method (Appendix 7)(Appendix 7)
•• Preferred Method in AISC SpecificationPreferred Method in AISC Specification
•• No Restrictions on UseNo Restrictions on Use
•• Must Be Used if (2Must Be Used if (2ndnd Drift / 1Drift / 1stst Drift) > 1.5Drift) > 1.5
Direct AnalysisDirect Analysis
MethodMethod
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Geometric ImperfectionsGeometric Imperfections
•• Apply Notional Loads = 0.002Y Apply Notional Loads = 0.002Yii(Assumes Imperfection = L / 500)(Assumes Imperfection = L / 500)
•• Notional Loads May Be Reduced WhenNotional Loads May Be Reduced When
Imperfections Are Smaller Imperfections Are Smaller
•• If (2If (2ndnd Drift / 1Drift / 1stst Drift) < 1.5, Notional LoadsDrift) < 1.5, Notional Loads
Apply To Gravity Load Combinations Only Apply To Gravity Load Combinations Only
Direct AnalysisDirect Analysis
MethodMethod
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22ndnd Order AnalysisOrder Analysis
•• PP-- ∆ ∆ (Big Delta) Analysis(Big Delta) Analysis Always Required Always Required
•• PP--δδ (little delta) Analysis(little delta) AnalysisCan Be Ignored IfCan Be Ignored If ααPPr r < 0.15P< 0.15PeLeL
Example: W12x65 Column (L = 15Example: W12x65 Column (L = 15’’))
PPeLeL = 4708 kips= 4708 kips PPyy = 955 kips= 955 kips
ΦΦPPnn = 746 kips= 746 kips →→ 0.16P0.16PeLeL
Direct AnalysisDirect Analysis
MethodMethod
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AISCAISC ““BenchmarkBenchmark”” ProblemsProblemsDirect AnalysisDirect AnalysisMethodMethod
Case 1Case 1
Case 2Case 2
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BenchmarkBenchmark – – Case 1Case 1Direct AnalysisDirect AnalysisMethodMethod
Electronic Automation of theElectronic Automation of the
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Zero JointsZero Joints
One JointOne Joint
Three JointsThree Joints
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BenchmarkBenchmark – – Case 1Case 1Direct AnalysisDirect AnalysisMethodMethod Case 1: Deflection Amplification
1.00
1.50
2.00
2.50
3.00
3.50
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7
Axial Force Normalized by Euler Buckling Load, P/Pe
A
m p l i f i c a t i o n F a c t o r , Y m
RISA (1 Node) RISA (3 Nodes) RISA (10 Nodes) AISC Benchmark
Electronic Automation of theElectronic Automation of the
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BenchmarkBenchmark – – Case 1Case 1Direct AnalysisDirect AnalysisMethodMethod Case 1: Moment Amplification
1.00
1.50
2.00
2.50
3.00
3.50
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7
Axial Force Normalized by Euler Buckling Load, P/Pe
A
m p l i f i c a t i o n F a c t o r ,
M m
RISA (1 Node) RISA (3 Nodes) RISA (10 Nodes) AISC Benchmark
Electronic Automation of theElectronic Automation of the
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BenchmarkBenchmark – – Case 2Case 2Direct AnalysisDirect AnalysisMethodMethod Case 2: Deflection Amplification
1.00
1.50
2.00
2.50
3.00
3.50
4.00
4.50
5.00
0 0.05 0.1 0.15 0.2
Axial Force Normalized by Euler Buckling Load, P/Pe
A m p l i f i c a t i o n F a c t o r , Y m
RISA (1 Node) RISA (3 Nodes) RISA (10 Nodes) AISC Benchmark
Electronic Automation of theElectronic Automation of the
AISC 13 AISC 13thth EditionEdition
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BenchmarkBenchmark – – Case 2Case 2Direct AnalysisDirect AnalysisMethodMethod Case 2: Moment Amplification
1.00
1.50
2.00
2.50
3.00
3.50
4.00
4.50
5.00
0 0.05 0.1 0.15 0.2
Axial Force Normalized by Euler Buckling, P/Pe
A m p l i f i c a t i o n F a c t o r , M m
RISA (1 Node) RISA (3 Nodes) RISA (10 Nodes) AISC Benchmark
Electronic Automation of theElectronic Automation of the
AISC 13 AISC 13thth EditionEdition
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Material NonMaterial Non--Linearity EffectsLinearity Effects
Axial Stiffness ReductionAxial Stiffness Reduction•• 0.8EA0.8EA – – For Members Whose AxialFor Members Whose Axial
Stiffness Contributes To Lateral Stability ofStiffness Contributes To Lateral Stability of
StructureStructure – – Columns That Are Part of LFRSColumns That Are Part of LFRS
– – Braces That Are Part of LFRSBraces That Are Part of LFRS
Direct AnalysisDirect Analysis
MethodMethod
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Material NonMaterial Non--Linearity EffectsLinearity Effects
Flexural Stiffness ReductionFlexural Stiffness Reduction•• 0.80.8ττbbEIEI – – For Members Whose FlexuralFor Members Whose Flexural
Stiffness Contributes To Lateral Stability ofStiffness Contributes To Lateral Stability of
StructureStructure – – Beams That Are Part of Moment FramesBeams That Are Part of Moment Frames
– – Columns That Are Part of Moment FramesColumns That Are Part of Moment Frames
– – TauTau ((ττbb) Is Based on Axial Load) Is Based on Axial Load
•• TauTau May Be Set toMay Be Set to ‘‘1.01.0’’ If AnIf An Additional Additional
Notional Load (0.001YNotional Load (0.001Yii) Is Included) Is Included
Direct AnalysisDirect Analysis
MethodMethod
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Analysis Methods of Chapter CAnalysis Methods of Chapter C
•• 11
stst
Order AnalysisOrder Analysis•• Amplified 1Amplified 1stst Order AnalysisOrder Analysis
•• General 2General 2ndnd Order AnalysisOrder Analysis
Direct Analysis MethodDirect Analysis Method (Appendix 7)(Appendix 7)•• Geometric Imperfections (Notional Loads)Geometric Imperfections (Notional Loads)
•• 22ndnd Order EffectsOrder Effects
•• Material NonMaterial Non--LinearityLinearity
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RISARISA’’s Implementation of D.A.M.s Implementation of D.A.M.
Notional LoadsNotional Loads
PP--∆∆ (Big Delta)(Big Delta)
PP--δδ (little delta)(little delta) Automated StiffnessAutomated Stiffness
AdjustmentsAdjustments
Direct AnalysisDirect Analysis
MethodMethod
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Josh Plummer, S.E.Josh Plummer, S.E.
Foothill Ranch, CAFoothill Ranch, CA
(800) 332(800) 332--RISARISA
joshp@risatech.com joshp@risatech.com
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