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CHANGES in AISC’s SEISMIC PROVISIONS:
AISC 341-05 to AISC 341-10
S. K. Ghosh Associates Inc.
Palatine, IL and Aliso Viejo, CA
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AISC Seismic Provisions
AISC Seismic Provisions provide System Ductility
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System Ductility
“System Ductility” is the ability of system to maintain stability after yielding/overload of some elements
Ductility
V
∆∆∆∆
• Ability of yielding/overloaded elements to deform
• Ability of non-yielding elements to withstand forces redistributed by yielding
• Ability of non-yielding elements to withstand deformations caused by yielding
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Seismic Provisions Measures
For each Seismic Force Resisting System
Identify target yield mechanism of the system
Designate deformation-controlled elements
Design remaining elements as force-controlled
Protect critical locations
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Seismic Provisions Measures
Identify target yield mechanism of the system
Flexural Yield
Tension yield and compression buckling
Shear Yield
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Stable yield
Seismic Provisions Measures
Designate deformation-controlled elements
• Design for element ductility
M
θ
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Design remaining elements as force-controlled
• Design to keep members essentially elastic at capacity of ductile elements
Resist redistributed forces
Seismic Provisions Measures
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Accommodatedeformations
Seismic Provisions Measures
Design remaining elements as force-controlled
• Design for deformations caused by yielding
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Protected Zones
Seismic Provisions Measures
Amplify forces
Demand Critical Welds
Protect critical locations
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Key Points
Reorganized chapters for consistency with AISC 360
Increased protection of critical locations
Added new systems and connections
Provided consistent capacity analysis requirements
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ROADMAP
Chapter Reorganization
General
Members
Connections
Moment Frames
Braced Frames
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Seismic Provisions 341-05 Part I:
1: Scope
2: Referenced Specifications, Codes, and Standards
3: General Seismic Design
4: Loads, Load Combinations, Nominal Strengths
5: Structural Drawings and Specifications, Shop Drawings, and Erection Drawings
6: Materials
7: Connections, Joints, and Fasteners
8: Members
9-17: Structural Systems
18: Quality Assurance Plan (Appendix Q)
Appendices P, R, S, T, W, X
Part II: Composite Systems
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AISC 341-10 Organization
A. General Requirements
B. General Design Requirements
C. Analysis
D. General Member and Connection Design Requirements
E. Moment-Frame Systems
F. Braced-Frame and Shear-Wall Systems
G. Composite Moment-Frame Systems
H. Composite Braced-Frame and Shear-Wall Systems
I. Fabrication and Erection
J. Quality Control and Quality Assurance
K. Prequalification and Cyclic Qualification Testing Provisions
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Chapter Reorganization
Preface to AISC 341-10
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AISC 341-05 - Part I
1. Scope
2. Referenced Specifications, Codes, and Standards
AISC 341-10
A. General Requirements
B. General Design Requirements3. General Seismic Design
4. Loads, Load Combinations, Nominal Strengths
A. General Requirements
I. Fabrication and Erection
5. Structural Drawings and Specifications, Shop Drawings, and Erection Drawings
6. Materials
Chapter Reorganization
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AISC 341-05 - Part I
7. Connections, Joints, and Fasteners
AISC 341-10
D. General Member and Connection Design Requirements
I. Fabrication and Erection
8. Members D. General Member and Connection Design Requirements
7.3b. Demand Critical Welds A. General Requirements
A3.4b. AWS D1.8
Chapter Reorganization
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AISC 341-05 - Part I AISC 341-10
9. Special Moment Frames
10. Intermediate Moment Frames
11. Ordinary Moment Frames
12. Special Truss Moment Frames
E. Moment-Frame Systems
E3. Special Moment Frames
E2. Intermediate Moment Frames
E1. Ordinary Moment Frames
E4. Special Truss Moment Frames
E5. Ordinary Cantilever Column Systems
E6. Special Cantilever Column Systems
Chapter Reorganization
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AISC 341-05 - Part I
13. Special Concentrically Braced Frames
14. Ordinary Concentrically Braced Frames
15. Eccentrically Braced Frames
16. Buckling-Restrained Braced Frames
17. Special Plate Shear Walls
AISC 341-10
F. Braced-Frame and Shear-Wall Systems
F2. Special Concentrically Braced Frames
F1. Ordinary Concentrically Braced Frames
F3. Eccentrically Braced Frames
F4. Buckling-Restrained Braced Frames
F5. Special Plate Shear Walls
Chapter Reorganization
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AISC 341-05 - Part I
18: Quality Assurance Plan (Appendix Q)
AISC 341-10
J. Quality Control and Quality Assurance
Appendix P: Connection Prequalification
Appendix S: Qualifying Cyclic Tests of Beam-to-Column and Link-to-Column Connections
Appendix T: Qualifying Cyclic Tests of BRBF Braces
K. Prequalification and Cyclic Qualification Testing Provisions
Chapter Reorganization
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J. Quality Control and Quality Assurance
No significant change within AISC 341
2012 IBC: Special Inspection
• 1705.2.1 Structural steel .
• Special inspection provisions for structural steel are now by reference to AISC 360-10 (see Chapter N)
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Appendix X: Weld Metal/Welding Procedure Specification Notch Toughness Verification Test
AISC 341-05 - Part I
Appendix W: Welding Provisions
AISC 341-10
A. General Requirements
A4.4a. AWS D1.8
I. Fabrication and Erection
Appendix R. Seismic Design Coefficients and Approximate Period Parameters
A. General Requirements
A4.4a. AWS D1.8
REMOVED
Chapter Reorganization
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AISC 341-05 - Part II
1. Scope
2. Referenced Specifications, Codes, and Standards
AISC 341-10
A. General Requirements
B. General Design Requirements3. General Seismic Design
4. Loads, Load Combinations, Nominal Strengths
D. General Member and Connection Design Requirements
5. Materials
6. Composite Members
7. Composite Connections
A. General Requirements
Chapter Reorganization
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G. Composite Moment-Frame Systems
G4. Composite Partially Restrained Moment Frames
G3. Composite Special Moment Frames
G2. Composite Intermediate Moment Frames
G1. Composite Ordinary Moment Frames
AISC 341-05 - Part II
8. Composite Partially Restrained Moment Frames
9. Composite Special Moment Frames
10. Composite Intermediate Moment Frames
11. Composite Ordinary Moment Frames
AISC 341-10
Chapter Reorganization
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H. Composite Braced-Frame and Shear Wall Systems
H2. Composite Special Concentrically Braced Frames
H1. Composite Ordinary Braced Frames
H3. Composite Eccentrically Braced Frames
AISC 341-05 - Part II
12. Composite Special Concentrically Braced Frames
13. Composite Ordinary Braced Frames
14. Composite Eccentrically Braced Frames
AISC 341-10
Chapter Reorganization
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H. Composite Braced-Frame and Shear Wall Systems
H4. Composite Partially Restrained Moment Frames
H5. Composite Special Moment Frames
H6. Composite Intermediate Moment Frames
AISC 341-05 - Part II
15. Ordinary Reinforced Concrete Shear Walls Composite with Structural Steel Elements
16. Special Reinforced Concrete Shear Walls Composite with Structural Steel Elements
17. Composite Steel Plate Shear Walls
AISC 341-10
Chapter Reorganization
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AISC 341-05 - Part II
18. Structural Design Drawings and Specifications, Shop Drawings, and Erection Drawings
AISC 341-10
A. General Requirements
I. Fabrication and Erection
19. Quality Assurance Plan J. Quality Control and Quality Assurance
Chapter Reorganization
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Structural System Chapters: E - H
Consistent organization of system requirements
1. Scope
2. Basis of Design
Intended response/inelasticity
3. Analysis
4. System Requirements
Stability Bracing
Moment Ratio for SMF
Special Configurations (V- or Inverted V-Bracing)
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Structural System Chapters: E - H
Consistent organization of system requirements
5. Member Requirements
Width-to-thickness limitations
Protected Zone
6. Connections
Demand Critical welds
Column Splices
Required Connection Strengths
7. Additional requirements
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ROADMAP
Chapter Reorganization
General
• Applicable Building Code
• Demand Critical Welds
• Amplified Seismic Loads
Members
Connections
Moment Frames
Braced Frames
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A. General Requirements
A1. Scope
• “These Provisions shall apply… unless specifically exempted by the applicable building code.”
• Applies to buildings and “other structures”
“Other structures” are designed, fabricated and erected like buildings with vertical and lateral systems similar to buildings
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Including Supplement No. 1
Applicable Building Code
AISC 341-05
Including Supplement No. 1
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Including Supplement No. 1
Applicable Building Code
AISC 341-05
Including Supplements No. 1 and No. 2
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Applicable Building Code
Loads and load combinations
Systems and limitations
Design requirements
Requirements for steel design codes
AISC 360-10 AISC 341-10
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ASCE 7-10 Table 12.2-1
AISC 341 NOT required
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Demand Critical Welds
A. General Requirements
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A. General Requirements
Demand Critical Weld Requirements
System
Column Beam Flange
to Column
Flange
Beam Web/Shear
Plate to Column
FlangeBases Splices
OMF (E1.6a.) ---- ---- CJP CJP
IMF (E2.6a.) All Types Groove CJP CJP
SMF (E3.6a.) All Types Groove CJP CJP
STMF (E4.6a.) All Types Groove ---- ----
OCCS (E5.6a.) ---- ---- ---- ----
SCCS (E6.6a.) All Types Groove ---- ----
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A. General Requirements
Demand Critical Weld Requirements
SystemColumn Link Flange or
Web to Column
Built-up Link:
Web to FlangeBases Splices
OCBF (F1) ---- ---- ---- ----
SCBF (F2.6a.) All Types Groove ---- ----
EBF (F3.6a.) All Types Groove All Types All Types
BRBF (F4.6a.) All Types Groove ---- ----
SPSW (F5.6a.) All Types Groove ---- ----
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B. General Design Requirements
B2. Load and Load Combinations
12.4.3 Seismic Load Combinations Including Overstrength FactorEm = Emh + Ev
= ΩΩΩΩ0QE ± 0.2SDSD
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B. General Design Requirements
B2. Load and Load Combinations (with Amplified Seismic Loads)
AISC 341-10 Provisions
Emh in ASCE 7 Section 12.4.3
Requires “Amplified Seismic Load”
Ω0QE
Defines EDefines Emh
Capacity Analysis
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B. General Design Requirements
AISC 341-05:
• Defines E (neglects vertical effect)
• E = Em = Emh + 0
AISC 341-10:
• Defines Emh
• Em = Emh + Ev = Emh + 0.2SDSD
B2. Load and Load Combinations (with Amplified Seismic Loads)
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C. Analysis
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C. Analysis
• C1. General Requirements:
Analysis shall conform to the applicable building code
Elastic analysis of composite systems shall consider cracked sections
• C2. Additional Requirements:
Additional analysis as required for each structural system shall be performed
• C3. Nonlinear Analysis:
When used, nonlinear analysis shall conform to Chapter 16 of ASCE 7
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BREAK!
If you are encountering technical difficulties, please call (847) 991-2700
If you have any questions, please type them in
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Question and Answer Session
If you are encountering technical difficulties, please call (847) 991-2700
If you have any questions, please type them in
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ROADMAP
Chapter Reorganization
General
Members
• Ductility Classification
• Required Axial Strength of Columns
Connections
Moment Frames
Braced Frames
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D1. General Member Requirements
D1.1 Classifications of Sections for Ductility
• D1.1b Width-to-Thickness Limitations
Highly Ductile
Moderately Ductile
• D1.2 Stability Bracing of Beams
Highly Ductile
Moderately Ductile
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D1. General Member Requirements
D1.1b Width-to-Thickness Limitations
• Highly Ductile
replaces Seismically Compact (AISC 341-05)
• Moderately Ductile
replaces Compact (AISC 360-05)
Courtesy of S. MahinU.C. Berkeley, 2004
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AISC 341-05: Seismically Compact
Footnotes indicated to which members and structural systems each row applies
Type of member
force
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AISC 341-05: Compact
Type of member
force
AISC 360-05Compact Limits
Compact does not apply for Uniform Compression
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D1.1b Width-to-Thickness Limitations
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D1.1b Width-to-Thickness Limitations
D1.1b Width-to-Thickness Limitations
• Limits are based on:
Element type (flange, web, etc.)
Section type (I-shaped, HSS, etc)
Member type (beam, column, brace)
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D1.1b Width-to-Thickness Limitations: Table D1.1
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D1.1b Width-to-Thickness Limitations
Member ductility classificationSystem Beam Column Brace Link
OMF (E1) --- --- --- ---
IMF (E2.5a) Moderately Moderately --- ---
SMF (E3.5a) Highly Highly --- ---
OCBF (F1.5a) --- ---SeismicallyCompact
Moderately---
SCBF (F2.5a) Moderately Highly Highly ---
EBF (F3.5a) Moderately Highly Moderately Highly
BRBF (F4.5a) Highly Highly --- ---
SPSW (F5.5a) Highly Highly --- ---
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Beams and columns: b/t limit comparison
*Includes flanges of built-up I-shapes, channels and tees; legs of single angles or double angles with separators; outstanding legs in pairs of angles in continuous contact
**Includes webs of channels and built-up I-shapes
D1.1b Width-to-Thickness Limitations: Highly Ductile
Table indicates factor on √(E/Fy)
ElementAISC 341-05
Seismically CompactAISC 341-10
Highly Ductile
Flanges of I-Shapes* 0.30 0.30
Web of I-Shapes**
Ca ≤ 0.1253.14(1-1.54Ca)
Ca ≤ 0.1252.45(1-0.93Ca)
Ca > 0.1251.12(2.33-Ca) ≥ 1.49
Ca > 0.1250.77(2.93-Ca) ≥ 1.49
SMFFlanges of Boxed I-Shaped and Built-Up Box Columns
NA 0.60
0.30√(E/Fy)
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D1.1b Width-to-Thickness Limitations: Highly Ductile
W18X40λλλλ = 2.11
W18X65λλλλ = 1.48
Fy = 50 ksi
Ca = Pu/(φcPy) (LRFD)Ca = (ΩcPa)/Py (ASD)
Webs of I-Shaped Beams and Columns: Highly Ductileλλ λλ h
d/√
(E/F
y)
3.14
2.52.452.16
1.49
2010: Highly Ductile
2005: Seismically Compact
2005: Seismically Compact for Flexure of SMF Beams
0.125 1.0(b/t)
√(E/Fy)λλλλ =
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D1.1b Width-to-Thickness Limitations: Highly Ductile SCBF braces : b/t ratio limit comparison
*Includes flanges of built-up I-shapes, channels and tees; legs of single angles or double angles with separators; outstanding legs in pairs of angles in continuous contact
**Includes webs of channels and built-up I-shapes
***Includes walls built-up box sections and side plates of boxed I-shaped sections
Table indicates factor on √(E/Fy)
ElementAISC 341-05
Seismically CompactAISC 341-10
Highly DuctileFlanges of I-Shapes* 0.30 0.30
Webs of I-Shapes**
Ca ≤ 0.1253.14(1-1.54Ca) 1.49
Ca > 0.1251.12(2.33-Ca) ≥ 1.49
Rect. HSS Walls*** 0.64 0.55
Rnd. HSS Walls 0.044 0.038
Stems of tees 0.30 0.30
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D1.1b Width-to-Thickness Limitations: SCBF Braces
Fy = 50 ksi
Ca = Pu/(φcPy) (LRFD)Ca = (ΩcPa)/Py (ASD)
Webs of I-Shaped Braces: Highly Ductileλλ λλ h
d/√
(E/F
y)
3.14
2.50
1.49
2010: Highly Ductile
2005: Seismically Compact
0.125 1.0
W10X17λλλλ = 1.53
W12X45λλλλ = 1.21
(b/t)
√(E/Fy)λλλλ =
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Beams and columns: b/t ratio limit comparison
*Includes flanges of built-up I-shapes, channels and tees; legs of single angles or double angles with separators; outstanding legs in pairs of angles in continuous contact
**Includes webs of channels and built-up I-shapes
D1.1b Width-to-Thickness Limitations: Moderately Ductile
Table indicates factor on √(E/Fy)
ElementAISC 360-05“Compact”
AISC 341-10Moderately Ductile
Flanges of I-Shapes*0.38 (Flexure)
0.56 (Compression)0.38
Web of I-Shapes**1.49 (Compression)
3.76 (Flexure)
Ca ≤ 0.1253.76(1-2.75Ca)
Ca > 0.1251.12(2.33-Ca) ≥ 1.49
IMFFlanges of Boxed I-Shaped and Built-Up Box Columns
NA 0.55
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D1.1b Width-to-Thickness Limitations: Moderately Ductile
Fy = 50 ksi
Ca = Pu/(φcPy) (LRFD)Ca = (ΩcPa)/Py (ASD)
Webs of I-Shaped Beams and Columns: Moderately Duct ileλλ λλ h
d/√
(E/F
y)3.76
2.50
1.49
2010: Moderately Ductile
2005: NonCompact for Compression
0.125 1.0
2005: Compact for Flexure
W18X40λλλλ = 2.11
W18X65λλλλ = 1.48
(b/t)
√(E/Fy)λλλλ =
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D1.1b Width-to-Thickness Limitations: Moderately Ductile
EBF braces : b/t ratio limit comparison
*Includes flanges of built-up I-shapes, channels and tees; legs of single angles or double angles with separators; outstanding legs in pairs of angles in continuous contact
**Includes webs of channels and built-up I-shapes
***Includes walls built-up box sections and side plates of boxed I-shaped sections
Table indicates factor on √(E/Fy)
ElementAISC 360-05“Compact”
AISC 341-10Moderately Ductile
Flanges of I-Shapes*0.38 (Flexure)
0.56 (Compression)0.38
Webs of I-Shapes**1.49 (Compression)
3.76 (Flexure)1.49
Rect. HSS Walls*** 1.12 0.64
Rnd. HSS Walls0.07 (Flexure)
0.11 (Compression)0.044
Stems of tees 0.75 0.38
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D1.1b Width-to-Thickness Limitations: OCBF Braces
OCBF braces : b/t ratio limit comparison:
*Includes flanges of built-up I-shapes, channels and tees; legs of single angles or double angles with separators; outstanding legs in pairs of angles in continuous contact
**Includes webs of channels and built-up I-shapes
Table indicates factor on √(E/Fy)
ElementAISC 341-05
Seismically CompactAISC 341-10
Moderately DuctileFlanges of I-Shapes* 0.30 0.38
Webs of I-Shapes*
Ca ≤ 0.1253.14(1-1.54Ca) 1.49
Ca > 0.1251.12(2.33-Ca) ≥1.49
Rect. HSS Walls 0.64 0.64Rnd. HSS Walls 0.044 0.044Stems of tees 0.30 0.38
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D1.1b Width-to-Thickness Limitations: OCBF Braces
Fy = 50 ksi
Ca = Pu/(φcPy) (LRFD)Ca = (ΩcPa)/Py (ASD)
Webs of I-Shaped Braces: OCBF – Moderately Ductile
λλ λλ hd/√
(E/F
y)
3.14
2.50
1.49
2010: Moderately Ductile
2005: Seismically Compact
0.125 1.0
W12X26λλλλ = 1.96
W12X35λλλλ = 1.48
(b/t)
√(E/Fy)λλλλ =
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D1. General Member Requirements
D1.2 Stability Bracing of Beams
• Maximum unbraced length for Highly Ductile and Moderately Ductile beams
• Strength and stiffness of braces per Appendix 6 of AISC 360
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D1.2 Stability Bracing of Beams
Maximum unbraced length of beams
*Beams in V or Inverted-V systems only
Member AISC 341-05, L b AISC 341-10, L b
SMF Beams (E2.4a) 0.086ry(E/Fy)Highly Ductile
0.086ry(E/Fy)
IMF Beams (E3.4b)
SPSW HBE (F5.4c)0.17ry(E/Fy)
Moderately Ductile
0.17ry(E/Fy)
SCBF Beams* (F2.4b)
BRBF Beams* (F4.4a)[0.12+0.076(M1/M2)](E/Fy)ry
Moderately Ductile
0.17ry(E/Fy)
OCBF Beams* (F1) [0.12+0.076(M1/M2)](E/Fy)ry NONE
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D1.2 Stability Bracing of Beams
Beams in V- or Inverted V-Braced Frames
M1/M2
L b/[(
E/F
y)r y
]
AISC 341-05 (Appendix 1 of AISC 360-05)Lb = [0.12+0.076(M1/M2)](E/Fy)ry
AISC 341-10: Moderately DuctileLb = 0.17(E/Fy)ry
0.196
0.120
0.044
-1.0 1.000
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D1.4 Columns
All SFRS columns now are required to use amplified seismic load combinations to determine Pr in the absence of moments
AISC 341-05LRFD
Pu/φcPn > 0.4
ASDΩcPa/Pn > 0.4
Amplified Seismic Load Combinations
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ROADMAP
Chapter Reorganization
General
Members
Connections
• Column Splices
• Column Bases/Anchorage
Moment Frames
Braced Frames
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D2.5. Column Splices: SFRS
Seismic Force Resisting Column Splices:
• Increased required strength
• More restrictions on partial joint penetration groove welds (PJP)
• “Push” towards complete joint penetration groove welds (CJP)
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D2.5. Column Splices: SFRS
D2.5b. Required Strength: largest of
• Required strength of the column
• Effect of amplified seismic loads
• Structural system requirements
D2.5c. Required Shear Strength: greater of
• Required strength from D2.5.b
• Mpc/H (LRFD) or Mpc/(1.5H) (ASD)
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SFRS Column Splices: Table Notes
Mr, Vr, Pr are required strengths of the splice
Mpc = lesser nominal plastic flexural strength
Mn = lesser nominal flexural strength
ΣMpc = sum of nominal plastic flexural strengths
H = story height
Hc = clear story height
Ω0E = Effect of Amplified Seismic Load Combinations
Mr_col, Vr_col, Pr_col are required strengths of the column
Special additional requirements apply for splices i n net tension
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D2.5 Column SplicesRequired Strength for SFRS: LRFD
System Welds
Mr Vr Pr
Largest of Mr_col,
Ω0E, and
Largest of Vr_col,
Ω0E, Mpc/H, and
Largest of
Pr_col, Ω0E, and
OMF (E1) ---- ---- ---- ----
IMF (E2.6g) No PJP Bolted: RyFyZx ΣMpc/H ----
SMF (E3.6g) No PJP Bolted: RyFyZx ΣMpc/H ----
STMF (E4.6c) No PJP Bolted: RyFyZx ΣMpc/H ----
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D2.5 Column SplicesRequired Strength for SFRS: LRFD
System Welds
Mr Vr Pr
Largest of Mr_col,
Ω0E, and
Largest of Vr_col,
Ω0E, Mpc/H, and
Largest of
Pr_col, Ω0E, and
OCBF (F1) ---- ---- ---- ----
SCBF (F2.6d) No PJP φMn/2 ΣMpc/Hc ----
EBF (F3.6d) No PJP φMn/2 ΣMpc/Hc ----
BRBF (F4.6d) No PJP φMn/2 ΣMpc/Hc ----
SPSW (F5.6d) No PJP φMn/2 ΣMpc/Hc ----
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D2.5 Column SplicesRequired Strength for SFRS: ASD
System Welds
Mr Vr Pr
Largest of Mr_col,
Ω0E, and
Largest of Vr_col,
Ω0E, Mpc/(1.5H),
and
Largest of
Pr_col, Ω0E, and
OMF (E1) ---- ---- ---- ----
IMF (E2.6g) No PJP Bolted: RyFyZx/1.5 ΣMpc/(1.5H) ----
SMF (E3.6g) No PJP Bolted: RyFyZx/1.5 ΣMpc/(1.5H) ----
STMF (E4.6c) No PJP Bolted: RyFyZx/1.5 ΣMpc/(1.5H) ----
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D2.5 Column SplicesRequired Strength for SFRS: ASD
System Welds
Mr Vr Pr
Largest of Mr_col,
Ω0E, and
Largest of Vr_col,
Ω0E, Mpc/(1.5H),
and
Largest of
Pr_col, Ω0E, and
OCBF (F1) ---- ---- ---- ----
SCBF (F2.6d) No PJP Mn/2Ω ΣMpc/(1.5Hc) ----
EBF (F3.6d) No PJP Mn/2Ω ΣMpc/(1.5Hc) ----
BRBF (F4.6d) No PJP Mn/2Ω ΣMpc/(1.5Hc) ----
SPSW (F5.6d) No PJP Mn/2Ω ΣMpc/(1.5Hc) ----
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D2.6 Column Bases
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D2.6 Column Bases: SFRS
D2.6a Required Axial Strength: Sum of vertical components:
• Braces: required member connection strength
• Columns: greater of
Required member strength
Axial load from Ω0E combinations
Required axial strength of column splices
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Axial: OCBF or SCBF - LRFD
D2.6 Column Bases: SFRS
T = RyFYAg orC = 1.1(1.14FcreAg)
Pr_col≥ ΩΩΩΩ0E
Pr = Σ vertical components
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D2.6 Column Bases: SFRS
T = RyFYAg
Pr_col≥ ΩΩΩΩ0EC = 0.3[(1.14FcreAg)]
Axial: SCBF w/ Compression Buckling - LRFD
Pr = Σ vertical components
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D2.6 Column Bases: SFRSLRFD Example
Example member vs. connection required strength
• SCBF: A500 Gr B; Fy = 46 ksi; Ry = 1.4; KL = 19 ft
• Ω0 = 2 for SCBF
Brace KL/r φPn RyFyAg (RyFyAg)/φPn
HSS8x8x5/8 76.3 459 kips 1056 kips 2.30
HSS6x6x1/2 102 200 kips 627 kips 3.14
HSS4x4x5/16 163 39.6 kips 264 kips 6.66
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D2.6 Column Bases: SFRS
D2.6b Required shear strength: Sum of horizontal components:
• Braces: required connection strength
• Columns: greater of
Shear load from Ω0E combinations
2RyFyZx/H (LRFD) (2/1.5)RyFyZx/H (ASD)
Required shear strength of column splices
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D2.6 Column Bases: SFRS
D2.6b Required Shear Strength - LRFD
System
AISC 341-05 (8.5b) AISC 341-10
Lesser of2RyFyZx/H, Ω0E, and
Greatest of Vr_col, Ω0E,
Mpc/H, and
OMF (E1), OCBF (F1) ---- ----
IMF (E2.6g), SMF (E3.6g),
STMF (E4.6c)---- ΣMpc/H
SCBF (F2.6d), EBF (F3.6d),
BRBF (F4.6d), SPSW (F5.6d)---- ΣMpc/Hc
ΣMpc/Hc = Mpc/Hc = FyZx/Hc ≤ 2RyFyZx/H
Mpc/Hc ≥ ΩΩΩΩ0E
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D2.6 Column Bases: SFRS
T = RyFYAg
Largest ofVr_col , ΩΩΩΩ0EMpc/Hc
C = 1.1(1.14FcreAg)
Shear: SCBF - LRFD
Vr = Σ horizontal components
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D2.6 Column Bases: SFRS
D2.6b Required Shear Strength - ASD
System
AISC 341-05 (8.5b) AISC 341-10
Lesser of(2/1.5)RyFyZx/H, Ω0E
Greatest of Vr_col, Ω0E,
Mpc/(1.5H)
OMF (E1), OCBF (F1) ---- ----
IMF (E2.6g), SMF (E3.6g),
STMF (E4.6c)---- ΣMpc/(1.5H)
SCBF (F2.6d), EBF (F3.6d),
BRBF (F4.6d), SPSW (F5.6d)---- ΣMpc/(1.5Hc)
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D2.6 Column Bases: SFRS
D2.6c Required Flexural Strength: Sum of flexural components:
• Braces: required connection strength
• Columns: lesser of
1.1RyFyZ (LRFD) or (1.1/1.5) RyFyZ (ASD)
Moment from Ω0E combinations
• User Note: Ignore moments for pinned bases
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D2.6 Column Bases: Non-SFRS
D2.6b Required Shear Strength: Non-SFRS Columns:
• Required shear strength of column splices
Mpc/H (LRFD) or Mpc/(1.5H) (ASD)
Vr
Mpc
Vr
- 86 -
D2.6 Column Bases: Anchorage
AISC 360 and 341
ACI 318 Appendix D
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D2.6 Column Bases: Anchorage
AISC 341-10 Section D2.6
• Exception: “The special requirements in ACI 318, Appendix D for regions of moderate or high seismic risk, or for structures assigned to intermediate or high seismic performance or design categories need not apply”.
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*ACI 318-11 no longer applies a 0.75 factor on shear strength
AISC 341 and ACI 318 Appendix D.
Design for AISC 341 Required Strengths
Codes and
Standards
0.75 Strength Factor
(0.75φNn)
Ductility Requirements
Appendix D.
AISC 341-05
2006 IBC: ACI 318-05
2009 IBC: ACI 318-08
D.3.3.3Exempted
D.3.3.4Exempted
AISC 341-10
2012 IBC: ACI 318-11
D.3.3.4.4 – Tension*:
Applied to concrete
failure modes
D.3.3.4.3 - Tension:
Option (c) or (d) satisfied
D.3.3.5.3 – Shear:
Option (b) or (c) satisfied
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BREAK!
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- 90 -
Question and Answer Session
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- 91 -
ROADMAP
Chapter Reorganization
General
Members
Connections
Moment Frames
• Prequalified Connections
• Cantilever Column Systems
Braced Frames
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E. Moment-Frame Systems
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E. Moment-Frame Systems
Summary of changes
• Ordinary Moment Frames
Text revised to allow use of non wide-flange members
Continuity plate requirements removed (E1.6b.)
• Intermediate and Special Moment Frames
Prequalified connections added to AISC 358-10
• Ordinary Cantilever Column Systems (OCCS) added
• Special Cantilever Column Systems (SCCS) added
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Prequalified ConnectionsAISC 358-10
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Prequalified ConnectionsAISC 358-10
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Extended End-Plate
Prequalified ConnectionsAISC 358-05Reduced Beam Section
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Welded Unreinforced Flange – Welded Web (WUF-W)
Prequalified ConnectionsAISC 358-05 with Supplement No. 1Bolted Flange Plate
- 98 -
Prequalified ConnectionsAISC 358-05 with Supplement No. 1Kaiser Bolted Bracket ™
By Steel Cast Connections, LLC
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Conxtech® CONXL™
Prequalified ConnectionsAISC 358-10 with Supplement No. 1
By ConXtech Inc.
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E5 and E6. Cantilever Column Systems
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Cantilever Column Systems
New to AISC 341-10
ASCE 7-10:
• Table 12.2-1:
OCCS: R= 1.5, Limited to 35 ft and SDC B and C
SCCS: R = 2.5, Limited to 35 ft in all SDC
• 12.2.5.2:
Required axial strength for seismic load combinations, shall not exceed 15% of available axial strength, Pr ≤ 0.15Pc
Foundations used for overturning resistance shall be designed to resist amplified seismic load combinations
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E5. Ordinary Cantilever Column Systems
E5.2. Provides minimal inelastic drift capacity through flexural yielding of the columns
Flexural yielding of columns
• E5.4a. Axial Load
Based on amplified seismic load combinations
For seismic load combinations, Prc ≤ 0.15Pc
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E6. Special Cantilever Column Systems
E6.2. Provides limited inelastic drift capacity through flexural yielding of the columns
Flexural yielding of columns• E6.4a. Axial Load
Based on amplified seismic load combinations
For seismic load combinations, Prc ≤ 0.15Pc
• E6.4b. Unbraced length: Moderately Ductile
• E6.5a. b/t limitations: Highly Ductile
• E6.5c. Protected Zone: 2dc from column base
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ROADMAP
Chapter Reorganization
General
Members
Connections
Moment Frames
Braced Frames
• Connection Deformation Compatibility
• Capacity Analysis
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F. Braced-Frame and Shear-Wall Systems
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F. Braced-Frame and Shear-Wall Systems
Summary of Changes
• Ordinary Concentrically Braced Frames
F1.4b. K-Braced frames prohibited
• Special Concentrically Braced Frames
F2.3. Analysis requirements added
F2.6b. Connection deformation compatibility requirement added
F2.5b(1). Brace slenderness ratio limit relaxed from Kl/r ≤ 4√(E/Fy) to Kl/r ≤ 200
F2.5b(3). Effective net area requirements for braces edited
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F. Deformation Compatibility
F2.6b. Beam-to-Column Connections: Brace connects to beam and column
• Provide “simple” connection per B3.6a. of AISC 360
• Design connection for Mr; lesser of:
1.1RyMp_bm (LRFD) or (1.1/1.5)RyMp_bm (ASD)
Σ1.1RyFyZcol (LRFD) or Σ(1.1/1.5)RyFyZcol (ASD)
Welds are Demand Critical
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F. Deformation Compatibility
Provide “simple” connection per B3.6a. of AISC 360
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F2. Special Concentrically Braced Frames
F2.3. Analysis
• Determine required strengths of beams, columns, and connections using capacity analysis
• Capture large forces caused by post-elastic behavior of braces
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F2.3. SCBF Analysis
Two analyses to determine Emh
1. Expected strength
Brace in Tension - consider expected strength
Brace in Compression - consider expected strength
2. Post-Buckling strength
Brace in Tension - consider expected strength
Brace in Compression - consider post-buckling strength
• It is permitted to neglect flexural forces resulting from seismic drift.
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F2.3. SCBF Analysis
Braces in Tension or Compression?
• Neglect the effects of gravity loads
• Consider only the first mode of deflection
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Expected Strength
Expected strength in compression:
Cexp = Min RyFyAg1.14Fcre
Expected strength in tension:Texp = RyFyAg
Fcre = Fcr with RyFy
F2.3. SCBF Expected Strength Analysis
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Expected StrengthElastic
Compression
Tension
F2.3. SCBF Expected Strength Analysis
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F2.3. SCBF Expected Strength Analysis
Expected StrengthElastic
Shear
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Post-Buckling
Post-Buckling strength in compression:
Cpb = 0.3*Min RyFyAg1.14Fcre
Expected strength in tension:Texp = RyFyAg
Fcre = Fcr with RyFy
F2.3. SCBF Post-Buckling Analysis
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F2.3. SCBF Post-Buckling Analysis
Post-BucklingElastic
Compression
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F2.3. SCBF Post-Buckling Analysis
Compression
Uplift
- 118 -
F2.3. SCBF Post-Buckling Analysis
Unbalanced shear force
AISC 341-05 considered this force
Post-Buckling
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F3. Eccentrically Braced Frames
- 120 -
F3. Eccentrically Braced Frames
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F. Braced-Frame and Shear-Wall Systems
Summary of Changes
• Eccentrically Brace Frames
F3.3. Analysis requirements revised
F3.5b(1). Built-up box sections allowed (no HSS)
F3.6b. Connection deformation compatibility requirement added
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F3. Eccentrically Braced Frames
F3.3 Analysis
• Emh = forces in beams, columns, braces, and connections when ALL links reach their adjusted shear strength
• Adjusted shear strength
I-shaped links: 1.25RyVn
Box links: 1.40RyVn
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F3. Eccentrically Braced Frames
I-Shapes: 1.25RyVnor
Boxes: 1.40RyVn
Determine forces in beams, columns,
braces, and connections
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F3. Eccentrically Braced Frames
F3.3 Analysis
• Permitted to take Emh = 0.88 times forces from analysis for:
Beams outside link
Columns in frames with 3 or more stories
• Permitted to neglect effects of seismic drifts on the moments
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F3. Eccentrically Braced Frames
Required Strength in AISC 341-05
• 15.6a. Diagonal Brace
E = forces in brace when shear in link reaches 1.25RyVn
• 15.6b. Beam Outside Link
E = forces in brace when shear in link reaches 1.1RyVn
• 15.8. Columns
E = forces in brace when shear in link reaches 1.1RyVn in ALL levels above the column
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F3. Eccentrically Braced Frames
Effective shear in links
ElementAISC 341-05
I-Shaped Links
AISC 341-10
I-Shaped Links
AISC 341-10
Box Links
Braces 1.25RyVn 1.25RyVn 1.40RyVn
Beams 1.10RyVn0.88*(1.25RyVn) =
1.10RyVn
0.88*(1.40RyVn) = 1.23RyVn
Columns < 3
stories1.10RyVn 1.25RyVn 1.40RyVn
Columns ≥ 3
stories1.10RyVn
0.88*(1.25RyVn) = 1.10RyVn
0.88*(1.40RyVn) = 1.23RyVn
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F3. Eccentrically Braced Frames
Required Strength in AISC 341-05
• 15.4 Link-to-Column Connections
Must be tested or prequalified
• 15.6c. Bracing Connections
At least required strength of brace (when shear in link reaches 1.25RyVn)
• 15.7. Beam-to-Column Connections
At least required strength of beam (when shear in link reaches 1.1RyVn)
If moment connection, meet OMF requirements
- 128 -
F3. Eccentrically Braced Frames
Required Connection Strengths
• F3.3. Required connection strengths are determined from the same capacity analysis as the members
• F3.6e. Link-to-Column connections
Must be tested or prequalified
• Beam-to-column moment connections must meet OMF requirements
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F. Braced-Frame and Shear-Wall Systems
Summary of Changes
• Buckling-Restrained Braced Frames
F4.3. Analysis requirements added
F4.6b. Connection deformation compatibility requirement added
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F. Braced-Frame and Shear-Wall Systems
Summary of Changes
• Special Plate Shear Walls
F5.4a. Horizontal Boundary Element stiffness minimum added
F5.4b. Beam-Column moment ratio limit added
F5.5c. Protected Zones added
F5.7. Requirements for perforated webs and corner cut-outs added
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Key Points
Reorganized chapters for consistency with AISC 360
Increased protection of critical locations
Added new systems and connections
Provided consistent capacity analysis requirements
- 132 -
Resources
Download AISC 341-10 FREE from www.aisc.org/FreePubs
• Commentary to AISC 341-10
Download AISC 358-10 FREE from www.aisc.org/FreePubs
AISC Steel Solutions Center
• Free technical support email: solutions@aisc.org
2010 AISC T.R. Higgins Award Lecture by James O. Malley
• “The AISC Seismic Provisions: Past, Present, and Future”
• http://www.aisc.org/content.aspx?id=572
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Resources
The AISC Seismic Design Manual , 2nd, Edition
www.aisc.org/Store
- 134 -
Question and Answer Session
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Thank You!!
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