S. K. Ghosh Associates Inc.
CHANGES in AISC’s SEISMIC PROVISIONS: AISC 341-05 to AISC 341-10 S. K. Ghosh Associates Inc. Palatine, IL and Aliso Viejo, CA www.skghoshassociates.com
-1-
AISC Seismic Provisions AISC Seismic Provisions provide System Ductility
-2-
www.skghoshassociates.com 1
S. K. Ghosh Associates Inc.
System Ductility “System Ductility” is the ability of system to maintain stability after yielding/overload of some elements • Ability of yielding/overloaded elements to deform V
• Ability of non-yielding elements to withstand forces redistributed by yielding
Ductility
• Ability of non-yielding elements to withstand deformations caused by yielding
∆
-3-
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
-4-
www.skghoshassociates.com 2
S. K. Ghosh Associates Inc.
Seismic Provisions Measures Identify target yield mechanism of the system Shear Yield Flexural Yield
Tension yield and compression buckling -5-
Seismic Provisions Measures Designate deformation-controlled elements • Design for element ductility
Stable yield
M
θ -6-
www.skghoshassociates.com 3
S. K. Ghosh Associates Inc.
Seismic Provisions Measures Design remaining elements as force-controlled • Design to keep members essentially elastic at capacity of ductile elements
Resist redistributed forces
-7-
Seismic Provisions Measures Design remaining elements as force-controlled • Design for deformations caused by yielding
Accommodate deformations
-8-
www.skghoshassociates.com 4
S. K. Ghosh Associates Inc.
Seismic Provisions Measures Protect critical locations Protected Zones
Demand Critical Welds
Amplify forces -9-
Key Points Reorganized chapters for consistency with AISC 360 Increased protection of critical locations Added new systems and connections Provided consistent capacity analysis requirements
- 10 -
www.skghoshassociates.com 5
S. K. Ghosh Associates Inc.
ROADMAP Chapter Reorganization General Members Connections Moment Frames Braced Frames
- 11 -
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 Part II: Composite Systems
7: Connections, Joints, and Fasteners 8: Members 9-17: Structural Systems 18: Quality Assurance Plan (Appendix Q) Appendices P, R, S, T, W, X - 12 -
www.skghoshassociates.com 6
S. K. Ghosh Associates Inc.
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 - 13 -
Chapter Reorganization Preface to AISC 341-10
- 14 -
www.skghoshassociates.com 7
S. K. Ghosh Associates Inc.
Chapter Reorganization AISC 341-05 - Part I
AISC 341-10
1. Scope
A. General Requirements
2. Referenced Specifications, Codes, and Standards 3. General Seismic Design
B. General Design Requirements
4. Loads, Load Combinations, Nominal Strengths 5. Structural Drawings and Specifications, Shop Drawings, and Erection Drawings
A. General Requirements I. Fabrication and Erection
6. Materials - 15 -
Chapter Reorganization AISC 341-05 - Part I
AISC 341-10
7. Connections, Joints, and Fasteners
D. General Member and Connection Design Requirements I. Fabrication and Erection
7.3b. Demand Critical Welds
A. General Requirements A3.4b.
8. Members
AWS D1.8
D. General Member and Connection Design Requirements
- 16 -
www.skghoshassociates.com 8
S. K. Ghosh Associates Inc.
Chapter Reorganization AISC 341-05 - Part I
AISC 341-10 E. Moment-Frame Systems
9. Special Moment Frames
E3. Special Moment Frames
10. Intermediate Moment Frames
E2. Intermediate Moment Frames
11. Ordinary Moment Frames
E1. Ordinary Moment Frames
12. Special Truss Moment Frames
E4. Special Truss Moment Frames E5. Ordinary Cantilever Column Systems E6. Special Cantilever Column Systems - 17 -
Chapter Reorganization AISC 341-05 - Part I
AISC 341-10 F. Braced-Frame and ShearWall Systems
13. Special Concentrically Braced Frames
F2. Special Concentrically Braced Frames
14. Ordinary Concentrically Braced Frames
F1. Ordinary Concentrically Braced Frames
15. Eccentrically Braced Frames
F3. Eccentrically Braced Frames
16. Buckling-Restrained Braced Frames
F4. Buckling-Restrained Braced Frames
17. Special Plate Shear Walls
F5. Special Plate Shear Walls - 18 -
www.skghoshassociates.com 9
S. K. Ghosh Associates Inc.
Chapter Reorganization AISC 341-05 - Part I
AISC 341-10
18: Quality Assurance Plan (Appendix Q)
J. Quality Control and Quality Assurance
Appendix P: Connection Prequalification
K. Prequalification and Cyclic Qualification Testing Provisions
Appendix S: Qualifying Cyclic Tests of Beam-to-Column and Link-to-Column Connections Appendix T: Qualifying Cyclic Tests of BRBF Braces
- 19 -
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)
- 20 -
www.skghoshassociates.com 10
S. K. Ghosh Associates Inc.
Chapter Reorganization AISC 341-05 - Part I
AISC 341-10
Appendix R. Seismic Design Coefficients and Approximate Period Parameters
REMOVED
Appendix W: Welding Provisions
A. General Requirements A4.4a.
AWS D1.8
I. Fabrication and Erection Appendix X: Weld Metal/Welding Procedure Specification Notch Toughness Verification Test
A. General Requirements A4.4a.
AWS D1.8
- 21 -
Chapter Reorganization AISC 341-05 - Part II 1. Scope
AISC 341-10 A. General Requirements
2. Referenced Specifications, Codes, and Standards 3. General Seismic Design
B. General Design Requirements
4. Loads, Load Combinations, Nominal Strengths 5. Materials
A. General Requirements
6. Composite Members 7. Composite Connections
D. General Member and Connection Design Requirements
- 22 -
www.skghoshassociates.com 11
S. K. Ghosh Associates Inc.
Chapter Reorganization AISC 341-05 - Part II
AISC 341-10 G. Composite Moment-Frame Systems
8. Composite Partially Restrained Moment Frames
G4. Composite Partially Restrained Moment Frames
9. Composite Special Moment Frames
G3. Composite Special Moment Frames
10. Composite Intermediate Moment Frames
G2. Composite Intermediate Moment Frames
11. Composite Ordinary Moment Frames
G1. Composite Ordinary Moment Frames
- 23 -
Chapter Reorganization AISC 341-05 - Part II
AISC 341-10 H. Composite Braced-Frame and Shear Wall Systems
12. Composite Special Concentrically Braced Frames
H2. Composite Special Concentrically Braced Frames
13. Composite Ordinary Braced Frames
H1. Composite Ordinary Braced Frames
14. Composite Eccentrically Braced Frames
H3. Composite Eccentrically Braced Frames
- 24 -
www.skghoshassociates.com 12
S. K. Ghosh Associates Inc.
Chapter Reorganization AISC 341-05 - Part II
AISC 341-10 H. Composite Braced-Frame and Shear Wall Systems
15. Ordinary Reinforced Concrete Shear Walls Composite with Structural Steel Elements
H4. Composite Partially Restrained Moment Frames
16. Special Reinforced Concrete Shear Walls Composite with Structural Steel Elements
H5. Composite Special Moment Frames
17. Composite Steel Plate Shear Walls
H6. Composite Intermediate Moment Frames
- 25 -
Chapter Reorganization AISC 341-05 - Part II
AISC 341-10
18. Structural Design Drawings and Specifications, Shop Drawings, and Erection Drawings
A. General Requirements
19. Quality Assurance Plan
J. Quality Control and Quality Assurance
I. Fabrication and Erection
- 26 -
www.skghoshassociates.com 13
S. K. Ghosh Associates Inc.
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) - 27 -
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 - 28 -
www.skghoshassociates.com 14
S. K. Ghosh Associates Inc.
ROADMAP Chapter Reorganization
General • Applicable Building Code • Demand Critical Welds • Amplified Seismic Loads Members Connections Moment Frames Braced Frames - 29 -
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
- 30 -
www.skghoshassociates.com 15
S. K. Ghosh Associates Inc.
Applicable Building Code
Including Supplement No. 1
Including Supplement No. 1
AISC 341-05
- 31 -
Applicable Building Code
Including Supplements No. 1 and No. 2
Including Supplement No. 1
AISC 341-05
- 32 -
www.skghoshassociates.com 16
S. K. Ghosh Associates Inc.
Applicable Building Code Loads and load combinations Systems and limitations Design requirements Requirements for steel design codes
AISC 360-10
AISC 341-10
- 33 -
ASCE 7-10 Table 12.2-1
AISC 341 NOT required
- 34 -
www.skghoshassociates.com 17
S. K. Ghosh Associates Inc.
A. General Requirements Demand Critical Welds
- 35 -
A. General Requirements Demand Critical Weld Requirements Column System
Beam Flange
Beam Web/Shear
to Column
Plate to Column
Flange
Flange
Bases
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
----
----
- 36 -
www.skghoshassociates.com 18
S. K. Ghosh Associates Inc.
A. General Requirements Demand Critical Weld Requirements Column System
Link Flange or
Built-up Link:
Bases
Splices
Web to Column
Web to Flange
----
----
----
----
Groove
----
----
All Types
Groove
All Types
All Types
BRBF (F4.6a.) All Types
Groove
----
----
SPSW (F5.6a.) All Types
Groove
----
----
OCBF (F1)
SCBF (F2.6a.) All Types EBF (F3.6a.)
- 37 -
B. General Design Requirements B2. Load and Load Combinations
12.4.3 Seismic Load Combinations Including Overstrength Factor
Em = Emh + Ev = Ω0QE ± 0.2SDSD
- 38 -
www.skghoshassociates.com 19
S. K. Ghosh Associates Inc.
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 E Defines Emh
Capacity Analysis
- 39 -
B. General Design Requirements B2. Load and Load Combinations (with Amplified Seismic Loads) AISC 341-05:
AISC 341-10:
• Defines E (neglects vertical effect)
• Defines Emh • Em = Emh + Ev = Emh + 0.2SDSD
• E = Em = Emh + 0
- 40 -
www.skghoshassociates.com 20
S. K. Ghosh Associates Inc.
C. Analysis
- 41 -
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
- 42 -
www.skghoshassociates.com 21
S. K. Ghosh Associates Inc.
BREAK!
If you have any questions, please type them in
If you are encountering technical difficulties, please call (847) 991-2700 - 43 -
Question and Answer Session If you have any questions, please type them in
If you are encountering technical difficulties, please call (847) 991-2700
- 44 -
www.skghoshassociates.com 22
S. K. Ghosh Associates Inc.
ROADMAP Chapter Reorganization General
Members • Ductility Classification • Required Axial Strength of Columns Connections Moment Frames Braced Frames
- 45 -
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
- 46 -
www.skghoshassociates.com 23
S. K. Ghosh Associates Inc.
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. Mahin U.C. Berkeley, 2004
- 47 -
AISC 341-05: Seismically Compact
Type of member force
Footnotes indicated to which members and structural systems each row applies - 48 -
www.skghoshassociates.com 24
S. K. Ghosh Associates Inc.
AISC 341-05: Compact AISC 360-05 Compact Limits
Type of member force
Compact does not apply for Uniform Compression - 49 -
D1.1b Width-to-Thickness Limitations
- 50 -
www.skghoshassociates.com 25
S. K. Ghosh Associates Inc.
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)
- 51 -
D1.1b Width-to-Thickness Limitations: Table D1.1
- 52 -
www.skghoshassociates.com 26
S. K. Ghosh Associates Inc.
D1.1b Width-to-Thickness Limitations Member ductility classification System
Beam
Column
Brace
Link
OMF (E1)
---
---
---
---
IMF (E2.5a)
Moderately
Moderately
---
---
SMF (E3.5a)
Highly
Highly
---
---
OCBF (F1.5a)
---
---
Seismically Compact Moderately
---
SCBF (F2.5a)
Moderately
Highly
Highly
---
EBF (F3.5a)
Moderately
Highly
Moderately
Highly
BRBF (F4.5a)
Highly
Highly
---
---
SPSW (F5.5a)
Highly
Highly
---
---
- 53 -
D1.1b Width-to-Thickness Limitations: Highly Ductile Beams and columns: b/t limit comparison Element
Table indicates factor on √(E/Fy) AISC 341-05 Seismically Compact
Flanges of I-Shapes*
Web of I-Shapes**
SMF Flanges of Boxed I-Shaped and Built-Up Box Columns
0.30√(E/Fy)
AISC 341-10 Highly Ductile
0.30
0.30
Ca ≤ 0.125 3.14(1-1.54Ca)
Ca ≤ 0.125 2.45(1-0.93Ca)
Ca > 0.125 1.12(2.33-Ca) ≥ 1.49
Ca > 0.125 0.77(2.93-Ca) ≥ 1.49
NA
0.60
*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 - 54 -
www.skghoshassociates.com 27
S. K. Ghosh Associates Inc.
D1.1b Width-to-Thickness Limitations: Highly Ductile Webs of I-Shaped Beams and Columns: Highly Ductile 2005: Seismically Compact
λ hd/√(E/Fy)
3.14
2005: Seismically Compact for Flexure of SMF Beams
2.5 2.45 2.16
Fy = 50 ksi
W18X40 λ = 2.11 W18X65 λ = 1.48
1.49 2010: Highly Ductile
λ= 0.125
Ca = Pu/(φcPy) (LRFD) Ca = (ΩcPa)/Py (ASD)
√(E/Fy) (b/t)
1.0
- 55 -
D1.1b Width-to-Thickness Limitations: Highly Ductile SCBF braces: b/t ratio limit comparison Element Flanges of I-Shapes*
Webs of I-Shapes**
Table indicates factor on √(E/Fy) AISC 341-05 Seismically Compact 0.30 Ca ≤ 0.125 3.14(1-1.54Ca) Ca > 0.125 1.12(2.33-Ca) ≥ 1.49
AISC 341-10 Highly Ductile 0.30
1.49
Rect. HSS Walls***
0.64
0.55
Rnd. HSS Walls
0.044
0.038
Stems of tees
0.30
0.30
*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 - 56 -
www.skghoshassociates.com 28
S. K. Ghosh Associates Inc.
D1.1b Width-to-Thickness Limitations: SCBF Braces Webs of I-Shaped Braces: Highly Ductile 2005: Seismically Compact
λ hd/√(E/Fy)
3.14
Fy = 50 ksi
2.50
W10X17 λ = 1.53
1.49
W12X45 λ = 1.21
2010: Highly Ductile
λ= 0.125
Ca = Pu/(φcPy) (LRFD) Ca = (ΩcPa)/Py (ASD)
√(E/Fy) (b/t)
1.0
- 57 -
D1.1b Width-to-Thickness Limitations: Moderately Ductile Beams and columns: b/t ratio limit comparison Table indicates factor on √(E/Fy) AISC 360-05 Element “Compact” 0.38 (Flexure) Flanges of I-Shapes* 0.56 (Compression)
Web of I-Shapes**
1.49 (Compression) 3.76 (Flexure)
IMF Flanges of Boxed I-Shaped and Built-Up Box Columns
NA
AISC 341-10 Moderately Ductile 0.38 Ca ≤ 0.125 3.76(1-2.75Ca) Ca > 0.125 1.12(2.33-Ca) ≥ 1.49 0.55
*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 - 58 -
www.skghoshassociates.com 29
S. K. Ghosh Associates Inc.
D1.1b Width-to-Thickness Limitations: Moderately Ductile Webs of I-Shaped Beams and Columns: Moderately Ductile 3.76 2005: Compact for Flexure
λ hd/√(E/Fy)
Fy = 50 ksi 2010: Moderately Ductile
W18X40 λ = 2.11
2.50
W18X65 λ = 1.48
1.49 2005: NonCompact for Compression
λ= 0.125
Ca = Pu/(φcPy) (LRFD) Ca = (ΩcPa)/Py (ASD)
√(E/Fy) (b/t)
1.0
- 59 -
D1.1b Width-to-Thickness Limitations: Moderately Ductile EBF braces: b/t ratio limit comparison Element Flanges of I-Shapes* Webs of I-Shapes** Rect. HSS Walls*** Rnd. HSS Walls Stems of tees
Table indicates factor on √(E/Fy) AISC 360-05 “Compact” 0.38 (Flexure) 0.56 (Compression) 1.49 (Compression) 3.76 (Flexure) 1.12 0.07 (Flexure) 0.11 (Compression)
AISC 341-10 Moderately Ductile
0.75
0.38 1.49 0.64 0.044 0.38
*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 - 60 -
www.skghoshassociates.com 30
S. K. Ghosh Associates Inc.
D1.1b Width-to-Thickness Limitations: OCBF Braces OCBF braces: b/t ratio limit comparison: Element Flanges of I-Shapes*
Webs of I-Shapes*
Rect. HSS Walls Rnd. HSS Walls Stems of tees
Table indicates factor on √(E/Fy) AISC 341-05 Seismically Compact 0.30 Ca ≤ 0.125 3.14(1-1.54Ca) Ca > 0.125 1.12(2.33-Ca) ≥1.49 0.64 0.044 0.30
AISC 341-10 Moderately Ductile 0.38
1.49
0.64 0.044 0.38
*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 - 61 -
D1.1b Width-to-Thickness Limitations: OCBF Braces Webs of I-Shaped Braces: OCBF – Moderately Ductile
λ hd/√(E/Fy)
2005: Seismically Compact
3.14
Fy = 50 ksi
2.50
W12X26 λ = 1.96 W12X35 λ = 1.48
1.49
2010: Moderately Ductile
λ= 0.125
Ca = Pu/(φcPy) (LRFD) Ca = (ΩcPa)/Py (ASD)
1.0
- 62 -
www.skghoshassociates.com 31
√(E/Fy) (b/t)
S. K. Ghosh Associates Inc.
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
- 63 -
D1.2 Stability Bracing of Beams Maximum unbraced length of beams Member
AISC 341-05, Lb
SMF Beams (E2.4a)
0.086ry(E/Fy)
IMF Beams (E3.4b) SPSW HBE (F5.4c) SCBF Beams* (F2.4b) BRBF Beams* (F4.4a) OCBF Beams* (F1)
0.17ry(E/Fy)
[0.12+0.076(M1/M2)](E/Fy)ry
AISC 341-10, Lb Highly Ductile 0.086ry(E/Fy) Moderately Ductile 0.17ry(E/Fy) Moderately Ductile 0.17ry(E/Fy)
[0.12+0.076(M1/M2)](E/Fy)ry
*Beams in V or Inverted-V systems only - 64 -
www.skghoshassociates.com 32
NONE
S. K. Ghosh Associates Inc.
D1.2 Stability Bracing of Beams Beams in V- or Inverted V-Braced Frames AISC 341-10: Moderately Ductile Lb = 0.17(E/Fy)ry
Lb/[(E/Fy)ry]
0.196
0.120
AISC 341-05 (Appendix 1 of AISC 360-05) Lb = [0.12+0.076(M1/M2)](E/Fy)ry
0.044 0
-1.0
0
1.0
M1/M2 - 65 -
D1.4 Columns All SFRS columns now are required to use amplified seismic load combinations to determine Pr in the absence of moments AISC 341-05 LRFD Pu/φcPn > 0.4
Amplified Seismic Load Combinations
ASD ΩcPa/Pn > 0.4 - 66 -
www.skghoshassociates.com 33
S. K. Ghosh Associates Inc.
ROADMAP Chapter Reorganization General Members
Connections • Column Splices • Column Bases/Anchorage Moment Frames Braced Frames
- 67 -
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) - 68 -
www.skghoshassociates.com 34
S. K. Ghosh Associates Inc.
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)
- 69 -
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 in net tension - 70 -
www.skghoshassociates.com 35
S. K. Ghosh Associates Inc.
D2.5 Column Splices Required Strength for SFRS: LRFD
System
Welds
Mr
Vr
Pr
Largest of Mr_col,
Largest of Vr_col,
Largest of
Ω0E, and
Ω0E, Mpc/H, and
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
----
- 71 -
D2.5 Column Splices Required Strength for SFRS: LRFD
System
Welds
Mr
Vr
Pr
Largest of Mr_col,
Largest of Vr_col,
Largest of
Ω0E, and
Ω0E, Mpc/H, and
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
----
- 72 -
www.skghoshassociates.com 36
S. K. Ghosh Associates Inc.
D2.5 Column Splices Required Strength for SFRS: ASD Mr System
Welds
Largest of Mr_col, Ω0E, and
Vr
Pr
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)
----
- 73 -
D2.5 Column Splices Required Strength for SFRS: ASD Mr System
Welds
Largest of Mr_col, Ω0E, and
Vr Largest of Vr_col, Ω0E, Mpc/(1.5H), and
Pr 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)
----
- 74 -
www.skghoshassociates.com 37
S. K. Ghosh Associates Inc.
D2.6 Column Bases
- 75 -
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
- 76 -
www.skghoshassociates.com 38
S. K. Ghosh Associates Inc.
D2.6 Column Bases: SFRS Axial: OCBF or SCBF - LRFD Pr_col ≥ Ω0E
T = RyFYAg or C = 1.1(1.14FcreAg)
Pr = Σ vertical components - 77 -
D2.6 Column Bases: SFRS Axial: SCBF w/ Compression Buckling - LRFD
C = 0.3[(1.14FcreAg)]
Pr_col ≥ Ω0E
T = RyFYAg
Pr = Σ vertical components - 78 -
www.skghoshassociates.com 39
S. K. Ghosh Associates Inc.
D2.6 Column Bases: SFRS LRFD Example Example member vs. connection required strength • SCBF: A500 Gr B; Fy = 46 ksi; Ry = 1.4; KL = 19 ft 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
• Ω0 = 2 for SCBF - 79 -
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
- 80 -
www.skghoshassociates.com 40
S. K. Ghosh Associates Inc.
D2.6 Column Bases: SFRS D2.6b Required Shear Strength - LRFD AISC 341-05 (8.5b) System
Lesser of 2RyFyZx/H, Ω0E, and
OMF (E1), OCBF (F1) IMF (E2.6g), SMF (E3.6g), STMF (E4.6c) SCBF (F2.6d), EBF (F3.6d), BRBF (F4.6d), SPSW (F5.6d)
AISC 341-10 Greatest of Vr_col, Ω0E, Mpc/H, and
----
----
----
ΣMpc/H
----
ΣMpc/Hc
ΣMpc/Hc = Mpc/Hc = FyZx/Hc ≤ 2RyFyZx/H Mpc/Hc ≥ Ω0E - 81 -
D2.6 Column Bases: SFRS Shear: SCBF - LRFD
C = 1.1(1.14FcreAg)
Largest of Vr_col, Ω0E Mpc/Hc
T = RyFYAg
Vr = Σ horizontal components - 82 -
www.skghoshassociates.com 41
S. K. Ghosh Associates Inc.
D2.6 Column Bases: SFRS D2.6b Required Shear Strength - ASD AISC 341-05 (8.5b) System
Lesser of (2/1.5)RyFyZx/H, Ω0E
OMF (E1), OCBF (F1) IMF (E2.6g), SMF (E3.6g), STMF (E4.6c) SCBF (F2.6d), EBF (F3.6d), BRBF (F4.6d), SPSW (F5.6d)
AISC 341-10 Greatest of Vr_col, Ω0E, Mpc/(1.5H)
----
----
----
ΣMpc/(1.5H)
----
ΣMpc/(1.5Hc)
- 83 -
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
- 84 -
www.skghoshassociates.com 42
S. K. Ghosh Associates Inc.
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 - 85 -
D2.6 Column Bases: Anchorage AISC 360 and 341
ACI 318 Appendix D
- 86 -
www.skghoshassociates.com 43
S. K. Ghosh Associates Inc.
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”.
- 87 -
AISC 341 and ACI 318 Appendix D. Design for AISC 341 Required Strengths Codes and
0.75 Strength Factor
Ductility Requirements
Standards
(0.75φNn)
Appendix D.
D.3.3.3 Exempted
D.3.3.4 Exempted
AISC 341-05 2006 IBC: ACI 318-05 2009 IBC: ACI 318-08
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
*ACI 318-11 no longer applies a 0.75 factor on shear strength - 88 -
www.skghoshassociates.com 44
S. K. Ghosh Associates Inc.
BREAK!
If you have any questions, please type them in
If you are encountering technical difficulties, please call (847) 991-2700 - 89 -
Question and Answer Session If you have any questions, please type them in
If you are encountering technical difficulties, please call (847) 991-2700
- 90 -
www.skghoshassociates.com 45
S. K. Ghosh Associates Inc.
ROADMAP Chapter Reorganization General Members Connections
Moment Frames • Prequalified Connections • Cantilever Column Systems Braced Frames
- 91 -
E. Moment-Frame Systems
- 92 -
www.skghoshassociates.com 46
S. K. Ghosh Associates Inc.
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
- 93 -
Prequalified Connections AISC 358-10
- 94 -
www.skghoshassociates.com 47
S. K. Ghosh Associates Inc.
Prequalified Connections AISC 358-10
- 95 -
Prequalified Connections AISC 358-05 Reduced Beam Section
Extended End-Plate
- 96 -
www.skghoshassociates.com 48
S. K. Ghosh Associates Inc.
Prequalified Connections AISC 358-05 with Supplement No. 1 Bolted Flange Plate
Welded Unreinforced Flange – Welded Web (WUF-W)
- 97 -
Prequalified Connections AISC 358-05 with Supplement No. 1 Kaiser Bolted Bracket ™
By Steel Cast Connections, LLC - 98 -
www.skghoshassociates.com 49
S. K. Ghosh Associates Inc.
Prequalified Connections AISC 358-10 with Supplement No. 1 Conxtech® CONXL™
By ConXtech Inc. - 99 -
E5 and E6. Cantilever Column Systems
- 100 -
www.skghoshassociates.com 50
S. K. Ghosh Associates Inc.
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 - 101 -
E5. Ordinary Cantilever Column Systems E5.2. Provides minimal inelastic drift capacity through flexural yielding of the columns • E5.4a. Axial Load Based on amplified seismic load combinations For seismic load combinations, Prc ≤ 0.15Pc
Flexural yielding of columns
- 102 -
www.skghoshassociates.com 51
S. K. Ghosh Associates Inc.
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 - 103 -
ROADMAP Chapter Reorganization General Members Connections Moment Frames
Braced Frames • Connection Deformation Compatibility • Capacity Analysis
- 104 -
www.skghoshassociates.com 52
S. K. Ghosh Associates Inc.
F. Braced-Frame and Shear-Wall Systems
- 105 -
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
- 106 -
www.skghoshassociates.com 53
S. K. Ghosh Associates Inc.
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
- 107 -
F. Deformation Compatibility Provide “simple” connection per B3.6a. of AISC 360
- 108 -
www.skghoshassociates.com 54
S. K. Ghosh Associates Inc.
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
- 109 -
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. - 110 -
www.skghoshassociates.com 55
S. K. Ghosh Associates Inc.
F2.3. SCBF Analysis Braces in Tension or Compression? • Neglect the effects of gravity loads • Consider only the first mode of deflection
- 111 -
F2.3. SCBF Expected Strength Analysis Expected strength in compression: Cexp = Min RyFyAg 1.14Fcre Fcre = Fcr with RyFy
Expected strength in tension: Texp = RyFyAg Expected Strength - 112 -
www.skghoshassociates.com 56
S. K. Ghosh Associates Inc.
F2.3. SCBF Expected Strength Analysis
Compression Tension
Elastic
Expected Strength - 113 -
F2.3. SCBF Expected Strength Analysis
Shear Elastic
Expected Strength - 114 -
www.skghoshassociates.com 57
S. K. Ghosh Associates Inc.
F2.3. SCBF Post-Buckling Analysis Post-Buckling strength in compression: Cpb = 0.3*Min RyFyAg 1.14Fcre Fcre = Fcr with RyFy
Expected strength in tension: Texp = RyFyAg Post-Buckling - 115 -
F2.3. SCBF Post-Buckling Analysis
Compression
Elastic
Post-Buckling - 116 -
www.skghoshassociates.com 58
S. K. Ghosh Associates Inc.
F2.3. SCBF Post-Buckling Analysis
Compression
Uplift
- 117 -
F2.3. SCBF Post-Buckling Analysis Unbalanced shear force
AISC 341-05 considered this force Post-Buckling - 118 -
www.skghoshassociates.com 59
S. K. Ghosh Associates Inc.
F3. Eccentrically Braced Frames
- 119 -
F3. Eccentrically Braced Frames
- 120 -
www.skghoshassociates.com 60
S. K. Ghosh Associates Inc.
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
- 121 -
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
- 122 -
www.skghoshassociates.com 61
S. K. Ghosh Associates Inc.
F3. Eccentrically Braced Frames I-Shapes: 1.25RyVn or Boxes: 1.40RyVn
Determine forces in beams, columns, braces, and connections - 123 -
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
- 124 -
www.skghoshassociates.com 62
S. K. Ghosh Associates Inc.
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
- 125 -
F3. Eccentrically Braced Frames Effective shear in links AISC 341-05
AISC 341-10
AISC 341-10
I-Shaped Links
I-Shaped Links
Box Links
Braces
1.25RyVn
1.25RyVn
1.40RyVn
Beams
1.10RyVn
0.88*(1.25RyVn) = 1.10RyVn
0.88*(1.40RyVn) = 1.23RyVn
1.10RyVn
1.25RyVn
1.40RyVn
1.10RyVn
0.88*(1.25RyVn) = 1.10RyVn
0.88*(1.40RyVn) = 1.23RyVn
Element
Columns < 3 stories Columns ≥ 3 stories
- 126 -
www.skghoshassociates.com 63
S. K. Ghosh Associates Inc.
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 - 127 -
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
- 128 -
www.skghoshassociates.com 64
S. K. Ghosh Associates Inc.
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
- 129 -
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
- 130 -
www.skghoshassociates.com 65
S. K. Ghosh Associates Inc.
Key Points Reorganized chapters for consistency with AISC 360 Increased protection of critical locations Added new systems and connections Provided consistent capacity analysis requirements
- 131 -
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:
[email protected] 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
- 132 -
www.skghoshassociates.com 66
S. K. Ghosh Associates Inc.
Resources The AISC Seismic Design Manual, 2nd, Edition www.aisc.org/Store
- 133 -
Question and Answer Session If you have any questions, please type them in
If you are encountering technical difficulties, please call (847) 991-2700
- 134 -
www.skghoshassociates.com 67
S. K. Ghosh Associates Inc.
Thank You!! For more information… www.skghoshassociates.com Chicago Main Office 334 East Colfax Street, Unit E Palatine, IL 60067 Phone: (847) 991-2700 Fax: (847) 991-2702 Email:
[email protected]
Southern California Office 43 Vantis Drive Aliso Viejo, CA 92656 Phone: (949) 215-6560 Fax: (847) 991-2702 Email:
[email protected]
- 135 -
www.skghoshassociates.com 68
