AISC 341-Significant Changes-2005 to 2010

1S. K. Ghosh Associates Inc.

www.skghoshassociates.com

- 1 -

CHANGES in AISCs 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



- 3 -

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

- 4 -

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



- 5 -


Identify target yield mechanism of the system

Flexural Yield

Tension yield and compression buckling

Shear Yield

- 6 -

Stable yield


Designate deformation-controlled elements Design for element ductility

M



- 7 -

Design remaining elements as force-controlled Design to keep members essentially elastic at

capacity of ductile elements

Resist redistributed forces


- 8 -

Accommodatedeformations


Design remaining elements as force-controlled Design for deformations caused by yielding



- 9 -

Protected Zones


Amplify forces

Demand Critical Welds

Protect critical locations

- 10 -

Key Points

Reorganized chapters for consistency with AISC 360

Increased protection of critical locations

Added new systems and connections

Provided consistent capacity analysis requirements



- 11 -

ROADMAP

Chapter Reorganization General Members Connections Moment Frames Braced Frames

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Seismic Provisions 341-05 Part I:1: Scope2: Referenced Specifications, Codes, and Standards3: General Seismic Design4: Loads, Load Combinations, Nominal Strengths5: Structural Drawings and Specifications, Shop Drawings,

and Erection Drawings6: Materials7: Connections, Joints, and Fasteners8: Members9-17: Structural Systems18: 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 RequirementsB. General Design RequirementsC. AnalysisD. General Member and Connection Design RequirementsE. Moment-Frame SystemsF. Braced-Frame and Shear-Wall SystemsG. Composite Moment-Frame SystemsH. Composite Braced-Frame and Shear-Wall SystemsI. Fabrication and ErectionJ. Quality Control and Quality AssuranceK. Prequalification and Cyclic Qualification Testing Provisions

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Chapter Reorganization

Preface to AISC 341-10



- 15 -

AISC 341-05 - Part I1. Scope2. Referenced Specifications,

Codes, and Standards

AISC 341-10A. General Requirements

B. General Design Requirements3. General Seismic Design4. Loads, Load Combinations,

Nominal Strengths

A. General RequirementsI. Fabrication and Erection

5. Structural Drawings and Specifications, Shop Drawings, and Erection Drawings

6. Materials


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AISC 341-05 - Part I7. Connections, Joints, and

Fasteners

AISC 341-10D. 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 RequirementsA3.4b. AWS D1.8




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AISC 341-05 - Part I AISC 341-10

9. Special Moment Frames10. Intermediate Moment Frames11. Ordinary Moment Frames12. Special Truss Moment

Frames

E. Moment-Frame SystemsE3. Special Moment FramesE2. Intermediate Moment FramesE1. Ordinary Moment FramesE4. Special Truss Moment

FramesE5. Ordinary Cantilever Column

SystemsE6. Special Cantilever Column

Systems


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AISC 341-05 - Part I

13. Special Concentrically Braced Frames

14. Ordinary Concentrically Braced Frames

15. Eccentrically Braced Frames16. Buckling-Restrained Braced

Frames17. Special Plate Shear Walls

AISC 341-10F. Braced-Frame and Shear-

Wall SystemsF2. Special Concentrically Braced FramesF1. Ordinary Concentrically Braced FramesF3. Eccentrically Braced FramesF4. Buckling-Restrained Braced FramesF5. Special Plate Shear Walls


10

S. K. Ghosh Associates Inc.


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AISC 341-05 - Part I18: Quality Assurance Plan

(Appendix Q)

AISC 341-10J. Quality Control and Quality Assurance

Appendix P: Connection PrequalificationAppendix S: Qualifying Cyclic Tests of Beam-to-Column and Link-to-Column ConnectionsAppendix T: Qualifying Cyclic Tests of BRBF Braces

K. Prequalification and Cyclic Qualification Testing Provisions


- 20 -

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)

11



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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 RequirementsA4.4a. AWS D1.8

I. Fabrication and Erection

Appendix R. Seismic Design Coefficients and Approximate Period Parameters

A. General RequirementsA4.4a. AWS D1.8

REMOVED


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AISC 341-05 - Part II1. Scope2. Referenced Specifications,

Codes, and Standards

AISC 341-10A. General Requirements

B. General Design Requirements3. General Seismic Design4. Loads, Load Combinations,

Nominal Strengths

D. General Member and Connection Design Requirements

5. Materials

6. Composite Members7. Composite Connections

A. General Requirements


12



- 23 -

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


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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


12. Composite Special Concentrically Braced Frames

13. Composite Ordinary Braced Frames

14. Composite Eccentrically Braced Frames

AISC 341-10


13



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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


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


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AISC 341-05 - Part II18. Structural Design Drawings

and Specifications, Shop Drawings, and Erection Drawings

AISC 341-10A. General RequirementsI. Fabrication and Erection

19. Quality Assurance Plan J. Quality Control and Quality Assurance


14



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Structural System Chapters: E - H

Consistent organization of system requirements1. Scope2. Basis of Design

Intended response/inelasticity

3. Analysis4. 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 requirements5. Member Requirements

Width-to-thickness limitations Protected Zone

6. Connections Demand Critical welds Column Splices Required Connection Strengths

7. Additional requirements

15



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ROADMAP


General Applicable Building Code Demand Critical Welds Amplified Seismic Loads

Members Connections Moment Frames Braced Frames

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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

16



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Including Supplement No. 1

Applicable Building Code

AISC 341-05


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Applicable Building Code

AISC 341-05

Including Supplements No. 1 and No. 2

17



- 33 -

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

18



- 35 -

Demand Critical Welds


- 36 -


Demand Critical Weld Requirements

SystemColumn Beam Flange

to Column Flange

Beam Web/Shear Plate to Column

FlangeBases Splices

OMF (E1.6a.) ---- ---- CJP CJPIMF (E2.6a.) All Types Groove CJP CJPSMF (E3.6a.) All Types Groove CJP CJP

STMF (E4.6a.) All Types Groove ---- ----OCCS (E5.6a.) ---- ---- ---- ----SCCS (E6.6a.) All Types Groove ---- ----

19



- 37 -


Demand Critical Weld Requirements

SystemColumn Link Flange or

Web to ColumnBuilt-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 ---- ----

- 38 -

B. General Design Requirements

B2. Load and Load Combinations

12.4.3 Seismic Load Combinations Including Overstrength FactorEm = Emh + Ev

= 0QE 0.2SDSD

20



- 39 -


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 0QE

Defines EDefines Emh

Capacity Analysis

- 40 -


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)

21



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C. Analysis

- 42 -

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

22



- 43 -

BREAK!

If you are encountering technical difficulties, please call (847) 991-2700

If you have any questions, please type them in

- 44 -

Question and Answer Session



23



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ROADMAP

Chapter Reorganization General

Members Ductility Classification Required Axial Strength of Columns

Connections Moment Frames Braced Frames

- 46 -

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

24



- 47 -


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

- 48 -

AISC 341-05: Seismically Compact

Footnotes indicated to which members and structural systems each row applies

Type of member

force

25



- 49 -

AISC 341-05: Compact

Type of member

force

AISC 360-05Compact Limits

Compact does not apply for Uniform Compression

- 50 -

D1.1b Width-to-Thickness Limitations

26



- 51 -


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)

- 52 -

D1.1b Width-to-Thickness Limitations: Table D1.1

27



- 53 -


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 --- ---

- 54 -

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)Element AISC 341-05Seismically Compact

AISC 341-10Highly 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)

28



- 55 -

D1.1b Width-to-Thickness Limitations: Highly Ductile

W18X40 = 2.11

W18X65 = 1.48

Fy = 50 ksi

Ca = Pu/(cPy) (LRFD)Ca = (cPa)/Py (ASD)

Webs of I-Shaped Beams and Columns: Highly Ductile h

d/(E

/Fy)

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) =

- 56 -

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


AISC 341-10Highly Ductile


Webs of I-Shapes**

Ca 0.1253.14(1-1.54Ca) 1.49Ca > 0.125

1.12(2.33-Ca) 1.49Rect. HSS Walls*** 0.64 0.55

Rnd. HSS Walls 0.044 0.038Stems of tees 0.30 0.30

29



- 57 -

D1.1b Width-to-Thickness Limitations: SCBF Braces

Fy = 50 ksi


Webs of I-Shaped Braces: Highly Ductile h

d/(E

/Fy)

3.14

2.50

1.49

2010: Highly Ductile


0.125 1.0

W10X17 = 1.53

W12X45 = 1.21

(b/t)(E/Fy)

=

- 58 -

Beams and columns: b/t ratio limit comparison


D1.1b Width-to-Thickness Limitations: Moderately Ductile

Table indicates factor on (E/Fy)Element AISC 360-05

CompactAISC 341-10

Moderately 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

30



- 59 -

D1.1b Width-to-Thickness Limitations: Moderately Ductile

Fy = 50 ksi


Webs of I-Shaped Beams and Columns: Moderately Ductile h

d/(E

/Fy)

3.76

2.50

1.49

2010: Moderately Ductile

2005: NonCompact for Compression

0.125 1.0

2005: Compact for Flexure

W18X40 = 2.11

W18X65 = 1.48

(b/t)(E/Fy)

=

- 60 -

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)Element AISC 360-05

CompactAISC 341-10

Moderately Ductile

Flanges of I-Shapes* 0.38 (Flexure)0.56 (Compression) 0.38

Webs of I-Shapes** 1.49 (Compression)3.76 (Flexure) 1.49Rect. HSS Walls*** 1.12 0.64

Rnd. HSS Walls 0.07 (Flexure)0.11 (Compression) 0.044

Stems of tees 0.75 0.38

31



- 61 -

D1.1b Width-to-Thickness Limitations: OCBF Braces OCBF braces: b/t ratio limit comparison:



AISC 341-10Moderately Ductile


Webs of I-Shapes*

Ca 0.1253.14(1-1.54Ca) 1.49Ca > 0.125

1.12(2.33-Ca) 1.49Rect. HSS Walls 0.64 0.64Rnd. HSS Walls 0.044 0.044Stems of tees 0.30 0.38

- 62 -

D1.1b Width-to-Thickness Limitations: OCBF Braces

Fy = 50 ksi


Webs of I-Shaped Braces: OCBF Moderately Ductile

hd/

(E/F

y)

3.14

2.50

1.49

2010: Moderately Ductile


0.125 1.0

W12X26 = 1.96

W12X35 = 1.48

(b/t)(E/Fy)

=

32



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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

- 64 -

D1.2 Stability Bracing of Beams

Maximum unbraced length of beams

*Beams in V or Inverted-V systems only

Member AISC 341-05, Lb AISC 341-10, Lb

SMF Beams (E2.4a) 0.086ry(E/Fy)Highly Ductile0.086ry(E/Fy)

IMF Beams (E3.4b)SPSW HBE (F5.4c) 0.17ry(E/Fy)

Moderately Ductile0.17ry(E/Fy)

SCBF Beams* (F2.4b)BRBF Beams* (F4.4a) [0.12+0.076(M1/M2)](E/Fy)ry

Moderately Ductile0.17ry(E/Fy)

OCBF Beams* (F1) [0.12+0.076(M1/M2)](E/Fy)ry NONE

33



- 65 -

D1.2 Stability Bracing of Beams

Beams in V- or Inverted V-Braced Frames

M1/M2

L b/[(E

/Fy)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

- 66 -

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/cPn > 0.4

ASDcPa/Pn > 0.4

Amplified Seismic Load Combinations

34



- 67 -

ROADMAP

Chapter Reorganization General Members

Connections Column Splices Column Bases/Anchorage

Moment Frames Braced Frames

- 68 -

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)

35



- 69 -

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)

- 70 -

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 Mpc = sum of nominal plastic flexural strengths H = story height Hc = clear story height 0E = 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

36



- 71 -

D2.5 Column SplicesRequired Strength for SFRS: LRFD

System WeldsMr Vr Pr

Largest of Mr_col, 0E, and

Largest of Vr_col,0E, Mpc/H, and

Largest of Pr_col, 0E, and

OMF (E1) ---- ---- ---- ----

IMF (E2.6g) No PJP Bolted: RyFyZx Mpc/H ----

SMF (E3.6g) No PJP Bolted: RyFyZx Mpc/H ----

STMF (E4.6c) No PJP Bolted: RyFyZx Mpc/H ----

- 72 -

D2.5 Column SplicesRequired Strength for SFRS: LRFD

System WeldsMr Vr Pr


Largest of Vr_col,0E, Mpc/H, and


OCBF (F1) ---- ---- ---- ----

SCBF (F2.6d) No PJP Mn/2 Mpc/Hc ----

EBF (F3.6d) No PJP Mn/2 Mpc/Hc ----

BRBF (F4.6d) No PJP Mn/2 Mpc/Hc ----

SPSW (F5.6d) No PJP Mn/2 Mpc/Hc ----

37



- 73 -

D2.5 Column SplicesRequired Strength for SFRS: ASD

System Welds

Mr Vr Pr


Largest of Vr_col,0E, Mpc/(1.5H),

and


OMF (E1) ---- ---- ---- ----

IMF (E2.6g) No PJP Bolted: RyFyZx/1.5 Mpc/(1.5H) ----

SMF (E3.6g) No PJP Bolted: RyFyZx/1.5 Mpc/(1.5H) ----

STMF (E4.6c) No PJP Bolted: RyFyZx/1.5 Mpc/(1.5H) ----

- 74 -

D2.5 Column SplicesRequired Strength for SFRS: ASD

System Welds

Mr Vr Pr


Largest of Vr_col,0E, Mpc/(1.5H),

and


OCBF (F1) ---- ---- ---- ----

SCBF (F2.6d) No PJP Mn/2 Mpc/(1.5Hc) ----

EBF (F3.6d) No PJP Mn/2 Mpc/(1.5Hc) ----

BRBF (F4.6d) No PJP Mn/2 Mpc/(1.5Hc) ----

SPSW (F5.6d) No PJP Mn/2 Mpc/(1.5Hc) ----

38



- 75 -

D2.6 Column Bases

- 76 -

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 0E combinations Required axial strength of column splices

39



- 77 -

Axial: OCBF or SCBF - LRFD


T = RyFYAg orC = 1.1(1.14FcreAg)

Pr_col 0E

Pr = vertical components

- 78 -


T = RyFYAg

Pr_col 0EC = 0.3[(1.14FcreAg)]

Axial: SCBF w/ Compression Buckling - LRFD

Pr = vertical components

40



- 79 -

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

0 = 2 for SCBF

Brace KL/r Pn RyFyAg (RyFyAg)/PnHSS8x8x5/8 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

- 80 -


D2.6b Required shear strength: Sum of horizontal components: Braces: required connection strength Columns: greater of

Shear load from 0E combinations 2RyFyZx/H (LRFD) (2/1.5)RyFyZx/H (ASD) Required shear strength of column splices

41



- 81 -


D2.6b Required Shear Strength - LRFD

System

AISC 341-05 (8.5b) AISC 341-10

Lesser of2RyFyZx/H, 0E, and

Greatest of Vr_col, 0E, Mpc/H, and

OMF (E1), OCBF (F1) ---- ----IMF (E2.6g), SMF (E3.6g),

STMF (E4.6c) ---- Mpc/H

SCBF (F2.6d), EBF (F3.6d), BRBF (F4.6d), SPSW (F5.6d) ---- Mpc/Hc

Mpc/Hc = Mpc/Hc = FyZx/Hc 2RyFyZx/HMpc/Hc 0E

- 82 -


T = RyFYAgLargest ofVr_col, 0EMpc/Hc

C = 1.1(1.14FcreAg)

Shear: SCBF - LRFD

Vr = horizontal components

42



- 83 -


D2.6b Required Shear Strength - ASD

System

AISC 341-05 (8.5b) AISC 341-10

Lesser of(2/1.5)RyFyZx/H, 0E

Greatest of Vr_col, 0E, Mpc/(1.5H)

OMF (E1), OCBF (F1) ---- ----

IMF (E2.6g), SMF (E3.6g), STMF (E4.6c) ---- Mpc/(1.5H)

SCBF (F2.6d), EBF (F3.6d), BRBF (F4.6d), SPSW (F5.6d) ---- Mpc/(1.5Hc)

- 84 -


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 0E combinations

User Note: Ignore moments for pinned bases

43



- 85 -

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)

VrMpc

Vr

- 86 -

D2.6 Column Bases: Anchorage

AISC 360 and 341

ACI 318 Appendix D

44



- 87 -

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.

- 88 -

*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 StrengthsCodes and Standards

0.75 Strength Factor (0.75Nn)

Ductility RequirementsAppendix D.

AISC 341-052006 IBC: ACI 318-052009 IBC: ACI 318-08

D.3.3.3Exempted

D.3.3.4Exempted

AISC 341-102012 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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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

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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 LoadBased on amplified seismic

load combinationsFor 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) 1.1RyFyZcol (LRFD) or (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 Emh1. Expected strength

Brace in Tension - consider expected strengthBrace in Compression - consider expected strength

2. Post-Buckling strengthBrace in Tension - consider expected strengthBrace 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


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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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Post-BucklingElastic

Compression

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Compression

Uplift

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Unbalanced shear force

AISC 341-05 considered this force

Post-Buckling

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F3. Eccentrically Braced Frames

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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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F3.3 Analysis Emh = forces in beams, columns, braces, and

connections when ALL links reach their adjusted shear strength

Adjusted shear strength I-shaped links: 1.25RyVnBox links: 1.40RyVn

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I-Shapes: 1.25RyVnor

Boxes: 1.40RyVn

Determine forces in beams, columns,

braces, and connections

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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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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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Effective shear in links

ElementAISC 341-05

I-Shaped LinksAISC 341-10

I-Shaped LinksAISC 341-10Box Links

Braces 1.25RyVn 1.25RyVn 1.40RyVn

Beams 1.10RyVn0.88*(1.25RyVn) =

1.10RyVn0.88*(1.40RyVn) =

1.23RyVnColumns < 3

stories1.10RyVn 1.25RyVn 1.40RyVn

Columns 3 stories

1.10RyVn0.88*(1.25RyVn) =

1.10RyVn0.88*(1.40RyVn) =

1.23RyVn

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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

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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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Buckling-Restrained Braced Frames F4.3. Analysis requirements added F4.6b. Connection deformation compatibility requirement added

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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

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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

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Resources

The AISC Seismic Design Manual, 2nd, Edition

www.aisc.org/Store

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Thank You!!

For more informationwww.skghoshassociates.com

Chicago Main Office334 East Colfax Street, Unit EPalatine, IL 60067Phone: (847) 991-2700Fax: (847) 991-2702Email: [email protected]

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AISC 341-Significant Changes-2005 to 2010

Documents

Transcript of AISC 341-Significant Changes-2005 to 2010