AISC Seismic Provisions

1

-CHANGES in AISC’s SEISMIC PROVISIONS:

AISC 341-05 to AISC 341-10

Formerly with

S. K. Ghosh Associates Inc.

Palatine, IL and Aliso Viejo, CA

www.skghoshassociates.com

Jason Ericksen, S.E.

FORSE Consulting, LLC

AISC Seismic Provisions

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

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

5

-Seismic Provisions Measures



Identify target yield mechanism of the system

Flexural Yield

Tension yield and

compression buckling

Shear Yield

Stable yield

Seismic Provisions Measures



Designate deformation-controlled elements

• Design for element ductility

7

-

Design remaining elements as force-controlled

• Design to keep members essentially elastic at

capacity of ductile elements

Resist

redistributed

forces

Seismic Provisions Measures

Accommodate

deformations

Seismic Provisions Measures



Design remaining elements as force-controlled

9

-Protected Zones

Seismic Provisions Measures

Amplify

forces

Demand

Critical

Welds



Protect critical locations

Key Points



Reorganized chapters for

consistency with AISC 360



Increased protection of critical

locations



Added new systems and

connections



Provided consistent capacity

11

-ROADMAP



Chapter Reorganization



General



Members



Connections



Moment Frames



Braced Frames

Reorder Rename Reformat

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)

Part II: Composite Systems

13

-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

Chapter Reorganization

15

-AISC 341-05 - Part I

1. Scope

2. Referenced Specifications, Codes, and Standards

AISC 341-10

A. General Requirements

B. General Design Requirements

3. 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

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

17

-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

AISC 341-05 - Part I

13. Special Concentrically Braced Frames

14. Ordinary Concentrically Braced Frames

15. Eccentrically Braced Frames 16. Buckling-Restrained Braced

Frames

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

19

-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)

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

21

-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

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)

23

-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

Seismic Provisions 341-05 Part II:

1: Scope

2: Referenced Specifications, Codes, and Standards 3: General Seismic Design

4: Loads, Load Combinations, Nominal Strengths 5: Materials

6: Composite Members 7: Composite Connections 8-17: Structural Systems

18:Structural Design Drawings and Specifications, Shop Drawings, and Erection Drawings

25

-AISC 341-05 - Part II

1. Scope

2. Referenced Specifications, Codes, and Standards

AISC 341-10

A. General Requirements

B. General Design Requirements

3. 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

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

27

-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

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

29

-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

ROADMAP



Chapter Reorganization



General

•

Chapters A, B, and C



Members



Connections



Moment Frames



Braced Frames

31

-A. General Requirements



A1. Scope

• “These Provisions shall apply… unless specifically

exempted by the applicable building code.”



AISC 341-05;

•

R >3, “Provisions shall apply… regardless of seismic

design category”

•

R

≤

3, “not required to satisfy these Provisions, unless

specifically required by the applicable building code.”

A.1 Scope

Applicable Building Code

Including

33

-Including Supplement No. 1

A.1 Scope

Applicable Building Code

AISC 341-05

Including

Supplements No. 1 and No. 2

A.1 Scope

Applicable Building Code



Loads and load combinations



Systems and limitations



Design requirements

35

-ASCE 7-10 Table 12.2-1

AISC 341 NOT required



A3.4b Demand Critical Welds

A. General Requirements

A3.4. Consumables for Welding

• Special CVN

requirements for

enhanced ductility

• Adjacent to locations

of high strain

System chapters AISC 358 EOR discretion

37

-A. General Requirements

A3.4b Demand Critical Welds



Demand Critical Weld Requirements

System

Column Beam Flange

to Column Flange Beam Web/Shear Plate to Column 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 ----

----A. General Requirements

A3.4b Demand Critical Welds



Demand Critical Weld Requirements

System Column Link Flange or Web to Column

Built-up Link: Web to Flange Bases 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 ----

39

-A3.4b Demand Critical Welds at

Column Base

B. General Design Requirements



B2. Loads and Load Combinations

• Where “Amplified Seismic Loads” are required for

specific members or connections

The seismic load effect including the system overstrength factor

shall be applied as prescribed by the applicable building code.

Where E_mhis defined, intended to replace E_mhin ASCE 7 Section 12.4.3.

41

-B. General Design Requirements



B2. Load and Load Combinations

12.4.3 Seismic Load Combinations

Including Overstrength Factor

E

_m

=

E

_mh

+ E

_v

=



₀

Q

_E

± 0.2S

_DS

D

B. General Design Requirements



B2. Load and Load Combinations (with Amplified

Seismic Loads)

AISC 341-10 Provisions E_mhin ASCE 7 Section 12.4.3 Requires “Amplified Seismic Load” 0QE Defines E Defines Emh Capacity Analysis

43

-B. General Design Requirements

AISC 341-05:

• Defines E

(neglects

vertical effect)

•

E

= E

m

= E

mh

+ 0

AISC 341-10:

• Defines E

_mh

• E

_m

= E

_mh

+ E

_v

= E

_mh

+

0.2S

DS

D



B2. Load and Load Combinations (with Amplified

Seismic Loads)

45

-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

BREAK!

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

If you have any questions,

please type them in

47

-Question

 

and

 

Answer

 

Session

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

If you have any questions,

please type them in

ROADMAP



History and Ductility



Chapter Reorganization



General



Members

•

D1. General Member Requirements



Connections



Moment Frames



Braced Frames

Courtesy of S. Mahin U.C. Berkeley, 2004

49

-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

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

51

-AISC 341-05: Seismically Compact

Footnotes indicated to which members and structural systems each row applies Type of member force

AISC 341-05: Compact

Type of member force AISC 360-05 Compact Limits

53

-D1.1b Width-to-Thickness Limitations

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)



Type of member force (flexure, uniform compression)



Member type (beam, column, brace)

55

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

Table D1.1

Type of member

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

57

-

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/F_y)

Element AISC 341-05 Seismically Compact AISC 341-10 Highly Ductile Flanges of I-Shapes* 0.30 0.30 Web of I-Shapes** Ca≤ 0.125 3.14(1-1.54C_a) Ca≤ 0.125 2.45(1-0.93C_a) Ca> 0.125 1.12(2.33-C_a) ≥ 1.49 Ca> 0.125 0.77(2.93-C_a) ≥ 1.49 SMF

Flanges of Boxed I-Shaped and Built-Up Box Columns

NA 0.60 0.30√(E/Fy)

D1.1b Width-to-Thickness Limitations:

Highly Ductile

W18X40 = 2.11 W18X65 = 1.48 Fy= 50 ksi

Webs of I-Shaped Beams and Columns: Highly Ductile

hd / √ (E/F y ) 3.14 2.5 2.45 2.16 1.49 2010: Highly Ductile 2005: Seismically Compact

2005: Seismically Compact for Flexure of SMF Beams

(b/t) √(E/Fy)

59

-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)

Element AISC 341-05 Seismically Compact AISC 341-10 Highly Ductile Flanges of I-Shapes* 0.30 0.30 Webs of I-Shapes** C_a≤ 0.125 3.14(1-1.54Ca) _1.49 Ca> 0.125 1.12(2.33-C_a) ≥ 1.49 Rect. HSS Walls*** 0.64 0.55 Rnd. HSS Walls 0.044 0.038 Stems of tees 0.30 0.30

D1.1b Width-to-Thickness Limitations:

SCBF Braces

Fy= 50 ksi

Webs of I-Shaped Braces: Highly Ductile

hd / √ (E/F y ) 3.14 2.50 1.49 2010: Highly Ductile 2005: Seismically Compact W10X17 = 1.53 W12X45 = 1.21 (b/t) √(E/Fy) =

61

-

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/F_y)

Element AISC 360-05

“Compact”

AISC 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≤ 0.125 3.76(1-2.75C_a) Ca> 0.125 1.12(2.33-C_a) ≥ 1.49 IMF

Flanges of Boxed I-Shaped and Built-Up Box Columns

NA 0.55

D1.1b Width-to-Thickness Limitations:

Moderately Ductile

Fy= 50 ksi

Webs of I-Shaped Beams and Columns: Moderately Ductile

hd / √ (E/F y ) 3.76 2.50 1.49 2010: Moderately Ductile

2005: NonCompact for Compression 2005: Compact for Flexure

W18X40 = 2.11 W18X65 = 1.48 (b/t) √(E/Fy) =

63

-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

“Compact”

AISC 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) 1.49 Rect. HSS Walls*** 1.12 0.64 Rnd. HSS Walls 0.07 (Flexure) 0.11 (Compression) 0.044 Stems of tees 0.75 0.38

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

Table indicates factor on √(E/F_y)

Element AISC 341-05 Seismically Compact AISC 341-10 Moderately Ductile Flanges of I-Shapes* 0.30 0.38 Webs of I-Shapes* Ca≤ 0.125 3.14(1-1.54C_a) 1.49 Ca> 0.125 1.12(2.33-C_a) ≥1.49 Rect. HSS Walls 0.64 0.64 Rnd. HSS Walls 0.044 0.044 Stems of tees 0.30 0.38

65

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

OCBF Braces

F_y= 50 ksi Ca= Pu/(cPy) (LRFD) C_a= (cPa)/Py (ASD)

Webs of I-Shaped Braces: OCBF – Moderately Ductile

hd / √ (E/F y ) 3.14 2.50 1.49 2010: Moderately Ductile 2005: Seismically Compact 0.125 1.0 W12X26 = 1.96 W12X35 = 1.48 (b/t) √(E/Fy) =

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

67

-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

D1.2 Stability Bracing of Beams



Beams in V- or Inverted V-Braced Frames

Lb

/[(E/F

y

)ry

]

AISC 341-05 (Appendix 1 of AISC 360-05) L_b= [0.12+0.076(M₁/M₂)](E/F_y)r_y

AISC 341-10: Moderately Ductile Lb= 0.17(E/Fy)ry 0.196 0.120 0.044 -1.0 0 1.0 0

69

-D1.4 Columns



All SFRS columns

now are required to use amplified

seismic load combinations to determine P

_r

in the

absence of moments

AISC 341-05

LRFD

P

_u

/



_c

P

_n

> 0.4

ASD



_c

P

_a

/P

_n

> 0.4

Amplified Seismic Load

Combinations

ROADMAP



History and Ductility



Chapter Reorganization



General



Members



Connections

•

D2. General Connection

Requirements



Moment Frames

71

-D2.1 Connections

AISC 341-05: Connections

7.1 Scope

The design of connections for a member that is part of

the SLRS shall be configured such that a ductile limit

state in either the connection or the member controls

the design.

The requirement was removed because it was deemed

too onerous because the required strengths are capacity

controlled.

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)

73

-D2.5. Column Splices: SFRS



D2.5b. Required Strength: largest of

• Required strength of the column (M

_{r_col}

, V

_{r_col}

, P

_{r_col}

)

• Effect of amplified seismic loads

(M

r_Em

, V

r_Em

, P

r_Em

)

• Structural system requirements

• Special requirements for columns in net tension

determined using load combinations including

overstrength

D2.5. Column Splices: SFRS



D2.5c. Required Shear Strength: greater of

• Required strength from D2.5.b

• M

_pc

/H (LRFD)

or

M

_pc

/(1.5H) (ASD)

Where;

M

_pc

= Lesser

nominal plastic flexural strength

H = story height

75

-SFRS Column Splices:

Table Definitions

M

_{r_col}

, V

_{r_col}

, P

_{r_col}

= required strengths of the column

M

_{r_Em}

, V

_{r_Em}

, P

_{r_Em}

= required strengths of the column from of

seismic load combinations including overstrength

M

_r

, V

_r

, P

_r

= required strengths of the splice

M

_n

=

lesser

nominal flexural strength (includes effects of

unbraced length)

M

_pc

=

lesser

nominal plastic flexural strength



M

_pc

= sum of nominal plastic flexural strengths

H = story height (top of beam flange to top of beam flange)

H

_c

= clear story height (top of beam flange to bottom of beam

flange)

D2.5 Column Splices

Required Strength for SFRS: LRFD

System Welds Mr 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 ΣMpc/H ----SMF(E3.6g) No PJP Bolted: R_yF_yZ_x ΣM_pc/H ----STMF (E4.6c) No PJP Bolted: R_yF_yZ_x ΣM_pc/H

77

-D2.5 Column Splices

Required Strength for SFRS: LRFD

System Welds Mr Vr Pr Largest of Mr_col, 0E, and Largest of Vr_col, 0E,Mpc/H, and Largest of P_{r_col,} 0E, and OCBF(F1) ---- ---- ---- ----SCBF(F2.6d) No PJP Mn/2 ΣMpc/Hc ----EBF(F3.6d) No PJP M_n/2 ΣM_pc/H_c ----BRBF(F4.6d) No PJP Mn/2 ΣMpc/Hc ----SPSW(F5.6d) No PJP Mn/2 ΣMpc/Hc

----D2.5 Column Splices

Required Strength for SFRS: ASD

System Welds Mr Vr Pr Largest of Mr_col, 0E, and Largest of Vr_col, 0E,Mpc/(1.5H), and Largest of P_{r_col,} 0E, and OMF (E1) ---- ---- ----

----IMF(E2.6g) No PJP Bolted: RyFyZx/1.5 ΣMpc/(1.5H) ----SMF(E3.6g) No PJP Bolted: R_yF_yZ_x/1.5 ΣM_pc/(1.5H) ----STMF (E4.6c) No PJP Bolted: RyFyZx/1.5 ΣMpc/(1.5H)

79

-D2.5 Column Splices

Required Strength for SFRS: ASD

System Welds Mr Vr Pr Largest of Mr_col, 0E, and Largest of Vr_col, 0E,Mpc/(1.5H), and Largest of P_{r_col,} 0E, and OCBF(F1) ---- ---- ---- ----SCBF(F2.6d) No PJP M_n/2 ΣM_pc/(1.5H_c) ----EBF(F3.6d) No PJP Mn/2 ΣMpc/(1.5Hc) ----BRBF(F4.6d) No PJP Mn/2 ΣMpc/(1.5Hc) ----SPSW(F5.6d) No PJP M_n/2 ΣM_pc/(1.5H_c)

----D2.6 Column Bases



Like column splices,

column bases are

also considered

critical locations and

have similarly

increased

requirements.

81

-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

Axial: SCBF - LRFD

D2.6 Column Bases: SFRS

Required Axial Strength

P

_{r_col}

≥



₀

E

P

_r

=

Σ

vertical

T =

R

y

F

y

A

g

or

C =

1.1*Min R

y

F

y

A

g

1.14F

_cre

A

_g Fcre= Fcrwith RyFy

L ≤ distance from brace end to brace end

83

-D2.6 Column Bases: SFRS

Required Axial Strength

T =

R

_y

F

_y

A

_g

P

r_col

≥



₀

E

Axial: SCBF w/ Compression Buckling - LRFD

P

r

=

Σ

vertical

components

C =

0.3*Min R

y

F

y

A

g

1.14F

_cre

A

_g Compression force from SCBF analysis requirements, Section F2.3

D2.6 Column Bases: SFRS

Required Axial Strength - LRFD



Example member vs. connection required strength

•

SCBF

: A500 Gr B; F

y

= 46 ksi; R

y

= 1.4; KL = 19 ft

•



= 2 for SCBF

Brace KL/r _cP_n R_yF_yA_g (R_yF_yA_g)/_cP_n 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

85

-D2.6 Column Bases: SFRS

Required Shear Strength



D2.6b Required shear strength: Sum of horizontal

components:

• Braces: required connection strength

• Columns: greater of

Shear load from ₀E combinations

2R_yF_yZ_x/H (LRFD) (2/1.5)R_yF_yZ_x/H (ASD) Required shear strength of column splices

D2.6 Column Bases: SFRS

Required Shear Strength

Column Component - LRFD System AISC 341-05 (8.5b) AISC 341-10 Lesser of 2RyFyZx/H and0E Largest of V_{r_col},₀E, M_pc/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

87

-D2.6 Column Bases: SFRS

Required Shear Strength

T = R

y

F

y

A

g

Largest

of

V

_{r_col}

,



₀

E

M

_pc

/H

_c

Shear: SCBF - LRFD

V

_r

=

Σ

horizontal

components

C =

1.1*Min R

y

F

y

A

g

1.14F

_cre

A

_g Required connection strength in compression, Section F2.6c(1)

D2.6 Column Bases: SFRS

Required Shear Strength

Column Component - ASD

System AISC 341-05 (8.5b) AISC 341-10 Lesser of (2/1.5)R_yF_yZ_x/H, ₀E Largest of Vr_col,0E, 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),

89

-D2.6 Column Bases: SFRS

Required Flexural Strength



D2.6c Required Flexural Strength: Sum of flexural

components:

• Braces: required connection strength

Based on critical buckling axis

Rotation capacity may be provided in place of flexural strength

• Columns: lesser of

1.1R_yF_yZ (LRFD) or (1.1/1.5) R_yF_yZ (ASD)

Moment from ₀E combinations

• User Note: Ignore moments for pinned bases

D2.6 Column Bases:

Columns Not Part of SFRS



D2.6b Required Shear Strength: Non-SFRS

Columns:

• Required shear strength of column splices



M

_pc

/H (LRFD)

or

M

_pc

/(1.5H) (ASD)

V

_r

M

_pc

91

-D2.6 Column Bases: Anchorage

AISC 360 and 341

ACI 318 Appendix D

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”.

93

-*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 (0.75N_n) Ductility Requirements Appendix D. AISC 341-05 2006 IBC: ACI 318-05 2009 IBC: ACI 318-08 D.3.3.3 Exempted D.3.3.4 Exempted 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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95

-Question

 

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Answer

 

Session

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ROADMAP



History and Ductility



Chapter Reorganization



General



Members



Connections



Moment Frames

•

Chapter E

•

AISC 358-10

97

-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

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

99

-Prequalified Connections

AISC 358-10

Prequalified Connections

AISC 358-10

101

-Extended End-Plate

Prequalified Connections

AISC 358-05

Reduced Beam Section

Welded

Unreinforced

Flange – Welded

Web (WUF-W)

Prequalified Connections

AISC 358-05 with Supplement No. 1

103

-Prequalified Connections

AISC 358-05 with Supplement No. 1

Kaiser Bolted Bracket ™

By Steel Cast Connections, LLC

Conxtech® CONXL™

Prequalified Connections

105

-E5 and E6. Cantilever Column Systems

E5 and E6. 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

107

-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, P

_rc

≤

0.15P

_c

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, P

_rc

≤

0.15P

_c

• E6.4b. Unbraced length: Moderately Ductile

• E6.5a. b/t limitations: Highly Ductile

109

-ROADMAP



History and Ductility



Chapter Reorganization



General



Members



Connections



Moment Frames



Braced Frames

F1 and F2: Concentrically

Braced-Frame 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

111

-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 M

_r

; lesser of:



1.1R

_y

M

_{p_bm}

(LRFD)

or

(1.1/1.5)R

_y

M

_{p_bm}

(ASD)





1.1R

_y

F

_y

Z

_col

(LRFD)

or



(1.1/1.5)R

_y

F

_y

Z

_col

(ASD)



Welds are Demand Critical

F. Deformation Compatibility

113

-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

F2.3. SCBF Analysis



Two analyses to determine

E

_mh

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

115

-F2.3. SCBF Analysis



Braces in

Tension

or

Compression

?

• Neglect the effects of gravity

loads

• Consider only the first mode of

deflection

Expected strength in

compression:

C

_exp

= Min R

y

F

y

A

g

1.14F

_cre

A

_g

Expected strength

in tension:

T

_exp

= R

_y

F

_y

A

_g Fcre= Fcrwith RyFy

L ≤ distance from brace end to brace end

117

-Expected Strength

Elastic

Compression

Tension

F2.3. SCBF Expected Strength Analysis

F2.3. SCBF Expected Strength Analysis

119

-Post-Buckling

Post-Buckling strength in

compression:

C

pb

= 0.3*Min R

_1.14F

y

F

y

A

g cre

A

g

Expected strength

in tension:

T

_exp

= R

_y

F

_y

A

_g Fcre= Fcrwith RyFy

L ≤ distance from brace end to brace end

F2.3. SCBF Post-Buckling Analysis

F2.3. SCBF Post-Buckling Analysis

121

-F2.3. SCBF Post-Buckling Analysis

Compression

Uplift

F2.3. SCBF Post-Buckling Analysis

Unbalanced

shear force

AISC 341-05

123

-F3. Eccentrically Braced Frames

125

-F. Braced-Frame and Shear-Wall

Systems



Summary of Changes

• F3.3. Analysis requirements revised

• F3.5b(1). Built-up box sections allowed (no HSS)

• F3.6b. New connection deformation compatibility

F3. Eccentrically Braced Frames



F3.3 Analysis

• E

mh

= forces in beams, columns, braces, and

connections when ALL links reach their adjusted

shear strength

• Adjusted shear strength



I-shaped links: 1.25R

_y

V

_n 

Box links: 1.40R

_y

V

_n

127

-F3. Eccentrically Braced Frames

I-Shapes: 1.25R

_y

V

_n

or

Boxes: 1.40R

y

V

n

Determine forces in

beams, columns,

braces, and

connections

F3. Eccentrically Braced Frames



F3.3 Analysis

• Permitted to take E

mh

= 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

129

-F3. Eccentrically Braced Frames



Required Strength in AISC 341-05

• 15.6a. Diagonal Brace

E = forces in brace when shear in link reaches 1.25R_yV_n

• 15.6b. Beam Outside Link

E = forces in brace when shear in link reaches 1.1R_yV_n

• 15.8. Columns

E = forces in brace when shear in link reaches 1.1R_yV_nin ALL

levels above the column

F3. Eccentrically Braced Frames



Effective shear in links

Element AISC 341-05 I-Shaped Links AISC 341-10 I-Shaped Links AISC 341-10 Box Links Braces 1.25R_yV_n 1.25R_yV_n 1.40R_yV_n Beams 1.10RyVn 0.88*(1.25R_1.10R yVn) = yVn 0.88*(1.40RyVn) = 1.23RyVn Columns < 3 stories 1.10RyVn 1.25RyVn 1.40RyVn Columns ≥ 3 1.10RV 0.88*(1.25RyVn) = 0.88*(1.40RyVn) =

131

-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

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

133

-F4. Buckling-Restrained Braced

Frames



Summary of Changes

• Buckling-Restrained Braced Frames

F4.3. Analysis requirements added

F4.6b. Connection deformation compatibility requirement added

F4. Buckling-Restrained Braced

Frames



F4.6b. Beam-to-Column Connections

• Brace connection to Beam and Column (2 options)

Provide “simple” connection

135

-F5. Special Plate Shear Walls



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

137

-Key Points



Reorganized chapters for

consistency with AISC 360



Increased protection of critical

locations



Added new systems and

connections



Provided consistent capacity

analysis requirements

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

139

-Resources

The AISC

Seismic Design

Manual

, 2

nd

_{, Edition}

www.aisc.org/Store

141

-SKGA Wind Simple Computer Program



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

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

Applies the effective area reduction factor for C&C

pressures.



Provides the design wind pressures for each applicable

zone of the building in clear and concise tables.



Documents the calculations in clear and attractive reports.



And more…..

http://skghoshassociates.com/wind-simple

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-Jason Ericksen, S.E.

[email protected]

www.FORSEconsulting.com

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