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COMPARISON OF ANSI/AISC 360-10 TO ANSI/AISC 360-05 (prepared by Eric Bolin and Tom Dehlin)

This document summarizes the revisions contained in the 2010 AISC Specification for Structural Steel Buildings (ANSI/AISC 360-10) compared to the 2005 AISC Specification for Structural Steel Buildings (ANSI/AISC 360-05).

CHAPTER A GENERAL PROVISIONS

The major changes to this chapter include:

• The reorganization of seismic application sections. • The removal of the seismic response modification factor, R. • The addition of several new standards, codes and specifications.

A1. SCOPE

The scope of the 2010 Specification has been expanded by including systems with structural steel acting compositely with reinforced concrete. Added to this section is a reference to ASCE/SEI 7 for loads, load combinations, system limitations and general design requirements in the event there is no applicable building code. A1.1. Seismic Applications (was Sections A1.1 and A1.2)

There are no longer categories classified as “low” or “high” seismic. The Specification now refers to the Seismic Provisions for Structural Steel Buildings (ANSI/AISC 341) for the design of seismic force resisting systems and the discussion of the seismic response modification factor, R, has been moved into a new user note.

A1.2. Nuclear Applications (was Section A1.3) The reference to the Load and Resistance Factor Design Specification for Steel Safety-Related Structures for Nuclear Facilities (ANSI/AISC N690L) has been removed from this section.

A2. REFERENCED SPECIFICATIONS, CODES AND STANDARDS

Several additions and updates have been made to the specifications, codes and standards listed in this section.

A3. MATERIAL A3.1. Structural Steel Materials

The following statement has been removed from this section, “If requested, the fabricator shall provide an affidavit stating that the structural steel furnished meets the requirements of the grade specified.”

A3.1a. ASTM Designations

Several ASTM Specifications have been added as approved for use with the 2010 Specification. For hot-rolled shapes, ASTM A1043/A1043M has been added, for structural tubing, ASTM A618M and A847M has been added, for plates, ASTM A1043/A1043M has been added and for sheets ASTM A606M has been added.

A3.1b. Unidentified Steel

This section is expanded to include a statement that the use of unidentified steel shall be subject to the approval of the engineer of record. Also added is a

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statement that unidentified steel be allowed if its failure does not reduce the strength of the structure.

A3.1c. Rolled Heavy Shapes

A rolled heavy shape welded connection subject to tension that requires a Charpy V-notch impact test result in the contract documents has been changed as follows:

• “Spliced” has been changed to “spliced or connected” using complete-joint-penetration groove welds.

• Complete-joint-penetration groove welds that “fuse through the thickness of the member” has been changed to “fuse through the thickness of the flange or the flange and web”.

The exception to the above requirement has been changed as follows:

• 2005 Specification: Charpy V-notch results are not required when a non-heavy shape is welded to the face of a rolled heavy shape with complete joint penetration groove welds.

• 2010 Specification: When a rolled heavy shape is welded to the surface of another shape using groove welds the Charpy V-notch requirement only applies to the shape with the weld metal fused through the cross section.

A3.1d. Built-Up Heavy Shapes No changes have been made to this section. A3.2. Steel Castings and Forgings No changes have been made to this section. A3.3. Bolts, Washers and Nuts

The following ASTM Specifications have been added for bolts: ASTM A354 and ASTM F2280. For washers ASTM F844 has been added.

A3.4. Anchor Rods and Threaded Rods No changes have been made to this section. A3.5. Consumables for Welding

The title of this section has been changed from Filler Metal Flux for Welding. The following metric American Welding Society specifications have been added to this section: AWS A5.1M, AWS A5.5M, AWS A5.18M, AWS A5.20M, AWS A5.28M and AWS A5.29M.

A3.6. Headed Stud Anchors

The title of this section has been changed from Stud Shear Connectors. The welding code, AWSD1.1M, was added to this section. The user note referencing ASTM A29/A29M-04 for studs made from cold drawn bar has been removed.

A4. STRUCTURAL DESIGN DRAWINGS AND SPECIFICATIONS

The provision for deviations which don’t meet the Code of Standard Practice for Steel Buildings and Bridges be specifically identified in design drawings and/or specifications has been removed. A user note is added to this section stating the information that is to be shown on the design drawings.

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CHAPTER B DESIGN REQUIREMENTS

The major changes to this chapter include:

• The incorporation of structural integrity requirements for connections in the limit state section. • Bearing bolts are permitted in short slotted holes parallel to the direction of tension loading. • The moment redistribution section has been moved to this chapter from Appendix 1. • The addition of a section for the design of diaphragms and collectors. • Reorganization of the tables for limiting width-to-thickness ratios for flexure and compression

elements. • Compression elements are now classified as either slender or nonslender. • A new section has been added for quality control and quality assurance provisions.

B1. GENERAL PROVISIONS No changes have been made to this section. B2. LOADS AND LOAD COMBINATIONS

The user note in this section has been reworded for clarity. B3. DESIGN BASIS

Several new sections have been added. Section B3.12, Design Wall Thickness for HSS, has been moved to Section B4.2. Section B3.13, Gross and Net Area Determination, has been moved to Section B4.3.

B3.1. Required Strength

The reference to the provisions in Appendix 1 for moment redistribution in continuous beams has been removed because this topic has been moved into this chapter.

B3.2. Limit States

Several additions have been made to this section for completeness of structural integrity requirements for connections. The limit states based on limiting deformations or yielding do not need to be considered for structural integrity requirements. Also, bolt bearing with short-slotted holes parallel to the direction of tension are to be assumed at the end of the slot.

B3.3. Design for Strength Using Load and Resistance Factor Design (LRFD) No changes have been made to this section. B3.4. Design for Strength Using Allowable Strength Design (ASD) No changes have been made to this section. B3.5. Design for Stability No changes have been made to this section. B3.6. Design of Connections Added to this section is the statement that self-limiting inelastic deformations

are permitted. For beams, girders and trusses the supports shall be restrained against rotation unless analysis shows that restraint is not required.

B3.6a. Simple Connections The provisions for permitting inelastic rotation of a connection have been

removed from this section.

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B3.6b. Moment Connections No changes have been made to this section. B3.7. Moment Redistribution in Beams (was Appendix 1, Section 1.3) A provision has been added that does not permit the reduction for moment

redistribution for members with Fy exceeding 65 ksi or for design using partially restrained moment connections.

B3.8. Diaphragms and Collectors (new section) References to applicable sections for designing diaphragm and collector

elements have been added in this new section. B3.9. Design for Serviceability (was Section B3.7) The word “performance” has been removed from the requirements for

serviceability design. The word “connectors” has also been removed from this section.

B3.10. Design for Ponding (was Section B3.8) No changes have been made to this section. B3.11. Design for Fatigue (was Section B3.9) No changes have been made to this section. B3.12. Design for Fire Conditions (was Section B3.10) Portions of this section have been reworded to improve clarity. B3.13. Design for Corrosion Effects (was Section B3.11) No changes have been made to this section. B3.14. Anchorage to Concrete (new section) This section includes references to Chapter I for design of steel and concrete

acting compositely and Chapter J for design of column bases and anchor rods. B4. MEMBER PROPERTIES

The title of this section has been changed from Classification of Sections for Local Buckling. Several sub-sections have been moved here including, B4.2, Design Wall Thickness for HSS and B4.3, Gross and Net Area Determination. The topics of quality control and quality assurance are now included in a new section.

B4.1. Classification of Sections for Local Buckling (was section B4)

The local buckling classifications for members have been separated for flexure and compression. The classification for flexure remains the same while compression members are now classified as either slender or nonslender. The reference to Table B4.1 now reflects the new Tables B4.1a for members subject to axial compression and B4.1b for members subject to flexure.

TABLE B4.1a Width-to-Thickness Ratios: Compression Elements Members Subject to Axial Compression

This table contains the cases from Table B4.1 in the 2005 Specification that apply to compression. New figures are included in the Examples column, which now include a larger number of applicable sections. Since compression elements in members subject to axial compression are now defined as either slender or nonslender, only the limiting width to thickness ratio, λr, is provided in this table. The following table shows the changes that have been made to the element descriptions and the case numbering in this table.

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Case (2010) Case (2005) Change in Description 1 3 Flanges of tees have been added to this case 2 4 * 3 5 * 4 8 * 5 10 Flanges of channels have been added to this

case 6 12 The term “flanges” has been changed to

“walls” and bending has been removed from description

7 12 Bending has been removed from description 8 14 * 9 15 “Circular hollow sections” has been changed

to “Round HSS” and bending is removed from the description

* No changes have been made. B4.1a. Unstiffened Elements (was Section B4.1) No changes have been made to this section. B4.1b. Stiffened Elements (was Section B4.2)

In this section the term “centroid” has been changed to “center of gravity”. Section (e) has been added defining, b, the width of perforated cover plates. TABLE B4.1b Width-to-Thickness Ratios: Compression Elements Members Subject to Flexure

This table contains the cases from Table B4.1 in the 2005 Specification that apply to flexure. New figures are included in the Examples column, which now include a larger number of applicable sections. The following table shows the changes that have been made to the element descriptions and case numbering in this table.

Case (2010) Case (2005) Change in Description

10 1 Flanges of tees added to this case 11 2 * 12 6 * 13 New Weak axis flexure of flanges of rolled I-

shaped sections, channels and tees 14 New New section and limits for the stems of tees

in flexure 15 9 * 16 11 * 17 12 Compression removed from description 18 12 Compression removed from description 19 13 Webs of boxes added 20 15 “Circular hollow sections” has been changed

to “Round HSS” and compression is removed from the description

* No changes have been made. B4.2. Design Wall Thickness for HSS (was Section B3.12) No changes have been made to this section.

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B4.3. Gross and Net Area Determination (was Section B3.13) B4.3a. Gross Area (was Section B3.13a) No changes have been made to this section. B4.3b. Net Area (was Section B3.13b) A reference to Section J3.2 for determining slot dimensions has been removed.

The following statement has been added: “For members without holes, the net area, An, is equal to the gross area, Ag.”

B5. FABRICATION AND ERECTION

Quality control has been removed from this section since the referenced chapter, Chapter M, no longer contains the topic of quality control.

B6. QUALITY CONTROL AND QUALITY ASSURANCE (new section)

This new section references the new Chapter N, Quality Control and Quality Assurance. B7. EVALUATION OF EXISTING STRUCTURES (was Section B6) This section has been reworded for clarity.

CHAPTER C DESIGN FOR STABILITY

The major changes to this chapter include:

• The title of this chapter has been changed from Stability Analysis and Design. • This chapter now contains the direct analysis method, which has been moved from Appendix.7 • The approximate second-order analysis (B1-B2 method) has been moved to Appendix 8. • A new section, C3, titled Calculation of Available Strengths has been added to this section.

C1. GENERAL STABILITY REQUIREMENTS (was Section C1.1)

The content of this section has been reorganized to improve clarity. A numbered list is now provided for effects that should be considered when analyzing the stability of a structure. Added to this list includes stiffness reduction due to inelasticity and uncertainty in stiffness and strength. Removed from this list is member stiffness reduction due to residual stresses. The list has been changed so component and connection deformations are now categorized under all other deformations that contribute to the displacement of the structure. The LRFD and ASD load levels used for analysis are included in this section. Added to this section is the statement that any rational method that considers the effects listed in this section is permitted. A user note is included in this section defining the term design, which is the combination of analysis to determine required strength and proportioning components to have adequate available strength.

C1.1. Direct Analysis Method of Design (new section)

This section refers to sections C2 and C3 for the calculation of required and available strengths, respectfully, for this method of analysis.

C1.2. Alternative Methods of Design (new section)

This section refers to Appendix 7 for the effective length and first-order analysis methods if justified by the provisions.

C2. CALCULATION OF REQUIRED STRENGTHS

This section now contains the required strength calculations using the direct analysis method. Several new sections have been added based on the requirements of this method. The content of this section have been moved from Appendix 7 in the 2005 Specification.

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C2.1. General Analysis Requirements (new section)

The following conditions have been added to allow for the P-δ effects to be neglected: the ratio of maximum second-order drift to maximum first-order drift is equal or less than 1.7 and no more than one third of the gravity load can be supported by the moment resisting frame in the direction of translation considered. P-δ effects must always be considered in the evaluation of individual members subject to flexure and compression. Also added is a statement that the approximate method of second-order analysis is permitted as an alternative to rigorous second-order analysis. Analysis will cover all gravity loads and applied loads that may influence the stability of the structure. Two user notes have been added, one states the P-δ effects evaluated for individual members can be satisfied by applying the B1 multiplier, the other states that it is important to include all gravity loads in the analysis.

C2.2. Consideration of Initial Imperfections (new section)

The effects of initial imperfections can be accounted for using either direct modeling or the use of notional loads (covered previously in Appendix 7, Section 7.2). A user note has been added stating that the imperfections considered are the locations of points of intersection of members caused by the out-of-plumbness of columns. Initial out-of-straightness of members is addressed in Chapter E for compression members and is not considered explicitly in analysis.

C2.2a. Direct Modeling of Imperfections (new Section)

The provisions in this section allow for the effects of initial imperfections to be accounted for directly by analysis. The pattern of initial displacement of points of intersection from their nominal locations shall be the maximum amount considered which causes the greatest destabilizing effect. A user note has been added stating the initial displacements should be similar in configuration to displacements caused by loading and buckling with magnitudes based on permissible construction tolerances given in the AISC Code of Standard Practice. If gravity loads are supported primarily by vertical members and the ratio of maximum second-order drift to maximum first-order drift is less than or equal to 1.7, effects of initial imperfections can be included in the analysis of gravity only load combinations only.

C2.2b. Use of Notional Loads to Represent Imperfections

The content of this section has been moved from Appendix 7, Sections 7.2 and 7.3 in the 2005 Specification. Added is a statement that notional loads are permissible for structures that support gravity loads primarily through nominally vertical members. A user note has been added stating that using notional loads can create additional fictitious base shears and overturning moments. The correct horizontal reaction at the base is found using a force equal to but opposite in direction to the notional loads applied at the base.

C2.3. Adjustments to Stiffness (new section)

This section has been moved from Appendix 7, Section 7.3(3). The equations for the reduced flexural stiffness (Eq. A-7-2) and reduced axial stiffness (Eq. A-7-3), have been reformatted into a text description and moved into Section C2.3(1). A paragraph has been added for the stability analysis of a structure using materials other than structural steel.

C3. CALCULATION OF AVAILABLE STRENGTHS (new section)

This section refers to Chapters D, E, F, G, H, I, J and K for the determination of available strengths of members when using the direct analysis method. The effective length factor, K, will

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be taken as unity unless a smaller value can be justified by analysis. The bracing which defines the unbraced length will have stiffness sufficient to control member movement at braced points, which is covered in Appendix 6.

CHAPTER D DESIGN OF MEMBERS FOR TENSION

The major changes to this chapter include:

• The gross and net area sections have been moved to Chapter B. • A new minimum shear lag factor is given for open cross-section shapes. • Modifications have been made to the description of elements in Table D3.1.

D1. SLENDERNESS LIMITATIONS No changes have been made to this section. D2. TENSILE STRENGTH No changes have been made to this section. D3. EFFECTIVE NET AREA

The title of this section has been changed from Area Determination. Sections D3.1, Gross Area, and D3.2, Net Area have been moved to Sections B4.3a and B4.3b, respectively. For open cross sections the minimum shear lag factor, U, has been changed from equal to or greater than 0.60 to the ratio of the gross area of the connected elements to the member gross area. The alternate lesser value of U, based on the effect of eccentricity, has been removed.

Table D3.1 Shear Lag Factors for Connections to Tension Members This table remains the same with the following exceptions: Case 2 has been expanded to include tension members that transmit tensile load with longitudinal welds in combination with transverse welds. Two new figures have been added for Case 2 examples, one is a single angle the other is a tee shape. Case 8 is expanded to include double angles. In the 2005 Specification the single angle condition with 2 or 3 fasteners per line in the direction of loading, with U = 0.60, has been changed to only 3 fasteners and directs the user to Case 2 for less fasteners.

D4. BUILT-UP MEMBERS No changes have been made to this section. D5. PIN-CONNECTED MEMBERS D5.1. Tensile Strength

In Equation D5-1 the variable for effective edge distance, beff, has been changed to be.

D5.2. Dimensional Requirements No changes have been made to this section. D6. EYEBARS D6.1. Tensile Strength No changes have been made to this section. D6.2. Dimensional Requirements No changes have been made to this section.

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CHAPTER E

DESIGN OF MEMBERS FOR COMPRESSION The major changes to this chapter include:

• A new chapter selection table has been added for various compression member cross sections. • Changes have been made to the provisions for single angle compression members. • A new modified slenderness ratio is given for built up members. • The term “critical” has been removed from the definition of the elastic buckling stress, Fe.

E1. GENERAL PROVISIONS

Sections E1(a) and E1(b) have been removed from this section and placed in the new Table User Note E1.1.

TABLE USER NOTE E1.1 Selection Table for the Application of Chapter E Sections This new selection table shows the applicable limit states with chapter section references for doubly symmetric, singularly symmetric and unsymmetrical cross-section shapes with and without slender elements. This table is similar to the flexural member selection table, Table User Note F1.1, found at the beginning of Chapter F in the 2005 Specification .

E2. EFFECTIVE LENGTH

The title of this section has been changed from Slenderness Limitations and Effective Length. This section now references Appendix 7 in addition to Chapter C, for the determination of the effective length factor, K. The term “column” has been replaced with “member” in this section.

E3. FLEXURAL BUCKLING OF MEMBERS WITHOUT SLENDER ELEMENTS

The title of this section has been changed from Compressive Strength for Flexural Buckling of Members without Slender Elements. The application of this section has changed from members with compact and noncompact sections to nonslender elements. The “flexural buckling stress”, Fcr, is now referred to as the “critical stress”. In Section E3(a) the alternate slenderness check, Fe ≥ 0.44Fy, is now shown as Fy/Fe ≤ 2.25 and in Section E3(b), Fe < 0.44Fy, is now shown as Fy/Fe > 2.25. The elastic buckling stress, Fe, now references Appendix 7 instead of Section C2.

E4. TORSIONAL AND FLEXURAL-TORSIONAL BUCKLING OF MEMBERS WITHOUT

SLENDER ELEMENTS The title of this section has been changed from Compressive Strength for Torsional and Flexural-

Torsional Buckling of Members without Slender Elements. This section now applies to all doubly symmetric members without slender elements when the torsional unbraced length exceeds the lateral unbraced length and for single angles with b/t > 20. In Section E4(a), the member slenderness for double angle compression members is:

m

KL KLr r

⎛ ⎞= ⎜ ⎟⎝ ⎠

With the exception of their ordering, the equations in this section remain unchanged. E5. SINGLE ANGLE COMPRESSION MEMBERS This section now stipulates that the provisions in Section E4 apply to single angles with b/t > 20.

The material in Section E5(c) has been moved to Section E5 with the exception of the specific examples of different end conditions, requiring the use of Chapter H provisions, which has been removed.

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E6. BUILT-UP MEMBERS E6.1. Compressive Strength

This section is reorganized to improved clarity. The provision for end connection of built-up members shall be welded or by means of pretensioned bolts with Class A or B faying surfaces has been moved from Section E6.2. The user note from section E6.2, which states it is acceptable to design the bolted end connections for full compressive load with bolts in bearing and bolt design based on the shear strength, but the bolts must be pretensioned, has been moved into this section. This user note also states that the end connection should be designed to resist slip. Section E6.1(i) has been changed to E6.1(a) and Section E6.1(ii) has been changed to E6.1(b). In Section E6.1(b), the modified column slenderness equation for built up shapes with intermediate connectors that are welded or connected with pretensioned bolts has been replaced with two new equations as follows:

(i) When 40i

ar

≤

m o

KL KLr r

⎛ ⎞ ⎛ ⎞=⎜ ⎟ ⎜ ⎟⎝ ⎠ ⎝ ⎠

(E6-2a)

(ii) When 40i

ar

>

22i

im o o

KL KL K ar r r

⎛ ⎞⎛ ⎞ ⎛ ⎞= +⎜ ⎟ ⎜ ⎟ ⎜ ⎟⎝ ⎠ ⎝ ⎠ ⎝ ⎠ (E6-2b)

The variable Ki is defined as 0.50 for angles back-to-back, 0.75 for channels back-to-back, and 0.86 for all other cases.

E6.2. Dimensional Requirements

Parts of this section have been reworded to improve clarity. E7. MEMBERS WITH SLENDER ELEMENTS The statement that it is conservative to use the smaller Qs for cross sections composed of multiple

unstiffened slender elements has been added to the user note. E7.1. Slender Unstiffened Elements, Qs

In Section E7.1(b) the column which the element is projecting from has been changed from built-up to built-up I-shaped.

E7.2. Slender Stiffened Elements, Qa

The variable for summation of effective areas, Aeff, has been changed to Ae.

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CHAPTER F DESIGN OF MEMBERS FOR FLEXURE

The major changes to this chapter include:

• The equation for the lateral-torsional buckling modification factor, Cb, has been modified • The additions of a new Rpc equation. • Changes to the equations for flange local buckling of tees. • The addition of a new section for local buckling of tee stems. • New proportioning limits are now given for I-shaped members. • This chapter now contains the unbraced length moment redistribution section, moved from

Appendix 1. TABLE USER NOTE F1.1 Selection Table for the Application of Chapter F Sections

The portion of this table referring to Section F12 for unsymmetrical shapes now excludes single angles.

F1. GENERAL PROVISIONS The content of this section has been reorganized into two new subsections. The use of the lateral-

torsional buckling modification factor, Cb, in now limited to singly symmetric members in single curvature and all doubly symmetric members. In Equation F1-1 the cross-section monosymmetry parameter, Rm, has been removed along with the upper limit as follows,

2005 Specification:

12.5 3.02.5 3 4 3

maxb m

max A B c

MC RM M M M

= ≤+ + +

2010 Specification:

12.52.5 3 4 3

maxb

max A B c

MCM M M M

=+ + +

The statement that Cb is permitted to be conservatively taken as 1.0 has been removed. The user note has been expanded to include the value of Cb for equal end moments of the same sign and also refers to the commentary for detailed analysis for singly symmetric members.

F2. DOUBLY SYMMETRIC COMPACT I-SHAPED MEMBERS AND CHANNELS BENT

ABOUT THEIR MAJOR AXIS F2.1. Yielding No changes have been made to this section. F2.2. Lateral-Torsional Buckling

A user note has been added stating that Equations F2-3 and F2-4 in the 2010 Specification produce identical solutions as the equations used in past editions of the LRFD Specification but are similar in appearance to the equations used for singularly symmetric sections. Equation F2-6 has been changed as follows: 2005 Specification:

20.7

1.95 1 1 6.760.7

y x or ts

y x o

FE Jc S hL rF S h E Jc

⎛ ⎞= + + ⎜ ⎟

⎝ ⎠ (F2-6)

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2010 Specification:

22 0.7

1.95 6.760.7

yr ts

y x o x o

FE Jc JcL rF S h S h E

⎛ ⎞⎛ ⎞= + + ⎜ ⎟⎜ ⎟⎝ ⎠ ⎝ ⎠

(F2-6)

F3. DOUBLY SYMMETRIC I-SHAPED MEMBERS WITH COMPACT WEBS AND

NONCOMPACT OR SLENDER FLANGES BENT ABOUT THEIR MAJOR AXIS F3.1. Lateral-Torsional Buckling No changes have been made in this section. F3.2. Compression Flange Local Buckling A definition of h has been added to this section. F4. OTHER I-SHAPED MEMBERS WITH COMPACT OR NONCOMPACT WEBS BENT

ABOUT THEIR MAJOR AXIS F4.1. Compression Flange Yielding The definition of Myc has been added to this section. F4.2. Lateral-Torsional Buckling

The web plastification factor, Rpc, is now based on the ratio of Iyc/Iy in Section F4.2c. A definition for variables, Iyc and hc, have been added to this section.

F4.3. Compression Flange Local Buckling No changes have been made to this section. F4.4. Tension Flange Yielding No changes have been made to this section. F5. DOUBLY SYMMETRIC AND SINGLY SYMMETRIC I-SHAPED MEMBERS WITH

SLENDER WEBS BENT ABOUT THEIR MAJOR AXIS F5.1. Compression Flange Yielding No changes have been made to this section. F5.2. Lateral-Torsional Buckling No changes have been made to this section. F5.3. Compression Flange Local Buckling No changes have been made to this section. F5.4. Tension Flange Yielding No changes have been made to this section. F6. I-SHAPED MEMBERS AND CHANNELS BENT ABOUT THEIR MINOR AXIS F6.1. Yielding No changes have been made to this section. F6.2. Flange Local Buckling

In Section F6.2(a), the text has been changed from “The limit state of yielding shall apply” to “Flange local buckling does not apply”. In Equation F6-4 the variable, bf, has been changed to b. The definition of b has been added, which is equal to bf for the flanges of I-shaped members.

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F7. SQUARE AND RECTANGULAR HSS AND BOX-SHAPED MEMBERS A user note has been added to this section stating that a lateral-torsional buckling equation is not

provided in this section since the limit state of beam deflection will control for reasonable cases. F7.1. Yielding No changes have been made to this section. F7.2. Flange Local Buckling

In Equation F7-3 the variable for the effective section modulus, Seff, has been changed to Se. In Equation F7-4 the variable for flange thickness, t, has been changed to tf.

F7.3. Web Local Buckling No changes have been made to this section. F8. ROUND HSS F8.1. Yielding No changes have been made to this section. F8.2. Local Buckling No changes have been made to this section. F9. TEES AND DOUBLE ANGLES LOADED IN THE PLANE OF SYMMETRY A new section, F9.4, has been added for checking the limit state of local buckling for tee stems in

flexural compression. F9.1. Yielding

New sub-sections have been added to improve the organization of this section. F9.2. Lateral-Torsional Buckling No changes have been made to this section.

F9.3. Flange Local Buckling of Tees In this section the equations for critical buckling stress have been changed to nominal moment strength equations for sections with noncompact and slender flanges as follows, 2005 Specification (b) For noncompact sections

1.19 0.502

f ycr y

f

b FF F

t E⎛ ⎞⎛ ⎞

= −⎜ ⎟⎜ ⎟⎜ ⎟⎝ ⎠⎝ ⎠ (F9-7)

(c) For slender sections

20.69

2

crf

f

EFbt

=⎛ ⎞⎜ ⎟⎝ ⎠

(F9-8)

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2010 Specification (b) For sections with a noncompact flange in flexural compression

( )0.7 1.6pfn p p y xc y

rf pfM M M F S M

⎛ ⎞λ − λ= − − ≤⎜ ⎟

λ − λ⎝ ⎠ (F9-6)

(c) For sections with a slender flange in flexural compression

20.7

2

xcn

f

f

ESMbt

=⎛ ⎞⎜ ⎟⎝ ⎠

(F9-7)

A new user note has been added to this section stating that for double angles with flange legs in compression the limit state of local buckling is checked using Section F10.3 with b/t of the flange legs as an upper limit.

F9.4. Local Buckling of Tee Stems in Flexural Compression (new section)

In this new section the nominal moment strength of tee stems in flexural compression is calculated using the elastic section modulus, Sx and the critical stress, Fcr. The critical stress equations are calculated based on the ratio of d/tw

using the following limits: 0.84 and 1.03y y

E EF F

. A user note has been added

to this section stating that for double angles with web legs in compression the limit state of local buckling is checked using Section F10.3 with b/t of the web legs as an upper limit.

F10. SINGLE ANGLES There has been a statement added to this section stating if there is a moment about both principle

axes with or without axial load, or of there is a moment along one principle axis with axial load the combined stress ratio shall be determined using Section H2. A user note has been added stating if bending is about the minor axis, only the limit states of yielding and leg local buckling apply.

F10.1. Yielding No changes have been made in this section. F10.2. Lateral-Torsional Buckling

Several parts within this section have been relocated to improve organization. In Section F10.2(b)(iii), no axial compression has been added to the requirement for the use of Equations F10-6a and F10-6b. The variable for the laterally unbraced length of member, L, has been changed to Lb.

F10.3. Leg Local Buckling No changes have been made to this section. F11. RECTANGULAR BARS AND ROUNDS F11.1. Yielding No changes have been made to this section. F11.2. Lateral-Torsional Buckling No changes have been made to this section. F12. UNSYMMETRICAL SHAPES The variable for lowest elastic section modulus relative to the axis of bending, S, has been changed

to Smin.

15

F12.1. Yielding No changes have been made to this section. F12.2. Lateral-Torsional Buckling No changes have been made to this section. F12.3. Local Buckling No changes have been made to this section. F13. PROPORTIONS OF BEAMS AND GIRDERS F13.1. Strength Reductions for Members With Holes in the Tension Flange

This section has been renamed from Hole Reductions. The references to Sections D3.1 and D3.2 for the calculation of the gross and net area of the tension flange have been changed to Section B4.3a and B4.3b, respectfully.

F13.2. Proportioning Limits for I-Shaped Members

The proportion limits of I-shaped members with slender webs have been changed as follow:

For, 2005 Specification 2010 Specification

1.5ah

≤ 11.7w ymax

h Et F

⎛ ⎞ =⎜ ⎟⎝ ⎠

12.0w ymax

h Et F

⎛ ⎞ =⎜ ⎟⎝ ⎠

1.5ah

> 0.42w ymax

h Et F

⎛ ⎞ =⎜ ⎟⎝ ⎠

0.40w ymax

h Et F

⎛ ⎞ =⎜ ⎟⎝ ⎠

F13.3. Cover Plates

No changes have been made to this section. F13.4. Built-Up Beams No changes have been made to this section. F13.5. Unbraced Length for Moment Redistribution (new section)

The contents of this section have been moved from Appendix 1, Section 1.7 in the 2005 Specification. Equation A-1-7 and A-1-8 in the 2005 Specification have been changed to Equations F13-8 and F13-9, respectfully. The variable for the limiting laterally unbraced length for plastic analysis, Lpd, has been changed to the limiting laterally unbraced length for eligibility for moment redistribution in beams, Lm.

CHAPTER G DESIGN OF MEMBERS FOR SHEAR

The major changes to this chapter include:

• A limiting condition for the use of tension field action has been modified. G1. GENERAL PROVISIONS No changes have been made to this section. G2. MEMBERS WITH UNSTIFFENED OR STIFFENED WEBS

16

G2.1. Shear Strength The title of this section has been changed from Nominal Shear Strength. When determining the equation for the web plate shear buckling coefficient, the term unstiffened web has been changed to web without transverse stiffeners. The web plate shear buckling coefficient equation for webs with transverse stiffeners has been given the equation number G2-6.

G2.2. Transverse Stiffeners

A new variable, Ist, has been assigned to the moment of inertia of transverse stiffeners. The minimum of this moment of inertia has been moved from the text to Equation G2-7. In Equation G2-8, the variable, a, has been changed to b. The provision for when lateral bracing is attached to a stiffener has been removed.

G3. TENSION FIELD ACTION G3.1. Limits on the Use of Tension Field Action No changes have been made to this section. G3.2. Shear Strength with Tension Field Action

The title of this section has been changed from Nominal Shear Strength with Tension Field Action.

G3.3. Transverse Stiffeners

The first limiting condition in Section G3.3(1), for tension field action with transverse stiffeners, has been given equation number G3-3. The equation for the second limiting condition has been changed as follows: 2005 Specification

20.15 (1 ) 18 0y rst s w v w

yst c

F VA D ht C tF V

⎡ ⎤> − − ≥⎢ ⎥⎣ ⎦ (G3-3)

2010 Specification

( ) 11 2 1

2 1

r cst st st st

c c

V VI I I IV V

−⎡ ⎤≥ + − ⎢ ⎥−⎣ ⎦ (G3-4)

Several new variables are defined in this section including Ist, Ist1, Ist2, Vc1, Vc2 and ρst. The following equation has been added to this section:

1.54 1.3

2 40ywst

stFhIE

ρ ⎛ ⎞= ⎜ ⎟⎝ ⎠

(G3-5)

G4. SINGLE ANGLES This section has been reorganized to improve clarity. The given, Cv = 1.0, for determining the

shear strength of a single angle has been removed from this section. The following relationship has been added: h/tw = b/t.

G5. RECTANGULAR HSS AND BOX-SHAPED MEMBERS This section has been reorganized for clarity. The definition of the design wall thickness, t, has

been added to this section. G6. ROUND HSS The definition of, Ag, has been changed from the gross area based on design wall thickness to the

gross cross-sectional area of the member.

17

G7. WEAK AXIS SHEAR IN DOUBLY SYMMETRIC AND SINGLY SYMMETRIC SHAPES The following relationship has been added: h/tw = b/tf. A definition of, b, has been added to this

section. G8. BEAMS AND GIRDERS WITH WEB OPENINGS No changes have been made to this section.

CHAPTER H DESIGN OF MEMBERS FOR COMBINED FORCES AND TORSION

The major changes to this chapter include:

• The addition of a new section for the rupture of flanges with holes subject to tension. • In the Cb scale factor equation, α has been changed from 1.5 to 1.6 for ASD. • A modification has been made to the interaction equation in Section H1.3.

H1. DOUBLY AND SINGLY SYMMETRIC MEMBERS SUBJECT TO FLEXURE AND

AXIAL FORCE

H1.1. Doubly and Singly Symmetric Members Subject to Flexure and Compression

No changes have been made to this section. H1.2. Doubly and Singly Symmetric Members Subject to Flexure and Tension

The term tensile strength has been changed to axial strength in the variable definitions. The scale factor for Cb with doubly symmetric members using LRFD and ASD has been combined into the following equation:

1 r

ey

PPα

+

The α in this equation for ASD has been changed from 1.5 to 1.6.

H1.3. Doubly Symmetric Rolled Compact Members Subject to Single Axis Flexure and Compression The title of this section has been changed from Doubly Symmetric Members in Single Axis Flexure and Compression. The following condition has been added to this section for compact members: (KL)z ≤ (KL)y. This limit state of “flexural-torsional buckling” has been changed to “lateral-torsional buckling.” The provision that Section H1.1 be used if Mr/Mc ≥ 0.05 in both directions (biaxial moment), has been changed to Mry/Mcy ≥ 0.05 (single axis moment). The equation for out of plane buckling has been changed as follows:

2005 Specification 2

1.0r r

co cx

P MP M

⎛ ⎞+ ≤⎜ ⎟⎝ ⎠

(H1-2)

2010 Specification

2

1.5 0.5 1.0r r rx

cy cy b cx

P P MP P C M

⎛ ⎞ ⎛ ⎞− + ≤⎜ ⎟ ⎜ ⎟⎝ ⎠⎝ ⎠

(H1-2)

The statement that the moment ratio in Equation H1-2 shall be neglected if bending is only about the weak axis has been removed.

18

H2. UNSYNNETRIC AND OTHER MEMBERS SUBJECT TO FLEXURE AND AXIAL FORCE

The subscript r has been added to all the required stress variables and c to all the available stress variables in Equation H2-1.

H3. MEMBERS SUBJECT TO TORSION AND COMBINED TORSION, FLEXURE, SHEAR

AND/OR AXIAL FORCE The title of this section has been changes from Members Under Torsion and Combined Torsion,

Flexure, Shear and/or Axial Force. H3.1. Round and Rectangular HSS Subject to Torsion

The title of this section has been changed from Torsional Strength of Round and Rectangular HSS. This section has been reorganized to improve clarity. The definitions of h and t have been added to this section.

H3.2. HSS Subject to Combined Torsion, Shear, Flexure and Axial Force No changes have been made to this section. H3.3. Non-HSS Members Subject to Torsion and Combined Stress

The title of this section has been changed from Strength of Non-HSS Members Under Torsion and Combined Stress. The design and allowable torsional strength has been changed to available torsional strength.

H4. RUPTURE OF FLANGES WITH HOLES SUBJECT TO TENSION (new section) This new section covers the check required for bolt holes in flanges subject to tension under

combined axial force and major axis flexure.

CHAPTER I DESIGN OF COMPOSITE MEMBERS

The major changes to this chapter include:

• The term “shear connector” has been changed to “steel headed stud anchor”. • The provisions of ACI 318 now apply in addition to an applicable building code. • New limiting width-to-thickness ratios for filled composite members subject to compression and

flexure. • Modification to nominal axial and flexural strength equations for filled composite members based

on the limiting width-to-thickness ratios. • The maximum allowed b/t ratios for rectangular and round HSS have been increased. • A single set of resistance and safety factors are now given for encased and filled composite

members subject to flexure. • New methods are allowed for calculating the available shear strength of filled and encased

composite members. • The interaction equations of Section H1.1 now apply to encased and filled composite members

subject to combined flexure and axial force. • Force allocation provisions now apply to both filled and encased composite members. • Provisions have been added for an external force applied concurrently to steel and concrete. • New equations along with a set of resistance and safety factors are now given for direct bond

interaction. • Modifications have been made to the steel anchor detailing requirements for filled and encased

members. • A new section has been added for composite diaphragms and collector beams. • The maximum position effect factor, Rp, has been changed to 0.75.

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The following table includes the organizational changes made to the sections of Chapter I in the 2010 Specification,

2010 Specification 2005 Specification Section Title Section

I1.1 Concrete and Steel Reinforcement ** I1.2 Nominal Strength of Composite Sections I1.1 I1.2a Plastic Stress Distribution Method I1.1a I1.2b Strain Compatibility Method I1.1b I1.3 Material Limitations I1.2 I1.4 Classification of Filled Composite Sections for Local

Buckling **

I2.1d Load Transfer I2.1e I2.1e Detailing Requirements I2.1f I2.2d Load Transfer I2.2e I3.1b Strength During Construction I3.1c I3.4 Filled Composite Member I3.3 I4 Shear ** I4.1 Filled and Encased Composite Members I2.1d and I2.2d I4.2 Composite Beams With Formed Steel Deck I3.1b I5 Combined Flexure and Axial Force I4 I6 Load Transfer ** I6.1 General Requirements ** I6.2 Force Allocation ** I6.2a External Force Applied to Steel Section I2.1e I6.2b External Force Applied to Concrete I2.1e I6.2c External Force Applied Concurrently to Steel and

Concrete **

I6.3 Force Transfer Mechanisms ** I6.3a Direct Bearing I2.1e I6.3b Shear Connection ** I6.3c Direct Bond Interaction ** I6.4a Encased Composite Members I2.1f I6.4b Filled Composite Members I2.2f I7 Composite Diaphragms and Collector Beams ** I8.1 General I3.2d(6) I8.2 Steel Anchors in Composite Beams I1.3 I8.2a Strength of Steel Headed Stud Anchors I3.2d(3) I8.2b Strength of Steel Channel Anchors I3.2d(4) I8.2c Required Number of Steel Anchors I3.2d(5) and

I3.2d(6) I8.2d Detailing Requirements I3.2d(6) I8.3 Steel Anchors in Composite Components ** I8.3a Shear Strength of Steel Headed Stud Anchors in

Composite Components **

I8.3b Tensile Strength of Steel Headed Stud Anchors in Composite Components

**

I8.3c Strength of Steel Headed Stud Anchors for Interaction of Shear and Tension in Composite Components

**

I8.3d Shear Strength of Steel Channel Anchors in Composite Components

**

I8.3e Detailing Requirements in Composite Components ** I9 Special Cases I5

** Indicates that this is a new section

20

I1. GENERAL PROVISIONS The reference to the applicable building code and ACI 318 for the design, details and material

properties of concrete and reinforcement has been moved to Section I1.1. I1.1. Concrete and Steel Reinforcement

In the 2005 Specification the provisions of the ACI 318 are applied in the absence of an applicable building code. The 2010 Specification stipulates that the ACI 318 applies in addition to an applicable building code. Several new exceptions and limitations are given for the use of ACI 318. A user note is included in this section that states it is the intent of the Specification for the reinforced concrete portion of a composite section to be detailed using the noncomposite provisions of ACI 318.

I1.2. Nominal Strength of Composite Sections

Added to this section is the statement that local buckling effects do not need to be considered for encased composite members.

I1.2a. Plastic Stress Distribution Method

Compression in the concrete section is now defined as compression due to axial force and/or flexure.

I1.2b. Strain Compatibility Method No changes have been made to this section. I1.3. Material Limitations

Structural steel has been included in the list for material limitations of this section. The provision that higher strength materials are permitted when justified by testing or analysis has been removed.

I1.4. Classification of Filled Composite Sections for Local Buckling

This section covers the new limiting width-to-thickness ratios for filled composite sections. These sections qualify as compact, noncompact or slender for both compression and flexure. The ratios and limits for filled composite members are located in Tables I1.1a and I1.1b.

TABLE I1.1A Limiting Width-to-Thickness Ratios for Compression Steel Elements in Composite Members Subject to Axial Compression for Use with Section I2.2 (new table)

This new table includes the width-to-thickness ratios, compact/noncompact limits, noncompact/slender limits and maximum permitted width-to-thickness ratio for the walls of rectangular HSS, boxes and round HSS subject to compression.

TABLE I1.1B Limiting Width-to-Thickness Ratios for Compression Steel Elements in Composite Members Subject to Flexure for Use with Section I3.4 (new table)

This new table includes the width-to-thickness ratios, compact/noncompact limits, noncompact/slender limits and maximum permitted width-to-thickness ratio for the flanges of rectangular HSS and boxes, webs of rectangular HSS and boxes and round HSS subject to flexure.

I2. AXIAL FORCE

The title of this section has been changed from Axial Members.

21

I2.1. Encased Composite Members I2.1a. Limitations

Several new requirements have been added to Section I2.1a for lateral ties. A minimum size of reinforcement is given along with the maximum spacing of ties based on reinforcement size and least column dimension. A user note is included referring to ACI 318 for additional tie and spiral reinforcement requirements.

I2.1b. Compressive Strength

The provisions of this section now specifically apply to axially loaded doubly symmetric encased composite members. The variable for nominal axial compressive strength without length effects, Po, has been changed to Pno. The variable for the minimum yield stress of the reinforcing bars, Fyr, has been changed to Fysr. Added is a statement that the available compressive strength need not be less than that of the bare steel member.

I2.1c. Tensile Strength No changes have been made to this section. I2.1d. Load Transfer

This section now refers to Section I6 for load transfer requirements for encased composite members.

I2.1e. Detailing Requirements

Several detailing requirements have been removed from this section including the total number of longitudinal reinforcing bars and the transverse reinforcement spacing. The provision for clear cover to reinforcing steel has been changed from a minimum 1.5 in. to a minimum of 1.5 times the reinforcing bar diameter, but not less than 1.5 in. Shear connector detailing requirements have been moved to Section I6.4a.

I2.2 Filled Composite Members

The title of this section has been changed from Filled Composite Columns. Noncompact and slender members are now allowed by the provisions without justification by testing or analysis.

I2.2a. Limitations

The term “HSS” has been removed from the provisions of this section. The width-to-thickness ratios for local buckling are now contained in Table I1.1. The maximum permitted b/t ratio for rectangular HSS has been changed from 2.26 / yE F to 5.00 / yE F . The maximum permitted b/t ratio for round HSS has been changed from 0.15E/Fy to 0.31E/Fy.

I2.2b. Compressive Strength

The term “column” has been changed to “member” in this section. The equation for the available compressive strength of a compact member has been changed as follows:

2005 Specification 2010 Specification '

2o s y sr yr c cP A F A F C A f= + + '2

sno y s c c sr

c

EP F A C f A AE

⎛ ⎞= + +⎜ ⎟⎝ ⎠

New available compressive strength equations are given for noncompact and slender sections. New critical stress equations are given for rectangular and

22

round filled sections. A statement that the available compressive strength need not be less than that of the bare steel member has been added.

I2.2c. Tensile Strength The term “column” has been changed to “member” in this section. I2.2d. Load Transfer

This section now refers to Section I6 for load transfer requirements for filled composite members.

I3. FLEXURE

The title of this section has been changed from Flexural Members. I3.1. General I3.1a. Effective Width No changes have been made to this section. I3.1b. Strength During Construction No changes have been made to this section. I3.2. Composite Beams With Steel Headed Stud or Steel Channel Anchors

The title of this section has been changed from Strength of Composite Beams with Shear Connectors.

I3.2a. Positive Flexural Strength No changes have been made to this section. I3.2b. Negative Flexural Strength No changes have been made to this section. I3.2c. Composite Beams with Formed Steel Deck

The title of this section has been changed from Strength of Composite Beams with Formed Steel Deck. “Specified by the designer” has been changed to “specified by the contract documents” for use of other types of steel deck anchorage devices.

I3.2d. Load Transfer Between Steel Beam and Concrete Slab

The title of this section has been changed from Shear Connectors. The variable for the area of adequately developed longitudinal reinforcing steel within the effective width of the concrete, Ar, has been changed to Asr. The subsections covering the strength, number and placement and spacing or steel headed stud anchors have been moved to Section I8.

I3.3. Encased Composite Members

In the 2005 Specification this section contained provisions for both encased and filled members. In the 2010 Specification the provisions for filled members have been moved to Section I3.4. The LRFD resistance factor and ASD safety factor if steel anchors are provided using the plastic stress distribution on the composite section or strain compatibility methods have been changed as follows:

23

2005 Specification φb = 0.85 (LRFD) Ωb = 1.76 (ASD)

2010 Specification

φb = 0.90 (LRFD) Ωb = 1.67 (ASD)

This change gives equivalent resistance and safety factors for all conditions of encased composite members subject to flexure.

I3.4. Filled Composite Members

This topic has been moved from Section I3.3 in the 2005 Specification. I3.4a. Limitations

Filled composite sections are now classified for local buckling using the limiting width-to-thickness ratios in Table I1.1.

I3.4b. Flexural Strength

New equations have been provided for the calculation of the nominal flexural strength for compact, noncompact and slender filled composite members. The LRFD resistance factor and ASD safety factor are given as follows:

φb = 0.90 (LRFD) Ωb = 1.67 (ASD) I4. SHEAR I4.1. Filled and Encased Composite Members

The available shear strength of an encased composite member is now allowed to be calculated using the nominal shear strength of the steel section alone. The available shear strength for filled composite members is now allowed to be calculated based on the nominal shear strength of the steel section plus the nominal shear strength of the reinforcing steel. The resistance factor for LRFD and safety factor for ASD are given for calculating the nominal shear strength of the reinforced concrete portion alone or the reinforced concrete with the steel section, they are as follows:

φv = 0.75 (LRFD) Ωv = 2.00 (ASD) I4.2. Composite Beams With Formed Steel Deck

Composite beams with steel channel anchors have been added to this section. I5. COMBINED FLEXURE AND AXIAL FORCE

Checks of encased and filled composite members with compact sections are now allowed to use the interaction equations of Section H1.1, for combined flexure and axial force. Additionally, the interaction equations of Section H1.1 are now allowed for filled composite members with noncompact and slender sections.

I6. LOAD TRANSFER

I6.1. General Requirements This section combines the axial load transfer for both the encased and filled axially loaded composite members.

I6.2. Force Allocation

The provisions in 2005 Specification Section I2.1e for load transfer in an encased member have been moved into this section. These provisions now apply to filled members.

24

I6.2a. External Force Applied to Steel Section

The statement: “shear connectors shall be provided to transfer the required shear force” has been changed to “the force required to be transferred to the concrete”. The variable for the force required to be transferred to the concrete, Vr, has been changed to Vr′.

I6.2b. External Force Applied to Concrete

The statement: “shear connectors shall be provided to transfer the required shear force” has been changed to “the force required to be transferred to the steel”. The equation for the force required to be transferred to the steel has been changed as follows, 2005 Specification ( )' /s y oV V A F P= (I2-10) 2010 Specification ( )' /r r y s noV P F A P= (I6-2) where,

Pr = required external force applied to the composite member

I6.2c. External Force Applied Concurrently to Steel and Concrete This new section gives the provision for an encased or filled composite member with force applied concurrently to the concrete and steel sections.

I6.3. Force Transfer Mechanisms

The provisions in 2005 Specification Section I2.2e for load transfer in a filled member have been moved into this section.

I6.3a. Direct Bearing This force transfer section is now defined as “direct bearing from internal bearing mechanisms”. The limit state for the bearing strength is now defined as “concrete crushing.” The term “load is applied” has been changed to “force is transferred”. In the bearing strength equation the variable for nominal bearing strength of concrete, Pp, has been changed to nominal strength of force transfer mechanism, Rn and the variable for loaded area, AB, has been changed to loaded area of concrete, A1.

I6.3b. Shear Connection This new section gives the provisions for force transfer by shear connection in filled and encased composite members.

I6.3c. Direct Bond Interaction

This new section gives equations for force transfer in filled rectangular and round steel sections by direct bond interaction. The LRFD resistance factor and ASD safety factor are given as follows:

φb = 0.45 (LRFD) Ωb = 3.33 (ASD)

I6.4. Detailing Requirements I6.4a. Encased Composite Members

The provisions for steel anchor detailing for encased composite members have been moved from Section I2.1f. The distribution of the shear connectors has changed from “along the length of the member” to “within the load introduction

25

length”. The distribution has changed from at least 2.5 times the depth to at most 2 times the minimum transverse dimension of the member above and below the load transfer region. The provision for the maximum connector spacing of 16 in. has been removed.

I6.4b. Filled Composite Members

The provisions for steel anchor detailing for filled composite members have been moved from Section I2.2f. The distribution of the shear connectors has changed from “along the length of the member” to “within the load introduction length”. The distribution of at least 2.5 times the width if rectangular HSS and 2.5 times the diameter of round HSS has been changed to at most 2 times the minimum transverse dimension of the member above and below the load transfer region. The provision for the maximum connector spacing of 16 in. has been removed.

I7. COMPOSITE DIAPHRAGMS AND COLLECTOR BEAMS This section gives the provisions for composite slab diaphragms and collector beams. I8. STEEL ANCHORS I8.1. General

The diameter of a steel headed stud anchor has been changed from “not greater than 2.5 times the thickness of the flange” to “not greater than 2.5 times the thickness of the base metal”

I8.2. Steel Anchors in Composite Beams

The title of this section has been changed from Shear Connectors. No additional changes have been made to this section.

I8.2a. Strength of Steel Headed Stud Anchors

The title of this section has been changed form Strength of Stud Shear Connectors. The cross-sectional area of stud shear connector, Asc, has been changed to the cross-sectional area of steel headed stud anchor, Asa. For steel headed stud anchors welded directly to the steel shape the position effect factor, Rp, has been changed from 1.0 to 0.75. The footnote in the user note which gives the qualifications for a no decking condition has been removed.

I8.2b. Strength of Steel Channel Anchors

The title of this section has been changed form Strength of Channel Shear Connectors. The channel shear connecter is now defined as a hot-rolled channel anchor. The length of channel shear connector, Lc, has been changed to the length of channel anchor, la.

I8.2c. Required Number of Steel Anchors

No changes have been made in this section. I8.2d. Detailing Requirements

Added to this section is a provision for the minimum distance from the center of an anchor to a free edge in the direction of the shear force, which is 8 in. for normal weight concrete and 10 in. for light weight concrete.

I8.3. Steel Anchors in Composite Components

This new section covers the provisions for other types of composite components not covered in other sections of this chapter. Included in this section is the height to diameter ratio of normal and light weight concrete for various loading

26

conditions along with the head diameter to shank diameter ratio for steel headed stud anchors subjected to tension or interaction of shear and tension.

I8.3a. Shear Strength of Steel Headed Stud Anchors in Composite Components

This section covers the shear strength of a steel headed stud anchor when concrete breakout is not an applicable limit state.

I8.3b. Tensile Strength of Steel Headed Stud Anchors in Composite Components

This section covers the tensile strength of a steel headed stud anchor based on the distance from the anchor to a free edge and the center-to-center anchor spacing.

I8.3c. Strength of Steel Headed Stud Anchors for Interaction of Shear and

Tension in Composite Components This section covers the nominal strength for interaction between shear and

tension for a steel headed stud anchor. I8.3d. Shear Strength of Steel Channel Anchors in Composite Components

This section refers to Section I8.2b and gives the resistance factor (LRFD) and safety factor (ASD) for the shear strength of steel channel anchors.

I8.3e. Detailing Requirements in Composite Components

This section gives the provisions for the minimum cover, minimum and maximum spacing of steel headed stud anchors and maximum spacing of steel channel anchors for composite components.

I9. SPECIAL CASES No changes have been made to this section.

CHAPTER J DESIGN OF CONNECTIONS

The major changes to this chapter include:

• Weld requirements revised to be consistent with AWS D1.1-2010 • The base metal strength for partial-joint-penetration (PJP) groove welds in tension has been

revised to use rupture strength rather than yield strength • To use provisions in Section J2.4 welds no longer need to be loaded “in-plane” • Two new groups, A and B, have been formed for high-strength bolt classification • Nominal shear strength in bearing-type connections has been increased by approximately 12.5% • The resistance and safety factors for column bases and bearing on concrete have been changed

The organization of this chapter remains the same. J1. GENERAL PROVISIONS

J1.1. Design Basis No changes have been made to this section.

J1.2. Simple Connections No changes have been made to this section. J1.3. Moment Connections No changes have been made to this section.

27

J1.4. Compression Members with Bearing Joints The following sentence has been added to improve clarity: “Compression members relying on bearing for load transfer shall meet the following requirements.”

J1.5. Splices in Heavy Sections

A fourth provision, filler metal requirements as given in Section J2.6, has been added for cases where tensile forces due to applied tension or flexure are to be transmitted through splices in heavy sections.

J1.6. Weld Access Holes

Beam cope provisions have been removed from this section. A minimum requirement of 1 ½ in. (38 mm) has been added for the length of an access hole from the toe of the weld preparation. The minimum height requirement for access holes has been changed from 1 in. (25 mm) to ¾ in. (19 mm).

J1.7. Placement of Welds and Bolts No changes have been made to this section. J1.8. Bolts in Combination with Welds No changes have been made to this section. J1.9. High-Strength Bolts in Combination with Rivets No changes have been made to this section. J1.10. Limitations on Bolted and Welded Connections

Slip-critical has been removed from the list of required joints in this section. J2. WELDS

Many of the revisions to the weld requirements in this section have been made to be consistent with AWS D1.1/D1.1M-2010.

J2.1. Groove Welds J2.1a. Effective Area No changes have been made to this section. J2.1b. Limitations No changes have been made to this section.

J2.2. Fillet Welds J2.2a. Effective Area No changes have been made to this section. J2.2b. Limitations

The minimum length requirements for fillet welds designed on the basis of strength have been changed to incorporate the actual length of the weld instead of its effective length. An equation for determining a weld’s effective length is now given in lieu of specifying the reduction factor, β, as 0.60 when the length of an end-loaded fillet weld exceeds 300 times its size.

28

The clause “when the required strength is less than that developed by a continuous fillet weld of the smallest permitted size” has been removed from the paragraph outlining the conditions in which intermittent fillet welds may be used. In addition to being used to transmit shear in lap joints, fillet welds in holes or slots are now permitted to be used to resist loads perpendicular to the faying surface in lap joints.

J2.3. Plug and Slot Welds J2.3a. Effective Area No changes have been made to this section. J2.3b. Limitations No changes have been made to this section. J2.4. Strength

The limit state of yielding is no longer applicable when determining the base material strength and the weld metal strength. See Table J2.5 discussion following. Welds are no longer required to be loaded “in-plane” to use the alternative provisions given in Sections J2.4(a), J2.4(b) and J2.4(c). Sections J2.4(a) and J2.4(c) now require that the weld group has “a uniform leg size.” Equation J2-7 has been added to the 2010 Specification and may be used to determine the nominal moment capacity of weld elements within a weld group that are analyzed using an instantaneous center of rotation method.

TABLE J2.5 Available Strength of Welded Joints, ksi (MPa)

The nominal strength of the base material has been altered in Table J2.5 to account for the removal of yielding as an applicable limit state when designing a partial-joint-penetration groove weld connection subjected to tension normal to the weld axis. The LRFD resistance and ASD safety factors have also been changed in Table J2.5 to account for a limit state of tensile rupture, as shown in the following table,

Changes to nominal strength of base material provisions for PJP welds. — 2005 Specification 2010 Specification

φ and Ω 0.901.67

φ =Ω =

0.752.00

φ =Ω =

Nominal strength, ksi (MPa) Fy Fu J2.5. Combination of Welds No changes have been made to this section. J2.6. Filler Metal Requirements No changes have been made to this section. J2.7. Mixed Weld Metal No changes have been made to this section.

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J3. BOLTS AND THREADED PARTS J3.1. High-Strength Bolts

High-strength bolts in the 2010 Specification are now grouped according to material strength as follows:

Group A Group B ASTM A325 ASTM A490

ASTM A325M ASTM A490M ASTM F1852 ASTM F2280

ASTM A354 Grade BC ASTM354 Grade BD ASTM A449 –

These new groups affect terminology and provisions throughout Section J3 of the 2010 Specification; all references to ASTM A325 or A325M bolts and all references to ASTM A490 or A490M bolts in the 2005 Specification have been changed to the terms “Group A” and “Group B,” respectively. Bolts are permitted to be installed to the snug-tight condition when used in bearing type connections, except as noted in Section E6 or Section J1.10. These exceptions were not listed in the 2005 Specification. The definition of the snug-tight condition has been simplified to the tightness required to bring the connected plies into firm contact. A user note has been added to this section stating that there are no specific minimum or maximum tension requirements for snug-tight bolts and fully pretensioned bolts such as ASTM F1852 or F2280 are permitted unless specifically prohibited on design drawings. When referring to meeting length and diameter requirements, the phrase “ASTM A325 and A325M, F1852, or A490 and A490M bolts” has been replaced by “the RCSC Specification limitations.” When using ASTM A354 Gr. BC, A354 Gr. BD, or A449 bolts and threaded rods in slip-critical connections, the bolt geometry to be compared to the bolt geometry required by the RCSC Specification now includes the thread pitch and the thread length in addition to the head and nut(s).

The conditions under which a single hardened washer conforming to ASTM F436 shall be used in lieu of the standard washer and its associated user note have been moved to Section J3.2 in the 2010 Specification. The paragraph referencing Section J3.10 for the provisions for adequate available bearing strength in slip-critical connections has been removed. TABLE J3.2 Nominal Strength of Fasteners and Threaded Parts, ksi (MPa) Several of the footnotes have been changed in Table J3.2:

• Footnote [a] now applies to the entire Nominal Tensile Strength column. It still references Appendix 3 requirements, but now applies to high-strength bolts subject to tensile fatigue loading.

• Footnote [b] in the 2005 Specification has been changed to [c] in the 2010 Specification. It now only applies to A307 bolts when determining the nominal shear strength in bearing-type connections.

30

• Footnote [c] in the 2005 Specification has been changed to [d] in the 2010 Specification.

• Footnote [d] in the 2005 Specification, which specifies the nominal tensile strength of the threaded portion of an upset rod, has been removed.

• Footnote [e] in the 2005 Specification, which references Appendix 3 for high-strength bolts subject to tensile fatigue loading, has been incorporated into Footnote [a] in the 2010 Specification.

• Footnote [b] in the 2010 Specification specifies that for end loaded connections with a fastener pattern length greater than 38 in. (965 mm), which was 50 in. (1270 mm) in the 2005 Specification, the nominal shear stress Fnv shall be reduced to 83.3% of the tabulated values (was 80% of the tabulated values in the 2005 Specification). This was footnote [f] in the 2005 Specification.

• Fastener pattern length has been redefined in footnote [b] as the maximum distance parallel to the line of force between the centerline of the bolts connecting two parts with one faying surface.

Values in Table J3.2 for the nominal shear strength in bearing-type connections have increased approximately 12.5% from their respective quantities in the 2005 Specification. The following table lists the changes per case.

— Nominal Shear Strength in Bearing-Type Connections, Fnv, ksi (MPa)

Description of Fasteners 2005 Specification 2010 Specification

A307 bolts 24 (165) 27 (188) Group A (e.g., A325)

bolts, when threads are not excluded from shear

planes

48 (330) 54 (375)

Group A (e.g., A325) bolts, when threads are

excluded from shear planes

60 (414) 68 (457)

Group B (e.g., A490) bolts, when threads are not excluded from shear

planes

60 (414) 68 (457)

Group B (e.g., A490) bolts, when threads are

excluded from shear planes

75 (520) 84 (579)

Threaded parts meeting the requirements of Section A3.4, when

threads are not excluded from shear planes

0.40Fu 0.450Fu

Threaded parts meeting the requirements of Section A3.4, when threads are excluded

from shear planes

0.50Fu 0.563Fu

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J3.2. Size and Use of Holes The conditions under which a single hardened washer conforming to ASTM F436 shall be used in lieu of the standard washer and its associated User Note have been moved to this section.

J3.3. Minimum Spacing

A user note has been added to this section, stating that ASTM F1554 anchor rods may be furnished in accordance to product specification with a body diameter less than the nominal diameter.

J3.4. Minimum Edge Distance No changes have been made to this section.

TABLE J3.4 Minimum Edge Distance from Center of Standard Hole to Edge of Connected Part In Tables J3.4 and J3.4M, footnotes [c] and [d] have been removed.

J3.5. Maximum Spacing and Edge Distance

A user note has been added to this section stating that dimensions which are listed just before the user note do not apply to elements consisting of two shapes in continuous contact.

J3.6. Tensile and Shear Strength of Bolts and Threaded Parts

The reference to footnote [d] of Table J3.2 has been removed from the definition of Ab. This change is consistent with the reorganization of Table J3.2. A user note has been added to this section stating that the strength of a bolt group be taken as the sum of the effective strengths of the individual fasteners, where the effective strength of an individual fastener may be taken as the lesser of the fastener shear strength based on the provisions of this section or that of the bearing strength at the bolt hole from the provisions of Section J3.10.

J3.7. Combined Tension and Shear in Bearing-Type Connections

The following has been added to the definition of frv to improve clarity: “required shear stress using LRFD or ASD load combinations, ksi (MPa)” In the user note, the upper limit for the required stress has been changed from 20% of the corresponding available stress to 30% of the corresponding available stress.

J3.8. High-Strength Bolts in Slip-Critical Connections

The available strength for slip-critical connections is now based on the limit state of slip and the limit states of bearing-type connections (this limit state was based on serviceability and slip in the 2005 Specification). The paragraph outlining when to design slip-critical connections based on the limit states of serviceability and slip has been removed. The statement that “slip-critical connections shall be designed as follows, unless otherwise designated by the engineer of record” has been removed. The following table summarizes the new provisions for slip-critical connection strength.

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Case φ (LRFD) Ω (ASD) For standard size and

shot-slotted holes perpendicular to the direction of the load

1.00 1.50

For oversized and shot-slotted holes parallel to the direction of the load

0.85 1.76

For long-slotted holes 0.70 2.14 The following terms in Equation J3-4 (the available slip resistance for the limit state of slip) have been changed in the 2010 Specification:

• The mean slip coefficient μ is now taken as 0.30 for Class A surfaces instead of 0.35.

• The hole factor, hsc, and its provisions have been removed in favor of hf, which is a factor for fillers. This factor is taken as 1.0 where there are no fillers or where bolts have been added to distribute loads in the filler, or where bolts have not been added to distribute the load in the filler for one filler between connected parts. Where bolts have not been added to distribute the load in the filler for two or more fillers between connected parts, this variable is taken as 0.85.

• The variable, Ns, has been changed to ns and is now taken as the number of slip planes required to permit the connection to slip.

Equation J3-4 has been changed to,

n u f b sR D h T n= μ

J3.9. Combined Tension and Shear in Slip-Critical Connections The variable for the number of bolts carrying the applied tension in a slip-critical connection, Nb, has been changed to nb. The variable for the factor to be multiplied to the available slip resistance per bolt, ks, has been changed to ksc.

J3.10. Bearing Strength at Bolt Holes

A user note has been added to this section: The strength of the bolt group is the sum of the effective strengths of the individual fasteners, where the effective strength of an individual fastener is the lesser of the fastener shear strength per Section J3.6 or the bearing strength at the bolt hole based on this section. The variable used for the clear distance, in the direction of the force, between the edge of the hole and the edge of the adjacent hole or edge of the material, Lc, has been changed to lc.

J3.11. Special Fasteners No changes have been made to this section. J3.12. Tension Fasteners No changes have been made to this section.

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J4. AFFECTED ELEMENTS OF MEMBERS AND CONNECTING ELEMENTS J4.1. Strength of Elements in Tension

A user note has been added to this section stating that the effective net area of the connection plate may be limited due to stress distribution as calculated by methods such as the Whitmore Section.

J4.2. Strength of Elements in Shear No changes have been made to this section. J4.3. Block Shear Strength No changes have been made to this section. J4.4. Strength of Elements in Compression No changes have been made to this section. J4.5. Strength of Elements in Flexure

This section is new to the 2010 Specification. It specifies that the available flexural strength of affected elements shall be the lower value obtained according to the limit states of flexural yielding, local buckling, flexural lateral-torsional buckling and flexural rupture.

J5. FILLERS This section has been reorganized into four subsections in the 2010 Specification. J5.1. Fillers in Welded Connections

Section J5.1 outlines the requirements to which fillers and the connecting welds shall conform.

J5.1a. Thin Fillers

Fillers less than ¼ in. (6 mm) thick shall not be used to transfer stress. Other provisions for thin fillers remain the same and have been reorganized in this section.

J5.1b. Thick Fillers

The provisions for thick fillers remain the same and have been reorganized in this section.

J5.2. Fillers in Bolted Connections

A minimum value of 0.85 is now given for the factor used to determine the shear strength of bolts, 1 0.4( 0.25).t− −

J6. SPLICES No changes have been made to this section. J7. BEARING STRENGTH No changes have been made to this section. J8. COLUMN BASES AND BEARING ON CONCRETE

The resistance and safety factors for column bases and for bearing on concrete have been changed from 0.60 to 0.65 and from 2.50 to 2.31 for LRFD and ASD, respectively.

J9. ANCHOR RODS AND EMBEDMENTS

It is now required that the design of column bases and anchor rods for the transfer of forces to a concrete foundation including bearing against the concrete elements shall satisfy the requirements of ACI 318 or ACI 349.

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A user note has been added to this section stating “When columns are required to resist a horizontal force at the base plate, bearing against the concrete elements should be considered.”

J10. FLANGES AND WEBS WITH CONCENTRATED FORCES J10.1. Flange Local Buckling No changes have been made to this section. J10.2. Web Local Buckling

In Equations J10-2 and J10-3 and in later equations listed in Section J10, the symbol used for the length of bearing, N, has been changed to lb.

J10.3. Web Local Crippling No changes have been made to this section.

J10.4. Web Sidesway Buckling In Equations J10-6 and J10-7, the symbol representing the largest laterally unbraced length along either flange at the point of load, l, has been changed to Lb.

J10.5. Web Compression Buckling No changes have been made to this section. J10.6. Web Panel Zone Shear

The symbol representing the column cross-sectional area, A, has been changed to Ag, and its definition has been changed to represent the gross cross-sectional area of the member.

J10.7. Unframed Ends of Beams and Girders No changes have been made to this section. J10.8. Additional Stiffener Requirements for Concentrated Forces

Stiffeners required to resist tensile concentrated forces shall now be designed in accordance with the requirements of Section J4.1 (was Chapter D in the 2005 Specification). The design requirements in Section J4.4 are the only provisions referenced when specifying the requirements for designing stiffeners that are required to resist compressive concentrated forces (was Sections E6.2 and J4.4 in the 2005 Specification). The thickness of a stiffener shall not be less than one-half the thickness of the flange or moment connection plate delivering the concentrated load, nor less than the width divided by 16 (was 15 in the 2005 Specification).

J10.9. Additional Doubler Plate Requirements for Concentrated Forces No changes have been made to this section.

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CHAPTER K DESIGN OF HSS AND BOX MEMBER CONNECTIONS

The major change to this chapter is the reorganization of the design provisions within this chapter into tabular form. In addition, most of these tables include figures of the connection types associated with the appropriate design equations. The user note referencing Section J3.10(c) for through-bolts has been updated; the last sentence of the chapter’s introductory paragraph in the 2005 Specification has been added to the user note. Two new user notes have been added to the Chapter K preamble:

• Connection strength is often governed by the size of HSS members, especially the wall thickness of truss chords, and this must be considered in the initial design.

• Connection parameters must be within the limits of applicability. Limit states need only be checked when connection geometry or loading is within the parameters given in the description of the limit state.

The chapter organization remains the same except for the addition of Section K4. K1. CONCENTRATED FORCES ON HSS

The limits of applicability that were listed in Section K1.2 in the 2005 Specification are now tabulated in Table K1.1A for round HSS and Table K1.2A for rectangular HSS in the 2010 Specification. Equation K4-4 (was Equation K1-7 in the 2005 Specification), which is used to calculate the total effective weld length for welds on both sides of the transverse plate for rectangular HSS, has been moved to Table K4.1. All user notes from the 2005 Specification have been removed from this section.

K1.1. Definitions of Parameters

The symbol representing the bearing length of the load, measured parallel to the axis of the HSS member, N, has been changed to lb. The variable Fc has been added to the 2010 Specification which represents the available stress (Fy for LRFD, 0.60Fy for ASD) in ksi (MPa).

K1.2. Round HSS

The available strength and limits of applicability criteria for round HSS connections subjected to a concentrated force are located in Tables K1.1 and K1.1A, respectively.

In Table K1.1, the available strength, Rn, in Equations K1-1 and K1-2 is now multiplied by sinθ, where θ is the plate load angle. Table K1.1A specifies θ to be greater than or equal to 30°. The definitions for Qf are now located in Table K1.1 under the subheading FUNCTIONS. The definition for U and any terms associated with that symbol are also tabulated there.

K1.3. Rectangular HSS

The available strength and limits of applicability criteria for rectangular HSS connections subjected to a concentrated force are located in Tables K1.2 and K1.2A, respectively.

36

The definitions for Qf are now located in Table K1.1 under the subheading FUNCTIONS. The definition for U and any terms associated with that symbol are also tabulated there. In Table K1.2, the available strength Rn in Equations K1-12 and K1-13 is now multiplied by sinθ, where θ is the plate load angle. Table K1.2A specifies θ to be greater than or equal to 30°.

K2. HSS-TO-HSS TRUSS CONNECTIONS

The following paragraph has been added to the 2010 Specification: “The design strength and allowable strength shall be determined in accordance with the provisions of this chapter and the provisions of Section B3.6.”

K2.1. Definitions of Parameters

The symbol representing the overlap length measured along the connecting face of the chord beneath the two branches, q, has been changed to lov. The symbol representing the projected length of the overlapping branch on the chord, p, has been changed to lp. The symbol representing the bearing length of the load, measured parallel to the axis of the HSS member, N, has been changed to lb.

K2.2. Round HSS

The available strength and limits of applicability criteria for round HSS-to-HSS truss connections are located in Tables K2.1 and K2.1A, respectively. The definitions for Qf are now located in Table K2.1 under the subheading FUNCTIONS. The definition for U and any terms associated with that symbol are also tabulated there.

K2.3. Rectangular HSS

The available strength and limits of applicability criteria for rectangular HSS-to-HSS truss connections are located in Tables K2.2 and K2.2A, respectively. The definitions for Qf are now located in Table K2.2 under the subheading FUNCTIONS. The definition for U and any terms associated with that symbol are also tabulated there.

Section K2.3e has been moved to Table K4.1 in Section K4. K3. HSS-TO-HSS MOMENT CONNECTIONS

The following statement has been added to this section: The design strength and the allowable strength of connections shall be determined in accordance with the provisions of this chapter and the provisions of Section B3.6.

K3.1. Definitions of Parameters No changes have been made to this section. K3.2. Round HSS

The available strength and limits of applicability criteria for round HSS moment connections are located in Tables K3.1 and K3.1A, respectively. Equation K3-4 (formerly Equation K3-6 in the 2005 Specification) has been revised with the removal of the variable Qf.

37

The definitions for Qf are now located in Table K3.1 under the subheading FUNCTIONS. The definition for U and any terms associated with that symbol are also tabulated there.

K3.3. Rectangular HSS

The available strength and limits of applicability criteria for rectangular HSS moment connections are located in Tables K3.2 and K3.2A, respectively. The definitions for Qf are now located in Table K3.2 under the subheading FUNCTIONS. The definition for U and any terms associated with that symbol are also tabulated there.

K4. WELDS OF PLATES AND BRANCHES TO RECTANGULAR HSS

This section is new to the 2010 Specification and specifies which provisions are to be used in addition to those contained in Section B3.6 to determine the design strength and allowable strength of welded connections. The available strength of welds shall be determined for the limit state of nonuniformity of load transfer along the line of weld and is given by,

or n n nw w eR P F t l= (K4-1) -n ip nw ipM F S= (K4-2) -n op nw opM F S= (K4-3)

where, Fnw = nominal stress of weld metal (Chapter J) with no increase in strength due to directionality

of load, ksi (MPa) Sip = effective elastic section modulus of welds for in-plane bending (Table K4.1), in.3 (mm3) Sop = effective elastic section modulus of welds for out-of-plane bending (Table K4.1), in.3

(mm3) le = total effective weld length of groove and fillet welds to rectangular HSS for weld strength

calculations, in. (mm) tw = smallest effective weld throat around the perimeter of branch or plate, in. (mm)

For fillet welds, φ = 0.75 (LRFD) and Ω = 2.00 (ASD). For partial-joint-penetration groove welds, φ = 0.80 (LRFD) and Ω = 1.88 (ASD). Table K4.1 may be used to determine le (formerly Le in the 2005 Specification). The weld provisions contained in Sections K1 and K2 have been moved to Table K4.1 in this section.

Design rules for T-, Y- and cross-connections under branch axial load or bending are now included in the 2010 Specification.

22

sinb

e eoiH

l b= +θ

(K4-5)

2

3 sin sinw b b

ip w eoit H H

S t b⎛ ⎞ ⎛ ⎞= +⎜ ⎟ ⎜ ⎟⎝ ⎠ ⎝ ⎠θ θ

(K4-6)

( )3

2 ( 3)( )sin 3

b w w b eoiop w b b

b

H t t B bS t B B

B−⎛ ⎞

= + −⎜ ⎟⎝ ⎠θ (K4-7)

10 yeoi b b

yb b

F tb B B

B t F t

⎛ ⎞= ≤⎜ ⎟

⎝ ⎠ (K2-13)

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CHAPTER L DESIGN FOR SERVICEABILITY

No major changes have been made to this chapter. The organization of this chapter remains the same. L1. GENERAL PROVISIONS

The user note in this section now references ASCE/SEI 7, Appendix C (was Appendix B in the 2005 Specification) for additional information on serviceability limit states, service loads and appropriate load combinations for serviceability requirements.

L2. CAMBER

The user note referencing the Code of Standard Practice for Steel Buildings and Bridges for camber recommendations has been removed.

L3. DEFLECTIONS No changes have been made to this section. L4. DRIFT No changes have been made to this section. L5. VIBRATION No changes have been made to this section. L6. WIND-INDUCED MOTION No changes have been made to this section. L7. EXPANSION AND CONTRACTION No changes have been made to this section. L8. CONNECTION SLIP

References to Sections J3.8 and J3.9 for the design of slip-critical connections have been moved into the user note.

CHAPTER M FABRICATION AND ERECTION

The major changes to this chapter include:

• Relocation of Section M5, Quality Control, to Chapter N, where it has been expanded upon • A reference to the AISC Code of Standard Practice is added in Section M4.

The organization of this chapter remains the same with the exception of Section M5 being relocated to Chapter N. M1. SHOP AND ERECTION DRAWINGS

The 2010 Specification states that shop and erection drawings may be prepared in stages. M2. FABRICATION M2.1. Cambering, Curving and Straightening No changes have been made to this section.

39

M2.2. Thermal Cutting Requirements for reentrant corners have been expanded upon:

• Reentrant corners shall be formed with a curved transition o The radius required to fit the connection is sufficient o A surface is not to be considered curved if it is the result of

two straight torch cuts meeting at a point • Discontinuous corners are permitted where the material on both sides

of the discontinuous reentrant corner are connected to a mating piece, which is used to prevent deformation and associated stress concentration at the corner

A user note has been added stating that reentrant corners with radii between a in. and 2 in. (10 mm and 13 mm) are acceptable for statically loaded work. In addition, a discontinuous reentrant corner may be used to fit pieces tightly together provided the pieces are connected close to the corner on both sides of the discontinuous corner. Also, slots in HSS for gussets may be made with semicircular ends or with curved corners, and square ends are permissible if the edge of the gusset is welded to the HSS. The statement requiring crack inspections in accordance with ASTM E709 for hot-rolled shapes with a flange thickness greater than 2 in. (50 mm) and built-up shapes with a material thickness greater than 2 in. (50 mm) has been removed from the 2010 Specification. The user note at the end of this section now references AWS C4.1-77 sample 2 instead of AWS C4.1-77 sample 3 as a guide for evaluating the surface roughness of copes in shapes with flanges not exceeding 2 in. (50 mm) thick.

M2.3. Planing of Edges No changes have been made to this section. M2.4. Welded Construction

No changes have been made to this section. M2.5. Bolted Construction

Water jet cut holes are now permitted. A user note has been added stating that AWS Surface Roughness Guide for Oxygen Cutting (AWS C4.1-77) sample 3 is referenced as a guide for evaluating the surface roughness of thermally cut holes.

M2.6. Compression Joints

No changes have been made to this section. M2.7. Dimensional Tolerances

The specific chapter (Chapter 6) in the AISC Code of Standard Practice for Steel Buildings and Bridges is now given when referencing requirements for dimensional tolerances.

M2.8. Finish of Column Bases

No changes have been made to this section. M2.9. Holes for Anchor Rods No changes have been made to this section.

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M2.10. Drain Holes No changes have been made to this section. M2.11. Requirements for Galvanized Members

The user note in this section now references Section M2.2 for copes of members to be galvanized.

M3. SHOP PAINTING M3.1. General Requirements

Chapter 6 in the AISC Code of Standard Practice for Steel Buildings and Bridges is now specifically referenced for shop painting and surface preparation requirements.

M3.2. Inaccessible Surfaces No changes have been made to this section. M3.3. Contact Surfaces No changes have been made to this section. M3.4. Finished Surfaces No changes have been made to this section. M3.5. Surfaces Adjacent to Field Welds No changes have been made to this section. M4. ERECTION M4.1. Column Base Setting

Chapter 7 of the AISC Code of Standard Practice for Steel Buildings and Bridges is now referenced.

M4.2. Stability and Connections

The title of this section has been renamed from Bracing. Chapter 7 of the AISC Code of Standard Practice for Steel Buildings and Bridges is now referenced. Additionally, the 2010 Specification incorporated former Section M4.7 (Field Connections in 2005 Specification) here, which requires that the structure be secured to support dead, erection and other loads anticipated to occur as erection progresses.

M4.3. Alignment No changes have been made to this section. M4.4. Fit of Column Compression Joints and Base Plates No changes have been made to this section. M4.5. Field Welding

The 2010 Specification specifically references wire brushing to assure weld quality for shop paints on surfaces adjacent to joints, if necessary. In addition, the 2010 Specification added a paragraph on field welding of attachments to installed embedments in contact with concrete. Specifically, these attachments should be welded such that excessive thermal expansion of the embedment is avoided. Excessive thermal expansion may cause the concrete to spall or crack and may cause excessive stress in the embedment anchors.

41

M4.6. Field Painting No changes have been made to this section.

CHAPTER N QUALITY CONTROL AND QUALITY ASSURANCE

This chapter is new to the 2010 Specification and addresses minimum requirements for quality control, quality assurance and nondestructive testing for structural steel systems and steel elements of composite members for buildings and other structures. This chapter replaces Section M5 of the 2005 Specification. N1. SCOPE

This new section defines quality control as being provided by fabricator or erector. Quality assurance is provided by others when required by the authority having jurisdiction (AHJ), purchaser, owner or engineer of record (EOR).

N2. FABRICATOR AND ERECTOR QUALITY CONTROL PROGRAM

The first sentence of the preamble to Section M5 of the 2005 Specification has been moved to this section, and it has been expanded upon to include lists of minimum requirements for both the fabricator’s and the erector’s quality control inspector.

N3. FABRICATOR AND ERECTOR DOCUMENTS N3.1. Submittals for Steel Construction

This new section lists documents that the fabricator or erector shall submit for review by the EOR or the EOR’s designee prior to fabrication or erection.

N3.2. Available Documents for Steel Construction

This new section lists documents that shall be available in electronic or printed form for review by the EOR or the EOR’s designee prior to fabrication or erection.

N4. INSPECTION AND NONDESTRUCTIVE TESTING PERSONNEL N4.1. Quality Control Inspector Qualifications

This new section states that “quality control welding inspection personnel shall be qualified to the satisfaction of the fabricator’s or erector’s quality control program.” This section lists qualifications that the quality control personnel must meet.

N4.2. Quality Assurance Inspector Qualifications

This new section states that “quality assurance welding inspectors shall be qualified to the satisfaction of the quality assurance agency’s written practice.” This section lists the qualifications that the quality assurance personnel must meet.

N4.3. NDT Personnel Qualifications

This new section states that “nondestructive testing personnel, for NDT other than visual, shall be qualified in accordance with their employer’s written practice.” This section goes on to list documents whose criteria should be met (or exceeded by) the employer’s written practice.

42

N5. MINIMUM REQUIREMENTS FOR INSPECTION OF STRUCTURAL STEEL BUILDINGS

N5.1. Quality Control

This new section references Sections N5.4, N5.6 and N5.7 for quality control inspection tasks to be performed by the fabricator’s or erector’s quality control inspector, which are listed in Tables N5.4-1 through N5.4-3 and Tables N5.6-1 through N5.6-3. This section also defines the applicable construction documents for quality control inspection as the shop drawings and the erection drawings, in addition to “the applicable referenced specifications, codes and standards.”

N5.2. Quality Assurance

This new section references Sections N5.4, N5.6 and N5.7 for quality assurance inspection tasks. This section also specifies that the quality assurance agency shall submit inspection reports and nondestructive testing reports to the AHJ, EOR or owner as well as the fabricator and erector.

N5.3. Coordinated Inspection

This new section states that if a task is noted to be performed by both quality control and quality assurance, then it is permissible to have the inspection functions performed by only party if it is coordinated between the quality control inspector and the quality assurance inspector. This section states that if the work is performed by the quality control inspector, approval from the AHJ and EOR is required.

N5.4. Inspection of Welding

Section M5.3 of the 2005 Specification has been moved to this section, and it has been expanded upon. One such expansion is the addition of three tables (Tables N5.4-1, N5.4-2 and N5.4-3) that provide the minimum required welding inspection tasks.

The first paragraph of Section M5.3 of the 2005 Specification is now a user note in this section.

N5.5. Nondestructive Testing of Welded Joints N5.5a. Procedures

This new section lists different tests that shall be performed by quality assurance in accordance with AWS D1.1/D1.1M.

N5.5b. CJP Groove Weld NDT

This new section specifies ultrasonic testing procedures to be performed by quality assurance for certain CJP welds based on the structure’s Risk Category according to ASCE/SEI 7. The user note in this section states that “for structures in Risk Category I or material less than c in. thick, NDT of CJP groove welds is not required.”

N5.5c. Access Hole NDT

This new section specifies when quality assurance should test thermally cut surfaces of access holes using magnetic particle testing or penetrant testing. This section also states that “any crack shall be deemed unacceptable regardless of size or location.”

N5.5d. Welded Joints Subjected to Fatigue

This new section states that the quality assurance shall establish weld soundness by radiographic or ultrasonic inspection when required by Appendix 3, Table A-

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3.1. This section also specifies that reducing the rate of ultrasonic testing is prohibited.

N5.5e. Reduction of Rate of Ultrasonic Testing

This new section specifies that the rate of ultrasonic testing is permitted to be reduced to 25% (where the initial rate for ultrasonic testing is 100%), given certain provisions outlined further in the section are followed. This section also states that the EOR and the AHJ must approve this reduction.

N5.5f. Increase in Rate of Ultrasonic Testing

This new section outlines the provisions under which the rate of ultrasonic testing shall be increased to 100% (where the initial rate for ultrasonic testing is 10%) for structures in Risk Category II.

N5.5g. Documentation

This new section specifies that “all NDT performed shall be documented,” it also lists specific items that the NDT report shall identify and/or indicate.

N5.6. Inspection of High-Strength Bolting

Section M5.4 of the 2005 Specification has been moved to this section, and it has been expanded upon. Similar to Section N5.4, three tables have been added that list the minimum required bolting inspection tasks.

N5.7. Other Inspection Tasks

This new section lists what the fabricator’s and erector’s quality control personnel shall inspect and the documents that are used to verify compliance. Also included in this section are the requirements for the quality assurance personnel and the documents that are used.

N6. MINIMUM REQUIREMENTS FOR INSPECTION OF COMPOSITE CONSTRUCTION This new section lists the tasks associated with inspection of structural steel and steel deck used in

composite construction. N7. APPROVED FABRICATORS AND ERECTORS This new section specifies when quality assurance inspections may be waived for approved

fabricators and erectors. It also states when NDT may be performed by approved fabricators. This section also states when the fabricator and erector should submit their individual certificates of compliance, and it also specifies what should be stated within these certificates of compliance.

N8. NONCOMFORMING MATERIAL AND WORKMANSHIP Section M5.2 of the 2005 Specification has been moved to this section, and it has been expanded

upon to include instructions on dealing with nonconforming material and to include specific reports that the quality assurance agency shall submit to the fabricator and erector in addition to the AHJ and EOR or owner.

The specification for timely, in-sequence inspections is an implication from Section M5.1 of the

2005 Specification.

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APPENDIX 1 DESIGN BY INELASTIC ANALYSIS

The major changes to this appendix are the clarification on how to design using inelastic analysis and the relocation of moment redistribution to Sections B3.7 and F13.5. This appendix has been reorganized into three main sections. 1.1. GENERAL REQUIREMENTS

Sections 1.8 and 1.9 of the 2005 Specification have been moved here and expanded upon; additional requirements for inelastic analysis have also been added. In addition, this section now outlines the basic procedure for performing an inelastic analysis and introduces the other sections in the appendix.

1.2. DUCTILITY REQUIREMENTS

1.2.1. Material Section 1.2 of the 2005 Specification has been moved to this section and reworded to provide clarity.

1.2.2. Cross Section

Section 1.4 of the 2005 Specification has been moved to this section. The controlling width-to-thickness ratio, λpd, is now explicitly calculated; all inequalities from the 2005 Specification have been replaced by equations calculating this limit. It is now stated prior to each equation that the applicable width-to-thickness ratio of the section may not exceed λpd.

1.2.3. Unbraced Length Section 1.7 of the 2005 Specification has been moved to this section.

Equations A-1-7 and A-1-8 from the 2005 Specification have been modified as follows,

1

2

'0.12 0.076pd y

y

M EL rM F

⎡ ⎤= −⎢ ⎥

⎣ ⎦ (A-1-5)

1

2

'0.17 0.10 0.10pd y y

y y

M E EL r rM F F

⎡ ⎤= − ≥⎢ ⎥

⎣ ⎦ (A-1-7)

The value of M1' is determined by using either: Equation A-1-6a, Equation A-1-6b or Equation A-1-6c of the 2010 Specification, whichever case is applicable. These equations also incorporate the moment at the middle of the unbraced length, Mmid, and both M1 and Mmid are taken as positive when they cause compression in the same flange as M2. Note that the definitions of M1 and M2 have not changed from the 2005 Specification. These new equations are similar to Equations A-1-7 and A-1-8 from the 2005 Specification, but they now allow for Lpd to be explicitly calculated without determining whether reverse curvature or single curvature are present. A third case has been added for which there is no Lpd limit: members subject only to tension.

1.2.4. Axial Force

This section is based on Sections 1.5.1 and 1.5.2 of the 2005 Specification and states that the compressive design strength for compression members with

45

plastic hinges shall not exceed 0.75FyAg, regardless of the frame type. In the 2005 Specification, moment frames had the same design limit, but braced frames could be designed up to 0.85FyAg.

1.3. ANALYSIS REQUIREMENTS

1.3.1. Material Properties and Yield Criteria This section includes material properties and yield criteria that must be included in the inelastic analysis that were previously specified in Sections 1.5, 1.6, 1.7, and 1.8 of the 2005 Specification. The 2010 Specification, however has put all these analysis requirements in one section.

1.3.2. Geometric Imperfections

Initial geometric imperfections must be taken into account during an inelastic analysis; this was not specified in the 2005 Specification.

1.3.3. Residual Stress and Partial Yielding Effects

The effect of residual stresses and partial yielding must be part of the inelastic analysis; this was not specified in the 2005 Specification.

APPENDIX 2 DESIGN FOR PONDING

No major changes have occurred within this appendix. The organization of this appendix remains the same. 2.1. SIMPLIFIED DESIGN FOR PONDING

Lp and Ls have had their definitions simplified to the length of primary members and the length of secondary members, respectively. The 15% reduction in the moment of inertia, Is, is now stated as a suggestion rather than a specification in a new User Note. The effects of member strain should be included when determining Ip and Is for trusses and steel joists.

2.2. IMPROVED DESIGN FOR PONDING

Some language has been modified to improve clarity.

APPENDIX 3 DESIGN FOR FATIGUE

No major changes have been made to this appendix chapter. The organization of this appendix remains the same, except that title of Section 3.3 has been changed from Design Stress Range to Plain Material and Welded Joints. A user note has been added referencing the AISC Seismic Provisions for structures subject to seismic loads. 3.1. GENERAL PROVISIONS The situations in which evaluation of fatigue resistance is not required have been expanded upon.

46

3.2. CALCULATION OF MAXIMUM STRESSES AND ALLOWABLE STRESS RANGES No changes have been made to this section. 3.3. PLAIN MATERIAL AND WELDED JOINTS

The symbol for the number of stress range fluctuations in a design life, N, has been changed to nSR. 3.4. BOLTS AND THREADED PARTS

For high-strength bolts, common bolts, and threaded anchor rods with cut, ground or rolled threads, the factors Cf and FTH are no longer specified to be taken as 3.9 × 108 and 7 ksi (48 MPa), respectively. The symbol for pitch, P, has been changed to p.

3.5. SPECIAL FABRICATION AND ERECTION REQUIREMENTS

The 2010 Specification now specifies that longitudinal backing, if left in place, shall be attached with continuous fillet welds. A user note has been added stating that AWS C4.1 Sample 3 may be used to evaluate compliance with the requirement that the surface roughness of thermally cut edges subject to cyclic stress ranges shall not exceed 1000 μin. (25 μm).

TABLE A-3.1 Fatigue Design Parameters

The following are the revisions that have been made to Table A-3.1 in the 2010 Specification: • Parts of Table A-3.1 have been reworded for clarity. • Figure 1.3 of Table A-3.1 now shows a zoomed-in illustration of a bolt hole

from Figures 1.3a and 1.3b. • A clarification has been added to Figure 1.4; Figure 1.4c is Figure 1.4b as seen

with the bracing removed. • A note has been added to Figure 2.1: Figures are for slip-critical bolted

connections. • A note has been added to Figure 2.2: Figures are for bolted connections

designed to bear, meeting the requirements of slip-critical connections. • A note has been added to Figure 2.3: Figures are for snug-tightened bolts, rivets,

or other mechanical fasteners. • Figure 2.3c, which is similar to Figures 2.1c and 2.2c, has been added. • Figure 3.2c, which is a zoomed-in illustration of the crack depicted in Figure

3.2b, has been added. • Figure 3.4c has been removed. • The thickness criteria, t, for determining Cf and FTH in Section 4.1 has been

changed from 0.8 in. (20 mm) to 0.5 in. (12 mm). • Sections 5.1 through 5.4 and Sections 6.1 through 6.3 now specify that weld

soundness must be established by radiographic or ultrasonic inspection in accordance with the requirements of subclauses 6.12 or 6.13 of AWS D1.1/D1.1M.

• Figure 5.6c has been modified to include a zoomed-in illustration of a crack in the cross section of the fillet weld.

• Figure 5.6d has been added. • The note under Figure 5.7c has been removed. • Figure 6.3c, which depicts a grinded transition of two plates of unequal

thickness, has been added. • Figure 6.4c, which is similar to Figure 6.3c, has been added. • The provisions in Section 7.1 for selecting stress categories E and E’ have

changed, as shown in the following table:

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Stress Category 2005 Specification 2010 Specification

E 12 or 4 in. (100 mm)a b>

when b is ≤ 1 in. (25 mm) a > 4 in. (100 mm)

when b > 0.8 in. (20 mm)

E’ 12 or 4 in. (100 mm)a b>

when b is > 1 in. (25 mm) a > lesser of 12b or 4 in. (100 mm)

when b ≤ 0.8 in. (20 mm) • Figures 7.1c and 7.1d are now Figures 7.1d and 7.1e, respectively; Figure 7.1c is

a new illustration. • A zoomed-in illustration of the crack in Figure 8.1b has been added. • The potential crack initiation point of Section 8.2 has been modified. • Figure 8.4b, which is similar to Figure 8.3b, has been added.

APPENDIX 4 STRUCTURAL DESIGN FOR FIRE CONDITIONS

The major changes in this appendix chapter include the revisions made to Section 4.2.4.3b, Simple Methods of Analysis. They include changes to the design provision for both compression and flexural members. The organization of this appendix remains the same. 4.1. GENERAL PROVISIONS Terms that were defined in this section in the 2005 Specification have been moved to the Glossary in the 2010 Specification. 4.1.1. Performance Objective No changes have been made to this section. 4.1.2. Design by Engineering Analysis

It is now required that the load and resistance factor design method, in accordance with the provisions of Section B3.3, be used for structural design for fire conditions.

4.1.3. Design by Qualification Testing No changes have been made to this section. 4.1.4. Load Combinations and Required Strength

The phrase “authority having jurisdiction” has been replaced by “applicable building code.”

4.2. STRUCTURAL DESIGN FOR FIRE CONDITIONS BY ANALYSIS 4.2.1. Design-Basis Fire No changes have been made to this section. 4.2.1.1. Localized Fire No changes have been made to this section. 4.2.1.2. Post-Flashover Compartment Fires

The paragraph in Section 4.2.1.4, Fire Duration, from the 2005 Specification has been moved to this section.

4.2.1.3. Exterior Fires No changes have been made to this section.

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4.2.1.4. Active Fire Protection System

Because Fire Duration is now incorporated into Section 4.2.1.2, Active Fire Protection System was moved from Section 4.2.1.5 to Section 4.2.1.4.

4.2.2. Temperatures in Structural Systems under Fire Conditions No changes have been made to this section. 4.2.3. Material Strengths at Elevated Temperatures The coefficient of expansion, kp, was added to Table A-4.2.1 and is defined as,

( ) /p p yk F T F=

Asterisks, which designated the use of ambient properties, have been removed from Table A-4.2.1 and replaced with 1.00.

4.2.3.1. Thermal Elongation No changes have been made to this section. 4.2.3.2. Mechanical Properties at Elevated Temperatures

The proportional limit at elevated temperatures, Fp(T), is now defined in this section and it is calculated as a ratio to yield strength as specified in Table A-4.2.1. All the terms listed in this section are now shown as being functions of temperature. The elastic shear modulus, G, has also been added to these terms.

TABLE A-4.2.2 Properties of Concrete at Elevated Temperatures

A subheading in Table A-4.2.2 has been corrected; the values of εcu(T) are now representative of normal weight concrete instead of lightweight concrete.

4.2.4. Structural Design Requirements

4.2.4.1. General Structural Integrity No changes have been made to this section. 4.2.4.2. Strength Requirements and Deformation Limits No changes have been made to this section. 4.2.4.3. Methods of Analysis 4.2.4.3a. Advanced Methods of Analysis No changes have been made to this section. 4.2.4.3b. Simple Methods of Analysis

A new provision states that the member and connection design strengths shall be determined without consideration of temperature effects for steel temperatures less than or equal to 400 °F (204 °C). A new user note explains that the degradation in steel at these temperatures need not be considered in calculating member strengths.

4.2.4.3b(1) Tension Members No changes have been made to this section.

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4.2.4.3b(2) Compression Members A new equation has been introduced that is to be used in lieu of Equations E3-2 and E3-3 in determining the nominal compressive strength for flexural buckling:

( )

( )( ) 0.42 ( )y

e

F TF T

cr yF T F T⎡ ⎤⎢ ⎥=⎢ ⎥⎣ ⎦

(A-4-2)

where, Fy(T) = yield stress at elevated temperature

Fe(T) = critical elastic buckling stress calculated from Equation E3-4 with the elastic modulus E(T) at elevated temperature

4.2.4.3b(3) Flexural Members

Equations A-4-3 to A-4-10 have been introduced that are to be used in lieu of Equations F2-2 through F2-6 in determining the nominal flexural strength for lateral-torsional buckling of laterally unbraced doubly symmetric members: When ( )b rL L T≤

( ) ( ) ( ) ( ) 1( )

xcb

n b r p rr

LM T C M T M T M T

L T

⎡ ⎤⎡ ⎤⎡ ⎤⎢ ⎥= + − −⎢ ⎥⎣ ⎦⎢ ⎥⎣ ⎦⎣ ⎦

(A-4-3)

When ( )b rL L T> ( ) ( )n cr xM T F T S= (A-4-4)

where,

Fcr(T) 22

2

( )1 0.078b b

x o tsb

ts

C E T LJcS h rL

r

⎛ ⎞π= + ⎜ ⎟⎝ ⎠⎛ ⎞

⎜ ⎟⎝ ⎠

( A-4-5)

Lr(T) 2 2

( )( )1.95 6.76( ) ( )

Lts

L x o x o

F TE T Jc JcrF T S h S h E T

⎛ ⎞ ⎡ ⎤= + + ⎢ ⎥⎜ ⎟⎝ ⎠ ⎣ ⎦

(A-4-6)

Mr(T) ( )x LS F T= (A-4-7) FL(T) ( 0.3 )y p yF k k= − (A-4-8) Mp(T) ( )x yZ F T= (A-4-9)

cx 0.53 3.0450T

= + ≤ where T is in °F (A-4-10)

cx 0.6 3.0250T

= + ≤ where T is in °C (S.I.) (A-4-10M)

4.2.4.3b(4) Composite Floor Members No changes have been made to this section. 4.2.4.4. Design Strength No changes have been made to this section. 4.3. DESIGN BY QUALIFICATION TESTING 4.3.1. Qualification Standards No changes have been made to this section.

50

4.3.2. Restrained Construction No changes have been made to this section. 4.3.3. Unrestrained Construction No changes have been made to this section.

APPENDIX 5 EVALUATION OF EXISTING STRUCTURES

No major changes have been made to this appendix chapter. The organization of this appendix remains the same.

APPENDIX 6 STABILITY BRACING FOR COLUMNS AND BEAMS

A major change to this appendix chapter is the addition of beam-column bracing provisions. The organization of this appendix remains the same, with the exception of the addition of Section 6.4, Beam-Column Bracing. 6.1. GENERAL PROVISIONS

Parts of this section have been reworded and reorganized to improve clarity. A paragraph has been added to the beginning of this section that outlines the design basis for columns and beams with respect to unbraced length.

The definitions of a relative brace and of a nodal brace have been moved to a new user note.

6.2. COLUMN BRACING 6.2.1. Relative Bracing No changes have been made to this section. 6.2.2. Nodal Bracing

The last sentence of the preamble to Section 6.2 (It is assumed that nodal braces are equally spaced along the column) has been moved to a new user note in this section in the 2010 Specification.

6.3. BEAM BRACING Parts of the preamble to this section have been reworded and reorganized for clarity. 6.3.1. Lateral Bracing This section has been reorganized to improve clarity. 6.3.1a. Relative Bracing

The symbol representing the required brace strength has been changed from Pbr to Prb.

6.3.1b. Nodal Bracing No changes have been made to this section.

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6.3.2. Torsional Bracing

The first and last sentences of this section have been removed.

A user note has been added stating that torsional bracing can be provided with a moment-connected beam, cross frame, or other diaphragm element.

6.3.2a. Nodal Bracing

The symbol representing the required strength of nodal bracing, Mbr, has been changed to Mrb. The sentence describing the consequences of sec Tβ < β has been moved to a new user note.

6.3.2b. Continuous Bracing This section has been reorganized to improve clarity. 6.4. BEAM-COLUMN BRACING

This section is new to the 2010 Specification, and it outlines how to determine the required strength and stiffness of beam-columns per various lateral bracing and torsional bracing cases.

APPENDIX 7 ALTERNATIVE METHODS OF DESIGN FOR STABILITY

A major change made to this appendix chapter is the addition of several provisions from Chapter C of the 2005 Specification. This appendix has been renamed and reorganized as follows:

• Title of this appendix chapter has been changed from Direct Analysis Method to Alternative Methods of Design for Stability.

• The titles of Sections 7.2 and 7.3 have been changed from Notional Loads and Design-Analysis Constraints to Effective Length Method and First-Order Analysis Method, respectively.

7.1. GENERAL STABILITY REQUIREMENTS

Sections C1 and C2 are now referenced here, and the effective length method and first-order analysis method are introduced.

7.2. EFFECTIVE LENGTH METHOD 7.2.1. Limitations

Parts of Section C2.2 of the 2005 Specification have been moved here and reorganized to improve clarity. The 1.6 factor for ASD load combinations has been removed from the user note and has been placed in a list of conditions in this section.

7.2.2. Required Strengths

Parts of Section C2.2 of the 2005 Specification have been moved here and reorganized to improve clarity. A user note has been added that explains why the notional load need only be applied in gravity-only load cases.

52

7.2.3. Available Strengths

Sections C1.3a, C1.3b and C1.3c of the 2005 Specification have been moved to this section and represent the provisions for determining the effective length factor, K.

7.3. FIRST-ORDER ANALYSIS METHOD 7.3.1. Limitations

The first two limitations presented in this section are equivalent to those presented in Section 7.2.1. As such, these limitations have been moved from Section C2.2 of the 2005 Specification to this section. The final limitation has been moved to this section from Section C2.2b of the 2005 Specification.

7.3.2. Required Strengths

The requirements listed in this section (additional lateral load, Ni, and the nonsway amplification of beam-column moments) have been moved from Section C2.2b of the 2005 Specification to this section. Equation A-7-2 (was Equation C2-8 in the 2005 Specification) has been modified to include α which is an amplification term that is equal to 1.0 under LRFD load combinations and 1.6 under ASD load combinations:

2.1 ( ) 0.0042i i iN L Y Y= α Δ ≥ (A-7-2) Due to the addition of α in the previous equation, the user note instructing Δ to be multiplied by 1.6 (if ASD load combinations were used) has been deleted.

7.3.3. Available Strengths

The first two paragraphs of Section C1.2 of the 2005 Specification have been moved to this section.

It is specified in this section that the effective length factor, K, of all members shall be taken as unity. A user note referencing Appendix 6 for methods of satisfying bracing requirements has been added.

APPENDIX 8 APPROXIMATE SECOND-ORDER ANALYSIS

This appendix is new to the 2010 Specification. The approximate second order analysis (B1-B2) method has been moved from Chapter C. 8.1. LIMITATIONS

This section is new to the 2010 Specification, and it states the limitations of this analysis procedure. It also states that it’s permissible to use this method to determine the P-δ of any individual compression member.

8.2. CALCULATION PROCEDURE (was Section C2.1b)

The equations for calculating the second-order flexural and axial strength remains the same. The following provision has been added, B1 shall be taken as 1.0 for members not subjected to

53

compression. The user note stating for B1 ≤ 1.05 it is conservative to amplify the sum of the non-sway and sway moments by the B2 amplifier has been removed from this section.

8.2.1. Multiplier B1 for P-δ Effects

The equations used for calculating B1 have remained the same. The term “zero sidesway” has been changed to “no lateral translation at the member ends” in the definition of Pe1. The definition of EI has been expanded to include the required flexural rigidity required for both the direct analysis method (= 0.8τbEI) and the first-order analysis method. A statement has been added stating that the use of the first-order estimate of, Pr, is permitted in the B1 equation.

8.2.2. Multiplier B2 for P-Δ Effects

In the equation for B2 the variable ΣPnt has been changed to Pstory and ΣPe2 has been changed to Pe story. The Pe2 equation for moment frames which uses K2, has been removed. The equation for Pe2 in the 2005 Specification has been changed as follows:

2005 Specification

2e MH

HLP R ΣΣ =

Δ (C2-6b)

2010 Specification

e story MH

HLP R=Δ

(A-8-7)

The variable RM has been changed from equal to 0.85 for moment frames and 1.0 for braced frames to the following equation:

( )1 0.15 /M mf storyR P P= − (A-8-8)

The variable Pmf is the total vertical load in columns in the story that are part of moment frames (=0 for braced frame systems).