Aisc 341_16 seismic provisions for structural steel buildings

AISC 360, Specification for Structural Steel Buildings (ANSIAISC 36016) is intended to cover common design criteria. Accordingly, it is not feasible for it to also cover all of the special and unique problems encountered within the full range of structural design prac tice. This document, Seismic Provisions for Structural Steel Buildings (ANSIAISC 34116) (hereafter referred to as the Provisions), is a separate consensus standard that addresses one such topic: the design and construction of structural steel and composite structural steel reinforced concrete building systems specifically detailed for seismic resistance. The Symbols, Glossary, and Abbreviations are all considered part of this document. Accompanying the Provisions is a nonmandatory Commentary with background infor mation and nonmandatory user notes interspersed throughout to provide guidance on the specific application of the document.

Material Specifications

Structural steel used in the seismic force-resisting system (SFRS) shall satisfy the requirements of Specification Section A3.1, except as modified in these Provisions

The maximum specified minimum yield stress for structural steel used in members expected to exhibit inelastic behavior is capped at 50 ksi (345 MPa) This limitation applies to systems outlined in Chapters E, F, G, and H, with specific exceptions for those defined in Sections E1 and F1.

The specified minimum yield stress limits for G1, H1, and H4 materials should not exceed 55 ksi (380 MPa) However, these limits can be surpassed if the material's suitability is confirmed through testing or other rational criteria.

Exception: Specified minimum yield stress of structural steel shall not exceed 70 ksi

(485 MPa) for columns in systems defined in Sections E3, E4, G3, H1, H2 and H3 and for columns in all systems in Chapter F.

The structural steel used in the SFRS described in Chapters E, F, G and H shall meet one of the following ASTM Specifications:

ASTM A36/A36M ASTM A529/A529M ASTM A572/A572M [Grade 42 (290), 50 (345) or 55 (380)]

ASTM A588/A588M ASTM A1011/A1011M HSLAS Grade 55 (380) ASTM A1043/A1043M

ASTM A36/A36M ASTM A529/A529M ASTM A572/A572M [Grade 42 (290), 50 (345) or 55 (380)]

The structural steel used for column base plates shall meet one of the preceding

ASTM specifications or ASTM A283/A283M Grade D Other steels and nonsteel materials in buckling-restrained braced frames are permitted to be used subject to the requirements of Sections F4 and K3.

This section focuses exclusively on the material properties of structural steel utilized in the Special Framework for Seismic Resistance (SFRS), as defined in Section 2.1 of the AISC Code of Standard Practice It is important to note that this discussion does not encompass other types of steel, such as cables used for permanent bracing, nor does it include steel reinforcement found in composite components.

SFRS is covered in Section A3.5.

Expected Material Strength

When required in these Provisions, the required strength of an element (a member or a connection of a member) shall be determined from the expected yield stress,

The yield stress ratio, R y, is defined as the expected yield stress compared to the specified minimum yield stress, F y, of the steel used in a structural member or its adjoining member.

When required to determine the nominal strength, R n , for limit states within the same member from which the required strength is determined, the expected yield stress,

In construction and engineering, R y F y and R t F u can be utilized as substitutes for F y and F u, where F u represents the minimum specified tensile strength Here, R t denotes the ratio of the expected tensile strength to the specified minimum tensile strength, F u, of the material in question.

In certain situations, it is essential to design a member or its connection limit state for forces that correspond to the member's expected strength This includes calculating the nominal strength, Rn, of beams outside the link in eccentrically braced frames and assessing diagonal brace rupture limit states, such as block shear rupture and net section rupture in Special Concentrically Braced Frames (SCBF) In these cases, using the expected material strength is allowed to determine the available member strength However, for connecting elements and other members, the specified material strength must be utilized.

Table A3.1 provides the values of R y and R t for different steel and steel reinforcement materials Alternative R y and R t values may be used if they are obtained through testing specimens that are comparable in size and source to the intended materials, conducted in accordance with the ASTM specifications for the specified grade of steel.

User Note: The expected compressive strength of concrete may be estimated using values from Seismic Rehabilitation of Existing Buildings (ASCE/SEI 41-13).

Heavy Sections

For structural steel in the SFRS, in addition to the requirements of Specification Sec- tion A3.1c, hot rolled shapes with flange thickness equal to or greater than 12 in

(38 mm) shall have a minimum Charpy V-notch (CVN) toughness of 20 ft-lb (27

J) at 70°F (21°C), tested in the alternate core location as described in ASTM A6

Supplementary Requirement S30 Plates with thickness equal to or greater than 2 in

(50 mm) shall have a minimum Charpy V-notch toughness of 20 ft-lb (27 J) at 70°F

R y and R t Values for Steel and Steel Reinforcement Materials

Hot-rolled structural shapes and bars:

(21°C), measured at any location permitted by ASTM A673, Frequency P, where the plate is used for the following:

(a) Members built up from plate

(b) Connection plates where inelastic strain under seismic loading is expected

(c) The steel core of buckling-restrained braces

Consumables for Welding

4a Seismic Force-Resisting System Welds

All welds used in members and connections in the SFRS shall be made with filler metals meeting the requirements specified in clauses 6.1, 6.2 and 6.3 of Structural

Welding Code—Seismic Supplement (AWS D1.8/D1.8M), hereafter referred to as

User Note: AWS D1.8/D1.8M clauses 6.2.1, 6.2.2, 6.2.3, and 6.3.1 apply only to demand critical welds.

Welds designated as demand critical shall be made with filler metals meeting the requirements specified in AWS D1.8/D1.8M clauses 6.1, 6.2 and 6.3.

User Note: AWS D1.8/D1.8M requires that all seismic force-resisting system welds are to be made with filler metals classified using AWS A5 standards that achieve the following mechanical properties:

Filler Metal Classification Properties for Seismic

CVN Toughness, ft-lb (J) a 20 (27) min @ 0°F (−18°C) a 25 (34) min @

− 20°F ( − 30°C) a Filler metals classified as meeting 20 ft-lbf (27 J) min at a temperature lower than 0°F (−18°C) also meet this requirement.

AWS D1.8/D1.8M mandates that, unless exempted from testing, all demand critical welds must utilize filler metals that undergo Heat Input Envelope Testing, ensuring they meet specific mechanical property standards in the weld metal.

Mechanical Properties for Demand Critical Welds

Yield Strength, ksi (MPa) 58 (400) min 68 (470) min 78 (540) min.

Tensile Strength, ksi (MPa) 70 (480) min 80 (550) min 90 (620) min.

CVN Toughness, ft-lb (J) b, c 40 (54) min @ 70°F (20°C) 40 (54) min @

50°F (10°C) b For LAST of +50°F (+10°C) For LAST less than +50°F (+10°C), see AWS D1.8/D1.8M clause 6.2.2. c Tests conducted in accordance with AWS D1.8/D1.8M Annex A meeting 40 ft-lb (54 J) min at a temperature lower than +70°F (+20°C) also meet this requirement.

Concrete and Steel Reinforcement

Concrete and steel reinforcement in composite components for special SFRS in Sections G2, G3, G4, H2, H3, H5, H6, and H7 must comply with ACI 318 Chapter 18 standards Meanwhile, the concrete and steel reinforcement for ordinary SFRS in Sections G1, H1, and H4 should adhere to the requirements outlined in ACI 318 Section 18.2.1.4.

A4 STRUCTURAL DESIGN DRAWINGS AND SPECIFICATIONS

General

Structural design drawings and specifications must clearly outline the scope of work and incorporate all necessary elements as mandated by the Specification, the AISC Code of Standard Practice for Steel Buildings and Bridges, relevant building codes, and any additional applicable requirements.

(b) Identification of the members and connections that are part of the SFRS

(c) Locations and dimensions of protected zones

(d) Connection details between concrete floor diaphragms and the structural steel elements of the SFRS (e) Shop drawing and erection drawing requirements not addressed in Section I1

The Code of Standard Practice replaces the term "design drawings" with "design documents" to encompass both paper and electronic models Additionally, "fabrication documents" is used instead of "shop drawings," and "erection documents" replaces "erection drawings." This terminology is intended to avoid any conflict while generalizing the terms used in the standard.

Steel Construction

In addition to the requirements of Section A4.1, structural design drawings and specifications for steel construction shall indicate the following items, as applicable:

(b) Connection material specifications and sizes

(c) Locations of demand critical welds

When detailing gusset plates, it is essential to identify locations that accommodate inelastic rotation Additionally, connection plates must be specified in areas that require Charpy V-notch toughness, as outlined in Section A3.3(b) It is crucial to note the lowest anticipated service temperature of the steel structure, particularly if it is not enclosed and maintained at a minimum temperature of 50°F (10°C) Lastly, the locations where weld backing needs to be removed should also be clearly indicated.

Fillet welds are essential in specific locations where weld backing is allowed to remain, ensuring structural integrity They are also necessary to reinforce groove welds and enhance connection geometry for improved performance Additionally, it is crucial to identify locations where weld tabs must be removed to maintain the quality and aesthetics of the weld.

(k) Splice locations where tapered transitions are required

(l) The shape of weld access holes, if a shape other than those provided for in the

Certain joints or groups of joints necessitate a specific assembly order, welding sequence, welding technique, or other special precautions, which must be submitted to the engineer of record for approval.

Composite Construction

In accordance with Sections A4.1 and A4.2, structural design drawings and specifications for composite construction must clearly indicate the necessary requirements for the steel components of reinforced concrete or composite elements.

Effective bar placement, including cutoffs, lap and mechanical splices, hooks, and mechanical anchorage, is crucial for structural integrity It is essential to consider the requirements for dimensional changes due to temperature fluctuations, creep, and shrinkage Additionally, the precise location, magnitude, and sequencing of any prestressing or post-tensioning techniques must be carefully planned Lastly, the placement of steel headed stud anchors and welded reinforcing bar anchors plays a significant role in ensuring the strength and durability of the construction.

This chapter addresses the general requirements for the seismic design of steel structures that are applicable to all chapters of the Provisions.

This chapter is organized as follows:

Seismic design categories and risk categories dictate the necessary strength and design requirements, along with height and irregularity limitations, as outlined in the relevant building code.

The design story drift and the limitations on story drift shall be determined as required in the applicable building code.

The required strength outlined in these provisions pertains to the capacity-limited seismic load The capacity-limited horizontal seismic load effect, E cl, must be determined as specified in these provisions, replacing E mh, and applied according to the load combinations established in the relevant building code.

In accordance with the specified provisions, when addressing the required strength related to overstrength seismic loads, the horizontal seismic load effect, E mh, must be calculated using the overstrength factor, Ω o, and applied according to the load combinations outlined in the relevant building code Additionally, it is permissible to utilize the capacity-limited seismic load in scenarios where the required strength pertains to overstrength seismic loads.

User Note: The seismic load effect including overstrength is defined in ASCE/

In ASCE/SEI 7 Section 12.4.3.1, the horizontal seismic load effect, denoted as E mh, is calculated using Equation 12.4-7: E mh = Ω o Q E It is important to note that E mh has an upper limit, as it should not exceed the value of E cl.

Provisions for seismic loads allow for the use of overstrength factors, denoted as Ω o, or capacity-limited seismic load, E cl According to ASCE/SEI 7 Section, when capacity-limited seismic load is necessary, E cl should be used in place of E mh.

12.4.3.2 and use of ASCE/SEI 7 Equation 12.4-7 is not permitted.

GENERAL DESIGN REQUIREMENTS

Required Strength

The required strength of structural members and connections shall be the greater of:

The necessary strength, as identified through structural analysis for the relevant load combinations outlined in the applicable building code and Chapter C, along with the strength requirements specified in Chapters D, E, F, G, and H, must be adhered to for compliance and safety.

Available Strength

The available strength is defined as the design strength, ϕR n, for load and resistance factor design (LRFD) and as the allowable strength, R n /Ω, for allowable strength design (ASD) The determination of available strength for systems, members, and connections must follow the Specification, unless modified by these Provisions.

The seismic force-resisting system (SFRS) must include moment frames, braced frames, or shear wall systems that adhere to the specifications outlined in Chapters E, F, G, and H.

Diaphragms and chords must be engineered to withstand the loads and load combinations specified in the relevant building code Additionally, collectors should be designed to accommodate these load combinations, ensuring compliance with the building code, including considerations for overstrength.

Truss Diaphragms

When utilizing a truss as a diaphragm, it is essential to ensure that all truss members and their connections are designed to withstand forces determined by the load combinations specified in the relevant building code, including considerations for overstrength.

Forces outlined in this section are not required to be applied to the diagonal members of truss diaphragms and their connections, provided these components meet the criteria specified in Sections F2.4a, F2.5a, F2.5b, and F2.6c However, braces configured in K or V shapes, as well as those supporting gravity loads beyond their own weight, do not qualify for this exception.

Chords in truss diaphragms function similarly to columns in vertical special concentrically braced frames and must comply with the requirements for highly ductile members as specified for columns in Section F2.5a.

Truss diaphragms integrated into three-dimensional systems featuring ordinary moment frames or ordinary concentrically braced frames are exempt from the forces outlined in this section This exemption applies as long as the truss diagonal members meet the criteria specified in Sections F1.4b and F1.5, and the connections adhere to the standards set in Section F1.6.

This chapter addresses design related analysis requirements The chapter is organized as follows:

An analysis conforming to the requirements of the applicable building code and the

Specification shall be performed for design of the system.

In designs that utilize elastic analysis, the stiffness characteristics of steel system components must be determined using elastic sections, while for composite systems, the analysis should account for the impact of cracked sections.

Additional analysis shall be performed as specified in Chapters E, F, G and H of these

When nonlinear analysis is used to satisfy the requirements of these Provisions, it shall be performed in accordance with the applicable building code.

ASCE/SEI 7 allows for nonlinear analysis through a response history procedure, incorporating both material and geometric nonlinearities in the analytical model This approach aims to assess anticipated member inelastic deformations and story drifts in response to representative ground motions Additionally, the analysis yields maximum expected internal forces at critical locations, such as column splices, which serve as upper limits for the necessary strength in design.

ANALYSIS

Classification of Sections for Ductility

When required for the systems defined in Chapters E, F, G, H and Section D4, members designated as moderately ductile members or highly ductile members shall comply with this section.

1a Section Requirements for Ductile Members

Structural steel sections for both moderately ductile members and highly ductile members shall have flanges continuously connected to the web or webs.

Encased composite columns shall comply with the requirements of Section D1.4b.1 for moderately ductile members and Section D1.4b.2 for highly ductile members.

Filled composite columns shall comply with the requirements of Section D1.4c for both moderately and highly ductile members.

Concrete sections shall comply with the requirements of ACI 318 Section 18.4 for moderately ductile members and ACI 318 Section 18.6 and 18.7 for highly ductile members.

1b Width-to-Thickness Limitations of Steel and Composite Sections

For members designated as moderately ductile members, the width-to-thickness ratios of compression elements shall not exceed the limiting width-to-thickness ratios, λ md , from Table D1.1.

For members designated as highly ductile members, the width-to-thickness ratios of compression elements shall not exceed the limiting width-to-thickness ratios, λ hd , from Table D1.1.

TABLE D1.1 Limiting Width-to-Thickness Ratios for Compression Elements for Moderately Ductile and Highly Ductile Members

Limiting Width-to-Thickness Ratio

Highly Ductile Members λ md Moderately Ductile Members

Flanges of rolled or built-up I-shaped sections, channels, and tees, as well as the legs of single and double-angle members with separators, play a crucial role in structural integrity Additionally, the outstanding legs of pairs of angles in continuous contact are essential for maintaining stability, adhering to the specification of b/t 0.32 R F E y y.

Flanges of H-pile sections per

HSS used as diagonal braces

Side plates of boxed I-shaped sections and walls of built-up box shapes used as diagonal braces

Flanges of built-up box shapes used as link beams b / t b / t h / t b / t

TABLE D1.1 (continued) Limiting Width-to-Thickness Ratios for Compression Elements for Moderately Ductile and Highly Ductile Members

Webs of rolled or built-up I shaped sections and channels used as diagonal braces h / t w 1.57 R F E y y 1.57 R F E y y

Where used in beams or columns as flanges in uniform compression due to axial, flexure, or combined axial and flexure:

2) Flanges and side plates of boxed I-shaped sections, webs and flanges of built-up box shapes b / t h / t

Where used in beams, columns, or links, as webs in flexure, or combined axial and flexure:

1) Webs of rolled or built-up I-shaped sections or channels [b]

2) Side plates of boxed I-shaped sections

3) Webs of built-up box sections h / t w h / t h / t

Webs of built-up box sections used as EBF links h / t 0.67 R F E y y 1.75 R F E y y

Webs of H-Pile sections h / t w not applicable E

Walls of rectangular filled composite members b / t 1.48 R F E y y 2.37 R F E y y

Walls of round filled composite members D / t 0.085 R F E y y

[a] For tee-shaped compression members, the limiting width-to-thickness ratio for highly ductile members for the stem of the tee shall be E

0.40 R F y y where either of the following conditions are satisfied:

(1) Buckling of the compression member occurs about the plane of the stem.

The axial compression load is transmitted through end connections solely to the outer face of the tee flange, creating an eccentric connection that diminishes the compression stresses at the stem's tip.

[b] For I-shaped beams in SMF systems, where C a is less than or equal to 0.114, the limiting ratio h / t w shall not exceed E

For I-shaped beams in intermediate moment frame (IMF) systems, where C a is less than or equal to 0.114, the limiting width-to-thickness ratio shall not exceed E

[c] The limiting diameter-to-thickness ratio of round HSS members used as beams or columns shall not exceed

E = modulus of elasticity of steel = 29,000 ksi (200 000 MPa)

F y = specified minimum yield stress, ksi (MPa)

P a = required axial strength using ASD load combinations, kips (N)

P u = required axial strength using LRFD load combinations, kips (N)

R y = ratio of the expected yield stress to the specified minimum yield stress ϕ c = resistance factor for compression Ω c = safety factor for compression

Stability Bracing of Beams

In accordance with Chapters E, F, G, and H, stability bracing is essential to prevent lateral-torsional buckling of structural steel or concrete-encased beams under flexural loads This requirement specifically applies to beams classified as moderately ductile or highly ductile members.

Stability bracing is essential not only for intermediate and special moment frame beams as outlined in Chapters E, F, G, and H but also for columns within the special cantilever column system (SCCS) as specified in Section E6.

The bracing of moderately ductile steel beams shall satisfy the following requirements:

(a) Both flanges of beams shall be laterally braced or the beam cross section shall be braced with point torsional bracing.

Beam bracing must adhere to the guidelines outlined in Appendix 6 of the Specification, which addresses the lateral and torsional bracing of beams In this context, the value of C d is set at 1.0, and it is essential to ensure that the member achieves the necessary flexural strength.

R y = ratio of the expected yield stress to the specified minimum yield stress

Z = plastic section modulus about the axis of bending, in 3 (mm 3 ) α s = LRFD-ASD force level adjustment factor = 1.0 for LRFD and 1.5 for ASD

(c) Beam bracing shall have a maximum spacing of

L b 0.19r E R F y y y (D1-2) where r y = radius of gyration about y-axis, in (mm)

The bracing of moderately ductile concrete-encased composite beams shall satisfy the following requirements:

(a) Both flanges of members shall be laterally braced or the beam cross section shall be braced with point torsional bracing.

(b) Lateral bracing shall meet the requirements of Appendix 6 of the Specifica- tion for lateral or torsional bracing of beams, where M r = M p,exp of the beam as specified in Section G2.6d, and C d = 1.0.

(c) Member bracing shall have a maximum spacing of

L b = 0.19r y E / ( R y F y ) (D1-3) using the material properties of the steel section and r y in the plane of buckling calculated based on the elastic transformed section.

In addition to the requirements of Sections D1.2a.1(a) and (b), and D1.2a.2(a) and

(b), the bracing of highly ductile beam members shall have a maximum spacing of

For concrete-encased composite beams, the steel section's material properties are essential, and the calculation of the radius of gyration (r y) in the buckling plane must utilize the elastic transformed section The formula L b = 0.095r y E / (R y F y) is applicable in this context.

2c Special Bracing at Plastic Hinge Locations

Special bracing shall be located adjacent to expected plastic hinge locations where required by Chapters E, F, G or H.

For structural steel beams, such bracing shall satisfy the following requirements:

(a) Both flanges of beams shall be laterally braced or the member cross section shall be braced with point torsional bracing.

(b) The required strength of lateral bracing of each flange provided adjacent to plastic hinges shall be:

P r 0.06R F Z y y s o h (D1-4) where h o = distance between flange centroids, in (mm)

The required strength of torsional bracing provided adjacent to plastic hinges shall be:

The necessary bracing stiffness must meet the criteria outlined in Appendix 6 of the Specification for lateral or torsional bracing of beams with a C d value of 1.0 Additionally, the required flexural strength of the beam should be determined accordingly.

For concrete-encased composite beams, such bracing shall satisfy the following requirements:

(a) Both flanges of beams shall be laterally braced or the beam cross section shall be braced with point torsional bracing.

(b) The required strength of lateral bracing provided adjacent to plastic hinges shall be

P u 0.06M p exp , h o (D1-7) of the beam, where

M p,exp = expected flexural strength of the steel, concrete-encased or composite beam, kip-in (N-mm), determined in accordance with Section G2.6d.

The required strength for torsional bracing provided adjacent to plastic hinges shall be M u = 0.06M p,exp of the beam.

The required bracing stiffness must meet the criteria outlined in Appendix 6 of the Specification for the lateral or torsional bracing of beams This is applicable when the ratio of moment resistance (M r) to the ultimate moment (M u) equals the expected plastic moment (M p,exp) of the beam, as determined by Section G2.6d, with a constant C d set at 1.0.

Protected Zones

Discontinuities arising from fabrication, erection procedures, or other attachments are not allowed in areas designated as protected zones for members or connection elements, as outlined in Section I2.1 of these Provisions and ANSI standards.

Welded steel headed stud anchors and similar connections are allowed in protected zones if specified in ANSI/AISC 358 They may also be accepted through a connection prequalification per Section K1 or through qualification testing as outlined in Sections K2 and K3.

Columns

Columns in moment frames, braced frames and shear walls shall satisfy the requirements of this section.

The required strength of columns in the SFRS shall be determined from the greater effect of the following:

(a) The load effect resulting from the analysis requirements for the applicable system per Chapters E, F, G and H.

The compressive axial strength and tensile strength are evaluated using the overstrength seismic load, allowing for the neglect of applied moments in this assessment, except when the moment arises from a load applied to the column between lateral support points.

When assessing the required axial strength for columns shared by intersecting frames, it is essential to account for the potential simultaneous inelastic behavior across all frames, including considerations for overstrength seismic loads or capacity-limited seismic loads The load direction in each frame must be chosen to generate the maximum load effect on the column.

Columns can have their required axial strength limited through a three-dimensional nonlinear analysis that applies ground motion in two orthogonal directions, as outlined in Section C3.

(b) Columns common to intersecting frames that are part of Sections E1, F1, G1,

H1, H4 or combinations thereof need not be designed for these loads.

Encased composite columns must meet the criteria outlined in Specification Chapter I, along with the specific requirements detailed in this section Furthermore, additional stipulations for moderately ductile and highly ductile members are provided in Sections D1.4b.1.

2, shall apply as required by Chapters G and H.

Encased composite columns used as moderately ductile members shall satisfy the following requirements:

(a) The maximum spacing of transverse reinforcement at the top and bottom shall be the least of the following:

(1) One-half the least dimension of the section

The required spacing must be upheld over a vertical distance that is at least equal to the greatest length measured from each joint face, applicable to both sides of any section where flexural yielding is anticipated.

(1) One-sixth the vertical clear height of the column

(c) Tie spacing over the remaining column length shall not exceed twice the spacing defined in Section D1.4b.1(a).

Splices and end bearing details for encased composite columns in composite ordinary SFRS must meet the requirements outlined in the Specification and ACI 318 Section 10.7.5.3 The design should adhere to ACI 318 Sections 18.2.7 and 18.2.8, taking into account any negative behavioral impacts from sudden changes in member stiffness or nominal tensile strength It is essential to recognize transitions to reinforced concrete sections without embedded structural steel, transitions to bare structural steel sections, and column bases as abrupt changes.

(e) Welded wire fabric shall be prohibited as transverse reinforcement.

Encased composite columns used as highly ductile members shall satisfy Sec- tion D1.4b.1 in addition to the following requirements:

(a) Longitudinal load-carrying reinforcement shall satisfy the requirements of ACI 318 Section 18.7.4.

(b) Transverse reinforcement shall be hoop reinforcement as defined in ACI 318 Chapter 18 and shall satisfy the following requirements:

(1) The minimum area of tie reinforcement, A sh , shall be:

A s = cross-sectional area of the structural steel core, in 2 (mm 2 )

F y = specified minimum yield stress of the structural steel core, ksi (MPa)

F ysr = specified minimum yield stress of the ties, ksi (MPa)

The nominal axial compressive strength (P_n) of a composite column is determined according to specified guidelines and is measured in kips (N) The cross-sectional dimension of the confined core (h_cc) is assessed from the center-to-center distance of the tie reinforcement, measured in inches (mm) The specified compressive strength of concrete (ƒ′_c) is expressed in ksi (MPa), while the spacing of transverse reinforcement (s) is measured along the longitudinal axis of the structural member, also in inches (mm).

Equation D1-8 need not be satisfied if the nominal strength of the concrete-encased structural steel section alone is greater than the load effect from a load combination of 1.0D + 0.5L, where

D = dead load due to the weight of the structural elements and permanent features on the building, kips (N)

L = live load due to occupancy and moveable equipment, kips (N)

(2) The maximum spacing of transverse reinforcement along the length of the column shall be the lesser of six longitudinal load-carrying bar diameters or 6 in (150 mm).

In accordance with Sections D1.4b.1(c), D1.4b.1(d), and D1.4b.1(e), the maximum spacing for transverse reinforcement along a member's length must not exceed one-fourth of the member's smallest dimension or 4 inches (100 mm) Additionally, confining reinforcement should be placed no more than 14 inches (350 mm) apart in the transverse direction.

Encased composite columns in braced frames that require compressive strengths exceeding 0.2P n, excluding overstrength seismic loads, must feature transverse reinforcement throughout the entire element length as outlined in Section D1.4b.2(b)(3) However, this requirement can be waived if the nominal strength of the concrete-encased steel section surpasses the load effect derived from the load combination of 1.0D + 0.5L.

Composite columns that support loads from discontinued stiff members, such as walls or braced frames, must include transverse reinforcement throughout their entire length below the level of discontinuity if the necessary compressive strength exceeds 0.1P n, excluding overstrength seismic loads This transverse reinforcement must extend into the discontinued member sufficiently to ensure full yielding of both the concrete-encased steel section and the longitudinal reinforcement However, this requirement can be waived if the nominal strength of the concrete-encased steel section alone surpasses the load effect from the load combination of 1.0D + 0.5L.

(e) Encased composite columns used in a C-SMF shall satisfy the following requirements:

(1) Transverse reinforcement shall satisfy the requirements in Section D1.4b.2(2) at the top and bottom of the column over the region specified in Section D1.4b.1(b).

(2) The strong-column/weak-beam design requirements in Section G3.4a shall be satisfied Column bases shall be detailed to sustain inelastic flexural hinging.

(3) The required shear strength of the column shall satisfy the requirements of ACI 318 Section 18.7.6.1.1.

When a column ends on a footing or mat foundation, the transverse reinforcement must extend at least 12 inches (300 mm) into the footing or mat If the column terminates on a wall, the transverse reinforcement should extend into the wall sufficiently to ensure full yielding of the concrete-encased shape and longitudinal reinforcement.

This section applies to columns that meet the limitations of Specification Section

Filled composite columns must be designed in accordance with Specification Chapter I, with the exception that their nominal shear strength is determined solely by the structural steel section's effective shear area.

Composite Slab Diaphragms

The design of composite floor and roof slab diaphragms for seismic effects shall meet the following requirements.

Details shall be provided to transfer loads between the diaphragm and boundary members, collector elements, and elements of the horizontal framing system.

The nominal in-plane shear strength of composite diaphragms and concrete slabs on steel deck diaphragms should be considered as the nominal shear strength of the reinforced concrete situated above the top of the steel deck ribs, following the guidelines set forth in ACI 318, with certain exclusions.

Chapter 14 Alternatively, the composite diaphragm nominal shear strength shall be determined by in-plane shear tests of concrete-filled diaphragms.

Built-Up Structural Steel Members

This section addresses connections between components of built-up members where specific requirements are not provided in the system chapters of these Provisions or in ANSI/AISC 358.

Connections between components of built-up members subject to inelastic behavior shall be designed for the expected forces arising from that inelastic behavior.

Connections between components of built-up members where inelastic behavior is not expected shall be designed for the load effect including the overstrength seismic load.

In areas where connections between components of a built structure are necessary within a protected zone, these connections must possess a tensile strength equivalent to R y F y t p / α s of the weaker element throughout the entire length of the protected zone.

Built-up members can be utilized in connections that require testing, provided they are either accepted by ANSI/AISC 358 for a prequalified joint or have been validated through a qualification test.

Connections, joints and fasteners that are part of the SFRS shall comply with Specifi- cation Chapter J, and with the additional requirements of this section.

Splices and bases of columns that are not designated as part of the SFRS shall satisfy the requirements of Sections D2.5a, D2.5c and D2.6.

Where protected zones are designated in connection elements by these Provisions or

ANSI/AISC 358, they shall satisfy the requirements of Sections D1.3 and I2.1.

Bolted Joints

Bolted joints shall satisfy the following requirements:

The shear strength of bolted joints with standard or short-slotted holes, when subjected to perpendicular loads, should be determined following the guidelines for bearing-type joints outlined in Specification Sections J3.6 and J3.10 It is essential to apply the nominal bolt bearing and tearout equations from Section J3.10, especially when the deformation at the bolt hole under service load is a critical design factor.

In cases where the required strength of a connection relies on the anticipated strength of a member or element, it is acceptable to utilize the bolt bearing and tearout equations as outlined in Specification Section J3.10, provided that deformation is not a factor in the design considerations.

(b) Bolts and welds shall not be designed to share force in a joint or the same force component in a connection.

To ensure structural integrity, a member force, like a diagonal brace axial force, must be resisted at the connection using only one type of joint—either bolts or welds Connections that utilize both types, such as when bolts resist forces perpendicular to those resisted by welds, do not effectively share the load For instance, in a moment connection where welded flanges handle flexural forces and a bolted web transmits shear, the forces are not considered to be shared.

Bolt holes in bolted joints must be standard or short-slotted and oriented perpendicular to the applied load, especially where seismic loads are transferred through shear in the bolts However, oversized or short-slotted holes are allowed in connections where seismic loads are transferred through tension rather than shear in the bolts.

(1) For diagonal braces, oversized holes are permitted in one connection ply only when the connection is designed as a slip-critical joint.

Alternative hole types are allowed if specified in ANSI/AISC 358, established through a connection prequalification per Section K1, or determined through qualification testing as outlined in Section K2 or K3.

Diagonal brace connections featuring oversized holes must meet additional limit states, specifically bolt bearing and bolt shear, to ensure the connection's strength as outlined in Sections F1, F2, F3, and F4.

(d) All bolts shall be installed as pretensioned high-strength bolts Faying surfaces shall satisfy the requirements for slip-critical connections in accordance with

Specification Section J3.8 with a faying surface with a Class A slip coefficient or higher.

Exceptions: Connection surfaces are permitted to have coatings with a slip coefficient less than that of a Class A faying surface for the following:

(1) End plate moment connections conforming to the requirements of Section E1, or ANSI/AISC 358

(2) Bolted joints where the seismic load effects are transferred either by tension in bolts or by compression bearing but not by shear in bolts

Welded Joints

Welded joints shall be designed in accordance with Specification Chapter J.

Continuity Plates and Stiffeners

The design of continuity plates and stiffeners in the webs of rolled shapes must accommodate reduced contact lengths with the member flanges and web, as specified by the corner clip sizes outlined in Section I2.4.

Column Splices

For all building columns, including those not designated as part of the SFRS, column splices shall be located 4 ft (1.2 m) or more away from the beam-to-column flange connections.

(a) When the column clear height between beam-to-column flange connections is less than 8 ft (2.4 m), splices shall be at half the clear height

Column splices featuring webs and flanges connected by complete-joint-penetration groove welds can be positioned nearer to beam-to-column flange connections, provided they maintain a minimum distance equal to the depth of the column.

For optimal safety and accessibility, it is recommended that splices be positioned at least 4 feet (1.2 meters) above the finished floor elevation This height allows for the installation of perimeter safety cables before the erection of the next tier.

(1) The required strength of column splices in the SFRS shall be the greater of:

(a) The required strength of the columns, including that determined from Chapters E, F, G and H and Section D1.4a; or,

(b) The required strength determined using the overstrength seismic load.

Welded column splices subjected to a calculated net tensile load effect, based on the overstrength seismic load, must meet specific requirements to ensure structural integrity and safety.

(a) The available strength of partial-joint-penetration (PJP) groove welded joints, if used, shall be at least equal to 200% of the required strength

Exception: Partial-joint-penetration (PJP) groove welds are excluded from this requirement if the Exceptions in Sections E2.6g, E3.6g or E4.6c are invoked.

(b) The available strength for each flange splice shall be at least equal to 0.5R y F y b f t f / α s , where

F y = specified minimum yield stress, ksi (MPa)

R y = ratio of expected yield stress to the specified minimum yield stress,

F y b f = width of flange, in (mm) of the smaller column connected t f = thickness of flange, in (mm) of the smaller column connected

When butt joints in column splices utilize complete-joint-penetration groove welds, tapered transitions are necessary between flanges of differing thickness or width if the tension stress at any point in the smaller flange surpasses 0.30F y / α s These transitions must comply with the guidelines outlined in AWS D1.8/D1.8M clause 4.2.

For all building columns, including those not part of the Special Moment-Resisting Frame System (SFRS), the required shear strength of column splices must be calculated using the formula M pc / (α s H) In this equation, M pc represents the lesser plastic flexural strength of the column sections for the relevant direction, while H denotes the height of the story The height can be measured as the distance between the centerlines of the floor framing at adjacent levels or the distance between the tops of the floor slabs at those levels.

The required shear strength of splices of columns in the SFRS shall be the greater of the foregoing requirement or the required shear strength determined per Section

Structural steel column splices can be either bolted or welded, or they can be welded to one column and bolted to another It is essential that all splice configurations comply with the specific requirements outlined in Chapters E, F, G, or H.

Splice plates or channels used for making web splices in SFRS columns shall be placed on both sides of the column web.

For welded butt-joint splices made with groove welds, weld tabs shall be removed in accordance with AWS D1.8/D1.8M clause 6.16 Steel backing of groove welds need not be removed.

5e Splices in Encased Composite Columns

For encased composite columns, column splices shall conform to Section D1.4b and

Column Bases

The required strength of column bases, including those that are not designated as part of the SFRS, shall be determined in accordance with this section.

The available strength of steel elements at the column base, including base plates, anchor rods, stiffening plates, and shear lug elements shall be in accordance with the

When columns are welded to base plates using groove welds, it is essential to remove weld tabs and weld backing, except for specific cases Weld backing that is attached to the inside of flanges and on the web of I-shaped sections can remain if it is secured to the column base plate with a continuous 3/8-inch (8 mm) fillet weld However, fillet welds connecting the backing to the inside of column flanges are not allowed Additionally, weld backing on the inside of hollow structural sections (HSS) and box-section columns does not need to be removed.

The strength of concrete elements and reinforcing steel at the column base must comply with ACI 318 standards When designing anchor rods, it is essential to ensure that ductility is achieved through deformations in the rods and their anchorage within reinforced concrete, adhering to the requirements set forth by ACI 318.

Chapter 17 Alternatively, when the ductility demand is provided for elsewhere, the anchor rods and anchorage into reinforced concrete are permitted to be designed for the maximum loads resulting from the deformations occurring elsewhere, including the effects of material overstrength and strain hardening.

When designing anchor embedments with concrete reinforcing steel, it's crucial to account for potential anchor failure modes Ensure that reinforcement is effectively developed on both sides of the anticipated failure surface, as outlined in ACI 318 Chapter 17 and its Commentary.

The axial strength required for column bases within the Seismic Force Resisting System (SFRS), including their connection to the foundation, must equal the total vertical components of the necessary connection strengths of the steel elements linked to the column base This strength must also meet or exceed the higher of specified minimum values.

(a) The column axial load calculated using the overstrength seismic load

(b) The required axial strength for column splices, as prescribed in Section D2.5

The vertical components of a structure encompass the axial load from columns and the vertical component of the axial load from diagonal members that frame into the column base For detailed guidance, refer to Section D2.5, which cites Section D1.4a and relevant chapters.

E, F, G and H Where diagonal braces frame to both sides of a column, the effects of compression brace buckling should be considered in the summation of vertical components See Section F2.3.

The shear strength needed for column bases, including those not classified as part of the Seismic Force Resisting System (SFRS), along with their connections to the foundations, must equal the total of the horizontal components of the required connection strengths for the steel elements attached to the column base.

(a) For diagonal braces, the horizontal component shall be determined from the required strength of diagonal brace connections for the SFRS.

(b) For columns, the horizontal component shall be equal to the lesser of the following:

(2) The shear calculated using the overstrength seismic load.

(c) The summation of the required strengths of the horizontal components shall not be less than 07F y Z / (α s H) of the column.

(a) Single story columns with simple connections at both ends need not comply with Sections D2.6b(b) or D2.6b(c).

(b) Columns that are part of the systems defined in Sections E1, F1, G1, H1, H4 or combinations thereof need not comply with Section D2.6b(c).

The minimum shear strength required, as outlined in Section D2.6b(c), should not surpass the maximum load effect that the column can transfer to the foundation This determination can be made through a nonlinear analysis as specified in Section C3, or by conducting an analysis that accounts for inelastic behavior leading to a story drift of 0.025H at either the first or second story, but not simultaneously for both levels.

Horizontal components in structural design include shear loads from columns and the horizontal axial loads from diagonal members connecting to the column base For columns not included in the Seismic Force Resisting System (SFRS), horizontal forces are generally assessed based on the criteria outlined in this section, but they typically do not take precedence over those calculated in accordance with Section D2.6b(c).

In structures where column bases serve as moment connections to the foundation, the necessary flexural strength of these bases, which are integral to the Special Moment Resisting Frame System (SMRFS), must equal the total required connection strengths of the steel elements linked to the column base.

(a) For diagonal braces, the required flexural strength shall be at least equal to the required flexural strength of diagonal brace connections.

(b) For columns, the required flexural strength shall be at least equal to the lesser of the following:

(2) The moment calculated using the overstrength seismic load, provided that a ductile limit state in either the column base or the foundation controls the design.

User Note: Moments at column to column base connections designed as simple connections may be ignored.

Composite Connections

This section addresses connections in buildings that employ composite steel and concrete systems, focusing on the transfer of seismic loads between structural steel and reinforced concrete elements To ensure safety and effectiveness, the methods for calculating connection strength must adhere to specified requirements If connection strength is not established through analysis or testing, the design models for these connections must meet certain established criteria.

(a) Force shall be transferred between structural steel and reinforced concrete through:

(1) direct bearing from internal bearing mechanisms;

(3) shear friction with the necessary clamping force provided by reinforcement normal to the plane of shear transfer; or

The combination of various mechanisms is allowed only when their stiffness and deformation capacities are compatible Additionally, any potential bond strength between structural steel and reinforced concrete should be disregarded when considering the connection force transfer mechanism.

(b) The nominal bearing and shear-friction strengths shall meet the requirements of

ACI 318 Unless a higher strength is substantiated by cyclic testing, the nominal bearing and shear-friction strengths shall be reduced by 25% for the composite seismic systems described in Sections G3, H2, H3, H5 and H6.

(c) Face bearing plates consisting of stiffeners between the flanges of steel beams shall be provided when beams are embedded in reinforced concrete columns or walls.

The nominal shear strength of concrete-encased steel panel zones in beam-to-column connections is determined by summing the nominal strengths of the structural steel and the confined reinforced concrete shear elements, as outlined in Section E3.6e and ACI 318 Section 18.8.

Reinforcement in reinforced concrete connections must effectively counteract all tensile forces, while transverse reinforcement is necessary to confine the concrete It is essential that all reinforcement is fully developed in tension or compression beyond the point where it is no longer needed to resist forces The development lengths for these reinforcements should adhere to the specifications outlined in ACI 318 Chapter 25, and must also meet the requirements set forth in ACI 318 Section 18.8.5 for the systems detailed in Sections G3, H2, H3, H5, and H6.

(f) Composite connections shall satisfy the following additional requirements:

To effectively transfer horizontal diaphragm forces, the slab reinforcement must be meticulously designed and anchored to withstand in-plane tensile forces at all critical sections This includes connections to collector beams, columns, diagonal braces, and walls.

For connections between structural steel or composite beams and reinforced concrete or encased composite columns, it is essential to include transverse hoop reinforcement in the connection area of the column This requirement aligns with ACI 318 Section 18.8, with specified modifications.

(i) Structural steel sections framing into the connections are considered to provide confinement over a width equal to that of face bearing plates welded to the beams between the flanges.

Lap splices for perimeter ties are allowed when they are confined by face bearing plates or other methods that protect the concrete cover from spalling, as outlined in Sections G1, G2, H1, and H4.

To ensure structural integrity in reinforced concrete and composite columns, it is crucial to carefully detail the longitudinal bar sizes and layout This design minimizes slippage of the bars at the beam-to-column connection, addressing the significant force transfer that occurs due to variations in column moments along the height of the connection.

User Note: The commentary provides guidance for determining panel-zone shear strength.

Steel Anchors

In sections G2, G3, G4, H2, H3, H5, and H6, the shear and tensile strength of steel headed stud anchors or welded reinforcing bar anchors incorporated into the intermediate or special seismic force-resisting system (SFRS) must be reduced by 25% from their specified strengths.

Specification Chapter I The diameter of steel headed stud anchors shall be limited to w in (19 mm).

User Note: The 25% reduction is not necessary for gravity and collector components in structures with intermediate or special seismic force-resisting systems designed for the overstrength seismic load.

D3 DEFORMATION COMPATIBILITY OF NON-SFRS MEMBERS AND

In accordance with the applicable building code, elements not part of the seismic force-resisting system (SFRS) must be designed to accommodate deformation compatibility This design should account for the combined effects of gravity loads and deformations resulting from the calculated design story drift.

According to ASCE/SEI 7, both structural steel and composite members must adhere to specific requirements regarding flexible shear connections, which should accommodate member end rotations as outlined in Specification Section J1.2 Inelastic deformations in connections or members are acceptable as long as they are self-limiting and do not compromise the stability of the member For additional insights, refer to the Commentary.

Design Requirements

Design of H-piles shall comply with the requirements of the Specification regarding design of members subjected to combined loads H-piles located in site classes E or

F as defined by ASCE/SEI 7 shall satisfy the requirements for moderately ductile members of Section D1.1.

Battered H-Piles

When using a combination of battered (sloped) and vertical piles in a pile group, it is essential to design the vertical piles to independently support the total dead and live loads, without relying on the assistance of the battered piles.

Tension

Tension within each pile is conveyed to the pile cap through mechanical methods, including shear keys, reinforcing bars, or studs that are welded to the embedded section of the pile.

Protected Zone

Each pile shall have a designated protected zone, defined as the length equal to the depth of the pile cross-section directly beneath the bottom of the pile cap, in accordance with the requirements outlined in Sections D1.3 and I2.1.

MOMENT-FRAME SYSTEMS

Scope

Ordinary moment frames (OMF) of structural steel shall be designed in conformance with this section.

Basis of Design

OMF designed in accordance with these provisions are expected to provide minimal inelastic deformation capacity in their members and connections.

Analysis

There are no requirements specific to this system.

System Requirements

Members

In OMF, there are no restrictions on the width-to-thickness ratios of members beyond the specified standards Additionally, there are no stability bracing requirements for beams or joints, aside from those outlined in the Specification Furthermore, structural steel beams in OMF can be combined with a reinforced concrete slab to effectively support gravity loads.

There are no designated protected zones for OMF members.

BRACED-FRAME AND SHEAR-WALL SYSTEMS

Ordinary Concentrically Braced Frames above

4 System Requirements 260 4a Lateral Force Distribution 260 4b V- and Inverted V-Braced Frames 260 4c K-Braced Frames 261 4d Tension-Only Frames 261 4e Multi-Tiered Braced Frames 261

5 Members 272 5a Basic Requirements 272 5b Diagonal Braces 273 5c Protected Zones 274

6 Connections 2746a Demand Critical Welds 2746b Beam-to-Column Connections 2756c Brace Connections 2786d Column Splices 282

4 System Requirements 290 4a Link Rotation Angle 290 4b Bracing of Link 292

5 Members 292 5a Basic Requirements 292 5b Links 292 5c Protected Zones 298

6 Connections 298 6a Demand Critical Welds 298 6b Beam-to-Column Connections 298 6c Brace Connections 298 6d Column Splices 299 6e Link-to-Column Connections 299 F4 Buckling-Restrained Braced Frames (BRBF) 301

2 Basis of Design 302 2a Brace Strength 305 2b Adjustment Factors 305

4 System Requirements 306 4a V- and Inverted V-Braced Frames 306 4b K-Braced Frames 307 4d Multi-Tiered Braced Frames 307

5 Members 309 5a Basic Requirements 309 5b Diagonal Braces 310 5c Protected Zones 311

6 Connections 311 6a Demand Critical Welds 311 6b Beam-to-Column Connections 311 6c Diagonal Brace Connections 312 6d Column Splices 312 F5 Special Plate Shear Walls (SPSW) 312

4a Stiffness of Boundary Elements 323 4c Bracing 323 4d Openings in Webs 323

5 Members 323 5a Basic Requirements 323 5b Webs 324 5c HBE 325 5d Protected Zone 326

6 Connections 326 6a Demand Critical Welds 326 6b HBE-to-VBE Connections 326 6c Connections of Webs to Boundary Elements 327 6d Column Splices 327

7 Perforated Webs 327 7a Regular Layout of Circular Perforations 327 7b Reinforced Corner Cut-Out 328

G1 Composite Ordinary Moment Frames (C-OMF) 331

2 Basis of Design 331 G2 Composite Intermediate Moment Frames (C-IMF) 331

4 System Requirements 331 4a Stability Bracing of Beams 331

5 Members 331 5a Basic Requirements 331 5b Beam Flanges 332 5c Protected Zones 332

6 Connections 332 6a Demand Critical Welds 332 6b Beam-to-Column Connections 332 6c Conformance Demonstration 332 6d Required Shear Strength 332 6e Connection Diaphragm Plates 332 6f Column Splices 333 G3 Composite Special Moment Frames (C-SMF) 333

4 System Requirements 3334a Moment Ratio 3334b Stability Bracing of Beams 3344c Stability Bracing at Beam-to-Column Connections 334

5 Members 334 5a Basic Requirements 334 5b Beam Flanges 334 5c Protected Zones 334

6 Connections 335 6a Demand Critical Welds 335 6b Beam-to-Column Connections 335 6c Conformance Demonstration 338 6d Required Shear Strength 338 6e Connection Diaphragm Plates 339 6f Column Splices 339 G4 Composite Partially Restrained Moment Frames (C-PRMF) 339

6 Connections 342 6c Beam-to-Column Connections 342 6d Conformance Demonstration 343

H COMPOSITE BRACED FRAME AND SHEAR WALL SYSTEMS 344

H1 Composite Ordinary Braced Frames (C-OBF) 344

6 Connections 344 H2 Composite Special Concentrically Braced Frames (C-SCBF) 346

6 Connections 347 6a Demand Critical Welds 347 6b Beam-to-Column Connections 347 6d Column Splices 347 H3 Composite Eccentrically Braced Frames (C-EBF) 348

6 Connections 348 6a Beam-to-Column Connections 348 H4 Composite Ordinary Shear Walls (C-OSW) 349

5 Members 353 5b Coupling Beams 353 H5 Composite Special Shear Walls (C-SSW) 355

5 Members 357 5a Ductile Elements 357 5b Boundary Members 357 5c Steel Coupling Beams 358 5d Composite Coupling Beams 359 5e Protected Zones 360

6 Connections 360 H6 Composite Plate Shear Walls—Concrete Encased (C-PSW/CE) 360

3 Analysis 361 3a Webs 361 3b Other Members and Connections 361

4 System Requirements 361 4e Openings in Webs 361

5 Members 361 5b Webs 361 5c Concrete Stiffening Elements 362 5d Boundary Members 362

6 Connections 362 6a Demand Critical Welds 363 6b HBE-to-VBE Connections 363 6c Connections of Steel Plate to Boundary Elements 363 6d Connections of Steel Plate to Reinforced Concrete Panel 364 H7 Composite Plate Shear Walls—Concrete Filled (C-PSW/CF) 364

4 System Requirements 367 4a Steel Web Plate of C-PSW/CF with Boundary Elements 367 4b Steel Plate of C-PSW/CF without Boundary Elements 367 4d Spacing of Tie Bars in C-PSW/CF with or without

Boundary Elements 367 4f Connection between Tie Bars and Steel Plates 368 4h C-PSW/CF and Foundation Connection 368

5 Members 368 5a Flexural Strength 368 5b Shear Strength 371

3 Shop and Erection Drawings for Composite Construction 373 I2 Fabrication and Erection 373

J QUALITY CONTROL AND QUALITY ASSURANCE 376

1 Documents to be Submitted for Steel Construction 377

2 Documents to be Available for Review for Steel Construction 377

3 Documents to be Submitted for Composite Construction 377

4 Documents to be Available for Review for Composite Construction 378 J3 Quality Assurance Agency Documents 378

J4 Inspection and Nondestructive Testing Personnel 378

3 Document (D) 379 J6 Welding Inspection and Nondestructive Testing 379

2 NDT of Welded Joints 380 2a CJP Groove Weld NDT 380 2b Column Splice and Column-to-Base Plate PJP

Groove Weld NDT 3802c Base Metal NDT for Lamellar Tearing and Laminations 3812d Beam Cope and Access Hole NDT 381

2e Reduced Beam Section Repair NDT 381 2f Weld Tab Removal Sites 381 J7 Inspection of High-Strength Bolting 382

K1 Prequalification of Beam-to-Column and

2 General Requirements 384 2a Basis for Prequalification 384 2b Authority for Prequalification 384

6 Prequalification Record 387 K2 Cyclic Tests for Qualification of Beam-to-Column and

3 Essential Test Variables 389 3a Sources of Inelastic Rotation 389 3b Members 390 3f Steel Strength for Steel Members and Connection Elements 392 3i Welded Joints 393

6 Testing Requirements for Material Specimens 394 K3 Cyclic Tests for Qualification of Buckling-Restrained Braces 395

The symbols listed below are to be used in addition to or replacements for those in the AISC

The Specification for Structural Steel Buildings outlines that in cases of symbol duplication between the Provisions and the AISC Specification, the symbol provided in this document takes precedence Additionally, the section or table number in the right-hand column indicates the initial usage of each symbol.

A b Cross-sectional area of a horizontal boundary element, in 2 (mm 2 ) F5.5b

A c Cross-sectional area of a vertical boundary element, in 2 (mm 2 ) F5.5b

A cw Area of concrete between web plates, in 2 (mm 2 ) H7.5b

A f Gross area of flange, in 2 (mm 2 ) E4.4b

A lw Web area of link (excluding flanges), in 2 (mm 2 ) F3.5b

A s Cross-sectional area of the structural steel core, in 2 (mm 2 ) D1.4b

A sc Cross-sectional area of the yielding segment of steel core, in 2 (mm 2 ) F4.5b

A sh Minimum area of tie reinforcement, in 2 (mm 2 ) D1.4b

A sp Horizontal area of stiffened steel plate in composite plate shear wall, in 2 (mm 2 ) H6.3b

A sr Area of transverse reinforcement in coupling beam, in 2 (mm 2 ) H4.5b

A sr Area of longitudinal wall reinforcement provided over the embedment length, L e , in 2 (mm 2 ) H5.5c

A st Horizontal cross-sectional area of the link stiffener, in 2 (mm 2 ) F3.5b

A sw Area of steel web plates, in 2 (mm 2 ) H7.5b

A tb Area of transfer reinforcement required in each of the first and second regions attached to each of the top and bottom flanges, in 2 (mm 2 ) H5.5c

A tw Area of steel beam web, in 2 (mm 2 ) H5.5c

A w Area of steel beam web, in 2 (mm 2 ) H4.5b

C a Ratio of required strength to available axial yield strength Table D1.1

C d Coefficient relating relative brace stiffness and curvature D1.2a

D Dead load due to the weight of the structural elements and permanent features on the building, kips (N) D1.4b

D Outside diameter of round HSS, in (mm) Table D1.1

D Diameter of the holes, in (mm) F5.7a

E Modulus of elasticity of steel = 29,000 ksi (200 000 MPa) Table D1.1

E cl Capacity-limited horizontal seismic load effect B2

E mh Horizontal seismic load effect, including the overstrength factor, kips (N) or kip-in (N-mm) B2

F cr Critical stress, ksi (MPa) F1.6a

F cre Critical stress calculated from Specification Chapter E using expected yield stress, ksi (MPa) F1.6a

F y Specified minimum yield stress, ksi (MPa) As used in the Specification,

Yield stress refers to the minimum yield point for steels with a defined yield point or the specified yield strength for those without one.

F yb Specified minimum yield stress of beam, ksi (MPa) E3.4a

F yc Specified minimum yield stress of column, ksi (MPa) E3.4a

F ysc Specified minimum yield stress of the steel core, or actual yield stress of the steel core as determined from a coupon test, ksi (MPa) F4.5b

F ysr Specified minimum yield stress of the ties, ksi (MPa) D1.4b

F ysr Specified minimum yield stress of transverse reinforcement, ksi (MPa) H4.5b

F ysr Specified minimum yield stress of transfer reinforcement, ksi (MPa) H5.5c

F yw Specified minimum yield stress of web skin plates, ksi (MPa) H7.5b

F u Specified minimum tensile strength, ksi (MPa) A3.2

H Height of story, in (mm) D2.5c

H c Clear height of the column between beam connections, including a structural slab, if present, in (mm) F2.6d

H c Clear column (and web-plate) height between beam flanges, in (mm) F5.7a.3

I Moment of inertia, in 4 (mm 4 ) E4.5c

I b Moment of inertia of a horizontal boundary element taken perpendicular to the plane of the web, in 4 (mm 4 ) F5.4a

I c Moment of inertia of a vertical boundary element taken perpendicular to the plane of the web, in 4 (mm 4 ) F5.4a

I x Moment of inertia about an axis perpendicular to the plane of the

I y Moment of inertia about an axis in the plane of the EBF in 4 (mm 4 ) F3.5b

I y Moment of inertia of the plate about the y-axis, in 4 (mm 4 ) F5.7b

L Live load due to occupancy and moveable equipment, kips (N) D1.4b

L Length of column, in (mm) E3.4c

L Span length of the truss, in (mm) E4.5c

L Length of brace, in (mm) F1.5b

L Distance between vertical boundary element centerlines, in (mm) F5.4a

L b Length between points which are either braced against lateral displacement of compression flange or braced against twist of the cross section, in (mm) D1.2a

L c Effective length = KL, in (mm) F1.5b

L cf Clear length of beam, in (mm) E1.6b

L cf Clear distance between column flanges, in (mm) F5.5b

L e Embedment length of coupling beam, in (mm) H4.5b

L h Distance between beam plastic hinge locations, as defined within the test report or ANSI/AISC 358, in (mm) E2.6d

L s Length of the special segment, in (mm) E4.5c

M a Required flexural strength, using ASD load combinations, kip-in (N-mm) D1.2c

M f Maximum probable moment at the column face, kip-in (N-mm) E3.6f.1

M nc Nominal flexural strength of a chord member of the special segment, kip-in (N-mm) E4.5c

M n,PR Nominal flexural strength of PR connection, kip-in (N-mm) E1.6c

M p Plastic bending moment, kip-in (N-mm) E1.6b

M p Plastic bending moment of a link, kip-in (N-mm) F3.4a

M p Plastic bending moment of the steel, concrete-encased or composite beam, kip-in (N-mm) G2.6b

M p Moment corresponding to plastic stress distribution over the composite cross section, kip-in (N-mm) G4.6c

M pc Plastic bending moment of the column, kip-in (N-mm) D2.5c

M pcc Plastic flexural strength of a composite column, kip-in (N-mm) G2.6f

M p,exp Expected flexural strength, kip-in (N-mm) D1.2c

The maximum probable moment (M pr) at the plastic hinge location is determined following ANSI/AISC 358 standards, or through connection prequalification as outlined in Section K1, or via qualification testing as specified in Section K2, measured in kip-in (N-mm).

M r Required flexural strength, kip-in (N-mm) D1.2a

M u Required flexural strength, using LRFD load combinations, kip-in (N-mm) D1.2c

M uv Additional moment due to shear amplification from the location of the plastic hinge to the column centerline, kip-in (N-mm) G3.4a

M v Additional moment due to shear amplification from the location of the plastic hinge to the column centerline based on LRFD or ASD load combinations, kip-in (N-mm) E3.4a

M y Yield moment corresponding to yielding of the steel plate in flexural tension and first yield in flexural compression H7.5a

M pb * Projection of the expected flexural strength of the beam as defined in

M pc * Projection of the nominal flexural strength of the column as defined in

M pcc * Projection of the nominal flexural strength of the composite or reinforced concrete column as defined in Section G3.4a, kip-in (N-mm) ….G3.4a

M p,exp * Projection of the expected flexural strength of the steel or composite beam as defined in Section G3.4a, kip-in (N-mm) G3.4a

N r Number of horizontal rows of perforations F5.7a

P a Required axial strength using ASD load combinations, kips (N) Table D1.1

P ac Required compressive strength using ASD load combinations, kips (N) E3.4a

P b Axial design strength of wall at balanced condition, kips (N) H5.4

P n Nominal axial compressive strength, kips (N) D1.4b

P nc Nominal axial compressive strength of the chord member at the ends, kips (N) E4.4c

P nc Nominal axial compressive strength of diagonal members of the special segment, kips (N) E4.5c

P nt Nominal axial tensile strength of a diagonal member of the special segment, kips (N) E4.5c

P r Required axial compressive strength, kips (N) E3.4a

P rc Required axial strength, kips (N) E5.4a

P u Required axial strength using LRFD load combinations, kips (N) Table D1.1

P uc Required compressive strength using LRFD load combinations, kips (N) E3.4a

P y Axial yield strength , kips (N) Table D1.1

P ysc Axial yield strength of steel core, kips (N) F4.2a

P ysc-max Maximum specified axial yield strength of steel core, ksi (MPa) F4.4d

P ysc-min Minimum specified axial yield strength of steel core, ksi (MPa) F4.4d

R Radius of the cut-out, in (mm) F5.7b

R c Factor to account for expected strength of concrete = 1.5 H5.5d

R t Ratio of the expected tensile strength to the specified minimum tensile strength F u A3.2

R y Ratio of the expected yield stress to the specified minimum yield stress, F y A3.2

R yr Ratio of the expected yield stress of the transverse reinforcement material to the specified minimum yield stress H5.5d

S diag Shortest center-to-center distance between holes, in (mm) F5.7a

T 1 Tension force resulting from the locally buckled web plates developing plastic hinges on horizontal yield lines along the tie bars and at mid-vertical distance between tie bars H7.4e

T 2 Tension force that develops to prevent splitting of the concrete element on a plane parallel to the steel plate H7.4e

V a Required shear strength using ASD load combinations, kips (N) E1.6b

V comp Limiting expected shear strength of an encased composite coupling beam, kips (N) H4.5b

V n Nominal shear strength of link, kips (N) F3.3

V n Expected shear strength of a steel coupling beam, kips (N) H5.5c

V n,comp Expected shear strength of an encased composite coupling beam, kips (N) H4.5b

V n, connection Nominal shear strength of coupling beam connection to wall pier, kips (N) H4.5b

V ne Expected vertical shear strength of the special segment, kips (N) E4.5c

V p Plastic shear strength of a link, kips (N) F3.4a

V r Required shear strength using LRFD or ASD load combinations, kips (N) F3.5b

V u Required shear strength using LRFD load combinations, kips (N) E1.6b

Y con Distance from the top of the steel beam to the top of concrete slab or encasement, in (mm) G3.5a

Y PNA Maximum distance from the extreme concrete compression fiber to the plastic neutral axis, in (mm) G3.5a

Z Plastic section modulus about the axis of bending, in 3 (mm 3 ) D1.2a

Z c Plastic section modulus of the column about the axis of bending, in 3 (mm 3 ) E3.4a

Z x Plastic section modulus about x-axis, in 3 (mm 3 ) E2.6g a Distance between connectors, in (mm) F2.5b b Width of compression element as defined in Specification

Section B4.1 outlines various dimensions critical for structural elements, including the inside width of box sections, beam flange widths, and wall thicknesses Key parameters such as the overall depth of beams, effective depth of concrete encasements, and nominal bolt diameters are specified in millimeters and inches It details the clear span of coupling beams, the distance between flanges, and the governing radius of gyration, which are essential for ensuring structural integrity Additionally, the section discusses the spacing of transverse reinforcements, thicknesses of various components like steel web plates and gusset plates, and the maximum spacing of tie bars Safety factors for compression and shear strength are also defined, along with deformation quantities for controlling loading in test specimens Understanding these specifications is crucial for engineers and architects to ensure compliance with safety standards and structural performance.

1.5 for ASD D1.2a β Compression strength adjustment factor F4.2a β1 Factor relating depth of equivalent rectangular compressive stress block to neutral axis depth, as defined in ACI 318 H4.5b γ total Total link rotation angle, rad K2.4c θ Story drift angle, rad K2.4b λ hd ,λ md Limiting slenderness parameter for highly and moderately ductile compression elements, respectively D1.1b ϕ Resistance factor B3.2 ϕ c Resistance factor for compression Table D1.1 ϕ v Resistance factor for shear E3.6e ρ Strength adjusted reinforcement ratio H7.5b ω Strain hardening adjustment factor F4.2a

The terms listed below are to be used in addition to those in the AISC Specification for

Structural Steel Buildings Some commonly used terms are repeated here for convenience.

(1) Terms designated with † are common AISI-AISC terms that are coordinated between the two standards developers.

(2) Terms designated with * are usually qualified by the type of load effect, for example, nominal tensile strength, available compressive strength, and design flexural strength.

Adjusted brace strength Strength of a brace in a buckling-restrained braced frame at deformations corresponding to 2.0 times the design story drift.

Adjusted link shear strength Link shear strength including the material overstrength and strain hardening.

Allowable strength*† Nominal strength divided by the safety factor, R n / Ω

Applicable building code† Building code under which the structure is designed.

Allowable Strength Design (ASD) is a method used in structural engineering to proportion components so that their allowable strength meets or exceeds the required strength when subjected to specified ASD load combinations.

ASD load combination† Load combination in the applicable building code intended for allowable strength design (allowable stress design).

Authority having jurisdiction (AHJ) Organization, political subdivision, office or individual charged with the responsibility of administering and enforcing the provisions of this

Available strength*† Design strength or allowable strength, as applicable.

Boundary member Portion along wall or diaphragm edge strengthened with structural steel sections and/or longitudinal steel reinforcement and transverse reinforcement.

Brace test specimen A single buckling-restrained brace element used for laboratory testing intended to model the brace in the prototype.

Braced frame† An essentially vertical truss system that provides resistance to lateral forces and provides stability for the structural system.

Buckling-restrained brace A pre-fabricated, or manufactured, brace element consisting of a steel core and a buckling-restraining system as described in Section F4 and qualified by testing as required in Section K3.

Buckling-restrained braced frame (BRBF) A diagonally braced frame employing buckling- restrained braces and meeting the requirements of Section F4.

Buckling-restraining system System of restraints that limits buckling of the steel core in

The Buckling-Restraining Braced Frame (BRBF) system consists of a casing that encases the steel core, along with structural elements connected to it This innovative system is designed to accommodate transverse expansion and longitudinal contraction of the steel core, allowing for deformations up to 2.0 times the design story drift.

Casing serves as a crucial component that counteracts transverse forces acting on the diagonal brace, effectively preventing buckling of the core structure It is essential for the casing to have a mechanism to transmit these forces to the overall buckling-restraining system Notably, the casing exerts minimal to no resistance against forces along the axis of the diagonal brace.

The capacity-limited horizontal seismic load effect, E cl, is established following the specified provisions and is used in place of E mh This load effect is then applied according to the load combinations outlined in the relevant building code.

Collector Also known as drag strut; member that serves to transfer loads between diaphragms and the members of the vertical force-resisting elements of the seismic force-resisting system.

Column base Assemblage of structural shapes, plates, connectors, bolts and rods at the base of a column used to transmit forces between the steel superstructure and the foundation.

Complete loading cycle A cycle of rotation taken from zero force to zero force, including one positive and one negative peak.

Composite beam Structural steel beam in contact with and acting compositely with a reinforced concrete slab designed to act compositely for seismic forces.

Composite brace Concrete-encased structural steel section (rolled or built-up) or concrete- filled steel section used as a diagonal brace.

Composite column Concrete-encased structural steel section (rolled or built-up) or concrete- filled steel section used as a column.

Composite eccentrically braced frame (C-EBF) Composite braced frame meeting the requirements of Section H3.

Composite intermediate moment frame (C-IMF) Composite moment frame meeting the requirements of Section G2.

Composite ordinary braced frame (C-OBF) Composite braced frame meeting the requirements of Section H1.

Composite ordinary moment frame (C-OMF) Composite moment frame meeting the requirements of Section G1.

Composite ordinary shear wall (C-OSW) Composite shear wall meeting the requirements of Section H4.

Composite partially restrained moment frame (C-PRMF) Composite moment frame meeting the requirements of Section G4.

The composite plate shear wall with concrete encasement (C-PSW/CE) features a steel plate that is reinforced with concrete on one or both sides This design enhances out-of-plane stiffness, effectively preventing buckling of the steel plate while complying with the specifications outlined in Section H6.

The composite plate shear wall (C-PSW/CF) is a structural system featuring two planar steel web plates filled with concrete, which may include boundary elements This design complies with the specifications outlined in Section H7, ensuring enhanced structural integrity and performance.

Composite shear wall Steel plate wall panel composite with reinforced concrete wall panel or reinforced concrete wall that has steel or concrete-encased structural steel sections as boundary members.

A composite slab is a reinforced concrete slab that is supported by and bonded to a formed steel deck This design functions as a diaphragm, effectively transferring loads to and between the components of the seismic force-resisting system.

Composite special concentrically braced frame (C-SCBF) Composite braced frame meeting the requirements of Section H2.

Composite special moment frame (C-SMF) Composite moment frame meeting the requirements of Section G3.

Composite special shear wall (C-SSW) Composite shear wall meeting the requirements of

Concrete-encased shapes Structural steel sections encased in concrete.

Continuity plates Column stiffeners at the top and bottom of the panel zone; also known as transverse stiffeners.

Coupling beam Structural steel or composite beam connecting adjacent reinforced concrete wall elements so that they act together to resist lateral loads.

Demand critical weld Weld so designated by these Provisions.

Design earthquake ground motion The ground motion represented by the design response spectrum as specified in the applicable building code.

Design story drift Calculated story drift, including the effect of expected inelastic action, due to design level earthquake forces as determined by the applicable building code.

Design strength*† Resistance factor multiplied by the nominal strength, ϕR n

Diagonal brace Inclined structural member carrying primarily axial force in a braced frame

Ductile limit states encompass the yielding of members and connections, deformation at bolt holes, and the buckling of members that meet the seismic compactness criteria outlined in Table D1.1 However, the rupture of a member or connection, as well as the buckling of a connection element, is not classified as a ductile limit state.

Eccentrically braced frame (EBF) Diagonally braced frame meeting the requirements of

Section F3 that has at least one end of each diagonal brace connected to a beam with a defined eccentricity from another beam-to-brace connection or a beam-to-column connection.

Encased composite beam Composite beam completely enclosed in reinforced concrete.

Encased composite column Structural steel column completely encased in reinforced concrete.

Engineer of record (EOR) Licensed professional responsible for sealing the contract documents.

Exempted column Column not meeting the requirements of Equation E3-1 for SMF.

Expected tensile strength* Tensile strength of a member, equal to the specified minimum tensile strength, F u , multiplied by R t

Expected yield strength Yield strength in tension of a member, equal to the expected yield stress multiplied by A g

Expected yield stress Yield stress of the material, equal to the specified minimum yield stress, F y , multiplied by R y

Face bearing plates are essential components in construction, designed to enhance the stability of structural steel beams embedded in reinforced concrete walls or columns These plates are strategically positioned at the face of the concrete, ensuring effective load transfer and providing confinement to the surrounding material By facilitating direct bearing, face bearing plates play a crucial role in maintaining the structural integrity of concrete structures.

Filled composite column HSS filled with structural concrete.

Fully composite beam Composite beam that has a sufficient number of steel headed stud anchors to develop the nominal plastic flexural strength of the composite section.

Highly ductile member A member that meets the requirements for highly ductile members in Section D1.

Horizontal boundary element (HBE) A beam with a connection to one or more web plates in an SPSW.

Intermediate boundary element (IBE) A member, other than a beam or column, that provides resistance to web plate tension adjacent to an opening in an SPSW.

Intermediate moment frame (IMF) Moment-frame system that meets the requirements of

Perforated Webs

7a Regular Layout of Circular Perforations

A perforated plate that meets the specified criteria can be utilized as the web of a Steel Plate Shear Wall (SPSW) The perforated webs must feature a consistent pattern of uniformly sized holes, evenly distributed across the entire web-plate area, arranged in such a way that the holes align diagonally at a uniform angle to the vertical It is essential to include at least four horizontal and four vertical lines of holes, with the edges of the openings maintaining a surface roughness of 500 μ-in (13 microns) or less.

The panel design shear strength, ϕV n (LRFD), and the allowable shear strength,

V n / Ω (ASD), in accordance with the limit state of shear yielding, shall be determined as follows for perforated webs with holes that align diagonally at 45° from the horizontal:

0.42 1 0.7S n y w cf diag (F5-3) ϕ = 0.90 (LRFD) Ω = 1.67 (ASD) where

D = diameter of the holes, in (mm)

S diag = shortest center-to-center distance between the holes measured on the 45° diagonal, in (mm)

The spacing, S diag , shall be at least 1.67D.

The distance between the first holes and web connections to the HBE and VBE shall be at least D, but shall not exceed D + 0.7S diag

The stiffness of such regularly perforated infill plates shall be calculated using an effective web-plate thickness, t eff , given by:

1 4 1 sin eff diag diag r c w (F5-4) where

H c = clear column (and web-plate) height between beam flanges, in (mm)

N r = number of horizontal rows of perforations t w = web-plate thickness, in (mm) α = angle of the shortest center-to-center lines in the opening array to vertical, degrees

Perforating webs as outlined in Section F5.7a leads to web yielding occurring parallel to the alignment of the holes Consequently, in the scenario described by Section F5.7a, the angle α is defined as equal to.

The effective expected tension for analysis is R y F y (1 − 0.7D / S diag ).

Quarter-circular cut-outs are allowed at the corners of webs, provided they are reinforced with an arching plate that aligns with the edges of the cut-outs These plates must be engineered to ensure the solid web achieves its full strength and retains its resistance during deformations associated with the design story drift.

The arching plate shall have the available strength to resist the axial tension force, P r , resulting from web-plate tension in the absence of other forces:

F y = specified minimum yield stress of the web plate, in 2 (mm 2 )

R = radius of the cut-out, in (mm)

R y = ratio of the expected yield stress to the specified minimum yield stress,

HBE and VBE shall be designed to resist the axial tension forces acting at the end of the arching reinforcement.

2 Design for Combined Axial and Flexural Forces

The arching plate must possess sufficient strength to withstand the combined impacts of axial force (P r) and moment (M r) in the web's plane, which arise from connection deformation when other forces are not present.

E = modulus of elasticity, ksi (MPa)

H = height of story, in (mm)

The moment of inertia (I y) of the plate about the y-axis is measured in inches to the fourth power (in.⁴ or mm⁴) The design story drift (Δ) is also measured in inches (mm) It is essential that the horizontal beam elements (HBE) and vertical beam elements (VBE) are engineered to withstand the combined axial and flexural strengths required at the ends of the arching reinforcement.

This chapter provides the basis of design, the requirements for analysis, and the requirements for the system, members and connections for composite moment-frame systems.

The chapter is organized as follows:

G1 Composite Ordinary Moment Frames (C-OMF)

G2 Composite Intermediate Moment Frames (C-IMF)

G3 Composite Special Moment Frames (C-SMF)

G4 Composite Partially Restrained Moment Frames (C-PRMF)

User Note: The requirements of this chapter are in addition to those required by the

Specification and the applicable building code.

G1 COMPOSITE ORDINARY MOMENT FRAMES (C-OMF)

Composite ordinary moment frames (C-OMF) shall be designed in conformance with this section This section is applicable to moment frames with fully restrained

(FR) connections that consist of either composite or reinforced concrete columns and structural steel, concrete-encased composite, or composite beams.

C-OMF designed in accordance with these provisions are expected to provide minimal inelastic deformation capacity in their members and connections.

The requirements of Sections A1, A2, A3.5, A4, B1, B2, B3, B4, D2.7, and Chapter

C apply to C-OMF All other requirements in Chapters A, B, D, I, J and K are not applicable to C-OMF.

User Note: Composite ordinary moment frames, comparable to reinforced concrete ordinary moment frames, are only permitted in seismic design categories

Steel ordinary moment frames are allowed in higher seismic design categories, while structures rated B or below in ASCE/SEI 7 have different design requirements that focus on minimal ductility in members and connections.

There are no additional requirements for steel or composite members beyond those in the Specification Reinforced concrete columns shall meet the requirements of ACI

There are no designated protected zones.

Connections shall be fully restrained (FR) and shall satisfy the requirements of Sec- tion D2.7.

G2 COMPOSITE INTERMEDIATE MOMENT FRAMES (C-IMF)

Composite intermediate moment frames (C-IMF) shall be designed in conformance with this section This section is applicable to moment frames with fully restrained

(FR) connections that consist of composite or reinforced concrete columns and structural steel, concrete-encased composite, or composite beams.

C-IMF designed in accordance with these provisions are expected to provide limited inelastic deformation capacity through flexural yielding of the C-IMF beams and columns, and shear yielding of the column panel zones Design of connections of beams to columns, including panel zones, continuity plates and diaphragms shall provide the performance required by Section G2.6b and demonstrate this conformance as required by Section G2.6c.

Composite intermediate moment frames, similar to reinforced concrete intermediate moment frames, are allowed only in seismic design categories C or lower according to ASCE/SEI 7 In contrast, steel intermediate moment frames can be utilized in higher seismic design categories The design specifications focus on ensuring limited ductility in both the members and connections.

Beams shall be braced to satisfy the requirements for moderately ductile members in

Beam braces should be strategically positioned near concentrated forces, changes in cross-section, and other areas identified by analysis where plastic hinges are likely to develop during the inelastic deformations of the C-IMF, unless testing suggests otherwise.

The required strength and stiffness of stability bracing provided adjacent to plastic hinges shall be in accordance with Section D1.2c.

Steel and composite members shall satisfy the requirements of Section D1.1 for moderately ductile members.

In plastic hinge regions, sudden alterations to the beam flange area are not allowed Modifications such as drilling holes in the flange or reducing the width of the beam flange are prohibited unless testing or qualification proves that the modified design can effectively create stable plastic hinges to handle the necessary story drift angle.

The region at each end of the beam subject to inelastic straining shall be designated as a protected zone and shall satisfy the requirements of Section D1.3.

The plastic hinge zones at the ends of C-IMF beams are designated as protected zones, which typically extend from the composite column face to half the beam depth beyond the plastic hinge point.

Connections shall be fully restrained (FR) and shall satisfy the requirements of Sec- tion D2 and this section.

Beam-to-composite column connections used in the SFRS shall satisfy the following requirements:

(a) The connection shall be capable of accommodating a story drift angle of at least

The flexural resistance measured at the column face must be a minimum of 0.80M p of the connected beam when subjected to a story drift angle of 0.02 rad Here, M p refers to the plastic bending moment of steel, concrete-encased, or composite beams, and must comply with the standards outlined in Specification Chapter I.

Beam-to-column connections used in the SFRS shall satisfy the requirements of Sec- tion G2.6b by one of the following:

(a) Use of C-IMF connections designed in accordance with ANSI/AISC 358.

(b) Use of a connection prequalified for C-IMF in accordance with Section K1.

(c) Results of at least two qualifying cyclic test results conducted in accordance with Section K2 The tests are permitted to be based on one of the following:

(1) Tests reported in the research literature or documented tests performed for other projects that represent the project conditions, within the limits specified in Section K2.

(2) Tests that are conducted specifically for the project and are representative of project member sizes, material strengths, connection configurations, and matching connection processes, within the limits specified in Section K2.

(d) Calculations that are substantiated by mechanistic models and component limit state design criteria consistent with these provisions.

The required shear strength of the connection shall be determined using the capacity- limited seismic load effect The capacity-limited horizontal seismic load effect, E cl , shall be taken as:

M p,exp = expected flexural strength of the steel, concrete-encased or composite beam, kip-in (N-mm)

L h = distance between beam plastic hinge locations, in (mm)

To calculate the experimental plastic moment (M p,exp) for a concrete-encased or composite beam, utilize either the plastic stress distribution method or the strain compatibility method It is essential to apply the appropriate R y and R c factors for various elements of the cross-section while ensuring section force equilibrium and determining the flexural strength.

User Note: For steel beams, M p,exp in Equation G2-1 may be taken as R y M p of the beam.

9.1-96 COMPOSITE SPECIAL MOMENT FRAMES (C-SMF) [Sect G3.

Connection diaphragm plates are permitted for filled composite columns both exter- nal to the column and internal to the column.

Where diaphragm plates are used, the thickness of the plates shall be at least the thickness of the beam flange.

Diaphragm plates must be welded around the entire perimeter of the column using either complete-joint-penetration (CJP) groove welds or two-sided fillet welds The strength of these weld joints should meet or exceed the strength of the contact area between the plate and the column sides.

Internal diaphragms shall have circular openings sufficient for placing the concrete.

In addition to the requirements of Section D2.5, column splices shall comply with the requirements of this section Where welds are used to make the splice, they shall be

CJP groove welds When column splices are not made with groove welds, they shall have a required flexural strength that is at least equal to the plastic flexural strength,

M pcc , of the smaller composite column The required shear strength of column web splices shall be at least equal to ∑M pcc / H, where

H = height of story, in (mm)

∑M pcc = sum of the plastic flexural strengths at the top and bottom ends of the composite column, kip-in (N-mm)

For composite columns, the plastic flexural strength shall satisfy the requirements of

Specification Chapter I including the required axial strength, P rc

G3 COMPOSITE SPECIAL MOMENT FRAMES (C-SMF)

Composite special moment frames (C-SMF) must be designed according to the specified guidelines This section applies to moment frames featuring fully restrained (FR) connections, which can include either composite or reinforced concrete columns, along with structural steel or concrete-encased composite beams.

COMPOSITE BRACED-FRAME AND SHEAR-WALL SYSTEMS

QUALITY CONTROL AND QUALITY ASSURANCE

Documents to be Submitted for Steel Construction

In accordance with Specification Section N3.1, the following documents must be submitted for review by the Engineer of Record (EOR) or their designated representative before the fabrication or erection of the relevant work commences.

(b) Copies of the manufacturer’s typical certificate of conformance for all elec- trodes, fluxes and shielding gasses to be used

For critical welds, it is essential to obtain the manufacturer's certifications confirming that the filler metal meets the required supplemental notch toughness standards If the filler metal manufacturer does not provide these certifications, the fabricator or erector must conduct the necessary testing and supply the relevant test reports.

When selecting filler metals for shielded metal arc welding (SMAW), flux cored arc welding (FCAW), and gas metal arc welding (GMAW), it is essential to refer to the manufacturer's product data sheets or catalog data These resources provide critical information on the specifications and performance characteristics of composite (cored) filler metals, ensuring optimal welding results.

The article emphasizes the importance of adhering to a specific assembly order, welding sequence, and welding techniques for joints or groups of joints These details must be submitted to the engineer of record, especially when special precautions are required.

Documents to be Available for Review for Steel Construction

The fabricator and erector must provide any additional documents required by the Engineer of Record (EOR) in the contract for review before fabrication or erection begins.

The fabricator and erector shall retain their document(s) for at least one year after substantial completion of construction.

Documents to be Available for Review for

J4 Inspection and Nondestructive Testing Personnel 378

3 Document (D) 379 J6 Welding Inspection and Nondestructive Testing 379

2 NDT of Welded Joints 380 2a CJP Groove Weld NDT 380 2b Column Splice and Column-to-Base Plate PJP

Groove Weld NDT 3802c Base Metal NDT for Lamellar Tearing and Laminations 3812d Beam Cope and Access Hole NDT 381

2e Reduced Beam Section Repair NDT 381 2f Weld Tab Removal Sites 381 J7 Inspection of High-Strength Bolting 382

The Specification for Structural Steel Buildings outlines that in cases of symbol duplication between its provisions and the AISC Specification, the symbols defined in this document take precedence Additionally, the section or table number indicated in the right-hand column denotes the initial usage of each symbol.

Yield stress refers to the minimum yield point for steels with a defined yield point or the specified yield strength for those without one Understanding yield stress is crucial for material selection and structural integrity in engineering applications.

The maximum probable moment (M pr) at the plastic hinge location is defined according to ANSI/AISC 358 standards, or through a connection prequalification per Section K1, or via qualification testing outlined in Section K2, measured in kip-in (N-mm).

This article outlines various specifications and dimensions related to structural components, including the inside width of box sections, beam flange widths, wall thicknesses, and concrete encasement measurements, all provided in inches and millimeters Key parameters such as the overall depth of beams, bolt diameters, effective depths of encasements, and distances between centroids are detailed The document also specifies the governing radius of gyration, spacing of transverse reinforcement, and thicknesses of elements and plates Additionally, it highlights important safety factors, angles of diagonal members, and deformation quantities critical for design and testing Compliance with these measurements ensures structural integrity and safety in construction projects.

Allowable Strength Design (ASD) is a method used to proportion structural components, ensuring that their allowable strength meets or surpasses the required strength when subjected to ASD load combinations.

The Buckling-Restraining Braced Frame (BRBF) system comprises a casing that encases the steel core and structural elements connected to it This innovative system is designed to accommodate the transverse expansion and longitudinal contraction of the steel core, allowing for deformations up to 2.0 times the design story drift.

Casing is a crucial component that provides resistance against transverse forces acting on the diagonal brace, effectively preventing core buckling It plays a vital role in transmitting these forces to the overall buckling-restraining system, although it exerts minimal or no resistance along the axis of the diagonal brace.

The capacity-limited horizontal seismic load effect, denoted as E cl, is calculated according to established provisions and replaces E mh This load effect is then applied in accordance with the load combinations specified in the relevant building code.

A composite plate shear wall (C-PSW/CE) features a steel plate encased in reinforced concrete on one or both sides This design enhances out-of-plane stiffness, effectively preventing buckling of the steel plate while adhering to the specifications outlined in Section H6.

The Composite Plate Shear Wall with Concrete Fill (C-PSW/CF) is a structural element that features two steel web plates with concrete filling in between This design may include boundary elements and adheres to the specifications outlined in Section H7.

A composite slab is a reinforced concrete structure that is supported by and bonded to a formed steel deck This design functions as a diaphragm, effectively transferring loads to and between the components of the seismic force-resisting system.

The ductile limit state encompasses yielding of members and connections, bearing deformation at bolt holes, and buckling of members that meet the seismic compactness criteria outlined in Table D1.1 However, it is important to note that the rupture of a member or connection, as well as the buckling of a connection element, does not qualify as a ductile limit state.

Face bearing plates are essential components that enhance the structural integrity of reinforced concrete walls and columns These plates are affixed to stiffeners on structural steel beams, ensuring effective load transfer through direct bearing Positioned at the face of the concrete, they provide crucial confinement, contributing to the overall strength and stability of the construction.

The inverted-V-braced frame is a structural design that enhances stability, similar to the V-braced frame The k-area refers to a specific region of the web, extending from the tangent point of the web and flange-web fillet, identified by the AISC “k” dimension, and reaches a distance of 12 inches (38 mm) into the web beyond this k dimension.

K-braced frame A braced-frame configuration in which two or more braces connect to a column at a point other than a beam-to-column or strut-to-column connection.

Observe (O)

The inspector shall observe these functions on a random, daily basis Operations need not be delayed pending observations.

Perform (P)

These inspections shall be performed prior to the final acceptance of the item.

Coordinated Inspection

The Specification for Structural Steel Buildings outlines that in cases of symbol duplication between its provisions and the AISC Specification, the symbols defined in this document take priority Additionally, the corresponding section or table number in the right-hand column indicates the initial usage of each symbol.

Yield stress refers to the minimum specified yield point in steels that possess a yield point, or the specified yield strength in steels that lack a yield point.

The maximum probable moment (M pr) at the plastic hinge location is established following the ANSI/AISC 358 guidelines or through connection prequalification as outlined in Section K1, or via qualification testing as per Section K2, measured in kip-in (N-mm).

Section B4.1 outlines various dimensions and specifications relevant to structural components, including the inside width of box sections and beam flanges, as well as the thickness of wall piers and concrete encasements Key measurements such as the overall depth of beams, nominal bolt diameters, and effective depths of concrete encasements are detailed, along with the clear spans of coupling beams and distances between flanges The document also specifies the governing radius of gyration, minimum radius for individual components, and the thicknesses of various elements, including steel web plates and gusset plates Additionally, it addresses the spacing of transverse reinforcement and the design story drift, ensuring structural integrity and safety through defined safety factors for compression and shear strength The angles of diagonal members and web yielding are also noted, emphasizing the importance of precise measurements and adjustments in structural design.

Allowable Strength Design (ASD) is a method for proportioning structural components to ensure that their allowable strength meets or surpasses the required strength when subjected to ASD load combinations.

The Buckling-Restrained Braced Frame (BRBF) system consists of a casing that encases the steel core along with structural elements connected to it This innovative system is designed to accommodate both transverse expansion and longitudinal contraction of the steel core, allowing for deformations that can reach up to 2.0 times the design story drift.

The casing serves as a critical component that withstands transverse forces acting on the diagonal brace, effectively preventing core buckling It is essential for the casing to have a mechanism to transfer these forces to the rest of the buckling-restraining system However, it exerts minimal or no resistance to forces along the axis of the diagonal brace.

The capacity-limited horizontal seismic load effect, E cl, is calculated according to established provisions and is used in place of E mh This load is then applied as specified by the load combinations outlined in the relevant building code.

The composite plate shear wall with concrete encasement (C-PSW/CE) features a steel plate surrounded by reinforced concrete on one or both sides This design enhances out-of-plane stiffness, effectively preventing buckling of the steel plate while complying with the specifications outlined in Section H6.

The Composite Plate Shear Wall (C-PSW/CF) is a structural element composed of two flat steel web plates filled with concrete, which may include boundary elements This design adheres to the specifications outlined in Section H7, ensuring enhanced structural performance and stability.

A composite slab consists of a reinforced concrete layer that is supported by and bonded to a formed steel deck This configuration acts as a diaphragm, effectively transferring loads to and between the components of the seismic force-resisting system.

Ductile limit states encompass the yielding of members and connections, deformation at bolt holes, and buckling of members that meet the seismic compactness criteria outlined in Table D1.1 However, the rupture of a member or connection, as well as the buckling of a connection element, does not qualify as a ductile limit state.

Face bearing plates are essential components that enhance the structural integrity of reinforced concrete walls or columns These plates are affixed to stiffeners on structural steel beams, ensuring effective load transfer to the concrete Positioned at the concrete's face, they provide crucial confinement, facilitating direct bearing and improving overall stability.

The inverted-V-braced frame is a structural system that enhances stability and strength, similar to the V-braced frame The k-area refers to a specific region of the web, defined by the AISC "k" dimension, which extends 12 inches (38 mm) into the web from the tangent point of the web and flange-web fillet.

K-braced frame A braced-frame configuration in which two or more braces connect to a column at a point other than a beam-to-column or strut-to-column connection.

Visual Welding Inspection

All requirements of the Specification shall apply, except as specifically modified by

Visual welding inspection shall be performed by both quality control and quality assurance personnel As a minimum, tasks shall be as listed in Tables J6.1, J6.2 and

PREQUALIFICATION AND CYCLIC QUALIFICATION

General Requirements

Connections must undergo prequalification based on test data that meets Section K1.3, supported by analytical studies and design models The evidence for prequalification should be comprehensive enough to ensure the connection consistently meets the required story drift angle for SMF, IMF, C-SMF, and C-IMF systems, or the necessary link rotation angle for EBF, within specified limits Additionally, all relevant limit states impacting the connection's stiffness, strength, and deformation capacity, as well as the seismic force-resisting system (SFRS), must be clearly identified, along with the influence of design variables.

Section K1.4 shall be addressed for connection prequalification.

Prequalification of a connection and the associated limits of prequalification shall be established by a connection prequalification review panel (CPRP) approved by the authority having jurisdiction.

Testing Requirements

Connection prequalification data must be derived from tests conducted per Section K2, with the CPRP responsible for determining the number of tests and variables involved The CPRP is also required to provide updated information when limits for a previously prequalified connection are modified To ensure reliability, a sufficient number of tests on diverse specimens must be conducted to demonstrate the connection's ability to handle the necessary story drift angle for SMF, IMF, C-SMF, and C-IMF, as well as the required link rotation angle for EBF, particularly where the link is adjacent to columns Additionally, member size limits for prequalification must adhere to the specifications outlined in Section K2.3b.

Prequalification Variables

To achieve prequalification, it is essential to evaluate how various factors impact connection performance The CPRP will set specific limits on the allowable values for each of these factors to ensure the prequalified connection meets required standards.

4a Beam and Column Parameters for SMF and IMF, Link and Column

(a) Cross-section shape: wide flange, box or other

(b) Cross-section fabrication method: rolled shape, welded shape or other

(g) Beam span-to-depth ratio (for SMF or IMF), or link length (for EBF)

(h) Width-to-thickness ratio of cross-section elements

When considering column orientation in relation to beams or links, there are several connection methods to note: beams or links can be attached to the column flange, connected to the column web, or secured to both the column flange and web Additionally, other connection configurations may also be utilized.

(k) Other parameters pertinent to the specific connection under consideration

4b Beam and Column Parameters for C-SMF and C-IMF

(a) For structural steel members that are part of a composite beam or column: spec- ify parameters required in Section K1.4a (b) Overall depth of composite beam and column

(c) Composite beam span-to-depth ratio

(f) Reinforcement development and splice requirements

(h) Concrete compressive strength and density

(i) Steel anchor dimensions and material specification

(j) Other parameters pertinent to the specific connection under consideration

4c Beam-to-Column or Link-to-Column Relations

(a) Panel zone strength for SMF, IMF, and EBF

(b) Joint shear strength for C-SMF and C-IMF

(c) Doubler plate attachment details for SMF, IMF and EBF

(d) Joint reinforcement details for C-SMF and C-IMF

(e) Column-to-beam (or column-to-link) moment ratio

(a) Identification of conditions under which continuity plates or diaphragm plates are required (b) Thickness, width and depth

(a) Location, extent (including returns), type (CJP, PJP, fillet, etc.) and any reinforcement or contouring required (b) Filler metal classification strength and notch toughness

(c) Details and treatment of weld backing and weld tabs

(d) Weld access holes: size, geometry and finish

(e) Welding quality control and quality assurance beyond that described in Chapter

J, including nondestructive testing (NDT) method, inspection frequency, acceptance criteria and documentation requirements

(b) Bolt grade: ASTM F3125 Grades A325, A325M, A490, A490M, F1852, F2280 or other (c) Installation requirements: pretensioned, snug-tight or other

(d) Hole type: standard, oversize, short-slot, long-slot or other

(e) Hole fabrication method: drilling, punching, sub-punching and reaming, or other

(f) Other parameters pertinent to the specific connection under consideration

4g Reinforcement in C-SMF and C-IMF

(a) Location of longitudinal and transverse reinforcement

(c) Hook configurations and other pertinent reinforcement details

4h Quality Control and Quality Assurance

Requirements that exceed or supplement requirements specified in Chapter J, if any.

All variables and workmanship parameters that exceed AISC, RCSC and AWS requirements pertinent to the specific connection under consideration, as established by the CPRP.

Design Procedure

A comprehensive design procedure must be available for a prequalified connection

The design procedure must address all applicable limit states within the limits of prequalification.

Prequalification Record

A prequalified connection shall be provided with a written prequalification record with the following information:

(a) General description of the prequalified connection and drawings that clearly identify key features and components of the connection

The expected behavior of the connection in both elastic and inelastic ranges is crucial for understanding its performance under load Inelastic action is anticipated to occur at specific locations, which are strategically chosen based on design requirements Additionally, it is essential to identify the limit states that govern the connection's strength and deformation capacity, ensuring safety and structural integrity throughout its service life.

(c) Listing of systems for which connection is prequalified: SMF, IMF, EBF,

(d) Listing of limits for all applicable prequalification variables listed in Section

K1.4 (e) Listing of demand critical welds

(f) Definition of the region of the connection that comprises the protected zone

(g) Detailed description of the design procedure for the connection, as required in

(h) List of references of test reports, research reports and other publications that provided the basis for prequalification(i) Summary of quality control and quality assurance procedures

K2 CYCLIC TESTS FOR QUALIFICATION OF BEAM-TO-COLUMN AND

This section outlines the requirements for qualifying cyclic tests of beam-to-column moment connections in Special Moment Frames (SMF), Intermediate Moment Frames (IMF), Capped Special Moment Frames (C-SMF), and Capped Intermediate Moment Frames (C-IMF), as well as link-to-column connections in Eccentrically Braced Frames (EBF) when mandated by these Provisions The testing aims to demonstrate that these connections meet the necessary criteria for strength and story drift angle or link rotation angle Alternative testing methods may be utilized if approved by the engineer of record and the relevant authority.

Test Subassemblage Requirements

The test subassemblage shall replicate, as closely as is practical, the conditions that will occur in the prototype during earthquake loading The test subassemblage shall include the following features:

(a) The test specimen shall consist of at least a single column with beams or links attached to one or both sides of the column.

(b) Points of inflection in the test assemblage shall coincide with the anticipated points of inflection in the prototype under earthquake loading.

(c) Lateral bracing of the test subassemblage is permitted near load application or reaction points as needed to provide lateral stability of the test subassemblage

Additional lateral bracing of the test subassemblage is not permitted, unless it replicates lateral bracing to be used in the prototype.

Essential Test Variables

The test specimen must closely mimic the relevant design, detailing, construction features, and material properties of the prototype Key variables essential to this replication must be accurately reflected in the test specimen.

Inelastic rotation is determined through an analysis of test specimen deformations and can arise from various factors, including yielding of structural members, connection elements, connectors, reinforcing steel, inelastic deformation of concrete, and slip between members and connection elements This is particularly relevant for beam-to-column moment connections in Special Moment Frames (SMF), Intermediate Moment Frames (IMF), and Concentrically Braced Special Moment Frames (C-SMF).

C-IMF, inelastic rotation is computed based upon the assumption that inelastic action is concentrated at a single point located at the intersection of the centerline of the beam with the centerline of the column For link-to-column connections in EBF, inelastic rotation shall be computed based upon the assumption that inelastic action is concentrated at a single point located at the intersection of the centerline of the link with the face of the column.

Inelastic rotation in the test specimen must be generated through inelastic actions in the same members and connection elements as expected in the prototype This includes areas such as the beam or link, the column panel zone, the column outside the panel zone, and connection elements The inelastic rotation percentage in each member or connection element of the test specimen should remain within 25% of the expected total inelastic rotation percentage for the corresponding components in the prototype.

The size of the beam or link used in the test specimen shall be within the following limits:

(a) The depth of the test beam or link shall be no less than 90% of the depth of the prototype beam or link.

For SMF, IMF, and EBF, the weight per foot of the test beam or link must be at least 75% of the weight per foot of the corresponding prototype beam or link.

For C-SMF and C-IMF, the structural steel member used in the test beam must have a weight per foot that is at least 75% of the weight per foot of the structural steel member in the prototype beam.

The size of the column used in the test specimen shall correctly represent the inelastic action in the column, as per the requirements in Section K2.3a In addition, in SMF,

In the context of testing, the depth of the test column in IMF and EBF must be at least 90% of the prototype column's depth Similarly, for C-SMF and C-IMF, the depth of the structural steel member in the test column should not be less than 90% of the depth of the corresponding structural steel member in the prototype column.

The width-to-thickness ratios of compression elements in steel members must comply with the specified limitations outlined in these provisions for SMF, IMF, C-SMF, C-IMF, or EBF members.

In certain cases, the width-to-thickness ratios of compression elements in test specimens can exceed the limitations outlined in these Provisions, provided that two specific conditions are satisfied.

The compression elements of the test specimen maintain width-to-thickness ratios that are equal to or greater than those of the corresponding prototype members.

Design features aimed at preventing local buckling in test specimens, including concrete encasement and filling of steel members, reflect the essential characteristics found in the corresponding prototype designs.

Extrapolation beyond the limitations stated in this section is permitted subject to qualified peer review and approval by the authority having jurisdiction.

3c Reinforcing Steel Amount, Size and Detailing

The longitudinal reinforcing bars must collectively have a total area that is at least 75% of the area found in the prototype, with each individual bar required to maintain an area no smaller than 70% of the maximum bar size used in the prototype.

Design approaches and methods used for anchorage and development of reinforcement, and for splicing reinforcement in the test specimen shall be representative of the prototype.

The amount, arrangement and hook configurations for transverse reinforcement shall be representative of the bond, confinement and anchorage conditions of the prototype.

The connection details in the test specimen must closely mirror those of the prototype, ensuring that the connection elements are a full-scale representation of the prototype's components for the sizes being tested.

Continuity plates in the test specimen must be sized and connected to closely resemble those used in the prototype connection.

3f Steel Strength for Steel Members and Connection Elements

The following additional requirements shall be satisfied for each steel member or connection element of the test specimen that supplies inelastic rotation by yielding:

The yield strength must be determined according to the guidelines outlined in Section K2.6a For this section, it is not permissible to use yield stress values from certified material test reports instead of conducting physical testing.

(b) The yield strength of the beam flange as tested in accordance with Section

K2.6a shall not be more than 15% below R y F y for the grade of steel to be used for the corresponding elements of the prototype.

Loading History

The test specimen shall be subjected to cyclic loads in accordance with the requirements prescribed in Section K2.4b for beam-to-column moment connections in SMF,

IMF, C-SMF, and C-IMF, and in accordance with the requirements prescribed in Sec- tion K2.4c for link-to-column connections in EBF.

To qualify connections for SMF, IMF, C-SMF, or C-IMF, loading sequences with orthogonal column arrangements must be applied to both axes, following the loading sequence outlined in Section K2.4b The beams used for each axis should reflect the most demanding combination for which qualification or prequalification is being pursued.

In lieu of concurrent application about each axis of the loading sequence specified in Section K2.4b, the loading sequence about one axis shall satisfy requirements of

In Section K2.4b, a constant concurrent load, matching the anticipated strength of the beam linked to the column along its orthogonal axis, must be applied around that same orthogonal axis.

Loading sequences other than those specified in Sections K2.4b and K2.4c are permitted to be used when they are demonstrated to be of equivalent or greater severity.

4b Loading Sequence for Beam-to-Column Moment Connections

Cyclic tests for beam-to-column moment connections in Special Moment Frames (SMF), Intermediate Moment Frames (IMF), Concentrically Braced Special Moment Frames (C-SMF), and Concentrically Braced Intermediate Moment Frames (C-IMF) must be performed by regulating the story drift angle, θ, applied to the test specimen, as outlined in the specifications.

Continue loading at increments of θ = 0.01 rad, with two cycles of loading at each step.

4c Loading Sequence for Link-to-Column Connections

Cyclic tests for link-to-column moment connections in EBF must be conducted by regulating the overall link rotation angle, γ total, applied to the test specimen.

Continue loading at increments of γ total = 0.02 rad, with one cycle of loading at each step.

Instrumentation

Sufficient instrumentation shall be provided on the test specimen to permit measure- ment or calculation of the quantities listed in Section K2.7.

Testing Requirements for Material Specimens

6a Tension Testing Requirements for Structural Steel Material Specimens

Tension testing must be performed on samples from material test plates in compliance with Section K2.6c, ensuring that these plates are sourced from the same heat of steel as the test specimen While results from certified material test reports can be reported, they cannot replace physical testing as required in this section The tension testing and reporting are essential for specific portions of the test specimen.

(a) Flange(s) and web(s) of beams and columns at standard locations

(b) Any element of the connection that supplies inelastic rotation by yielding

6b Tension Testing Requirements for Reinforcing Steel Material Specimens

Tension testing shall be conducted on samples of reinforcing steel in accordance with

In Section K2.6c, it is mandated that samples of reinforcing steel for material tests must originate from the same heat as the test specimen While tension-test results from certified material test reports are to be documented, they cannot replace physical testing as required by this section.

6c Methods of Tension Testing for Structural and Reinforcing Steel Material

Tension testing shall be conducted in accordance with ASTM A6/A6M, ASTM A370, and ASTM E8, as applicable, with the following exceptions:

(a) The yield strength, F y , that is reported from the test shall be based upon the yield strength definition in ASTM A370, using the offset method at 0.002 in./in strain.

(b) The loading rate for the tension test shall replicate, as closely as practical, the loading rate to be used for the test specimen.

Concrete test cylinders must be fabricated and cured according to ASTM C31 standards A minimum of three cylinders from each concrete batch used in the test specimen must be tested within five days before or after the cyclic qualifying test Testing of the concrete cylinders should follow ASTM C39 guidelines The average compressive strength of these cylinders must be between 90% and 150% of the specified compressive strength for the corresponding member or connection element Additionally, the average compressive strength should not exceed 3000 psi (20.7 MPa) above the specified compressive strength for the relevant component.

If the average compressive strength of three cylinders falls outside the specified limits, the specimen may still be deemed acceptable This is contingent upon the provision of supporting calculations or other evidence that illustrates how the variation in concrete strength will influence the performance of the connection.

6e Testing Requirements for Weld Metal Material Specimens

Weld metal testing must be performed on samples taken from the material test plate, utilizing the same filler metal classification, manufacturer, brand, or trade name, and diameter, while maintaining the same average heat input used during the welding of the test specimen The tensile strength and CVN toughness of the weld material specimens will be assessed following the Standard Methods for Mechanical Testing.

According to AWS B4.0/B4.0M standards, it is not permissible to substitute tensile strength and CVN toughness values from a manufacturer's certificate of conformance for physical testing in weld evaluations.

The same WPS shall be used to make the test specimen and the material test plate

The material test plate must be constructed from base metal that matches the grade and type of the test specimen, though it is not necessary to use the same heat If the average heat input for the material test plate deviates by more than ±20% from that of the test specimen, a new test plate must be produced and evaluated.

Each test specimen must have a written report that complies with the authority having jurisdiction and this section's requirements The report must comprehensively document all essential features and outcomes of the test, including specific information as outlined in the guidelines.

(a) A drawing or clear description of the test subassemblage, including key dimensions, boundary conditions at loading and reaction points, and location of lateral braces.

The connection detail drawing must include essential specifications such as member sizes, steel grades, dimensions of connection elements, welding details with filler metal, bolt hole sizes and locations, bolt sizes and grades, as well as the specified compressive strength and density of concrete Additionally, it should outline reinforcing bar sizes, grades, locations, and details regarding splices and anchorage, along with any other relevant connection details.

(c) A listing of all other essential variables for the test specimen, as listed in Section

(d) A listing or plot showing the applied load or displacement history of the test specimen.

(e) A listing of all welds to be designated demand critical.

(f) Definition of the region of the member and connection to be designated a protected zone.

A graph illustrating the relationship between the applied load and the displacement of the test specimen is essential Displacement measurements should be taken at or near the load application point It is crucial to clearly indicate the specific locations on the test specimen where both load and displacement measurements were recorded.

A graph illustrating the relationship between beam moment and story drift angle is essential for beam-to-column moment connections, while a separate graph should depict the link shear force against link rotation angle for link-to-column connections For accurate analysis, the beam moment and story drift angle must be calculated relative to the column's centerline.

The article discusses the story drift angle and the total inelastic rotation observed in the test specimen It emphasizes the identification of components within the specimen that contribute to the total inelastic rotation Additionally, it requires a detailed report on the contribution of each component to the overall inelastic rotation, along with a clear explanation of the computation method used for determining these inelastic rotations.

The article provides a chronological record of test observations, detailing key phenomena such as yielding, slip, instability, cracking, and rupture of steel elements, as well as concrete cracking and other damage to any relevant portions of the test specimen.

(k) The controlling failure mode for the test specimen If the test is terminated prior to failure, the reason for terminating the test shall be clearly indicated.

(l) The results of the material specimen tests specified in Section K2.6.

(m) The welding procedure specifications (WPS) and welding inspection reports.

Additional drawings, data, and discussion of the test specimen or test results are permitted to be included in the report.

The test specimen must meet the strength and drift angle requirements outlined for SMF, IMF, C-SMF, C-IMF, or EBF connections Additionally, it should be able to endure the specified story drift angle or link rotation angle for a minimum of one complete loading cycle.

K3 CYCLIC TESTS FOR QUALIFICATION OF BUCKLING-

This section outlines the requirements for qualifying cyclic tests of individual buckling-restrained braces and their subassemblages, as mandated by these provisions Testing individual braces aims to confirm their compliance with strength and inelastic deformation requirements while also determining maximum brace forces for adjacent elements' design Conversely, the testing of brace subassemblages ensures that the design can effectively accommodate deformation and rotational demands Additionally, these tests demonstrate that the hysteretic behavior of the brace within the subassemblage aligns with that of the individually tested brace elements.

Alternative testing requirements are permitted when approved by the engineer of record and the authority having jurisdiction This section provides only minimum recommendations for simplified test conditions.

The subassemblage test specimen shall satisfy the following requirements:

Tiêu đề	Seismic Provisions for Structural Steel Buildings
Trường học	American Institute of Steel Construction
Chuyên ngành	Structural Steel
Thể loại	standard
Năm xuất bản	2016
Thành phố	Chicago

Định dạng
Số trang	480
Dung lượng	7,27 MB