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SynC · Editorial revision

Structural Steel Connections

Revision7
EditedOct 12, 2026
StatusCurrent
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Current revision. This is editorial revision 7, the current text of this standard. Read it on the standard's page.

SynC Standards Team — Specifier (Platform Standards) ✓ OfficialDiscloses employment SynC (SynC Platform Team)
Datasheet constraints: every range, checkbox and listbox field now states its direction

1 Scope

NOTE This standard governs how the members furnished under Structural Steel FramingStructural Steel FramingResolves to the current adopted revision.sync/structural-steel-framing are fastened to one another: who designs each class of connection, the bolt assemblies and the condition they are installed to, the surfaces they clamp, the holes they pass through, the configuration of the groove welds that complete moment connections and splices, and the inspection that proves each joint reached the condition its design assumes. (1.1)
NOTE The connection classes in scope are simple shear connections (shear tabs, double-angle, single-angle, seated, and shear end-plate connections), fully restrained and partially restrained moment connections, vertical and horizontal bracing connections with their gusset plates, column splices, and the steel side of column base plate connections, together with the angles, tees, plates, stiffeners, continuity plates, and doubler plates that complete them. (1.2)
NOTE A connection is the point at which the load path is either made or broken, and most of what makes it is invisible after erection: the pretension in a bolt, the condition of a faying surface, and the soundness of a groove weld root cannot be seen in the finished structure, so the procedures and records that establish those conditions are treated by this standard as load-bearing requirements rather than paperwork. (1.3)
NOTE This standard is a layer over two companion standards and repeats neither: Structural Steel FramingStructural Steel FramingResolves to the current adopted revision.sync/structural-steel-framing keeps the members, fabrication, hole forming, erection, coatings, certification, and warranty, and Welding RequirementsWelding RequirementsResolves to the current adopted revision.sync/welding-requirements keeps the welding quality program of procedure and welder qualification, consumables, preheat, weld acceptance, and nondestructive examination. (1.4)
NOTE The following are governed elsewhere and are outside this standard: (1.5)
  • the framing members themselves, their fabrication, hole forming, camber, erection sequence, tolerances, and shop and field coatings
  • welding procedure and welder qualification, welding consumables and their storage, preheat and interpass control, weld acceptance criteria, and the nondestructive examination program
  • anchor rods, their embedment, and the concrete they are cast into
  • connections of open-web steel joists and joist girders to their supports
  • steel deck attachment, puddle welds, and sidelap fasteners
  • cold-formed light-gauge steel connections
  • fasteners for miscellaneous and architectural metalwork
  • stainless steel and aluminum connections
1.6 Connections shall conform to ANSI/AISC 360 Chapter J, to ANSI/AISC 303 for trade practice and the assignment of connection design responsibility, to the RCSC Specification for Structural Joints Using High-Strength Bolts for high-strength bolting, and to AWS D1.1 for welding.
1.7 Where the seismic force-resisting system is designed under ANSI/AISC 341, the connections of that system shall additionally conform to ANSI/AISC 341, and welds designated demand-critical shall conform to AWS D1.8.
1.8 Connection geometry and the member sizes at each connection shall be as indicated on the connection detail sheets.
NOTE This standard states project-wide policy for each connection class in the datasheet; the connection schedules carry the exceptions for individual connections, and where the two differ for a given connection, the schedule governs that connection. (1.9)

2 Referenced Standards

2.1 Connections shall comply with the latest adopted edition of each of the following unless a specific edition is cited.
2.2 Where the contract documents, the Authority Having Jurisdiction, or two referenced standards impose conflicting requirements, the more stringent requirement shall govern unless the Engineer of Record directs otherwise in writing.
Standard Title
ANSI/AISC 360 Specification for Structural Steel Buildings
ANSI/AISC 303 Code of Standard Practice for Steel Buildings and Bridges
ANSI/AISC 341 Seismic Provisions for Structural Steel Buildings
ANSI/AISC 358 Prequalified Connections for Special and Intermediate Steel Moment Frames for Seismic Applications
AISC Steel Construction Manual Standard connection tables used where connection selection is completed by the fabricator
RCSC Specification for Structural Joints Using High-Strength Bolts
AWS D1.1/D1.1M Structural Welding Code — Steel
AWS D1.8/D1.8M Structural Welding Code — Seismic Supplement
ASTM F3125/F3125M High Strength Structural Bolts and Assemblies, Steel and Alloy Steel, Heat Treated, Inch Dimensions 120 ksi and 150 ksi Minimum Tensile Strength, and Metric Dimensions 830 MPa and 1040 MPa Minimum Tensile Strength
ASTM A563/A563M Carbon and Alloy Steel Nuts
ASTM F436/F436M Hardened Steel Washers Inch and Metric Dimensions
ASTM F959/F959M Compressible-Washer-Type Direct Tension Indicators for Use with Structural Fasteners, Inch and Metric Series
ASTM F606/F606M Determining the Mechanical Properties of Externally and Internally Threaded Fasteners, Washers, Direct Tension Indicators, and Rivets
ASTM F2329/F2329M Zinc Coating, Hot-Dip, Requirements for Application to Carbon and Alloy Steel Bolts, Screws, Washers, Nuts, and Special Threaded Fasteners
ASTM B695 Coatings of Zinc Mechanically Deposited on Iron and Steel
ASTM F1136/F1136M Zinc/Aluminum Corrosion Protective Coatings for Fasteners
ASTM F2833 Corrosion Protective Fastener Coatings with Zinc Rich Base Coat and Aluminum Organic/Inorganic Type
ASTM A123/A123M Zinc (Hot-Dip Galvanized) Coatings on Iron and Steel Products
ASCE/SEI 7 Minimum Design Loads and Associated Criteria for Buildings and Other Structures
IBC International Building Code (Chapter 17, Special Inspections and Tests)

3 Submittals

3.1 Action Submittals

3.1.1 The Contractor shall submit the following for review before any connection is fabricated or installed:
  • connection shop drawings showing every connection element with its plate size and grade, bolt grade, diameter, and finish, hole type and size, edge and end distances, gauges, weld symbols, weld sizes, joint geometry, backing and weld tab disposition, weld access hole geometry, and the faying surface treatment at each slip-critical joint
  • connection design calculations for each connection class whose design is not complete on the contract documents, sealed by an engineer licensed in the jurisdiction of the project
  • bolt assembly certifications for each lot of high-strength fastener assemblies, giving the ASTM F3125 grade, type, and finish, the matching nut and washer specifications, the lot identification, the manufacturer's certified mechanical test results, and the rotational-capacity test results where this standard requires them
  • direct tension indicator product data and ASTM F959 conformance, where direct tension indicators are a permitted pretensioning method
  • product data and the RCSC slip-class qualification report for any coating to be applied to a slip-critical faying surface
  • the pre-installation verification plan, identifying the tension calibrator to be used, the occasions on which verification will be performed, and the record to be kept
  • the bolting inspection plan, identifying the inspection tasks, the sampling, and the personnel qualifications for each joint condition on the project
Action Submittal Packagecheckbox
☑ Connection shop drawings
☐ Connection design calculations
☑ Bolt assembly certifications and rotational-capacity test results
☐ Direct tension indicator product data
☐ Faying surface coating slip-class qualification
☑ Pre-installation verification plan
☑ Bolting inspection plan
NOTE Welding procedure specifications, procedure qualification records, welder qualification records, filler metal certifications, and the nondestructive examination plan are submitted under Welding RequirementsWelding RequirementsResolves to the current adopted revision.sync/welding-requirements and are not resubmitted under this standard. (3.1.2)
3.1.3 Connection shop drawings shall be coordinated with the member shop drawings submitted under Structural Steel FramingStructural Steel FramingResolves to the current adopted revision.sync/structural-steel-framing so that connection elements, hole patterns, and weld access conditions agree with the approved members.
3.1.4 No connection shall be fabricated or installed until the submittals covering its connection class have been reviewed and returned.

3.2 Closeout Submittals

3.2.1 The Contractor shall submit the following before the structural steel is accepted:
  • bolt installation records organized by connection, recording the joint condition, the pretensioning method, the fastener lot installed, and the inspection result for each pretensioned and slip-critical joint
  • pre-installation verification records for each lot and each occasion on which verification was performed
  • faying surface verification records for each slip-critical joint, recording the surface treatment and, where a coating was applied, its type and dry film thickness
  • a nonconformance log listing every bolt or connection rejected, its disposition, the corrective action, and the re-inspection result
  • certificates of compliance from the fabricator and the erector stating that the connections were made in accordance with the contract documents, the RCSC Specification, and AWS D1.1
Closeout Submittal Packagecheckbox
☑ Bolt installation records by connection
☑ Pre-installation verification records
☑ Faying surface verification records
☑ Nonconformance log
☑ Certificates of compliance
NOTE Weld inspection and nondestructive examination records for connection welds are delivered under Welding RequirementsWelding RequirementsResolves to the current adopted revision.sync/welding-requirements. (3.2.2)

4 Quality Assurance

4.1 Quality Control and Quality Assurance Framework

NOTE AISC 360 Chapter N separates quality control, the fabricator's and erector's own program, from quality assurance, the independent verification performed by an inspector who has no financial relationship with the fabricator or the erector. (4.1.1)
4.1.2 Quality assurance inspection shall not relieve the fabricator or the erector of any quality control responsibility.
4.1.3 The bolting inspection plan shall identify each task as one performed on a random, unannounced basis without delaying production or as one performed for every joint, in accordance with the inspection tables of AISC 360 Chapter N.
4.1.4 Where the adopted building code requires special inspection of high-strength bolting, that inspection shall be performed under the special inspection program administered in accordance with Special Inspections And TestingSpecial Inspections and Structural TestingResolves to the current adopted revision.sync/special-inspections-and-testing.

4.2 Bolting Inspection Personnel

4.2.1 Quality assurance inspection of high-strength bolting shall be performed by an inspector holding the qualification indicated in the datasheet.
Bolting Quality Assurance Inspector Qualificationselect
ICC Structural Steel and Bolting Special Inspector certification
Documented training in RCSC installation and inspection accepted by the Authority Having Jurisdiction
Direct supervision by a licensed engineer
NOTE A welding inspector's certification qualifies the holder to inspect welds and does not by itself qualify the holder to inspect bolting; the two are separate qualifications and a single individual may hold both. (4.2.2)
NOTE Welding inspector and nondestructive examination technician qualifications are established in Welding RequirementsWelding RequirementsResolves to the current adopted revision.sync/welding-requirements, and fabricator, erector, and welder qualifications are established in Structural Steel FramingStructural Steel FramingResolves to the current adopted revision.sync/structural-steel-framing and Welding RequirementsWelding RequirementsResolves to the current adopted revision.sync/welding-requirements. (4.2.3)

4.3 Fabricator and Erector Qualification

4.3.1 Connections shall be fabricated and installed only by the fabricator and erector qualified under Structural Steel FramingStructural Steel FramingResolves to the current adopted revision.sync/structural-steel-framing.
4.3.2 Where the seismic force-resisting system is designed under AISC 341, the fabricator shall hold the certification category that Structural Steel FramingStructural Steel FramingResolves to the current adopted revision.sync/structural-steel-framing requires for that work.

5 Connection Design Responsibility

NOTE AISC 303 recognizes three arrangements for the design of a connection: the Engineer of Record completes the design and shows it on the contract documents; the Engineer of Record states the design forces and the fabricator completes the connection using the standard connections of the AISC Steel Construction Manual; or the Engineer of Record states the design forces and delegates the design to a licensed engineer retained by the fabricator. (5.1)
NOTE Which arrangement applies is a project policy decided separately for each connection class, because the classes carry different demands and different design effort: a shear connection is usually a catalog selection, a moment connection in a seismic frame is a prequalified assembly with its own design rules, and a base plate is tied to the anchor rods and foundation the Engineer of Record already designs. (5.2)
5.3 The design responsibility for simple shear connections shall be as indicated in the datasheet.
Simple Shear Connection Design Responsibilityradio
○ Complete design by the Engineer of Record
○ Selection by the fabricator from AISC Steel Construction Manual standard connections for the stated reactions
○ Design delegated to a licensed engineer retained by the fabricator
5.4 The design responsibility for moment connections shall be as indicated in the datasheet.
Moment Connection Design Responsibilityradio
○ Complete design by the Engineer of Record
○ Selection by the fabricator from AISC Steel Construction Manual standard connections for the stated demands
○ Design delegated to a licensed engineer retained by the fabricator
5.5 The design responsibility for bracing and gusset plate connections shall be as indicated in the datasheet.
Bracing Connection Design Responsibilityradio
○ Complete design by the Engineer of Record
○ Selection by the fabricator from AISC Steel Construction Manual standard connections for the stated forces
○ Design delegated to a licensed engineer retained by the fabricator
5.6 The design responsibility for column splices and column base plate connections shall be as indicated in the datasheet.
Column Splice and Base Plate Connection Design Responsibilityradio
○ Complete design by the Engineer of Record
○ Selection by the fabricator from AISC Steel Construction Manual standard connections for the stated forces
○ Design delegated to a licensed engineer retained by the fabricator
NOTE No arrangement is the norm across projects for any connection class, because the split between Engineer of Record design and fabricator design follows regional practice, the licensing rules of the jurisdiction, and the complexity of the frame rather than settling on one answer, so these fields carry no default. (5.7)
5.8 For every connection class whose design is not complete on the contract documents, the design forces, moments, and any rotation or ductility demands shall be as indicated on the structural framing plans and connection schedules.
5.9 Where the design of a connection class is delegated, the calculations shall be prepared and sealed by an engineer licensed in the jurisdiction of the project and shall be submitted with the connection shop drawings.
NOTE Where the design of a connection class is delegated, the Engineer of Record's review of the delegated submittal confirms that the connection satisfies the stated demands and does not transfer responsibility for the detailed design back to the Engineer of Record. (5.10)
5.11 Where a connection is neither designed on the contract documents nor assigned a design force, the Contractor shall request the design force from the Engineer of Record before the connection is designed, fabricated, or installed.
5.12 Where the datasheet assigns a basis for simple shear connections whose reaction is not stated, that basis shall be used in place of a request to the Engineer of Record.
Reaction Basis for Simple Shear Connections Without a Stated Reactionradio
○ One-half of the beam's maximum total uniform load from the AISC Steel Construction Manual
○ The reaction produced by the beam's full uniform load capacity
○ Reaction obtained from the Engineer of Record in every case
5.13 Every connection shall develop the forces stated for it, and a connection shall not be reduced below the stated demand on the basis of the actual member loading unless the Engineer of Record approves the reduction in writing.

6 Seismic Force-Resisting System Connections

6.1 Applicability of AISC 341

6.1.1 Whether the connection provisions of AISC 341 apply to the seismic force-resisting system shall be as indicated in the datasheet.
AISC 341 Connection Provisions for the Seismic Force-Resisting Systemradio
○ Apply to the connections of the seismic force-resisting system
○ Do not apply
Derived — Seismic Design CategorySeismic Design CategoryParameterEach project supplies its own value.seismic-design-category and whether the seismic force-resisting system is designated as detailed under AISC 341 in accordance with ASCE/SEI 7 (by default)
NOTE The applicability follows from the seismic design category together with the system the structure was designed as: a system assigned a response modification coefficient that ASCE/SEI 7 permits without seismic detailing is designed under AISC 360 alone even in a category where a detailed system would invoke AISC 341, so the category by itself does not settle the question. (6.1.2)
6.1.3 Where AISC 341 applies, the connections of the seismic force-resisting system shall be identified as such on the connection shop drawings.

6.2 Seismic Moment Connections

6.2.1 Where AISC 341 applies to a moment frame, the basis on which its beam-to-column moment connections are qualified shall be as indicated in the datasheet.
Seismic Moment Connection Qualification Basisradio
○ Prequalified connection under AISC 358
○ Connection qualified by cyclic testing under AISC 341
○ Not applicable
NOTE A prequalified connection carries its own detailing, welding, bolting, and inspection rules that form part of the qualification, and a deviation from the prequalified detail removes the connection from prequalification. (6.2.2)
6.2.3 Where a prequalified connection is used, the connection shall be detailed, fabricated, and inspected in accordance with AISC 358 for that connection type, and no element of the prequalified detail shall be altered without the Engineer of Record's written approval.
6.2.4 Where a connection is qualified by cyclic testing, the qualifying test report shall be submitted with the connection design calculations.

6.3 Protected Zones

NOTE A protected zone is the region of a seismic member in which inelastic straining is expected, and a hole, notch, arc strike, tack weld, or attachment weld within it can nucleate a fracture under cyclic earthquake demand. (6.3.1)
6.3.2 Where AISC 341 applies, the extent of each protected zone shall be as indicated on the structural framing plans and elevations.
6.3.3 Within a protected zone, no hole shall be drilled or punched, no cope or notch shall be cut, no arc strike or tack weld shall be made, and no attachment shall be welded, except as shown on the approved connection shop drawings or approved in writing by the Engineer of Record.
6.3.4 The protected zone restriction applies to every trade whose work approaches the member, and the erector shall mark each protected zone on the member and communicate the restriction to the trades that follow.
6.3.5 A discontinuity introduced into a protected zone shall be reported to the Engineer of Record, and shall not be repaired until the Engineer of Record has approved the repair procedure in writing.

6.4 Bolted Joints in the Seismic Force-Resisting System

6.4.1 Where AISC 341 applies, bolts in the connections of the seismic force-resisting system shall be pretensioned high-strength bolts.
6.4.2 Where AISC 341 applies, the faying surfaces of bolted joints in the seismic force-resisting system shall be prepared to at least the Class A slip condition, whether or not the joint is designed as slip-critical.
6.4.3 Where AISC 341 applies, bolts and welds shall not share the same force in any connection of the seismic force-resisting system.
6.4.4 Where AISC 341 applies, bolt holes in the connections of the seismic force-resisting system shall be standard holes or short-slotted holes with the slot perpendicular to the direction of load, except where AISC 341 or the prequalified connection permits another hole type.
NOTE Demand-critical welds are designated by the Engineer of Record and are governed for filler metal toughness, preheat, and examination by Welding RequirementsWelding RequirementsResolves to the current adopted revision.sync/welding-requirements; this standard governs the backing, weld tab, and access hole configuration at those welds under Welded Connection Configurations. (6.4.5)

7 High-Strength Bolt Assemblies

7.1 Bolt Grade, Type, and Finish

NOTE ASTM F3125 consolidates the former A325, A490, F1852, and F2280 standards into one specification covering two strength grades in hex-head and twist-off styles, and every high-strength structural bolt on the project is furnished under it. (7.1.1)
7.1.2 The high-strength bolt grade shall be as indicated in the datasheet.
High-Strength Bolt Graderadio
● ASTM F3125 Grade A325
○ ASTM F3125 Grade A490
NOTE Grade A490 develops a higher shear and tension strength per bolt than Grade A325, which resolves a connection whose force will not fit in the available gauge or bolt count at the lower grade, at the cost of a bolt that ASTM F3125 does not permit to be galvanized and that the RCSC Specification requires to be pretensioned wherever it carries tension. (7.1.3)
7.1.4 The bolt steel type shall be as indicated in the datasheet.
High-Strength Bolt Steel Typeradio
● Type 1
○ Type 3
NOTE Type 3 is the weathering steel bolt, furnished with atmospheric corrosion resistance comparable to that of weathering structural steel so that the fastener weathers with the member instead of rusting ahead of it. (7.1.5)
7.1.6 Where the connected members are weathering steel left uncoated, bolt assemblies shall be Type 3.
7.1.7 The bolt finish shall be as indicated in the datasheet.
High-Strength Bolt Finishselect
Plain uncoated
Hot-dip galvanized to ASTM F2329
Mechanically deposited zinc to ASTM B695 Class 55
Zinc-aluminum coating to ASTM F1136 Grade 3 or ASTM F2833 Grade 1
7.1.8 Grade A490 bolts shall not be hot-dip galvanized or mechanically galvanized, because the high-strength steel is susceptible to hydrogen embrittlement in the pickling and coating process and ASTM F3125 prohibits zinc coating of that grade.
7.1.9 Where a coated finish is required on a Grade A490 bolt, the finish selected shall be one of the zinc-aluminum coatings ASTM F3125 permits on that grade.
7.1.10 Where the connected members are hot-dip galvanized, the bolt finish selected shall be one of the coated finishes.
7.1.11 Where a coated finish is selected, the bolt finish shall be coordinated with the member coating system established under Structural Steel FramingStructural Steel FramingResolves to the current adopted revision.sync/structural-steel-framing.
7.1.12 Nuts shall conform to ASTM A563 in the grade and finish that ASTM F3125 assigns to the bolt grade and finish, and washers shall conform to ASTM F436 in the matching finish.
7.1.13 Nuts for coated bolts shall be overtapped to clear the coating thickness on the bolt threads and shall be lubricated by the manufacturer, and a nut for a plain bolt shall not be run onto a coated bolt.

7.2 Bolt Diameter

7.2.1 The bolt diameter used in connections where no other diameter is indicated shall be as indicated in the datasheet.
Bolt Diameter Where Not Otherwise Indicatedrange
in.
0.50.6250.750.87511.1251.251.5
Per drawings — the connection schedules and details (deferred by default)
7.2.2 Where the connection details show a different diameter at a connection, that diameter shall govern at that connection.
7.2.3 Bolt length shall be selected so that the end of the bolt is at least flush with the outer face of the nut after installation, with the thread condition at the shear plane as the connection design assumes.

7.3 Matched Assemblies

7.3.1 A high-strength bolt shall be furnished and installed as a matched assembly of bolt, nut, and washer, and direct tension indicator where used, from a single production lot, lubricated and tested together.
NOTE The lubricant on a fastener assembly is part of the tested assembly, and a nut from another lot, a nut whose lubricant has washed off, or a bolt that has already been pretensioned once will not reach the pretension the lot's test records demonstrate. (7.3.2)
7.3.3 Components from different lots shall not be mixed within an assembly, and a lot shall not be combined with another lot in storage or at the work point.
7.3.4 Rotational-capacity testing shall be performed on the assemblies indicated in the datasheet, in accordance with ASTM F3125, and the results shall be included in the bolt assembly certification.
Rotational-Capacity Testing of Bolt Assembliesradio
● Coated assemblies as ASTM F3125 requires
○ Every lot of assemblies regardless of finish
NOTE The rotational-capacity test drives the assembly well past its required pretension and confirms that the lubricated nut, the bolt threads, and the coating together let the bolt strain without stripping or seizing; ASTM F3125 requires it on coated assemblies because a coating changes the thread friction, and a project extends it to plain assemblies where the cost of a lot that stalls at snug is high enough to justify testing every lot. (7.3.5)

8 Bolted Joint Condition

8.1 Joint Conditions Defined

NOTE AISC 360 and the RCSC Specification recognize three conditions for a high-strength bolted joint: snug-tight, in which the plies are drawn into firm contact and the bolt carries no specified pretension; pretensioned, in which each bolt is tensioned to the minimum pretension of AISC 360 Table J3.1; and slip-critical, in which the bolts are pretensioned and the faying surfaces are prepared to a slip class so that the joint carries service load by friction without slipping into bearing. (8.1.1)
NOTE The joint condition is a property of the connection design, not of the installer's effort, because a snug-tight joint is designed for bearing and a slip-critical joint is designed for friction, and the same bolt group has a different strength under each. (8.1.2)
NOTE AISC 360 Section J3.1 requires pretensioned or slip-critical installation for column splices and beam-to-column connections in structures of the height it states, for connections supporting running machinery and cranes, for connections whose bolts are subject to fatigue, for joints using Grade A490 bolts in tension, and for any joint the Engineer of Record so designates, and AISC 341 requires it throughout the seismic force-resisting system; these code triggers govern regardless of the class policy the datasheet selects. (8.1.3)
8.1.4 Where AISC 360, AISC 341, or the RCSC Specification requires pretensioned or slip-critical installation for a joint, that requirement shall govern over any less demanding class policy selected in the datasheet.

8.2 Joint Condition by Connection Class

8.2.1 The joint condition for simple shear connections shall be as indicated in the datasheet.
Joint Condition for Simple Shear Connectionsradio
● Snug-tight
○ Pretensioned
○ Slip-critical
8.2.2 The joint condition for bolted moment connections shall be as indicated in the datasheet.
Joint Condition for Bolted Moment Connectionsradio
○ Snug-tight
● Pretensioned
○ Slip-critical
8.2.3 The joint condition for bracing and gusset plate connections shall be as indicated in the datasheet.
Joint Condition for Bracing Connectionsradio
○ Snug-tight
○ Pretensioned
○ Slip-critical
8.2.4 The joint condition for column splices shall be as indicated in the datasheet.
Joint Condition for Column Splicesradio
○ Snug-tight
○ Pretensioned
○ Slip-critical
8.2.6 Individual connections whose joint condition differs from the class policy shall be as indicated on the connection schedules.
8.2.7 The fabricator and erector shall not downgrade a joint from the condition designated for it, and a joint designated slip-critical shall not be installed as pretensioned without the faying surface treatment this standard requires.
NOTE Slip-critical designation is required by AISC 360 wherever slip at the faying surface would be detrimental to the performance of the structure, wherever bolts pass through oversized holes, and wherever bolts pass through slotted holes with the slot parallel to the direction of load. (8.2.8)

9 Pretensioning

9.1 Permitted Pretensioning Methods

9.1.1 The pretensioning methods permitted on the project shall be as indicated in the datasheet.
Permitted Pretensioning Methodscheckbox
Any of:
☑ Turn-of-nut
☑ Calibrated wrench
☑ Twist-off tension-control bolt
☑ Direct tension indicator
NOTE Each RCSC method reaches the minimum pretension of AISC 360 Table J3.1 by a different mechanism, and the choice among the permitted methods belongs to the erector because it turns on the crew's tooling and on the access at each joint. (9.1.2)
NOTE Turn-of-nut brings the bolt to snug, matchmarks the nut and the protruding bolt end, and turns the nut a further rotation prescribed by the RCSC Specification for the bolt length and the slope of the faying surfaces, straining the bolt into the range where the pretension is insensitive to the exact rotation. (9.1.3)
NOTE Calibrated wrench sets the wrench on a tension calibrator using assemblies from the lot in use so that the wrench's shut-off corresponds to the required pretension under that day's lubrication and thread condition, and it is the method most sensitive to a lot that has lost its lubricant, because torque is what it controls and friction is what it cannot see. (9.1.4)
NOTE A twist-off tension-control bolt carries a splined tip that shears at a calibrated torque, leaving visible evidence that the assembly reached its tested pretension, and it needs clearance behind the joint for the installation tool. (9.1.5)
NOTE A direct tension indicator is a washer with formed protrusions that flatten as the bolt is tensioned, and a feeler gauge at the gap between the protrusions confirms the pretension was reached regardless of the tool that produced it. (9.1.6)
9.1.7 The erector shall select the pretensioning method for each connection from the permitted methods, shall identify it in the pre-installation verification plan, and shall not change method on a connection without repeating the pre-installation verification for the new method.
9.1.8 A method not permitted in the datasheet shall not be used, and a joint pretensioned by a method not permitted shall be disassembled and re-installed with new assemblies by a permitted method at the Contractor's expense.

9.2 Pre-Installation Verification

9.2.1 Pre-installation verification shall be performed for every pretensioning method and every fastener lot on the occasions indicated in the datasheet, using a tension calibrator and assemblies from the lot to be installed.
Pre-Installation Verification Occasionsradio
● At the start of work for each lot and whenever the lot, lubrication, equipment, or conditions change, as the RCSC Specification requires
○ At the start of every shift in addition to the occasions the RCSC Specification requires
9.2.2 The verification sample shall consist of not fewer than three complete assemblies of each combination of diameter, length, grade, and lot, and each assembly shall reach not less than 1.05 times the minimum pretension of AISC 360 Table J3.1 by the method to be used in the work.
NOTE Pre-installation verification catches the lot whose lubricant has dried in storage or whose threads have rusted, which reaches the wrench's shut-off or the prescribed rotation without reaching the pretension, before that lot is installed in a structure where the shortfall cannot be seen. (9.2.3)
9.2.4 A lot that fails pre-installation verification shall not be installed, and shall be cleaned and relubricated by a method the manufacturer accepts and re-verified, or removed from the project.
9.2.5 The tension calibrator shall be calibrated within the interval its manufacturer states, and the calibration record shall be available at the site.
9.2.6 Pre-installation verification results shall be recorded by lot, method, and date, and the record shall be available to the quality assurance inspector before the lot is installed.

10 Slip-Critical Faying Surfaces

10.1 Slip Class

NOTE The slip resistance of a slip-critical joint is the product of the bolt pretension and the mean slip coefficient of the faying surface, so the surface class is an input to the connection design and not a finish detail. (10.1.1)
10.1.2 The faying surface slip class for slip-critical connections shall be as indicated in the datasheet.
Slip-Critical Faying Surface Slip Classradio
● Class A
○ Class B
NOTE AISC 360 assigns a mean slip coefficient of 0.30 to Class A and 0.50 to Class B, so a Class B surface carries the same slip load with fewer bolts at the cost of blast cleaning the faying area of every slip-critical joint, and Class A is what an uncoated mill-scale surface or a hot-dip galvanized surface provides without that preparation. (10.1.3)
10.1.4 The slip class selected shall be the class used in the design of every slip-critical connection, and a connection designed for Class B shall not be furnished with a Class A surface.

10.2 Faying Surface Treatment

10.2.1 The treatment of slip-critical faying surfaces shall be as indicated in the datasheet.
Slip-Critical Faying Surface Treatmentselect
Unpainted clean mill scale
Unpainted blast-cleaned steel
Blast-cleaned steel coated with a coating qualified for the slip class
Hot-dip galvanized and roughened by hand wire brushing
10.2.2 The treatment selected shall provide the slip class selected in the datasheet, and a coating applied to a slip-critical faying surface shall carry a slip-class qualification under the RCSC Specification for the class selected, at the dry film thickness within which that qualification holds.
10.2.3 Where a coated treatment is selected, the coating type and the dry film thickness applied at each slip-critical joint shall be recorded in the faying surface verification record.
10.2.4 Where a hot-dip galvanized treatment is selected, the faying surfaces shall be roughened by hand wire brushing after galvanizing and shall not be power wire brushed, because power brushing polishes the zinc and reduces the slip coefficient below the class assigned to the surface.
10.2.5 A slip-critical faying surface shall be free of oil, wax, dirt, loose scale, loose rust, and coating overspray at assembly, and a surface contaminated after treatment shall be re-treated before the plies are brought together.
10.2.6 Whether slip-critical faying areas are masked during shop coating shall be as indicated in the datasheet.
Faying Surface Masking During Shop Coatingradio
○ Faying areas masked before shop coating is applied
○ Faying areas coated with the qualified shop coating
Derived — the slip-critical faying surface treatment selected and whether the shop coating specified in the structural steel framing standard is qualified for the selected slip class (by default)
10.2.7 The masking boundary at each slip-critical joint shall match the connection geometry on the approved connection shop drawings.
10.2.8 Field touch-up coating applied to connections under Structural Steel FramingStructural Steel FramingResolves to the current adopted revision.sync/structural-steel-framing shall not be applied inside the faying area of a slip-critical joint before the joint is assembled.
10.2.9 Where the faying surface of a slip-critical joint must be protected from corrosion across a shipping or storage interval, the protection shall be a coating qualified for the slip class, and no other coating, oil, or wax shall be applied to the faying area.

11 Bolt Holes

11.1 The hole types permitted in bolted connections shall be as indicated in the datasheet.
Hole Types Permitted in Bolted Connectionscheckbox
Any of:
☑ Standard holes
☐ Oversized holes
☐ Short-slotted holes
☐ Long-slotted holes
11.2 Hole dimensions for each hole type shall conform to AISC 360 Table J3.3 for the bolt diameter.
NOTE Oversized and slotted holes buy erection adjustment or accommodate movement, and they buy it by giving up bearing reliability, which is why AISC 360 permits oversized holes and slots parallel to the load only in slip-critical joints. (11.3)
11.4 Oversized holes shall be used only in slip-critical connections, in accordance with AISC 360 Section J3.2.
11.5 Slotted holes with the slot parallel to the direction of load shall be used only in slip-critical connections, and slotted holes in a bearing connection shall have the slot perpendicular to the direction of load.
11.6 Where a bolt passes through an oversized or slotted hole in an outer ply, a hardened washer or plate washer of the size the RCSC Specification requires shall be placed over the hole so that the nut or head bears on solid material.
11.7 The hole type at any connection where a hole type other than standard is used shall be as indicated on the connection details.
11.8 Edge distances, end distances, and bolt spacing shall conform to AISC 360 Sections J3.3 through J3.5 and shall be as indicated on the connection details.
NOTE Hole forming by punching, drilling, or sub-punching and reaming is a fabrication requirement governed by Structural Steel FramingStructural Steel FramingResolves to the current adopted revision.sync/structural-steel-framing, which also requires drilled or reamed holes where the connection is subject to fatigue or is in the seismic force-resisting system. (11.9)
11.10 Where the connected members are hot-dip galvanized, zinc build-up in the holes shall be removed after galvanizing so that the bolt passes freely, and the hole shall not be enlarged beyond the dimension AISC 360 Table J3.3 permits for its type.
11.11 A hole that is misaligned at erection shall be reamed to the next larger hole type only where that type is permitted for the joint condition, and shall not be corrected by drifting that distorts the metal, by flame cutting, or by welding and redrilling without the Engineer of Record's written approval.

12 Bolt Installation

12.1 Washers

12.1.1 Hardened washers shall be provided at the positions indicated in the datasheet, in addition to any washer the RCSC Specification requires for the bolt grade, hole type, or pretensioning method.
Hardened Washer Policyradio
● Hardened washers where the RCSC Specification requires them
○ Hardened washer under the turned element at every pretensioned bolt
○ Hardened washers under both the head and the nut at every high-strength bolt
NOTE The RCSC Specification requires a hardened washer under the turned element where pretension is developed by calibrated wrench or twist-off bolt, under both the head and the nut for Grade A490 bolts in material below a stated yield strength, over oversized and slotted holes in outer plies, and beneath a direct tension indicator where the indicator is at the turned element. (12.1.2)
12.1.3 Beveled washers shall be used where the bearing face of a ply is sloped more than 1:20 from perpendicular to the bolt axis, so that the nut or head bears evenly.
12.1.4 Where a direct tension indicator is used, it shall be placed at the position and with the hardened washer that the RCSC Specification requires for whether the head or the nut is turned.

12.2 Snugging and Pretensioning Sequence

12.2.1 High-strength bolts shall be installed in accordance with the RCSC Specification.
12.2.2 Before any bolt is snugged, the plies shall be assembled with the faying surfaces in the condition this standard requires and with every bolt in the joint installed and finger-tight.
12.2.3 All bolts in a joint shall be brought to snug-tight, working systematically from the most rigid part of the joint toward its free edges, before any bolt in the joint is pretensioned.
NOTE Snug-tight is the condition reached by the full effort of an ironworker on an ordinary spud wrench or by a few impacts of an impact wrench, and it is a ply condition rather than a bolt condition: it means the plies are in firm contact throughout the joint. (12.2.4)
12.2.5 After the whole joint is snug, the bolts shall be pretensioned in the same systematic pattern, and pretensioning shall not begin at the free edge.
NOTE Pretensioning a bolt while adjacent plies are still gapped lets the plies close as later bolts are tightened, relaxing the pretension in the bolts already tensioned and leaving them below the minimum without any change the installer can see. (12.2.6)
12.2.7 A bolt shall be pretensioned by turning the nut or the head with the other element held from rotating, and the element turned shall be the one the pre-installation verification tested.
12.2.8 Where the turn-of-nut method is used, the nut and the protruding bolt end shall be matchmarked at snug and the marks left in place for inspection.
12.2.9 Where the calibrated wrench method is used, the wrench shall be recalibrated on the tension calibrator at the start of each shift and whenever the lot, the bolt diameter or length, the lubrication, or the wrench changes.
12.2.10 Where twist-off bolts are used, the splined end shall shear during the pretensioning pass, and a bolt whose spline sheared during snugging shall be removed and replaced.
12.2.11 Where direct tension indicators are used, the gap shall be checked with the feeler gauge the indicator manufacturer specifies, and an indicator whose protrusions were flattened before pretensioning shall be removed and replaced with the bolt.

12.3 Re-Use and Replacement

12.3.1 A high-strength bolt that has been pretensioned shall not be re-used, and a bolt that has been loosened after pretensioning, that fails inspection, or whose spline sheared during snugging shall be removed and replaced with a new assembly from a verified lot.
NOTE Touching up a bolt, meaning re-tightening a bolt that has relaxed because adjacent bolts were tightened after it, is permitted within a joint before the joint is accepted and is not re-use. (12.3.2)
12.3.3 Where the joint condition or the method requires it, a joint disassembled after pretensioning shall be re-installed entirely with new assemblies.

13 Welded Connection Configurations

13.1 Weld Types and Sizes

13.1.1 The weld type, size, and length at each connection shall be as indicated on the connection details.
NOTE Welding procedure, welder qualification, filler metals, preheat, weld acceptance, and nondestructive examination for connection welds are governed by Welding RequirementsWelding RequirementsResolves to the current adopted revision.sync/welding-requirements; this section governs only the connection-specific configuration of backing, weld tabs, access holes, and the welds particular to each connection class. (13.1.2)
13.1.3 Fillet welds shall not be intermittent on a member subject to fatigue or within a protected zone.
13.1.4 A complete-joint-penetration groove weld loaded in tension transverse to its axis, such as a beam flange welded to a column flange, shall be detailed with the weld access hole, backing, and root treatment this standard requires, because that configuration concentrates through-thickness strain in the column material and is the one most exposed to lamellar tearing.
13.1.5 A partial-joint-penetration groove weld in a column splice shall be used only where the splice carries compression across the weld throat under every load combination, unless the Engineer of Record has verified the tension capacity of the partial throat and shown the required effective throat on the connection details.
13.1.6 Where a column splice is subject to net tension under any load combination, the splice welds shall be complete-joint-penetration groove welds or the splice shall be bolted, as indicated on the column splice details.

13.2 Backing at Beam-to-Column Flange Welds

NOTE Steel backing left at the root of a complete-joint-penetration flange weld leaves a notch at the weld root, and the bottom flange is the flange where that notch sits in the region of greatest inelastic strain in a moment frame beam and cannot be reached to reinforce it from above. (13.2.1)
13.2.2 The disposition of steel backing at the bottom flange of complete-joint-penetration beam-to-column flange welds shall be as indicated in the datasheet.
Bottom-Flange Backing at CJP Beam-to-Column Flange Weldsradio
○ Removed, root back-gouged to sound metal, and reinforced with a fillet weld
○ Left in place and attached to the column flange with a continuous fillet weld
○ Left in place unattached
13.2.3 The disposition of steel backing at the top flange of complete-joint-penetration beam-to-column flange welds shall be as indicated in the datasheet.
Top-Flange Backing at CJP Beam-to-Column Flange Weldsradio
○ Removed, root back-gouged to sound metal, and reinforced with a fillet weld
○ Left in place and attached to the column flange with a continuous fillet weld
○ Left in place unattached
13.2.5 Where AISC 341 applies, the backing at demand-critical beam-to-column flange welds shall be disposed of as AWS D1.8 and the AISC 358 connection require, and the datasheet selection shall not be used to relax that requirement.
13.2.6 Where backing is removed, the root shall be back-gouged to sound metal, examined for defects, and rewelded with a reinforcing fillet of the size shown on the connection details.
13.2.7 Where backing is left in place and attached with a fillet weld, the fillet shall be continuous along the backing and shall be made with a filler metal of the toughness the connection weld requires.
13.2.8 Where backing is left in place unattached, the backing shall be continuous for the full length of the joint and shall be fit tight against the base metal.

13.3 Weld Tabs

NOTE Weld tabs extend the groove beyond the ends of the joint so that the starts and stops of each pass fall outside the connection, and the tab region is where the weld carries the arc-start defects that removal takes away with it. (13.3.1)
13.3.2 The removal of weld tabs at complete-joint-penetration groove welds shall be as indicated in the datasheet.
Weld Tab Removal at CJP Groove Weldsradio
○ Removed and the weld ends ground smooth at every complete-joint-penetration groove weld
● Removed where AWS D1.1, AWS D1.8, or the connection detail requires
13.3.3 Where weld tabs are removed, the weld ends shall be finished to the profile and surface condition AWS D1.1 requires, without gouging the base metal.
13.3.4 Where AISC 341 applies, weld tabs at demand-critical welds shall be removed and the ends finished as AWS D1.8 requires.

13.4 Weld Access Holes

13.4.1 The geometry of weld access holes at beam copes and at complete-joint-penetration flange welds shall be as indicated in the datasheet.
Weld Access Hole Geometryradio
○ Geometry and surface condition per AWS D1.1
○ Seismic geometry and surface condition per AWS D1.8
○ Geometry specified by the AISC 358 prequalified connection
Derived — the applicability of AISC 341 determined from Seismic Design CategorySeismic Design CategoryParameterEach project supplies its own value.seismic-design-category and the seismic force-resisting system, and the geometry the AISC 358 connection selected requires (by default)
NOTE A rough or sharply radiused access hole is a fracture initiation site at exactly the point where the flange weld ends, which is why the seismic geometry and its surface roughness limit are a qualification condition of the connection and not a workmanship preference. (13.4.2)
13.4.3 Weld access holes shall be free of notches and gouges, and a hole cut outside the geometry or roughness required shall be ground to the required condition or repaired by a procedure the Engineer of Record approves in writing.

13.5 Continuity Plates, Doubler Plates, and Stiffeners

13.5.1 Continuity plates, doubler plates, and stiffeners shall be furnished at the locations and in the thicknesses indicated on the connection details.
13.5.2 Welding of a continuity plate, doubler plate, or stiffener into the k-area of a rolled shape shall be avoided by clipping the plate corner as the connection detail shows, and where such welding is unavoidable the web k-area within 3 in. of the weld shall be inspected for cracks after welding.
NOTE The k-area of a rotary-straightened shape is harder and less tough than the rest of the section, and welding into it has produced cracks in the web that appear only after the weld cools. (13.5.3)

14 Load Sharing Between Bolts and Welds

14.1 Whether bolts and welds may share the same force within a single connection shall be as indicated in the datasheet.
Load Sharing Between Bolts and Weldsradio
● Not permitted
○ Permitted within the limits of AISC 360 Section J1.8
NOTE A weld carries its load at a strain too small for a bearing bolt to develop its full strength, so AISC 360 counts the two as sharing only under the conditions of Section J1.8 and only with the bolts installed and pretensioned before the welds are made. (14.2)
14.3 Where load sharing is permitted, the bolts in the shared joint shall be installed in standard holes or in short slots perpendicular to the direction of load, shall be pretensioned before welding begins, and shall share load only with the welds Section J1.8 permits.
14.4 Where load sharing is not permitted, each force in a connection shall be transmitted by bolts alone or by welds alone, erection bolts in a welded connection shall be treated as fit-up devices, and the weld shall be sized to carry the full force without them.
14.5 Where a bolted connection is altered by welding after the bolts have been pretensioned, the existing bolts may be counted for the loads present at the time of the alteration only as AISC 360 Section J1.8 permits.
14.6 Where AISC 341 applies, bolts and welds shall not share load in any connection of the seismic force-resisting system regardless of the datasheet selection.

15 Bolting Inspection

15.1 Inspection by Joint Condition

15.1.1 Bolting shall be inspected in accordance with AISC 360 Chapter N and the RCSC Specification, with the tasks assigned to quality control and quality assurance as the bolting inspection plan states.
15.1.2 Snug-tight joints shall be verified by observation that every bolt is present, that the plies are in firm contact throughout the joint, and that no nut or head has backed off, with random checking by spud wrench.
15.1.3 Pretensioned and slip-critical joints shall be verified by the quality assurance inspector observing or reviewing the record of the pre-installation verification for the lot and method, and by observing the installation operation to confirm that the joint was snugged throughout before pretensioning and that the pretensioning pass proceeded systematically.
15.1.4 For turn-of-nut, the inspector shall confirm that matchmarks were placed at snug and that the prescribed rotation was achieved; for calibrated wrench, that the wrench was calibrated on the occasions this standard requires; for twist-off bolts, that the spline sheared during the pretensioning pass on every bolt; and for direct tension indicators, that the gap closed to the value the indicator manufacturer specifies.
15.1.5 Slip-critical joints shall additionally be verified by the inspector confirming, before the plies are assembled, that the faying surface treatment matches the treatment selected in the datasheet and that the surface is clean.
15.1.6 In addition to observation, the quality assurance inspector shall individually verify the pretension evidence on the proportion of bolts in each pretensioned and slip-critical joint indicated in the datasheet.
Bolts per Pretensioned Joint Individually Verified After Installationrange
%
102550100
NOTE A value of zero leaves the inspection at the observation basis AISC 360 Chapter N establishes, in which the installation operation is witnessed and no routine per-bolt check follows; a higher value adds a per-bolt check of rotation, spline, or indicator gap on a sample after installation, at the cost of inspection time and of a joint that has to be reopened to inspection after the crew has moved on. (15.1.7)
15.1.8 Where the installation records and the pre-installation verification are in order, arbitration testing of installed bolts is not required; where the inspector and the erector disagree whether a joint reached pretension, the arbitration procedure of the RCSC Specification shall govern, using an inspection wrench calibrated on the tension calibrator with assemblies from the lot in question.
15.1.9 A joint that fails inspection shall be corrected at the Contractor's expense, and the cost of any re-inspection and of any arbitration testing that confirms a deficiency shall be borne by the Contractor.

15.2 Inspection Records

15.2.1 Bolting inspection results shall be recorded by connection, identifying the joint condition, the pretensioning method, the fastener lot, the inspector, the date, and the result.
15.2.2 Rejected bolts and joints shall be entered in the nonconformance log with their disposition and the re-inspection result.

16 Field Modifications

16.1 A connection shall not be cut, drilled, reamed beyond the correction this standard permits, or welded in a manner not shown on the approved connection shop drawings without the Engineer of Record's written approval.
16.2 A field modification made without approval voids the certificate of compliance for the affected connection, and the Contractor shall bear the cost of the engineering review, the corrective work, and the re-inspection the modification requires.
16.3 Where a member does not fit at a connection, the Contractor shall report the misfit to the Engineer of Record with the measured deviation before any correction is made, and shall make only the correction the Engineer of Record approves in writing.

17 Delivery, Storage, and Handling

17.1 High-strength bolt assemblies shall be delivered in the manufacturer's sealed and labeled containers, with each container identifying the lot, grade, type, finish, diameter, length, and the matching nut and washer lots.
17.2 Assemblies shall be stored in a closed, weathertight enclosure off the ground, protected from moisture, dirt, and condensation, and shall remain in their sealed containers until issued for installation.
17.3 Only the quantity of assemblies expected to be installed in one shift shall be issued from protected storage to the work point.
17.4 Assemblies not installed during the shift in which they were issued shall be returned to protected storage at the end of that shift and shall not be left exposed to weather at the work point.
17.5 Lots shall be kept segregated in storage and at the work point so that the lot installed in every connection can be traced to its certification and its pre-installation verification record.
17.6 An assembly that has rusted, whose lubricant has dried, washed off, or been contaminated, or whose container seal was broken for a period long enough to admit moisture shall not be installed until the lot has been re-verified by pre-installation verification or has been cleaned and relubricated by a method the manufacturer accepts and then re-verified.
17.7 Field relubrication of an assembly with a lubricant the manufacturer has not accepted is not permitted, because the pretension the lot's records demonstrate was tested with the manufacturer's lubricant and no other.
17.8 Direct tension indicators shall be stored and handled so that their protrusions are not deformed before installation, and an indicator with a deformed protrusion shall be discarded.
NOTE Welding consumables are received, stored, and controlled under Welding RequirementsWelding RequirementsResolves to the current adopted revision.sync/welding-requirements. (17.9)

18 Warranty

NOTE The connection work is warranted under the warranty Structural Steel FramingStructural Steel FramingResolves to the current adopted revision.sync/structural-steel-framing establishes for the structural steel, for the period and on the terms stated there. (18.1)
18.2 For the purpose of that warranty, a connection defect includes a high-strength bolt found below the minimum pretension its joint condition requires, a slip-critical joint whose faying surface was not treated as this standard requires, a connection whose fastener grade, diameter, hole type, or weld configuration differs from the approved connection shop drawings, and a weld defect in a connection weld that the required inspection should have found.
18.3 A connection found defective within the warranty period shall be corrected by the responsible party at its own expense, including disassembly, new fastener assemblies, re-welding, re-inspection, and restoration of the coating system disturbed by the correction.