1 Scope
NOTE This specification covers the design responsibility, materials, installation, and inspection of the bolted and welded connections that join hot-rolled structural steel framing members into a complete, load-carrying structure. (1.1)
NOTE It is the connection-focused companion to
Structural Steel Framing: the framing standard governs the members, their fabrication, erection, and coatings, while this standard governs how those members are fastened to one another.
(1.2) 1.3The framing standard and this standard shall be read together, and where a requirement appears in both, the more stringent shall govern.
1.4Connections shall conform to ANSI/AISC 360-22 (Specification for Structural Steel Buildings), principally Chapter J (Design of Connections), to ANSI/AISC 303-22 (Code of Standard Practice for Steel Buildings and Bridges) for trade practice and connection-design responsibility, to the RCSC Specification for Structural Joints Using High-Strength Bolts (2020) for all high-strength bolting, and to AWS D1.1:2025 (Structural Welding Code — Steel) for all welding.
1.5Where the project is assigned to Seismic Design Category C, D, E, or F, ANSI/AISC 341-22 (Seismic Provisions) and AWS D1.8:2016 (Seismic Supplement) shall additionally govern connections in the seismic force-resisting system.
NOTE A connection is where the load path is made or broken; the way bolts are pretensioned and verified, faying surfaces are prepared, welds are qualified and inspected, and design responsibility is assigned are treated as load-bearing requirements, not paperwork. (1.6)
NOTE A connection that "looks tight" but was never verified, or a complete-joint-penetration weld that was never ultrasonically tested where the code requires it, is a defective connection regardless of appearance. (1.7)
1.8 Connection Types in Scope
NOTE The connection types within this scope include simple (shear) connections such as shear tabs, double-angle, single-angle, seated, and end-plate shear connections; fully restrained (FR) and partially restrained (PR) moment connections; vertical and horizontal bracing connections and their gusset plates; column splices; column base plate connections (the steel-side bolting and welding, not the concrete anchorage); and the connection elements — angles, tees, plates, stiffeners, and continuity plates — required to complete them. (1.8.1)
1.8.3This standard governs how those connections are made and verified, not which member frames where.
2 Referenced Standards
2.1Connections shall comply with the latest adopted edition of each standard listed below.
2.2Where conflicts exist, the more stringent requirement shall govern unless the Structural Engineer of Record (SER) directs otherwise in writing.
2.3The project structural general notes and connection design basis govern over default assumptions in this specification.
2.4 Standards Reference Table
| Standard |
Title |
| ANSI/AISC 360-22 |
Specification for Structural Steel Buildings (Chapter J — Design of Connections) |
| ANSI/AISC 303-22 |
Code of Standard Practice for Steel Buildings and Bridges |
| ANSI/AISC 341-22 |
Seismic Provisions for Structural Steel Buildings (where applicable) |
| ANSI/AISC 358-22 |
Prequalified Connections for Special and Intermediate Steel Moment Frames for Seismic Applications (where applicable) |
| RCSC 2020 |
Specification for Structural Joints Using High-Strength Bolts |
| AWS D1.1:2025 |
Structural Welding Code — Steel |
| AWS D1.8:2016 |
Structural Welding Code — Seismic Supplement |
| AWS A5-series |
Filler Metal Specifications (electrodes, wires, and fluxes by process) |
| AWS QC1 |
Standard for AWS Certification of Welding Inspectors |
| ASTM F3125/F3125M |
High Strength Structural Bolts and Assemblies (consolidates A325, A490, F1852, F2280) |
| ASTM A563/A563M |
Carbon and Alloy Steel Nuts |
| ASTM F436/F436M |
Hardened Steel Washers |
| ASTM F959/F959M |
Compressible-Washer-Type Direct Tension Indicators for Use with Structural Fasteners |
| ASTM A1085/A1085M |
Cold-Formed Welded Carbon Steel Hollow Structural Sections (HSS) |
| ASTM A6/A6M |
General Requirements for Rolled Structural Steel Bars, Plates, Shapes, and Sheet Piling |
| ASTM A123/A123M |
Zinc (Hot-Dip Galvanized) Coatings on Iron and Steel Products |
| ASTM B695 |
Coatings of Zinc Mechanically Deposited on Iron and Steel |
| ASTM F2329/F2329M |
Zinc Coating, Hot-Dip, Requirements for Application to Carbon and Alloy Steel Bolts |
| AISC G4.2 |
Guidelines for the Qualification of Structural Bolting Inspectors |
| ASNT SNT-TC-1A |
Personnel Qualification and Certification in Nondestructive Testing |
| IBC 2021 |
International Building Code (Chapter 17, Special Inspections and Tests) |
3 Submittals
3.1 Action Submittals
3.1.1The Contractor and fabricator shall submit the following for review by the SER prior to fabricating or installing any connection:
- Connection design calculations, where connection design is delegated to the fabricator, sealed by a licensed structural engineer in the state of the project (see Connection Design below)
- Connection shop drawings showing all connection elements, plate sizes and grades, bolt patterns, hole types and sizes, edge and end distances, gauges, weld symbols, weld sizes, joint geometry, backing and weld-access-hole details, and the faying-surface treatment required at each slip-critical joint
- Welding procedure specifications (WPS) for every welded joint, prequalified or qualified under AWS D1.1:2025, listing the essential variables: base metals and groups, filler metal classification, welding process, position, preheat and interpass temperature, heat input range, and joint geometry
- Procedure qualification records (PQR) supporting each non-prequalified WPS
- Welder and welding operator qualification records per AWS D1.1:2025 Clause 7 (and Clause 8 where applicable), showing process, position, base metal group, and qualification date for each individual
- Bolt assembly certifications and test reports for each lot of high-strength fasteners under ASTM F3125, including the manufacturer's certified mechanical test results and the rotational-capacity (RC) test results for the matched bolt-nut-washer (and DTI where used) assembly per RCSC 2020
- Filler-metal certifications (AWS A5-series) including Charpy V-notch (CVN) toughness data where demand-critical welds are required
- Direct-tension-indicator product data and ASTM F959 conformance, where DTIs are the selected pretensioning method
- Pre-installation verification (PIV) plan describing the tension-measuring device, the verification frequency, and the records to be kept
- Nondestructive examination (NDE) plan identifying methods, extent by weld type and risk category, acceptance criteria, and personnel qualifications
☐ Connection design calculations (where delegated, PE-sealed)
☐ Connection shop drawings (bolt patterns, weld symbols, joint details)
☐ Welding procedure specifications (WPS)
☐ Procedure qualification records (PQR) — non-prequalified WPS
☐ Welder and welding operator qualification records (AWS D1.1 Clause 7)
☐ Bolt assembly certifications and rotational-capacity (RC) test reports (ASTM F3125)
☐ Filler-metal certifications with CVN data where demand-critical
☐ Direct-tension-indicator product data (ASTM F959), if used
☐ Pre-installation verification (PIV) plan
☐ Nondestructive examination (NDE) plan
3.1.2Connection work shall not begin until the corresponding submittals have been reviewed and returned.
3.1.3Submittals shall be coordinated with the member submittals required by Structural Steel Framing so that connection elements, hole patterns, and weld access conditions are consistent with the approved member shop drawings. 3.2 Closeout Submittals
3.2.1At substantial completion, the Contractor shall provide:
- Bolt installation and inspection records, organized by connection, documenting the pretensioning method, the PIV results for each lot and each day, and the inspection results for each pretensioned and slip-critical joint
- Welding inspection records, including the visual inspection report for every weld and the NDE reports (UT, RT, MT, PT as applicable) for every weld subjected to NDE, cross-referenced to weld location and WPS
- A non-conformance and repair log listing every rejected weld or bolt, the disposition, the repair WPS or procedure used, and the re-inspection result
- Certificates of compliance from the fabricator and erector attesting that the connections were made in accordance with the contract documents, RCSC 2020, and AWS D1.1:2025
☐ Bolt installation and inspection records (by connection, with PIV results)
☐ Welding inspection records (visual and NDE reports cross-referenced to WPS)
☐ Non-conformance and repair log (rejections, dispositions, re-inspections)
☐ Certificates of compliance from fabricator and erector (RCSC 2020, AWS D1.1)
4 Quality Assurance
4.1 QC and QA Framework
NOTE Connection quality is governed by AISC 360-22 Chapter N, which separates quality control (QC) — the fabricator's and erector's own internal program — from quality assurance (QA) — the independent verification performed by an inspector retained by or on behalf of the Owner with no financial relationship to the fabricator or erector. (4.1.1)
4.1.2The two functions are distinct; QA inspection does not relieve the fabricator or erector of QC responsibility.
4.1.3The QA plan shall identify each inspection task as Observe (O), performed on a random unannounced basis without delaying production, or Perform (P), carried out for each applicable joint or member, per AISC 360-22 Tables N5.4 and N5.6.
4.2 Fabricator and Erector Certification
NOTE The fabricator and erector qualifications, including AISC certification category, are established in
Structural Steel Framing and are not repeated here.
(4.2.1) 4.2.3Seismic force-resisting connections require, at minimum, an AISC Advanced (ADV) certified fabricator as established in the framing standard.
4.3 Welder Qualification
○ AWS D1.1:2025 Clause 7 (production-weld qualification)
○ AWS D1.1:2025 Clause 7 with CVN toughness testing (seismic demand-critical welds)
4.3.1All welders and welding operators making structural connections shall be qualified under AWS D1.1:2025 Clause 7 for the processes, positions, base metal groups, and joint types they will weld.
4.3.2Welder qualification shall be current and shall not have lapsed by more than six months for a given process.
4.3.3A welder who has not used a process in production for six months or more shall requalify before making production welds.
4.3.4For seismic demand-critical welds, welders shall additionally be qualified on material matching the thickness and joint geometry of the demand-critical joint using the specific approved WPS.
4.4 Inspection Personnel
☐ AWS Certified Welding Inspector (CWI) per AWS QC1 — welding inspection
☐ Bolting inspector qualified per AISC G4.2 — high-strength bolting
☐ ASNT SNT-TC-1A Level II for each NDE method used (UT/RT/MT/PT)
4.4.1Welding QA inspection shall be performed by an AWS Certified Welding Inspector (CWI) per AWS QC1, or by an inspector working under the direct supervision of a CWI.
4.4.2Bolting QA inspectors shall be qualified per AISC G4.2.
4.4.3NDE technicians shall be qualified per ASNT SNT-TC-1A, with Level II the minimum for independent evaluation of UT, RT, MT, and PT results.
4.4.4Level I personnel may perform tests only under Level II supervision and shall not independently evaluate results.
4.4.5A CWI qualification covers visual inspection but does not by itself qualify a person to perform or evaluate UT, RT, MT, or PT; separate ASNT method qualification is required for each.
5 Environmental and Service Conditions
5.1 Seismic Design Category
NOTE The Seismic Design Category (SDC) determines whether the seismic provisions of AISC 341-22 and AWS D1.8:2016 apply to the connections of the seismic force-resisting system. (5.1.1)
A or B — no special seismic connection requirements
C — intermediate detailing for designated systems, consult SER
D, E, or F — full AISC 341-22 / AWS D1.8 connection requirements apply
NOTE In SDC A and B there are generally no special seismic connection requirements. (5.1.2)
5.1.3In SDC C, intermediate detailing may apply to designated systems.
5.1.4In SDC D, E, and F, demand-critical welds, protected zones, prequalified moment connections per AISC 358-22, and the enhanced bolting and inspection requirements of AISC 341-22 shall apply to all elements of the seismic force-resisting system.
5.2 Service Environment
NOTE The corrosion environment of the connection determines the fastener finish and the faying-surface and coating provisions. (5.2.1)
Interior, dry, conditioned — plain (black) bolts, no special corrosion measures
Exposed/exterior or high humidity — galvanized fasteners on galvanized steel
Aggressive industrial or coastal — galvanized fasteners, qualified faying-surface coating
5.2.2Interior, dry, conditioned connections use plain (black) bolts and require no special corrosion measures.
5.2.3Connections exposed to weather, high humidity, or aggressive industrial atmospheres shall use galvanized fasteners compatible with galvanized members, and the faying-surface and slip-class provisions shall account for the coating.
5.2.4The connection corrosion environment shall be coordinated with the member coating system established in Structural Steel Framing. 6 Bolted Connections
6.1 Bolt Assemblies
NOTE ASTM F3125 is the consolidated specification that replaced the legacy A325, A325M, A490, A490M, F1852, and F2280 standards; it covers heat-treated structural bolts in two strength grades and two styles (hex-head and the twist-off tension-control style). (6.1.1)
ASTM F3125 Grade A325 (120 ksi minimum tensile strength)
ASTM F3125 Grade A490 (150 ksi minimum tensile strength)
Plain (black, uncoated) — interior/dry, standard
Mechanically galvanized (ASTM B695 Class 50) — A325 or A490
Hot-dip galvanized (ASTM F2329) — A325 only
5/8 in.
3/4 in.
7/8 in.
1 in.
1-1/8 in.
1-1/4 in.
NOTE Grade A325 (120 ksi minimum tensile strength) is the standard for the great majority of structural connections. (6.1.2)
NOTE Grade A490 (150 ksi minimum tensile strength) is specified where the higher per-bolt shear and tension capacity is needed to fit the required force into the available bolt count or gauge. (6.1.3)
6.1.4Grade A490 bolts shall not be hot-dip galvanized, because high-strength steel of A490 hardness is susceptible to hydrogen embrittlement during pickling and galvanizing and ASTM F3125 prohibits it.
6.1.5A high-strength bolt shall be supplied and installed as a matched assembly — bolt, nut, and washer (and DTI where used) from the same production lot, lubricated and rotational-capacity tested together.
NOTE Mixing components from different lots, substituting a non-lubricated or differently lubricated nut, or re-using a fastener that has already been pretensioned invalidates the certification. (6.1.6)
6.1.7Nuts shall conform to ASTM A563 and washers to ASTM F436.
6.1.8Galvanized nuts shall be overtapped to clear the zinc thickness on the bolt threads, and a standard nut shall not be forced onto a galvanized bolt.
6.2 Connection Joint Type
NOTE RCSC 2020 and AISC 360-22 Section J3 recognize three joint conditions: snug-tight, pretensioned, and slip-critical. (6.2.1)
Snug-tight — bearing connections not subject to fatigue, tension, or seismic demand
Pretensioned — full pretension required, faying surface not slip-critical
Slip-critical — full pretension plus verified faying-surface slip resistance
NOTE A snug-tight joint brings the plies into firm contact by the full effort of an ironworker on a spud wrench or a few impacts of an impact wrench. (6.2.2)
6.2.3A snug-tight joint is adequate only for ordinary bearing-type connections in static shear that are not subject to fatigue, do not carry significant tension, and are not part of the seismic force-resisting system.
6.2.4A pretensioned joint shall develop the minimum bolt pretension of AISC 360-22 Table J3.1 but does not require any particular faying-surface condition.
6.2.5A slip-critical joint shall develop the minimum pretension and additionally rely on the friction (slip resistance) between prepared faying surfaces so that the joint does not slip into bearing under service load.
6.2.6Pretensioned installation is required by RCSC 2020 and AISC 360-22 for connections subject to cyclic or fatigue loading; connections using A490 bolts in tension or combined shear and tension; connections in the seismic force-resisting system per AISC 341-22; column splices in buildings over 125 ft tall per AISC 360-22 Section J3.1; column base plate connections; and any connection the SER has explicitly designated for pretensioning.
6.2.7The SER shall designate pretensioned and slip-critical connections on the contract drawings, and the fabricator shall not downgrade a designated joint to snug-tight.
6.3 Pretensioning Methods
6.3.1The four RCSC pretensioning methods each achieve the minimum pretension of AISC 360-22 Table J3.1 by a different mechanism, and any may be used on a given project subject to approval in the submittal.
Turn-of-nut method (RCSC 2020 §8.2.1)
Calibrated wrench method (RCSC 2020 §8.2.2)
Twist-off tension-control (TC) bolt assemblies (RCSC 2020 §8.2.3)
Direct-tension-indicator (DTI) washers per ASTM F959 (RCSC 2020 §8.2.4)
○ Per RCSC 2020 Table 8.1 (rotation by bolt length and faying-surface slope)
NOTE Turn-of-nut: the bolts are first brought to snug, the nut and protruding bolt end are matchmarked, and the nut is turned a specified additional rotation (one-third, one-half, or two-thirds turn per RCSC 2020 Table 8.1) that strains the bolt into the inelastic range where pretension is insensitive to the exact rotation. (6.3.2)
NOTE Calibrated wrench: the installation wrench is calibrated each shift on a tension-measuring device (a Skidmore-Wilhelm or equivalent) using bolts from the lot in use, so the wrench shut-off or applied torque corresponds to the minimum pretension under that day's lubrication and thread condition. (6.3.3)
NOTE Twist-off (TC) bolts: a splined tip beyond the threaded length shears off at a calibrated torque, giving a visible, no-measurement confirmation that the assembly reached pretension. (6.3.4)
NOTE DTI washers: a compressible washer with formed protrusions flattens as the bolt is tensioned, and a feeler gauge confirms the gap has closed to the specified dimension, indicating the bolt reached minimum pretension. (6.3.5)
6.4 Pre-Installation Verification
○ Required each shift and on any lot/lube/condition change, tension-measuring device (standard)
○ Required at project start only (not permitted for slip-critical or seismic)
6.4.1Pre-installation verification (PIV) shall be performed at the start of each day's bolting and whenever the lot, lubrication, weather, or equipment changes, for all pretensioned and slip-critical joints.
6.4.2A representative sample of the complete assembly being installed that day shall be tested in a tension-measuring device to confirm that the chosen installation method, with that specific lot and its as-delivered lubrication, develops at least 1.05 times the minimum required pretension before installation begins.
NOTE PIV catches a lot that has lost its lubricant in storage or has rusted threads — which will not develop pretension at the expected torque or rotation — before hundreds of under-tensioned bolts are placed. (6.4.3)
6.5 Faying Surfaces — Slip-Critical Connections
NOTE The slip resistance of a slip-critical joint is the product of the bolt pretension and the mean slip coefficient (mu) of the faying surface; the surface class therefore enters directly into the connection design. (6.5.1)
Class A (mean slip coefficient mu = 0.30) — clean mill scale or Class A qualified coating
Class B (mean slip coefficient mu = 0.50) — blast-cleaned bare steel or Class B qualified coating
○ Uncoated (clean mill scale for Class A, or blast-cleaned bare steel for Class B)
○ Coating with documented Class A or Class B qualification per RCSC 2020 Appendix A
NOTE Class A surfaces (mu = 0.30) comprise unpainted clean mill-scale steel or steel blast-cleaned and coated with a coating qualified as Class A. (6.5.2)
NOTE Class B surfaces (mu = 0.50) comprise unpainted blast-cleaned bare steel or steel coated with a Class-B-qualified coating; the higher coefficient can reduce the number of bolts but requires blast cleaning of the faying area. (6.5.3)
6.5.4A faying surface in the slip-critical zone shall not be coated with an ordinary shop primer unless that primer has been tested and qualified for a slip class under RCSC 2020 Appendix A.
6.5.5Where corrosion protection of the faying area is required during a long shipping interval, only a coating with a documented Class A or Class B qualification shall be used, applied at the qualified dry film thickness, and the type and thickness shall be recorded.
6.5.6Oil, wax, dirt, and overspray on the faying surface destroy slip resistance and shall be prevented, and the faying area shall be masked during shop priming where the primer is not qualified.
6.6 Bolt Holes
NOTE Standard round holes are the default; oversized and slotted holes provide erection adjustment or accommodate thermal movement but reduce the bearing reliability of the joint, so their use carries restrictions under AISC 360-22 Section J3.2. (6.6.1)
○ Standard round holes (STD) — nominal bolt diameter plus 1/16 in. (per AISC 360-22 Table J3.3)
○ Oversized holes (OVS) — per AISC 360-22 Table J3.3 (slip-critical only)
○ Short-slotted holes (SSL) — per AISC 360-22 Table J3.3
○ Long-slotted holes (LSL) — per AISC 360-22 Table J3.3
6.6.2Oversized holes are permitted only in slip-critical connections.
6.6.3Slotted holes are restricted in orientation relative to the load and may require plate washers or hardened washers to bridge the slot.
6.6.5For connections subject to fatigue or designated as seismic, holes shall be drilled or sub-punched and reamed to remove the cold-worked edge.
6.7 Bolt Installation
Per RCSC 2020 (position-dependent by grade, hole type, and method) — standard
ASTM F436 hardened washer under turned element at all pretensioned bolts
ASTM F436 hardened washers under both head and nut at all locations
6.7.1All bolts shall be installed per RCSC 2020.
6.7.2Plies shall be brought into firm contact before pretensioning, working systematically from the most rigid part of the joint toward the free edges so that the plies seat fully and no gaps remain.
6.7.3All bolts in a connection shall be brought to snug-tight first, and only after the entire connection is snug shall the pretensioning operation proceed, in the same systematic pattern.
NOTE This two-pass sequence prevents pretensioning a bolt while adjacent plies are still gapped, which would relax the bolts already tensioned and leave them below the minimum. (6.7.4)
6.7.5Beveled (wedge) washers shall be used where the bearing face is sloped more than 1:20 from perpendicular to the bolt axis, such as on the flanges of American Standard channels and S-shapes, so that the nut bears evenly.
6.7.6Hardened ASTM F436 washers shall be provided as required by RCSC 2020 for the bolt grade, hole type, and pretensioning method — at minimum under the turned element for pretensioned and slip-critical joints, and under both head and nut for A490.
6.8 Bolt Inspection
○ Per AISC 360-22 Table N5.6 (observe PIV and installation; verify per method)
○ Verify rotation/spline/DTI gap on a minimum of 10% of bolts per connection
6.8.1Snug-tight joints shall be verified by visual inspection for the presence of all bolts and firm ply contact, with random spot-checking by spud wrench.
6.8.2Pretensioned and slip-critical joints shall be inspected per AISC 360-22 Table N5.6 and RCSC 2020 Section 9, with the QA inspector observing or documenting the PIV and then observing the installation operation.
6.8.3For turn-of-nut, the inspector shall confirm that matchmarks were placed at snug and that the specified rotation was achieved.
6.8.4For TC bolts, the inspector shall confirm that the splines have sheared on all bolts.
6.8.5For DTIs, the inspector shall verify the feeler-gauge gap on a sample of the DTIs.
6.8.6Slip-critical joints additionally require documentation that the faying-surface condition was verified before assembly.
6.8.7Where the installation method's records are in order, arbitration testing per RCSC 2020 is not required; where a question arises, the arbitration procedure governs.
6.8.8A bolt that has been pretensioned and then loosened, or that fails inspection, shall be removed and replaced with a new assembly, and high-strength bolts shall not be re-used.
7 Welded Connections
FCAW-G (Flux-Cored Arc Welding — Gas-Shielded)
FCAW-S (Flux-Cored Arc Welding — Self-Shielded)
SMAW (Shielded Metal Arc Welding)
SAW (Submerged Arc Welding) — shop, flat position
GMAW (Gas Metal Arc Welding)
Multiple processes per approved WPS
7.1.1Welding consumables shall conform to the applicable AWS A5-series specification and shall be selected to match the base metal group and the preheat and interpass requirements of the WPS.
7.1.2Filler metals shall meet the matching-strength requirement of AWS D1.1:2025 for the base metal; overmatching strength filler is permitted only where the WPS and the SER allow it.
7.1.3Low-hydrogen consumables (H8 or lower diffusible-hydrogen designation) shall be used for all structural welding to control hydrogen cracking.
7.1.4Where demand-critical welds are required by AISC 341-22, the filler metal shall additionally meet the CVN toughness requirements of AWS D1.8:2016 — a minimum of 20 ft-lb at minus 20 degrees F (and the supplemental toughness at the higher test temperature where required).
7.1.5Self-shielded FCAW (FCAW-S) shall not be used for demand-critical welds.
7.1.6Low-hydrogen SMAW electrodes and fluxes shall be stored and handled per the AWS A5-series and the manufacturer's instructions, and electrodes exposed beyond the permitted atmospheric window shall be redried or discarded.
7.2 Weld Types and Joint Configurations
☐ Fillet welds
☐ Complete-joint-penetration (CJP) groove welds
☐ Partial-joint-penetration (PJP) groove welds
☐ Plug or slot welds
☐ Flare-bevel/flare-V groove welds (to HSS and rounded edges)
Per AWS D1.1:2025 Table 7.7 (based on thickness of thicker part joined)
3/16 in. minimum all locations
1/4 in. minimum all locations
NOTE Fillet welds are the workhorse of steel connections — economical, requiring no joint preparation, and used wherever a lap or tee joint can develop the force in shear along the weld throat. (7.2.2)
NOTE Complete-joint-penetration (CJP) groove welds fuse the full thickness of the joint and develop the full strength of the connected material; they are reserved for the highest-demand joints such as moment-connection beam flanges to columns and heavy column splices, and require edge preparation, fit-up, and usually backing. (7.2.3)
NOTE Partial-joint-penetration (PJP) groove welds develop a defined partial throat and are used where full strength is not required, such as some column splices in compression. (7.2.4)
7.2.5CJP groove welds loaded in tension transverse to the weld shall be detailed with appropriate weld-access holes, backing, and — where the SER requires it — through-thickness material with verified properties, because this configuration is the most susceptible to lamellar tearing in the through-thickness direction.
NOTE The minimum fillet weld size of AWS D1.1:2025 Table 7.7, keyed to the thickness of the thicker part joined, is a metallurgical minimum independent of the calculated demand and prevents the thick material from drawing heat out of a small weld so fast that the weld metal cools into a hard, crack-prone microstructure. (7.2.6)
7.2.7The maximum fillet size along an edge is limited so that the full throat is developed.
7.2.8Intermittent fillet welds shall not be used on members subject to fatigue or within protected zones designated under AISC 341-22.
7.3 Weld Access Holes and Backing
○ Leave backing in place (non-seismic, where permitted by detail)
○ Remove bottom-flange backing, back-gouge and reinforce; fillet-weld top-flange backing (seismic, AWS D1.8)
7.3.1Weld access holes (rat holes) at beam copes and at CJP groove welds shall be detailed and finished to the geometry and surface-roughness requirements of AWS D1.1:2025.
7.3.2In seismic applications the special access-hole geometry of AWS D1.8:2016 shall apply, because a poorly shaped or rough access hole is a fracture initiation site under cyclic demand.
7.3.3Steel backing left in place at CJP welds at moment connections, and weld tabs (run-off tabs), shall be handled per the contract details.
NOTE For seismic demand-critical beam-flange welds, bottom-flange backing is typically removed and the root back-gouged and rewelded with a reinforcing fillet, and top-flange backing is fillet-welded to the column, all per AWS D1.8:2016. (7.3.4)
7.3.5Weld tabs shall be removed and the ends finished where required by AWS D1.1:2025 or the drawings.
7.4 Preheat and Interpass Temperature
○ Temperature-indicating crayons (Tempilstik or equivalent)
○ Contact pyrometer (surface thermometer)
○ Infrared thermometer
7.4.1Preheat and interpass temperatures shall comply with AWS D1.1:2025 Table 5.3 for prequalified WPS, or with the qualified WPS where more stringent.
NOTE Preheat slows the cooling rate of the weld and surrounding heat-affected zone, allowing diffusible hydrogen to escape and preventing the hard, crack-susceptible microstructure that causes delayed hydrogen (underbead) cracking, most critical in thick material, high-restraint joints, higher-carbon-equivalent steels, and cold ambient conditions. (7.4.2)
7.4.3Preheat shall be verified before arc initiation and interpass temperature between passes using a calibrated contact pyrometer or temperature-indicating crayons, and the verification shall be documented.
7.4.4The minimum base-metal temperature for welding shall not be below the AWS D1.1:2025 limit (generally 0 degrees F), the surface shall be dry, and the joint shall be shielded from wind that would disturb the arc shielding gas.
7.5 Weld Inspection and NDE
Ultrasonic testing (UT) per AWS D1.1:2025
Radiographic testing (RT) per AWS D1.1:2025
UT primary, RT where geometry prevents effective UT
Ultrasonic testing (UT) per AWS D1.1:2025
Magnetic particle testing (MT) — surface and near-surface confirmation
UT primary, MT for surface indications
Per AISC 360-22 Table N5.4 (risk-category-based minimum)
25% of CJP groove welds in tension (Risk Category II minimum)
100% of CJP groove welds in tension (Risk Category III/IV)
○ 100% UT and 100% visual of all demand-critical CJP welds (AISC 341-22 / AWS D1.8)
7.5.1All welds shall be visually inspected per AWS D1.1:2025 Clause 8, performed on 100 percent of welds.
NOTE Visual testing is the first and most cost-effective inspection, catching insufficient size, undercut, overlap, porosity, improper profile, incomplete fusion at the toes, and surface cracks before any volumetric NDE is undertaken. (7.5.2)
7.5.3QC visual inspection is performed by the fabricator's or erector's inspector; QA visual inspection is performed by the Owner's independent CWI.
7.5.4Acceptance criteria for statically and cyclically loaded connections shall be those of AWS D1.1:2025 Clause 8.
7.5.5Volumetric and surface NDE beyond visual shall be performed by method, weld type, and extent per AISC 360-22 Table N5.4 and the project NDE plan.
NOTE Ultrasonic testing (UT) is the preferred volumetric method for CJP groove welds — portable, needing no radiation exclusion zone, and detecting internal planar flaws (cracks, incomplete fusion) and volumetric flaws (porosity, slag) throughout the weld volume. (7.5.6)
7.5.7The UT operator shall be qualified per AWS D1.1:2025 and shall distinguish rejectable planar discontinuities from acceptable volumetric ones.
NOTE Radiographic testing (RT) gives a permanent film record but requires radiation control and is generally limited to geometries where UT scanning is impractical. (7.5.8)
NOTE Magnetic particle testing (MT) is a surface and near-surface method used to confirm freedom from surface and shallow subsurface cracks, particularly on fillet welds, on PJP welds, and on accessible welds in seismic applications. (7.5.9)
NOTE Penetrant testing (PT) detects surface-breaking discontinuities where MT is not applicable. (7.5.10)
7.5.11Per AISC 360-22 Table N5.4, the minimum UT rate for Risk Category II buildings is 10 percent of CJP groove welds in compression and 25 percent of CJP groove welds in tension.
7.5.12For Risk Category III and IV (essential and substantial-hazard facilities) the UT rate increases to 100 percent of CJP groove welds in tension.
7.5.13The SER may specify higher NDE rates for critical connections regardless of risk category.
7.5.14Welds rejected by NDE shall be repaired per a repair WPS and re-inspected by the same method that found the defect, and the repair and re-inspection shall be entered in the non-conformance log.
8 Connection Design
8.1 Design Responsibility and Delegation
NOTE Connection design responsibility is established by AISC 303-22. (8.1.1)
○ Connections fully detailed on contract drawings — no delegation
○ Simple shear connections delegated to fabricator (forces shown on drawings)
○ Moment connections delegated to fabricator (forces and rotation demands shown)
○ All connections delegated to fabricator (all design forces shown on drawings)
8.1.2The contract documents shall make clear, for each connection, whether the SER has fully detailed the connection on the drawings or has delegated its design to the fabricator's engineer.
8.1.3Where design is delegated, the contract drawings shall show the required forces, moments, and any rotation or ductility demands for each connection type.
8.1.4Where design is delegated, the fabricator's engineer — a structural engineer licensed in the state of the project — shall design the connection geometry to satisfy those demands and seal the calculations.
NOTE The SER's review of the delegated submittal confirms that the connections meet the stated contract demands and does not transfer the detailed-design responsibility back to the SER. (8.1.5)
8.1.6This division of responsibility is a defined provision of AISC 303-22 and shall be stated explicitly so that no connection is left with ambiguous design authorship.
8.2 Minimum Forces and Connection Types
☐ Simple (shear) — shear tab, double-angle, single-angle, seated, shear end-plate
☐ Fully restrained (FR) moment connections
☐ Partially restrained (PR) moment connections
☐ Bracing / gusset-plate connections
☐ Column splices
☐ Column base plate connections (steel side)
8.2.1Every connection shall develop the forces shown on the contract drawings.
8.2.2Where a connection force is not shown, the connection shall be designed for the minimum-force provisions of AISC 360-22 Section J1.
8.2.4The schedule shall identify which connections are simple (shear), which are moment (FR or PR), which are bracing, and which are slip-critical, so that the correct bolting and welding requirements of this standard are applied to each.
8.3 Seismic Connections
○ Not applicable — non-seismic or SDC A/B
○ Prequalified connection per AISC 358-22
○ Connection qualified by cyclic testing per AISC 341-22
8.3.1Where the project is in SDC D, E, or F, or where the SER designates seismic systems in lower SDCs, connections in the seismic force-resisting system shall conform to AISC 341-22.
8.3.2Seismic moment connections shall be prequalified connections per AISC 358-22 or shall be qualified by testing.
8.3.3Protected zones — regions of expected plastic hinging designated on the drawings — shall not be drilled, punched, coped, notched, or have attachments welded to them without the SER's written approval, because any such stress raiser can nucleate fracture during cyclic earthquake demand.
8.3.4Demand-critical welds shall meet the filler-metal toughness, access-hole, backing, and 100 percent NDE requirements set out above.
9 Surface Preparation and Coatings Interface
NOTE The surface preparation, shop primer, galvanizing, and field touch-up of the steel are governed by
Structural Steel Framing; this section addresses only where coatings and the connection work intersect.
(9.1) ○ Mask slip-critical faying areas before priming (primer not slip-qualified) — standard
○ No masking required (faying-area primer is Class A or B qualified)
9.2The faying surfaces of slip-critical joints shall be prepared to the slip class specified above and shall be masked off during shop priming unless the primer is qualified for the slip class.
9.3The masking shall be coordinated with the shop coating operation so that the qualified-coating boundary matches the connection geometry on the shop drawings.
9.4Field welds, the heat-affected zone alongside them, bolt heads and nuts, and any field-cut or field-drilled surfaces shall be cleaned and touched up to restore the shop coating system per the framing standard within the time limit it sets.
9.5Faying surfaces shall never receive field touch-up coating inside the slip-critical zone.
9.6Where members are hot-dip galvanized per ASTM A123, bolt holes shall be reamed to restore clearance after galvanizing, and only A325 (not A490) galvanized bolts shall be used.
10 Installation and Erection Sequencing
○ Per AISC 360-22 Section J1.8 (sequence so bolts and welds share load as designed)
○ As specifically detailed on the connection drawing
10.1Connection work in the field shall follow the erection sequence and stability plan required by Structural Steel Framing. 10.2Within each connection, bolts shall be brought to snug-tight and then pretensioned in the systematic pattern described above.
10.3A member shall not be released from the crane until it is connected and braced sufficiently to be stable on its own, and single-bolt pickup connections shall not be relied on for stability.
10.4Field welding shall be performed only by currently qualified welders using approved WPS, after the joint is fitted, aligned, and (where applicable) bolted in its erection bolts, and only when the base-metal temperature, surface dryness, and wind conditions satisfy AWS D1.1:2025.
10.5Where a connection combines bolts and welds sharing the same force, the installation sequence shall follow AISC 360-22 Section J1.8 so that the bolts and welds share load as the design assumes — generally the bolts are snugged, the welds completed, and the bolts then pretensioned, unless the connection detail directs otherwise.
10.6Field modifications to connections — cutting, drilling, or welding not on the approved drawings — shall not be performed without the SER's written approval, and unauthorized field modification voids the affected member's certifications.
11 Delivery, Storage, and Handling of Fasteners and Consumables
11.1 Fastener Delivery and Storage
☐ Store as sealed, labeled matched lots protected from moisture and dirt
☐ Issue only the shift's quantity to the work point; return unused to protected storage
☐ Keep lots segregated and traceable to certification and PIV records
☐ Do not field re-lubricate; re-verify by PIV or discard if lubricant lost
☐ Protect DTI protrusions from deformation before installation
11.1.1High-strength bolt assemblies shall be delivered and stored as matched lots, in their sealed and labeled containers, protected from dirt, moisture, and loss of the manufacturer-applied lubricant.
11.1.2A fastener that has rusted, dried out, or been re-lubricated in the field with an unqualified lubricant shall be re-verified by PIV or discarded, because the lubricant is part of the certified assembly.
11.1.3Only the quantity of fasteners expected to be installed in a work shift shall be taken from protected storage to the work point.
11.1.4Assemblies not installed that shift shall be returned to protected storage and shall not be left exposed to the weather.
11.1.5Lots shall be kept segregated and identifiable so that the lot installed in any connection can be traced to its certification and PIV record.
11.1.6DTIs shall be stored so their protrusions are not deformed before installation.
11.2 Consumable Storage
☐ Store per AWS A5-series and manufacturer instructions
☐ Hold low-hydrogen SMAW electrodes / SAW flux in heated ovens; redry per manufacturer
☐ Discard consumables showing moisture, rust, or damage
☐ Protect FCAW/GMAW wire from moisture and contamination
11.2.1Welding consumables shall be stored and handled per the AWS A5-series and the manufacturer's instructions.
11.2.2Low-hydrogen SMAW electrodes and SAW fluxes shall be kept in heated holding ovens and redried per the manufacturer where they have been exposed beyond the permitted atmospheric exposure window.
11.2.3Consumables that show signs of moisture pickup, damage, or rust shall not be used.
11.2.4FCAW and GMAW wire spools shall be protected from moisture and contamination.
12 Warranty
1 year from substantial completion
2 years from substantial completion
12.1The fabricator shall warrant the shop connection work and the erector shall warrant the field connection work against defects in materials and workmanship for a period of not less than one year from substantial completion, or for the period stated in the contract documents if longer.
12.2The warranty shall cover under-tensioned or improperly installed high-strength bolts, weld defects not detected during the required inspection and NDE, incorrect connection geometry or fastener grade, and connection distress that becomes apparent under load.
12.3Connections found defective within the warranty period shall be corrected at the responsible party's expense, including any disassembly, refastening, re-welding, re-inspection, and coating restoration required.
NOTE The warranty does not cover damage caused by other trades, loading beyond the design basis, modifications by others after completion of the steel work, or corrosion of fasteners or welds that results from failure to maintain the coating system. (12.4)