This specification covers the materials, fabrication, erection, inspection, and coating of hot-rolled structural steel framing systems for buildings and structures. The structural steel work shall conform to ANSI/AISC 360-22 (Specification for Structural Steel Buildings), ANSI/AISC 303-22 (Code of Standard Practice for Steel Buildings and Bridges), and AWS D1.1:2025 (Structural Welding Code — Steel) as the primary governing standards for design basis, trade practice, and welding, respectively. Where projects are assigned to Seismic Design Category C, D, E, or F, ANSI/AISC 341-22 (Seismic Provisions for Structural Steel Buildings) shall additionally govern all elements of the seismic force-resisting system.
Structural steel under this specification includes all members shown on the structural drawings as part of the gravity-load-carrying and lateral force-resisting systems: wide-flange beams, girders, and columns; hollow structural sections (HSS) used as columns, braces, or beams; channels, angles, tees, and plates; base plates, bearing plates, and column cap plates; headed shear stud connectors for composite beams; gusset plates, stiffeners, and connection plates; and all bolts, nuts, washers, welds, and anchor rods required to form a complete, structurally sound framing system.
Member sizes, connection types, connection details, and overall framing geometry are as indicated on the structural framing plans, elevations, sections, and connection detail sheets. This specification governs how the steel is procured, fabricated, erected, inspected, and coated; the structural contract drawings define what is built and where. The two documents shall be read together. In the event of a conflict between this specification and the structural drawings, the more stringent requirement governs; the Structural Engineer of Record (SER) shall resolve genuine conflicts in writing.
This specification does not cover steel deck, which is addressed in Steel Deck. Concrete placement at composite slab systems, anchor rod embedment, and footing requirements are addressed in Cast In Place Concrete and Concrete Reinforcement. Spray-applied fireproofing applied to structural steel members is addressed in Fireproofing. Structural steel connections to masonry bearing walls shall be coordinated with Unit Masonry.
Materials, fabrication, and erection shall comply with the latest adopted edition of each standard listed below. Where conflicts exist between referenced standards, the more stringent requirement shall govern unless the SER directs otherwise in writing. The project's structural general notes and connection design basis govern over default assumptions in this specification.
| Standard | Title |
|---|---|
| ANSI/AISC 360-22 | Specification for Structural Steel Buildings |
| 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) |
| AISC Design Guide 1 | Base Plate and Anchor Rod Design (Second Edition) |
| AWS D1.1:2025 | Structural Welding Code — Steel |
| AWS D1.8:2016 | Structural Welding Code — Seismic Supplement |
| RCSC 2020 | Specification for Structural Joints Using High-Strength Bolts |
| ASTM A6/A6M-24 | General Requirements for Rolled Structural Steel Bars, Plates, Shapes, and Sheet Piling |
| ASTM A36/A36M | Carbon Structural Steel |
| ASTM A572/A572M | High-Strength Low-Alloy Columbium-Vanadium Structural Steel |
| ASTM A992/A992M | Structural Steel Shapes |
| ASTM A500/A500M-23 | Cold-Formed Welded and Seamless Carbon Steel Structural Tubing in Rounds and Shapes |
| ASTM A1085/A1085M-22 | Cold-Formed Welded Carbon Steel Hollow Structural Sections (HSS) |
| ASTM A529/A529M | High-Strength Carbon-Manganese Steel of Structural Quality |
| ASTM A913/A913M | High-Strength Low-Alloy Steel Shapes of Structural Quality, Produced by Quenching and Self-Tempering Process |
| ASTM F3125/F3125M | High Strength Structural Bolts and Assemblies |
| ASTM A307 | Carbon Steel Bolts, Studs, and Threaded Rod 60,000 PSI Tensile Strength |
| ASTM A563 | 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 |
| ASTM F1554-20 | Anchor Bolts, Steel, 36, 55, and 105-ksi Yield Strength |
| ASTM A108 | Steel Bar, Carbon and Alloy, Cold-Finished |
| 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 | Zinc Coating, Hot-Dip, Requirements for Application to Carbon and Alloy Steel Bolts |
| ASCE 7-22 | Minimum Design Loads and Associated Criteria for Buildings and Other Structures |
| IBC 2021 | International Building Code (Chapter 17, Special Inspections and Tests) |
| AMPP SP 2 (SSPC-SP 2) | Hand Tool Cleaning |
| AMPP SP 3 (SSPC-SP 3) | Power Tool Cleaning |
| AMPP SP 6 (SSPC-SP 6) | Commercial Blast Cleaning |
| AMPP SP 10 (SSPC-SP 10) | Near-White Metal Blast Cleaning |
| AMPP PA 1 (SSPC-PA 1) | Shop, Field, and Maintenance Painting of Steel |
| ASNT SNT-TC-1A | Personnel Qualification and Certification in Nondestructive Testing |
The fabricator shall submit the following for review by the SER and Architect of Record prior to commencing fabrication. Fabrication shall not begin on any members, connection elements, or assemblies until the corresponding submittals have been reviewed and returned. The Contractor shall allow a minimum of 15 working days for each review cycle.
Shop drawings shall be prepared by the fabricator in accordance with AISC 303-22 Section 4. Shop drawings shall show all member designations, sizes, cross-sections, lengths, connection details, bolt patterns and hole types, weld symbols and sizes, cope dimensions, block cuts, cambered members and camber amounts, erection marks, piece marks, and the project north orientation. Shop drawings shall not be reproductions or tracings of the structural contract drawings; they represent the fabricator's independent detailed interpretation of the design. This distinction protects the SER's design responsibility and is non-negotiable.
Erection drawings shall show the erection sequence, planned crane locations and pick sequences where relevant to the stability of incomplete frames, and the required temporary shoring and bracing scheme. The erection plan is a safety and stability document that confirms the erector has thought through the sequence before arriving at the site.
Welding procedure specifications (WPS) shall be submitted for all welded connections, covering both prequalified and non-prequalified procedures under AWS D1.1:2025. Each WPS shall include the essential variables: base metals, filler metal classification, welding process, position, preheat and interpass temperature, heat input range, and joint geometry. Procedure qualification records (PQR) shall accompany non-prequalified WPS. WPS shall be available at the work location during fabrication.
Welder qualification records shall document that each welder and welding operator has been qualified per AWS D1.1:2025 Clause 7 (or Clause 8 where applicable) for the processes, positions, and joint types they will perform. Records shall show qualification date, process, position, and base metal group. The Contractor shall ensure all qualification records are current and shall remove any welder whose qualification has lapsed.
Certified mill test reports (CMTR) shall be submitted for all structural steel shapes, plates, bars, and tubing. CMTRs shall be traceable to specific heat and lot numbers corresponding to the material delivered to the project and shall confirm compliance with the applicable ASTM specification, including mechanical properties, chemical composition, and carbon equivalent where required. CMTRs are the project's primary evidence that the specified grade was actually delivered.
Bolt lot certifications shall be submitted for each lot of high-strength bolts, nuts, and washers conforming to ASTM F3125. Certifications shall confirm the lot number, the grade, the mechanical test results, and where applicable, the results of rotational-capacity (RC) testing per the RCSC 2020 Specification. Bolts, nuts, and washers shall be submitted as complete matched assemblies from the same lot.
Fabricator AISC certification documentation shall be submitted and shall be current at the time of submittal. Certification shall remain current throughout the fabrication period; lapse shall be reported to the SER immediately.
Connection design calculations shall be submitted where connection design is delegated to the fabricator, as described in the Delegated Design section below.
Shop and field coating product data sheets and application procedures shall be submitted for all coating systems, including surface preparation requirements, application method, wet and dry film thickness per coat, total dry film thickness, and recoat windows.
Where connection design is delegated to the fabricator, the contract drawings shall show the required connection forces, moments, and performance criteria for each connection type, and the fabricator's engineer of record shall design the connection geometry to satisfy those demands. Connection calculations shall be prepared by a licensed structural engineer in the state of the project and retained by the fabricator. Delegated design calculations and drawings shall be submitted with the shop drawings for review by the SER. The SER's review confirms that the delegated connections meet the contract force requirements; the fabricator's engineer retains responsibility for the detailed design.
At substantial completion, the Contractor shall provide:
AISC 360-22 Chapter N establishes the minimum requirements for quality control (QC), quality assurance (QA), and nondestructive testing of structural steel. QC is the fabricator's and erector's own internal program for meeting the requirements of the contract. QA is the independent verification of the QC program, performed by an inspector retained by or on behalf of the Owner and having no financial relationship with the fabricator or erector. These two functions are separate and shall not be conflated; QA inspection does not relieve the fabricator or erector of QC responsibility.
AISC 360-22 Chapter N distinguishes two levels of inspector activity: Observe (O) tasks, which inspectors perform on a random, unannounced basis and do not delay operations pending inspection, and Perform (P) tasks, which are carried out for each welded joint, bolted connection, or member as required. The QA inspection plan shall identify which tasks are Observe and which are Perform, consistent with AISC 360-22 Tables N5.4-1, N5.4-2, N5.4-3, N5.6-1, N5.6-2, and N5.6-3.
Special inspections of structural steel construction shall be performed in accordance with IBC 2021 Chapter 17, Section 1705.2 and Table 1705.2. The Statement of Special Inspections (SSI) prepared by the SER shall list all required special inspection tasks and the applicable inspection frequency (continuous or periodic). The Special Inspector shall be engaged by the Owner and shall report deficiencies directly to the SER and the Authority Having Jurisdiction (AHJ). Special inspection is required for the following categories under IBC 1705.2:
AISC fabricator certification, administered under AISC 207 (Standard for Certification Programs), requires an independent third-party audit of the fabricator's quality management system, personnel, equipment, and shop practices. Standard (STD) certification covers typical commercial building projects with standard connections. Intermediate (INT) certification is appropriate where connections involve heavier members, more complex detailing, or seismic systems in moderate seismic zones. Advanced (ADV) certification is required where seismic special moment frames, eccentrically braced frames, or buckling-restrained braced frames are specified. Complex (CPX) certification is reserved for long-span, high-rise, or architecturally complex projects with demanding tolerances. The SER shall select the appropriate category based on the project's structural complexity, not simply on size.
The fabricator shall maintain current AISC certification for the full duration of fabrication. If certification lapses or is suspended, the fabricator shall notify the Owner, SER, and Architect immediately and shall not continue fabrication until certification is reinstated or an alternative quality assurance program approved by the SER is in place.
The erector shall demonstrate the experience, equipment, and personnel to safely and accurately erect the steel framing shown on the contract drawings. AISC erector certification covers the erector's safety program, site planning, and hoisting operations. For projects with complex geometry, tall structures, or critical erection sequencing, ACSE certification or equivalent experience documentation shall be required. The erector's superintendent shall have a minimum of five years of structural steel erection experience on projects of comparable scope.
All welders and welding operators performing structural steel work shall be qualified under AWS D1.1:2025 Clause 7 for the specific welding processes, positions, base metal groups, and joint types they will perform. Qualification shall be current and shall not have lapsed by more than six months. Welders who have not continuously welded with a specific process for six months or more shall re-qualify under AWS D1.1:2025 before performing production work. The fabricator and erector shall each maintain a log of all qualified welders, their processes, positions, and qualification expiration dates, and shall make the log available to the QA inspector upon request.
For projects with seismic demand-critical welds per AISC 341-22, welders performing those welds shall demonstrate qualification on material matching the thickness and joint geometry of the demand-critical joints, using the specific approved WPS.
QA inspectors shall be AWS Certified Welding Inspectors (CWI) per AWS QC1 or shall hold equivalent qualification documented to the satisfaction of the SER. NDT technicians shall be qualified per ASNT SNT-TC-1A at the appropriate level (Level II minimum for independent evaluation). QA inspection firms shall have no business, financial, or organizational relationship with the fabricator or erector.
ASTM A992 is the standard specification for wide-flange shapes in the United States and is used for essentially all W-section beams, girders, and columns in commercial construction. A992 provides three critical properties that distinguish it from older specifications: a minimum yield-to-tensile ratio of Fu/Fy ≥ 1.18 (ensuring the material can strain-harden before fracture), a maximum yield-to-tensile ratio of Fy/Fu ≤ 0.85 (preventing shapes with extremely high, unpredictable yield strength), and a maximum carbon equivalent (CE ≤ 0.45 for Groups 1–3, ≤ 0.47 for Groups 4–5) to ensure reliable weldability. These controls are essential for predictable connection behavior and for seismic performance; ASTM A36 and ASTM A572 Grade 50 W-shapes shall not be substituted for A992 shapes without the SER's written approval.
ASTM A913 shapes are produced by the quenching and self-tempering (QST) process, which achieves higher strength and toughness in large shapes without the penalty in weldability that normally accompanies high-strength steel. A913 Grade 50 or 65 shapes are specified where heavy column sections (W14×257 and heavier or Group 4 and 5 shapes) require enhanced through-thickness toughness, where high seismic demands per AISC 341-22 require Charpy V-notch (CVN) toughness for demand-critical members, or where the structural engineer requires Grade 65 or 70 to reduce member size in heavily loaded columns.
ASTM A500/A500M Grade C is the standard specification for cold-formed welded and seamless HSS (both rectangular and round). Grade C provides 50 ksi minimum yield and is preferred over Grade B because Grade B offers no procurement cost advantage while providing lower strength. One persistent issue with A500 is wall thickness tolerance: the standard permits wall thickness to be as much as 10% below the nominal dimension. In calculations for connection strength — particularly for welded connections to HSS walls or for local wall yielding — designers and fabricators shall apply the appropriate thickness reduction factor (typically 0.93 of nominal) per AISC 360-22.
ASTM A1085 is a newer specification that closes the tolerance gap: wall thickness tolerance is tightened to −5% (not −10%), a maximum mass tolerance of −3.5% is added, and an upper bound on yield strength of 70 ksi is imposed to ensure ductile connection behavior. A1085 is recommended for concentrically braced frames, eccentrically braced frames, and other seismic applications per AISC 341-22 where HSS members serve as primary structural elements, because the tighter tolerances eliminate the need for the 0.93 wall thickness reduction factor and the bounded yield strength improves connection ductility prediction. A1085 is also appropriate for architecturally exposed HSS where dimensional precision is required.
ASTM A36 is the standard specification for channels, angles, and miscellaneous shapes used in secondary framing, bracing, and kicker connections. A572 Grade 50 is specified where secondary member sizes must be minimized or where the SER has noted specific higher-strength requirements on the drawings.
ASTM A36 plate is the standard for shear tabs, gusset plates, stiffeners, column base plates, bearing plates, and similar connection elements. A36's relatively low yield strength is an intentional design choice for many connection configurations: a "softer" plate yields predictably before fracture and accommodates deformation demands that would be better handled at the plate than at the weld or bolt. Substituting A572 Grade 50 plate for A36 without the SER's written approval can shift the failure mode of the connection and may not be conservative. The SER shall explicitly note on the contract drawings where higher-strength plate is required.
ASTM F3125 is the consolidated specification for high-strength structural bolts, which superseded the legacy ASTM A325 and A490 individual standards. Grade A325 (120 ksi minimum tensile strength for bolt diameters ≤1 in., 105 ksi for larger diameters) is the standard for the majority of structural steel connections in commercial buildings. Grade A490 (150 ksi minimum tensile strength) is specified where bolt count or gauge distances limit the number of fasteners that can fit in a connection and the higher bolt shear and tension capacity of A490 resolves the constraint. Grade A490 bolts shall not be galvanized; the hot-dip galvanizing process can induce hydrogen embrittlement in high-strength steel, and ASTM F3125 explicitly prohibits galvanizing of A490.
Plain (black) bolts shall be used on the majority of projects. Galvanized bolts shall be used where the connected structural steel is hot-dip galvanized. When galvanized bolts are specified, the bolts, nuts, and washers shall be from the same lot and shall be furnished as matched assemblies that have been rotational-capacity tested per RCSC 2020 Section 2.3.3. Galvanized nuts shall be overtapped to accommodate the zinc coating thickness; standard nuts shall not be used on galvanized bolts.
ASTM F1554 is the standard specification for anchor rods and covers three yield strength grades. Grade 36 is the standard for column base plate anchor rods in most commercial buildings; it provides adequate strength for typical gravity and wind-driven overturning loads, is readily available, and is compatible with standard hook embedment configurations. Grade 55 includes an optional weldability supplement (Supplement S1) that shall be specified when anchor rods must be welded; without the weldability supplement, Grade 55 is not reliably weldable. Grade 105 is used where high tensile demand, large diameter rods, or seismic overturning moments require higher strength; its high strength and hardness make it unsuitable for bending and it shall not be used where 90-degree hooks are required. Anchor rod grades shall be color-coded at the projecting end: blue for Grade 36, yellow for Grade 55, red for Grade 105.
Anchor rod sizes, diameters, embedment depths, projection lengths, spacing, and group locations are as indicated on the structural foundation plans and anchor rod setting plans. Anchor rod placement templates shall be furnished by the fabricator and used by the concrete subcontractor when setting rods; see Cast In Place Concrete for concrete placement and anchor rod tolerance requirements.
Welding electrodes, wires, and fluxes shall comply with AWS D1.1:2025 and shall be selected to match the base metal group and the minimum preheat and interpass temperature requirements of the WPS. Filler metals shall meet the matching strength requirements of AWS D1.1:2025 for the applicable base metal; overmatching strength filler metals may be used only where the WPS and the SER permit them. Low-hydrogen electrodes (H8 or lower designation) shall be used for all structural welding. Filler metal packaging shall be in accordance with AWS A5-series storage requirements; opened packages of low-hydrogen SMAW electrodes shall be kept in portable electrode ovens or redried before use if exposed to ambient humidity for more than the manufacturer's stated window.
FCAW-G (gas-shielded flux cored arc welding) is the most widely used process for structural steel fabrication and field welding because it combines high deposition rates, all-position capability, and tolerance of the steel surfaces encountered in structural work. FCAW-S (self-shielded) is used in field conditions where wind disrupts external gas shielding, but the SER should be aware that self-shielded FCAW is generally prohibited for demand-critical welds in seismic applications per AWS D1.8. SMAW remains common for field welding, repairs, and in positions where continuous wire-feed processes are impractical. SAW is used in the shop for long flat-position welds such as beam flange-to-column flange connections and built-up member assembly because it produces excellent weld quality at very high deposition rates. GMAW requires a stable, shielded shop environment and is less common for structural steel than for light fabrication.
Shear stud connectors shall conform to ASTM A108 and shall be welded per AWS D1.1:2025 Clause 9 using a stud welding process qualified for the steel deck profile and base metal conditions present. Shear stud quantity, layout, minimum and maximum spacing, edge distances, and deck orientation requirements are as indicated on the composite beam schedules and framing plans. Studs shall be tested after welding by the bend test per AWS D1.1:2025 Clause 9.8.1; studs that do not meet visual inspection criteria shall be bent to 90 degrees for further evaluation. Where stud heads are found to be off-center or weld flash is irregular, additional studs shall be added adjacent to the defective stud rather than attempting to remove and re-weld the original.
All connections shall develop the forces shown on the contract drawings. Where forces are not shown for a connection, the connection shall be designed for the minimum design force requirements of AISC 360-22 Section J1.4. Connections shown only schematically on the contract drawings (standard connections) shall be designed by the fabricator's engineer where connection design is delegated, as described in the Submittals section.
Snug-tight installation, as defined by RCSC 2020, is the condition achieved when all plies of a connection are in firm contact and each bolt has been tightened by a few impacts of an impact wrench or the full effort of a worker using an ordinary spud wrench. Snug-tight is the minimum condition for all bearing-type connections not subject to fatigue, tension loads, or seismic force-resisting system requirements. Confirming snug-tight is accomplished by visual inspection and random checking with a spud wrench; it does not require instrumented verification.
Pretensioned installation is required where the RCSC 2020 or AISC 360-22 mandates it, and shall be specified for the following connection conditions:
Each pretensioning method achieves the minimum bolt tensions specified in AISC 360-22 Table J3.1 through a different mechanism. Turn-of-nut: bolts are brought to snug, matchmarked between nut and connected ply, then turned an additional specified rotation (1/3, 1/2, or 2/3 turn depending on bolt length and slope of faying surfaces per RCSC 2020 Table 8.2); mean pretension achieved is approximately 1.35 times the minimum for A325 bolts. Calibrated wrench: an impact or torque wrench is calibrated on a bolt tension calibrator (such as a Skidmore-Wilhelm device) at the start of each shift using bolts from the same lot; calibration accounts for daily variation in bolt lubrication and thread condition. TC bolts (twist-off type): tightening ceases when the spline on the bolt end shears off, providing a visual, no-measurement confirmation of installation. DTI washers: the washer squeezes as the bolt is tightened; a calibrated feeler gauge verifies that the gap has closed to the specified dimension, confirming that the bolt has reached minimum pretension. Any method may be used on a given project; the method shall be selected by the erector and approved in the submittal process.
Pre-installation verification (PIV) shall be performed at the start of each day's bolting operations for pretensioned and slip-critical connections, using a Skidmore-Wilhelm or equivalent tension-measuring device and bolts from the same lot being used that day. PIV confirms that the installation method and the specific bolt lot will achieve minimum pretension under field conditions; lube condition, temperature, and thread quality all affect pretension for methods that rely on torque.
Slip-critical connections are required where bolt slip under service loads would cause unacceptable deformation, where bolts are installed in oversized or slotted holes, where the connection is subject to load reversal (net tension), or where the connection is part of a seismic force-resisting system that requires slip resistance to meet drift or ductility limits. The SER shall designate slip-critical connections on the contract drawings. A slip-critical designation requires pretensioned bolt installation and a verified faying surface condition.
The faying surface class is determined by the coefficient of slip resistance (μ) used in the connection design. Class B surfaces (μ = 0.50) allow higher slip resistance and can reduce the number of bolts, but require blast cleaning of the faying surface area before assembly. If shop primer is applied to the faying surface area, the primer must be specifically qualified as a Class A or Class B coating per RCSC 2020 Appendix A; most shop primers are qualified Class A. The faying surface shall not be painted with a standard shop primer in the slip-critical zone unless the primer is RCSC-approved for the applicable class. Contamination of the faying surface with oil, wax, or dirt before assembly reduces slip resistance and shall be prevented.
Standard round holes are the default for all connections. Oversized and slotted holes accommodate erection tolerances or allow for thermal movement in connections subject to temperature cycles; their use requires slip-critical connection design. Long-slotted holes provide greater erection adjustment range but further restrict their use per AISC 360-22 Section J3.2.
Punching is economical and fast but leaves a cold-worked zone around the hole that can reduce ductility in fatigue applications and seismic demand-critical regions. In connections that are part of a seismic force-resisting system, or where the connection is designated as subject to fatigue, holes shall be drilled or sub-punched and reamed to final diameter to remove the cold-worked material at the hole edge.
All welding shall be performed per AWS D1.1:2025 using approved WPS. The WPS is the governing document for each weld; the welder or welding operator shall have a copy of the applicable WPS at the workstation and shall follow it precisely, including preheat and interpass temperature requirements. Deviation from the WPS essential variables without authorization constitutes a non-conformance requiring the SER's review.
CJP groove welds are the highest-demand weld type and require full fusion through the entire joint thickness. They are used in moment connection beam flanges, heavy column splices, and other connections where full strength must be developed across the joint. CJP groove welds loaded in tension transverse to the weld axis are the welds most susceptible to lamellar tearing in the connected material and shall be designed with appropriate backing and access details.
Preheat and interpass temperatures shall comply with AWS D1.1:2025 Table 5.3 (prequalified WPS) or the qualified WPS, whichever is more stringent. Preheat is required to prevent hydrogen cracking (underbead cracking) in higher-carbon-equivalent base metals and under conditions of high restraint, thick material, or low ambient temperature. Minimum preheat temperatures per AWS D1.1:2025 are based on the carbon equivalent of the base metal, the material thickness, and the welding process. The Contractor shall have calibrated contact pyrometers or thermal pencils on site and shall verify and document preheat prior to arc initiation and interpass temperature between passes.
Minimum fillet weld size per AWS D1.1:2025 Table 7.7 is based on the thickness of the thicker part being joined and is set to prevent rapid cooling that produces hard, brittle weld metal. Fillet weld sizes, lengths, and locations are as shown on the structural connection details. Intermittent fillet welds shall not be used on members subject to fatigue loading or in protected zones per AISC 341-22.
Where the project is assigned to Seismic Design Category D, E, or F, or where the SER has designated seismic force-resisting system connections in lower SDCs, demand-critical welds shall comply with AISC 341-22 and AWS D1.8:2016.
For SDC D through F, demand-critical welds shall be made with filler metals meeting CVN toughness of 20 ft-lb at −20°F per AWS D1.8:2016. FCAW-S (self-shielded flux cored arc welding) shall not be used for demand-critical welds. Protected zones designated on the structural drawings are regions of expected plastic hinging and shall not be drilled, punched, coped, notched, or welded for attachments of any kind without written approval from the SER. Protected zones are particularly sensitive to stress concentrations that would nucleate fracture during earthquake loading.
All high-strength bolts shall be installed in accordance with RCSC 2020. Prior to installation, the Contractor shall confirm that the bolts, nuts, and washers are from the same matched assembly lot and have not been mixed with components from other lots. Components shall be free of dirt, oil other than manufacturer's applied lubrication, and burrs that would prevent solid seating of plies.
Connections shall be assembled progressively from the most rigid point outward to draw the plies into firm contact before pretensioning begins. Finger-tightening all bolts before any are brought to snug ensures that plies are fully in contact before the load sequence starts and prevents bolt cross-threading.
RCSC 2020 specifies washer requirements based on bolt grade, hole type, and connection condition. As a baseline, hardened washers are required under the turned element (nut or bolt head, depending on which is turned) for all pretensioned and slip-critical connections, and under both head and nut for Grade A490 bolts. Beveled washers (wedge washers) shall be used where bearing surfaces are sloped more than 1:20 from perpendicular to the bolt axis.
Snug-tight connections shall be verified by the QA inspector through visual inspection and random spot-checking with a spud wrench. Inspectors shall verify that all bolts are present, that plies are in firm contact, and that bolt heads or nuts have not backed off.
Pretensioned connections shall be inspected by witnessing or reviewing documented evidence of the pre-installation verification and the actual installation operation for each bolt group. For turn-of-nut installations, the QA inspector shall verify matchmarks have been placed at snug and that the specified rotation has been achieved for at least 10% of bolts in each connection. For TC bolt installations, the inspector shall verify that splines have sheared on all bolts. For DTI installations, the inspector shall verify feeler-gauge gap readings on a minimum of 10% of DTIs. Rejected bolts shall be replaced; they shall not be re-used.
Fabrication shall conform to AISC 303-22 and AISC 360-22 Chapter M. Members shall be fabricated to the dimensions and details shown on the approved shop drawings, within the tolerances of ASTM A6/A6M-24 (rolling tolerances) and AISC 303-22 (fabrication tolerances). Any departure from the approved shop drawings constitutes a non-conformance and shall be brought to the SER's attention; the fabricator shall not proceed with non-conforming work without written direction.
Thermal cutting (oxy-fuel and plasma) and mechanical cutting (sawing and shearing) are acceptable cutting methods. Thermally cut edges that are subject to calculated tensile stress or that will receive welding shall be ground smooth and free of notches, gouges, and slag to a surface roughness not exceeding 1000 μin (ANSI/ASME B46.1) per AWS D1.1:2025. Reentrant corners shall have a minimum radius of 3/8 in. to prevent notch-initiated fracture at stress concentrations.
Shearing is permitted for material up to 5/8 in. thick for plates and 3/4 in. thick for angles and channels when the sheared edge will not be subject to calculated tensile stress and is not part of a connection designated as seismic.
Heat straightening of distorted members is permitted within the limits of AISC 303-22 provided that temperatures do not exceed 1,200°F for A36 and A572 steel or 1,100°F for A992 steel, as measured by calibrated contact pyrometer or thermal crayon. Repeated heating of the same location shall be avoided. Heat straightening shall not be performed on members that have been hot-dip galvanized.
Where camber is indicated on the structural drawings, members shall be cambered to the dimensions shown within the fabrication tolerances of AISC 303-22 (typically ±1/4 in. for beams up to 50 ft, proportionally larger for longer spans, per AISC 303-22 Section 6.4). Camber is intended to compensate for dead load deflection so that the floor surface is level after dead loads are applied. The net dead load camber value shown on the drawings represents the SER's calculation of the expected dead load deflection, and the fabricator shall camber to that value.
The practical minimum camber for hot-rolled beams is approximately 3/4 in.; specifying less than 3/4 in. camber typically results in the fabricator ignoring the requirement or cambering to the minimum practical value, generating a non-conformance. The SER shall review camber requirements before issuing drawings. Members not indicated for camber shall be fabricated so that any incidental camber is upward (arch up) after erection.
Camber amounts are as noted on the structural framing plans and beam/girder schedules.
Every member shall be clearly and durably marked with its erection mark (also called the piece mark) using paint stick, die stamp, or stencil. Erection marks shall match those shown on the approved erection drawings. For members where the top or bottom orientation must be maintained in the field, the mark shall indicate the required orientation. Members that are part of a seismic force-resisting system shall be identified as such on the erection drawings so that special inspection requirements are correctly applied in the field.
AMPP SP 6 (Commercial Blast Cleaning) is the standard minimum surface preparation for shop-primed structural steel. It removes all visible oil, grease, dust, mill scale, rust, and paint, permitting random staining on no more than 33% of any 9 in.² area. SP 6 is adequate for standard alkyd and epoxy primer systems applied in sheltered, protected environments. AMPP SP 10 (Near-White Metal Blast Cleaning) removes all visible contaminants except light shadows, streaks, and slight discolorations on no more than 5% of the surface; it is required for high-performance epoxy and zinc-rich primer systems, for steel in exposed or exterior applications, and for galvanizing preparation. AMPP SP 2 (Hand Tool Cleaning) is the minimum for steel that will be fully concealed within the building envelope and will receive spray-applied fireproofing; it is not adequate for any coated, exposed, or galvanized steel.
The shop coating decision is driven by the final service environment and what system will be applied in the field. Steel destined to receive spray-applied cementitious or intumescent fireproofing shall receive no shop primer unless the fireproofing manufacturer has tested and certified adhesion over the specific primer at the proposed DFT; most cementitious fireproofing products require clean, bare steel for adequate bond. See Fireproofing for fireproofing bond strength and adhesion testing requirements.
Steel to be hot-dip galvanized shall be prepared per AMPP SP 10 or by the galvanizer's standard acid-pickling process. Galvanizing shall conform to ASTM A123; minimum average coating thickness requirements depend on the steel category (structural shapes, plates, and bar stock) per ASTM A123 Table 1. Galvanized bolt holes shall be reamed or re-tapped after galvanizing to restore the clearance required for bolt installation; the reaming operation is the fabricator's responsibility.
Zinc-rich primer provides galvanic (cathodic) protection of the base steel and is specified for steel in moderately aggressive environments, steel in semi-exposed locations, and steel where the field paint system is expected to be less than continuous. Inorganic zinc-rich primers require blast-cleaned surfaces to provide the metallic zinc-to-steel contact needed for galvanic protection; they are not applicable over previously primed or contaminated surfaces.
Faying surfaces of slip-critical connections shall receive the surface treatment corresponding to the specified slip coefficient class. Standard shop primer shall be masked off or left unpainted on faying surfaces unless the primer is RCSC-approved for the applicable slip class. Where coating of the faying surface is unavoidable (e.g., for corrosion protection during a long shipping interval), only approved Class A or Class B primers shall be used, and the type and DFT shall be recorded and submitted for the SER's review.
AESS requirements per AISC 303-22 Section 10 impose progressively more stringent standards for weld appearance, surface finish, flatness, spatter removal, and dimensional tolerances as the category increases. AESS adds meaningful cost — Category 2 typically adds 15–25% to fabrication cost of affected members; Category 3 and 4 add more. The SER and Architect shall explicitly identify which members are AESS and which category applies on the contract drawings, and this designation shall be made early enough to be incorporated into the bid documents. Specifying AESS after contract award creates scope disputes and schedule impacts.
All field welds, bolt heads and nuts, areas where shop coating was damaged during shipping or erection, and field-cut or field-drilled surfaces shall be cleaned to a minimum of AMPP SP 2 and coated with the field touch-up coating material within 24 hours of exposure. Touch-up shall restore the full dry film thickness of the shop coating system.
Before erecting any steel, the erector shall survey all anchor rod groups and verify that installed positions are within the tolerances of AISC 303-22 Section 7.5. Anchor rod tolerance limits per AISC 303-22 are: ±1/8 in. between anchor rods within a group (pattern tolerance), and ±1/4 in. between groups of anchor rods (grid tolerance). Anchor rod projection tolerance (height above concrete) is ±3/8 in. These tolerances exist because base plate holes have limited clearance and because anchor rod misalignment is one of the most common field conditions that generates RFIs and construction delays.
Anchor rods found to be out of tolerance shall be reported to the SER before steel is erected. The SER shall evaluate the deviation and direct the correction. Acceptable corrections include enlarging base plate holes (subject to bearing area verification), bending anchor rods within the limits permitted by AISC Design Guide 1, or modifying the base plate design to accommodate the actual rod positions. Unauthorized bending or cutting of anchor rods by the Contractor without SER direction is not permitted.
The erector shall prepare and submit an erection plan in accordance with AISC 303-22 Section 7.10, showing the planned sequence of erection, the location of shoring and temporary bracing required during each phase, the positions of cranes and their reach radii, and the sequence of bolting and welding operations needed to stabilize the structure at each stage. The erection plan is a safety and quality document; it is not a formality. Failure to sequence erection properly has caused structural failures and worker fatalities.
The erector is responsible for the stability of the steel frame at all times during erection, from the first column set until the permanent lateral force-resisting system is complete and capable of carrying its design loads. Temporary bracing shall be designed by a licensed structural engineer retained by the erector, based on the actual construction sequence and the gravity loads present at each erection phase. Temporary bracing shall not be removed until the permanent bracing, diaphragm, or moment frame connections are fully installed, inspected, and verified by the SER and QA inspector to be complete.
Field-bolted connections shall be assembled in accordance with the sequence described in the Bolting section, with bolts brought to snug-tight before the pretensioning sequence begins in each connection. Field-welded connections shall be made by welders whose qualifications are current for the positions and processes required, using approved WPS. The ambient temperature and wind conditions shall be checked before field welding begins; AISC 360-22 and AWS D1.1:2025 set minimum base metal temperature requirements (generally 0°F for most steels) and prohibit welding when the surface to be welded is wet or when the wind speed would disturb gas shielding.
Field modifications — cutting, drilling, or welding not shown on the approved shop or erection drawings — shall not be performed without written approval from the SER. The SER shall evaluate field modification requests promptly to avoid causing erection stoppages. Unauthorized field modifications void the quality certifications of the affected members.
The erector shall maintain the steel frame within plumbness tolerances throughout erection and shall plumb the frame as erection progresses, not only at completion. Delaying plumbing until the frame is complete makes corrections increasingly difficult and may require the erector to remove and re-erect members. Members shall be released from the crane only after they have been adequately connected and braced to be stable without the crane. Single-bolt pickup connections shall not be relied upon for stability.
Hot-rolled structural steel shapes are produced within the rolling tolerances of ASTM A6/A6M-24. These tolerances cover deviations in cross-sectional dimensions (flange width, flange thickness, web thickness, overall depth), straightness, and camber as-received from the mill. Mill tolerances are inherent in the structural steel supply chain and are accounted for in standard connection designs. Members with mill-induced defects exceeding ASTM A6/A6M-24 limits shall be rejected.
Fabrication tolerances per AISC 303-22 govern the accuracy of dimensions introduced during shop fabrication: member length (±1/16 in. for members up to 30 ft; ±1/8 in. for members 30 to 65 ft), hole placement (±1/16 in. from specified location), column ends squareness, and camber. The fabrication tolerance is additional to the mill tolerance; connection details must accommodate the combined worst-case stack-up of mill plus fabrication tolerances.
Erection tolerances per AISC 303-22 Sections 7.13 through 7.16 govern the position and plumbness of the erected steel. Key tolerances are as follows:
Column plumbness: deviation from plumb shall not exceed 1/500 of the column height (approximately 1/4 in. per 10 ft of height), with an absolute maximum of 1 in. toward the building exterior and 1 in. toward the building interior for the upper portion of columns above 300 ft.
Column base plate elevation: ±3/16 in. from the established floor datum.
Beam end elevation: ±3/8 in. from the established floor datum.
Beam alignment: beams shall be positioned within ±1/4 in. of the plan position shown on the structural framing plan.
The erector shall survey the completed steel frame and submit a written report to the SER documenting that plumbness, elevation, and alignment measurements are within the specified tolerances. The SER shall review the survey report before permanent floor construction loads (deck, concrete) are applied to the frame. Erected steel that exceeds tolerance shall not be loaded with permanent construction until the SER has reviewed and accepted the condition in writing.
All welds shall be visually inspected per AWS D1.1:2025 Clause 8. Visual inspection is the most fundamental and cost-effective inspection method and shall be performed first; it identifies the majority of weld defects (insufficient size, undercut, porosity, overlap, improper profile, and cracks) without consumables or equipment, and it catches defects before they require costly NDT rejection and repair. Visual inspection of completed welds shall verify: correct weld size, length, and location; acceptable weld surface profile (no excessive convexity or concavity, undercut, overlap); complete fusion at weld toes; absence of cracks; and cleanliness between passes on multi-pass welds. QC visual inspection shall be performed by the fabricator's inspector. QA visual inspection shall be performed by the Owner's independent inspector.
Ultrasonic testing (UT) is the preferred volumetric NDT method for structural steel because it is portable, does not require radiation control, and can detect internal discontinuities (incomplete fusion, planar flaws, porosity) throughout the full weld volume. Radiographic testing (RT) provides a permanent film record but requires radiation safety exclusion zones and is more difficult to apply in the field; RT is typically used for specific welds where the geometry prevents effective UT scanning, such as small-diameter pipe and certain tee-joint configurations. Magnetic particle testing (MT) is a surface and near-surface method only; it is excellent for detecting cracks that have opened to or near the surface and shall be used for fillet weld examination where surface defects are suspected and for all welds in accessible locations in high-seismic applications.
AISC 360-22 Table N5.4-1 establishes minimum NDT rates based on building risk category. For Risk Category II (most commercial buildings), the minimum rate is 10% for CJP groove welds loaded in compression and 25% for CJP groove welds loaded in tension. For Risk Category III and IV (essential facilities), 100% NDT of CJP groove welds in tension is required. NDT of CJP welds in compression is not required for Risk Category I and II buildings beyond the minimum per Table N5.4-1 unless the SER specifies otherwise. The SER may specify rates higher than the code minimum for critical connections regardless of risk category.
NDT personnel shall be qualified per ASNT SNT-TC-1A at Level II or higher for the specific test method used. AWS Certified Welding Inspectors (CWI) qualify for visual inspection but shall hold separate ASNT qualification to perform UT, RT, or MT. Level II personnel shall perform tests and evaluate indications independently; Level I personnel may perform tests under Level II supervision but shall not independently evaluate results.
The QA inspector shall verify bolt installation for each connection in accordance with RCSC 2020 Section 9 and AISC 360-22 Chapter N inspection tables N5.6-1, N5.6-2, and N5.6-3. Snug-tight connections require visual inspection for firm contact; pretensioned connections require witnessed or documented pre-installation verification and documentation of the tightening operation for a minimum of 10% of bolts in each connection; slip-critical connections require the same as pretensioned, plus documentation that faying surface conditions were verified before assembly. Bolts found to not meet the tightening requirements shall be re-tightened or replaced; in no case shall the bolt be re-used after it has been tightened to the failure point.
Shear stud welding shall be verified by the weld bend test per AWS D1.1:2025 Clause 9.8.1. A minimum of ten studs per operator per shift shall be tested when welding through steel deck; five studs per operator per shift when welding to bare steel. Studs that fail the visual inspection criteria shall be bent to 30 degrees from vertical and inspected; a stud that remains intact at 30-degree bend with no visible fracture is acceptable. Studs with fractured welds shall be chipped off and replaced, with the weld area ground smooth before a new stud is welded.
Structural steel shall be delivered to the project site in the fabricator's standard bundling, with each piece clearly marked with its erection mark. Members shall be loaded and transported to prevent distortion, impact damage to members or coatings, and contact with incompatible materials. Long members shall be adequately supported during transport to prevent permanent sag.
At the site, steel shall be stored on timber dunnage or other supports that keep members off the ground surface. Storing steel directly on soil causes corrosion damage to the coating and introduces contamination at contact surfaces. Members shall be arranged to allow drainage; water shall not be permitted to pond on horizontal surfaces or inside HSS members. Open ends of HSS shall be capped or plugged to prevent water accumulation and the freeze-thaw cycling that can split seam welds in A500 tubing.
Members arriving with kinks, bends, twists, or coating damage that exceeds the limits of the touch-up specifications shall be reported to the SER before erection. Members shall not be erected until the SER has reviewed and accepted the condition or directed corrective action. Members with section loss from corrosion shall not be erected without the SER's written acceptance.
The fabricator shall warrant the structural steel work against defects in material and workmanship, including fabrication errors discovered after erection, weld defects not detected during inspection, and dimensional non-conformances that become apparent under load. The erector shall warrant the erection work, including misalignment, plumbness deviations, incorrect connections, and damage to coatings or members caused by erection operations. The warranty does not cover damage caused by other trades, overloading beyond the design basis, modifications by others after completion of the structural steel work, or normal weathering and corrosion of uncoated or inadequately maintained steel.
Shop coating and primer warranties are limited to coverage against coating failures attributable to improper surface preparation or application; the warranty does not cover field damage to shop coatings. Where a full exterior paint system is applied in the field, the painting subcontractor's warranty covers the complete coating system applied in the field.