AISC standards for steel design, detailing and fabrication.

What AISC publishes and what each document governs

AISC, the American Institute of Steel Construction, publishes the family of standards that most US building codes reference for structural steel, and it is that adoption by reference that makes the documents mandatory on a project rather than merely advisory.

• AISC 360, Specification for Structural Steel Buildings — the design basis: member strength, stability, connection design and serviceability.
• AISC 303, Code of Standard Practice for Steel Buildings and Bridges — the document that governs standard practice once design is finished: what the contract documents are assumed to include, fabrication and erection tolerances, and where responsibility sits between the engineer of record and the fabricator.
• AISC 341, Seismic Provisions for Structural Steel Buildings — additional detailing requirements for members and connections inside a seismic force-resisting system.

A detailer works from all three at once. The specification decides what a member has to do, the code of standard practice decides how it is drawn and toleranced, and the seismic provisions decide whether a connection needs ductile detailing at all.

What AISC covers, and what it does not

AISC 360 and AISC 341 are written for buildings and building-like structures. That phrase does real work, because it leaves out two of the largest categories of steel infrastructure in the United States, and a package detailed to the wrong family is wrong from the first sheet rather than at the last check.

Highway bridges are designed to the AASHTO LRFD Bridge Design Specifications, published by the American Association of State Highway and Transportation Officials, and welded to AASHTO/AWS D1.5, the bridge welding code, rather than to AWS D1.1. Railroad bridges follow the AREMA Manual for Railway Engineering. Both bring their own fatigue provisions, their own inspection regimes and their own tolerances, and neither defers to AISC 360 for them.

The boundary is not always where a reader expects it. A pedestrian link between two buildings, a pipe rack on a plant site, a crane runway girder inside an industrial building — each sits somewhere on the line between building-like and infrastructure, and the answer comes from what the design specification says rather than from what the structure looks like. AISC 303 spans the gap deliberately: it is the Code of Standard Practice for Steel Buildings and Bridges, so standard practice can be common even where the design specification is not.

How AISC becomes mandatory, and which edition

AISC develops standards; it does not regulate. Its documents become mandatory through adoption by reference. The International Building Code names AISC 360 and AISC 341 as the design standards for structural steel, and a state, county or city that adopts the IBC adopts those standards with it. Where a jurisdiction has not adopted them, or where the work sits outside a building code altogether, AISC still governs whenever the project specification says so — which, on structural steel in the United States, is nearly always.

The edition matters as much as the document. AISC 360 has been reissued on a roughly five-to-six-year cycle, and the edition a jurisdiction enforces is the one named in the building code that jurisdiction adopted, not the newest one AISC has published. Adoption lags publication, and it lags unevenly: two neighbouring authorities can be enforcing different editions of the same specification at the same time, which matters because provisions do move between editions.

So a package is set up against a named edition rather than against AISC in general. The governing edition, the seismic design category where AISC 341 applies, and the connection design split are fixed at intake and recorded together, so the checks run against the document the approving authority will actually open.

AISC 360 and the design basis

AISC 360 sets the design basis: how member strength is calculated for tension, compression, flexure and shear, how overall stability is assessed under the direct analysis method, and how connections are proportioned once a load path is chosen. It works through both load and resistance factor design and allowable strength design, and a drawing set should make clear which basis governs, since tolerances and factors of safety are not interchangeable between them.

The specification leans on other standards rather than repeating them: ASTM material specifications such as A992 for wide-flange shapes and A500 for hollow structural sections, the RCSC Specification for Structural Joints Using High-Strength Bolts for bolted connections, and AWS D1.1 for welding procedure and qualification. A detailer who only reads AISC 360 is reading half the picture; the bolt and weld provisions live one level down, in the documents it references.

AISC 303: responsibility, tolerance and assumption

AISC 303 is the document a detailer actually argues over, because it decides what a fabricator is entitled to assume when a drawing is silent. It sets out what a complete set of contract documents should contain, defines standard mill and fabrication tolerances for cross-section, straightness and length, sets erection tolerances for plumbness and alignment, and states how camber is specified and measured.

It also settles the connection design split. Where the engineer of record designs every connection, the fabricator details to that design. Where the contract delegates connection design, a licensed engineer engaged by the fabricator designs the connection against the loads the engineer of record provides, and that design is submitted back for approval. Most disputes on a steel project trace back to that split being unclear rather than to an error in either party's calculation.

What AISC changes in a detailing package

Once a package is set up under AISC, several things follow directly onto the sheet. Standard, oversized and slotted bolt hole dimensions come from the bolting provisions in AISC 360 and the RCSC specification, not from habit, and they change with bolt diameter and connection type. Camber is called out and measured the way AISC 303 defines it, not as a general note. Erection tolerances for plumbness and alignment set what the erection drawings need to show for the steel to be accepted on site.

Where a member sits inside a seismic force-resisting system, AISC 341 adds detailing a gravity connection never sees — moment connection geometry validated under AISC 358, protected zones where welds and attachments are restricted, and demand-critical welds that carry their own inspection requirements. Flagging which members are seismic and which are gravity is one of the first decisions a package under AISC has to record, because the two are detailed differently from the same beam schedule onward.

Inspection reaches the sheet too. AISC 360 Chapter N sets the quality control and quality assurance requirements for fabrication and erection: quality control performed by the fabricator and erector, quality assurance performed by an agency engaged for the owner, and a split between tasks that are observed and tasks that must be performed on every item. It also sets where non-destructive testing is required, including ultrasonic testing of complete-joint-penetration groove welds above a defined thickness in the higher risk categories. Where AISC 341 applies, demand-critical welds carry heavier inspection again. Those requirements surface as weld callouts, inspection notes and a weld map a testing agency can work from — or they do not, and the site finds out during erection.

How we check a package against AISC

The automated checks on a US package are configured to AISC 360 and AISC 303 specifically: bolt edge distance, gauge and hole type checked against the specification's bolting tables, weld symbols checked for legality against AWS A2.4, member sizes and grades on the sheet checked against the model, and camber and mill tolerance notes checked against what AISC 303 requires to be stated. Where connection design is delegated, the detailed connection is checked against the loads the engineer of record issued before it is submitted for approval.

None of that replaces the review. A senior engineer reviews the checked package and signs it before issue, and that signature, not the check record on its own, is what a project is actually buying.