8.1 Structural General Notes & Specification Interpretation

Structural General Notes & Specification Interpretation

The Structural General Notes (SGN) serve as the foundation for any structural steel project. For a structural steel and bolting special inspector, the SGN is the first place to look when arriving at a new project or reviewing a new set of drawings. The general notes provide the overarching rules, material requirements, and inspection criteria that apply to the entire structure, unless specifically overridden by a local detail.

Governing Codes and Standards

The first section of the SGN typically lists the governing building code, such as the International Building Code (IBC) and the specific edition year (e.g., 2021 IBC). This establishes the legal framework for the project's design and construction. More importantly for the steel inspector, the notes will invoke specific reference standards that are legally binding for the project. These typically include:

• AISC 360: Specification for Structural Steel Buildings
• AISC 341: Seismic Provisions for Structural Steel Buildings (if applicable to the seismic design category)
• RCSC Specification: Specification for Structural Joints Using High-Strength Bolts
• AWS D1.1: Structural Welding Code - Steel
• AWS D1.8: Structural Welding Code - Seismic Supplement

It is critical to verify the exact edition of these standards called out in the notes, as provisions change between editions. If the SGN specifies the 2016 AISC 360, the inspector must evaluate the work against that specific standard, even if a newer version has been published.

Material Grade Callouts

Structural steel comes in various shapes and material grades, and the SGN dictates the default grade for each member type. A typical material specification table in the SGN might look like this:

Inspectors must verify Mill Test Reports (MTRs) against these specific grade requirements. A common issue in the field is the substitution of materials. For example, if a contractor supplies ASTM A572 Grade 50 plates instead of A36, this is generally an acceptable upgrade, but if A36 is supplied where A572 Grade 50 is required, it must be rejected or evaluated by the Engineer of Record (EOR).

Special Inspection Tables and Notes

The IBC requires a Statement of Special Inspections, which is frequently incorporated directly into the SGN. This section outlines the specific tasks the special inspector must perform, categorizing them into continuous or periodic inspections.

For structural steel, the table will differentiate between tasks such as:

• Material verification (periodic)
• High-strength bolting inspection (snug-tight is typically periodic, while pretensioning may be continuous or periodic depending on the method and code edition)
• Welding inspection (multi-pass fillet welds, complete joint penetration welds)
• Steel frame erection and plumbing

The notes will also specify the required non-destructive testing (NDT), such as ultrasonic testing (UT) for CJP welds, and the required percentage of testing. If the general notes dictate that 100% of CJP welds in the moment frame require UT, the inspector must ensure this is tracked and completed.

Bolt Pretensioning Instructions

Bolting requirements are often a source of confusion between general notes and specific details. The SGN usually establishes the default connection type—for instance, stating that "All high-strength bolts shall be installed as snug-tight unless noted otherwise."

However, the notes may also contain global exceptions, such as "All bolted connections in the lateral force-resisting system shall be slip-critical." The inspector must cross-reference the framing plans to identify which members are part of the lateral system to apply the correct bolting standard. Furthermore, specific connection details on the drawings might call out "Pretensioned (PT)" or "Slip-Critical (SC)" for a particular joint. When a local detail calls for a slip-critical connection, it requires verification of the faying surface preparation (e.g., Class A or Class B coating, or bare steel) and the use of a recognized pretensioning method (turn-of-nut, twist-off type tension control bolts, direct tension indicators, or calibrated wrench).

Conflict Resolution Hierarchy

Construction documents are complex, and conflicts are inevitable. When discrepancies arise, start with the contract's own order-of-precedence clause, if it has one. For structural steel, AISC 303 Section 3.3 (in both the 14th and 15th Edition Manuals) states the default rules:

1. Design drawings govern over specifications when the two conflict.
2. Written figures govern over scaled dimensions on the design drawings.
3. Structural design drawings govern over architectural, electrical, mechanical or other trades' drawings.

Common drafting practice adds that a specific, large-scale detail (for example, a 1" = 1'-0" connection detail) governs over general notes and small-scale plans for the item it shows, and IBC 102.1 applies the same specific-over-general logic within the code.

Approved shop drawings do not override the contract documents. Shop drawings show how the fabricator will build the design, and they are crucial for piece marks and exact bolt counts. If an approved shop drawing shows a 1/4" fillet weld where the contract detail requires a 5/16" fillet weld, the contract requirement remains binding unless the engineer of record has approved a change through an RFI or revision.

AISC 303 also says that when the fabricator discovers a discrepancy in the contract documents, it must promptly notify the owner's designated representative for construction so the owner's designated representative for design can resolve it. The inspector follows the same principle: never resolve a conflict by assumption; report it and obtain a written resolution from the engineer of record.