Structural Steel Specifications (USA / AISC 360)

Construction Structural Steel AISC USA Engineering Compliance

Overview

The Structural Steel Specifications (USA / AISC 360) skill helps Rakenne users draft, review, and validate technical specifications for load-bearing structural steel buildings in the United States. It covers the full AISC 360 scope — material selection, LRFD/ASD design factors, member and connection design, seismic considerations, and serviceability — with automated cross-referencing of ASTM steel grades and safety-margin validation. The skill includes AISC 360 and ASTM reference tables, a complete specification template, a compliance checklist, and two extension tools for code cross-referencing and draft validation.

Getting Started

Add your source materials to the project workspace (existing specification drafts, analysis outputs, project requirements), then activate the Structural Steel Specifications (USA / AISC 360) skill. The agent will guide you through defining the project scope, selecting materials, establishing the design basis, and drafting a specification. The result can be saved under output/ alongside a validation report and completed checklist.

Example Conversation

Below is an example of how a typical specification-drafting session unfolds. The agent collects project context, applies the specification template, cross-references ASTM grades, and validates the draft.

You: I need to draft a structural steel specification for a new 5-story office building in Chicago. We’re using LRFD. The lateral system is special concentrically braced frames.
Agent: I’ll help you put together a complete specification per AISC 360. To fill in the design basis accurately, I need a few details:
What is the approximate footprint and typical bay spacing?
Do you have the geotechnical report with the site class, or should I assume Site Class D (default)?
Any specific steel grades you’d like to use, or should I go with standard practice (A992 for W-shapes, A500 Gr. C for HSS braces, A572 Gr. 50 for plates)?
You: About 120 ft × 200 ft, 30-ft bays. Assume Site Class D. Use the standard grades you mentioned. Roof snow load is 25 psf ground.
Agent: I’ve set up the specification using the skill template and populated the key sections. Here’s a summary of what I’ve established:
Design basis: LRFD per AISC 360-22, ASCE 7-22, IBC 2024. Risk Category II. For Chicago (Site Class D), SDS ≈ 0.40g, SD1 ≈ 0.17g → Seismic Design Category C. Since you’re using SCBF, I’ve referenced AISC 341-22 for seismic provisions.
Materials: A992 for W-shapes (Fy = 50 ksi, Fu = 65 ksi), A500 Gr. C for rectangular HSS braces (Fy = 50 ksi, Fu = 62 ksi), A572 Gr. 50 for gusset plates, Group A bolts (A325), E70XX electrodes.
Loads: I’ve itemized dead loads (deck, MEP, ceiling), live loads per ASCE 7 Table 4.3-1 (50 psf office, 80 psf corridors), roof live load 20 psf, ground snow load 25 psf, and listed all 7 LRFD load combinations.
I ran structural_code_referencer on A992 and A500 Gr. C — the reference cards with φ factors and design formulas are embedded in the spec. I also ran check_yield_safety_margin on the draft: no errors, but 8 placeholders remain (specific deflection calculations, connection details, and fire protection). The draft is at output/structural_steel_spec_chicago_office.md. Want me to fill in the member design section next?
You: Yes, and run the checklist too.
Agent: Done. I’ve completed the member design section with checks for beams (yielding and LTB per AISC F2), columns (flexural buckling per AISC E3), and braces (slenderness per AISC 341). The connections section includes standard shear tabs for gravity beams and gusset plate criteria for SCBF braces. I’ve also applied the compliance checklist — all items pass except fire protection (not yet specified) and the vibration assessment (marked N/A per your confirmation). The updated spec and checklist are saved alongside the validation report.

Output Excerpt

Below is a representative excerpt from a structural steel specification produced with the skill — showing the material specification and design factors sections after template application and code cross-referencing.

Structural Steel Specification — Excerpt

Project: 5-Story Office Building, Chicago, IL
Design Method: LRFD per AISC 360-22
Governing Codes: AISC 360-22, ASCE/SEI 7-22, IBC 2024, AISC 341-22

3. Material Specification

3.1 Steel Grades

Element	ASTM Specification	Fy (ksi)	Fu (ksi)
W-shapes (beams, columns)	A992	50	65
HSS braces (rectangular)	A500 Gr. C	50	62
Gusset plates, connection plates	A572 Gr. 50	50	65
Angles, miscellaneous steel	A36	36	58
Pipe columns (if any)	A53 Gr. B	35	60

All steel shall have E = 29,000 ksi. Mill certificates shall be provided for all structural steel.

3.2 Bolts

Application	Group	ASTM	Installation
Shear connections (gravity)	Group A	A325 / F1852	Snug-tight
Brace connections	Group A	A325 / F1852	Pretensioned
Slip-critical (where noted)	Group A	A325 / F1852	Slip-critical, Class A faying surfaces
Anchor rods	—	F1554 Gr. 36	—

3.3 Welding

Filler metal: E70XX (FEXX = 70 ksi)
Welding process: FCAW-S or SMAW in field; FCAW-S or SAW in shop
Preheat: Per AWS D1.1 Table 5.8

6.1 Beam Design (typical floor beam W21×44)

Span: 30 ft, composite with 3-in. metal deck + 3.25-in. lightweight concrete
Unbraced length: Lb = 0 (continuous top-flange bracing by deck)
Nominal strength: Mn = Mp = Fy × Zx = 50 × 95.4 = 4,770 kip-in = 397.5 kip-ft
Design strength (LRFD): φb × Mn = 0.90 × 397.5 = 357.8 kip-ft
Required strength: Mu = 285 kip-ft → Mu/φMn = 0.80 — OK
Deflection: ΔLL = L/480 = 0.75 in. (actual 0.62 in.) — OK

This excerpt is illustrative. Final content must reflect actual project-specific data, analysis results, and the applicable code edition.

Extension Tool Validations

The skill includes two extension tools that automate code cross-referencing and specification validation. Below is what each tool checks and how to interpret results.

`structural_code_referencer`

Returns material properties and design parameters for a given ASTM steel grade and design method.

Output	Description
Material properties	Fy (yield strength), Fu (tensile strength), typical shapes per the ASTM standard
LRFD design strengths	φ factor and design formula for each limit state (tension, compression, flexure, shear, block shear, bolts) with computed φ·Fy and φ·Fu values
ASD allowable strengths	Ω factor and allowable formula for each limit state with computed Rn/Ω values
Applicable standards	Full list: ASTM material spec, AISC 360, AISC 341, ASCE 7, IBC, AWS D1.1, RCSC

`check_yield_safety_margin`

Scans a Markdown specification draft for compliance issues. The report includes:

Check	Description
Required sections	Verifies presence of 10 key specification sections (project scope, codes, materials, loads, analysis, member design, connections, stability, serviceability, design method). Each is marked OK or MISSING.
Yield strength vs ASTM minimum	Detects Fy values in the document and compares them to the minimum for each ASTM grade mentioned. Flags an ERROR if Fy is below the ASTM minimum (e.g., Fy = 36 ksi stated for an A992 member that requires 50 ksi).
Resistance factors (φ)	Extracts φ values and warns if any do not match standard AISC 360 values (0.75 or 0.90).
Safety factors (Ω)	Extracts Ω values and warns if any do not match standard AISC 360 values (1.67 or 2.00).
Eurocode terminology	Flags an ERROR if γ_M0, γ_M1, or γ_M2 notation is found — these are Eurocode partial safety factors and must not be used for US AISC specifications.
Unfilled placeholders	Detects `[TBD]`, `[TODO]`, `...`, `{}`, and bracketed text that may indicate incomplete sections.
Design method detection	Reports whether LRFD, ASD, or both are referenced in the document. Warns if neither is detected.

Interpreting the result

No critical errors: All required sections present, yield values conform to ASTM minimums, and design factors match AISC 360 standards. Placeholders and warnings should still be reviewed.
ERROR(S) found: At least one critical issue — missing section, below-minimum yield strength, Eurocode notation, or non-standard design factor. Fix the issues and re-run the tool.

The tool does not substitute professional engineering judgment — it provides automated structural checks to catch common specification errors before final review.