AISC Manual · Shapes & bolts

How to read AISC steel shapes & bolt types

What W14x22, HSS6x6x3/8, and L4x4x1/2 actually mean, how to read the dimension tables, and what snug-tight, pretensioned, and slip-critical mean on the erection drawings.

Need section properties or bolt rules? See AISC’s current standards → and the Steel Construction Manual.

Shape designations decoded

Designation style	What the numbers mean	Field notes
W14x22 (wide flange)	Nominal depth in inches × weight in lb per foot	Actual depth is rarely exactly the nominal number — heavier shapes in the same "family" get deeper
S, M, HP (e.g. HP12x53)	Same pattern: nominal depth × lb/ft	S = American Standard (tapered flanges), M = miscellaneous light shapes, HP = bearing pile
C12x20.7 / MC (channels)	Nominal depth × lb/ft	MC = miscellaneous channel; don't swap C for MC without checking
WT7x11 (structural tee)	Cut from a W shape: half the depth, half the weight	A WT7x11 comes from a W14x22
L4x4x1/2 (angle)	Leg × leg × thickness, in inches	Unequal legs list the long leg first (L6x4x3/8); "LLV" / "LLH" on drawings means long leg vertical/horizontal
HSS6x6x3/8 (square/rect tube)	Outside width × outside height × nominal wall thickness	Design wall thickness can be less than nominal for some ASTM specs — the Manual lists both
HSS6.625x0.280 (round)	Outside diameter × nominal wall thickness	Round HSS is not the same product as steel pipe, even at the same OD
Pipe 4 Std / XS / XXS	Nominal pipe size and weight class	Structural pipe uses pipe sizing — see the steel pipe schedule chart

Our own summary, not the AISC Manual or RCSC Specification text. Get section properties from the AISC Steel Construction Manual or AISC shapes database, follow the structural drawings, and verify against the editions your AHJ and project spec reference. Not engineering advice.

How to read an AISC Manual dimension/property table, step by step

Step	What you do	Watch out for
1	Find the table for the shape family (W, C, L, HSS, etc.) in Part 1	W, M, S, and HP shapes are in separate tables
2	Find the row for the exact designation	Rows are grouped by nominal depth, then by weight
3	Read dimensions: area, depth, web thickness, flange width and thickness	Many dimensions are listed both as decimals (for design) and as fractions (for detailing)
4	Read properties: moment of inertia, section modulus, radius of gyration	Strong axis (x-x) and weak axis (y-y) are separate columns
5	Check the detailing columns: k-distance, workable gage, T distance	k governs fillet clearance for stiffeners and clip angles
6	Confirm the edition and material spec	Shapes get added and dropped between editions; W shapes are usually ASTM A992

Worked example — how much does a W12x26 beam weigh?

Input / step	Value	Source
Designation	W12x26	Drawings
Weight per foot	26 lb/ft	Second number of the designation
Cut length	30 ft	Shop drawing
Beam weight	26 × 30 = 780 lb	Weight = lb/ft × length
Add connection material allowance (clips, plates, bolts)	≈ +5% → ~820 lb	Estimating allowance — adjust to your detail
Cross-check: steel weighs about 490 lb/ft³, so 1 in² of section weighs 3.40 lb/ft	26 ÷ 3.40 ≈ 7.6 in² area	Physics: 490 ÷ 144

Physics only — no AISC table values. For picks, use the actual scale or shop-ticket weight plus rigging, and check the crane chart.

Structural bolts and joint types — the concepts

Term	What it means	Field impact
ASTM F3125	The combined standard that absorbed A325, A490, F1852, and F2280 (2015)	Grades A325 and A490 still exist as grades within F3125; twist-off versions are separate grades
Grade A325 vs A490	A490 is the higher-strength grade	A490 can't be galvanized and shouldn't be reused; don't substitute one for the other without the EOR
Snug-tight joint	Plies brought into firm contact — full effort of a worker with a spud wrench or a few impacts	Most shear connections; inspection is mainly visual
Pretensioned joint	Bolts tensioned to a specified minimum pretension	Needs an approved method: turn-of-nut, calibrated wrench, twist-off (TC) bolts, or DTIs
Slip-critical joint	Pretensioned and designed so the plies don't slip under load	Faying surfaces matter — paint, galvanizing, and mill scale class must match the design
Bearing-type connection	Load transfers through bolt shear and bearing on the hole	Threads included (N) or excluded (X) from the shear plane changes capacity
Pre-installation verification	Testing sample assemblies from each lot in a tension calibrator before use	Required for pretensioned and slip-critical work — plan the calibrator on site

Joint type is called out on the drawings (SC, PT, or ST). Our own summary, not the AISC Manual or RCSC Specification text. Get section properties from the AISC Steel Construction Manual or AISC shapes database, follow the structural drawings, and verify against the editions your AHJ and project spec reference. Not engineering advice.

Common field mistakes

Mistake	What to do instead
Assuming a W14 is exactly 14 in deep	Look up actual depth in the Manual — it varies by weight within the nominal size
Reading HSS wall as full nominal thickness for design	The Manual lists a design wall thickness; use it for calcs, nominal for ordering
Substituting round HSS for pipe (or the reverse)	Different ASTM specs, walls, and strengths — get EOR approval
Pretensioning a snug-tight joint "to be safe" with A490s	Follow the joint type called out; over-tensioning is not always harmless
Painting faying surfaces of slip-critical joints	Mask faying surfaces unless the coating is qualified for the specified slip class
Skipping pre-installation verification	Test each lot/assembly combination in a tension calibrator before installing

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Steel shapes and bolts, in plain language

Get the actual values from AISC. Shape dimensions and properties come from the AISC Steel Construction Manual (Part 1) and AISC’s shapes database; bolted-joint rules come from the RCSC Specification. AISC lists its current standards on its site. This page explains how to read them; it doesn’t reproduce the tables.

The designation tells you depth and weight. For W, S, M, HP, and channel shapes, the first number is the nominal depth in inches and the second is weight in pounds per foot. Angles and HSS work differently: angles list leg × leg × thickness, square/rectangular HSS list outside dimensions × wall, and round HSS list outside diameter × wall. A WT is a W shape split in half — half the depth and half the weight.

Worked example. A 30 ft W12x26 weighs 26 × 30 = 780 lb before connection material. Because steel weighs about 490 lb/ft³, every square inch of cross-section weighs 3.40 lb per foot — so 26 lb/ft implies about 7.6 in² of steel, a quick sanity check against the Manual’s area column.

Bolts: grade and joint type are separate choices. ASTM F3125 now covers the high-strength structural bolts formerly specified as A325 and A490 (and their twist-off versions). The drawings then call the joint type: snug-tight, pretensioned, or slip-critical. Pretensioned and slip-critical joints need an approved tensioning method and pre-installation verification in a tension calibrator; slip-critical joints also need the faying surfaces prepared to the design slip class.

Related references: the steel pipe schedule chart for pipe columns and bollards, the crane power line clearance chart for erection near lines, and the equipment inspection checklist. Field PM keeps bolt-lot certs, calibrator results, and connection inspection photos with each job.

FAQ

What does W14x22 mean?+

W is a wide-flange shape, 14 is the nominal depth in inches, and 22 is the weight in pounds per linear foot. The actual depth is close to — but usually not exactly — 14 in; look it up in the AISC Manual.

How do I calculate the weight of a steel beam?+

Multiply the weight per foot (the second number in the designation) by the length. A 30 ft W12x26 weighs 26 × 30 = 780 lb, plus connection material. For picks, use the shop ticket weight and include rigging.

Are A325 and A490 bolts still made?+

Yes, as grades within ASTM F3125, which consolidated A325, A490, F1852, and F2280 in 2015. Drawings may still say A325 or A490 — they mean F3125 Grade A325 or Grade A490. The twist-off versions are separate grades.

What is the difference between snug-tight, pretensioned, and slip-critical?+

Snug-tight joints only bring the plies into firm contact. Pretensioned joints tension each bolt to a specified minimum using an approved method. Slip-critical joints are pretensioned and also rely on friction between the plies, so faying-surface prep and coatings must match the design slip class.

Where can I get the AISC Specification?+

AISC publishes its current standards, including the Specification for Structural Steel Buildings (AISC 360) and the RCSC bolt specification, at aisc.org — check the current-standards page for download options. Shape dimensions and properties are in the Steel Construction Manual and AISC's shapes database.

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