---- | -------------- | ---------- | ---------- | --------------------------- | | W8x31 | 31 | 9.12 | 8.00 | Light columns, short beams | | W10x33 | 33 | 9.71 | 9.73 | Columns, beam-columns | | W12x26 | 26 | 7.65 | 12.22 | Floor beams, light framing | | W12x40 | 40 | 11.7 | 11.94 | Floor beams, moderate spans | | W14x30 | 30 | 8.85 | 13.84 | Columns, beams | | W16x36 | 36 | 10.6 | 15.86 | Floor beams (most common) | | W18x35 | 35 | 10.3 | 17.70 | Floor beams | | W18x46 | 46 | 13.5 | 18.06 | Heavier floor beams | | W21x44 | 44 | 13.0 | 20.66 | Long-span floor beams | | W24x55 | 55 | 16.2 | 23.58 | Transfer beams, girders | | W27x84 | 84 | 24.7 | 26.71 | Heavy girders | | W30x90 | 90 | 26.3 | 29.53 | Long-span girders | | W33x118 | 118 | 34.7 | 33.30 | Transfer girders | | W36x135 | 135 | 39.7 | 35.55 | Long-span transfer girders |

HSS shapes

Shape Weight (lb/ft) Area (in²) Common Use
HSS2x2x1/4 5.59 1.64 Bracing, architectural
HSS3x3x3/16 6.92 2.03 Bracing, minor columns
HSS4x4x1/4 11.9 3.49 Columns, truss chords
HSS6x6x3/8 27.5 8.08 Columns, frames
HSS6x6x1/2 35.2 10.3 Heavy columns
HSS8x8x3/8 37.7 11.1 Major columns
HSS8x8x1/2 49.0 14.4 Transfer columns
HSS10x10x1/2 62.5 18.4 Heavy columns, trusses
HSS12x12x1/2 75.7 22.2 Monumental columns
HSS16x16x5/8 119 35.0 Heavy column stacks

Angles and channels

Shape Weight (lb/ft) Area (in²) Common Use
L3x3x1/4 4.75 1.39 Light bracing, lintels
L4x4x3/8 9.10 2.67 Bracing, connections
L6x6x1/2 18.4 5.41 Heavy bracing, framing
C6x13 13 3.82 Light framing, purlins
C8x18.75 18.75 5.51 Floor framing
C10x20 20 5.87 Girts, purlins
C12x25 25 7.34 Heavy purlins, beams
MC10x22 22 6.47 Specialty framing
MC12x31 31 9.10 Crane runway beams

Worked Example — Floor Framing Material Takeoff

Problem: A 5-story office building has the typical floor framing shown below. Calculate the total structural steel weight for one typical floor level.

Given data

Plan dimensions: 120 ft × 80 ft
Beam spacing: 6 ft on center (short direction)
Beam span: 40 ft (long direction)
Girder span: 30 ft (short direction)
Interior columns: W12x65 at each grid intersection
Perimeter columns: W10x49 at each grid intersection

Grid: 4 bays × 30 ft (long) × 2 bays × 40 ft (short)
Total bays: 8
Interior columns per floor: 3 (one per row × 3 rows)
Perimeter columns per floor: 12 (on grid lines)

Step 1 — Floor beams

Number of beams: 120/6 = 20 beams per girder line × 3 girder lines = 60 beams
But there are 4 × 30ft girders per 40ft direction = 2 × 4 = 8 girder lines? Let me simplify.

Beam count: 5 beam lines per 30ft bay × 3 bays = 15 beam lines × 2 rows = 30 beams
Each beam spans 40 ft.

Section: W16x36 (typical floor beam)
Weight per beam: 36 × 40 = 1,440 lb
Total beam weight: 30 × 1,440 = 43,200 lb = 21.6 tons

Step 2 — Girders

Number of girders: 2 rows × 4 bays = 8 girders + 2 edge lines × 4 = 8 more = 16 girders
Actually: 2 interior girder lines × 4 bays = 8 girders at 30 ft each.

Section: W21x44 (typical girder)
Weight per girder: 44 × 30 = 1,320 lb
Total girder weight: 8 × 1,320 = 10,560 lb = 5.28 tons

Step 3 — Columns (one story height, 14 ft floor-to-floor)

Interior columns: 3 × W12x65 × 14 ft = 3 × 65 × 14 = 2,730 lb
Perimeter columns: 10 × W10x49 × 14 ft = 10 × 49 × 14 = 6,860 lb
Total column weight: 9,590 lb = 4.80 tons

Step 4 — Total and add connections allowance

Beams:     43,200 lb
Girders:   10,560 lb
Columns:    9,590 lb
Subtotal:  63,350 lb

Connection allowance (5%): 3,168 lb
Misc (stairs, openings):   2,000 lb

Grand total: 68,518 lb = 34.3 tons per floor

Steel weight per sq ft: 68,518 / (120 × 80) = 7.1 psf

A structural steel framing weight of 5-10 psf is typical for office buildings. This 7.1 psf falls squarely in the expected range, confirming the takeoff is reasonable.

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Worked Example: Steel Takeoff for Simple Frame

Problem: Calculate the total steel weight for a single-bay portal frame: 2 columns W12x65, 20 ft tall; 1 beam W18x50, 40 ft span; base plates 3/4 in. x 14 in. x 14 in. (4 plates); cap plates 1/2 in. x 8 in. x 12 in. (2 plates).

Given:

Solution:

Step 1 -- Member weights (AISC Table 1-1):

W12x65: 65 plf x 20 ft x 2 columns = 2,600 lb
W18x50: 50 plf x 40 ft x 1 beam   = 2,000 lb
Total member weight               = 4,600 lb

Step 2 -- Plate weights (0.284 lb/in^3):

Base plate: 0.284 x 14 x 14 x 0.75 x 4 = 0.284 x 588 = 167 lb
Cap plate:  0.284 x 8 x 12 x 0.50 x 2  = 0.284 x 96  = 27 lb
Total plate weight                        = 194 lb

Step 3 -- Connection allowance:

Connection = 5% x 4,600 = 230 lb

Step 4 -- Total frame steel weight:

Total = 4,600 + 194 + 230 = 5,024 lb = 2.51 tons

Result: Total estimated steel weight is 2.51 tons. At $3,000/ton fabricated and erected (typical 2026 pricing for small commercial), approximate cost = $7,530. At 5-8 psf average for low-rise, this ~800 ft^2 footprint is in the expected range.

Frequently Asked Questions

How do I read a W-shape designation like W18×35? The W designation identifies a wide-flange section. The first number (18) is the nominal depth in inches — the actual depth of a W18×35 is 17.7 inches, close to but not exactly 18 inches because AISC standardises depth within a family. The second number (35) is the weight in pounds per linear foot. This means a W18×35 weighs 35 lb for every foot of length, which comes directly from the cross-sectional area multiplied by the steel density. In SI sections the designation uses the depth in mm and the mass in kg/m.

What is the density of structural steel and how is weight per foot calculated? Structural steel has a unit weight of approximately 490 lb/ft³ (77.0 kN/m³ or 7850 kg/m³). The weight per linear foot of a section equals its cross-sectional area (in²) multiplied by 490 lb/ft³ and divided by 144 in²/ft² — or equivalently, area (in²) × 3.40 lb/(in²·ft). The AISC Steel Construction Manual tabulates this directly as the nominal weight in lb/ft for every listed section, so it is rarely necessary to compute from first principles unless you are dealing with a non-standard built-up section.

How do I convert lb/ft section weight to a dead load in psf? The self-weight of a beam in lb/ft is a line load, not an area load. To convert it to a contribution to the dead load psf for slab design or load combination purposes, divide the lb/ft weight by the tributary width (in feet) that the beam serves. For example, a W18×35 (35 lb/ft) on 10 ft centres contributes 35/10 = 3.5 psf to the dead load — a small but not negligible fraction of a typical 50–75 psf superimposed dead load. For long-span beams or closely spaced framing, self-weight can be 5–10% of the total dead load.

How do I calculate total steel weight for a material takeoff? Multiply the section weight per foot (lb/ft) by the cut length (ft) for each member, then sum across all members. For example: ten W18×35 beams at 30 ft each = 10 × 35 × 30 = 10,500 lb = 4.73 tons of structural steel. Add 2–5% for connection plates, stiffeners, and weld metal as a typical fabrication allowance. Material takeoff quantities are also used to estimate erection crane capacity and shipping tonnage.

How does self-weight affect the span capacity of long steel beams? Self-weight adds a uniform dead load that occupies part of the beam’s moment and deflection budget before any superimposed loads are applied. For a W18×35 at 30 ft span, the self-weight moment alone is 0.035 × 30² / 8 = 3.94 kip·ft, which is a small fraction of the section’s moment capacity. But for a W36×135 at 80 ft span, the self-weight moment is 0.135 × 80² / 8 = 108 kip·ft — a much more significant demand. As spans exceed roughly 20 m (65 ft), self-weight typically consumes 15–25% of total allowable moment, so it must be explicitly included in the load combination rather than treated as negligible.

How much does a W12×26 weigh over a 20-foot span, and what dead load does it contribute? A W12×26 weighs 26 lb/ft by definition (the designation encodes the weight), so a 20-foot member weighs 26 × 20 = 520 lb = 0.26 tons. For dead load purposes on a floor framing system, this is a line load of 0.026 kip/ft. If this beam frames into a 10-foot tributary width, the dead load contribution is 0.026 / 10 = 0.0026 kip/ft² = 2.6 psf — small relative to a typical 50–100 psf superimposed floor load, but non-negligible for a long-span beam where cumulative self-weight governs deflection rather than strength.

Code References

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