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Sheet S-118
PPDPDD CE

Steelconcept

Steel shapes and members: W-shapes, HSS, joists, decking

One-line orientation

The shape catalog (W / S / C / L / HSS / pipe), how to read a W-designation, and joist-vs-beam and deck choices — the exam tests reading the call-out and matching the member to the span/load.

Key points

  • Rolled and formed shapes:
    • W (wide-flange): wide flanges, high strength and stiffness; the standard beam and column shape; supports variants like castellated beams.
    • S (American Standard / “I-beam”): older, narrower tapered flanges; largely superseded by W-shapes.
    • C (channel): C-shaped; framing, edges, built-up members.
    • L (angle): L-shaped, equal or unequal legs; bracing, connections, lintels.
    • HSS (hollow structural section): square/rectangular tube; clean look, good in compression/torsion. Pipe: round hollow section, often as columns.
  • Reading the W-designation (e.g. W12×26):
    • First number = nominal depth (inches). Second number = weight (lb per linear foot).
    • Depth is nominal, not exact — members in a group share a nominal depth at different weights.
  • Open-web steel joists (truss-like; openings for MEP):
    • K-series — standard, most common, shorter spans.
    • LH (Long-span) — longer spans.
    • DLH (Deep Long-span) — longest/deepest spans.
  • Metal deck:
    • Form deck — stays in place as formwork for a concrete slab.
    • Composite deck — ribbed/embossed to bond with concrete so deck + slab act compositely.
    • Roof deck — supports roof loads; may carry insulating concrete, gypsum, or be bare where a lightweight non-combustible roof surface suffices.
  • Composite beam action: shear studs weld the beam to the concrete slab so they act as one deeper member, raising capacity.
  • Camber: beam pre-curved upward so it deflects to level under load.
  • Approximate depth rules of thumb (preliminary sizing): beam ≈ span/20, girder ≈ span/15, open-web joist ≈ span/20, composite deck ≈ span/24, steel deck ≈ span/40.

Steel shapes by section — and reading W12×26

Six sections to recognize — and how a W-designation decodes.

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Steel shapes by section — and reading a W12×26 designation Left panel, a shape catalog: six solid-filled steel cross-sections sit on one shared baseline — W (wide flanges with parallel inner faces), S (a narrower American-Standard I-beam with visibly tapered inner flange faces), C (channel, flanges open to one side), L (equal-leg angle), HSS (square hollow ring) and Pipe (round hollow ring). Each carries its designation letter and name; W and S are tied by a bracket labelled the confusable pair, with a note that S is narrower, tapered and largely superseded. Right panel decodes the call-out W12×26: three rows read W as wide-flange, 12 as nominal depth in inches, and ×26 as weight in pounds per foot. An enlarged wide-flange section drawn deeper than wide carries an ink-blue dimension string, with witness lines and arrowheads, on its vertical depth and labelled 12 — showing the first number measures depth, not width. An amber caution band warns that depth is not width and nominal is not exact: a group shares one nominal depth at different weights. A note flags that the silhouettes are schematic and not to scale. SHAPE CATALOGcross-section sets the shapeWwide-flangeSI-beamCchannelLangleHSSsquare tubePiperoundEASY TO CONFUSEW: wide + parallel · S: narrow + taperedS is largely superseded by WREAD THE CALL-OUTW12×26Wwide-flange12nominal depth (in)×26weight (lb / ft)12depthDepth is not width · nominal is not exacta group shares one nominal depth at different weights

Silhouettes are schematic — proportions not to scale.

Steel joists — depth buys span; open web buys routing space

Schematic

Read K → LH → DLH as one series, then compare the open web with a solid-web beam.

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K, LH, and DLH open-web steel joists grow deeper and longer, while an open web routes MEP unlike a solid-web beam K, LH, and DLH joist elevations share a left datum and progressively grow deeper and longer. A qualitative arrow and the preliminary sizing rule depth approximately equals span divided by twenty reinforce the relationship. Below, a blue MEP route passes through an open-web joist but stops at a hatched solid-web W-shape. The solid-web member is labeled for heavier or concentrated loads. JOIST SERIES · SHARED LEFT DATUMKstandardshortest spansdepthLHlong-spandepthDLHdeep long-spandepthSPAN AND REQUIRED DEPTH GROW TOGETHERdepth ≈ span/20Open weblighter / longer spansduct sectionFITS WITHIN THE WEB OPENINGSolid-web W-shapeheavier / concentrated loadsNO WEB PASS-THROUGH
  • duct section placed inside an open-web void

Trap: a solid-web beam is not automatically better; choose by span and load, and account for the open joist's MEP-routing advantage.

Confusions / comparison

MemberWebBest forNotes
W-shape (solid-web beam)SolidHeavier/concentrated loads, columnsStandard modern shape; designated depth × weight/ft
S-shape (I-beam)SolidLegacy useNarrower tapered flanges; superseded by W
Open-web steel joistOpen (truss)Longer spans, lighter/roof loadsLight, economical; MEP routes through web
HSS / pipeHollowColumns, exposed members, torsionTube (square/rect) or round
W-designationReads as
W12×26Wide-flange · 12 in nominal depth · 26 lb per linear foot

→ Steel types and production (this module): hot-rolled origin of these shapes · Steel connections (this module): how shapes are joined (shear vs moment) · Steel lateral systems (this module): how shapes assemble into frames · Steel fireproofing (this module): protecting exposed members.

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Steel connectionsSteel fireproofingGalvanic actionLateral systems