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Structuralaka: wide-flange beamaka: H-beamaka: W-shape

I-Beam

In Plain English

A steel beam with an I-shaped cross-section that efficiently resists bending under load.

Definition

A steel or aluminum structural member with a cross-section shaped like the letter I, consisting of two horizontal flanges connected by a vertical web. The I-shape provides high bending resistance relative to its weight by placing material where stress is greatest—at the top and bottom flanges. I-beams are widely used for floor beams, roof framing, and columns.

Why It Matters in Bidding

Steel members like I-beams drive both material tonnage and erection cost, so accurate takeoff of size, length, and connections is central to a structural bid. Estimators price by weight and complexity, meaning beam designation, camber, and connection details directly affect fabrication hours, crane time, and the steel sub's number, with mill lead times also influencing the schedule and cash flow plan.

Example

Taking off the structural steel package, the estimator tallies the W-shape beams by weight per foot from the framing plan and flags long-lead wide-flange sizes that the mill quotes at twelve weeks, affecting the bid schedule.

Related Terms

W-ShapeBeamGirderStructural Steel

Frequently Asked Questions

Steel is priced largely by weight, so estimators sum each member's length times its pounds-per-foot to get tonnage, then add costs for connections, fabrication, coatings, shipping, and erection. Connection complexity and piece count often drive labor more than raw tonnage, so detailing and erection sequence matter as much as weight.
Informally, people say I-beam, but most modern structural steel is the wide-flange W-shape, which has wider, parallel flanges. The older true I-beam (S-shape) has narrower, tapered flanges and is less common. Estimators should price exactly what the framing plan designates, since the shapes differ in weight, availability, and cost.
Wide-flange sections, especially heavy or less common sizes, can carry long mill rolling and fabrication lead times. Estimators must align procurement with the erection schedule and reflect it in the bid, because late steel delays the entire frame and downstream trades, creating both schedule risk and cash flow pressure.

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