Structural Steel
Fabricated steel shapes that form a building's frame.
Quick Answer
Structural steel is steel formed into standard shapes, such as wide-flange beams, columns, channels, angles, and hollow structural sections, that are fabricated and connected to frame buildings and bridges. It has a high strength-to-weight ratio, is made to tight tolerances in a shop, and is erected quickly with bolted or welded connections.
The Full Picture
Structural steel framing is built from standardized rolled shapes, primarily wide-flange (W) sections for beams and columns, plus channels, angles, plates, and hollow structural sections (HSS). Fabricators cut, drill, weld, and coat these members in the shop according to detailed shop drawings, then deliver them to the site for erection.
Steel buildings typically combine a gravity system of beams, girders, and columns supporting composite metal deck and concrete topping, with a lateral system of braced frames or moment frames. Connections, which are bolted or welded, are a key design item because they must transfer forces reliably and be practical for the erector to install.
In the United States, design is governed by the AISC Specification for Structural Steel Buildings (AISC 360), which the building code adopts. Fabrication and erection quality are covered by AISC certification programs and the Code of Standard Practice. Corrosion protection and fire protection, usually spray-applied or intumescent, are separate scopes that must be coordinated.
For contractors, steel is a long-lead, schedule-critical package. Mill and fabricator capacity, shop drawing review, detailing time, and market price swings all influence cost and timing. Estimators typically price steel by weight from takeoffs of members and connections, and clarify who is responsible for items such as embeds, anchor bolts, deck, shear studs, and miscellaneous metals.
Real Examples
Common Misconceptions
People assume: Steel does not need fire protection because it does not burn.
Actually: Steel loses strength at high temperatures, so many buildings require fireproofing or fire-rated assemblies to meet the code's required fire-resistance ratings.
People assume: The steel price is just the weight times a price per ton.
Actually: Pricing also reflects fabrication complexity, connections, finish, deck, miscellaneous metals, detailing, delivery, and erection, and varies with the market.
Frequently Asked Questions
What are the common structural steel shapes?
Wide-flange (W) beams and columns, channels (C), angles (L), tees, plates, and hollow structural sections (HSS), which are round, square, or rectangular tubes.
What is the difference between structural steel and rebar?
Structural steel forms the framing of a structure by itself, while rebar is smaller steel reinforcement embedded in concrete to carry tension.
What standards govern structural steel buildings?
AISC 360 covers design, and AISC 303 covers fabrication and erection practice. Material standards come from ASTM, and the building code adopts these by reference.
Why is steel considered a long-lead item?
Because mill supply, fabrication, and shop drawing approval can take months, so steel is often procured early to protect the construction schedule.