Structural Steel (Material)
Rolled and fabricated steel shapes that form the frame of many buildings.
Quick Answer
Structural steel is steel produced in standardized shapes and grades, such as wide-flange beams, channels, angles, and hollow structural sections, and fabricated into the beams, columns, and braces of a building frame. Its high strength-to-weight ratio and predictable behavior let engineers design long spans and tall frames with bolted or welded connections.
The Full Picture
Structural steel is steel made to specifications for load-carrying use in buildings and other structures. It is produced as standard rolled shapes, such as wide-flange (W) sections, channels (C), angles (L), and tees, as hollow structural sections (HSS) in round, square, and rectangular forms, and as plates and built-up members when standard shapes do not suffice.
Material grades are defined by ASTM standards. For example, ASTM A992 is the common specification for wide-flange shapes in buildings, ASTM A500 covers cold-formed HSS, and ASTM A36 is a long-standing plate and shape grade. Grades differ in yield strength, toughness, and weldability, and the structural engineer selects them in the contract documents. Design is governed in the US by the AISC Specification for Structural Steel Buildings.
Pieces become a frame through connections. Bolted connections use high-strength bolts, and welded connections use qualified procedures and welders under AWS requirements. Fabricators detail each piece in shop drawings, cut and drill members in a shop, and ship them for erection, where ironworkers set and connect them with cranes. Fireproofing, corrosion protection, and coordination with decking, studs, and other trades follow.
For preconstruction teams, steel is typically priced by weight, with fabrication and erection often subcontracted, so tonnage, connection complexity, and lead times are important estimating inputs. Mill and fabricator availability can affect the schedule and early procurement decisions.
Real Examples
Common Misconceptions
People assume: Steel does not need fire protection because it is noncombustible.
Actually: Steel loses strength at high temperatures, so many buildings require spray-applied or intumescent fireproofing, or enclosure, to achieve the required fire-resistance rating.
People assume: All structural steel is the same grade.
Actually: Grades differ by yield strength, toughness, and weldability, and the specified ASTM grade must match the shape and the engineer's design.
Frequently Asked Questions
What is the difference between structural steel and rebar?
Structural steel forms the load-carrying frame in shapes such as beams and columns. Rebar is smaller reinforcing bar placed inside concrete to resist tension.
What does A992 mean?
ASTM A992 is a specification for structural steel shapes, widely used for wide-flange beams and columns in buildings, with a minimum yield strength of 50 ksi.
How is structural steel priced?
Generally by weight (tons) for fabricated material, plus detailing, fabrication, delivery, and erection, with connection complexity and market conditions affecting the price.
What is the difference between bolted and welded connections?
Bolted connections use high-strength bolts and are commonly field-assembled. Welded connections fuse members together, often in the shop, and need qualified welders and inspection.