Structural steel is steel used for making construction materials in a variety of shapes. Many structural steel shapes take the form of an elongated beam having a profile of a specific cross section. Structural steel shapes, sizes, chemical composition, mechanical properties such as strengths, storage practices, etc., are regulated by standards in most industrialized countries. Structural steel is usually used in a system of interconnected members that are fixed together to carry loads in order to meet a specific need. Structural steel shapes, such as I-beams, have high second moments of area, so can support a high load without excessive sagging.
Structural shapes The shapes available are described in published standards worldwide, and specialist, proprietary cross sections are also available.
I-beam (serif capital 'I'-shaped cross-section – in Britain these include Universal Beams (UB) and Universal Columns (UC); in Europe it includes the IPE, HE, HL, HD and other sections; in the US it includes Wide Flange (WF or W-Shape) and H sections) Z-Shape (half a flange in opposite directions) HSS-Shape (Hollow structural section also known as SHS (structural hollow section) and including square, rectangular, circular (pipe) and elliptical cross sections) Angle (L-shaped cross-section) Structural channel, C-beam, or 'C' cross-section Tee (T-shaped cross-section) Bar, with a rectangular cross section, but not so wide so as to be called a sheet. Rod, a round or square section long compared to its width. Plate, metal sheets thicker than 6 mm or 1⁄4 in. Open web steel joist Sections can be hot or cold rolled, or fabricated by welding together flat or bent plates.
The terms angle iron, channel iron, and sheet iron have been in common use since before wrought iron was replaced by steel for commercial purposes and are still often used. In technical writing angle stock, channel stock, and sheet are often used instead of those misnomers.
Standards
Europe Most steels used in Europe are specified to comply with EN 10025. However, some national standards remain in force. Example grades are S275J2 or S355K2W where S denotes structural steel; 275 or 355 denotes the yield strength in newtons per square millimetre or the equivalent megapascals; J2 or K2 denotes the material's toughness by Charpy impact test values, and the W denotes weathering steel. Further letters can be used to designate fine grain steel (N or NL); quenched and tempered steel (Q or QL); and thermomechanically rolled steel (M or ML). Common yield strengths available are 195, 235, 275, 355, 420, and 460, although some grades are more commonly used than others. In the UK, almost all structural steel is S275 and S355. Higher grades such as 500, 550, 620, 690, 890 and 960 available in quenched and tempered material although grades above 690 receive little if any use in construction at present. Euronorms define the shape of standard structural profiles:
European I-beam: IPE – Euronorm 19-57 European I-beam: IPN – DIN 1025-1 European flange beams: HE – Euronorm 53-62 European channels: UPN – DIN 1026-1 European cold formed IS IS 800-1
US Steels used for building construction in the US use standard alloys identified and specified by ASTM International. These steels have an alloy identification beginning with A and then two, three, or four numbers. The four-number AISI steel grades commonly used for mechanical engineering, machines, and vehicles are a completely different specification series. The standard commonly used structural steels are:
Carbon steels A36 – structural shapes and plate. A53 – structural pipe and tubing. A500 – structural pipe and tubing. A501 – structural pipe and tubing. A529 – structural shapes and plate. A1085 – structural pipe and tubing.
High strength low alloy steels A441 – structural shapes and plates (Superseded by A572) A572 – structural shapes and plates. A618 – structural pipe and tubing. A992 – Possible applications are W or S I-Beams. A913 – Quenched and Self Tempered (QST) W shapes. A270 – structural shapes and plates.
Corrosion resistant high strength low alloy steels A243 – structural shapes and plates. A588 – structural shapes and plates.
Quenched and tempered alloy steels A514 – structural shapes and plates. A517 – boilers and pressure vessels. Eglin steel – Inexpensive aerospace and weaponry items.
Forged steel A668 – Steel Forgings
CE marking The concept of CE marking for all construction products and steel products is introduced by the Construction Products Directive (CPD). The CPD is a European Directive that ensures the free movement of all construction products within the European Union. Because steel components are "safety critical", CE Marking is not allowed unless the Factory Production Control (FPC) system under which they are produced has been assessed by a suitable certification body that has been approved to the European Commission. In the case of steel products such as sections, bolts and fabricated steelwork the CE Marking demonstrates that the product complies with the relevant harmonized standard. For steel structures the main harmonized standards are:
Steel sections and plate – EN 10025-1 Hollow sections – EN 10219-1 and EN 10210-1 Pre-loadable bolts – EN 14399-1 Non-preloadable bolts – EN 15048-1 Fabricated steel – EN 1090 −1 The standard that covers CE Marking of structural steelwork is EN 1090-1. The standard has come into force in late 2010. After a transition period of two years, CE Marking will become mandatory in most European Countries sometime early in 2012. The official end date of the transition period is July 1, 2014
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