Structural steel is steel construction material a Profile (engineering) formed with a specific shape or cross section (geometry) and certain standards of Chemistry and mechanical properties. Structural steel shape, size, composition, strength, storage, etc., is regulated in most industrialized countries. Structural steel members, such as I-beams, have high Second moment of area which allow them to be very stiff in respect to their cross-sectional area. Image:I-Beam 002.JPG in this case used to support wood beams in a house.]] Image:Struc steel.jpg A primed steel beam is holding up the floor above, which consists of a metal deck (Q-Deck), upon which a concrete slab has been poured.]] Image:Steel beam penetration.jpg beam through-penetration with incomplete fireproofing.]] Image:Owsj deck fireproofing.jpg deck and OWSJ (Open Web Steel Joist), receiving first coat of spray fireproofing plaster made of polystyrene leavened gypsum ]]

Common structural shapes

lt;!-- This section is linked from Meccano --> In most Developed country the shapes available are set out in published standards, although a number of specialist and proprietary Cross section (geometry) are also available. *I-beam (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) 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 (geometry) rectangle circular (pipe (material) and ellipse Cross section (geometry) *Angle (L-shaped cross-section) *Channel ( -shaped cross-section) *Tee (T-shaped cross-section) *Rail profile (asymmetrical I-beam) **Rail tracks#Rail **Vignoles rail **Flanged T rail **Tramway track#Grooved rail *Bar, a piece of metal rectangle Cross section (geometry) (flat) and long, but not so wide so as to be called a Sheet metal *Rod, a Circle or Square (geometry) and long piece of metal or wood see also rebar and dowel *Plate, sheet metal thicker than 6 mm or 1/4 in. *Open web steel joist While many sections are made by Hot rolling or Cold rolling rolling (metalworking) others are made by weld ng together flat or bent plates (for example, the largest circular hollow sections are made from flat plate bent into a circle and seam-welded).

Standards

Standard structural steels (Europe)

Most steels used throughout Europe are specified to comply with the European Committee for Standardization EN 10025. However, many national standards also remain in force. Typical grades are described as S275J2 or S355K2W. In these examples, S denotes structural rather than engineering steel; 275 or 355 denotes the yield strength in newtons per square millimetre or the equivalent megapascal ; J2 or K2 denotes the materials toughness by reference to Charpy impact test values; and the W denotes Cor-ten Further letters can be used to designate Normalization (metallurgy) steel (N or NL); quench steel (Q or QL); and thermomechanically rolled steel (M or ML). The normal yield strength grades available are 195, 235, 275, 355, 420, and 460, although some grades are more commonly used than others e.g. in the UK, almost all structural steel is grades S275 and S355. Higher grades are available in quenched and tempered material (500, 550, 620, 690, 890 and 960 - although grades above 690 receive little if any use in construction at present).

Standard structural steels (USA)

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:Manual of Steel Construction, 8th Edition 2nd revised printing, American Institute of Steel Construction, 1987, ch 1 page 1-5

Carbon steels

* A36 steel - structural shapes and plate * A53 steel - structural pipe and tubing * A500 steel - structural pipe and tubing * A501 steel - structural pipe and tubing * A529 steel - structural shapes and plate

High strength low alloy steels

* A441 steel - structural shapes and plates * A572 steel - structural shapes and plates * A618 steel - structural pipe and tubing * A992 steel - W shapes beams only * A270 steel - structural shapes and plates

Corrosion resistant high strength low alloy steels

* A242 - structural shapes and plates * Weathering steel - structural shapes and plates

Quenched and tempered alloy steels

* A514 steel - structural shapes and plates * A514 steel#A517 - boilers and pressure vessels

Steel vs. concrete

As raw material prices fluctuate, often so does building design. During times of lower steel prices, more steel and less concrete is used, and vice versa. Each set of vendors and users typically maintain national industry associations that advocate the use of its materials versus the other. However, both materials are typically used together. Concrete without steel reinforcement (usually ribbed round bars called Rebar crumbles under tensile loads. Steel on its own, without composite or reinforced concrete floors, is likewise not a preferred building method. While rebar is almost always steel, it is not considered a structural steel and is described separately in the Rebar and Reinforced concrete articles. While both steel structures and Reinforced concrete cement(R.C.C)structures have their pros and cons,the steel structures have better strength to weight ratio than RCC, and can be easily dismantled(Steel structures,which have bolted connections can also be reused to some extent after dismantling).

Thermal properties

The properties of steel vary widely, depending on its alloying elements. The austenizing temperature, the temperature where a steel transforms to an austenite crystal structure, for steel starts at 900°C for pure iron, then, as more carbon is added, the temperature falls to a minimum 724°C for eutectic steel (steel with only .83% by weight of carbon in it). As 2.1% carbon (by mass is approached, the austenizing temperature climbs back up, to 1130°C. Similarly, the melting point of steel changes based on the alloy. The lowest temperature at which a plain carbon steel can begin to melt, its solidus is 1130 °C. Steel never turns into a liquid below this temperature. Pure Iron (Steel with 0% Carbon) starts to melt at 1492 °C (2720 °F), and is completely liquid upon reaching 1539 °C (2802 °F). Steel with 2.1% Carbon by weight begins melting at 1130 °C (2066 °F), and is completely molten upon reaching 1315 °C (2400 °F). Steel with more than 2.1% Carbon is no longer Steel, but is known as Cast iron http://www.msm.cam.ac.uk/phase-trans/images/FeC.gif

Fireproofing of structural steel

In order for a fireproofing product to qualify for a certification listing of structural steel, through a fire test the critical temperature is set by the national standard, which governs the test. In Japan this is below 400°C. In China Europe and North America it is set at 540°C. The time it takes for the steel element that is being tested to reach the temperature set by the national standard determines the duration of the fire-resistance rating Care must be taken to ensure that thermal expansion of structural elements does not damage fire-resistance rating wall and floor assemblies. Penetrant in a Firewall (construction) and ferrous cable tray in organic firestop should be installed in accordance with an appropriate certification listing that complies with the local building code Open Web Steel Joists (OWSJ) require a great deal of spray fireproofing because they are not very massive and also because they are so open, that a lot of the sprayed plaster flies right past its constituent parts during the coating process. Structural steel requires external insulation (fireproofing) in order to prevent the steel from weakening in the event of a fire. When heated, steel expands and softens, eventually losing its structural integrity. Given enough energy, it can also melt. Heat transfer to the steel can be slowed by the use of fireproofing materials While concrete structures that comprise buildings are able to achieve fire-resistance ratings without additional fireproofing, concrete can be subject to severe spalling, particularly if it has an elevated moisture content. Fireproofing is available for concrete but this is typically not used in buildings. Instead, it is used in traffic tunnels and locations where a hydrocarbon fire is likely to break out. Thus, steel and concrete compete against one another not only on the basis of the price per unit of mass but also on the basis of the pricing for the fireproofing that must be added in order to satisfy the passive fire protection requirements that are mandated through building code . Common fireproofing methods for structural steel include intumescent endothermic and plaster coatings as well as drywall calcium silicate cladding, and mineral or high temperature insulation wool in the form of blanket.

See also

*Diamond plate *Dowel#Stone masonry *Drywall *Endothermic *Fireproofing *Flame cleaning *Flanged T rail *Tramway track#Grooved rail *Hollow structural section *Open web steel joist *Intumescent *Passive fire protection *Penetrant *Profile (engineering) *Rail tracks#Railway rail *Rebar *Structural engineering *Structural shape rolling *Vignoles rail

References

External links

*http://www.aisc.org/ The American Institute of Steel Construction, Inc.] *http://cic.nist.gov/vrml/cis2.html Product Data Standards for Structural Steel (CIS/2, IFC)] The product data standards facilitate interoperability between CAD software. SteelVis is visualization software for CIS/2 files. *http://www.ironworkers.org International Association of Bridge, Structural, Ornamental, and Reinforcing Iron Workers] Category:Structural engineering Category:Steels de:Baustahl es:Acero laminado fi:Rakenneteräs it:Acciaio strutturale pt:Cantoneira sl:Konstrukcijsko jeklo sv:Konstruktionsstål