I-beam
Overview
 
-beams, also known as H-beams, W-beams (for "wide flange"), rolled steel joist (RSJ), or double-T (especially in Polish
Polish language
Polish is a language of the Lechitic subgroup of West Slavic languages, used throughout Poland and by Polish minorities in other countries...

, Spanish
Spanish language
Spanish , also known as Castilian , is a Romance language in the Ibero-Romance group that evolved from several languages and dialects in central-northern Iberia around the 9th century and gradually spread with the expansion of the Kingdom of Castile into central and southern Iberia during the...

 and German
German language
German is a West Germanic language, related to and classified alongside English and Dutch. With an estimated 90 – 98 million native speakers, German is one of the world's major languages and is the most widely-spoken first language in the European Union....

) are beams
Beam (structure)
A beam is a horizontal structural element that is capable of withstanding load primarily by resisting bending. The bending force induced into the material of the beam as a result of the external loads, own weight, span and external reactions to these loads is called a bending moment.- Overview...

 with an - or H-shaped cross-section
Cross section (geometry)
In geometry, a cross-section is the intersection of a figure in 2-dimensional space with a line, or of a body in 3-dimensional space with a plane, etc...

. The horizontal elements of the "" are flange
Flange
A flange is an external or internal ridge, or rim , for strength, as the flange of an iron beam such as an I-beam or a T-beam; or for attachment to another object, as the flange on the end of a pipe, steam cylinder, etc., or on the lens mount of a camera; or for a flange of a rail car or tram wheel...

s, while the vertical element is the web. The web resists shear forces while the flanges resist most of the bending moment experienced by the beam. Beam theory
Euler-Bernoulli beam equation
Euler–Bernoulli beam theory is a simplification of the linear theory of elasticity which provides a means of calculating the load-carrying and deflection characteristics of beams. It covers the case for small deflections of a beam which is subjected to lateral loads only...

 shows that the -shaped section is a very efficient form for carrying both bending
Bending
In engineering mechanics, bending characterizes the behavior of a slender structural element subjected to an external load applied perpendicularly to a longitudinal axis of the element. The structural element is assumed to be such that at least one of its dimensions is a small fraction, typically...

 and shear
Shearing (physics)
Shearing in continuum mechanics refers to the occurrence of a shear strain, which is a deformation of a material substance in which parallel internal surfaces slide past one another. It is induced by a shear stress in the material...

 loads in the plane of the web.
Encyclopedia
-beams, also known as H-beams, W-beams (for "wide flange"), rolled steel joist (RSJ), or double-T (especially in Polish
Polish language
Polish is a language of the Lechitic subgroup of West Slavic languages, used throughout Poland and by Polish minorities in other countries...

, Spanish
Spanish language
Spanish , also known as Castilian , is a Romance language in the Ibero-Romance group that evolved from several languages and dialects in central-northern Iberia around the 9th century and gradually spread with the expansion of the Kingdom of Castile into central and southern Iberia during the...

 and German
German language
German is a West Germanic language, related to and classified alongside English and Dutch. With an estimated 90 – 98 million native speakers, German is one of the world's major languages and is the most widely-spoken first language in the European Union....

) are beams
Beam (structure)
A beam is a horizontal structural element that is capable of withstanding load primarily by resisting bending. The bending force induced into the material of the beam as a result of the external loads, own weight, span and external reactions to these loads is called a bending moment.- Overview...

 with an - or H-shaped cross-section
Cross section (geometry)
In geometry, a cross-section is the intersection of a figure in 2-dimensional space with a line, or of a body in 3-dimensional space with a plane, etc...

. The horizontal elements of the "" are flange
Flange
A flange is an external or internal ridge, or rim , for strength, as the flange of an iron beam such as an I-beam or a T-beam; or for attachment to another object, as the flange on the end of a pipe, steam cylinder, etc., or on the lens mount of a camera; or for a flange of a rail car or tram wheel...

s, while the vertical element is the web. The web resists shear forces while the flanges resist most of the bending moment experienced by the beam. Beam theory
Euler-Bernoulli beam equation
Euler–Bernoulli beam theory is a simplification of the linear theory of elasticity which provides a means of calculating the load-carrying and deflection characteristics of beams. It covers the case for small deflections of a beam which is subjected to lateral loads only...

 shows that the -shaped section is a very efficient form for carrying both bending
Bending
In engineering mechanics, bending characterizes the behavior of a slender structural element subjected to an external load applied perpendicularly to a longitudinal axis of the element. The structural element is assumed to be such that at least one of its dimensions is a small fraction, typically...

 and shear
Shearing (physics)
Shearing in continuum mechanics refers to the occurrence of a shear strain, which is a deformation of a material substance in which parallel internal surfaces slide past one another. It is induced by a shear stress in the material...

 loads in the plane of the web. On the other hand, the cross-section has a reduced capacity in the transverse direction, and is also inefficient in carrying torsion
Torsion (mechanics)
In solid mechanics, torsion is the twisting of an object due to an applied torque. In sections perpendicular to the torque axis, the resultant shear stress in this section is perpendicular to the radius....

, for which hollow structural section
Hollow structural section
A hollow structural section is a type of metal profile with a hollow tubular cross section. In some countries they are referred to instead as a structural hollow section ....

s are often preferred.

Overview

There are two standard I-beam forms:
  • Rolled -beam, formed by hot rolling, cold rolling or extrusion
    Extrusion
    Extrusion is a process used to create objects of a fixed cross-sectional profile. A material is pushed or drawn through a die of the desired cross-section...

     (depending on material).
  • Plate girder, formed by welding
    Welding
    Welding is a fabrication or sculptural process that joins materials, usually metals or thermoplastics, by causing coalescence. This is often done by melting the workpieces and adding a filler material to form a pool of molten material that cools to become a strong joint, with pressure sometimes...

     (or occasionally bolting or rivet
    Rivet
    A rivet is a permanent mechanical fastener. Before being installed a rivet consists of a smooth cylindrical shaft with a head on one end. The end opposite the head is called the buck-tail. On installation the rivet is placed in a punched or pre-drilled hole, and the tail is upset, or bucked A rivet...

    ing) plates.


-beams are commonly made of structural steel
Structural steel
Structural steel is steel construction material, a profile, formed with a specific shape or cross section and certain standards of chemical composition and mechanical properties...

 but may also be formed from aluminium
Aluminium
Aluminium or aluminum is a silvery white member of the boron group of chemical elements. It has the symbol Al, and its atomic number is 13. It is not soluble in water under normal circumstances....

 or other materials. A common type of -beam is the rolled steel joist (RSJ)—sometimes incorrectly rendered as reinforced steel joist. British and European standard
European Committee for Standardization
The European Committee for Standardization or Comité Européen de Normalisation , is a non-profit organisation whose mission is to foster the European economy in global trading, the welfare of European citizens and the environment by providing an efficient infrastructure to interested parties for...

s also specify Universal Beams (UBs) and Universal Columns (UCs). These sections have parallel flanges, as opposed to the varying thickness of RSJ flanges. UCs have equal or near-equal width and depth, while UBs are significantly deeper than they are wide.

-beams engineered from wood with fiberboard
Fiberboard
Fiberboard is known as low density fiberboard is a type of engineered wood product that is made out of wood fibers. Types of fiberboard include particle board, medium-density fiberboard, and hardboard. Fiberboard is sometimes used as a synonym for particle board, but particle board usually refers...

 and/or laminated veneer lumber
Laminated veneer lumber
Laminated veneer lumber is an engineered wood product that uses multiple layers of thin wood assembled with adhesives. It offers several advantages over typical milled lumber: it is stronger, straighter, and more uniform. It is much less likely than conventional lumber to warp, twist, bow, or...

 are also becoming increasingly popular in construction, especially residential, as they are both lighter and less prone to warping than solid wooden joist
Joist
A joist, in architecture and engineering, is one of the horizontal supporting members that run from wall to wall, wall to beam, or beam to beam to support a ceiling, roof, or floor. It may be made of wood, steel, or concrete. Typically, a beam is bigger than, and is thus distinguished from, a joist...

s. However there has been some concern as to their rapid loss of strength in a fire if unprotected.

Design

-beams are widely used in the construction industry and are available in a variety of standard sizes. Tables are available to allow easy selection of a suitable steel -beam size for a given applied load. -beams may be used both as beams and as column
Column
A column or pillar in architecture and structural engineering is a vertical structural element that transmits, through compression, the weight of the structure above to other structural elements below. For the purpose of wind or earthquake engineering, columns may be designed to resist lateral forces...

s.

-beams may be used both on their own, or acting compositely
Composite material
Composite materials, often shortened to composites or called composition materials, are engineered or naturally occurring materials made from two or more constituent materials with significantly different physical or chemical properties which remain separate and distinct at the macroscopic or...

 with another material, typically concrete
Concrete
Concrete is a composite construction material, composed of cement and other cementitious materials such as fly ash and slag cement, aggregate , water and chemical admixtures.The word concrete comes from the Latin word...

. Design may be governed by any of the following criteria:
  • deflection
    Deflection (engineering)
    In engineering, deflection is the degree to which a structural element is displaced under a load. It may refer to an angle or a distance.The deflection distance of a member under a load is directly related to the slope of the deflected shape of the member under that load and can be calculated by...

    : the stiffness
    Stiffness
    Stiffness is the resistance of an elastic body to deformation by an applied force along a given degree of freedom when a set of loading points and boundary conditions are prescribed on the elastic body.-Calculations:...

     of the -beam will be chosen to minimize deformation
  • vibration
    Vibration
    Vibration refers to mechanical oscillations about an equilibrium point. The oscillations may be periodic such as the motion of a pendulum or random such as the movement of a tire on a gravel road.Vibration is occasionally "desirable"...

    : the stiffness and mass
    Mass
    Mass can be defined as a quantitive measure of the resistance an object has to change in its velocity.In physics, mass commonly refers to any of the following three properties of matter, which have been shown experimentally to be equivalent:...

     are chosen to prevent unacceptable vibrations, particularly in settings sensitive to vibrations, such as offices and libraries
  • bending failure by yielding
    Yield (engineering)
    The yield strength or yield point of a material is defined in engineering and materials science as the stress at which a material begins to deform plastically. Prior to the yield point the material will deform elastically and will return to its original shape when the applied stress is removed...

    : where the stress
    Stress (physics)
    In continuum mechanics, stress is a measure of the internal forces acting within a deformable body. Quantitatively, it is a measure of the average force per unit area of a surface within the body on which internal forces act. These internal forces are a reaction to external forces applied on the body...

     in the cross section exceeds the yield stress
  • bending failure by lateral torsional buckling: where a flange in compression tends to buckle sideways or the entire cross-section buckles torsionally
  • bending failure by local buckling: where the flange or web is so slender as to buckle locally
  • local yield: caused by concentrated loads, such as at the beam's point of support
  • shear failure: where the web fails. Slender webs will fail by buckling, rippling in a phenomenon termed tension field action, but shear failure is also resisted by the stiffness of the flanges
  • buckling or yielding of components: for example, of stiffeners used to provide stability to the -beam's web.

Design for bending

A beam under bending sees high stresses along the axial fibers that are farthest from the neutral axis
Neutral axis
The neutral axis is an axis in the cross section of a beam or shaft along which there are no longitudinal stresses or strains. If the section is symmetric, isotropic and is not curved before a bend occurs, then the neutral axis is at the geometric centroid...

. To prevent failure, most of the material in the beam must be located in these regions. Comparatively little material is needed in the area close to the neutral axis. This observation is the basis of the -beam cross-section; the neutral axis runs along the center of the web which can be relatively thin and most of the material can be concentrated in the flanges.

The ideal beam is the one with the least cross-sectional area (and hence requiring the least material) needed to achieve a given section modulus
Section modulus
Section modulus is a geometric property for a given cross-section often used in the design of beams or flexural members. There are two types of section moduli, the elastic section modulus and the plastic section modulus .- Notation :...

. Since the section modulus depends on the value of the moment of inertia, an efficient beam must have most of its material located as far from the neutral axis as possible. The farther a given amount of material is from the neutral axis, the larger is the section modulus and hence a larger bending moment can be resisted.

When designing a symmetric -beam to resist stresses due to bending the usual starting point is the required section modulus. If the allowable stress is and the maximum expected bending moment is , then the required section modulus is given by
where is the moment of inertia
Moment of inertia
In classical mechanics, moment of inertia, also called mass moment of inertia, rotational inertia, polar moment of inertia of mass, or the angular mass, is a measure of an object's resistance to changes to its rotation. It is the inertia of a rotating body with respect to its rotation...

 of the beam cross-section and is the distance of the top of the beam from the neutral axis (see beam theory for more details).

For a beam of cross-sectional area and height , the ideal cross-section would have half the area at a distance above the cross-section and the other half at a distance below the cross-section For this cross-section
However, these ideal conditions can never be achieved because material is needed in the web for physical reasons, including to resist buckling. For wide-flange beams, the section modulus is approximately
which is superior to that achieved by rectangular beams and circular beams.

Issues

Though -beams are excellent for unidirectional bending in a plane parallel to the web, they do not perform as well in bidirectional bending. These beams also show little resistance to twisting and undergo sectional warping under torsional loading. For torsion dominated problems, box beams and other types of stiff sections perform better.

Wide-flange steel materials and rolling processes (U.S.)

In the United States, the most commonly mentioned -beam is the wide-flange (W) shape. These beams have flanges in which the planes are nearly parallel. Other -beams include American Standard (designated S) shapes, in which flange surfaces are not parallel, and H-piles (designated HP), which are typically used as pile foundations. Wide-flange shapes are available in grade ASTM A992, which has generally replaced the older ASTM grades A572 and A36. Ranges of yield strength:
  • A36: 36,000 psi
    Pounds per square inch
    The pound per square inch or, more accurately, pound-force per square inch is a unit of pressure or of stress based on avoirdupois units...

     (250 MPa)
  • A572: 42,000–60,000 psi (290–410 MPa), but 50,000 psi (340 MPa) is the most common
  • A588: Similar to A572
  • A992: 50,000–65,000 psi (340–450 MPa)


Like most steel products, -beams often contain some recycled content.

The American Institute of Steel Construction ("AISC") publishes the "Steel Construction Manual" for designing structures of various shapes. It documents the common approaches, ASD and LRFD, (as of 13th ed.) to creating such designs.

Designation and terminology

  • In the United States, steel -beams are commonly specified using the depth and weight of the beam. For example, a "W10x22" beam is approximately 10 inches (25.4 cm) in depth (height when the -beam is standing on its flanges) and weighs approximately 22 lb/ft (33 kg/m).

  • In Canada, steel -beams are now commonly specified using the depth and weight of the beam in metric terms. For example, a "W250x33" beam is approximately 250 millimetres (9.8 in) in depth (height when the -beam is standing on its flanges) and weighs approximately 33 kg/m (22 lb/ft). -beams are still available in U.S. sizes from many Canadian manufacturers.

  • In India -beams are designated as ISMB, ISJB, ISLB, ISWB. ISMB :Indian Standard Medium Weight Beam, ISJB : Indian Standard Junior Beams, ISLB : Indian Standard Light Weight Beams, ISWB : Indian Standard Wide Flange Beams. Beams are designated as per respective abbreviated reference followed by the depth of section such as for example ISMB 450, where 450 is the depth of section in millimetres (mm). The dimensions of these beams are classified as per IS:808. (as per BIS
    Bureau of Indian Standards
    The Bureau of Indian Standards is the national Standards Body of India working under the aegis of Ministry of Consumer Affairs, Food & Public Distribution, Government of India. It is established by the Bureau of Indian Standards Act, 1986 which came into effect on 23 December 1986...

    )

  • In the United Kingdom, these steel sections are commonly specified with a code consisting of the major dimension (usually the depth)-x-the minor dimension-x-the mass per metre-ending with the section type, all measurements being metric. Therefore a 152x152x23UC would be a column section (UC = universal column) of approximately 152 millimetres (6 in) depth 152 millimetres (6 in) width and weighing 23 kg per meter length.

  • In Australia, these steel sections are commonly referred to as Universal Beams (UB) or Columns (UC). The designation for each is given as the height of the beam, the type (beam or column) and then the unit metre rate (e.g., a 460UB67 is a 460 millimetres (18.1 in) deep universal beam that weighs 67 kg/m)

Indian standard beams ISMB

Type
Beam
height
(mm)
Flange
width
(mm)
Web
thickness
(mm)
Flange
thickness
(mm)
Weight
(kg/m)
Cross-section
area
(cm2)
Moment of inertia
in torsion (J)
(cm4)
ISMB 80 80 46 3.8 5.2 6.0 7.64 0.70
ISMB 100 100 55 4.1 5.7 8.1 10.3 1.10
ISMB 120 120 70 4.4 6.3 10.4 13.2 1.71
ISMB 140 140 73 4.7 6.9 12.9 16.4 2.54
ISMB 750 x 137 753 263 11.5 17 137 175 137.1
ISMB 750 x 147 753 265 13.2 17 147 188 161.5
ISMB 750 x 173 762 267 14.4 21.6 173 221 273.6
ISMB 750 x 196 770 268 15.6 25.4 196 251 408.9

European wide flange beams HEA and HEB

Type
Beam
height
(mm)
Flange
width
(mm)
Web
thickness
(mm)
Flange
thickness
(mm)
Weight
(kg/m)
Cross-section
area
(cm2)
Moment of inertia
in torsion (J)
(cm4)
HE 100 A 96 100 5 8 16.7 21.2 5.24
HE 120 A 114 120 5 8 19.9 25.3 5.99
HE 140 A 133 140 5.5 8.5 24,7 31.4 8.13
HE 160 A 152 160 6 9 30.4 38.8 12.19
HE 1000 x 415 1020 304 26 46 415 528.7 2714
HE 1000 x 438 1026 305 26.9 49 437 557.2 3200
HE 1000 x 494 1036 309 31 54 494 629.1 4433
HE 1000 x 584 1056 314 36 64 584 743.7 7230

Cellular beams

Cellular beams are the modern version of the traditional ‘castellated’ beam which results in a beam approximately 40-60% deeper than its parent section. The exact finished depth, cell diameter and cell spacing are flexible. A cellular beam is up to 1.5 times stronger than its parent section and is therefore utilized to create efficient large span constructions.

History

The method of producing an -beam, as rolled from a single piece of steel, was patented by Alphonse Halbou of the company Forges de la Providence
Forges de la Providence
Forges de la Providence was a Belgian steel producing company based in the Hainaut region around Charleroi. Founded as Société Anonyme des laminoirs, forges, fonderies et usines de la Providence the company had three steel production sites at Marchienne-au-Pont in Belgium, and Réhon and Hautmont in...

in 1849.

Bethlehem Steel
Bethlehem Steel
The Bethlehem Steel Corporation , based in Bethlehem, Pennsylvania, was once the second-largest steel producer in the United States, after Pittsburgh, Pennsylvania-based U.S. Steel. After a decline in the U.S...

's Bethlehem plant was famous for its Gray mill and the wide-flange shapes that that mill was good at rolling. The steel was hot rolled to make the beams. Bethlehem was a leading supplier of rolled structural steel of various cross-sections in American bridge and skyscraper work of the mid-twentieth century. Today, rolled cross-sections have been partially displaced in such work by fabricated
Fabrication (metal)
Fabrication as an industrial term refers to building metal structures by cutting, bending, and assembling. The cutting part of fabrication is via sawing, shearing, or chiseling ; torching with handheld torches ; and via CNC cutters...

 cross-sections.

See also

  • DIN 1025
    DIN 1025
    DIN 1025 is a DIN standard which defines the dimensions, masses and sectional properties of hot rolled I-beams.The standard is divided in 5 parts:...

    , a DIN
    Din
    DIN or Din or din can have several meanings:* A din is a loud noise.* Dīn, an Arabic term meaning "religion" or "way of life".* Din is one of the ten aspects of the Ein Sof in Kabbalah ....

     standard which defines the dimensions, masses and sectional properties of a set of I-beams
  • T-beam
    T-beam
    A T-beam, used in construction, is a load-bearing structure of reinforced concrete, wood or metal, with a t-shaped cross section. The top of the t-shaped cross section serves as a flange or compression member in resisting compressive stresses...

  • I-joist
    I-joist
    An engineered wood joist, more commonly known as an I-joist, is a product designed to eliminate many of the problems that occur with using conventional wood joists. Invented in 1969, the I-joist is a man made engineered wood product which has incredible strength in relation to its size and weight...

  • Open web steel joist
    Open web steel joist
    In structural engineering, the Open Web Steel Joist is a lightweight steel truss consisting, in the standard form, of parallel chords and a triangulated web system, proportioned to span between bearing points....

  • Reinforced concrete
    Reinforced concrete
    Reinforced concrete is concrete in which reinforcement bars , reinforcement grids, plates or fibers have been incorporated to strengthen the concrete in tension. It was invented by French gardener Joseph Monier in 1849 and patented in 1867. The term Ferro Concrete refers only to concrete that is...

  • Weld access hole‎

External links

The source of this article is wikipedia, the free encyclopedia.  The text of this article is licensed under the GFDL.
 
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