![i-Beam 002](https://upload.wikimedia.org/wikipedia/commons/4/40/I-Beam_002.JPG)
An I-beam, also known as H-beam (for universal column, UC), w-beam (for "wide flange"), universal beam (UB), rolled steel joist (RSJ), or double-T (especially in
Polish
Polish may refer to:
* Anything from or related to Poland, a country in Europe
* Polish language
* Poles, people from Poland or of Polish descent
* Polish chicken
*Polish brothers (Mark Polish and Michael Polish, born 1970), American twin screenwr ...
,
Bulgarian
Bulgarian may refer to:
* Something of, from, or related to the country of Bulgaria
* Bulgarians, a South Slavic ethnic group
* Bulgarian language, a Slavic language
* Bulgarian alphabet
* A citizen of Bulgaria, see Demographics of Bulgaria
* Bul ...
,
Spanish
Spanish might refer to:
* Items from or related to Spain:
**Spaniards are a nation and ethnic group indigenous to Spain
**Spanish language, spoken in Spain and many Latin American countries
**Spanish cuisine
Other places
* Spanish, Ontario, Cana ...
,
Italian
Italian(s) may refer to:
* Anything of, from, or related to the people of Italy over the centuries
** Italians, an ethnic group or simply a citizen of the Italian Republic or Italian Kingdom
** Italian language, a Romance language
*** Regional Ita ...
and
German
German(s) may refer to:
* Germany (of or related to)
**Germania (historical use)
* Germans, citizens of Germany, people of German ancestry, or native speakers of the German language
** For citizens of Germany, see also German nationality law
**Ger ...
), is a
beam
Beam may refer to:
Streams of particles or energy
*Light beam, or beam of light, a directional projection of light energy
**Laser beam
*Particle beam, a stream of charged or neutral particles
**Charged particle beam, a spatially localized grou ...
with an or -shaped
cross-section
Cross section may refer to:
* Cross section (geometry)
** Cross-sectional views in architecture & engineering 3D
*Cross section (geology)
* Cross section (electronics)
* Radar cross section, measure of detectability
* Cross section (physics)
**Ab ...
. The horizontal elements of the are
flange
A flange is a protruded ridge, lip or rim (wheel), rim, either external or internal, that serves to increase shear strength, strength (as the flange of an iron beam (structure), beam such as an I-beam or a T-beam); for easy attachment/transfer of ...
s, and the vertical element is the "web". I-beams are usually made of
structural steel
Structural steel is a category of 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, ...
and are used in construction and civil engineering.
The web resists
shear forces
In solid mechanics, shearing forces are unaligned forces acting on one part of a Rigid body, body in a specific direction, and another part of the body in the opposite direction. When the forces are collinear (aligned with each other), they ...
, while the flanges resist most of the bending moment experienced by the beam. The
Euler–Bernoulli beam equation shows that the I-shaped section is a very efficient form for carrying both
bending
In applied mechanics, bending (also known as flexure) 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 ...
and
shear
Shear may refer to:
Textile production
*Animal shearing, the collection of wool from various species
**Sheep shearing
*The removal of nap during wool cloth production
Science and technology Engineering
*Shear strength (soil), the shear strength ...
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 may refer to:
Science
* Torsion (mechanics), the twisting of an object due to an applied torque
* Torsion of spacetime, the field used in Einstein–Cartan theory and
** Alternatives to general relativity
* Torsion angle, in chemistry
Bi ...
, for which
hollow structural section
A hollow structural section (HSS) is a type of metal profile with a hollow cross section. The term is used predominantly in the United States, or other countries which follow US construction or engineering terminology.
HSS members can be circu ...
s are often preferred.
History
The method of producing an I-beam, as rolled from a single piece of wrought iron, was patented by Alphonse Halbou of the company ''
Forges de la Providence
Forges de la Providence was a Belgian steel producing company based in the Hainaut (province), Hainaut region around Charleroi. Founded as ''Société Anonyme des laminoirs, forges, fonderies et usines de la Providence'' the company had three steel ...
'' in 1849.
Bethlehem Steel
The Bethlehem Steel Corporation was an American steelmaking company headquartered in Bethlehem, Pennsylvania. For most of the 20th century, it was one of the world's largest steel producing and shipbuilding companies. At the height of its succe ...
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 cross-sections.
Overview
![Ibeam](https://upload.wikimedia.org/wikipedia/commons/e/e6/Ibeam.svg)
There are two standard I-beam forms:
* Rolled I-beam, formed by
hot rolling
In metalworking, rolling is a metal forming process in which metal stock is passed through one or more pairs of rolls to reduce the thickness, to make the thickness uniform, and/or to impart a desired mechanical property. The concept is simil ...
,
cold rolling
In metalworking, rolling is a metal forming process in which metal stock is passed through one or more pairs of rolls to reduce the thickness, to make the thickness uniform, and/or to impart a desired mechanical property. The concept is simil ...
or
extrusion
Extrusion is a process used to create objects of a fixed cross-sectional profile by pushing material through a die of the desired cross-section. Its two main advantages over other manufacturing processes are its ability to create very complex c ...
(depending on material).
*
Plate girder
A plate girder bridge is a bridge supported by two or more plate girders.
Overview
In a plate girder bridge, the plate girders are typically I-beams made up from separate structural steel plates (rather than rolled as a single cross-section), ...
, formed by
welding
Welding is a fabrication (metal), fabrication process that joins materials, usually metals or thermoplastics, by using high heat to melt the parts together and allowing them to cool, causing Fusion welding, fusion. Welding is distinct from lower ...
(or occasionally
bolting or
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 to the head is called the ''tail''. On installation, the rivet is placed in a punched ...
ing) plates.
I-beams are commonly made of
structural steel
Structural steel is a category of 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, ...
but may also be formed from
aluminium
Aluminium (aluminum in American and Canadian English) is a chemical element with the symbol Al and atomic number 13. Aluminium has a density lower than those of other common metals, at approximately one third that of steel. I ...
or other materials. A common type of I-beam is the ''rolled steel joist'' (RSJ)—sometimes incorrectly rendered as ''reinforced steel joist''.
British
British may refer to:
Peoples, culture, and language
* British people, nationals or natives of the United Kingdom, British Overseas Territories, and Crown Dependencies.
** Britishness, the British identity and common culture
* British English, ...
and
European standards
European Standards (abbreviated EN, from the German name ("European Norm")) are technical standards which have been ratified by one of the three European standards organizations: European Committee for Standardization (CEN), European Committee for ...
also specify Universal Beams (UBs) and Universal Columns (UCs). These sections have parallel flanges, as opposed to the varying thickness of RSJ flanges which are seldom now rolled in the UK. Parallel flanges are easier to connect to and do away with the need for tapering washers. UCs have equal or near-equal width and depth and are more suited to being oriented vertically to carry axial load such as columns in multi-storey construction, while UBs are significantly deeper than they are wide are more suited to carrying bending load such as beam elements in floors.
I-joist
An engineered wood joist, more commonly known as an I-joist, is a product designed to eliminate problems that occur with conventional wood joists. Invented in 1969, the I-joist is an engineered wood product that has great strength in relation to ...
s—I-beams engineered from wood with
fiberboard
Fiberboard (American English) or fibreboard (British English) is a type of engineered wood product that is made out of wood fibers. Types of fiberboard (in order of increasing density) include particle board or low-density fiberboard (LDF), medi ...
and/or
laminated veneer lumber
Laminated veneer lumber (LVL) is an engineered wood product that uses multiple layers of thin wood assembled with adhesives. It is typically used for headers, beams, rimboard, and edge-forming material. LVL offers several advantages over typi ...
—are also becoming increasingly popular in construction, especially residential, as they are both lighter and less prone to warping than solid wooden
joist
A joist is a horizontal structural member used in framing to span an open space, often between beams that subsequently transfer loads to vertical members. When incorporated into a floor framing system, joists serve to provide stiffness to the s ...
s. However, there has been some concern as to their rapid loss of strength in a fire if unprotected.
Design
![Beam mode 2](https://upload.wikimedia.org/wikipedia/commons/7/76/Beam_mode_2.gif)
I-beams are widely used in the
construction industry
Construction is a general term meaning the art and science to form objects, systems, or organizations,"Construction" def. 1.a. 1.b. and 1.c. ''Oxford English Dictionary'' Second Edition on CD-ROM (v. 4.0) Oxford University Press 2009 and come ...
and are available in a variety of standard sizes. Tables are available to allow easy selection of a suitable steel I-beam size for a given applied load. I-beams may be used both as beams and as
column
A column or pillar in architecture and structural engineering is a structural element that transmits, through compression, the weight of the structure above to other structural elements below. In other words, a column is a compression member. ...
s.
I-beams may be used both on their own, or acting
compositely with another material, typically
concrete
Concrete is a composite material composed of fine and coarse aggregate bonded together with a fluid cement (cement paste) that hardens (cures) over time. Concrete is the second-most-used substance in the world after water, and is the most wi ...
. Design may be governed by any of the following criteria:
*
deflection
Deflection or deflexion may refer to:
Board games
* Deflection (chess), a tactic that forces an opposing chess piece to leave a square
* Khet (game), formerly ''Deflexion'', an Egyptian-themed chess-like game using lasers
Mechanics
* Deflection ...
: the
stiffness
Stiffness is the extent to which an object resists deformation in response to an applied force.
The complementary concept is flexibility or pliability: the more flexible an object is, the less stiff it is.
Calculations
The stiffness, k, of a b ...
of the I-beam will be chosen to minimize deformation
*
vibration
Vibration is a mechanical phenomenon whereby oscillations occur about an equilibrium point. The word comes from Latin ''vibrationem'' ("shaking, brandishing"). The oscillations may be periodic function, periodic, such as the motion of a pendulum ...
: the stiffness and
mass
Mass is an intrinsic property of a body. It was traditionally believed to be related to the quantity of matter in a physical body, until the discovery of the atom and particle physics. It was found that different atoms and different elementar ...
are chosen to prevent unacceptable vibrations, particularly in settings sensitive to vibrations, such as offices and libraries
* bending failure by
yielding: where the
stress
Stress may refer to:
Science and medicine
* Stress (biology), an organism's response to a stressor such as an environmental condition
* Stress (linguistics), relative emphasis or prominence given to a syllable in a word, or to a word in a phrase ...
in the cross section exceeds the
yield stress
In materials science and engineering, the yield point is the point on a stress-strain curve that indicates the limit of elastic behavior and the beginning of plastic behavior. Below the yield point, a material will deform elastically and wi ...
* 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
Shear may refer to:
Textile production
* Animal shearing, the collection of wool from various species
**Sheep shearing
*The removal of nap during wool cloth production
Science and technology Engineering
* Shear strength (soil), the shear streng ...
: 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 I-beam's web.
Design for bending
![Poutre flexion deviee](https://upload.wikimedia.org/wikipedia/commons/c/cf/Poutre_flexion_deviee.svg)
A beam under bending sees high stresses along the axial fibers that are farthest from the
neutral axis
The neutral axis is an axis in the cross section of a beam (a member resisting bending) 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 neu ...
. 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 I-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 is a geometric property for a given cross-section used in the design of beams or flexural members. Other geometric properties used in design include area for tension and shear, radius of gyration for compression, and second moment ...
. Since the section modulus depends on the value of the
moment of inertia
The moment of inertia, otherwise known as the mass moment of inertia, angular mass, second moment of mass, or most accurately, rotational inertia, of a rigid body is a quantity that determines the torque needed for a desired angular acceler ...
, 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 I-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 of the beam cross-section and is the distance of the top of the beam from the neutral axis (see
beam theory
Beam may refer to:
Streams of particles or energy
*Light beam, or beam of light, a directional projection of light energy
**Laser beam
*Particle beam, a stream of charged or neutral particles
**Charged particle beam, a spatially localized grou ...
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.
[Gere and Timoshenko, 1997, ''Mechanics of Materials'', PWS Publishing Company.] 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 I-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 are used in preference to the I-beam.
Shapes and materials (U.S.)
![Rostiger Stahltraeger](https://upload.wikimedia.org/wikipedia/commons/1/1d/Rostiger_Stahltraeger.jpg)
In the United States, the most commonly mentioned I-beam is the wide-flange (W) shape. These beams have flanges whose inside surfaces are parallel over most of their area. Other I-beams include American Standard (designated S) shapes, in which inner 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:
* A572: , with the most common
* A588: Similar to A572
* A992:
Like most steel products, I-beams often contain some recycled content.
Standards
The following standards define the shape and tolerances of I-beam steel sections:
European Standards
*
EN 10024
En or EN may refer to:
Businesses
* Bouygues (stock symbol EN)
* Esquimalt and Nanaimo Railway (reporting mark EN, but now known as Southern Railway of Vancouver Island)
* Euronews, a news television and internet channel
Language and writing
* E ...
, Hot rolled taper flange I sections – Tolerances on shape and dimensions.
*
EN 10034
The EN 10034 "Structural steel I and H sections. Tolerances on shape and dimensions" is a European Standard.
The standard is developed by the technical committee ECISS/TC 103 - Structural steels other than reinforcements.
See also
* I-beam
...
, Structural steel I and H sections – Tolerances on shape and dimensions.
*
EN 10162
En or EN may refer to:
Businesses
* Bouygues (stock symbol EN)
* Esquimalt and Nanaimo Railway (reporting mark EN, but now known as Southern Railway of Vancouver Island)
* Euronews, a news television and internet channel
Language and writing
* E ...
, Cold rolled steel sections – Technical delivery conditions – Dimensional and cross-sectional tolerances
AISC Manual
The
American Institute of Steel Construction
The American Institute of Steel Construction (AISC) is a not-for-profit technical institute and trade association
A trade association, also known as an industry trade group, business association, sector association or industry body, is an or ...
(AISC) publishes the Steel Construction Manual for designing structures of various shapes. It documents the common approaches,
Allowable Strength Design {{unreferenced, date=March 2010
Allowable Strength Design (ASD) is a term used by the American Institute of Steel Construction (AISC) in the 14th Edition of the Manual of Steel Construction.
Allowable Stress Design philosophy was left unsupported ...
(ASD) and
Load and Resistance Factor Design (LRFD), (starting with 13th ed.) to create such designs.
Other
*
DIN 1025-5
DIN or Din or din may refer to:
People and language
* Din (name), people with the name
* Dīn, an Arabic word with three general senses: judgment, custom, and religion from which the name originates
* Dinka language (ISO 639 code: din), spoken by ...
*
ASTM A6
ASTM International, formerly known as American Society for Testing and Materials, is an international standards organization that develops and publishes voluntary consensus technical standards for a wide range of materials, products, systems, a ...
, American Standard Beams
*
BS 4-1
BS, B.S., Bs or bs may refer to:
Arts and entertainment
*BS-, a prefix for all games broadcast for the Satellaview modem via the Japanese Broadcasting Satellite system
* "B.S." (song), a song by Jhené Aiko from the album ''Chilombo''
*Team BS, ...
*
IS 808
In linguistics, a copula (plural: copulas or copulae; abbreviated ) is a word or phrase that links the subject of a sentence to a subject complement, such as the word ''is'' in the sentence "The sky is blue" or the phrase ''was not being'' i ...
– Dimensions hot rolled steel beam, column, channel and angle sections
*
AS/NZS 3679.1 – Australia and New Zealand standard
[Hot rolled and structural steel products – Fifth edition]
— Onesteel
Arrium was an Australian mining and materials company, employing nearly 10,000 workers,
that went into voluntary administration in 2016 with debts of more than $2 billion. In 2017 it was acquired by British-owned Liberty House Group.
Hist ...
. Retrieved 18 December 2015.
Designation and terminology
![i-BeamCrossSection](https://upload.wikimedia.org/wikipedia/commons/0/09/I-BeamCrossSection.svg)
* In the United States, steel I-beams are commonly specified using the depth and weight of the beam. For example, a "W10x22" beam is approximately in depth (nominal height of the I-beam from the outer face of one flange to the outer face of the other flange) and weighs . Wide flange section beams often vary from their nominal depth. In the case of the W14 series, they may be as deep as .
* In Canada, steel I-beams are now commonly specified using the depth and weight of the beam in metric terms. For example, a "W250x33" beam is approximately in depth (height of the I-beam from the outer face of one flange to the outer face of the other flange) and weighs approximately . I-beams are still available in U.S. sizes from many Canadian manufacturers.
* In Mexico, steel I-beams are called IR and commonly specified using the depth and weight of the beam in metric terms. For example, a "IR250x33" beam is approximately in depth (height of the I-beam from the outer face of one flange to the outer face of the other flange) and weighs approximately .
* In India I-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, and 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).
* 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 depth 152 mm width and weighing of 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 approximate height of the beam, the type (beam or column) and then the unit metre rate (e.g., a 460UB67.1 is an approximately deep universal beam that weighs ).
Cellular beams
Cellular beam
Cellular beam is a further development of the traditional castellated beam. The advantage of the steel beam castellation process is that it increases strength without adding weight, making both versions an inexpensive solution to achieve maximum ...
s are the modern version of the traditional "
castellated beam
A castellated beam is a Beam (structure), beam style where an I-beam is subjected to a Longitude, longitudinal cut along its web following a specific pattern.
The purpose is to divide and reassemble the beam with a deeper web by taking advantag ...
" 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.
See also
*
Canadian Institute of Steel Construction
Canadians (french: Canadiens) are people identified with the country of Canada. This connection may be residential, legal, historical or cultural. For most Canadians, many (or all) of these connections exist and are collectively the source of ...
* C-beam, also known as a
structural channel
The structural channel, also known as a C-channel or Parallel Flange Channel (PFC), is a type of (usually structural steel) beam, used primarily in building construction and civil engineering. Its cross section consists of a wide "web", usually ...
or Parallel Flange Channel (PFC)
*
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:
* DIN 1025-1
DIN or Din or din may refer to:
People and language
* Din (name), people with the na ...
– a DIN standard which defines the dimensions, masses and sectional properties of a set of I-beams
*
Open web steel joist
In structural engineering, the open web steel joist (OWSJ) is a lightweight steel truss consisting, in the standard form, of parallel chords and a triangulated web system, proportioned to span between bearing points.
The main function of an OWS ...
*
Reinforced concrete
Reinforced concrete (RC), also called reinforced cement concrete (RCC) and ferroconcrete, is a composite material in which concrete's relatively low tensile strength and ductility are compensated for by the inclusion of reinforcement having hig ...
*
Steel design
Steel Design, or more specifically, Structural Steel Design, is an area of structural engineering used to design steel structures. These structures include schools, houses, bridges, commercial centers, tall buildings, warehouses, aircraft, ships ...
*
Structural angle
Structural steel is a category of 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 ...
*
T-beam
A T-beam (or tee beam), used in construction, is a load-bearing structure of reinforced concrete, wood or metal, with a -shaped cross section. The top of the -shaped cross section serves as a flange or compression member in resisting compress ...
*
Weld access hole
The weld access hole or rat hole is a structural engineering technique in which a part of the web of an I-beam or T-beam is cut out at the end or ends of the beam. The hole in the web allows a welder to weld the flange to another part of the str ...
References
Further reading
* {{Cite book , last=Ashby , first=M. F. , year=2005 , title=Materials Selection in Mechanical Design , edition=3rd , location=Oxford; Boston , publisher=Elsevier Butterworth-Heinemann , isbn=9780750661683 See chapter 8, sections 8.4 ("Floor joists: wood or steel?") and 8.5 ("Increasing the stiffness of the steel sheet").
External links
Canadian Institute of Steel Construction websiteAmerican Institute of Steel Construction websiteMexican Institute of Steel Construction websiteBritish Constructional Steelwork Association website
1849 introductions
Structural engineering
Structural steel