Rwy'n pelydru

Mae dwy ffurf I{0}}beam safonol:

• Rolled I-beam, formed by rholio poeth, rholio oer or allwthio (depending on material).

• Trawstiwr plât, formed by weldio (or occasionally bolltio or rhybed) platiau.

I-beams are commonly made of dur strwythurol but may also be formed from alwminiwm or other materials. A common type of I-beam is the joist dur rholio (RSJ)—sometimes incorrectly rendered as disist dur atgyfnerthu. Prydeinig and safonau Ewropeaidd 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.

Rwy'n-distyllau—I-beams engineered from wood with bwrdd ffibr and/or lumber argaen lamineiddio—are also becoming increasingly popular in construction, especially residential, as they are both lighter and less prone to warping than solid wooden distiau. Fodd bynnag, bu rhywfaint o bryder ynghylch eu colli cryfder yn gyflym mewn tân os nad ydynt yn cael eu diogelu.

Dyluniad ar gyfer plygu 

Y straen mwyaf (${ \displaystyle \sigma _{xx}}$) mewn trawst o dan blygu yn y lleoliadau sydd bellaf o'r echelin niwtral.

A beam under bending sees high stresses along the axial fibers that are farthest from the echel niwtral. Er mwyn atal methiant, rhaid lleoli'r rhan fwyaf o'r deunydd yn y trawst yn y rhanbarthau hyn. Cymharol ychydig o ddeunydd sydd ei angen yn yr ardal sy'n agos at yr echelin niwtral. Yr arsylwad hwn yw sail yr adran I{0}}beam cross-adran; mae'r echelin niwtral yn rhedeg ar hyd canol y we a all fod yn gymharol denau a gellir crynhoi'r rhan fwyaf o'r deunydd yn y flanges.

The ideal beam is the one with the least cross-sectional area (and hence requiring the least material) needed to achieve a given modwlws adran. Since the section modulus depends on the value of the moment o syrthni, rhaid i drawst effeithlon fod â'r rhan fwyaf o'i ddeunydd wedi'i leoli mor bell o'r echelin niwtral â phosib. Po bellaf y daw swm penodol o ddeunydd o'r echelin niwtral, y mwyaf yw'r modwlws adran ac felly gellir gwrthsefyll momentyn plygu mwy.

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 ${ \displaystyle \sigma _{\mathrm {max} }}$ and the maximum expected bending moment is ${ \displaystyle M_{\mathrm {max} }}$, yna rhoddir y modwlws adran ofynnol gan³

• ${ \displaystyle S={\cfrac {M_{\mathrm {max} }}{\sigma _{\mathrm {max} }}}={ \cfrac {I}{c}}}$

where ${ \displaystyle I}$ is the moment of inertia of the beam cross-section and ${ \displaystyle c}$ is the distance of the top of the beam from the neutral axis (see theori trawst for more details).

For a beam of cross-sectional area ${ \arddull arddangos a}$ and height ${ \displaystyle h}$, the ideal cross-section would have half the area at a distance ${\displaystyle h/2}$ above the cross-section and the other half at a distance ${\displaystyle h/2}$ below the cross-section.³ For this cross-section

• ${ \displaystyle I={\cfrac {ah{2}}{4}};S=0.5ah}$

Fodd bynnag, ni ellir byth gyflawni'r amodau delfrydol hyn oherwydd bod angen deunydd yn y we am resymau corfforol, gan gynnwys i wrthsefyll byclo. Ar gyfer trawstiau fflans llydan, mae modwlws yr adran yn fras

• ${\displaystyle S\tua 0.35ah}$

sy'n well na'r hyn a gyflawnir gan drawstiau hirsgwar a thrawstiau crwn.

Materion 

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, trawstiau blwch and other types of stiff sections are used in preference to the I-beam.

Siapiau a deunyddiau (UDA) 

Dur rhychiog rhydlyd I-beam

Yn yr Unol Daleithiau, y -beam I a grybwyllir amlaf yw'r siâp fflans (W) llydan. Mae gan y trawstiau hyn fflansau y mae eu harwynebau mewnol yn gyfochrog dros y rhan fwyaf o'u hardal. Mae trawstiau I{2}}eraill yn cynnwys siapiau American Standard (S dynodedig), lle nad yw arwynebau fflans mewnol yn gyfochrog, a phentyrrau H (HP dynodedig), a ddefnyddir yn nodweddiadol fel sylfeini pentwr. Mae siapiau fflans eang ar gael mewn gradd ASTM A992,⁴ which has generally replaced the older ASTM grades A572 and A36. Ranges of yield strength:

• A36: 36,000 psi (250 MPa)

• A572: 42,000–60,000 psi (290–410 MPa), with 50,000 psi (340 MPa) the most common

• A588: Similar to A572

• A992: 50,000–65,000 psi (340–450 MPa)

Fel y rhan fwyaf o gynhyrchion dur, mae trawstiau I yn aml yn cynnwys rhywfaint o gynnwys wedi'i ailgylchu.

Safonau 

Mae'r safonau canlynol yn diffinio siâp a goddefiannau adrannau dur trawst I-:

Safonau Ewropeaidd 

• EN 10024, Hot rolled taper flange I sections – Tolerances on shape and dimensions.

• EN 10034, Structural steel I and H sections – Tolerances on shape and dimensions.

• EN 10162, Cold rolled steel sections – Technical delivery conditions – Dimensional and cross-sectional tolerances

Llawlyfr AISCgolygu

The Sefydliad Adeiladu Dur America (AISC) publishes the Steel Construction Manual for designing structures of various shapes. It documents the common approaches, Dyluniad Cryfder a Ganiateir (ASD) and Dyluniad Ffactor Llwyth a Gwrthiant (LRFD), (starting with 13th ed.) to create such designs.

Arall 

• DIN 1025-5

• ASTM A6, Trawstiau Safonol Americanaidd

• BS 4-1

• YN 808 – Dimensions hot rolled steel beam, column, channel and angle sections

• AS/NZS 3679.1 – Australia and New Zealand standard⁵

Dynodiad a therminoleg 

Ffans eang I-beam.

• In the Unol Daleithiau, steel I-beams are commonly specified using the depth and weight of the beam. For example, a "W10x22" beam is approximately 10 in (254 mm) 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 22 lb/ft (33 kg/m). Wide flange section beams often vary from their nominal depth. In the case of the W14 series, they may be as deep as 22.84 in (580 mm).⁶

• 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 250 millimetres (9.8 in) 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 33 kg/m (22 lb/ft; 67 lb/yd).⁷ I-beams are still available in U.S. sizes from many Canadian manufacturers.

• In Mecsico, 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 250 mm (9.8 in) 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 33 kg/m (22 lb/ft).⁸

• 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).^{angen dyfyniad}

• In the Deyrnas Unedig, these steel sections are commonly specified with a code consisting of the major dimension (usually the depth){{0}}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 mm (6.0 in) depth 152 mm width and weighing 23 kg/m (46 lb/yd) of length.⁹

• In Awstralia, 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 460 mm (18.1 in) deep universal beam that weighs 67.1 kg/m (135 lb/yd)).⁵

Trawstiau cellog 

Trawstiau cellog are the modern version of the traditional "trawst castellog" which results in a beam approximately 40–60 percent 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.¹⁰