aš-spindu

Yra dvi standartinės I-spindulio formos:

• Rolled I-beam, formed by karštas valcavimas, šaltas valcavimas or išspaudimas (depending on material).

• Plokštinė sija, formed by suvirinimas (or occasionally varžtais or kniedijimas) lėkštės.

I-beams are commonly made of konstrukcinis plienas but may also be formed from aliuminio or other materials. A common type of I-beam is the valcuoto plieno sija (RSJ)—sometimes incorrectly rendered as sustiprinta plieno sija. britų and Europos standartai 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-sijos—I-beams engineered from wood with medienos plaušų plokštės and/or laminuota lukšto mediena—are also becoming increasingly popular in construction, especially residential, as they are both lighter and less prone to warping than solid wooden sijos. Tačiau buvo susirūpinta dėl greito jų jėgų praradimo gaisro atveju, jei jie nėra apsaugoti.

Konstrukcija lenkimui 

Didžiausi įtempimai (${\displaystyle \sigma _{xx}}$) lenktoje sijoje yra tose vietose, kurios yra toliausiai nuo neutralios ašies.

A beam under bending sees high stresses along the axial fibers that are farthest from the neutrali ašis. Siekiant išvengti gedimų, didžioji dalis sijos medžiagos turi būti šiose srityse. Srityje, esančioje arti neutralios ašies, reikia palyginti mažai medžiagos. Šis stebėjimas yra I-sijos skerspjūvio-pagrindas; neutrali ašis eina išilgai juostos centro, kuris gali būti palyginti plonas, o didžioji dalis medžiagos gali būti sutelkta flanšuose.

The ideal beam is the one with the least cross-sectional area (and hence requiring the least material) needed to achieve a given sekcijos modulis. Since the section modulus depends on the value of the inercijos momentas, efektyvaus pluošto didžioji dalis medžiagos turi būti kuo toliau nuo neutralios ašies. Kuo toliau nuo neutralios ašies yra tam tikras medžiagos kiekis, tuo didesnis yra sekcijos modulis, todėl galima atsispirti didesniam lenkimo momentui.

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 ${\displaystyle M_{\mathrm {max} }}$, tada reikiamas atkarpos modulis pateikiamas pagal³

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

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 sijos teorija for more details).

For a beam of cross-sectional area ${\displaystyle a}$ 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

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

Tačiau šių idealių sąlygų niekada nepavyks pasiekti, nes žiniatinklyje medžiagos reikia dėl fizinių priežasčių, įskaitant atsparumą lenkimui. Plačios{0}}jungės sijos profilio modulis yra apytikslis

• ${\displaystyle S\approx 0.35ah}$

kuri yra pranašesnė už pasiektą stačiakampėmis ir apskritomis sijomis.

Problemos 

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

Formos ir medžiagos (JAV) 

Surūdijusi kniedyta plieninė I-sija

Jungtinėse Amerikos Valstijose dažniausiai minima I-sija yra plataus-jungės (W) forma. Šios sijos turi flanšus, kurių vidiniai paviršiai yra lygiagretūs didžiojoje jų ploto dalyje. Kitos I-sijos yra Amerikos standartinės (žymimos S) formos, kuriose vidiniai flanšo paviršiai nėra lygiagretūs, ir H-poliai (žymimi HP), kurie paprastai naudojami kaip poliniai pamatai. Platus-jungės formos yra ASTM A992 klasės,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)

Kaip ir daugumoje plieno gaminių, I{0}}sijose dažnai yra perdirbto turinio.

Standartai 

Šie standartai apibrėžia I{0}}sijos plieninių profilių formą ir leistinus nuokrypius:

Europos standartai 

• 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

AISC vadovasRedaguoti

The Amerikos plieno konstrukcijos institutas (AISC) publishes the Steel Construction Manual for designing structures of various shapes. It documents the common approaches, Leidžiamo stiprumo dizainas (ASD) and Apkrovos ir pasipriešinimo faktoriaus dizainas (LRFD), (starting with 13th ed.) to create such designs.

Kita 

• DIN 1025-5

• ASTM A6, Amerikos standartinės sijos

• BS 4-1

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

• AS/NZS 3679,1 – Australia and New Zealand standard⁵

Pavadinimas ir terminija 

Platus-flanšas I-sija.

• In the Jungtinės Valstijos, 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 Kanada, 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 Meksika, 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 Indija 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).^{reikalinga citata}

• In the Jungtinė Karalystė, 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 Australija, 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

Korinio ryšio sijos 

Korinio ryšio sijos are the modern version of the traditional "kasteliuotas sija" 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