I-raġġ

Hemm żewġ forom standard ta' I-raġġ:

• Rolled I-beam, formed by rolling bis-sħana, rolling kiesaħ or estrużjoni (depending on material).

• Trave tal-pjanċa, formed by iwweldjar (or occasionally bolting or irbattar) pjanċi.

I-beams are commonly made of azzar strutturali but may also be formed from aluminju or other materials. A common type of I-beam is the travu tal-azzar irrumblat (RSJ)—sometimes incorrectly rendered as travu rinfurzat tal-azzar. Brittaniċi and standards Ewropej 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-joists—I-beams engineered from wood with bord tal-fibra and/or injam laminat tal-fuljetta—are also becoming increasingly popular in construction, especially residential, as they are both lighter and less prone to warping than solid wooden travi. Madankollu, kien hemm xi tħassib dwar it-telf rapidu tagħhom ta 'saħħa f'nar jekk mhux protetti.

Disinn għall-liwi 

L-akbar tensjonijiet (${\displaystyle \sigma _{xx}}$) f'raġġ taħt liwi huma fil-postijiet l-aktar 'il bogħod mill-assi newtrali.

A beam under bending sees high stresses along the axial fibers that are farthest from the assi newtrali. Biex tevita l-falliment, ħafna mill-materjal fir-raġġ għandu jkun jinsab f'dawn ir-reġjuni. Komparattivament ftit huwa meħtieġ materjal fiż-żona qrib l-assi newtrali. Din l-osservazzjoni hija l-bażi tas-sezzjoni trasversali ta' I-raġġ-; l-assi newtrali jimxi tul iċ-ċentru tal-web li jista 'jkun relattivament irqiq u ħafna mill-materjal jista' jiġi kkonċentrat fil-flanġijiet.

The ideal beam is the one with the least cross-sectional area (and hence requiring the least material) needed to achieve a given modulu tas-sezzjoni. Since the section modulus depends on the value of the mument ta' inerzja, raġġ effiċjenti għandu jkollu ħafna mill-materjal tiegħu jinsab kemm jista 'jkun 'il bogħod mill-assi newtrali. Iktar ma jkun ’il bogħod ammont partikolari ta’ materjal mill-assi newtrali, iktar ikun kbir il-modulu tas-sezzjoni u għalhekk jista’ jiġi rreżistit mument ta’ liwi akbar.

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 ${\displaystyle \sigma _{\mathrm {mass} }}$ and the maximum expected bending moment is ${\displaystyle M_{\mathrm {mass} }}$, allura l-modulu tas-sezzjoni meħtieġ huwa mogħti minn³

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

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 teorija tar-raġġ 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

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

Madankollu, dawn il-kundizzjonijiet ideali qatt ma jistgħu jinkisbu minħabba li l-materjal huwa meħtieġ fil-web għal raġunijiet fiżiċi, inkluż biex jirreżisti l-buckling. Għal travi ta'-flanġ wiesa', il-modulu tas-sezzjoni huwa bejn wieħed u ieħor

• ${\displaystyle S\madwar 0.35ah}$

li huwa superjuri għal dak miksub minn travi rettangolari u travi ċirkolari.

Kwistjonijiet 

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, travi tal-kaxxa and other types of stiff sections are used in preference to the I-beam.

Forom u materjali (US) 

Azzar irbattut Rusty I-raġġ

Fl-Istati Uniti, l-aktar komunement imsemmi I-raġġ huwa l-forma wiesgħa-flanġ (W). Dawn it-travi għandhom flanġijiet li l-uċuħ ta 'ġewwa tagħhom huma paralleli fuq il-biċċa l-kbira taż-żona tagħhom. Travi I-oħra jinkludu forom American Standard (magħżula S), li fihom l-uċuħ tal-flanġ ta' ġewwa mhumiex paralleli, u munzelli H- (magħmula HP), li huma tipikament użati bħala pedamenti tal-pil. Forom ta' flanġ wiesgħa- huma disponibbli fil-grad 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)

Bħal ħafna mill-prodotti tal-azzar, it-travi I-spiss ikun fihom xi kontenut riċiklat.

Standards 

L-istandards li ġejjin jiddefinixxu l-forma u t-tolleranzi tas-sezzjonijiet tal-azzar tar-raġġ I-:

Standards Ewropej 

• 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

Manwal AISCeditja

The Istitut Amerikan tal-Kostruzzjoni tal-Azzar (AISC) publishes the Steel Construction Manual for designing structures of various shapes. It documents the common approaches, Disinn ta 'Qawwa Permessi (ASD) and Disinn tal-Fattur tat-Tagħbija u tar-Reżistenza (LRFD), (starting with 13th ed.) to create such designs.

Oħrajn 

• DIN 1025-5

• ASTM A6, Travi Standard Amerikani

• BS 4-1

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

• AS/NZS 3679.1 – Australia and New Zealand standard⁵

Denominazzjoni u terminoloġija 

Flanġ wiesa'-I-raġġ.

• In the Stati Uniti, 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 Messiku, 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 Indja 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).^{ċitazzjoni meħtieġa}

• In the Ir-Renju Unit, 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 Awstralja, 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

Travi ċellulari 

Travi ċellulari are the modern version of the traditional "travu castellated" 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