-žarim

Obstajata dve standardni obliki I-snopa:

• Rolled I-beam, formed by vroče valjanje, hladno valjanje or ekstrudiranje (depending on material).

• Ploščati nosilec, formed by varjenje (or occasionally privijanje or kovičenje) plošče.

I-beams are commonly made of konstrukcijsko jeklo but may also be formed from aluminij or other materials. A common type of I-beam is the valjani jekleni nosilec (RSJ)—sometimes incorrectly rendered as ojačan jekleni nosilec. Britanci and evropski standardi 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-tramovi—I-beams engineered from wood with vlaknene plošče and/or laminiran les—are also becoming increasingly popular in construction, especially residential, as they are both lighter and less prone to warping than solid wooden tramovi. Vendar pa obstaja nekaj skrbi glede njihove hitre izgube moči v požaru, če niso zaščitene.

Dizajn za upogibanje 

Največji stresi (${\displaystyle \sigma _{xx}}$) v upogibnem nosilcu so na mestih, ki so najbolj oddaljena od nevtralne osi.

A beam under bending sees high stresses along the axial fibers that are farthest from the nevtralna os. Da bi preprečili okvaro, mora biti večina materiala v žarku nameščena v teh regijah. Na območju blizu nevtralne osi je potrebno razmeroma malo materiala. To opazovanje je osnova za prerez I-snopa-; nevtralna os poteka vzdolž središča traku, ki je lahko razmeroma tanka in večina materiala je lahko koncentrirana v prirobnicah.

The ideal beam is the one with the least cross-sectional area (and hence requiring the least material) needed to achieve a given modul preseka. Since the section modulus depends on the value of the vztrajnostni moment, mora imeti učinkovit žarek večino materiala čim dlje od nevtralne osi. Dlje kot je določena količina materiala od nevtralne osi, večji je modul preseka in zato se je mogoče upreti večjemu upogibnemu momentu.

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 ${\displaystyle M_{\mathrm {max}}}$, potem je zahtevani modul preseka podan z³

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

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 žarka 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

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

Vendar teh idealnih pogojev ni mogoče nikoli doseči, ker je material potreben v spletu iz fizičnih razlogov, vključno z odpornostjo na upogibanje. Pri širokih-prirobnih nosilcih je modul preseka približno

• ${\displaystyle S\približno 0.35ah}$

kar je boljše od tistega, ki ga dosežejo pravokotni in krožni tramovi.

Težave 

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

Oblike in materiali (ZDA) 

Zarjavel zakovičen jekleni I{0}} žarek

V Združenih državah je najpogosteje omenjen I-žarek široka-prirobnica (W). Ti nosilci imajo prirobnice, katerih notranje površine so vzporedne na večini njihove površine. Drugi I- nosilci vključujejo ameriške standardne (označene S) oblike, pri katerih notranje prirobne površine niso vzporedne, in H- pilote (označene HP), ki se običajno uporabljajo kot temelji pilotov. Široke-oblike prirobnic so na voljo v razredu 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)

Kot večina jeklenih izdelkov, I-tramovi pogosto vsebujejo nekaj reciklirane vsebine.

Standardi 

Naslednji standardi opredeljujejo obliko in tolerance jeklenih profilov I{0}}:

evropski standardi 

• 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

Priročnik AISCUredi

The Ameriški inštitut za jeklene konstrukcije (AISC) publishes the Steel Construction Manual for designing structures of various shapes. It documents the common approaches, Zasnova dovoljene trdnosti (ASD) and Oblikovanje faktorja obremenitve in upora (LRFD), (starting with 13th ed.) to create such designs.

Drugo 

• DIN 1025-5

• ASTM A6, ameriški standardni nosilci

• BS 4-1

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

• AS/NZS 3679.1 – Australia and New Zealand standard⁵

Poimenovanje in terminologija 

Širok -prirobniček I- žarek.

• In the Združene države, 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 Mehika, 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).^{potreben navedba}

• In the Združeno kraljestvo, 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 Avstralija, 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

Celični žarki 

Celični žarki are the modern version of the traditional "kastelirani žarek" 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