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Blog Task 3- Cross sectional shapes for steel beams and columns

Lead author: Hanyue Hu

Beams are characterized by the shape of their cross-section, their length and material. In contemporary construction, beams are typically made of steel, reinforced concrete, wood or composites. One of the most common types of steel beam is I-beam.

I-beam

photo

I-beam is also known as the H- beam, Universal Beam and column. It is a beam with I or H shaped cross section. The horizontal elements of the “I” are flanges, which resist most of bending moment, and the vertical element is called the “web”, which resists shear forces. I beam is very good for carrying both bending and shear loads; however, its cross-section has a reduced capacity in the transverse direction. It is inefficient in carrying torsion, so that the hollow structural sections are preferred instead.

Hollow structural section (HSS-Shape)

HSS

A hollow structural section is a type of metal block with a hollow tubular cross section including square, rectangular, circular and elliptical cross sections. It is commonly available in mild steel.

Rectangular sections are commonly used in welded steel frames for experiencing loads in multiple directions. Square and circular sections are used for columns because they have very efficient shapes for the multiple-axis loading, as they have uniform geometry along two or more cross-sectional axes.  The square and circular sections are also good in resisting torsion. HSS can also be used as beams as it has superior resistance to lateral torsional buckling.

T-beam 

T-beam

A T-beam is a load-bearing structure of metal with a t-shaped cross section. The top of the cross section acts as a flange in resisting compressive stress. The web of the beam below the compression flange resists shear stress and provides greater separation for the coupled forces of bending.T beam is mainly used in construction.

Compare to I-beam, T-beam has a disadvantage to deal with tensile forces because it does not have a bottom flange. To make it more efficient, an inverted T-beam can be joined with a floor slab or bridge deck. By joining the top of the beams, the slab can act as the compression flange.

Z-beam

Z-beam

Z-beam is a beam with half a flange in opposite directions. It is commonly made of steel strips and is characterised by its high resistance to corrosion. Z type beam load cells combine both a compact form and high precision to produce a superior tension force transducer.

Angle (L-shaped cross-section)

L-jbeam

L beams are commonly used as floor beams because of the reduced overall structual depth. L beams only receive the loads from one side, so they hold considerable amount of torsional moments.

Channel, or C section, (C-shaped cross-section)

C-beam

Parallel Flange Channel (PFC): they have C shaped cross section and parallel inner flange surfaces.

Taper Flange Channel (CH): They are very similar to PFCs but have a slope on the inner flange surfaces.

C shape channel are usful in places where a single flat face without outstanding flanges on one side is required. However, it is inefficient to use it as a beam/column on its own. To improve its efficiency, C shaped beams can be supported using other structual shapes.

C steel beams are commonly used for roof purling. They are easy to install and theyhave good anti-bending performance and good straightness.

Asymmetric beams

Asymmetric beams

Asymmetric beams are produced by hot rolling in which the degree of asymmetry between the widths of the top and bottom flanges is approximately 60%, normally between 280 and 300mm deep. The pattern on the top flange binds with the surrounding concrete which saves the time of welding shear stud connectors on the top of a beam.

Asymmetric I-beams

The rail profile is the cross sectional shape of a railway rail which has a specific cross sectional profile – an asymmetrical I-beam design for use as the main component of railway track.

Research reference

http://www.structural-drafting-net-expert.com/steel-beam.html

http://wenku.baidu.com/view/21fd8681d0d233d4b14e6977.html

http://www.fgg.uni-lj.si/kmk/esdep/master/wg14/l1000.htm

http://en.wikipedia.org/wiki/I-beam

 

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