Structural steel is steel construction material, it is a profile formed with specific shapes or cross sections and specific standards of chemical composition and mechanical properties.  Structural steel shape, size, strength, composition etc is regulated in most industrialised countries. For example, structural steel sections such as I-beams have high second moments of area, this allows them to be very stiff in respect to their cross sectional area. In most of the developed countries, the shapes available for steel structures are set out in published standards as well as a number of specialist and proprietary cross sections are also available for the erection of specific steel structures.
Steel structures incorporate the following sections where necessary:

• I beam – This is an I shaped cross section
• Z Shape – Half a flange in opposite directions
• Structural hollow section which includes shapes square, rectangular, circular and elliptical.
• Angle – This is an l-shaped cross section
• Structural channel
• Tee – t-shaped cross section
• Rail profile -  asymmetrical I-beam
• Bar – a piece of metal, rectangular cross section (flat) and long, but not so wide as to be considered a sheet.
• Rod – a round or square long piece of metal
• Plate – metal sheets that are thicker than 6mm
• While many steel structure sections are made by hot or cold rolling, others are made by welding together flat or bent plates.  The largest circular hollow sections are made from flat plate bent into a circle and seam welded.