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Properties of Structural Steel for Design and Construction

by TKL Steel January 30, 2021

Structural Steel is used in the construction of different structures. As discussed in the Classification and Uses of Steel blog, there are numerous varieties, depending on its carbon content and other chemical compositions that impacts its properties – strength, hardness, and toughness. There are also different shapes of structural steel, depending on its cross section. Below are some of the common structural steel shapes.


I-beamAn I-shaped cross section with flanges on both side
Z-barHalf a flange going in opposite directions
Angle BarAn L-shaped cross section
T-BarT-shaped cross section
Rectangular BarA rectangular, cross sectioned long piece of steel
RodA round or square long piece of steel


The properties of steel is very important in the design and construction of structures to ensure that the structure will be able to serve its purpose. The most common types of steel properties are tensile strength, hardness, notch toughness, and fatigue stress.

Tensile Strength

Tensile strength of steel is determined by the limit up to which it can be stretched without breaking. Structural steel has high tensile strength and is preferred over other materials for construction. The tensile strength of an alloy is normally measured by putting a test piece in a tensile machine. The tensile machine tries stretching stress by slowly breaking the jaws of the tensile machine. The amount of stretching required to break the test piece is then measured and recorded.


Hardness is the ability of steel to withstand deformation in contrast to tensile strength which determines the ability of a steel structure to resist an applied load without breaking. Hardness also defines several other properties of steel, like resistance to wear, toughness, and formability. There are three different standard tests to evaluate steel hardness, these are the Brinell Test, the Rockwell Test, Knoop Hardness Test and the Vicker Hardness Test.

The Rockwell hardness test is the most frequently used test method since it is easier to execute and more precise compared to other methods. This can be used for all metals except for those materials with indentations or irregular shapes.

The Brinell hardness test is used to test materials with a structure that is too rough or too coarse.

The Vickers Test or the micro hardness test method is used to materials with small parts, thin sections, or case depth work.

Notch Toughness

Notch toughness is the capacity that a steel structure holds to absorb energy in occurrence of a notch or a crack. It is also frequently done at various temperatures since most materials become more fragile as they become colder. This test also helps to know when the brittle transition temperature occurs.

Fatigue strength

Fatigue strength is the maximum strength that a material can tolerate for a given number of cycles without cracking. The amount of cycles that a metal can stand before it breaks is a function of any of the following: static and cyclic stress values, alloy, heat-treatment and surface condition of the material, hardness profile and impurities of the material, kind of load applied, and range of temperature. The highest stress that can be exerted for a certain amount of cycles without fracture is the fatigue strength. Fatigue strength is also identified as endurance strength or fatigue limit.

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