Structural steel is a very important building material which is used in structural members such as beam, column and footings.
I will describe all the important things related to structural steel.
Lets start!
Table of Contents
What Is Structural Steel?
Structural steel is a special type of metal that is used in building construction, as well as in infrastructure projects like bridges and tunnels, and pre-engineered buildings like warehouses and factories.
It is a strong and durable material that provides the necessary support and strength needed for such structures to withstand heavy loads and remain standing.
Chemical Composition Of Structural Steel
The chemical composition of Structural Steel plays a vital role in determining its mechanical properties and performance. The primary elements that are added to Structural Steel to improve its properties are carbon, chromium, manganese, aluminum, copper, sulphur, phosphorus, and molybdenum.
Carbon is the most crucial chemical ingredient in Structural Steel. The carbon concentration in the steel can significantly influence its mechanical properties. As the carbon content increases, the steel’s strength increases while its flexibility decreases.
Chromium is another element that is added to Structural Steel to enhance its corrosion resistance. When combined with copper and nickel, small amounts of chromium can significantly increase the steel’s resistance to corrosion.
Manganese is used as a neutralizer during the hot rolling of Structural Steel. It has properties similar to carbon and can affect the material’s mechanical properties. Manganese also improves the steel’s hardenability and wear resistance.
Aluminum is an essential deoxidizer that contributes to the formation of a finer-grained crystalline microstructure in Structural Steel. This results in improved strength, toughness, and weldability.
Copper is added to promote corrosion resistance in Structural Steel. It also improves the steel’s machinability, formability, and electrical conductivity.
Sulphur and phosphorus are two elements that are often limited in steel alloys. This is because they can negatively impact the steel’s durability and strength. Sulphur and phosphorus can cause brittleness and reduce the steel’s ability to be welded.
Molybdenum is added to increase the steel’s strength at high temperatures and its resistance to corrosion. Molybdenum is also used to enhance the steel’s hardenability and improve its toughness.
Characteristics Of Structural Steel
Structural steel possesses various properties that impact the design and construction of steel structures.
I have described important properties of structural steel which is used in the design of steel structure.
Density: The density of structural steel ranges from 7750 to 8100 kg/m3.
Young’s Modulus of Elasticity: Typical values for structural steel fall between 190-210 GPa.
Poisson’s ratio: The acceptable range for Poisson’s ratio in structural steel is 0.27 to 0.3.
Tensile strength: Structural steel boasts high tensile strength, making it a preferred material in construction.
Yield strength: Yield strength, also referred to as yield point, is the stress at which an object permanently deforms and does not return to its original shape when stress is removed. Carbon structural steel has a yield strength ranging from 187 to 758 MPa, while structural steel made of alloys ranges from 366 to 1793 MPa.
Shear strength: The shear strength of a steel structure is the failure stress under shear, and it is around 0.57 times the yield stress of structural steel.
Hardness: Hardness refers to the resistance of an object to shape change when force is applied. There are three different types of hardness tests: scratch, indentation, and rebound. Structural steel made of alloys has a hardness range of 149 to 627 kg, while carbon structural steels range from 86 to 388 kg.
Melting point: As there are various types of structural steel, there is no standard melting point.
Specific heat: Specific heat, or heat capacity, is the amount required to raise an object’s temperature by a specific quantity. A higher specific heat value indicates greater insulation. Carbon structural steel has a specific heat range of 450 to 2081 J/kg-K, while for structural alloy steel, it ranges from 452 to 1499 J/kg-K.
Types
Structural steel is commonly used in construction and manufacturing due to its strength and durability. Carbon is the most frequently used commercial steel alloy. Higher carbon content improves strength and hardness, but also makes the steel more brittle and less weldable.
There are various types of structural steel based on their carbon content and mechanical properties. Carbon steel contains up to 2% carbon and has an ultimate tensile strength of 410-440 MPa and a yield strength of 350-400 MPa. High-strength carbon steel has an ultimate tensile strength of 480-550 MPa and a yield strength of 350-400 MPa, and is used in structures like transmission lines and microwave towers.
Medium and high-strength micro-alloyed steel includes alloys like chromium, nickel, and molybdenum to increase strength while retaining ductility. This steel has an ultimate tensile strength of 440-590 MPa and a yield strength of 300-450 MPa.
High-strength quenched and tempered steel undergoes heat treatment to increase strength. It has an ultimate tensile strength of 440-590 MPa and a yield strength of 300-450 MPa.
Weathering steel is corrosion-resistant and typically not painted. It has an ultimate tensile strength of 480 MPa and a yield strength of 350 MPa. Fire-resistant steel, also known as thermo-mechanically treated (TMT) steel, is used in structures prone to fire.
Popular Steel Structure Sections
- Universal Beams (UB) – I-shaped cross-section
- Universal Columns (UC) – I-shaped cross-section
- Wide Flange (WF or W-Shape) – I-shaped cross-section
- H sections – I-shaped cross-section
- IPE – I-shaped cross-section
- HE – I-shaped cross-section
- HL – I-shaped cross-section
- HD – I-shaped cross-section
- Z-Shape – half a flange in opposite directions
- HSS-Shape – Hollow structural section (square, rectangular, circular, and elliptical cross-sections)
- Angle – L-shaped cross-section
- Structural channel, or C-beam, or C cross-section
- Tee – T-shaped cross-section
- Rail profile – asymmetrical I-beam
- Railway rail
- Vignoles rail
- Flanged T rail
- Grooved rail
- Bar – rectangular cross-section
- Rod – round or square section long compared to its width
- Rebar – round or square section used for reinforcement
- Dowel – cylindrical rod used for joining two pieces of material
- Plate – metal sheets thicker than 6 mm or 1⁄4 in.
- Open web steel joist – truss-like structure made of steel bars
Note: The specification of steel structure section also various based on region, countries and local authorities.
Closing Thought
Structural Steel is a widely used material in modern construction due to its high strength-to-weight ratio and constructability. It is favored for building high-rise structures as it requires less material to carry the same load as concrete.
Structural Steel is an essential building material that allows us to construct some of the world’s tallest structures.