Structural Steel

What is Structural Steel?

Structural Steel is a special kind of Steel. It is used for construction purposes. Due to its rigidity and high strength-to-weight ratio, structural Steel is mainly employed in buildings. Structural Steel is used in houses, warehouses, airplane hangars, educational facilities, bridges, stadiums, etc.

Structural Steel Definition

Structural Steel is Steel that contains carbon, not more than 2.1%. These are also called Carbon Steel, and structural Steel typically has a carbon content of less than 0.6%.

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Properties of Structural Steel

The features of structural steel influence the design and construction of steel structures, and the value of different steel characteristics are highlighted below. The various tests that produce the importance of mechanical properties of structural Steel and the desired values of each parcel have been discussed in this article.

• Density: The density of Structural Steel is 7750 to 8100 kg/m³.
• Young's Modulus of Elasticity: Typical values for structural steel range from 190-210 GPa
• Poisson's ratio: For structural Steel, the acceptable value ranges from 0.27 to 0.3.
• Tensile strength: Structural Steel has high tensile strength, so it is preferred over other construction materials.
• Yield strength: The yield strength, also known as the yield point, is the stress at which an object permanently deforms. When stress is removed, it does not revert to its former shape. Carbon structural steel has a yield strength ranging from 187 to 758 MPa. The values of structural Steel constructed of alloys range from 366 to 1793 MPa.
• Shear strength: The shear strength of steel structure is specified at the failure under shear stress, and it is about 0.57 times the yield stress of structural Steel.
• Hardness: The resistance of an object to shape change when force is applied is referred to as hardness. There are three different types of hardness tests. Scratch, indentation, and rebound are all terms used to describe the process of scratching and indenting, and the hardness of structural Steel manufactured with alloys ranges from 149 to 627 kg. Carbon structural steels have a weight range of 86 to 388 kg.
• Melting point: Because there are so many different types of structural Steel, there is no standard melting point.
• Specific heat: The amount required to raise an object's temperature by a particular quantity is known as specific heat or heat capacity. A higher specific heat value indicates that the thing is more insulating. The units of measurement are Joules per Kilogram Kelvin. Specific heat for carbon structural steel ranges from 450 to 2081 J/kg-K, while for structural alloy steel, it ranges from 452 to 1499 J/kg-K.

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Types of Structural Steel

Carbon is the most often used commercial steel alloy. Increased carbon content improves hardenability and boosts hardness and strength. Conversely, carbon increases brittleness and lowers weldability because of its propensity for forming martensite. As a result, the carbon content in commercial Steel can be both a blessing and a burden. Based on the carbon content, the mechanical properties of different types of structural Steel and their uses are given below:

• Carbon steel: Steel in which the carbon content is upto 2% is known as carbon steel. The Specified ultimate tensile strength is 410 to 440 MPa, and the yield strength is 350 to 400 MPa.
• High-strength carbon steel: These steels are used in structures such as transmission lines and microwave towers. The specified ultimate tensile strength is 480 to 550 MPa, and the yield strength is 350 to 400 MPa.
• Medium and high strength micro-alloyed steel: Alloys such as chromium, nickel, molybdenum, etc., are used to increase the strength while retaining the desired ductility. The specified ultimate tensile strength is 440 to 590 MPa, and the yield strength is 300 to 450 MPa.
• High strength quenched and tempered Steel: Heat treatment increases strength in this type of Steel. The specified ultimate tensile strength is 440 to 590 MPa; the yield strength is 300 to 450 MPa.
• Weathering Steel: These are corrosion-resistant Steel and are often not Painted. The specified ultimate tensile strength is 480 MPa, and the yield strength is 350 MPa.
• Fire-resistant Steel: These steels are also known as thermo mechanically treated (TMT) steel and are used where the structures are more prone to fire.

Types of Steel Sections

Structural steel members are fabricated in factories according to their intended use. Continuous casting molds are used to cast rolled steel parts with no joints. The following sections describe the various shapes and forms of rolled steel sections.

1. Rolled Steel I-sections (Beam sections).
2. Rolled Steel Channel Sections.
3. Rolled Steel Tee Sections.
4. Rolled Steel Angles Sections.
5. Rolled Steel Bars.
6. Rolled Steel Tubes.
7. Rolled Steel Flats.
8. Rolled Steel Sheets

Rolled Steel I- sections

Used as beams or columns.

Beams

• ISJB – Indian Standard Junior Beam
• ISLB – Indian Standard Light Beam
• ISMB – Indian Standard Medium Beam
• ISWB – Indian Standard Wide Flange Beam

Columns/Heavy weight beams

• ISSC – Indian Standard Column Section
• ISHB – Indian Standard Heavy Beam

Rolled Steel Channel Sections

Used in steel-framed structures, steel bridges, crane girders

Categories

• ISJC - Indian Standard junior channels
• ISLC - Indian Standard lightweight channels
• ISMC - Indian Standard Medium Weight Channel.
• ISMCP - Indian Standard Medium weight parallel flange channels

Rolled Steel T - Sections

Used to form built-up sections and as members of steel roof trusses.

Categories

• ISNT - Indian Standard Normal Tee Bars
• ISHT - Indian Standard Wide flange Tee Bars
• ISST - Indian Standard Long Legged Tee Bars
• ISLT - Indian Standard Light Tee Bars
• ISJT - Indian Standard Junior Tee Bars

Rolled Steel Angle Sections

Used in the construction of roof trusses and filler joist flooring.

Categories

• ISA - Indian Standard Equal Angles
• ISA - Indian Standard Unequal Angles
• ISBA - Indian Standard Bulb Angles

Rolled Steel Bars

Used as reinforcement in concrete and steel grill work, among other things.

ISRO – Indian Standard Round Bars

Rolled Steel Tubes

Used in tubular trusses as columns, compression members, and tension members.

Rolled Steel Flats

Lattice bars made of rolled steel flats are used to connect the elements of built-up columns.

Rolled Steel Sheets

These are used in automobiles, appliances, furniture, and other everyday items.

Uses of Structural Steel

Structural Steel is the most widely used engineering and building material on the planet and is commonly used in modern construction. Because of its constructability and high strength-to-weight ratio, Structural Steel is used to build today's highest structures.

Concrete, on the other hand, has a substantially lower strength-to-weight ratio than Steel, although being less dense. This is owing to the considerably larger volume necessary for a structural concrete element to hold the same weight; Steel, although denser, requires less material to carry the same load.

Building Works

• Used as a structural component in trusses, beams, and other steel structures.
• Grills, doors, windows, and other non-structural materials
• In steel pipelines, tanks, and other similar structures.
• Used in sanitary and sewer fittings, rainwater items, and so on.
• The sheets are made of corrugated cardboard.
• Used as concrete reinforcement.

Reinforcement Works

Since the concrete is strong in tension and weak in compression, Steel is used as reinforcement to increase the tensile strength of the concrete structure.

Composition of Structural Steel

The chemical compositions influence the properties of Structural Steel. Some chemical elements used to enhance the mechanical properties are listed below. Structural Steel is a mixture of iron and other metals. Some parts are purposefully added to iron to achieve specific properties and features; the various compositions have been discussed in the following:

• Carbon: One of the most significant chemical ingredients in Steel is carbon. Carbon concentration rises, resulting in a material with less flexibility and more strength.
• Chromium: Small levels of chromium are present, combined with copper and nickel, to strengthen the material's corrosion resistance.
• Manganese: Manganese, along with oxygen and sulphur, is employed as a neutralizer in the hot rolling of Steel, and it has effects on the material properties of steel grades that are similar to those of carbon.
• Aluminum: Aluminum is a key deoxidizer that contributes to forming a finer-grained crystalline microstructure.
• Copper: Copper is used to promoting corrosion resistance.
• Sulphur and phosphorus: Sulphur and phosphorus are often limited in steel alloys because they negatively impact the Steel's durability and strength.
• Molybdenum: Molybdenum increases the Steel's strength at high temperatures and its corrosion resistance.

Best Books for Design of Steel Structures

Here is the list of best books to prepare the Steel Structures required for candidates preparing for GATE CE 2023.

• Design of Steel Structures by S.K.Duggal
• Design of Steel Structures by N. Subramanian
• Design Of Steel Structures by L Negi