- Structural steel is one of the materials used for any kind of construction steel, it is created with a specific shape. These steel materials have certain standards in terms of chemical composition and suitable strength. Steel material is also defined as hot-rolled product, with cross-sections such as corners, grooves and beams. The demand for steel structures is increasing around the world
Steel structure can be classified as follows:
- Frame construction
- Plate beams
- Steel arch bridge
- Industrial buildings
- Tower transmission line
Advantages and disadvantages of steel structures:
- In general, the advantages of steel structures are as follows: High strength steel over a high weight ratio. Hence the dead weight of steel structures is relatively small. This property makes steel a very attractive structural material for a number of multi-storey buildings, long span bridges, etc.
- It may undergo plastic deformation before failure; this provides greater reserve strength. This property is called ductility.
- Steel properties can be predicted with very high certainty. In fact, steel exhibits elasticity up to a relatively high level of stress and is often well defined.
- Steel structures can be constructed with high quality and narrow tolerances.
- Steel structures can often be prefabricated and mass produced.
- Can be applied quickly in steel structures. This saves construction costs of steel structures.
- Good fatigue strength is also an advantage of steel structures.
- If necessary, steel structure can be reinforced at any time in the future.
- The reusability of construction steel is also an advantage.
In general, the disadvantages of steel structures are as follows:
- Steel structures cost more than other types of structures.
- The strength of steel is significantly reduced when heated at common temperatures in a fire; therefore, fireproof treatment is required.
- Steel structures when exposed to air and water, such as in the case of bridges, are susceptible to corrosion and require regular maintenance.
Steel is an alloy of iron and carbon. Special properties can be transferred to iron by adding a small percentage of manganese, sulfur, copper, phosphorus, chromium and nickel, thus making a variety of steels possible. In general, the effects of the various chemical components on steel are as follows:
- Increasing the carbon and manganese content results in properties such as higher tensile strength and yield strength but lower ductility and is more difficult to weld.
- If the sulfur and phosphorus content increases by more than a percentage then it causes brittleness and thus it affects weldability as well as fatigue strength.
- The chromium and nickel content will provide corrosion resistance in steel, and its resistance to high temperatures can also be improved.
- Corrosion resistance can be improved by adding copper.
Small changes in the chemical composition will result in different types of steel. This steel is used as structural parts such as pipes, plates, pipes, bolts, studs, reinforcing bars, etc.
Heat treatment and alloys used in steel production result in different properties and durability. The mechanical properties of steel structures are as follows:
- Tensile strength:
The stress-strain curve for steel is usually obtained by performing a tensile test on any standard steel sample. The tensile strength of steel can be determined in terms of yield strength and ultimate strength.
Hardness is considered to be the ability of any material to resist identification and scratches. This is usually determined by pressing a dent in the surface. The result is a deformed steel that is both elastic and flexible. Different methods of finding a metal hardness include the Brinell hardness test, the Vicker hardness test and the Rockwell hardness test.
- Notch toughness:
It is possible that microscopic cracks appear in the material or the material may develop such cracks as a result of several loading cycles. These cracks can cause structures to collapse suddenly and are very dangerous. Therefore, to ensure this does not happen, materials with slow-growing cracks are preferred. These steels are called notched hard steels and the amount of energy it absorbs is measured by impacting the notched sample.
- Strength of materials:
A structure component, designed to withstand unilateral static loads, may fail if the same load is cycled in a large number of times. If the example of a thin bar is considered, it is bent back and forth with no resistance and will fail after several such repeated cycles. This type of failure is called fatigue failure. Examples: bridges, cranes, offshore structures, slender towers, etc.
Corrosion is the oxidation of metals under normal atmospheric conditions due to too much moisture and oxygen in the air. Metal corrosion is a very natural and rapid phenomenon in places with high humidity and near salt water. Consequently, attempts have been made to control corrosion using galvanized and epoxy coated rebar bars but were unsuccessful in practical use due to the risk of disintegration, which causes rapid corrosion. Corrosion-resistant elements such as copper, phosphorus and chromium are added to the metal in the appropriate manner, resulting in steel being resistant to corrosion.
- Roll steel
Like concrete, profile steel of any shape and size cannot be cast in place, since steel needs very high temperature to melt and roll into the required shape, profile steel of any shape, size and dimension. Standard length is rolled in steel mills and sold in the market.
Rolled steel sections include beams, columns, channels, rectangular hollow sections, circular hollow sections, single corners, tees, double angles and constructed sections.