Structural steel is one of the materials which used for any kind steel construction, it is formed with a specific shape. These steel materials are of certain standards of chemical composition and proper strength. The steel materials are also defined as hot rolled products, having cross sections like angles, channels and beam. All across the world, there is an increasing demand for steel structures.
There is a big advantage of steel over the concrete in terms of its ability to bear better tension as well as the compression which resulted in lighter construction. The steel authority of particular country takes care of the availability of structural steel for construction projects.
There are various structures which come under the edges of steel structures. These structures may be used for the industrial, residential, office and commercial purposes. The purpose of bridge is for roadways and railway lines. The structures like towers are used for different purposes such as power transmission, nodal towers for mobile network, radar, telephone relay towers, etc.
Steel structures can be classified as follows:
In general, the advantages of steel structures are as follows:
While in general, the disadvantages of steel structures are as follows:
Steel is an alloy of iron and carbon. The special properties can be imparted to iron by adding a small percentage of manganese, sulfur, copper, phosphorous, chrome and nickel, therefore variety of steel can be produced. Generally, the effects of different chemical constituents on steel are as follows:
Increase contents of carbon and manganese will induce the properties such as higher tensile strength and yield strength but have lower ductility and it is more difficult to weld.
The slight changes in the chemical composition will result in the various types of steel. This type of steel is used as structural members like tubes, sheets, pipes, bolts, rivets, reinforcement bars, etc.
The heat treatment and alloys used in the production of steel results in different properties and strength. The mechanical properties of structural steel are as follows:
The stress-strain curve for the steel is generally obtained by conducting tensile test on any standard steel specimen. Tensile strength of the steel can be defined in terms of yield strength and ultimate strength.
Hardness is regarded as the resistance of any material to identification and scratching. This is generally determined by forcing an indenter on to the surface. The resultant deformation steel is both elastic and plastic. The different methods to find out the hardness of metal which includes Brinell hardness test, Vicker’s hardness test, and Rockwell hardness test.
There is the possibility of microscopic cracks in a material or the material may develop such cracks as a result of several cycles of loading. These cracks may result in sudden collapse of the structure and it is very dangerous. Therefore to ensure that this should not happen, materials in which the cracks grow slowly are preferred. These types of steel are known as notch-tough steels and the amount of energy it absorb is measure by impacting the notch specimen.
A component of structure, which is designed to carry a single monotonically static load, may fail if the same load is applied cyclically a large number of times. If the example of a thin rod is considered, it bent back and forth beyond yielding fails after few cycles of such repeated bending. This type of failure is termed as fatigue failure. Examples: bridges, cranes, offshore structure, slender tower, etc.
Corrosion is the procedure in which oxidation of a metal in a normal atmospheric condition owing to the excessive presence of moisture and oxygen in the air. Corrosion of the metal is a very natural and rapid phenomenon in the areas of high humidity and places closer to saline water. Therefore the efforts to be made to control the corrosion by using galvanize and epoxy coated reinforcement bars but failed in practical usage due to the risk of disbanding, causing accelerated corrosion. Corrosion resistance elements such as copper, phosphorus and chromium are added in appropriate measure to the metal which results in corrosion resistance steel.
Like concrete, steel sections of any shape and size cannot be cast on site, since steel needs very high temperature to melt it and roll into the required shape, steel section of standard shapes, sizes and lengths are rolled in steel mills and marketed.
The rolled steel sections consist of rolled beams, columns, channels, rectangular hollow sections, circular hollow section, single angle, tees, double angles and built up sections.