Introduction to Structural steel.
The item included in this post will be the advantages, and disadvantages of structural steel.
Introduction to structural steel video.
The video discusses the advantages and disadvantages of steel as a construction material. The video has a subtitle and a closed caption in English. if you prefer to watch in Utube, this is the link.
The content of the post.
We are going to talk about a new subject, which is structural steel. We need to discuss several points. The first point is about the advantages and disadvantages of using steel as a construction material.
The second item is the relation between the stress and Strain of steel.
The next items will be discussed in the next posts.
The third item is about the different values of Yield stress for steel.
The fourth item is about the steel compositions what are the different steel grades?
The last item is about the different steel shapes and How we can estimate a given steel section? This is the content of the lecture as shown in the next slide image.
Structural steel and its advantages as a construction material.
We start with the advantages of steel. The first advantage is the high strength.
The steel has the advantage of carrying higher loads as compared with its lightweight. The unit weight of steel is higher than the unit weight of concrete.
I quote, for bridges and tall buildings and structures situated on poor foundations.
That was the advantage of steel. It has a higher own weight compared to any construction material.
The second advantage is uniformity. The second advantage is uniformity.
The properties of steel do not change appreciably with time, as do those of reinforced -concrete structures.
The third advantage of steel is elasticity. We can estimate the moment of inertia of steel structures with accuracy.
While the moment of inertia calculated for reinforced-concrete structures is somewhat indefinite. The next slide image shows the three types of advantages of steel.
The fourth advantage of a steel structure is its performance. I quote, that the steel frames that are correctly maintained will last indefinitely.
The age of steel structures can thus be extended by good maintenance.
I quote, research on some of the newer steels indicates that under certain conditions. No need for painting.
The next advantage is ductility, which is a property of Material.
That a given material can withstand extensive deformation without failure under high tensile stresses. Failure will occur after a large amount of elongation.
I quote when a mild or low-carbon steel member is being tested in tension.
A considerable reduction in cross-section and a large amount of elongation will occur at the point of failure, and a large number of elongations will be observed. This advantage gives a warning before failure, while brittle materials do not provide a warning before failure.
Disadvantages of structural steel as a construction material.
Now will be discussing the disadvantages of steel structures. The first disadvantage is corrosion.
Most steels are susceptible to corrosion when freely exposed to air and water and, therefore, should be painted periodically.
Weathering steels are a family of low-carbon steels with additional alloying elements mixed in with carbon and iron atoms.
These alloying elements give weathering steel better strength and more corrosion resistance than typical low-carbon steel grades, however, suitable applications tend to reduce the cost of maintenance.
The next disadvantage is the fireproofing cost.
The strength of steel is affected by the fire.
I quote, that many disastrous fires have occurred in empty buildings where the only fuel for the fires was the building themselves. Steel is an excellent heat conductor.
Additional disadvantages of steel.
Non-fireproofed steel members may transmit enough heat from a burning section.
The next disadvantage of steel is that steel is susceptible to buckling.
For buckling, we consider two factors which are the length and the second is the radius of gyration.
The slenderness of the member can be estimated. When the buckling length increases and the cross-section is getting smaller, the slenderness ratio is increased.
Additional steel is needed to stiffen the steel columns so that they will not buckle; this is done by adding bracing to the columns. The next disadvantage is the Fatigue of steel.
Fatigue is undesirable for steel since it affects strength. Fatigue is a large number of stress reversals.
I quote, that fatigue problems occur when tension is involved. Fatigue can be due to a large number of variations of tensile stress. The brittle fracture is also a disadvantage of steel.
This brittle fracture occurs at places of stress concentration.
This is the Pdf used in this post.
The next post will discuss the relationship between stress and strain for steel.
This is a link to a very good reference, A Beginner’s Guide to Structural Engineering