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Beam. Is it just a 3-dimensional line?
Table of Contents:
We all have at least once driven over a bridge or a flyover. Or been the other one. Took the wrong exit and stuck in traffic instead of a convenient flyover.
But while looking at a flyover have you ever wondered how is that structure standing? How does that big block of concrete is so up in the air and carrying the load of heavy vehicles passing over it?
Definition:
A beam is a structural element that supports/resists any lateral load applied through its axis.
A beam is a very important mechanical structure and can be found in a lot of heavy load-bearing structures. For any structure, a beam is a primary or foundation element.
How is the beam able to carry such heavy loads?
A beam is a 3-dimensional structure and its load bearing strength is dependent on its cross-sectional geometry. A simple beam may not be able to resist load as much as an I-section beam does.
Different types of beams:
Rectangular – The cross-section of the beam is a rectangle.
T-section – The cross-section of the beam is a profile similar to the alphabet T.
I-section- The cross-section of the beam is similar to the alphabet I.
Angular- The beam has wing-like profiles at a certain angle to the longitude.
Now we have seen how the beam structure is. But how is it standing up high in the sky?
For any structure, the important factor is the foundation or the platform on which the structure is built. Just like that for beams, it’s important how the beam is supported. The beam can be supported by a variety of means. Like,
Simply supported beam – A beam with single point fixed supports on both ends. One end of the beam can be free to move in the lateral direction. A common example of this is a draw bridge.
Overhanging beam – One end of the beam will be extended beyond the support. The support can be a single point or roller.
Cantilever beam – Only one end of the beam is supported and the other end is hanging free. A common example of this can be the diving board on a swimming pool.
Double overhanging beam – Both ends of the beam are extended outwards beyond the supporting points. A common example of this in our daily life in form of a dining table.
Continuous – A beam supported with more than two support points. The beams are usually longer or need to bear a heavy load.
It’s all cool how the structure is built and how it is supported. Now let’s take a look at how the beam transmits/handles load.
As you can see in the above illustrations, there are various types of loading conditions that can happen on a beam. How is it useful in real life though? In reality, the structures will have a load in a similar fashion or a combination of either of these conditions.
So, the different loading conditions are
Point Load - The beam experiences load at a singular location between the two support points. This is a static load condition and a common example of this will be a ceiling fan hanging on the beam. The load is concentrated on one single point.
Uniformly distributed load - The load is distributed evenly through the length of the beam. The load at any point on the beam will be constant. A flatbed truck with evenly loaded sand is an example of a uniformly distributed load. The load at any point on the base of the bed will be equal.
Triangular Distributed Load - This is a dynamic loading condition. The load is distributed in an incremental fashion from one end of the beam to the other starting with zero.
Trapezoidal distributed load - The load is distributed in an incremental fashion from one end of the beam to another.
Point Moment - This loading condition is different from the earlier mentioned one. The beam experiences a twist or moment at a certain point between the supports.
L - length of beam (m)
P - Load applied (N)
a - distance of point-of-load to support (m)
w - Load distribution (N/m)
M - Turning moment (N-m)
Summary:
Beams are the primary elements of a structure.
The load-carrying ability of a beam depends on the support of the beam.
The shape of the beam is an important factor for the load-carrying ability of the structure.
There are more complex structures which are developed with beams being the primary element. Such structures are known as truss.
Scratch your brain.
What is the most common type of beam you see in your day-to-day life?
Have you ever noticed the railway track? Does it fall under the category of beams? If yes, what type of beam it is?
Everyone likes a cold swim on a hot day of summer. Taking big dives from those diving boards. Did you notice what type of support those diving boards have? What is it called?
Beams are the primary elements of any construction project. There are bigger structures formed with beams. What are those cage-like structures called?