why do the iron beams of a house are in the shape of letter "I " . does it add any strength .?

Answer 1

it makes them stronger

Answer 2

Good observation!!. :)
To keep things simple, lets look at the letter 'I'. The beam is basically used to support the building structure which is subjective to constant uniform loading.

The beam will have to bear the "load which translates into the bending and shearing stresses". In other simpler words, depending on the loadtype, amount and the position of the load, the beam 'experiences' 'bending' and 'cutting' forces across it's length and hence are susceptible to breakages/ failures.

To nullify these forces the beam should have a "safe cross-section" area which will sustain the load. But having such an beam would consume huge amount of steel and hence the beam itself would be too heavy and costlier.

So, the interest is to have a 'section' (shape) which gives maximum safety with 'minimum' material being consumed into the steel beam. The letter "I" provides an almost perfect section to counter these kind of loads with "assured" safety. This is because the "moment of inertia" and "center of gravity" for an "I - beam" provide far more safety than any other solid shape with minimum material.
One more point to your observation, more the load, thicker will be the flange of the beam :))

Answer 3

The strength, or the amount of deflection in the beam from the weight of the floor above is determined almost entirely by the height of the center web, and to a lesser degree, the thickness of the web.
An I Beam with a web 6 inches high, will have much more deflection than an I Beam with a 12 inch high web. In fact, a 12 inch deep I beam is 13 times as strong as a 6 inch I beam, all other factors being equal.

The two parallel plates, one above, and one below the web, are called flanges. In the case of an I beam used to support a floor, the primary function of the flanges is to keep the web perfectly vertical (for maximum strength), and to prevent side to side twisting, which is most likely to occur before or during the installation of he beam.

In home construction, the flanges also provide a nice flat platform, off of which joists and other structural members can be easily attached and supported.

The dimensional relationship between the height and thickness of the web, and the width of the flanges varies widely.
There are many shapes and designs for I Beams and H beams.
Engineers select the proper shapes depending on the amount of force that is expected in each direction for a particular application.
For example, H beams (web and flanges all identical) are commonly used as columns in buildings and tall structures. The H shape column has pretty much equal resistance to bending from wind coming from any direction, and it also is the shape that provides the maximum amount of strength to prevent the column from buckling from the compressive (vertical downward)force of the weight of the building.

Answer 4

A capital I or a capital L.
Since there are two perpendicular forces that can act on a beam, sideways and up and down, the I or the L shape takes the stress from either direction better without bending or shearing. Also the I beam shape can attach easily to other beams with bolts of welding.

Answer 5

Steel beams(iron beams) are made in the I shape so as to stand up to a certain amount of pressure applied on any part of the surface and so that it wont crumble due to the load applied,just imagine a straight piece of metal strip instead of I beam and try loading a few tons of weight on it and it will just bend and collapse

Note:I Beams are small there are other versions called H Beams which are mainly used in heavy construction industries such as Oil & Gas industries

Answer 6

They are a compromise between strength, and weight.

A solid beam would be stronger, but the weight would be tremendous and prohibative for building.

An I beam has almost the strength of a solid beam but at less than half the weight.

Answer 7

jguffre got it right, but let me try to make it clearer. Imagine an iron wire. It's easy to bend. Make it thicker, and it's harder to bend but it's heavier. Now flatten it. Now it's easier to bend in the narrow direction and harder to bend in the wide direction. Now make it just barely big enough to support the load when installed edgewise. Your design is satisfactory, as long as it stays edgewise. The easiest way to keep it from deforming with minimal added weight is to make part of it thicker in the narrow direction. You could do that by making it in the shape of an X. But the I shape gives you other benefits, like a better surface for holding up the floor and attaching the floor.

Answer 8

I beams in a house are used to support weight. The force acts mainly in one direction.

The strenght of I beam is almost equal to the strength of solid rectangular beam except its own weight is less. This is true when we consider the forces in one direction.

Answer 9

In addition to the above informations:-
To spread the weight of the roof uniformly

Answer 10

The flat sides give optimal support.
The midsection gives maximal strength.
And because you don't have a massive block you have a significant weight reduction.

Answer 11

yes