# Which is stronger, solid beam or I-beam?

1. …if they have the same external dimensions?

2. …if they have the same mass?

I’m just wondering this but my physics background isn’t particularly strong. Thanks!

Update:

Could you give me a short description of WHY, especially #1? How does removing mass make it stronger?

Could you give me a short description of WHY, especially #1? How does removing mass make it stronger?

• Andrew S
1 month ago

1) The solid beam (I beams are only stronger when they have greater dimensions)

2) The I beam

In both cases the strength is governed by the stress within the beam and how much material is involved. The solid beam is easy to understand – more material is present all of which must be stressed to produce a given deformation of the beam.

In the second case since the beams are of equal mass the same amount of material is present but the I beam distributes it differently. With the beam in a vertical orientation a given deformation is the result of greater strain within the beam – on account of the greater depth the upper surface of the beam must be stretched by a greater amount to produce the same deformation. That greater strain needs a greater force to produce it, in other words a greater load.

• oil field trash
1 month ago

Based on them having the same external dimensions, the solid one will be stronger.

Based on the same mass, the I beam will.

In the first case the solld beam will have the greater section modulus and the the second case the I beam will have the greater section modulus.

It isn’t so much as matter of removing mass but rather placing it as far from the horizontal center line as possible.

You can do the math if you look at the link below.

• ?
1 month ago

1. The solid one is stronger because it has more material.

2. Depends what you mean by “strong”. They both have the same compressive or tensile strength, because they have the same amount of material. But the I-beam is stifffer against bending because the matreial is more widely distributed, like a soda straw is stiffer than a stir-stick.

• Yarok
1 month ago

a solid beam is stronger.

I-beams are used because they have a better strength/mass ratio, in architecture mass is critical as the more mass you use the more support you need.

1. solid beam beats I-beam – the solid beam would be stronger but impractical.

2. I-beam beats solid beam – but would probably be rather large.

• Irv S
1 month ago

1. Same dimensions – Solid (there’s more material)

2. Same mass – I beam( It makes more efficient use of the material it contains.)

• Sharon
1 month ago

i-beam is stronger.it’s 2 flange and thicker cross web can hold more load.that y gantry’s r made frm ibeam only.

• amrselimy
1 month ago

l-beam !!