Fill a steel beam with concrete or not?

[Arne999]

I'm going to put steel supports under an old foundation wall and am considering 80x80x6 just because 80 is what my small metal band saw can cut.

Is there any point in filling this with concrete to make it stronger? The profile might be sufficient as it is, but one tends to overdo, and the question is really general.

Fill steel profile with concrete or not? What type of concrete if so?

Moreover, it's MUCH cheaper to buy 80x80x3 or 80x80x4 instead of 80x80x6... so if something can be said about the difference with or without concrete, that would be good.

 

[atomlab]

Concrete is much better in terms of compressive strength, so the steel tube will only be to hold the concrete in place.

Will you be able to fill the tubes from above? If so, regular concrete will work. If you can only pour from the side, you will need expanding concrete.

 

[Arne999]

I am in the process of constructing so I would pour concrete in that case before it is in place. But what you are saying is that 6mm thick material on the profile is a bit unnecessary and I can save a few mm. I want to be able to weld easily so I prefer not to reduce too much.

 

[justusandersson]

What is the height of the pole?

 

[Arne999]

2 meters or perhaps rather 1.8-1.9

 

[witten]

Concrete is much better in compressive strength so the steel pipe will only be to hold the concrete in place.

Will you be able to fill the pipes from above? In that case, regular concrete works. If you can only pour from the side, you need to use expanding concrete.

That is not true at all. The steel column is stronger than the concrete even though the concrete increases the overall load capacity.

 

[Peter2400]

Have you calculated the load the pillars should withstand?
If you look at this table, it seems like they can handle quite a lot.

 

[witten]

2 meters or perhaps rather 1.8-1.9

A 2-meter column 80x80x4 can handle a design load of 25 tons. 20 tons for the same column with 3 mm material. Don't forget the rust protection.

 

[witten]

Have you calculated what load the columns should handle?
If you look in this table, it seems like they can handle quite a bit.
[image]

Likely it is KKR he is looking at, the table refers to VKR which have higher load capacity.

 

[Arne999]

So, I just want to reinforce an old construction that looks a bit shabby. It could very well hold as it is, and I will install 4 pillars. A few hundred tons in load over these do not exist even if they have to bear everything However, I like to overdimension like crazy. Concrete costs nothing, so if it makes things better, I'm happy to pour it in.

 

[witten]

It does provide corrosion protection from the inside if that feels better, but for load-bearing capacity, it is not needed in that case. In terms of natural resources, there is also no reason to use more than necessary.

 

[Arne999]

In terms of natural resources, I completely agree. I probably don't need to defend my footprint, but it becomes a philosophical question, so I'll stop there

 

[justusandersson]

The load-bearing capacity of poles is determined by the risk of buckling. It is therefore the bending strength that is tested. The load-bearing capacity decreases with the square of the height. A post twice as high has only a quarter of the load-bearing capacity. This applies regardless of the material. The theory for this was formulated by the Swiss mathematician Leonard Euler in the 18th century.