What is the best way to reduce the weight of a steel beam without compromising its strength?

[danielgomez]

Hi everyone,
I’m working on a project where we need to reduce the weight of a steel beam, but we can’t sacrifice its strength. What are some effective methods or design considerations to achieve this balance? Any suggestions or tips would be really helpful!

 

[W460x68]

Speaking purely to the weight of material, going with a deeper section is the best way to economize a steel beam. You'll get more strength for less weight.

 

[DrZoidberWoop]

but we can’t sacrifice its strength

What kind of strength? Global flexure? Shear? Ability to handle concentrated loads/bearing? Serviceability concerns?

Obviously castellating a beam saves weight, but has limits.

 

[KootK]

I was also going to recommend castellating. It does reduce shear capacity but that's rarely what governs the design of a steel beam.

But, yeah, knowing what kind of strength is massively important here.

As an example, if your governing failure mode is lateral torsional buckling in flexure, you may be able to save gobs of weight by adding in small elements to the system that laterally brace your beam compression flange.

 

[Eng16080]

Definitely agree with the comments above concerning what strength. Reducing the weight of the beam will most certainly compromise something, it's just a matter of whether that something controls.

Assuming the beam strength in strong axis bending/deflection controls and assuming it's fully laterally braced, then making the beam deeper is usually the solution. Castellating the beam is something that was more common (I want to say in the 60s/70s) but is less common now due to the labor involved. Most clients will not directly care about beam weight, but rather cost, so if the deeper/lighter beam is not cheaper, it probably fails to meet the overall goal.

 

[SWComposites]

yes,
a) why do you need to reduce the weight?
b) what strength checks are currently sizing the beam?

 

[ThomasH]

Hi everyone,
I’m working on a project where we need to reduce the weight of a steel beam, but we can’t sacrifice its strength. What are some effective methods or design considerations to achieve this balance? Any suggestions or tips would be really helpful!

I agree with a lot of what has already been said. But I can't help wondering, what is the purpose of the question?

The reason I ask is because you are registred as a Student, and I think the question could be very good from a teaching perspective. Instead of making a lot of repetitive beam calculations, ask a question like this and listen to the reply. Your reasoning would be the interesting part.

 

[EngDM]

There are a lot of ways to reduce weight without compromising strength, but as others are saying it really comes down to what solutions you are able to incorporate with your current conditions and structure restrictions.

Here are a couple of examples:

1. If you are restricted to a certain depth, for instance to ensure a specific clear height below the beam, then you can't go the route of increasing depth and reducing weight. A common option here would be to try and resist the top chord from buckling, and reduce your effecive length. If you cannot effectively brace the top flange, than the solution will become more complicated.

2. If you have multi-span conditions, adding a few double or single cantilevered beams with drop-in beams will lower your positive bending, and allow you to reduce your shape. But by doing this you have to be careful on how you are handling the negative bending.

3. If saving as much weight as possible is the focus, relaxing the deflection requirements can help you get there (you can do this for certain types of buildings, usually warehouses or low occupancy structures where deflection is of little concern).

In short, it really depends on the situation; there is no clear cut catch-all answer since there are several different failure modes of beams. With experience you'll get comfortable on a sort of "order" that you could start considering the solutions, and start with the easiest to implement and work your way down.

 

[HTURKAK]

Short respond ; If stability / LTB is not a problem, use higher strength steel grades . ( Eg; Instead of S235 Use HISTAR steel having yield
strengths of 355 MPa and 460 MPa)
For long respond , some details are necessary.