Best triangular shape for a support underneath a steel shelf

[Garry1234]

Good day,

I am wondering if someone will be able to please assist me? I am currently trying to redesign a support that is spot welded underneath a steel shelf. (Please see images attached). The current design uses a large quantity of material and I do not believe that it is very strong. I have also attached a proposed design - that I feel is extremely strong and is a better design.

My question is - Is the triangular support the best to implement? what is the best angle to use for the triangular support and the best height of the triangle so that I can use the least amount of material whilst keeping the shelf extremely strong?

Does the height of the triangle matter with regards to strength in a bending force?

Thank you very much

 

[Garry1234]

Please see the current shelf attached to make reference

 

[SlideRuleEra]

...triangular support the best to implement?
...what is the best angle to use...
...the best height of the triangle...
...use the least amount of material...
...keeping the shelf extremely strong?

It is highly unlikely that a single design will be "best" for all requirements. You will have to put the requirements in order, from most important to least important. The design may be "best" for the top priority, and a compromise for the other priorities.

Believe you can eliminate one requirement... if the support is not triangular, what shape do you propose as an alternate?

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[Garry1234]

Hi, thank you for the response.

I would like to implement a triangularly shaped support - however, I want to optimize strength whilst minimizing the amount of material used.

 

[SlideRuleEra]

Garry1234 - You will have to decide which is top priority:

1. High strength?

2. Minimum material?

Chances are the optimized answer will be neither the highest strength nor the least material... but an acceptable compromise of both requirements.

This project is a good example of what a Development Engineer (as in Research and Development) does. There is no "right" answer, it is up to you to use engineering skills to make choices and determine the best compromise solution. You may have to make and check some preliminary designs (that, in the end, don't work) but allow you to get a "feel" for what may work.

My first job out of university was a Development Engineer for aircraft equipment. Found the work so interesting that after 4 years full time, continued another 18 years part time.

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[rb1957]

is this a school project ? words like "least, minimum" and "maximum" are not often used in the real world except is specialised applications which I don't think your shelf is.

The 2nd pic looks like the support of a table, assuming you are looking down; yes?

How does the 1st pic apply to the second ?

Before you "optimise" the design you need some data ...

1) what load are you designing for ? Are the labour code requirements ??

2) What feature of the current "shelf" are you trying to improve ? Reduce (not minimise) material ? Do you know the current value ?
3) One triangle shape is unlikely to be "optimal". Much better would be several triangles, like corrugations. I suspect that maximum load is carried by corrugations of side length something like 12mm (based on 0.6mm thickness)

another day in paradise, or is paradise one day closer ?

 

[Garry1234]

Good day,

Thank you for your responses.

@SlideRuleEra - thank you for the information

@rb1957 - no this is a project I am trying to tackle at work, as I feel there can be some major improvements with regard to the current design. In the image of the shelf (yes, looking from the side downward - there are structural supports that are welded to a shelf shell. - the drawing is a proposed improvement of that support).

1. The load we are looking at is around 100kg
2. I would like to reduce material while keeping the integrity of the structure - currently, we roll o coil that is 120mm wide.

My objective is to help save our company money over the long run - if we can reduce the width of the material by just 10mm whilst maintaining the strength, the long run return will be massive as we produce approx. 1000 of these supports a day.

Thank you very much.

 

[dhengr]

Garry1234:
The triangular stiffener shape that you have sketched is actually significantly inferior from the structural and strength standpoint. The existing stiffener, as shown in your photo is actually a very efficient shape structurally, because it has some material area/volume at the flange furthest away from the shelf surface itself. And, you already have the rollers for forming that shape. Your “V” shape has almost no steel material at this bottom flange area. Your “V” shape will be stressed more highly in the bot. flg. area and will be more likely to yield and will deflect more under the design load. You have given no info. on actual sizes, thicknesses, dimensions of the shelf, thickness of the parts, real engineering details and drawings, etc. so it’s tough to comment beyond the above. The upshot is that there is no best or better “V” shape when compared with the current design of those stiffeners.

You are talking about trying to save 10mm of a real thin steel strip, out of a total width of 120mm before roll forming to shape. That’s an 8.3% (10/120) reduction in material costs on about 1000 of these stiffeners per day. That’s (10mm by .5mm thk. +/-)(900mm long) material volume per stiffener. You figure it out, I don’t know your material costs. The other costs of fabricating those shelves to a finished piece fare outweigh this small potential material savings. I would look to improve your various manufacturing steps if you really wanted to wring costs out of these shelves.

This sounds a lot like someone trying to justify their existence by saving a few pennies per shelf, not knowing what they are really doing structurally, and in the process producing an inferior final product. The negative impact on the finished product, quality, strength, durability, return costs, etc. will do more damage to your name than the few pennies saved. This seems penny wise and pound foolish to me.

 

[BridgeSmith]

Are you looking for greater strength for shelf capacity? If so, you won't do much better than the current configuration, certainly not with a triangular shape. The current configuration places a significant portion of the area of the support rib at close to the maximum distance from the shelf shell. That gives it a large moment of inertia (stiffness) and a large section modulus (strength) compared to your proposed cross section.

The greatest strength/weight ratio for vertical load would be achieved using an I shaped section. It gets you the greatest moment of inertia and section modulus for the cross sectional area. The shell of the shelf acts as part of the top flange. It may not have the lateral impact resistance required, though. A rectangular section, while not as efficient as the tee section (but more than the triangular shape, has greater lateral strength and stiffness.

I suspect the current shape was used to maximize vertical load capacity while providing rounded edges and good lateral stability.

It's going to be a tradeoff between getting the most area at the greatest distance from the shelf shell, and having it sufficient for the lateral loading imposed on it. What you have proposed is fairly strong laterally, but doesn't give you as much vertical bending capacity as something with more mass at the bottom.

You have to come to a conclusion about what strength you need, both vertically and horizontally, and design a section that meets those limits, while meeting the other requirements, such as handling considerations.

If strength is more important than stiffness, you could consider using a higher strength steel to meet your goals.

Cost-wise, likely whatever is easiest to fabricate and attach will cost the least overall. There has been a dramatic shift in the cost balance of labor vs. materials in the last few decades. There was a time when labor was relatively cheap and material was expensive. Bridge girders had 5/16" thick webs and stiffeners every 3' or so along them. Today, the same size girder has a 1/2" web and no stiffeners, because the labor to weld all those stiffeners would be far more than the cost of the extra steel. You may find a similar situation as you investigate further.

 

[LittleInch]

If I'm not mistaken, the stiffener is more like a flat W shape. Would a simple square box shape not be simpler and use less material?

Your sketch doesn't match the photo

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[rb1957]

I'd be surprised in material cost was such a driving factor in your costs; I'd expect processing.

Looks like the the "shelf" (looks more like a table top to me) support has spot welded stiffeners. I'd've thought you'd get more bang for your buck making the stiffeners integral with the web, like a corrugated panel. The issue this creates is the processing required ... can you stamp the s/metal steel without processing it (before of after the stamping) ?

Try drawing your idea on top of the picture of the support. I don't really see a single triangle working.

another day in paradise, or is paradise one day closer ?

 

[BridgeSmith]

"Would a simple square box shape not be simpler and use less material?"

Yes it would, and it would be simpler to fabricate and have a bit more vertical bending strength. However, there are a few downsides to that approach, which is most likely why the current shape was used.
1) A box shape doesn't have the stiffness against racking, or bending laterally, that the current shape does.
2) A square edge can very easily end up sharp enough to cut someone, especially if it gets bent even a little.
3) Paint adherence to sharp outside corners is not good, a generally not even possible if the painting is done before bending. The easiest way to paint something like that is while it's still flat. The current shape can be painted as a flat sheet and then bent into its final shape while keeping the paint on the outside intact.

My advice is to investigate the reasons for the use of the current shape before assuming you can "improve" on it. Usually, I find that someone smarter than me put a great deal of thought and refinement into it before I came along.