What’s the point of having a structural engineer?

Building is expensive. The recent financial crisis proved that construction is a luxury, because during hard times we can do without it. For many people, property is the most expensive outlay in their lives. So when it comes to embarking on an expensive building project it’s important to make sure every pound counts.

So avoiding hiring a structural engineer may seem an easy saving. The Romans built all their great structures with an architect to provide the vision and experienced builders to make it stand up. What’s a structural engineer for? What’s the point of them?

What you get with a structural engineer is someone who can – using a scientific approach – tell you exactly how much structure you need. One element of that is judging the strength of the structural frame. In order to design a structure that is strong enough without additional materials, which are wasteful and expensive.

A brilliant demonstration of the potential of structural engineering came from a group of students a few years ago. They had to build a dome structure, 40cm high and hollow, with a kilo of spaghetti and some glue. The winners would be the group that supported the biggest weight with the least spaghetti.

A common sense approach might be to use triangles to make the dome shape. To make it easy to build you might use the same size triangles throughout and estimate the strength by averaging out several different people’s opinions. A reasonable strength to achieve from a bag of spaghetti is hard to gauge, maybe a few kilograms is achievable.

The engineering students in question, tested the spaghetti to calculate its material properties (how much force it could take and how much it bent for a certain amount of force). Instead of designing the whole dome as one unit, they approached it as a series of 10 arches, which combined together make a dome. Using some trigonometry they were able to work out the best shape for the arches. They then used some engineering software to check that there were no particular weak spots and that the whole structure would be working hard before any one part broke. By separating the dome into 2D arches, they could build the dome flat and them assemble it, making it easier to build well.

Spaghetti dome 3D and section
Spaghetti dome 3D and section

So what was the benefit of having a structural engineer? Well if a smart person had designed something and built it well, it might be expected to hold a few kilograms. The ‘engineered’ spaghetti dome held 195.5kg! Slightly more than the 190kg predicted. It performed so well that the engineering department had to bring in a new testing rig, as their first one only went up to 100kg.

So what’s the point of having a structural engineer? Well a structural engineer helps you to get every ounce of strength out of the structure. So although their services cost money, they can design something which is easier to build and without additional materials, which are wasteful and expensive.

If you speak German, you can read more about this example here.

16 thoughts on “What’s the point of having a structural engineer?

  1. Hi Becky, I just went over to the other blog as well, your writings are absolutely beautiful and touch my heart everytime I read them. (they always bring a smile to my face or a tear to my eye as well). I can’t thank you enough for sharing the storey of amazing Sarah and the incredible family that she has right there beside her. Sarah is one lucky little lady and you are an incredibly awesome family. (the picture of you and sarah is soooo nice, I just love it).

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  2. Hi Russell,We have updated the app to version 1.2 which contains an update for the live tile. There was an issue regarding threading when generating the LiveTile image.The realtime.txt text is very easily fetched with a HtesqebReWutpt then we parse the data from an Array. There will be an update utilizing the xml-standard from the Cumulus Weather station in the future.

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  3. rafaela pereira disse:Olá, tudo bem?bom, vou divergir da opinião das meninas acima, eu achei o tom muito foe08&#r23t; não ficou muito sutil.é minha opinião, o um importante é vc estar satifeita! ;D

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  4. I remember doing engineering activities in my physics classes similar to the activity listed in the article. I made a bridge out of tooth picks and had to test its weight capacity. It’s really cool that the students were able to use a series of ten arches to make a dome and use trigonometry on those structures to see what the best shape would be. It seems that having an engineer helping with the calculations and planning on a building would be a great asset for any building project.

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      1. tweeted about this give away…under EL2A;_MIE&#8L30EI tried to leave the link here so you can see it but your comment section will not let me!!!ELLIE recently posted..

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  5. I agree that there are many benefits to hiring a structural engineer who can use a more scientific approach. Their long term plans can often result in a more quality structure for you. I also think it’s wise when designing some kind of structure to plan for future maintenance needs, or even material replacements. With more efficient materials, hopefully this happens less often, but time still takes it’s toll on all materials.

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  6. I have always been curious about how structures get their design and wanted to learn a bit more about them. It’s interesting that they actually can tell you exactly how much structure you need in a scientific aspect. Since you are trying to make it now fall over, it would be nice to hear what you need from a professional.

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    1. Thanks for your comments, glad you found it interesting. Yes it’s a key part of the job of being a structural engineer to assess it scientifically. You could test the building by making a replica and testing it to destruction, but in most cases that would be too expensive to be practical. Professionals will also help you get the regulatory approvals and balance the design with all the other requirements (architecture, fire engineer design, lighting design, civil engineering drainage design, landscaping architect etc.).

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  7. I appreciate the information on why you should have a structural engineer. I agree that it is important to ensure that you are doing things right when it comes to your biggest investment in life and that hiring a structural engineer can help you to do that. My mom is looking into building a custom home, I will be sure to share this information with her.

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  8. You mentioned that what you get with a structural engineer is someone who can – using a scientific approach – tell you exactly how much structure you need. Do most construction companies hiring structural engineering services or do they have an engineer as part of their company? My cousin is thinking of starting his own construction business and is trying to decide who he will need to hire. Hiring a structural engineer could be very beneficial. http://bostonandseeberger.com/index.php/service

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    1. Great question! It would be worth him getting some proper business advice. In the UK, my experience is that medium-size construction companies might have a structural engineer for temporary works, but only large firms might consider having a structural engineering department. I think it depends partly on how much work you’ve got, whether you’d be able to keep them busy. Out of interest, where is your cousin’s firm based? If he’s looking to employ a structural engineer might be able to recommend someone.

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