The Critical Weakness of the I-Beam 

As a mechanical "structural" engineer for over 35 years, I must disagree with the idea that an I-Beam has a fatal flaw. When designing anything, there are typical, predefined structural members that, if properly used, will result in nothing but a successful design. The error here is a misapplication of a known element of design. For instance, one can not say the nail has a fatal flaw because it does not hold steel together or welding is flawed because it does not attach wood to steel.

There’s a massive difference between A flaw in the design & a design limitation. If a engineer choose to use square tubing in place of an I- beam its not the tubing thats flawed… its a fatal flaw with-in the engineer not the tubing.

Very well explained, and it demonstrates the kinds of choices structural engineers make. I saw this in an engineering statics course I took in 1969. Hasn't changed much expect that now computers can model these structures much, much, much better than we could with slide rules (slip sticks).

Structural Engineering Ph.D. here. Good content and animations, but the video fails to acknowledge why the I-beam is the most efficient shape in steel structures. In fact, its popularity likely is an indicator or how non-fatal the torsional I-beam weakness is and, as you have noted, there are plenty of ways to mitigate this weakness from a design perspective. Good job, keep the videos coming.

We apologies for the audio quality and loud background music. We are a growing channel and we learn from our mistakes, we will correct this in our future videos. Also, many of you mentioned that the nomenclature of the beams might be different than the one used in your region. The name varies from place to place. In Canada, where our professional practice is, we colloquially refer to all shapes (W, H, S) derived from an "I" as I-beams. We understand that it is most likely different in your country/region.

Abundant examples of I beams vs. hollow tubes were evident in New Orleans after Hurricane Katrina. Every billboard in the area that I saw that was supported by I beams bent until the sign reached the ground. Every one I saw that was supported by tubular steel was still standing. As for the video, it leaves out a great deal of significant information.

Yes, that is quite instructive, though it seems unwarranted to call it a "fatal flaw". Rather, as I take the video, all configurations have their weaknesses, and torsion is simply the I Beams weakness. So it is used where it won't see those forces.

The illustration is not a 'I' beam but classed as a universal beam, 'I' beams have radii in the corners universal beams do not hence they do not have the same resistance to torsional loads.. They are cheaper and therefore easier to manufacture.

An engineer will choose a beam shape or construction design that gives equal resistance to all of the these failure modes. A thicker flange will help prevent tortion failure

Excellent explanation with accurate illustration , please don't stop making videos like these

This video finally explains analytically something I've intuitively understood for a long time. Nicely done.

Ah! Great vid! I’m an EE by background, so am light on mechanical topics and concepts. This was a great explanation of torsional stiffness! (It was great; as you were explaining about continuous flow and distance from the centroid, I was thinking “What about hollow cylinders? They’d be the best, right?” Then you showed the hollow cylinder 🙌😁) I’m a new subscriber now :-)

Excellent - would have needed that for studying years ago.

Great stuff. I am so glad that found your channel. You must be spending a lot of hours researching and editing. Really appreciated 🙏

I love your channel, I love your explanations… Most of all I like how you’re humble and request/remind the viewer to subscribe or to thumbs up at the end of the video. I hate it when channels ask at the beginning of the video. I have seen many other ways that are fun to remind the viewer. But I think your method is the best. Thank you very much.

This could have been really informative and educational if it weren't for the silly music competing with the narration. Is there really any benefit from overlaying music on a scientific/educational video?

Interesting... When Buncfield Depot, an oil storage facility in Hemel Hemstead UK blew up on 13th December 2005, many comercial buildings under construction within a few hundred yards ended up destroyed. Massive RSJ's (I beams) were left with twisted and buckled from the shear force of the explosion making it look like a war zone. So yes, can understand the limitations of these beams having witnessed the results first hand...

Simply phenomenal. Your teaching style deserves all the praise.

Brilliant clear description of the weakness of the I Beam. Clear and concise and co

The video of the beams really helped visualize what u were describing. Thanks!

Great topic and well presented. To make a fair comparison the cylindrical shape should also be a hollow tube to compare with the square tube. Then you would find the most efficient shape for torsion. Most of the large structures, crane booms, etc. are built with hollow shapes rather than solid shapes.

I’m not an engineer, I’m a musician. But this video satisfied an intellectual curiosity about structural engineering, so I’m looking forward to checking out more explanations about what makes large structures sound and long standing.

Great summary and illustrations ! Thank you.

Quite instructive. Destructive is the "music". Please drop it!

I-beams are great in general, one just need the knowhow during design regarding staying well under the limits to avoid issues. Great video

I subbed! This is quite educational, and I love it. Learned a lot! Keep it coming!

Wow! Awesome educational video! Love the insights on this one! Also helped clear my headache too!

I'm glad I stumbled upon this channel. Very good stuff. Designers of walk-ways aught to study this video so that fewer people end up _plummeting_

I used that basic principle to make a flexible set of saw horses that can conform to the ground but still Carry a heavy load. The top is T shape which shares many of the strengths and weaknesses of a I .

Really great video! Love your content 😊

Thank you brother, stay blessed.

Very helpful video. thanks for posting! :D

Thank you for making a really interesting video. you obviously understand your subject, , , and, you are able to explain it in nice simple terms. Many folks that know their subject are not very good at teaching it. You, however are a good teacher. A rare thing! To introduce students of engineering to some "real world" problems encountered by folks designing industrial type buildings, like storage or farm machinery sheds, that often have lightweight web trusses to make wide "clear span" sheds, mayhaps you might make some videos that show how simply by adding small braces, that go from the underside of the lower web of the truss to the roof purlins can increase the truss's carrying capacity( resistance to torsional bending forces). Torsional resistance can be increased in so many ways, ask any steel fabricator. I realise that in a short video you can't cover all variations, mayhaps a series of videos, might be the answer.

Very interesting. The vast amount of knowledge in any given subject matter is staggering. Even if one knew everything to date, technology changes so fast there are new things to learn every day, let alone current knowledge.

Really cool video! Appreciated.

Really informative I am glad I saw this..

I learned these by practice. I been a carpenter 40 years. You learn what works. Just throw around a smaller, lighter beam on the job site and you can see these flaws. Great instructions 👍

Interesting resource for students of engineering or those considering a career in engineering

This is great, i didnt know i needed to know this but i did! Subbed

Fantastic video with very useful visuals and animations. I liked the music as well

Great video! This video made me think of the forces placed on a hollow driveshaft of a vehicle. Can you do a video explaining why it's better to be hollow vs solid?

I wish you had added a circular tube in the mix with the square tube, I beam, and round bar

Great demo 👍👍👍

Interesting video. Thanks!

As an engineer that specifies beams almost daily, I enjoyed this video, and yes, as others have said, GREAT work. I often do think about the weaknesses of I-beams, and their suitability for a given purpose, as you've stated. For a future topic in this same thread, it might be nice to discuss S versus W beams. Despite years of design work, and designing not only buildings but also trailers, cranes, and even magicians' props, I've never had to specify an S beam. I've seen them used in conveyance work in factories, but never in building structures.

I just watched a video by Waldos world about building a gooseneck trailer. He included a small hollow round tube between the I beams and welded a plate to each end. He did this to reduce twisting of the frame especially when empty. I thought that it was a lot of extra work when he could have just made the beams bigger. This shows that a little material in the right place can go a long way.

This video answers my question in the previous video about c channel. Thank you.

Very interesting , very clear 👏🏼👏🏼👏🏼👏🏼

The ideal shape would be based on the Lp norm, with a factor between 2 and infinity; a value of 4, 5 or 6 seems like a good compromise. Some such designs are sometimes called "squircles".

Answer me this: why do creators take a perfectly good video and completely ruin it with continuous background music?

Hey lad thanks for sharing that wisdom with us! Great job

I've been in the building industry for years in my younger life. Now older retired guy, i built a hydraulic log splitter with a large "I" beam as part of the machine . After using this machine for 15 years im surprised every now and then how this i beam wants to "Twist" under heavy load... Ive never seen this happening in normal applications... I ❤ my log splitter ...

Good video. Nice job of explaining the difference between shapes. But I wouldn’t say the I-beam has the fatal flaw. That flaw would be on the engineer who didn’t take into consideration the weaknesses of the shape and failed to account for them in his design.

Also a nit, but eccentric is ik'-sen-trik and not es'-sen-trik. Informative video. Liked it.

Very interesting video, thank you. Well presented, too.

Excellent explanation ! Thanks

I take my hat off to engineers and design engineers. They are the true magicans of our modern technical advancements. Without them medicine, physics and science would srill be operating in the darkages. A good video for helping lay people understand some of the complexities in constructions they utilize everyday.

Excellent presentation. Visual contrast was a bit low for stiffeners. There was also an audio signal-to-noise ratio issue for me. I have impaired hearing, so would benefit from less background music, preferably none.

great theory, well done

Excellent lessons Professor.

WELL DONE PRESENTATION….NO ISSUES WITH MUSIC….ADDED TO THE QUALITY OF THE VIDEO

On many instructional videos, like this one, I notice they add music in the background. While I am trying to process the technical information and possibly memorizing it, my brain also has to process music as well. Although music is good for some, it is not good for all. I wish they would give us a button to cancel the music if we so choose.

Awesome, thanks 👍

few too many comments on how much quality there is in this video! very good quality

I got a bit worried when I saw the newly buildt bridge over the river in my home town. It is a concrete road surface on three high I-beams and now that they removed the pour supports I found that the beams have intervalls of diagonal buckling, the beams are arc'd and a few meters higher in the middle of the river than on the ends, the bridge is some 310 meters long. I do hope the buckling is from pre-stressing and that it would straighten when loaded, it is a new bridge that will replace the 65 year old arc'd concrete boxshapes bridge that had tension wires inside so that the new weightlimit if trucks here in Sweden can go up from 60 tonnes to 74. And both bridges can be seen on Google Earth at the moment in Kalix, Sweden. The new one is almost done by now and is planned to open within a month from now.

Too bad he's showing Wide Flange images, not "I" beam, which are now technically called "S" or Standard shapes.

Best explanation of concept waiting for more vedios like this✌️

Helpful, thanks!

Great content even though a bit more sparky narrator won't hurt...

finally figured out you were saying "eccentric" -- it's pronounced EK-centric

Very informative thank you :)

Fascinating!

Those are w-beams not I-beams

A little more energy in the voice, I am falling asleep

Great explanation

awsome video!i wish my teacher in the University would use these kind of visual explanations.

Great video

Nice presentation 🙂

Great job

Excellent

Good one!

thank you very much

I want more videos like this.

The nature of this content makes background music incongruous. Could you please try doing the next video without any such adornments - just to see if anyone else prefers it?

Thanks sir

I once saw a video about square solid driveshafts driving old factory equipment. When they were machined round in places to spin at supports they snapped because of the lose of torsion strength.

The alternatives you were comparing seem like they would be more expensive to produce though, with the possible exception of the filled cylinder that is probably both harder to work with and weaker

This explains why so many construction projects are now using box beams. I wondered if there was a strength difference.

This helped me understand why box tubing is used in home built car fames rather than I Beams TY

cool video!

The railroad bridge at 1:16 is the Ten Mile Bridge just downstream of the Chickamauga Dam on the Tennessee River in Chattanooga, TN.

very cool video

'Critical Weakness' is the hook, RU-vid creators need views and likes to keep creating content. The algorithms do not lie, without some form of drama in the title there are not as many views. Many titles are outright misleading and are considered click bait, but this title is not misleading, it's engaging. And the 'Critical Weakness' aspect has brought in a lot of views even if many are discussing if the title was misleading or inaccurate. Hats Off to 'The Engineering Hub' for creating an interesting video that has spawned many discussions. *Cheers*

Now I know why vehicle drive shafts are usually hollow round sections rather than solid.

I would love to see a video on torque boxs

Thanks for using metric!

thanks

I don't know why RU-vid recommend this to me, but I am already intrigued and wanting to learn about I-beams (whose I didn't knew had a proper name)

Thank you.

The two drone shots of the train crossing the bridge is from below the Chickamauga Dam in Chattanooga.