The Critical Weakness of the I-Beam

[@Chasmodee1]

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.

[@LTVoyager]

As a fellow structural engineer (retired), this is simply click bait.

[@1985230ce]

@@LTVoyager it got me to click.

[@TonyRule]

25 seconds in and I paused to read the comments because it's clearly patently false. And I'm out.

[@LTVoyager]

@@1985230ce Likewise, but only once. I won’t be back to watch another.

[@jeffreykalb9752]

As a fellow engineer, I say "thank you" for some common sense.

[@NvTwist]

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.

[@TheEngineeringHub]

Fair point! A design limitation is probably a more appropriate wording.

[@adelarsen9776]

Breaking News : "Steel Mills Close After Flaw Discovered"

[@tubester4567]

Right. There are many ways to reduce the risk of torsion, like joining 2 i-beams with braces, which is what they usually do.

[@adelarsen9776]

@@tubester4567 Yeah, engineers aren't stupid. Bracing is amazing. Thanks :-)

[@ag-om6nr]

@@adelarsen9776 True , but some engineers lack common sense ! The good engineers have respect for the tradesmen working for them , and listen to their input ! Without engineers this would be a very different world .

[@geoffconroy3284]

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.

[@cprogrck]

This. Lol!!! I thought this video was gonna be oh so that's why they stopped using I beams.

[@jamescad9978]

I remember the beams in the graphics as being called "wide flange"

[@onradioactivewaves]

Exactly what I thought, I-beam is thicker where the material meets, the picture looked like what I knew as a wide-flange beam.

[@dar0971]

I think he’s referring more to the general geometry rather than the specific ways that geometry can be altered to improve its properties. Sure I beams don’t have sharp corners and have curves, but they still have the general shape of these other beams and therefore exhibit similar properties. A box section is very different from any I shaped beam

[@patmat.]

Yes he is referring to the general shape. Don't make things more unnecessarily complicated.

[@ByWire-yk8eh]

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).

[@TheEngineeringHub]

Thank you for your kind words. It's really interesting (also understandable) to hear that the same considerations went into designing a beam in 1969 as they do today. Computers are definitely a useful tool, but in our opinion, the engineering judgment and intuition is the most important tool an engineer could possess. This comes from a group of young structural engineers that do use computers quite regularly.

[@nick4506]

just had statics the prof has tought that same course for 40 years. same laminated examples and everything year in year out, only change he's made is to allow calculators in exams. the equations were derived hundreds of years ago and they ain't changing. same in physics, chemistry and math so why are textbooks so dam expensive.

[@milantrcka121]

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

[@felimz]

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.

[@TheEngineeringHub]

Thank you Felipe, this video was focused more on the weakness of the I-beam. We made another video on the strengths of the I-beam and its incredible effectiveness in carrying bending loads. You can check that out here if you are interested: kzbin.info/www/bejne/Y5K4XpSvp7OkfrM Thank you for your comment, we appreciate your feedback! We are a growing channel and we try to improve our content by listening to the feedback from the viewers.

[@R7Romeo]

I'm a carpenter and I 2nd that statement.

[@defendermodsandtravels]

Structural Engineering PhD. here too. I beams are most wideley used in cases where high bending resistance is needed in a compact section. . There are many situations where other structural forms are more efficient in bending (trusses, box girders, composite beams). No good for compression (H sections, CHS and RHS more efficient). Not good for biaxial bending either. Not good for high shear loads because of the slender webs. The list goes on. The secret is to choose the section according to the applied load to be resisted.

[@isaacm6312]

@@defendermodsandtravels Bridge maintenance engineer, and from my point of view a truss has many more weaknesses (upkeep costs and potential failure paths) over a long timeline than a steel plate girder bridge. Of course truss bridges can be designed with redundant load paths, but historically are not redundant. Simplicity in design (plate girders are typically fairly simple from a design standpoint) also has some advantages for analyzing and preparing for seismic loading, or so "they" say. Of course with longer spans these more efficient cross-sections can become a necessity. Also, bracing for torsional and buckling forces in a plate girder can be done with fairly cheap and available steel. Plate girders are essentially the backbone of the US highway system.

[@russell_szabados]

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.

[@davepowell7168]

Ignore 911

[@andyharpist2938]

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

[@alexanderSydneyOz]

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.

[@TheEngineeringHub]

You are absolutely right Alexander! The word "fatal" might bit a bit overboard though a flaw/weakness, we believe is an alright description. We hope you agree and still found the video entertaining and informative.

[@alexanderSydneyOz]

@@TheEngineeringHub ah! horse-trading about the precise wording? :) Absolutely, yes, it is informative and factual and a positive addition to the amazing sharing of information afforded by the Internet.

[@TheEngineeringHub]

That makes us happy to hear! Hopefully will be enough so you can forgive us about the click-baity title. Cheers!

[@johngormley2192]

The I beam is an open section, whereas the square is closed so better torsion resistance. A hollow circular cylinder would be the best against torsion until wall thickness is decreased and crippling or buckling will limit the design capability. Each shape has it's own unique strength and weakness.

[@deangoddley2061]

I think there trying to implement more reasoning toward 911. The buildings probably not made right. What a joke.

[@greggentsch2119]

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.

[@BillLaBrie]

Their obvious fatal flaw is that they can easily be melted by jet fuel.

[@howardosborne8647]

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?

[@TheEngineeringHub]

Thank you for your feedback Howard, we will fix that for the upcoming video!

[@lightningdemolition1964]

Agreed.

[@TEE19622]

Should have included "ominous music" if any and a reference to the possibility of this "fatal flaw" as the reason for the twin tower collapse.

[@drumcdoo9050]

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...

[@TheEngineeringHub]

very interesting case study! thanks for watching

[@stuarth43]

IRISH J. not made so much now, all UB

[@charliepearce8767]

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 ...

[@Rimrock300]

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

[@TheEngineeringHub]

We absolutely agree with you--thanks for the comment!

[@DEtchells]

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 :-)

[@TheEngineeringHub]

Glad you enjoyed it!

[@GOLDVIOLINbowofdeath]

Thanks for admitting your area of limitations. I watch a lot of van to RV conversions and I cringe every time the channel brags that they’re touring a van that belongs to an engineer without saying what kind of engineer they are. if they’re an electrical engineer, I would trust that they are doing their power systems and solar systems correctly, but as a structural engineer, I have yet to see anybody other than me That seems to have any clue about how to design the structural elements, and yet they are minivan, builders, both DIY and so-called professionals that make them self out to be experts in that area

[@David-hm9ic]

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.

[@amralawdi483]

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

[@TheEngineeringHub]

That's so nice of you to say Amr! Comments like this give us so much motivation to keep going, thank you!

[@diyVT]

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 .

[@TheEngineeringHub]

very good observation! The T-shape does have similarities to the I-shape

[@earluke2592]

Excellent - would have needed that for studying years ago.

[@hilbert551]

Pollo

[@lyndonthan4350]

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.

[@TheEngineeringHub]

Thank you for your kind words Lyndon! We are considering a video reviewing the various structural shapes and their pros/cons. Regarding the specification of S shapes, in our professional practice we have seen them for some aluminum sections used in hoisting assemblies during building construction. However, you are right that W shapes are much more common. Cheers,

[@alexanderSydneyOz]

Hi. What is an s beam? I could not even find a reference to it with a Google search!

[@lyndonthan4350]

@@alexanderSydneyOz W beams are I-beams which have all parallel/orthogonal surfaces. This makes them very practical for use in numerous situations. But such shapes are not optimal for various loading conditions. An S-beam is an I-beam with tapered flanges, rather than flat flanges. The flange roots are thicker than the extremities. The web is still flat. I imagine these beams have the material more optimally distributed than W-beams.

[@davepowell7168]

Vierendeel trusses with castellated beams is not mentioned?

[@kneedeepsnow16]

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.

[@TheEngineeringHub]

Thank you for the kind words :)

[@ACitizenOfOurWorld]

Exactly. One needs to show they deserved a thumbs up. And that can only happen at the end of the presentation, which in this case, it certainly did.

[@TheEngineeringHub]

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.

[@kevgermany]

Can't spell, can you. And why don't you also cringe and grovel for the false title?

[@GamingKeenBeaner]

People are being kind of ridiculous about minor terminology issues. The audio seems ok to me even if its not amazing. Its always good to learn and improve, but try not to forget that there will always be haters no matter what you do.

[@kevgermany]

@@GamingKeenBeaner when self proclaimed professional engineers post misleading nonsense, we have ever right to object. But I guess you prefer sensationalist alternative facts.

[@hafdone6931]

@@kevgermany lol pls continue spamming rude comments -- it helps the algorithm generate more revenue

[@GamingKeenBeaner]

@@kevgermany I just realize people are human and not everything they make is going to be perfect in every way. You'll throw out every valid point just to be a know-it-all about nuanced details. Its bothersome.

[@HiTechDiver]

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.

[@mtnman7776]

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

[@TheEngineeringHub]

We are sorry abput that 😕 We will improve that for the next video. Thank you for your feedback.

[@mtnman7776]

@@TheEngineeringHub, music has its place for filler in blank audio portions but a constant background of music, especially in informative content, is very distracting and the few second repeating loop of music makes me want to cram a small i-beam into my ear drums. I'm not alone regarding background music during talking, I'm just more vociferous about it.

[@geoffreyworley5853]

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

[@darrinjones9387]

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 👍

[@TheEngineeringHub]

Hi Darrin, Thanks for your comment :) Glad you liked it.

[@macedonia666]

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

[@TheEngineeringHub]

We are also glad you found our channel! The research, animation, and editing do take a lot of time but reading positive comments makes it all worth it.

[@RalphSampson...]

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?

[@michaelkelly339]

Rerun the video, he dooes show you why hollow is better than solid. Basically, the further from the centroid the mass of the shaft is located, the greater the torsional force it can handle. Add to that the weight saving due to having a hollow shaft rather than a solid shaft and there are the two good reasons for hollow shafts.

[@TheEngineeringHub]

Thank you ralph and Michael! ralph, Michael has done a great job answering your question. Thank you both for your comments. Cheers

[@dougholland7563]

@@TheEngineeringHub Thank you for sharing your knowledge. I would still like to see a video that explores solid versus hollow a bit more, in particular, the optimal wall thickness to achieve maximum stiffness. I am thinking about axles for trailers etc.

[@troyjollimore4100]

@@dougholland7563 The optimal wall thickness would change, depending on the axle length, diameter, and material used...

[@RalphSampson...]

@@michaelkelly339 So, really it comes down to weight and material (cost) savings. Surely, the simple fact of having extra material in the center would not be detrimental to the performance. Remove the center and use that material to build five more driveshafts....cost, right? However, I was informed in a high school automotive class that a hollow tube was stronger than a solid. I think with it being solid, it would allow the shaft to twist easier. I'm really not sure. If that is the case, why have any shaft solid (i.e. a steering shaft)? I really want to see the physics behind it. It's torsional strength vs bending, right? Will a solid shaft twist easier than a hollow shaft of the same material and diameter?

[@westinthewest]

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?

[@TheEngineeringHub]

Thank you for your feedback westinthewest. This was mentioned by several viewers and we took notice of it. Our newest video on Dams does not have background music. Give it a try and let us know if that works better.

[@benjigray8690]

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.

[@TheEngineeringHub]

Hi Benji, thank you so much for your kind words; we really appreciate your support. Trusses are indeed an interesting subject and now that you brought it up; we added it to our list of future videos. We tend to keep our videos to less than 10 minutes so we have to be very selective of what we decide to cover. As you suggested, we tend to break the subject into smaller videos that deal with different aspects (or failure modes) though sometimes it may appear that we neglect some important issues but it is purely due to time constraints. We don't know yet what the truss video will include but we will try to make it as informative as possible. Thank you for your feedback!

[@Arsenic_99]

Simply phenomenal. Your teaching style deserves all the praise.

[@TheEngineeringHub]

Thank you for the kind words Rameez, comments like this make our day.

[@jonnyrocket3659]

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

[@TheEngineeringHub]

Hi Jonny, thanks for you comment! We hope to inspire more young students to consider a career in engineering.

[@frankbanner8572]

In Australia rectangular and square hollow sections are manufactured with rounded corners and not as depicted in the presentation.

[@michealfigueroa6325]

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

[@TheEngineeringHub]

Glad we could help Michael!

[@stansbruv3169]

I’m not a structural engineer but I did stay at a Holiday Inn Express last night….

[@charleswhitehead7441]

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

[@Effisso]

I wish you had watched the whole video

[@charleswhitehead7441]

@@Effisso I did. It just seems top me that a tube would have been a better comparison than a round bar in the graphs

[@tigerseye73]

@@charleswhitehead7441 5:02

[@JoeFrickinFriday]

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

[@markhedquist9597]

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

[@TheEngineeringHub]

Thank you Mark! Your comment made my day. We are looking forward to making more videos :)

[@markhedquist9597]

@@TheEngineeringHub I recently watched a video on "Fletcher" (?) Beams. I think I have the name right. A length of plate steel, drilled, sandwiched between two 2x wood framing members, and through bolted together. As an alternative to an "I" beam with the same wood configuration. Opinion? Specs? Future video? Looking forward to your videos. Glad my above comment hit home!

[@DrJQureshi]

Thanks for sharing. What wonderful video. This will have impact for years to come.

[@lightningdemolition1964]

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.

[@gwillard19]

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.

[@TheEngineeringHub]

You are not wrong Enzo! An engineer that does not understand torsional loads is no good!

[@phpn99]

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".

[@TheEngineeringHub]

xD

[@w1swh1]

Yes ive heard of squircles ( see iphone icons) Seems a good design to me but I am not a structural engineer.

[@tamasmihaly1]

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_

[@greghawley7852]

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

[@DataLog]

Twin Towers are a prime example. Those towers were so poorly built that I would blame the engineers for 80% of those deaths.

[@darrellturner560]

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.

[@kibukun]

I still spit on car engineers. They really suck at making cars easy to maintain.

[@darrellturner560]

@@kibukun huh! Changing filters, spark plugs oil and fluids is hard? Where were you in the days of carbies and points. Still it wasn't all that hard unless you had a GM product with the distributor shoved at the back of the motor. I think you mean that when things do go wrong they are a costly affair to repair. A lot of that is circumvented with timely maintainance.

[@burnerjack01]

With a shout out to Newton and Liebniz. For without them, Man may never have leaned the language of the Universe. The invention/discovery of Calculus is what made proper analysis possible.

[@burnerjack01]

@@kibukun It's not them, it's their overlords and market forces. They now almost literally have to pack 10# into a 5# bag.

[@darrellturner560]

@@burnerjack01 simple musical instruments used measurements long before formalised math appear. All knowledge is built upon by the next so no one person can truly be acknowledged as the fountain of any one thing. Great minds tend to open doors left closed by others who were often held back due to social constraining beliefs of their time. This is very apparent especially in the astronomical, maths and medical fields. Many a brave person speaking out had their life cut short. Not to mention the loss of the great Library of Alexandria.

[@tnsoftailrider]

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

[@Alan_Stinchcombe]

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.

[@TheEngineeringHub]

Thank for your feedback Alan. We value our viewers input and tried to apply it to our new videos on dams. If you have a second you can check it out and let us know if that works better for you because we want to provide equal entertainment for our hearing impaired viewers as well: kzbin.info/www/bejne/bpWVpntoedx-fa8

[@mdj.6179]

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.

[@josepeixoto3384]

And they got thinner on the process,needed re-calculation.

[@mariasrensen5927]

Really great video! Love your content 😊

[@TheEngineeringHub]

We are so glad to hear Maria 🏗👷

[@michelangelocardin9088]

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

[@mgx8381]

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.

[@TheEngineeringHub]

Thanks for your feedback! We will consider this for our future videos

[@bpj1805]

@@TheEngineeringHub Particularly since your voice trails off, often at the ends of sentences, and becomes nearly completely unintelligible due to the music overpowering it.

[@Effisso]

@@TheEngineeringHub Better quality mic/software/sound engineering would improve this. The mic sounds like a mid-tier mic from 2012.

[@ethanchandler2792]

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

[@TheEngineeringHub]

Glad you liked it!

[@paulthesoundguy1]

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

[@TheEngineeringHub]

That's good to hear Paul, thank you! We had a few comments from other viewers expressing their annoyance about it.

[@todd5082]

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

[@JohnB-pp5dn]

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

[@localeightironworker]

I have been ironworking for 15 years and have only seen standard I beams a few times. almost every beam you will see going in the air nowadays ( in wisconsin ) is going to be a wide flange beam.

[@MichaelClark-uw7ex]

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

[@Bratfalken]

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.

[@ninjaneerk5601]

What you call buckling may just be an intentional curve in the beam. Beams are sometimes curved (cambered) upward so that when they are loaded they will lay flat like you said. A few meters sounds like too much to be camber, but I'm not a bridge designer. It could be that the designers just want the bridge to curve up over the river. Buckling in an I beam occurs to the side and also causes the beam to rotate, so the curve in the vertical direction is nothing to worry about.

[@2019kartik]

What would you say if we have the web corrugated,for an I Beam. How would that effecr

[@TheEngineeringHub]

Hi Kartik, To briefly answer your question, the corrugated web can offer some additional resistance against web/local buckling. We are considering to do a future video reviewing various structural shapes--perhaps we can include corrugated web I-beams in that video! Cheers,

[@bpj1805]

How would you make such a thing cheaply, ideally in a mill spamming hot steel through rollers at multiple meters per second? Also corrugations are give extensional elasticity, which you don't want (although the flanges should take most of the stress).

[@akdrn3624]

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

[@daszieher]

No. Engineers like more calm narration. It was actually very comforting to watch. Not every video needs to be narrated by Hulk Hogan or attempt to make trivial things "exciting". Nicely done!

[@Eyes0penNoFear]

If you want to give it a bit of zip, change the playback speed to 1.25x

[@wyndwalkerranger7421]

Section shown is a wide flange or W section not an I beam.

[@scottyd2262]

Building 7 was made out of square beams... mic drop

[@nimrodaviv1544]

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

[@tenpoll]

Fire your sound engineer. Voice need to be uppped while music need to be down!

[@peterfitzpatrick7032]

Would crowning the top surface help to keep the load on centre ?

[@TheEngineeringHub]

Hi Peter, That's not something we've seen in our engineering practice before. More often, we see either the I-beam or the point of load application moved, or stiffeners/braces being added. Thanks for your comment!

[@dabeamer42]

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

[@3_14pie]

I don't know why KZbin 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)

[@mastmec]

Those are w-beams not I-beams

[@TheEngineeringHub]

Thank you for bringing this up mastmec, the beams are in fact wide flange beams though many people in the engineering and non-engineering world would still call them colloquially I-beams.

[@kermitbearden7142]

@@TheEngineeringHub People still say angle iron.

[@j.e.v.5016]

As others have said, it's not necessarily a flaw but property. I-beam shape is optimized to resist bending, just as circular shape is best to resist torsion. It's the combination that requires compromises. You can increase I-beam torsional resistance a bit by thickening the flanges. This might be enough if torsion load is small compared to bending - like due to small manufacturing errors the load application is a bit eccentric. If the torsion-bending ratio increases, the next step is to box some of the I-beam length. This increases its torsional rigidity considerably. If this is not enough, then hollow section I-beam might be the answer, especially with high strength steels (S600 - S900) although it's much harder to build. Other way to approach the situation is to take HSS profile and add material on top and bottom, thus increasing its bending resistance while keeping its torsional properties. As always, engineer has to balance between application, manufacturing and cost. Usually the simplest solution is the best.

[@gertkoegelenberg106]

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

[@TheEngineeringHub]

duly noted!

[@TelosDextroza]

🤣🤣🤣

[@darkredvan]

Well, it all depends what you want your beam to do, what you need it for. Some beams have this weakness, some have others. It is the job of the engineer to chose the right one for the purpose. There is no jack of all trades beam. For any given purpose you chose the right beam. If you have done it right, the weaknesses are less than any other beam. Simple, isn‘t it? Great video btw, thank you for posting!

[@TheEngineeringHub]

Hi darkredvan, We absolutely agree with you there, different shaped beams are suited for different applications. We hope you enjoyed the video. Cheers,

[@ding9633]

This reminds me of how I learned 100x more at a community college than I did at a university for engineering.

[@boblordylordyhowie]

You will learn more from doing it, than you will from reading about it, especially if you are curious.

[@texasRoofDoctor]

I want to build a 3 story ferro-concrete house and am planning to use i-beams to support floor joists. How far apart should I place support columns and what is max gap between i-beams to support such a structure? I plane to use something really light like Foam-Crete for internal non load bearing walls.

[@jeice13]

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

[@SteveandLizDonaldson]

Great video with exceptional graphics. But I would agree with the others that torsional stability of an I-beam is NOT a fatal flaw as you state in your title. It's just another failure mode that needs to be understood and addressed by engineers (I am one myself). Also, at 5:02 you hinted that a tube is better in torsion: true, but it has limits too on how thin the walls can get before they, too will buckle on the surface.

[@TheEngineeringHub]

Yes definitely, you are not wrong. We called it a flaw from the perspective that a small change in the load location reduces the carrying capacity drastically. So we thought, if a small change could bring down an otherwise strong entity then that must be its weakness/flaw. We are still learning as a channel and observing how the audience reacts to our content so we could get better in the future. Thank you for your feedback!

[@SteveandLizDonaldson]

@@TheEngineeringHub We engineers are a nit-picking bunch, so please don't let that slow you down from producing great content to especially get young folks interested in and learning about STEM topics! So, I've subscribed and wish you all the best.

[@trevthreader2689]

So a cylindrical tube resists torsion forces better, but does it outperform I-beams or square beams in dealing with compression and tension forces?

[@i12flytoday]

This video wreaks of statements that sound like a mid first year intro to engineering student would make. Basically, don't use a structural member for something it isn't designed for. i.e. Don't use an I-Beam for a driveshaft.

[@samngai6179]

MSc student in structural here... and I just wanna say this is exactly what I have been after during these 5 years of struggling

[@TheEngineeringHub]

Glad it was helpful!

[@RHJ3]

'Critical Weakness' is the hook, KZbin 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*

[@michaelmaolchalaan4603]

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

[@165Dash]

As an architect, this gives me a good general idea why I see so much use of HSS members, particularly in those quirky conditions with asymmetrical loading that we always seem to be creating for our structural engineers to “solve”.

[@TheEngineeringHub]

That is exactly right 165Dash, it is very interesting for us to hear how our colleagues from the architectural side feel about this since we are structural engineers. Thank you for your comment!

[@sroberds640]

So if we weld in side plates making it a tube with beam down the middle most of the torsion effect would be removed? Extruded would be better cause then you could get rid of the sharp inner corners.

[@ericbechel4434]

The government would like us to think burning jet fuel is the weakness of a steel I beam.

[@josepeixoto3384]

Fatal or not, now or later, with unpredicted loads and torques,one *better* be aware of this; thank you very much for the video

[@baliholy165]

So i want to redo roof in concrete building using steel beams & aircrete stuffed with styrofoam for natural solutions and some rooms. What diameter of circular hollow steel beam for heavy loads do you suggest?

[@alyssonpiccinin]

Reclamar que uma viga W não resiste torção é reclamar que um carro 4x4 é incapaz de andar sobre a água.

[@manojdangi7655]

Best explanation of concept waiting for more vedios like this✌️

[@husq2100]

Great video , thank you. One question, why did you make the circular beam solid? Given the only constraint was equal square area, surely it would have performed better as a tube?

[@TheEngineeringHub]

The reason is two fold, first because our older video had these exact three shapes so we thought it would be nice to use the same shapes for comparison. Also, since we already had a closed shape (the square tube), and an open shape (the I beam), a different category of beams might have been better so we went with solids. That was the reasoning in the first video at least, for this one we just continued with the same shapes.

[@bcubed72]

How does the C-beam (as in many pickup truck frames) differ in characteristics from the I beam?

[@eyesonly4451]

Our factory has 130' clear span frames spaced 30' apart. At one location we required a 60' clear opening through the side of the building into the adjacent, preexisting building. This meant that one of the frames would need to have that end suspended from the center of a 60' beam using an L-shaped hanger device welded to the side. To prevent the whole thing from rotating, the L-shaped hanger is also horizontally connected to the adjacent 130' frame with a 30' x 10" diameter hollow pipe. I get nervous every time I look up and see it.

[@SpiritofDaniel]

You learn this quickly when you try and pick up a long I-beam from one end. Often times the best compromise is a rectangular box beam.

[@Gottenhimfella]

That's a way of assessing torsional *stiffness*, not strength. While this also happens to be very low in I beams, it's not a good idea in general to use stiffness and strength as proxies for each other.

[@Ind421]

Moment of inertia is discussed in case of beams which confuses me though there is no rotary motion.I was told that it is called second moment of inertia.Will you please clarify?

[@TheEngineeringHub]

Hi Premkumarguttikonda, moment of inertia is also referred to as second moment of area. Actually there is rotational motion, this motion is the beam being bent. You can imagine the curved beam as a section of of a circle with its center somewhere above/below the beam. Check out this picture to see what I mean: ptgmedia.pearsoncmg.com/images/chap5_9780134859286/elementLinks/ugural_f05_25_alt.jpg It is a confusing concept, the key is not to think as normal rotation of a rigid body about a point/axis, because it is clear that is not happening. But rather to think as parts of the same body being rotated about their own axes. In this case, if you imagine the beam as a sequence of cross-sections glued together then rotating each section (e.g. section bc on the link) by a small amount (the dashed line on the link) would produce a bent beam. That's where the rotation is hidden.

[@carultch]

It has a lot of properties in common with mass moment of inertia as is used in rotational dynamics, but the property of structural sections that gets called the same term, really has nothing to do with inertia. The area moment of inertia or second moment of area, as is used as a property of structural sections, is purely a property of geometry. It doesn't depend on the identity of the material. Instead of integrating r^2 relative to an infinitesimal mass element, we are integrating r^2 relative to an infinitesimal area element. Area moment of inertia is a property of a structural shape's resistance to lateral loads like bending and shear. Or, the polar moment of area for circular shafts, for resisting torsional loads. For composite beams, we account for Young's modulus varying throughout the section as part of the integral So the centroid gets replaced with center of elasticity, and the second moment of area gets replaced with integral E*r^2 dA, rather than E*integral r^2 dA, because Young's modulus (E) is not unifom.

[@andymanaus1077]

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

[@briansmith8079]

What's failed to mention is the strength in a rectangular section tubing. The tubing size for size can resist torsion, buckling and deformation far better. But as in all things a WF beam or Ship Channel with tapered flanges and larger radius fillet will indeed out perform the tubing in a similar application. What's critical is the side loading, shear forces, penetrations, application, asthetics, weight or deadload and moment requirements.

[@JohnSmith-kf1fc]

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

[@DanBurgaud]

4:30 what about round hollow pipe instead of a rod?

[@patmat.]

Great summary and illustrations ! Thank you.

[@kex7294]

Thank you for sharing your knowledge with us! The title is a little bit overdramatic, which I don't blame you for, but I do think that you should expand upon a little more. My top suggestion is to change the tone of your voice, but changing the pacing, length or word choice may also work, if you still aren't comfortable with talking to a camera in that way. Other than that, great educational content!

[@TheEngineeringHub]

Thank you so much for this constructive feedback Kex. This is the only way that we could improve. We will keep these things in mind for the next video. Also many of you mentioned that the background music is annoying so we also removed that. Hopefully our latest video on dams addresses these issues better. If you have a second you can check it out and let us know if that works better: kzbin.info/www/bejne/bpWVpntoedx-fa8

[@MajorCaliber]

But, but... analyzed _in situ,_ the same cross-braces that resist global buckling also resist torsion, oui/non?

[@TheEngineeringHub]

Yes absolutely, it definitely helps but doesn't solve the issue.