Dear Mr. Paul Kassabian, I had the privilege of being part of this class, which to me, has been one of the most rewarding experiences provided by GSD. I express my gratitude for your efforts in creating such an engaging and productive learning process. Thank you.
Must kinda suck to know the most rewarding part of your experience there resulted in a quick free to view youtube video showing that you can do at home for about $100 with extremely simple explanations.
We had this type of excercise in programming class in college. "write a program that finds all prime numbers between 0 and let's say 100.000 as fast as possible". 3 times a year you made this excercise. Everytime you find something to improve in your code or algorythm.
Maam I have to say, your Dad had it rite. Zach was wrong, now just imagine. A 1/4 of a million Dollars to replace what he' F[EXPLICIT]ed up for you. You'r name, name your family...
@@PaulKassabian nice reuse of the Ottawa University materials science lab final exam project ... you missed having them do a full failure analysis on the end result as well ... back when I did this at Ottawa University in 1987 the report was 1000 pages long and the bridge I built carried 573lbs of weight before a miniature knot in the wood gave way ... more was learned from that project by everyone INCLUDING the professor that he kept at it until 92 or 3 ... . Balsa and string at 5lbs total bridge weight ... pre tensioned for 500lbs ..
@@PaulKassabian I wonder if you would entertain having anyone that has watched these, and has not had formal engineering to submit a design for one of your student teams to build? Simply put, the team should choose a bridge out of a “pot,” and make it according to the spec given. I would do this AFTER this competition, and as a bonus point to their score if they choose well.
@@PaulKassabian hi, Sir. I would just like you to know how much I admire your giggles when the bridges are about to collapse. Proves that you're emotionally invested in your craft. To my memory, my best tutors has always been those who truthfully enjoy the subject they're teaching. I'm sure many of your students will remember you and your lessons for the rest of their lives. Hope this comment reaches you; thanks for the video!
RU-vid amazes me how it shows me things I never knew I was interested in. A phenomenal teacher and I imagine every student is proud to have studied under you.
low learning curve tbh yes this is a project that is fun but clearly if you are of the mind of "what will fail" then you can almost make the teachers run out of weight
Paul my father was a bridge engineer and worked his whole life building and maintaining structures. Your passion, enthusiasm and attention to detail reminds me very much of him. Wonderful teaching and great to see some engineering passion. Thank you.
@@PaulKassabianthe one thing I like about spaghetti and glue is that it is even structural strength all the way through and you're not going to have some wood that's stronger than other wood making someone structure appear stronger than it actually is architecturally...
I remember doing this in high school in my architectural engineering and design class. My little balsa wood bridge held 176lbs before giving out! Great fun and an awesome learning experience!
there is NO substitute for hands-on application and learning. Engineering colleges are failing miserably at this of late. This is a perfect example of how learning should be done. Hands-on application, with a little trial and error. Let them test their ideas, take notes, and try again. Couple this with classroom learning and you have a winning combination. So much wasted opportunity in engineering colleges to really give students a truly great education with little extra effort.
Thanks! It really made a difference with, as you noted, the coupling with classroom learning...it's like concrete plus reinforcement...better together!
It would be amazing to start a class with a two week build like this, then finish it with another two week build to let the students demonstrate what they’ve learned.
I participated in one of these exercises back in college (35 years ago). Our span was to be roughly 18”. Material efficiency was the goal, so I made mine very light. The weight being used were bricks. Knowing the size the brick, my design used the first brick as a structural element. We ran out of bricks and the bridge never broke. A fun memory. Nice video. 👍🏻
Just an outside admirer here. I have to say, professor Kassabian reminds me so much of my physics professor. Someone who truly cares about the subject, his students and their overall engagement with the material and makes it all fun at the same time. Well done! Even though I am a graphic designer, I am always interested in all engineering subjects. And I f I had someone like YOU back in the day, I really think I would have become an engineer just because of the way you teach. Well done sire! Well done.
That was amazing to watch as a spectator, I can only imagine the problem solving and learning plus team building that took place to get to the test of all 13 bridges. Thank you for taking the time to record this and let all of us participate.
🎓✨ Mr. Paul Cassabian, I want to express my sincere appreciation for the incredible learning experience you provided through this class. It was truly a privilege to be a part of it. Your dedication and effort in creating an engaging and productive learning process are commendable. Thank you for enriching our knowledge and inspiring us to reach new heights. Grateful for this opportunity! 🙏🏼🌟📚
We did something similar in my civil eng class 35yrs ago, with a fixed amount of balsa wood for each team to span a 400mm gap. Fascinating to see the much more elaborate designs in the video.
Now that reminds me of the college I went to between 1973-1976. It was ALL hands on. 2 years of forestry, we were in the bush just as much as in the class, learning by doing. 1 year of welding and fabricating, skills I've used my entire working life. Keep doing it this way, we need people who THINK instead of parroting the party line they are being indoctrinated with. Those young people are having a blast, putting what they learned into actual use.
The problem with weights on top is that balance becomes a factor. The weight should be in a basket that is hanging from the center point of the bridge deck.
Yes, it's amazing that the one to carry the most weight was the only one that wasn't subjected to twisting forces. Some of the others may have done much better if a portion of the weight had been suspended below in buckets as it was on bridge 13.
The first one would have done even better if the loading had been vertical. Some bridges received loading that was much more vertical than others. Suspended weight would have been a more accurate test of relative load bearing.
@@Tohellem there are plenty of twisting forces that a bridge encounters, from having more weight on one side of the deck to wind pushing on sections above or below the deck.
RU-vid watchers suddenly clicking a lot more bridge related content than normal and the algorithm recognizes the uptick and recommends videos accordingly.
As a high school educator we have made spaghetti bridges. I have used timber before also. Spaghetti is generally used due to financial and or time constraints. The students are amazed that spaghetti can hold so much weight. It’s a great project, regardless of material, though I would want senior students, like those studying architecture to be using materials closer to those which bridges are made of. It’s interesting to discuss with students shock loading, UDL..etc. great video. Would be interesting to know what constraints you gave the students.
Harvard doesn't think much about the financial constraints. I'm in agreement that spaghetti is a good tool for younger folk. I remember a summer camp activity at the local community college that used glue and index cards to make a bridge. Lots of corrugation :)
Why not use popsicle sticks? A wonky bridge I made couple years ago held 400lbs+ while weighing 350g or so, it was one of the most memorable and impressive things we did at school
Spaghetti is a very good analog of concrete. They have almost exactly the same bulk modulus. It would be more accurate however if fine steel wire reinforcing was added…
It’s not a matter of knowledge, but a matter of experiences. But if you look only at knowledge, you will find a lot of better university than Harvard, even in USA. To know who they are, just watch where the big ingeneering compagnies get their new recrutes.
I love this! In highschool my absolute favorite class was drafting, all T squares and velum. We did a bridge every year and if you got to around 850 e factor you were doing pretty good. They were small and the best ones were relatively simple and light. He lets and my partner do a suspension bridge, nothing like this though. We pulled from the bottom and had a share built into the bridge that accepted the tray pulling down and put weights on the tray.
So nice for them to actually be creative and do their own design. When I had this class in university we had to recreate a moving model of a bridge that actually collapsed and recreate the the conditions that led to its collapse. If your bridge didn’t collapse or collapsed the wrong way you failed the class, while the professor was asking questions about the forces involved and theories behind the collapse. Some people got some really weird bridge collapse cases that were very difficult to recreate.
I remember doing something similar to this in my Highschool physics class. We had to span a 1-foot distance between two desks using only plastic straws to make the bridge. I remember making a crisscross arched bridge that held up very well, it was a fun time trying to think of a bridge that would work.
We did something like this in Grade 5 with glue and toothpicks. Obviously not at the same span or weights but it was one of the most memorable projects of my school years. Glad to see this video!
Yes! Toothpicks and wood glue are great for this contest. It has to be a particular brand and type of toothpick for an even playing field. Span a 12” gap and of course the weight should be hanging underneath from a specific sized block of wood that is placed into/onto the bridge. Sand can be used to fill a bucket hanging underneath. I participated in this at my elementary school’s science fair in the 80’s.
I cant believe that I've watched all of your videos and I barely recognized that additively manufactured part that you have at the background! What a masterpiece!
I was IT teacher for 6yrs and had students do their own projects with a common goal. It was just amazing to see and feel the enthusiasm by everyone, except one that wasn’t really into IT.
@@acyweiThat’s when I was the most annoyed when he was talking about looks, all I care about is functionality. It’s not art, it’s a structure designed to hold heavy loads while being as cheep as possible.
I would recommend AGAINST putting non-functional judging into something that's strictly an engineering discipline. Do you know why STEM isn't a buzzword anymore? They diluted it to "STEAM" by adding "Arts" to it. Then later on they killed it with "STREAM" by adding "Reading." This is also the difference between Japanese and American automotive engineering. Americans usually start with aesthetics first and the shoehorn the engineering into it, while most Japanese manufacturers over-engineer the mechanics first, and then add the aesthetics later.
@@matthewxavier8067 Some bridges have stood for centuries, or even millennia. Over that time, many of those bridges have become tied to the cultural identity of the city or nation they were built in. Obviously, function and safety are more important to their purpose in transportation rather than as an artpiece, but form has value too. Think of how many people will cross it, or see it from a distance during the time it is in use. Do you want them to feel it is a necessary eyesore, or should they feel appreciation, awe, respect, etc.?
My high school physics teacher had us do a similar project. We each got the same materials and how to build a bridge spanning 12 in. That was very educational and Unforgettable experience and made the study of Science and physics so much more interesting!
I participated in the Alumni competition at the University of Houston model span contest. These were small balsa wood packages that you could only use what was in the package. Walter, very innovative transmission tower designer caused them to have to rewrite the rules. The new rule was: You can only use glue on the joints. Walter had sliced the wood into fine sheets and glued it back together. He created plywood with no weak ends and the dried glue was stronger than wood. Other things he did to walk away with the win: They could not prevent his best of all. He baked the model in the oven on low heat to dry the wood/glue. Everyone found out that kiln dried wood is much stronger than air dried wood. He sanded the shape to eliminate any excess weight. You have to consider shear in your wood design.
I'm from Seville but have lived in the UK for more than a decade. I thought it looked like el puente del Alamillo, but I never imagined you were going to mention it. It made my day. 😊 Who would want to learn with a professor like you!? ❤
We did this in 7th grade science class, except our building material was newspaper. I absolutely dominated. The trick was rolling the newspaper from corner to corner, as tightly as possible. Some of the other designs were smart, but they rolled the paper into floppy hollow tubes instead of tight rigid sticks, and thus didn't stand a chance. I would have loved the opportunity to extend my model bridge building domination to Harvard, and indeed, around the world, but alas I am a poor.
I’ve never watched anything remotely similar to this but I’m pretty happy it got recommend! Enjoyed watching it and I really love how enthusiastic you are about your craft and students!! You are awesome much respect!!
When I was at the School of Architecture in Leicester, UK in 1970's we had this exact same class challenge albeit without the aesthetic element. The bridges were built of drinking straws, cardboard and balsa wood with some achieving remarkable load carrying capabilities, but then to the students although not the structural engineering tutor, it was not surprising as most of the structures had rigid wire reinforcement buried and hidden within the members! It was only when one of the bridges failed under an impossible load that the reinforcement was revealed. We all learnt many lessons beyond the initial 'build a structure over a span' that taxed our ingenuity and as student Architects how we could improve the structural capability without overt and noticeable structural effort - priceless.
This was one of the most fun things I did in college. We had to span more like 20 feet and you were supposed to be able to walk across. Mine weighed around 40 lbs and we ran out of weight at 1,500 lbs plus nine people with only about 2 or 3 inches of deflection. It could also float (not sure why you would need this) because the filler between the wood board deck and nylon suspension ropes was made of styrofoam panels. When the ropes were pretensioned, the deck bowed up so it was clear ahead of time it needed a little stiffening. It was so satisfying. I think a lot of engineering students haven't built things with a lot of basic materials, so it may not be intuitively obvious how things will behave and what will and won't work.
Two things i took away from this its interesting to see how the forces are applied to the bridge and how failures can happen more due to twisting also that the center point is the weakest on lots of the structures. Which leads me to more questions and thoughts...def love this sort of thing :)
My dad and I created a bridge from toothpicks for a school project with similar rules but a little smaller scale (about 18 inches long) when I was younger in 5th grade. We went with a glue lamenant design. We made a mold for the columns and trusses and on build day in class the strategy was to cut the tips off the toothpicks coat it in elmers glue then put it in the mold layer by layer interlocking the toothpicks in over lapping layers. We made two of these structures then made the deck just laying glue covered toothpicks across the two trusses with a special 'I' like beam in the middle between truses holding them together under the deck. At 160 lbs we ran out of weight and our bridge was the only survivor. My group won 1st on aesthetics, 1st on weight held (by over 100 lbs 😂), 2nd in cost efficiency, and first over all. We took it home to test it to failure with more weight and it made it to 230 lbs! Great memories with that.
Really fun class. I would have liked to see a standardized way of applying weights -- the bridge that did the best had weights hanging from the bottom, which stabilized the structure. Most of the bridges actually failed because the center of gravity of the bridge was raised high above the base, meaning any small misalignment in weight caused the bridge to flip.
"I am Vietnamese, and I wish my country offered such education. Thank you very much; I will continue to follow and learn a lot from you! I hope you produce many more videos like this!"
I'm surprised at the low standard of design of these bridges considering the level of the students. I've done this in secondary schools with 16 year old and they have come up with some impressive designs. I am particularly surprised at the cable designs that were obviously in compression. What on earth were the students thinking!
They copied an existing design that was anchored and weighted differently. Every design in use, has a certain way of working, and if you don't utilize the design as it was intended, it may fail due to the difference.
Those cables are typically under tension, but they didn’t account for the movement of the anchor points (towers) which in real life often have cables on the other side of the tower holding it up.
Yep more focused on form over function. They think the cable-stayed bridges are aesthetically pleasing but not thinking of how the bridge actually works.
The majority of the load on a bridge is due to self weight, it can be as high as 85% and more of the total load for cable-supported long-span bridges like those mimicked here. Therefore a more realistic loading would be for the majority of the load to be distributed over the full length of the bridge and a smaller concentrated load or better a distributed load applied over a portion of the bridge. With a concentrated load alone the beam still has a lot of work to do in flexure and the cables don't help as much.
Thanks Gregor and you're absolutely right on bridges of course. I know we titled it "model bridges" but it was essentially a beam contest and, most importantly, one where the students learned about beam/spanning behavior. They also knew all of them would be loaded until collapse and that could be done at our discretion/fun! Thanks again.
4 decades ago i was student in engineering. Beautiful to see the young generation in times of 3D virtuality, coding, CAD, fluid dynamics and A.I. doing some handcraftsmanship in construction. The physical experience engraves much derper in the learning process than just sitting front computer screens where smart 3rd party software is going the anslysis of steess loads. Tks for sharing
I love contests like this! I mean, they all took the same class, and yet came up with such different ideas (speaks well of their teacher, to. Like they GOT it, didn't just copy something. That first bridge? I've NEVER seen cables under a bridge like that! NOTE: I also noticed that it didn't actually break, just twisted off it's anchors.
Amazing. I remember doing this as an assignment in my design and technology class in year 12, our teacher scored us on the weight our bridges held before failure against the weight of the bridge itself to determine the best build. It was a super fun assignment and this video really brought back my memories. Thank you for sharing this. 👍
my class did this freshman year. But the span was 18 inches. The supplies were 100 straws, and 10 feet of kite string. Challenge was a fork. Option one, how many bricks can you support given the materials. Option 2, how little materials can you use to support 1 brick. My team won option one. We ran out of bricks and started using textbooks on top. 16 bricks plus 3 textbooks and it toppled. The key was prestressing the bridge into an arched form. We also put smaller straws inside larger straws and used a hot paperclip to punch holes through welding them together every half inch or so. But the best part by far was the team that held up a brick across 18 inches with 6 straws and no kite string. They formed 2 triangles that pinched the brick as its weight settled down. Thus its own weight held it in place. Absolutely genius IMHO.
That was really fun to watch, now what would be a lot of fun is to get as many of the students back together at some point like 10 years out of school and into their real world and have a similar competition that would be an excellent follow on video and honestly you should really do that I just think how much fun you guys would have for that weekend Well done, as a contractor, an electrician and someone who used to maintain 20 story building I wish all engineers spent two years in the field doing some work instead of coming out of school with no practical experience, I get that there are trade-offs its risk versus cost or whatever but when guys like me have to fix stuff that people build week sometimes really want to scream at that person who put this piece of equipment in her room and there’s no way to get it out without blowing a hole and getting a crane Well Done 👏👏👏👏
As an architecture student at the University of Cincinnati in 1970, we did virtually the same experiment but with a restriction of max 1/2 sq inch cross section of any element in the structure. Then we were required to walk across the bridge! Mine worked quite well. Point being, this isn't unique to Harvard! It was our final freshman project! What Fun for sure 😃
Looks like a lot of fun! In terms of stability testing the last one cheated a lot with the buckets on the sides and with a lower center of gravity. The moment of rotation is favored by the adition of the buckets. I think this is what allowed it to fail structurally and not on stability. Some of the others might have resisted just as well.
All of the students could have thought of the idea and used buckets, but only one group did - so kudos to their creativity. It's weird that a number of comments and responses imagined the worst case, then magically convinced themselves it was true, and then felt the need to publicly state their thoughts.
@@23lkjdfjsdlfj Speaking of weird, it is weird of you to magically convinced yourself that the people you commented on don't realize that and then felt the need to publicly state this. Of course the students thought of this, if not when loading on their bridge, then at least when they saw the other students do this. But if you're testing a scale model of a bridge, you're trying to simulate the actual thing, so not a high center of gravity for the load as occurs when stacked. The professor could've pointed this out as well, or prohibited the last team from loading with a lower COG. Given the amount of discussion this probably has been talked about, so my guess is that the students agreed this was fine and were just curious about the result. Hence these comments and the wonder of how the other bridges would've fared with a lower COG.
We had a competition in one of my 2nd year engineering classes. Objective was to build lightest bridge possible to carry a certain weight at a certain height and distance from supports. Bridge had to fail within 10% of the required failure load. Lightest bridge won. We used straws, wire and hot glue. We tested the compression and buckling capacity of our straws to determine failure load of individual members. Required application first principal truss static analysis from first year course and calculations were reviewed. Many came incredibly close to the required load. Probably one of the best courses I did as it taught many concepts all at once and it was a real engineering exercise.
I was frightened for their toes! Speaking as someone who managed to drop a weight on their foot and smash a toe! Do you recall which bridges won the popular vote and efficiency prizes?
Yup...we had lots of checks at start and throughout to look after toes! I think it was Bridge #4 that won "best looking" and Bridge #13 (the last one) won the other two awards which was lovely to see!
Interesting! Judging from video alone, I would not have guessed that bridge number four would have been the winner for best looking. As it was beautiful, I thought others would have taken this award.
I enjoyed this video! It reminded me of my own college experience at the Purdue University School of Engineering and Technology at Indianapolis. I was in a double degree program that awarded an Associate of Science in Civil Engineering Technology and a Bachelor of Science in Construction Technology. We took structural design classes in that program, part of which we took two classes at the same time, Strength of Materials and Materials testing. The second class acted as a lab for the first. As a semester project we were given four small pieces of lumber and were told to use them to make a beam we would test, then right a report on the test. It was expected the beams would fail when the load would push the beam past the maximum to bending moment it could handle. My group had the only beam that didn't fail due to bending, but it failed due to shear. Our beam was the only I-beam shape in the competition. One group made a beam that was larger in depth than all the rest, making it two pieces of lumber thick and tall. The other two groups made box beams. In theory, the I beam should have supported the most load before failing. The beam with the large depth supported the most load before failure, but it was pointed out that the depth would have been limited in actual practice. We were not permitted to cut the pieces of lumber, so the I-beam had on extra thick flange. Had we been able to cut that extra piece, we could have used it as stiffeners to help with that shear. That was a fun project and the most fun class I took in college.
I remember this exercise in the first year of high school science in the USA. We only had to span a 12 inch gap. But our bridges were only made from supplied matchsticks wood glue and string. Definitely one of my most enjoyed school memories. One team got caught cheating by hiding steel wire into the design. It still failed before mine which was purely the native ingredients :-) Great fun. I enjoyed reliving the memory watching this video. Thanks for sharing Paul.
Great contest ideas and prizes, Paul. ---For these courses it's far better to require a single, detailed model at the finish. I've seen too many Construction Technology / Structures courses overwhelm students to the point where the 'prize' is merely finishing the course and surviving it. They learn almost nothing as a result.
Reminds me of an architectural class I had in high school. Make a wire frame type of tower, over 2 feet tall, from tooth picks and hot glue, to hold the weight of a bowling ball at the top. Couldn't glue toothpicks side to side either to make walls. All had to be done with triangles. Was fun. Mine worked. Was so proud.
I did this at Ottawa U back in 87 ... the ORIGINAL first class of bridge busting ... got a nice b+ for the final report on the failure ... and had the leftover bridge for 5 years at home too ... (573lbs for a 5 lbs bridge made of Balsa and string)
I remember doing that in college and just not caring about the job, do the work, get a middle grade, graduate and that's it. Now that i'm a mechanical engineer, i really wish i paid attention to this kind of fun projects ! Congrats !
I would love to see more of it and would also be great to understand the different forces on the different area and how they could be improved… I definitely studied the wrong subject back at the University 😂❤
We did something similar at Napier (Engineering, Mechanical and Production) in the 70s. We each got a sheet of balsa wood, a tube of glue and a craft knife and we had to span a small gap. Individual effort rather than teams and they were judged simply on weight bearing. My triangular hollow section came second and the winner used a truss design. That was one of the most useful engineering learning experiences ever (along with the bending of the cut and brazed 10mm square bar). I sometimes wish younger engineers did more with balsa wood and less with Ansys because it taught a certain intuition about material efficiency!
Remember making bridges back in grade 7, we used Popsicle sticks, same glue and had a weight limit. Was a lot of fun and made me think back to it. My bridge failed around 120 lbs which was on the higher end of the class. He rented a hydraulic press that displayed how many lbs were being pushed on the metal rods that were used to apply weight. We did it after a month spent on learning how bridges work.
Your tests looked like a lot of fun, we did similar tests in my college days using a testing machine and balsa wood pieces. Each entrant got a kit with the same pieces of balsa and the same glue and had to build a model out of only those materials to fit a certain testing and loading arrangement. I'm sorry but the bridges at 7:40 and 9:29 should have been immediate fails. The students were recreating something that they had seen done without understanding how it worked and how to make their models work the same way. The towers were not participating in carrying loads, they were just additional mass and complication for no reason. This doesn't help to enhance MIT's reputation. I saw a similar thing done in a Mythbusters episode where they modeled a suspension bridge without understanding how a suspension bridge worked and how the cables needed to be anchored at the ends. I think your loading unfairly penalized some of the designs in that you had the center of gravity of load quite a bit higher than the "roadway" so this tested the torsional stiffness as much as anything.
Thanks, I was looking for someone pointing this out. The Towers can just pivot freely with no anchoring. I wonder why even the Prof. thinks it‘s a sound idea.
I remember having a project like this when I was 10 years old. We had learned simple bridge types and had to build our own bridges following those models, using recycled materials. My team built an arch bridge with thin cardboard and popsicle sticks, which ended up supporting 3 dictionaries surprisingly. Unfortunately we lost the competition to a suspension bridge (which to be fair was more of a beam bridge with high pillars, as most of its strength was in its beam, made out of a large chunk of staircase ramp). Fun times...
This is what content on RU-vid should be like, it's so good you can't help but subscribe because the content is incredible. I really enjoyed this, cheers.
A professor like you sir, would really allow learning to extend to the next level. Teaching like this would really help students understand the concepts and create a fun learning environment. I know theories and all are important but truth be told, it is boring if it can't be seen applied. So, Thank you sir for your methods of teaching.
