How Sensors Keep Bridges From Collapsing (and other structures too)

Infrastructure Instrumentation to save lives and make cool graphs!
It turns out that plenty of types of infrastructure, especially those that have serious implications for public safety, are equipped with instruments to track their performance over time and even save lives by providing an early warning if something is going wrong. Engineers keep an eye on strain, vibrations, temperature, pressure, tilt, flow rate, and more to make sure that structures behave like they were designed and to keep people safe from disaster.
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Practical Engineering is a KZbin channel about infrastructure and the human-made world around us. It is hosted, written, and produced by Grady Hillhouse. We have new videos posted regularly, so please subscribe for updates. If you enjoyed the video, hit that ‘like’ button, give us a comment, or watch another of our videos!
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This is not engineering advice. Everything here is for informational and entertainment purposes only. Contact an engineer licensed to practice in your area if you need professional advice or services. All non-licensed clips used for fair use commentary, criticism, and educational purposes.
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This video is sponsored by Henson.
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Tonic and Energy by Elexive is licensed under a Creative Commons Attribution License
Source: • Elexive - Tonic and En...
Hosted/Written/Produced by Grady Hillhouse
Edited by Wesley Crump
Script Edited by Ralph Crewe
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[@PracticalEngineeringChannel]

🏗 Did you know I wrote a book? There are still some signed copies left at store.practical.engineering 🪒 Look forward to your morning routine with a Henson razor (Code: PRACTICALENGINEERING for a free pack of 100 blades): bit.ly/3CWiWJP

[@Taylor_Moon]

may God bless you

[@anteshell]

I want to see an in-depth videos about these instruments. Especially this claim at 14:20 piqued my interest. Vibration causes relatively immense stress on the material, so how is it possible for something to be able to withstand decades of vibration with "no issues or drift"?

[@Platypus_Warrior]

I subscribed for this kind of video. I am not as much interested in what could be. What will be with over 30% chance of happening is still interesting.

[@silentracer911]

How are you going to promote a game and not get money for it? I came to click your link and found Henderson Razors… get them to sponsor a video or 2

[@XXCoder]

I recommand trying hellgineers too lol. Such fun, and blue skulls is so hard times.

[@EBuff75]

In Calvin & Hobbes, Calvin asked his dad about bridge weight limit signs. His dad's explanation was that they build the bridge and then drive heavier and heavier trucks over it until it collapses. Then they rebuild it and put up the appropriate sign!

[@pitcheung5354]

1/2right, it should really test by drive heavy lorries on the bridge - but not collapses and rebuild need.😆

[@jepito29]

I always think about that comic when I see a bridge sign to this day

[@jefferyyoung6836]

Having been a heavy transport truck driver I respect bridge load signs. I would hate for the bridge to be damaged by my load and my insurance rates go up because of a million dollar mistake.

[@rayopeongo]

Calvin’s dad had the best explanations. I loved his colour/ black and white photo/video one.

[@Mordecrox]

​@@pitcheung5354 a bridge was finished close to where I work so I could see almost 200 cement mixer trucks ordered to stress test it. The final test I was told involved filling them with rocks and water. Didn't knew they could even empty themselves from being filled with gravel and was expecting just water

[@matthewcocke8274]

I work at Geokon! I have been a fan of this channel since before I began my engineering degree, and I never would have guessed I would see the devices I work on every day to pop up on this channel! Thanks so much for trusting our equipment!

[@_aullik]

This is marketing done right. It cost your company nearly nothing and there are a lot of engineering students watching this that will remember that product in the future.

[@professorofdeath7965]

It's marketing but more subtlety done

[@StuffAndMore]

i also work in the field and i.m glad this video exist so i can send it to people who ask me what i do now :)

[@Muny]

These sensors are really neat! I am curious though; of course engineers "could" use these sensors, but how widely used are they really? Are they expensive to install? Is the maintenance of the acquisition equipment expensive? How likely is it that the bridge over the river down the street from me has something similar?

[@L3001USPSA]

Hello, I work at Geo-Instruments.

[@Campfire_Bandit]

As a US state bridge engineer, I love these videos! I share these around the office all the time, it's incredible how useful these simple breakdowns of common engineering principles are.

[@ElSantoLuchador]

I'm a bridge inspector, and that's why I'm here too. I'm not an engineer, but I play one on TV. (WSDOT)

[@ClayinSWVA]

Fiber optics in concrete hooked up to a data recorder is the new hotness. There are several companies in this space right now.

[@leocurious9919]

@@ClayinSWVA They are just qualitative sensors (crack / no crack)? And at the same team cheaper because of it, I assume?

[@ClayinSWVA]

@@leocurious9919 they can do strain, shape and load. Built-in traffic counting is a thing they can do also. The fiber is fairly cheap and can stretch the entire bridge for monitoring.

[@leocurious9919]

@@ClayinSWVA Amazing. Thanks.

[@evan-edstrom]

I live in Seattle. A few years ago, there was concern about the integrity of the West Seattle Bridge. They shut it down and did an extensive overhaul. Prior to re-opening, they tested it. The engineers put numerous sensors on the bridge, and drove 12 loaded 80,000lb trucks onto the bridge and measured the bridge's response using the sensors.

[@ElSantoLuchador]

Yup. The bridge developed cracks over time that weren't helped by the Nisqually Earthquake and a jammed rubber bearing that prohibited thermal expansion. They sealed the cracks and retightened the main span. Actual testing was preceded by lots of computer simulations. Trucks have grown bigger over time so the calculations made at the time of construction no longer hold (WSDOT bridge inspector, not an engineer, but I play one on TV).

[@busterbeagle2167]

sorry about your luck. lol

[@casonator]

Where my West Seattle Islanders at!!!!

[@touching_grass]

​@@casonator West Seattle is not an island, as a Vashon Island resident lol

[@francesbernard2445]

Good thing our body can maintain itself om its own while we are getting enough water, food and sleep instead of having to pass routine tests once a year using only sensors to collect the data eh?.

[@paulhaynes8045]

Much as I like civil engineering, I never thought anyone could make strain gauges interesting! Yet another excellent episode. Thanks.

[@paulhaynes8045]

Still not forking out $70 for a razor though!!

[@randomname4726]

​@@paulhaynes8045 It makes sense over a fairly short time.

[@mattbennion779]

​@Paul Haynes if you shave everyday it makes sense. Right now I am not employed and don't bother shaving but when I go back to work I plan to buy one of these.

[@GilmerJohn]

Strain gauges are difficult to maintain "in the field." An annual literal survey every year or so would track deflections. Actual physical inspections of the steel would prevent most surprises. Maintaining bridges (inspection, cleaning, and painting) will keep most bridges in service indefinitey.

[@ElSantoLuchador]

I lived in an old building with strain gauges all over the place to monitor crack growth (the building dated from the 1900s). It wasn't as interesting as it was unnerving.

[@ChristianAkacro]

Wow Grady! I'm a longtime subscriber and viewer of your content. I also happen to be the Producer of Poly Bridge 1 & 2. So glad to see you 'break down' and give the game a try!

[@tomorowsnobodys]

Nice! Great games!

[@butter-biscuit2248]

I LOVE BRIDGES!! I’M DEFINITELY GOING TO PLAY!!!

[@chrisoconnor6579]

I am a mining engineer specializing in rock mechanics. Instrumentation is important but much more challenging in a deep underground mine as the material is dis-continuous, heterogeneous, anisotropic, non-linear, and subject to plastic deformation. Point sensors can provide mis-leading information as they become highly dependant on local conditions, most of which cannot be accurately defined. We also use Geokon for most of our instrumentation. Our best tool is often the micro seismic system from dozens or even hundreds of sensors collectively working together to collect and compile rock noise data due to fracturing. Despite being a “remote” sensing approach, there is a lot of detailed local understanding of performance and conditions that can be extracted.

[@thegatek33p3r3]

If there's any video game you should play, it's Infra. It's all about infrastructure.

[@BlueScreenCorp]

Hmmm... You are right there is no plot of government corruption, fraud, or murder in it either

[@musicmanwins12]

Adding that to my steam wishlist! That game does look fun! Thanks!

[@genesises]

*its a puzzle adventure game - not an engineering game by the looks of it. unless you are talking about Infraspace - which is about infrastructure.

[@DrDrumminKY]

i really enjoy your videos. My wife is a civil engineer that deals mainly with storm water mgmt and stream restoration. After watching your videos, i can actually have conversations with her about her work and understand (albeit at a rudimentary level) what shes saying. Thanks so much for these and please keep them coming! I've got a lot more learning to do.

[@rayoflight62]

In the sector of telecommunications, we use an instrument called TDR (time domain reflectometer) which sends an electric pulse in a wire and check the returns from that pulse, to measure at what distance from the test equipment the fault is located. This test equipment is similar in principle to the sensor you showed in the video, but the frequency is higher and the domain is different (time instead of frequency) but the methodologies are similar. This is a very nice video - I begun my formal studies - a lifetime ago - specialising in "Transducers"; the devices have now been revolutionised because of the MEM technology, but the principles and the designs stayed the same. Thank you for the great video, Greetings, Anthony

[@ziginox]

TDR is fun, and can even be done at home if you happen to have a function/waveform generator and an oscilloscope! I was able to find out the length of some weird coax that way. Also, OTDR for fiber at work all the time, but that's in another department's hands.

[@Dr_le_Quack]

Its something that I am very grateful for in the field of electronics is that we can very easily monitor the performance of out systems (well, most of the time). I think its something that us electronic engineers often take for granted in comparison to the other fields of engineering.

[@AlecMuller]

Edward E Simmons, co-inventor of the bonded-wire strain gauge, spent many of his later years wandering around Caltech in a tutu, and would often attend physics lectures. This was was considered strange (even for California) in late 90's when I saw him.

[@michaeldufresne9428]

"Quick recreational math" gave me a chuckle

[@Halfwayparticular]

I used to work at Geokon as an electrical engineer. It was a wonderful place to work with exceptional leadership. Seeing the scope trace of the excitation and subsequent ringing brings back a lot of memories. Really glad you featured their stuff.

[@pitcheung5354]

I worked in a watermains flowmeter project: we install lots of flowmeter and pressure logger at the watermains, to monitoring the initial pressure and Flowrate of each watermains, and send those data to server for inspection everyday. While some watermain have non-stop flow data even at mid-night(which normally nobody use water) we realize that there is some leakage after that flowmeter, thus we could carryout a faster inspection/repair/exchange activity of those leakage pipe.(We don't need to checkthe water supply zone entirely) Sensors is really good

[@SomeGuysGarage]

Nobody uses water after midnight? What are we, gremlins? People go to the washroom in the middle of the night or work shift work or backflushing water softeners or put a load of laundry or dishes on, or a million other things that use water at night.

[@stepheneyles2198]

@@SomeGuysGarage Water Utilities can compare customer's meter reading with their own network flowmeters and extrapolate usage patterns over days/weeks/months etc. Any unusual fluctuations (i.e. increases over normal usage patterns) can be flagged for investigation. It's a common leakage detection technique where I work as well!

[@Berkeloid0]

@@SomeGuysGarage You're forgetting about commercial customers. Not many office buildings put a load of laundry on at midnight. A flushing toilet also doesn't show up as a non-stop flow like the OP said, it just uses a bit of water and then stops again. Leak detection is normally triggered by continuous flows that run 24/7. Most non-industrial places don't use water at the same steady rate 24/7, which you would see if you had a leaking pipe. Normally you'd expect certain times of the day (e.g. around midnight) to have some periods of zero water use where the meter doesn't increment at all for a few minutes or hours.

[@mfaizsyahmi]

There is always flow from the plant. If they're not directly reaching customers they're recharging the storage tanks. The concrete way to detect leakage is to compare measured mains flow vs metered flow. They'll never tally, and the difference is the non-revenue water i.e. leakage.

[@Sabi1234567890Asdf]

While seniors are great I've seen my share of them fail. Some in more spectacular ways than others. In my opinion sensors are a great resource to use but can't be the only tool. Prime example. We had a moisture sensor on a dryer that failed during my practicum in university. The dryer wouldn't shut off on the auto dry cycle. The homeowner caught it. The tech I was working with was so sure it was a stuck contact in the timer so he just brought out a timer. The homeowner called back that day and complained. It was the sensor. Thank God the home owner noticed it or there could have been a fire. I've learned never trust sensors. They are a great tool to help but are never definitive. It's sad to see these days that alot of tech company's are relying more and more on sensors and cutting other things that are time tested.

[@ThatsPety]

I don't know man, something about this video is just so magical. Your demeanor, the experiments, graphs, games, information, everything about it just comes together so beautifully. It's like the perfect culmination of everything you've been doing and improving on with your channel. Practical engineering at its finest, and I mean that in more ways than one

[@rpm6085]

Gotta love the humour in his scripts.

[@J-Bibble]

Great video. I was the engineer of record for a number of state owned dams. We routinely used piezometers, inclinometers, crack meters and other instruments to measure performance of earth dams and their concrete components. I used to enjoy observing trends in the data that correspond to things like changes in reservoir elevation. You start to learn how the infrastructure performs under different conditions, allowing you to spot potential issues.

[@SvdSinner]

Strain gauges are both useful and tedious. As an engineering student, I was horrified that many cool tests ended up taking 3-4 times as much time to calibrate the strain guages and the Wheatstone bridges attached to them than it took to do the experiments themselves.

[@TravisMapes1]

I feel your pain, but the calibration is worth the extra effort to make sure it's done right. If the data can't be trusted at a quantifiable level, then the experiment is meaningless 🤷‍♂️

[@joeyager8479]

Not exactly the same thing, but this happened when I was working for a large elevator company as a young draftsman about 50 years ago. The R&D Group was tasked with redesigning the escalator frame to try to reduce the number of welds to make the fabrication less expensive as the current fabrication required "weld all around". The goal was to produce a frame with a minimum of welds as determined by the engineer's calculations. The new frame would be set up a series of strain gauges and loaded up to test the structural integrity and add welds as required. This was all preCAD so I spent about a three weeks learning and adding weld symbols to the weldment detail drawings and having the engineers check it and make some changes as required. It turns out that the contracted fabricator's welders weren't certified so not understanding the weld symbols, they just welded all around, just to be safe! Needless to say it pretty much doomed the project and a series of lawsuits followed. I wound up leaving the company about a month later for what turned out to be a very interesting 36.5 years at a local machine design and fabrication company.

[@Bird_Dog00]

0:50 small correction: The bridge builder can try again. it's only those who USE the bridge who don't get a second try...

[@jdowls9538]

small correction to your small correction. *sometimes* they can try again. Most of the time, they lose their jobs or even their licenses! :P

[@rayoflight62]

The engineering sector lives and thrives on the use of sensors. There are some incredible type of sensors (e.g., a silicon diode used as temperature sensor - instead of an NTC or a termocouple, or an hot wire used as airflow meter - instead of a turbine connected to a micro-alternator). A comprehensive video of most types of sensors used in the world around us - from an automobile to an electric power plant to traffic lights), I believe, would be greatly popular here on KZbin. Best Wishes, Anthony

[@phoenixbloomfield8946]

I worked for a summer installing monitoring equipment for a wetland restoration company. We put finely perforated PVC pipes in the ground 1-2M deep. Next we put two small pressure sensors into the pipe: one was dangled at the very bottom, and the other was above the ground on the top to gather atmospheric pressure data. They took a reading once an hour for a year and then the data was downloaded. By knowing the density of water and the atmospheric pressure above that water we could generate a very nice plot of how the water table was fluctuating at that well. By installing 6 wells or so in strategic points at each site we could get a pretty good map of where the water was going underground through that wetland area, how much water was being absorbed into the ground, and (when correlated with weather data) how upstream conditions affect the wetland water table and how long the wetland held water (slowing it down from all rushing downstream at once) after a rain storm.

[@banjopete]

That’s a wetland, shock absorber on flow.

[@Karagoth444]

As a watcher since your automated garden/plant watering, I too have long valued cool graphs.

[@Dysiode]

The city water pressure demonstration really blew my mind! I intuitively know materials will deform, but never would have guessed there'd be a ~10% drift in water pressure over a day. The fact the strain gauges use acoustic vibration also blew my mind! Really fascinating video!

[@seanfuller2152]

I spent the first 19 years of working life making Vibrating Wire strain gauges, load cells and Piezometers. Plus other geotechnical Equipment, in the UK this video brings back memories of calibration working out the K Factors, etc, with a calculator. great times tensioning the wires and hearing the tension change with adjustment.

[@deonmurphy6383]

Your video reminded me of sensors I was peripherally involved with. They were flow transducers retrofitted into the penstock/scroll case of a hydro unit. They helped monitor the unit’s performance, but caused their own problems. The water pressure forced water through the fittings, through the cables, and then out of the scroll case, to the collection cabinet. So another problem to deal with. Not insurmountable, but unexpected.

[@deonc81ify]

As an Instrument Maintenance Technician, I share your love for sensors. 😅

[@Astyl_]

Strain gauges are an invaluable tool in the maritime industry as they are used to monitor hull stresses which is especially important given the size of modern ships and all the dynamic forces acting on them, they are employed all throughout the ship, used to measure shaft deflection, torque on wheels and fans in generators and engines, mooring forces, deck hogging or sagging due to added cargo load and basically anything you could think of. Most commonly the electro-resistive type is employed.

[@FlorianLinscheid]

Another important sensor type is an acoustic emission sensor. When placed on a structure, they can listen for cracks and friction sounds and let you locate the damage position, if you don't even know where to look for them. They are usually temporarily mounted, but can also be installed over many years. Their use in infrastructure is comparatively new though and not fully accepted and widespread.

[@CatsT.M]

1:35 About the bridge shown here: that is the Tacoma Narrows Bridge, luckily when it collapsed no one died but inside the car shown in this video there was a dog that several people attempted to save but were unable to. The driver, Leonard Coatsworth, was bringing the dog back to his daughter, after the collapse he said "I believe that right at this minute what appalls me most is that within a few hours I must tell my daughter that her dog is dead, when I might have saved him." (even though I have read and heard this quote several times it still feels terrible)

[@bigjay875]

I must admit I am one of those that enjoy watching engineering experts play these type of games. Helps me learn new tricks for repairing damaged things in the real world

[@DeleteriousEffect]

The plumber doesn't care about the city water pressure fluctuations. They care whether your pressure regulator valve is doing its job, so those higher system pressures and fluctuations don't gradually destroy everything in your home plumbing system. You've surely noticed that your faucet doesn't behave like a fire hydrant. They just need to test while they're there to determine whether the regulator needs adjusting or replacement.

[@TheWinningSperm888]

As an Instrumentation and Monitoring Engineer, this video makes me very happy! So good to see some of the sensors I use day to day!

[@tutrmw]

Working on a maintenance project right now for full depth concrete roadway repair. The contractor uses maturity meters that monitor the short term temperature of the concrete to know instatly when it meets the spec to open the lanes back up to traffic. It's incredibly useful and makes everything work much quicker and more smoothly. Sensors are great!

[@paulkinzer7661]

I enjoyed so much in this video, which really was 'practical'! But the graph you created showing the change in water pressure in your home was quite surprising. I mean, I knew there must be some change during periods of differing usage, but the change was quite a bit larger than I would have thought, IF I had ever thought to think about it. Which I never have. Thanks for challenging my brain to think about new things!

[@matthewwalburn2529]

I use a lot of these sensors for my work! I work for a fracture mechanics research lab where we often get representative pieces of piplines and other infrastructure that were made decades ago (without good data kept on it and often old impure steel) and test how it cracks to see if the rest of the line is still safe to run for awhile. Often times you can detect cracks with a pipeline inspection tool (called a PIG), but quite often smaller cracks things are missed and even then they often don’t know what material the pipe is after a few decades. So research is always being done to asses the likelihood of a leak. There’s also tons of effort being put into studying how converting our gas lines to hydrogen would work (hydrogen “embrittles” steel) in an effort to switch our infrastructure to cleaner energy. Crack growth is super facinating and suprisingly very complex to predict. But it also can be measured directly by measuring the resistance change across a crack as it grows (from the steel left getting thinner and thinner) it’s quite hard to interpret this data, but one of the more useful “sensors” we use because you can watch a crack grow with a very high accuracy without having to break open the material Sometimes it’s so geometry dependent that a small scale sample changes the results too much. So sometimes we do full scale tests (like purposely putting a flaw in a pipe and then cycling pressure) because small scale samples just don’t tell the whole story. Often this is compared to finite element analysis models to try and improve those tools. And the data from these large scale tests can be quite complex to analyze with so many channels and sensors. We did a pretty complicated test last year with easily over 100 channels (strain gauges, string pots track 3D position, linear displacement transducers, resistance measurements, thermocouples, etc.) and the test took a few months to set up. If you haven’t done one already, an episode on failure analysis would probably be a fun topic, although I’ll admit a very broad and complex one

[@MichaelSteeves]

I'm an I&C engineer. It is fascinating for me to see the instrumentation used in Civil engineering applications. I deal with pressures, flows, levels, humidity, temperature but I've never actually had to deal with strain gauges. Cool!

[@Bbfishman]

as a structural ironworker in NYC, i appreciate the accuracy of your videos. its cool to see these concepts demonstrated in a simple way

[@SpeakerMunkey]

As a mechanical engineer who used to work in acoustics, it makes me very happy to discover strain guags work by plucking and measuring the resonant frequency.

[@Itslvle]

One interesting medical application of structural load sensors was hip replacements. We initially thought you needed to avoid walking and standing for a few weeks while exercising in bed before you could walk again as not to destroy your new artificial hip joint (or rather it's connection to your bones), but after a study with a hip replacement with stress load sensors we found out that simply flexing your hip while in bed put more load on the joint than actually walking. So we ditched the weeks of lying in bed and people now go straight to walking after hip replacement surgery. Not only is it not fun lying in bed for a few weeks for no reason, it actually costs much more than a hotel room staying at a hospital and most importantly, hip replacements are done on elderly people that can lose 20-30% of their muscle mass just by lying in bed for a few weeks which can result in them never walking again afterwards or at least ending up in several weeks of physiotherapy before they can get out of the hospital again. It really did revolutionize hip replacement treatment.

[@Locke99GS]

Your plumber that took a single measurement at a tap was likely checking for extremes, like is the pressure under 40 or above 100, things that can indicate problems with only a single measurement.

[@1DGB16]

Hi Grady. I'm a long term subscriber to your channel and enjoy your videos a lot. What caught my eye to click on this video wasn't the title or youtube suggestion for once, but actually the thumbnail picture. That bridge is in the middle of my home town of Echuca, Victoria Australia. Only a mile away from where I grew up a hundred yards from where I work to this day. You don't show it or reference it in your video, and in the description only mention stock imagery providers, but I just thought I'd take a moment to point out the 144 year old bridge from a little town in rural Australia is the one you chose to be on the thumbnail for your video. Keep up the great work, my family loves your uploads mate. G'day from Australia.

[@nax1807]

I work for HensonRazor, and i must say, its been a delight having one of our products featured on this channel, we used to have a joke in the shop where we used to go round saying which youtube channel we wished we started, most said things like H3 or Mr beast, but there was one guy who said leisics or practical engineering, so this definately came as a surprise when marketing managed to make this sponsorship happen. much love grady.

[@PaulThurlow]

40 years in this game . I love this video and all the others . All colleges should be subscribed to this channel. Its true about VW strain gauges - many years ago we had some issues with strain gauges and we got an old-style phone to one and our expert could tell right away what the problem was. VW strain gauges were used to get the right tension load on the sixth street bridge in LA recently - 388 of them tuned to different load values. Keep up the great work.

[@L3001USPSA]

Hi Paul.

[@ronkirk5099]

I'm a retired mechanical engineer and I sure hope these videos are encouraging the next generation of students to choose this interesting and rewarding career path.

[@Whytho2000]

This video makes me happy, because Im in charge of putting a bunch of sensors in place, and I always forget that this is providing data for really cool things that engineers can build.

[@AppliedCryogenics]

My inalienable right to measure things and graph data! I love it.

[@christhemarketingguy]

This video is so amazing. It offers great insight into a hidden world of engineering and safety. Very inspiring content. Thank you!!

[@DubYahJohn]

Hi, just a general comment to say how much I enjoy your videos, as a retired, former mechanical engineer mainly in the Petro-chem industry I also got involved in bridges and structures in later years. But I guess us engineers are all the same breed and whatever it is, we just love looking for problems to solve. Thanks for the videos. At 66 I'm still learning.

[@malcolmcluett5732]

The old iron bridge (in the thumbnail for this video) is the railway bridge between Echuca (Victoria) and Moama (New South Wales), Australia. It was built in 1878 for rail and road traffic and spans the Murray River which is the state border. It is now just used for road traffic. The replacement concrete rail-only bridge (opened 1989) can be seen alongside.

[@InssiAjaton]

My first dealing with strain gages was when I assisted glueing them to some developmental aluminum poles. They were intended for flag poles and for street light poles. Some early prototypes exhibited scary response to wind, namely starting to vibrate. So there was an effort to study the different means of reducing or eliminating resonances. Bending strength was the first measurement target and then harmonics of the vibration. Eventually the light poles revealed another issue -- torsional vibrations, when the lamp housing with its ballast was mounted at the tip of a sideways bent top. . Then I designed (and built the electrical parts) for measuring moving wire tension at different stages of a multi step pulling process. The first instruments used a three wheel system with a flat spring steel "beam" ( a leaf ) and a full bridge formed by a set of 4 strain gages. They worked fine at slow wire speeds, but became a bit scary at high speeds. So, the final version had instead of ball bearing rollers three polished and rounded carbide pieces, one at the center and one on the opposite side of the steel leaf, at the ends. Again, he strain gages were forming a full bridge. I still, after decades, have some strain gages in my desk drawer, just in case I would need to build some new instrument.

[@shigekax]

Really interesting video ! I have limited experience with engineering, but the subject of this video is something I actually never thought about ! thank you

[@JeffMTX]

Guess I’ll chime in too- about 25 yrs ago, I used precision pressure transducers to estimate the altitude of the PANYNJ service trucks on the GW bridge between fort Lee and the Bronx. Placed two fixed units, one in fort Lee, and one on the upper deck NY side. It worked beautifully, except we discovered we had to correct for the Bernoulli effect (it was practically an exponential) due to the trucks’ driving speeds! We just linearly interpolated between the two fixed stations :)

[@draco18s]

OMG it plucks the wire and measures the vibration frequency. That's HELLA COOL. I had no idea that that was how that worked and the fact that you can hear it is just icing on the cake.

[@megmolkate]

I knew a guy who worked for MDOT who was involved in a project with the Mackinac Bridge Authority which used strain gauges and heavy test loads to determine if railroad cars could be placed on trucks and driven across the bridge. I recall that this was after one of the loading docks for the railroad car ferry failed. The conclusion was that the bridge could take the load but the project was not undertaken for a variety of reasons that I don’t remember. Railroad service between St Ignace and Mackinaw City was discontinued.

[@kasuha]

People who design and manufacture these sensors are unsung heroes of the modern era. Most don't even know they exist and countless lives were saved thanks to their work.

[@DanCooper404]

Thank you! I machine sensor housings for a living.

[@MikeHoughtelin]

Clean, that is what comes to mind on your podcasts. The examples are simple, your explanations are within my vocabulary. Showing how you set up your tests for testing is fun to watch. I truly enjoy your enthusiasm for your expertise, and you're not afraid to say I don't know when you're not sure about something. Thank you!

[@snowcarver]

This channel continues to produce some of the highest quality content. Thanks Grady for putting in the work to educate and entertain!

[@bloqk16]

I recall in the 1980s when the San Francisco Golden Gate Bridge was opened for pedestrians to celebrate its 50th anniversary. The concentrated weight of people on the bridge was multiple times more than it ever experienced from vehicular traffic. Hence, the curved bridge flattened-out at mid-span; which was documented with photos. The structural engineers said there was no danger of the bridge collapsing from that excessive weight. I was impressed the designers of the bridge had over-engineered its structural strength to handle the weight. As, after all, the bridge structure was experiencing unprecedented weight at 50 years of age.

[@StrangeComments]

What an incredible video. Definitely one of my favorites, great work Brady. Wonderful illustrations and demonstrations. I gotta say my favorite part is when you can literally hear the wire inside the sensor ringing everytime its frequency is checked haha. That was mindblowing.

[@Manzplained]

Grady, I absolutely love that you took the moment to explain how the sensors work!! I was sitting here listening to you and I was thinking, “I wonder how those super sensitive sensors work in principle. How do I look that up?!” And you immediately started explaining it!! Yes man!!!! Thanks!

[@iamdarkyoshi]

Sensors that make sci-fi noises to make measurements? Count me in! Excellent content as always, keep it up!

[@Renard380]

When i was at school there was a day in a place where they test materials. They put a sturdy metal bar in my hands, and just from holding the bar, we could hear the frequency of the sensor on it changing, meaning that big metal part was bending a little just under the stress of its own weight! I was amazed!

[@Beryllahawk]

That really IS like a superpower, seeing into solid objects and measuring things over spans of time that we just couldn't manage any other way. Recently learned about something called a "rust battery" too - it made me think about your corrosion demonstrations and the discussion of just what rust REALLY does to a structure. The idea that iron and air can combine into a very efficient large-capacity battery is just plain amazing, but if they can make it work at municipal scale - how cool would THAT be?? Wanted to give you another thank-you about your GREAT book, by the way! I got to nerd out a little about power grid infrastructure just a week ago, they had to open the big green box at the edge of the street, and while I made sure to ask first and stay well out of the way so I didn't endanger myself or the techs, I DID get a good look at the innards for a few minutes! I brought the book with me so I could kinda compare the illustrations to what I was seeing. VERY cool! (The reason the techs were working was also fairly astonishing: all power lines are buried in my neighborhood, but as it turns out, when you combine soil that's saturated with water after days of rain, and a DIRECT lightning strike right over a buried line, things go just a bit haywire! Power to our house did STRANGE things for a while, heh.)

[@jeremiefaucher-goulet3365]

A best example for this video would have been the Champlain bridge in Montreal. During it's last few years before demolition and replacement it was the most analyzed and watched bridge in the country. Covered in sensors everywhere, constantly getting emergency patches at the last minute. Like those temporary super-beams that would block a whole lane of traffic. Champlain bride is a very good case study when it comes to the practice of remote bridge monitoring with sensors.

[@Standaardnaam]

Great video on engineering as always. A comment from someone who does a lot of data visualization for my job: when you use plots with two y-axes, you need to really help the viewer understand what line goes with what axis. Or better yet, avoid dual axis altogether, and use aligned panels instead. (Plotting the same variable on different units, like the pressure graph with bar and psi is a great use of dual axes though.) It also helps to point out to viewers what the direction of the deformation axis actually means, does negative values mean that the crack is increasing in size?

[@bigpapadrew]

thanks again for making engineering more accessible 😊

[@Shanghaimartin]

Been subbed for over a year. Still no idea if he's called Brady or Grady.

[@JohnADoe-pg1qk]

Quote from the video description: "Practical Engineering is a KZbin channel about infrastructure and the human-made world around us. It is hosted, written, and produced by Grady Hillhouse."

[@Shanghaimartin]

@@JohnADoe-pg1qk Wow, honestly I would have said I was 70% leaning towards Brady too. Hahah

[@ESSBrew]

Liked this video by 7:20, its rare that I watch a "casual" video and they mention so many different questions about variables. Ive never had a conversation with a normal engineer about so many little variables. I like this video.

[@richardnavratil9661]

Love the channel and gotta say, as far as sponsorships and ads go (which I understand are needed), the fact you actually film it as if part of the video makes it feel lot more genuine!

[@jetstream01]

This is awesome. I want a full build series for this.

[@kkkk-wg6je]

That razor at the end looks great. And the way you describe it as a precision tool makes me want one even more.

[@viniciusfriasaleite8016]

I love to learn about the working principles of sensors. Always find it fascinating!

[@adriancentra]

I was wondering the whole first half of the video how these sensors work. Thank you for explaining it!

[@shurikentuna]

I watched every ad on your videos without skipping. That's the best I can do for now. Your videos are always top-notch.

[@JustinDrentlaw]

That transition into the ad was the segue of the century. Thanks for making great vids!

[@kentd4762]

Very informative and interesting video, Grady. Great job as always.

[@paulrisk606]

Brilliant. Thank you. Loved the sensors. Genius.

[@Konusu]

I love watching your videos all the time. You've helped me better my mechanical knowledge, as well as improve my insight about civil engineering. As an instrumentation technician, I thoroughly enjoyed this video. Thank you! 🙂

[@BeckyStern]

I came for the cool graphs... was not disappointed. Fascinating. Thanks Grady! 😀

[@billadams8795]

You git so giddy when you talk about measuring and data. :) Love it.

[@theyruinedyoutubeagain]

This is a genuinely brilliant video, I love it so much

[@fuurinkazan164]

Grady I was so happy to see you posted today. Great video as always!

[@derstrom8]

I worked for Geokon up until just a few years ago as an electronics engineer. Very cool to see this equipment in action being put in the spotlight!

[@DanDunfordRSM]

Thank you for re-investing into your channel, bringing us cool modern tools and gadgets to aid in your visuals. It's doesn't go unappreciated!!

[@clintonroushff7068]

As an "instrument technician" I enjoyed this more than some other projects. I see a trend of not taking the time to measure. When we make a change we need to document the effects. Your videos are always interesting. Keep up the good work!

[@KindarConrath]

I found this really interesting, partially because my last job was for a company that makes similar hardware. YieldPoint. They make Extensometers, Micrometers, Tiltmeters, Sloughmeters, Thermistors and were developing a pressure cell and a vibration sensor. I wrote the software that would collate and analyze the data from all the different equipment. Much of this equipment has a special place in underground structures such as Mines, as it is near critical to keep people safe by tracking the shift of the ground above peoples heads.

[@berthaduniverse]

As always Grady, thanks for all your hard work. BTW, if you paint enough, you actually can see the color and texture change of paint drying...

[@joe-edward]

great video as always, Grady. Thank you for sharing!!

[@drewdorkhead]

Havent watched it all the way, but as always great, fascinating content!

[@mattiasfagerlund]

There are also extensometers for measuring larger long time crack formations or earth movement in tunnels. These can measure millimeters to decimeters and beyond. There are vibration monitors used to make sure that blasting, boring or packing/piling doesn't cause undue vibrations on sensitive structures (old churches, tunnels, bridges) or equipment. In earthquake prone areas, vibration meters are sometimes placed around things like nuclear plants to monitor the vibration situation over time. A network of vibration monitors and careful loading during blasting can help blasters fine tune their models on how blast vibrations propagate through a particular area. There are also extremely sensitive ground movement radars that can monitor a rock face at sub-millimeter resolution from kilometers away - to detect and predict if a mine rock face is moving or even about to collapse.

[@FowlerAskew]

I did my electrical engineering co-op with an automated metering company and while those are mostly city-scale systems there are a lot of parallels, especially to your water pressure test. I read a patent at one point (maybe from Diehl?) for a fire hydrant with an internal antenna and sensors to log city water pressure. The vibrating string measurement also has some similarities to the operation of an ultrasonic water meter. You fire an ultrasonic pulse into the water, then measure how long it takes to travel to the receiver. Then you can calculate the flow rate based on how different the travel time is from the typical speed of sound in water

[@markb.1259]

You make this geeky engineering stuff very interesting!!! Thank You!!! 🙂

[@melom8276]

seeing a real engineer play poly bridge makes me very happy! love your videos

[@scotthix2926]

Worked at GE Power, did a lot of strain gauges on turbine blades. 1 of the difficult aspects of the strain gauges is getting the wires out of the machine to the reading equipment. Design considerations for these were thermal growth, load deflection, modal (frequency) analysis,

[@craighendrich3327]

This video is excellent! As a geotechnical engineer, we use sensors all the time to monitor and help predict the subsurface environment. Great stuff.

[@ShrirajHegde]

Frequency based sensors are very clever and incredible. That amused me a lot since I had no idea

[@johncage5368]

Very interesting episode! Sensors for measuring certain integrity-relevant values of structures is a topic not usually covered anywhere, it seems to me. I'd like to see and learn more of that.

[@SuperJaXXas]

Pretty cool! Engineering firm I used to work at years ago designed and manufactured a wireless slope monitoring device, called the "Slideminder" used in mine safety and engineering. I loved working in that field!

[@MrHamsto24]

Hey, I just started working installing VWPs for CNI! Small world :)