Structural Engineer Answers City Questions From Twitter | Tech Support | WIRED

Structural engineer Dr. Nehemiah Mabry answers the internet's burning questions about city building. How are underwater tunnels made? What city has the best urban designer? How do bridges not collapse? How do floating cities work? How do sink holes happen? Nehemiah answers all these questions and much more!
Director: Lisandro Perez-Rey
Director of Photography: Constantine Economides
Editor: Ron Douglas
Expert: Dr. Nehemiah Mabry
Line Producer: Joseph Buscemi
Associate Producer: Brandon White
Production Manager: Eric Martinez
Production Coordinator: Fernando Davila
Casting Producer: Nicole Ford
Camera Operator: Chris Alfonso
Audio: Brett Van Deusen
Production Assistant: Ryan Coppola
Post Production Supervisor: Alexa Deutsch
Post Production Coordinator: Ian Bryant
Supervising Editor: Doug Larsen
Assistant Editor: Ben Harowitz
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[@DrNee]

Thank you for this opportunity WIRED! I appreciate the comments as well 🙏🏾

[@kepter2k704]

Was World Trade Center a controlled demolition

[@joshcervantes2961]

Hi Dr. Nehemiah I just wanted to say your communication and knowledge of structural engineering is awesome. As a structural designer I would have a hard time trying to explain some of the questions. Awesome job.

[@danielp415]

Read a lot of urban planning and nobody ever described it as harmony between living working and playing. You killed it !

[@DrNee]

@@joshcervantes2961 Appreciate you

[@DrNee]

@@danielp415 Thanks for the kudos man

[@edalex23]

Went to school with this guy. Well done Nehemiah

[@WuntaykTimmy1]

Cool!

[@IvanIvanov-qx5oz]

Omg me too

[@GhostNovaa]

me 3

[@dannysmyl677]

Me too! He is awesome!

[@bxdda]

awesome guy

[@A1BASE]

I’m still blown away by cathedrals built in the 1300s. Generational projects that are incredibly technically fantastic. ‘What is your favorite building’ is a staple ice breaker exercise for my group.

[@sarahc6473]

I recommend reading The Pillars of the Earth by Ken Follett. Realistic fiction that displayed how it takes generations to build a cathedral.

[@abiolaolayinka2023]

He's not "just" a structural engineer, his knowledge of each aspect of civil engineering is astounding. Beautiful video.

[@chrisvo203]

who's saying "just"?

[@bobbyjenkins1321]

Maybe you missed the part where he says that he's a civil structural engineer. Civil engineers need to understand Geotechnical, Hydraulic, and Structural Engineering processes while also maintaining a connection to the economic factors involved in large scale construction. Civil Engineering isn't as easy as they make it out to be!

[@chrisvo203]

@@bobbyjenkins1321 i see, thanks for explaining

[@jocu475]

It’s called researching before filming lmao

[@ransforddamptey5151]

He actually has a doctorate in civil engineering. Super humble guy!

[@RishabhDesairf7627]

Should've called it "Structural support".

[@Pablo-cn3xt]

I wanna point out how these videos are such a great way for children to explore careers and not to mention seeing someone who looks like them be an expert in their field. Well done Wired.

[@DrNee]

Indeed!

[@yrtsg]

He looks nothing like me 😢

[@palinanavitskaya6133]

I hadn't ever considered that. You're absolutely right

[@leok7193]

Looks like them? What children do you know with a bald head and a full beard? lol

[@jenm1]

@@leok7193 They obviously mean race

[@ExileOfSand]

This guy was sooo good, loved how well he explained everything, plus his ideas of ideal architecture too. Bring him back!!

[@Cowatude]

Yeah i loved his video on the bridges, definitely one of the best hosts on this show.

[@timt8027]

As a structural engineer im amazed at what this guy knows. Some of the questions i would not consider to be our job like the question about traffic lights. Also some questions that were asked are for a specialized kind of structural engineer but he knew the answeres anyway. Im impressed!

[@juan_lopez1999]

Ikr. This guy is mind blowing 🤯

[@alexmaduta972]

Well maybe because he had time to prepare the answers? You don't really believe he answered them on the spot, do you?

[@monzerfaisal3673]

@@alexmaduta972 He also has a doctorate in the field which makes him highly knowledgeable and differentiated!

[@user-ni8rl6pf4q]

Right, they give the people the questions ahead of time and the answers are prepared ahead of time. Notice how they all have props and exhibits that just happen to go along with the questions. This kind of stuff is more scripted than you probably think.

[@Wildman-zh8lg]

You're not a structural engineer

[@JelenaW]

As a structural engineering university professor, I sometimes think I might gesticulate too much when explaining some things. It was so reassuring to see Dr. Nehemiah do the exact same movements :) We need to "reinforce" those definitions with our hands :)

[@davepowell7168]

Did the WTC buildings have seismic dampers?

[@ennanitsua]

Gesticulation helps me to understand! Keep it up!

[@nathanhaimson]

Hey, expressive teachers are the best! Especially for us visual learners who might have a hard time soaking up info just by listening to words alone.

[@SmokeyChipOatley]

@@nathanhaimson 😎👍, 👁️🧠👨‍🏫👀✌️👌🫡 (Yes I agree. I learn visually too. Good comment soldier.)

[@joshfriedman2717]

I know nothing about engineering and I thought that I don't care about it either... Until I saw this video. SO informative and clear! Thanks Wired. Thanks Nehemiah.

[@stevenc8140]

Josh think about civil engineering where streets, sewer, electric, & water are designed around roads and buildings too make sense! It’s incredible!

[@ClosestToTheSun]

As a CIVE, this is one of the most well done of these expert videos I've seen. I wouldn't be surprised to see this video included in some Intro university courses for engineering

[@zacharymeagor8675]

Would love to see a similar episode with an urban planner. I feel they have another perspective on the political and theoretical aspects of cities.

[@SokunRia]

we do. i often find myself entrenched in social aspects more than anything when it comes to urban planning and design. i just wanna design cool looking cities and squeeze in more parks but i end up working more with people and our social plights.

[@_maxgray]

Dr. Mabry is really good! Knowing the right information and conveying it to laypeople clearly are two different things and he's clearly got both sets of skills. Please bring him back!

[@danielzonneveld7712]

In the Netherlands, almost all, if not all, of the traffic lights have sensors that monitor the flow of traffic at the intersection, as well as in the town/ city to keep the flow of traffic moving. I.e., you can be approaching a green traffic light that turns red, it can turn back to green in seconds if it doesn't detect any other traffic with priority.

[@implecity]

If a light turned red then quickly went back to red here in the US, people would be crashing all the time ☠️ people here don’t know how to drive

[@CrashingKites]

Every time I hear someone talk about the Netherlands it sounds magical.

[@hunchbackaudio]

Every time I hear people bring things up like sensor governed traffic lights for example, I think, isn’t this the standard in every country?

[@NFSHeld]

In Germany, traffic lights may also be deliberately programmed out of phase or particularly in phase for slow speeds, to slow down traffic. I.e. in a 30 zone you can either go fast and have to stop on each red light, or go slow and arrive at the perfect time.

[@IluvinortheIneffable]

In the US they are programmed out of phase to induce violence

[@andrewcarson5850]

They have that in Buenos Aires. It's actually incredible to take a taxi ride and it just never stops until you arrive at your destination, very unlike London where you sit for ages at every traffic light, watching the fare climb higher and higher.

[@samuelturner6076]

I’d love to see more of him, he explained clearly and passionately.

[@StayVCA98]

It's really nice to get some real professional and truly an expert on their field on answering some of these questions!! 🤩

[@DarkStar27182]

Would love to see this done for other engineering disciplines - like electrical, mechanical, aerospace etc

[@8happyperson]

He worked at the university I went to and talked to my freshman class a few times. If I'm not mistaken he judged a competition we had and I was the third place winner. I got my engineering degree but am not using it. Glad someone as smart and nice as Nehemiah is though.

[@Tunechi65]

Go use that degree!!

[@STEMedia]

😊 Check us out btw 😉

[@MasterGhostf]

what a waste you don't use it. I am saddened by that fact.

[@petersage5157]

A lot of math also goes into designing a bridge for wind and variable load conditions. Two examples where the engineers fell down were the wibbly wobbly London Millennium Footbridge and the 1940 Tacoma Narrows Bridge, and we still have bridges where soldiers are advised to "break step" when crossing them to avoid resonances.

[@CLSGL]

I love seeing smart, genuine professionals talk about what they love. It’s a bonus when they can actually talk about it in a way that educates you!!

[@jopo7996]

Dr. Mabry is giving us a great foundation of information to build on.

[@Slimerson93]

Check u out 😎

[@maninarush2112]

😐🙂😁😆😂🤣😭🤢🤮

[@TonyTylerDraws]

I see what you did there

[@MrChipoclas]

Bro I just saw your comment on the rocket science video, you are demolishing this comment sections with your good jokes.

[@Righthand_]

One of the most straight forward person who appears in tech support. Someone who I willingly talk with all day long.

[@lisabrown8772]

Traffic signalization can also address issues of speeding (so you'll hit more red lights if you drive higher than the speed limit) or are prioritizing other modes of transport, such as pedestrians, bike lane users, and buses (and so vehicle drivers will experience more red lights).

[@saint-cetacean]

Exactly. San Francisco has a number of "green wave" streets that are timed to 15, 20, or 25 mph, as well as one that is timed to 10-12 for bicycles. If you hit it just right and nobody's being a jabroney, you can get across town super efficiently.

[@EstellammaSS]

That’s hilarious because in my city you hit every two red light if you drive at the speed limit but goes through pretty much every one green at 100kph.

[@dylanrieck6671]

Always impressive when very experts on a topic can concisely explain complex concepts without either confusing or condescending their audience. Nice job and thank you

[@tpammt8276]

This was awesome! I’ve always been intrigued by the engineering feats we’ve been able to accomplish. Glad to have at least a surface level understanding now.

[@angelaguado5780]

He came into my lecture for one of my classes and he was amazing and had all of us engaged.

[@nnn248nnn]

My brother is an engineer, and I'm in the creative world but still have my love of the sciences. Watched this video to get more into his current line of study-- so interesting and well-explained! :)

[@maryriha]

Just the right amount of explanation for everyone to understand. This is good. I hope he makes more videos.

[@thesoupin8or673]

I see this guy on Engineering Catastrophes all the time as one of the experts that comments on stuff that happened! Good for him, this was good

[@DannyAdair]

Really enjoyed this brilliant man’s accessible explanations. Bring him back for round two!

[@Maddolis]

I loved Dr.Mabry's video ('Every Bridge for Every Situation') for WIRED a couple of years ago, that and PolyBridge reignited an old interest in civil engineering - nice to see him back!

[@phuzed37]

Loved the video, and Dr. Mabry was a great choice; super competent and great at explaining the thought, detail and effort that goes into public safety when building and planning. Great video, thanks for your time, man.

[@Amiittk]

Civil engineering in itself is a pretty vast subject with each having a specialization, so this makes it more impressive that this man can answer questions related to diff discipline

[@vladeckk21]

That was a lot of topics! Thanks for the fun explanations.

[@nawdrawg8436]

Dr. Mabry’s awesome - great explanations to all these questions presented with enthusiasm and yet not talking over our heads. Very nicely done!

[@markbenn1907]

Great display of how well versed civil engineers are in so so many important topics

[@siggyvdz8213]

About the question on rainfall drain in California (10:45), as an agronomist I may also had one HUGE factor: soil. Soil, natural one, absorb a lot of water thank to all the porosity in it, roots, micro and macro organism tunnel in it etc. But nowadays, with intensive agriculture, tilling, machine passage and loss of soil fertility, agricultural soil absorbe less and less water (that why irrigation is more and more needed, making roots superficials, and so less soil porosity, that can became a vicious circle if not well managed). In addition, natural soil like forest, plain, meadows become scare and artificial soil more vaste. City drown themself by being to big and bad built (i.e: no green space, no porous soil...).

[@sharinberman7002]

This guys enthusiasm is infectious! And I love his little Brio Train bridge, perfect touch.

[@sarahferguson0]

I love this series and watch whenever it comes up in my feed, even the topics i don't think I'm interested in because i always learn something cool! 🙂

[@metalgod542]

How is it that this channel always manages to find individuals like this? Like I'm not even interested in half the subjects, yet these are always fascinating.

[@heauxkage5611]

love this guy's energy! thanks for the educational information brought out in a positive way

[@249pinkrose]

As a stormwater engineer we do design ponding to happen on purpose. For very large storm events we are restricted to how much water is allowed to enter the sewer system and at what rate. To meet these allowances we restrict flows and design for surface ponding. Not sure what the design requirements are in California but sometimes the puddles you see during big rain events are actually designed to be there.

[@VxV631]

Coherent, easy to follow, well-spoken, specific, professional.

[@scottwooledge6387]

Worth noting many of the existing subways in NYC replaced elevated lines. Elevated lines were unsightly, noisy, made local housing undesirable and the areas beneath them were dark and often attracted seedy characters. They ran on coal so they spewed pollution. Subways are far superior, particularly for places as dense as NYC.

[@tylergodefroy8713]

its nice to listen to experts who enjoy sharing their knowledge

[@aldousd666]

Presentation is the best yet I've seen at explaining tough concepts in a way that people unfamiliar can understand. I'm not into civil engineering, but I am a bit of a math and science geek, so I'm not just talking my book! Thanks Dr Mabry, nice one!

[@olivia-nu6dy]

Wow my structural questions can finally live at peace with these well explained answers

[@TonyTylerDraws]

These are my favorite videos. Knowledge sharing is my love language.

[@edincanada]

I didn't have a favorite structural engineer and now I do

[@juan_lopez1999]

Isn't he something?

[@utopia4056]

I love seeing my people doing great things. He worked hard and got where he wanted to, and thats commendable

[@gregj6648]

16 minutes well spent learning a lot! Wow, this guy is incredibly knowledgeable and enthusiastic about engineering around the world. Awesome guest, thanks Wired, more content like this please.

[@GreenT_LoR]

I love this man. Every description is so easily digestible and sophisticated. Also, killer smile.💚

[@juan_lopez1999]

Fruity

[@lightningbot85]

That NYC subway questions is a little funny because NYC HAD elevated subways before we had underground ones, but people didn't like them because they were loud, often used polluting steam engines, and darkened streets. We even called them the EL just like Chicago's famous system. Even today the NYC subway system is 40% above ground, mostly in the outer boroughs. (Brooklyn, Queens, Bronx, Staten Island, the area around Manhattan Island) Even in Manhattan, some lines go above ground. The Metro north mainline rail and the 1 line. These are both in upper manhattan (the harlem neighborhood) and are above ground because the terrain get's a bit strange and variable so it was easier to build above ground.

[@scottwooledge6387]

Yes. And I also think some of the above ground trains, particularly in outer boroughs are vestiges of the old EL system. Many of the subways follow the same footprints.

[@bontentengu]

Ah, wish I paid more attention so I could submit a question! Hope he comes back for more. I want to know how engineers would redesign an existing city, including the demolition and construction processes!

[@JujuOfAllTrades]

Get this guy a KZbin channel. Well spoken and easy to understand

[@lifeofeli99]

civil engineering is the most underrated profession

[@JJarosze9595]

This guy rocks, what a great educator

[@boldnbrash7028]

Very smart guy. Can tell how much he knows by how simplified the explanation is

[@N.I.R.A.T.I.A.S.]

This guy's fantastic. Knowledgeable, articulate, passionate. Thoroughly enjoyable video.

[@jon-christiansaulnerond545]

As a civil engineering student, I'm grateful for this video! Thank you so much Dr. Nehemiah Mabry and WIRED!!!

[@STEMedia]

No doubt! 😊 Check us out 😉

[@MrFunnpun]

I'm a civil engineer. Dr. Mabry did a great job representing all our disciplines.

[@ruin700]

4:00 He has that look I'm so excited talking about bridges but I am trying to hold it back some. Man loves what he does!

[@thePatheticfool]

This was such a refresher. I remember working on the idea of future cities in my schools ASCE chapter

[@Foley34]

I always love how engineers can take any question pretty much and give you a logical explanation.

[@michaelweyenberg6238]

It's an engineers job to find a solution to any probelm they're given.

[@DedikateSSB]

loved this one! he seems like he's genuinely passionate about this topic

[@kevinmills1318]

Childhood curiousity was satisifed with the rope bridge question - that one puzzled me

[@N1njaSnake]

One of the best guests of the series! Knowledgeable on so many specialist subjects and yet able to explain them so well.

[@trisooma6348]

Amsterdam (the whole of The Netherlands actually) has an amazing traffic design system too. Which also include loops in the roads to detect different types of traffic and can prioritize / switch traffic lights based on the actual current traffic. Not just an interesting grid but amazing NON car dependent traffic system 🙂

[@mixtermuxter8602]

need more of this guy

[@anthonyvallejo9127]

im about to graduate in civil. and when hes talking about some of the topics, it brings back a lot of the stress i had trying to pass these classes for the past 4 years lol

[@torbenstegmuller329]

This was so interesting and he was so passionate about the topic! Loved this episode.

[@ExtraVictory]

The dampers can be really cool if you do get a chance to see them. Highly recommend

[@cherrybombxo9894]

This guy is insanely smart omg

[@juan_lopez1999]

Ikr😍

[@tengraceapples]

I love how you guys include POC in your episodes. Thank you

[@ans2810]

This guy has a great presentation presence. Very entertaining to watch!

[@DjDobleU809]

RIP Baltimore Bridge 🌉

[@DrNee]

💯🙏

[@andrewjgrimm]

7:05 Got more poignant.

[@readjordan2257]

he should come back

[@paulandstepht]

This was my favorite support video so far. Well done!

[@joshuaspann2277]

Dr. Mabry representing NC State’s College of Engineering really well! Great job Nehemiah

[@truthbetold1258]

best part of these videos is appreciating how attractive it is when someone is talking about something they are passionate about

[@stevenc8140]

Mechanical & Civil Engineering are so interesting. I wish I was proficient enough in my math skills to have gotten a degree in it.

[@grzegorzswist]

About demolitions: You can use demolition charges only when many criteria are met. Other times you use demolition equipment - usually heavy excavators with long booms and hydraulic hammers/ sears.

[@WhyDidIJustEatThat]

12:35 btw update for anyone that cares, The Line is dead. The plan's been scaled back to 1.5km (and it's doubtful that even that will be built)

[@MrSpasticdancer]

structural engineers are unsung heroes of the modern world.

[@cael8948]

ayo i was not expecting to see my former solids teacher on wired. fair play dr. neh

[@DrNee]

@Cael 👊🏾

[@TheAncientColossus]

This is awesome. Great leader for our future engineers.

[@Robin787]

When you get recommended a video on YT and you notice WHOA I went to undergrad with him. Hey Nehemiah!

[@DrNee]

Hey Ruthie! :)

[@UCZx48kBoTg9O]

Should have called it Support Support

[@terryl7874]

Explanations were excellent!!!

[@heretictom]

That was one of the best support episodes yet!!!

[@mrahzzz]

@10:48 - this makes me think of why my city (and surely most if not all), have "hard surface coverage" as part of zoning requirements if you buy land to build on. If too much of your property is covered with an impenetrable surface or too much overhand, you interfere with the way drainage efficiently works in the entire area!

[@annabellecupcake8863]

Great video! I love engineering 😄

[@STEMedia]

😊 Check us out btw 😉

[@sleeperyjeemtoybox]

Got to say these random ones are often more interesting than yet another cleb.

[@JoseCruz-indaWorld]

Great video Dr. Nee !! I loved it !!. Where did you get your cool bridges?? I would love to get my hands on them to show my nephew. Thank you !

[@archaeologistify]

6:00 just to make some things clear, steel is stronger than concrete in both tension and compression. Concrete can confidently resist only compression. Despite it being able to withstand some tensile strength, we don't design structures that primarily take advantage of it's tensile resistance.

[@8523wsxc]

I think it would have been appropriate to clarify that The Line is the dumbest and least feasible project ever.

[@krs-fltutorials4487]

Crazy how he knows about everything. Isn't he specialized in a sub field of structural engineering?

[@s8terkid515]

Structural engineering is actually already a specialization of civil, the rabbit hole goes deep

[@r.sakarollsafe1285]

@@s8terkid515 yep.. it covers the whole thing structurally. ie: roads, bridge, buildings... its pretty hard to get his PhD status I can guarantee that. the common structural eng is building structural eng. I guess that's what this guy is referring to

[@krs-fltutorials4487]

@@s8terkid515 yes, i am a struc. Engineer myself. But he is answering questions about everything. I don't know anything about demolition or underwatwe tunnels.

[@Samantha2209]

@@krs-fltutorials4487 I suppose by researching the question a bit. He would already have the basic understanding of most topics, and would just research to complete the answers… then just communicate it.

[@paulhenry4059]

These things are written out and have a script.

[@senvr11]

I like how the chicago solution is to reverse the flow of a river as opposed to not polluting the earth

[@StanleyBDesir]

I've met Nehemiah in person at one of his SteMedia events. Brilliant and just an all around great guy.

[@STEMedia]

👊🏾