hello and welcome to technically speaking a podcast where scientists and engineers come together to chat about common interests shared knowledge and satisfied some curiosity I'm Antonia and in this episode I'm joined by Laura and Rwayda along with our special guest Alex who founded the embracing diversity diversity diaries podcast to talk about bridges and why we love them so much start with Laura what's your interest in this well i have a bit of a weird fascination with
victorian viaducts because they seem so graceful and strong and they're over 100 years old and some of them are still in use and a really good example i've not had the opportunity to visit it myself but i've seen it in the movies it's the glen finnian viaduct in scotland it was opened in 1901 for the west highland railway and it's in the harry potter movies it's that long curving bridge that the train goes across oh that's a nice one yeah
they're just so interesting to me they're always in green places as well and i quite like greenery so it's the greenness the peacefulness and the grace and the strength of them yeah definitely they look really nice from afar. So Rwayda, you're also a bit obsessed with bridges and you're
structural engineers so why do these viaducts last so long. Yes of course I'm obsessed with bridges I would say a fact that not everybody knows about the viaduct the viaduct you can consider them of like a series of mini bridges so each arch it's its own bridge then another bridge bridge bridge bridge to the end and that one one bit that is contribute to is resilient because it's like designers lots of bridges and the other bit is the material used so the viaducts are mainly
considered as machinery bridges made of bricks and that the material have put in into the building has a high resistance and that's why it's staying for long which would link us to another bridge i love to talk about it's the very first documented bridge and it is in mesopotamia well today iraq where um and it is in south of iraq in the city of telo it's made of clay bricks and it's still there but it's like it's not standing is falling down but has fallen down as a whole
with its full shape and be noticeable how old did you say that bridge was when it was well when was it constructed how long ago third millennium bc i think it was constructed ah this is like a long long time ago. Wow that is old! So Alex your a bridge engineer what do you like about bridges?
i absolutely love bridges there's so many reasons i love them firstly i like what they kind of symbolize it's like communication and connection or even travel and union i love how diverse they can be so there's so many different designs and materials but my favorite type of bridge is one that's really iconic to a certain place so as soon as you see that kind of bridge or a photo of it you know exactly where it is in the world and it really kind of makes that city or place stand out
so one of my favorites is the time bridge because i used to live in newcastle and something i really like about this bridge is the fact that dorothy buchanan helped design it and she was the first female member of the institution of civil engineers when that bridge opened in 1928.
wow i grew up in the north east so yeah i'm very familiar with the titan bridge but i didn't know that a female engineer helped with the construction that's pretty cool yeah i really like that fact great so if we dive in a bit more actually about the structure of bridges ray does mention rather old bridge unfortunately not standing but first documented bridge and alex has mentioned the time bridge which is a bit more modern interestingly it's a bit of a
different construction to the mesopotamian bridge and the bioducks can you explain a bit more about that grader as a structural engineer whenever i look at a bridge my brain convert that bridge to a system on forces and then i'll try to figure out how the forces are converted so for a tiny bridge is called two pin frost bridge uh it's similar to the bridge in sydney harbor in australia and the bridge and hell gate in new york and they're all like the shape of that is called a structural
engineer to bend us it's a what what's a two-pin truce so basically if you look at the structure of it you could see a collection of members that came together as triangles and that is a simple definition of truss so a truss is a collection of numbers that came to form a triangle and the triangle will carry the load and the two pins if we go back to the viaduct and as i said each arch is its own bridge so it's each arch is two pins so pins are the two points that hold the bridge
together so the first pin is one edge and the other pin is on the second edge of the bridge so that is a two-pin bridge and the arch is the shape of the bridge okay so in the case of the tine bridge you've got those like tubes of towers either end are they the pins in that case yes i get it and when you say members just so i feel like a complete idiot now they're like the girders and things that the time bridge is made of the girder is the well on the platform
then you'll have the small cable that would carry the load from that platform to that thrust shaped arch and if you think about the truss shaped arch is how the forces are integrated into that structure so for a truss is only carry the loading compression tension if you think of your pushing your hand together that's a compression member so it will transfer that load by compressing it and if you think about the tension if you think of your hand then try to pull your hand the other way
pull them apart and that is the tension force so you could feel the forces with your hand so that basically how the thrust will transfer forces in between these tiny uh triangular members so when you say the member is it i'm also picturing you know you know when you sit down you have a lap and when you stand up where does the lap go is a member actually a physical thing or is it just where the forces occur so what i would refer as a member is the physical thing that would carry the
load so in the case of where we were pushing our hands together our hands on the member yes you're thinking of your hands as two members and then the connection point is like the pinpoint for the triangle is the point in between your head so you're pushing together and the whole hand will carry the lord from that point up to your arm speaking of the time bridge i remember in 2012 hearing about a lightning bolt had struck the bridge wow i bet the pictures were really nice of
that yes as long as everyone was safe as well yeah nobody got hurt but i wonder the effects it had on the bridge itself yeah i mean it's mostly um metal isn't it so it must have conducted fairly well and i guess the question is what happens when you get to those are they they're masonry pins i'm remembering the bridge correctly i just hope that there were no one on the bridge by the time it was hit by the lighting because like steel transfer electricity and that's what
we will be afraid of if the lighting hit a bridge with someone moving on it because if you're in a car technically speaking you'll have the tires to protect you apparently that's not actually true no it's the fact that the frame that makes the car forms a faraday cage ah so it conducts all the electricity away from me i didn't know that nothing to do with the tires given that all the voltage that's coming through the lightning the voltage will arc across that gap
that the tires form really easily apparently so it's the fact you're in a big steel cage that's what keeps you safe so i wonder if it's an element of that in the time bridge as well i suspect not but i don't know i don't know about faraday cages yeah i can't imagine the time bridge was designed with lightning strikes in mind i don't think so i think it was designed in 19 20 something 1928 it was opened yes yeah we need to do a bit of a cross digging into when faraday
was doing his stuff i guess but that's kind of getting off topic yeah i'm just thinking how much do we plan disasters into our bridge building the main two things on the top of my head when you ask that are the wind load and the earthquake because they both cause dynamic load to your bridge which might cause it to collapse if the frequency of the wind matches the frequency of the bridge that would lead to arizona's case which you don't want to happen so we do design the bridges for some
some sort of dynamic loading to protect it from disaster has everyone here seen the video of the tacoma narrows bridge in washington don't think so please could you explain what what's about it's similar to um rawaida what she was explaining was it in about 1950s 1960s or ages around then yes around then yeah yeah i think the video is in black and white basically the wind frequency matches the bridge frequency and it just keeps oscillating and oscillating until it collapses
we should totally share the link for that video in the bio because it's equally interesting and terrifying at the same time yeah some pretty uh cool physics going on maybe i don't know if they are cool if you're talking about a bridge being destroyed yeah cool and bridges come up a lot in films as well and they always seem to want to try and destroy them we were planning this episode then spider-man the newest film was mentioned
and there was a big battle on tower bridge mysterio was doing something with his drones and there were lots of explosions but i don't remember the bridge actually being destroyed in that one am i remembering that correctly yes i think it was a very resilient bridge isn't it while talking about the tower bridge i would need to say a bit about this engineering it's a bit different to what i was explaining about the two pin if you imagine the middle span of the tower bridge when it's open
we call that a cantilever so each bit can't lever so if you think of each half of the span as a balcony that is the cantilever structure so it would hold the forces on only one side and the whole load will transfer instead of like thinking of the packed viaduct and the two pins so that the whole lord will go to an end and the other half of the lord will go to the other end and that is a cantilever bridge ah so when you say lever i think of something that sort of goes
up and down to let ships go through that's what a lever means to me about this cantilever means it's sort of counterweighted yeah it makes sense in a way so aside from tower bridge not actually being destroyed it's really iconic image of london are there any other iconic bridges that stick out in your mind when you think of a city because i think that was bob alex's interest in bridges well i guess i'll just give him one of hers for me it's probably the golden gate bridge again because it
comes up in so many films and it often seems like it's being destroyed in those films i mean router you mentioned earthquakes in there that's an earthquake zone isn't it on a fault yeah and there are lots of monsters that come out of the scene films that seem to want to attack that bridge well what can you tell me about the golden gate bridge as we kind of explaining the type of bridges so it's a suspension bridge that is a bit different than other bridges
because if you have seen the curved cables that are coming along and there's like tiny cables so the tiny cables will uh carry the load from the dock of the bridge the beam to the suspenders what we call them the huge curved cables and these will transfer the load up to the power which we transfer that to the foundation for the suspension of bridges you'll have a huge span in the middle if you think of the cantilever london tower bridge it's a shorter spa
in the middle so you didn't need the extra support to go longer there you go another type of bridge so what's the engineering in that suspension bridge that allows it to have a bigger span than a tower bridge in london is it the fact it's not a cantilever cantilever if you prefer you can pronounce it both way well if you think of the cantilever bridge and the point at the middle it will like reach to a point will it will deflect more right and it won't be structurally stable
and that's where the suspenders come in so they will pinpoint the small cables all along that huge span and this small cable will carry on the load to the suspender okay and that is uh one aspect to it and the other aspect is the material that the small cables and the splendor are made of you see are you talking to someone that simulates atoms in a past life during a phd so when you say small you
don't mean atoms small i i mean that's actually as like as a structure uh kind of a small not as tiny tiny bit small but if you compare the small like cables to the suspender they're small aren't they you put them in that perspective it's all relative yeah so are they like sort of like this the small cables like sort of as thick as your wrist maybe any idea well i think you have like cycled over that bridge it did but i was really looking at the cables what i was doing i think it would be
like thicker i don't know really but it would be smaller than the suspender which will be huge okay so yeah you mentioned i've been to the us i have traveled quite a bit around america and when i was in new york i heard about a nature bridge there that sounded pretty cool because well manhattan's really built up i mean yeah you've got central park but apart from that it's all just concrete canyons of buildings you mean a concrete jungle no concrete jungle of what dreams are made of i don't
it's honestly it is more like canyons than jungle it honestly is that was a reference to alicia keys he's wrong i know jungles and i your canyons it's definitely more of a canyon is never wrong yeah how can you deny alicia keys i see you saying i'm wrong yeah artistic license on the on description say yeah fair enough it's not a hard science describing a city but i thought the idea of having this nature bridge so repurposing an old bridge that possibly isn't
in use anymore into something new that could be useful was pretty cool and another member of the podcast team was telling me about one warrington as well where they've designed this bridge that's got like plants and things growing on it so it's a bit of a green space amidst a concrete thing concrete plateau or warrington you have a thing with concrete laura yeah because it's interesting but that's a different episode
speaking of sustainability and materials if we think of how ancient civilization use different environmentally friendly construction materials that's the first kind of materials i'm trying to think what they would have started with it would have had to have been rope and ward moving up to masonry rocks i know there are a lot of old masonry bridges in the lake district i don't think i'm going far enough back thinking about those
i'll jump in and say clay brakes was the material that the telo bridge and ancient mesopotamia was made of which is interesting because it's very environmental friendly yeah it's interesting it's a lot of the bridges in the lake district there's a lot of mining around the lakes so a lot of the bridges are made from local materials which i guess is why they're constructed the way that they are lots of slate i remember from my walks i love that in terms of sustainability
using local things that are readily available yeah i guess it only works for certain locations though yeah another member of the podcast was talking about how she would commute over a rope suspension bridge it was only way of getting from wherever she was to wherever she needed to go and i i can't imagine doing that it was a very different country it's very different construction materials yeah i think that's really different to imagine going over a rope bridge which is kind of
something out of a movie every day on your way to school or to work and that was your only way yeah it reminds me of the scene from indiana jones where he's having that battle on the bridge that he deliberately destroys to try and get free of people and they're all sort of hanging off the side of this cliff i can't imagine doing that as a commute not indiana jones style of course but just sort of day to day walking across a bridge that hasn't deliberately been destroyed but again it's
another bridge being destroyed but what do you think also helps them last longer first will be the engineering behind it the other bit would be the material which lead us to something alex knows more about which is the maintenance of bridges yeah so i do a lot of work on bridge maintenance this is where i saw all those lovely bridges in the lake district i went for a week and we did bridge inspections on raw iron bridges masonry bridges reinforced concrete bridges keeping up
that maintenance checking if there are any kind of faults or defects and sorting them out asap haven't inspected a wooden rope bridge yet hopefully i will in the future though i think there are many wooden rope bridges still in existence that is still used i kind of think if i know any famous ones they come from film quite a bit but i don't remember using any in real life there's the via for out there at honest up i've gone across it but it's three cables
so you're literally walking across this chasm with your feet on one cable and your hands either side is the the railing and that's it you've got a safety harness but unless you fall off you don't need that harness and i find that really weird that i walked across a canyon using just three ropes even though they were made out of steel rather than uh natural fibers that's kind of um stomach dropping isn't it i actually stopped to think about it yeah
the most memorable rope swing bridge for me was the one in shrek honestly like still gives me goosebumps now i just remember because i was saying about the symbolism of bridges and that really symbolized in common danger in the castle you just knew what was coming as soon as you saw that bridge did it have music to it as well where like he and donkey were both running around being chased by the dragon yep and then at the end i think yeah the bridge snaps and then they fall
and shreks holding onto donkey like his tail and you're just like oh my god don't fall into the lava i still remember it like it was yesterday yeah in a sort of indiana jones parody yeah i was doing a bit of research into this and according to the historic bridge foundation bridges do seem to signify change in films and society in general they not only represent the expansion of empires but they're also associated with danger and death or evil
and there's nothing like the psychology of the walkway or the road that crosses over empty space that has something in relation to dread and uncertainty so i guess they're used quite well in films to present represent a particular theme they're trying to get across and i wonder if maybe that's why i'm sort of drawn to some of the historic ones because they're in strange out the way places and you can imagine all these sort of historic cloak and dagger things
going on in these kind of quiet hidden glens that sounds like a good place to leave it there we've covered a lot about bridges we've talked about about why we love them why they get destroyed and how to actually keep them standing so i think we'll draw the conversation to a close but maybe let's say science can build a bridge and we'll bridge this gap into alex's podcast which we might be uh having a crossover into so alex can you tell us a little bit about embracing diversity
yes so this is a collaboration we're bridging both of the podcasts together my podcast is called embracing diversity diversity diaries and the aim is to let everybody know how to be an ally for the different diversities because kind of reflecting on diversity women in engineering that's kind of the only real diversity i have within the industry and i don't think there's enough out there to let people know how to become allies and really draw awareness to different diversities we can find
celebrate the differences and just celebrate how unique and diverse our industry is in engineering and i really want to expand this out into construction and stem subjects and just keep it growing and chrome great thanks alex so if you enjoyed this please continue the conversation maybe send us some information about your favorite bridge facts or how verges were made on twitter the views expressed in this podcast belong entirely to the person that
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