[Music]
hello and welcome to technically speaking the podcast where scientists and engineers come together to chat about some common interests share knowledge and satisfy some curiosity.
I'm Laura and in this episode i'm joined by Rwayda to talk about tall buildings but already you're a civil engineer and i'm a scientist who's fairly ignorant about this sort of thing so how are civil engineers able to build something like a skyscraper and be confident that it won't fall down well it started when the steel industry moved into the future and that was around the early 20th century so the material for building such a building was provided also the
science so the main two thing you need for building get all welding you need a good foundation for the building to stand on and you need a good material so the industry revolution with the steel was half on the other half is the knowledge about the soil and how you deal with it so getting a better foundation because they try to base it on bedrock layers that would be stable and don't think in the soil so that's basically like you know digging down through all the softs of
the soil that you mentioned and finding something solid to build on right yes precisely i guess there are places where you can't find the bedrock to build on but people do it anyway well that's interesting because the tallest building standing now is burj khalifa and it's bald on the sand and they really used some sort of foundation called pile foundation which means you dig into the ground into the soil with a pipe it's like a digging in a tube then filling
that with concrete to provide a friction between the soil and the concrete and that friction would hold the weight so it's not only one pile it's a hundred of them and all these piles are reinforced with steel as well so it's kind of like it holds its own weight and some of the load on it and then the main mechanism of transferring the weight of the building similar to the rock so the rock would take the whole load but now the friction between the soil and the pile will take
the load okay so if i'm being really scientific about this and you're talking about friction this might be a really stupid question but does someone calculate how long a pile you need to have to get enough friction yes ah so you need uh you need to calculate how long uh how many what the distance between them because you're you're creating a whole you're kind of like creating your own rock bed layer you don't want to disturb the soil you want to space them out and you want the pile
to be in an appropriate diameter also you want the length because you don't want to dig too deep then hit the water because you have the water saturation happening and if you hit that that's not not a good thing and also you need to treat the soil and lower the water elevation so that won't cause a problem in the soil so it's it's quite a complicated process we need a geotechnical engineer to explain it so we could probably do a whole episode on just talking about the foundations
but that's not really why we're here yeah from what you're saying i guess the foundations are kind of the sizes and scales with the height of the building so a taller building needs deeper foundations is that right i would put it like a stronger foundation because deeper sometimes won't mean stronger if you start digging the rock bed underneath so you want it to be till then and you find this layer that you will use it to anchor your load or do the piles okay and sometimes if you dig
too deep you might go into problems so the stronger your foundation is the taller you can build okay so it's not necessarily about just digging deeper gotcha you mentioned the bush khalifa which is in dubai and that is a flipping tall building yes it is is that all the spalding now yeah there isn't really a definition of what makes a skyscraper right there isn't anything that if it's over this tall then it's a skyscraper the definition of uh how tall the building
is to be the tallest or the skyscraper is changed through history because the change of what we're seeing in the materials so historically it was between 10 and 20 stories now it's between 40 and 50 stories it's just ridiculously changed because we have more technology to build things now yeah that makes sense so historically you're saying sort of 10 or 20 stories that's probably what 100 meters at the mall yes rather than the hundreds of meters that you see in some cities yes burj khalifa
is about 800 something meters high also we should mention something else that just jumped in the top of my head now is the invention of lifts or elevators really helped with tall buildings i guess so i guess if you're really really fit if you didn't have one though well imagine going up like 50 story i i well i barely can do three i spend a lot of time or i did spend a lot of time hill walking anyway so i was proclaiming mountains that were well only a kilometer tall but not just going
straight up constantly like you would on a staircase i suppose it's a bit different that's quite a hike yeah and it took a while so yeah maybe you're right maybe uh the lifts have made a big difference or elevators made a big difference to uh how tall you can go so once you've sunk your piles or you've dug into the bedrock or do you dig into bedrock or do you just sort of pin the things to the bedrock you you dig in too near them and anchor your either pile again or if you don't dig
through them or do a bed foundation which basically you cast a cube of concrete and it would settle on them okay so then once you've done that you can start building up so what does that construction i see on tv things like steel frames and girders and stuff but tell me more about it you start with steel frame that's why i said uh steel industry helped a lot building vertically so you start with the steeler frames which when they started welding with them looked like a cage then you
use concrete so you use steel and concrete usually so the concrete also provides stronger external layer and you put it in the main areas and then you will build up once you secure your foundation you build up yeah is there any particular consideration of like the shape of that steel frame or how many different cross pieces you have to put in i'm guessing you can't just do whatever you want there must be physical principles no no you need to do the calculation as you said but it's not
very restricted but sometimes when you build in a certain way you would avoid certain external impacts so let's say the wind or something so when you build something circular it's react better to the wind yeah because having been on top of those mountains it is pretty windy up there even if it's not windy blow her downs interesting so yeah they've definitely been times where you're like it's a sudden gust you have to sort of well i have to stop and plant my feet and just
wait for it to pass because i'll get blown off the mountain otherwise oh yeah so what do you experience is something that is a problem for the tall buildings this wind would cause them to sway interestingly earthquakes would have a quite a similar effect because it would just excite the base of the building get it to sway and there's like a few methods to protect the building from swaying so you have something called external tubular frame so you would get your
external frame of the building rather than the cage i was talking about be stronger to protect the building the other thing is using number system and also what i was talking about about a circular some sort of building so if you think of burj khalifa it have what they call a leaf foundation and you can even link it to a plane wing it's have this smooth radius that that would flow through and it won't kind of impact it so it would slide by it rather than push
it ah i see so i've seen some buildings that have got chimneys on them but the chimney's got a sort of a corkscrew around it is that to direct the wind around it so i guess in that case the wind will either curve up or down exactly so kind of you deceiving the wind i think it's a strange example here is similar when you jump to the water and have your hands in to break the water first so you don't hit your head with the water tension and everything and get a headache or break your neck so
it's kind of the same idea when you break the wind as a medium with the this like kind of wingy leafy shape of their edges i'm gonna have to go look up some pictures now because a leafy wingy building sounds quite interesting well if you if you if you just google burj khalifa and how they build it the tab like three leaves that the wind would break on the edges and it is not a problem anymore cool i will definitely do that you mentioned other methods um you mentioned tubular
frames and dampness and you also mentioned earthquakes so do they use the same design principles in buildings and earthquake zones yes there they they do both earthquake and wind would cause the building to escalate and one of the system is called the the tune mass system if you think of a bendolium you will have the bondolium on the top of the building so once the building is way one way the ball will go on the other side and get you to balance one of the example is the tabe 101 building in
taiwan and it has that system of a ball that balances the building on the top and it's open as a touristic site you just go can go in the building and see it that's interesting so it kind of just it wobbles around yes it levels around similar to the idea of tuning your guitar or if you're thinking of a marble ball in a pocket it would sway also if you think of the i'm not sure what they call it when the people skate over these wavy bits uh with the skate with the thing slide through
and they have the same movement so you're saying like this keyboard thing so you're saying if they skate over sort of an undulating surface but part of the they sort of move to react to that yes so like say their head doesn't move but their feet move up and down yes i get it it's the same idea so their balance but they using this k to do the cool movement and jump around holes this is a similar idea because they keep their self balanced and it's the same with the
building because they get the bendolium movement to create an encounter effect of the swaying we can look up some videos later to share on twitter and instagram i think but you're reminding me all this talk of earthquakes and wind and things that make those things fall down or destroy buildings in some ways making me think of a different type of disaster we like talking about movies a lot in this podcast and using those to explain the science and he reminded me of stay puft
marshmallow man from the original ghostbusters film because he was obviously climbing up the side of that building i think he stamped on the church at the bottom of that building it was in new york right yes i think it was filmed in new york yeah i think they had to climb up the stairs you were talking about having the elevators climb the stairs like it was a 22nd floor the building itself the bottom part of it does exist in new york so i walk past it but apparently it doesn't have 22 floors
the top part of the building was made up for the film ah so that was a ghost bit of the building yeah central yeah because the building top that's spooky though if you think of it it was like it was a ghost movie and the building gets the ghost is it's very very meta at some point but in the film they also said the building was made out of some really weird materials that i don't think you'd find in a building but you can tell me if i'm wrong so it was made of a magnesium
tungsten alloy and cold riveted girders with cores of pure selenium well the technical words are there but i don't think any of the materials are real we have girders in building and you we have balls no can you cold rivet something or is that just a made-up phrase the rivet is similar to a ball so they would rivet something in or secure it in i guess so you can vivid jeans can't you just kind of fold a bit of the metal around so it then gets wider than the hole it was put
through but i mean it's a film right so all of that stuff could be made up the whole thing was designed a superconductive antenna to spiritual turbulence i think oh doesn't sound like civil engineering yeah that's not my area so turbulence is more with aerospace engineering you've mentioned already uh steel and they used as much additional building material not spook central stuff why do we use steel and concrete so steel is is really very strong in tension and also
in compression but we mainly use it in tension because it's quite expensive and concrete is really really good in compression so and it's mainly when when we build we would think of rainforest concrete which basically have a little bit of steel in it to reinforce it so these two construction materials are giving you the enough strength for you to build high because you achieve their foundation either by the bedrock or the piles and you need a strong material for
the body and that's why we mainly use them even though they they do harm the environment and i think there's lots of statistics says the construction industry contributes something about 11 percent of the carbon emissions as well is a lot and it's mainly concrete and steel so we're talking about materials that have been around since like the industrial revolution i think you mentioned at the start so they're quite old technology and i kind of feel like it's no surprise that they produce a lot
of co2 because that seems to be very industrial revolution kind of thing i was saying is it just very unfortunate that we need to use such materials i mean there'll be a lot of infrastructure required in the very near future to change how we do things it's not like tall buildings you know building more wind turbines and things like that or building more houses that are better insulated so we'll have a lower carbon footprint to produce fewer co2 emissions i mean is that something that the
construction or the civil engineering industry is trying to address as well yeah so we're trying to go back to using timber and building timber been modified a lot and now we have what we call this the engineered timber product there's a lot of different ones i'll give two example that recently used in the tallest timber building which is in norway which is it's used as bart hotel park apartment now called the wood hotel it's altered so cold war architect homogeneous i may have pronounced it
wrong so i apologize to all the norwegian people for corrupting the name of the building this whole thing is built using two of the very common now timber products which call the clt which is stand for cross laminated timber as that when you get the lumber of the timber cut it usually to boards then you glue them perpendicularly to each other so one layer would be one way and the other layer will go across it and you'll do like three or four layers which make
it to be strong because you have tension compression tension compression changing as in layers so that's the clt and the other one is you get the boards of the timber glue them on the top of each other and that's the glue lamp okay they both have advantages and disadvantages and they they're much stronger than the normal timber in terms of some actions and they use them now to build the tall timber building which is a an industry that is starting the tallest timber building now i think is
85 meters high the one in norway okay there's a couple in canada as well uh so probably it would have been considered a skyscraper at some point but i guess it depends what else is around it right if you consider that a skyscraper could just be something that is really prominent on the skyline if everything else around it is quite short they can still claim they are the tallest timber building yeah and it is really environmental friendly the one in norway because they use the forest nearby to
get the material and prepare the materials and also like the advantage of timber when like one of the layers that of that ember get corrupted you just replace that layer if it was across a laminated timber you just get the broken boards glue something new and prepared sounds like a very diy type project yeah it seemed to be very sustainable that's what they're saying i live in quite a damp place i live really close to the sea in west columbia so with that sort of construction
material the treated timber would i be able to use that or would it just get really damp and rot they're treating timber for moisture so they would cover the timber with certain chemicals that would get it not too rot yeah that is something is growing as well so i think even with the uk humid weather timber building would survive also there is something called it's a hybrid between steel and timber so they're doing a mix of the tube instead of steel and concrete so yeah tempura is
getting a lot of attention at the moment i mean concrete i see that it's just well i think we said in previous episode rocks that have been burned yeah it just lots of burning yeah and steel's kind of like rocks have been purified and put together in some way because it's different metal laws right but now like they're doing lots of recycling of the steel yeah i'd heard that there isn't yet enough steel in circulation to be able to keep on doing that indefinitely because
we'll be building more infrastructure well that's true but i i don't know much about this i won't comment me neither that's the limit of my knowledge on that topic you mentioned elevators or lifts earlier on and some of the hotels i've been in were so told that going up in the lift my ears popped which is a bit disconcerting but tall buildings do that to you i suppose yeah but i also imagine that there could be thousands of people in a building that big we're talking
what 20 30 i don't know even 40 stories big yes so you could have uh well i say 500 000 i don't know that's probably a ridiculous number it's 500 000 people in the building not big i do a bit of safety related stuff and i always think oh that's an awful lot of people to evacuate in some sort of disaster like fire yes so that sort of thing has to be considered two things to think about there the evacuation will divide the building to compartment and these compartments need to have stairs going
down they mostly do internal stairs because the main thing with the fire and tall building the fire travel on the external edge of the building and that's why there's a huge regulation all about the cladding material you use to cover these folding fire trouble on the exterior size even if it started somewhere interior because it's easier to travel there than the inside so the you divide the building to compartment and i think that's mainly why the elevator changes place and you
only get a high to a certain floor then you change it all right i've never thought about that that makes sense and i just thought it was just some sort of design quirk that meant the elevator couldn't go all the way to the top because you designed the building a certain way that the elevator won't go to the top or you attach something to it but not necessarily in all of the toll welding okay so it's not just okay so we built it this tall now we wanted to build it taller but we
didn't necessarily think that through yes fair enough and and when you start attaching buildings to its neighbors it's also become problem because you don't have the strength in the internal wall to have the same kind of services and providing lifts and elevators there so i recently been in a hotel that it was basically they joined two building and they have opening in between and they link them with stairs but the left can go up to a certain point and i think because the material of the other
building was mostly all bricks i think they could not fit the left and i was thinking that i don't have anything to uh prove it and and i think that's mostly why lots of the buildings in the uk don't have lifts in them or elevators ah maybe because it needs a lot of strength to anchor it brick was a very traditional construction material yes at one point yeah i think that's applied to most of the uk that most of the uk don't have much left senate i was very disappointed when i moved like there's
no lips you'll just have to improve that cardio and make use of those stairs what's with you with pushing me to use stuff you want me to drive a manual and use my and now you're taking the lift away from me my secret is that i don't actually like technology for myself science i'm sitting on a podcast called sexually speaking i really i think we we quite diverted the topic as we usually do we talked a bit at the start about skyscrapers and how they became more of a thing where around the
time the industrial revolution when steel and various other materials became i guess easier to make yeah and i think they they needed some sort of a building that would be more densely populated because the cities were growing bigger and they were trying to save the space so that they went vertical if you've run out of space in two dimensions go for a third exactly it's very popular in in the us and in japan mostly though though in japan they run out of the space so
they need to go up i mean japan's mostly mountains although there's a lot of space you might not be able to build something on it all that easily because it's quite steep but sometimes you want to work in that city because there is something happening there there's some industry or companies or investment happening in that city and that's why the city needs to expand yeah and then you have to think about your earthquakes again if you've got that really tall building we're back to talking about
disasters and how to keep people safe how do you make that building not fall down and crush people sorry it's taking away a turn we mentioned a few of the method that we used today but that were not historically available and that's why some building did collapse in the history yes i guess all the buildings wouldn't have had those and the earthquake dampeners that you mentioned the thing that oscillates on top yeah and also the external frame is not in the very first one so if you have the
tubular frame which is basically externally stronger than the internal one it was all the same strength if we talk about skyscrapers i guess to me i mean there are a few in the uk and we used to live in manchester and there are a few really tall buildings that stand by really obviously as you're traveling in on the train but for me i think some of the most iconic tall buildings are probably in the u.s united states because you see them a lot in films hollywood effect yeah i guess it
was like that golden age of film maybe was around about the time people were starting to build these taller buildings as well yeah i'm thinking stuff like godzilla and king kong yeah these are very old aren't they they are sort of 1950s 1930s but they stick in your mind when someone's talking about it's usually a creature trying to climb up the slide or something or ghostbusters yeah we definitely don't design building for a congo attack though but if you did how would you go about
doing that if you have a giant ape is there anything you could do i think it's using the external frame and also with the same technology they have now with burj khalifa because there's something else that they have there a concrete column in the middle of the steel frame which is the external that kind of anchor everything in and maybe put some uh wires on the building that protection wires what they call the spiky ones oh you like to stop creature from actually
grabbing onto the building to begin with like those spiky things they have on some buildings to stop pigeons from some people have a dusty glass as well it's quite it's just the glass one freaks me out no i suspect king kong wouldn't have a problem with that i reckon he's got pretty leathery hands and the glass wouldn't bother him or her maybe yeah but i think anchoring their welding really good in the middle with kind of like even if you want to sway it one side you have the strength to
not to sway and also i think trying to build with a flexible material that is kind of have a little bit of merchant to sway so even if it's weighed it does not it's not stiff so it won't break yeah but yeah we definitely don't know don't design for like a see i guess what's what's interesting about that from a historical point of view so king kong was sort of 1933 the film and the empire state building was the tallest building at the time but it's only 381 meters i say i say
only i still quite tall but there are much taller buildings now right you were talking about the bush khalifa building at the start yes it was a it's about 800 meters it's kind of double the empire state yeah yeah yeah in some places a mountain is defined as anything over 600 meters so it's taller than mountain but they managed to climb it in mission impossible tom cruise got in the top was that the start of ghost protocol yes climbing up something made of glass
with these sucker things and then did one of them stop working yeah yeah i'm not sure if that was intentional or it was really stopped working i assume it was a plot point maybe to make you go right at the start of the film oh my god you might fall that's what i thought anyway well they want to get this suspend to it right exactly it would be a nice lead and set you up for the rest of the film i guess not but i can really remember the rest of the film you know yeah i don't
remember the rest of the film but yeah i really remember that scene i think they made it stand out and that's they kind of like the wow has the wow factor with the whole the tallest building and the climbing and everything yeah and so you were talking about maybe people will build taller ones yeah so i've been i've been reading that people are trying to get about a mile high which is double the height of the burj khalifa now because it's about half a mile i think with the technology we have
now i think it's doable the other thing people are thinking about is the conditions of the workers because you need lots of intensive work and you need to be very protective of the skilled worker you used as well to build these building because i know there were lots of issues with building uh burj khalifa and there's lots of protests associated to it i feel like there's something about you know trying to build a tall building where you probably shouldn't because you mentioned
you had to figure out a way to do something about the fact it's on sand it's kind of like it started as a need and now it's a race the race for the tallest building to kind of show off yeah but i think they're not only iconic it does hold a lot of people and it does provide lots of good services if you build them correctly you say build correctly i guess that means they should last for a long time as well yes they need to be sustainable because you don't want to build something that would
collapse on people's heads i feel like we keep talking about these buildings that shouldn't be falling down and we keep talking about trying to destroy them like maybe we should uh not care you you agree okay right i guess i'll sing so i i think i've learned quite a lot from lueda about how to build a tall building and the foundations are the most important thing to think about i guess you have to consider the location as well what is classed as a tall building has changed a
lot over time comparing the empire state building to the burj khalifa and you also need to think about the changing effects of the winds as you get higher up and the materials that you use sound like they're very important especially if you want to build something that is sustainable and will last and has a low carbon footprint from the outset so will be good for climate change i'm about to throw a question here at the end as well so if the climate is changing with the
changes we we would need to make to buildings oh you mean if it gets really hot or really cold in the future yes and that would even change the wind part and with the building we build now is safe for the future oh that is a very good question maybe we can explore that in a future episode what you think what sounds an intriguing idea it does but we can uh end this episode here and maybe think about how we do a really speculative one about don't you know what to say to that if
you want to carry on this pessimistic conversation you can find us on twitter you can leave a comment on this episode and we are now on instagram and we will put our instagram details in the description for this episode so thanks for sticking with us we'll see you next time the views expressed in this podcast belong entirely to the person that said them they do not represent any industry or organization if you enjoyed listening to these views it would really help us
out if you could rate us leave a review and tell a friend this podcast was sponsored by no one but if you're interested in funding us to continue to have frank discussions about science and engineering please get in touch [Music]