- 2 months ago
Peek inside a cloud-inspired library in Canada that's built over a live railway; see how clever engineering helped a huge Seattle skyscraper go up without harming its iconic neighbor, then cross an Australian bridge that floats above a busy river.
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00:00How do you design a library so impressive it reinvigorates a forgotten neighborhood?
00:06We had to build this ceiling structure with two crews at once.
00:10And then there's this moment where they had to meet in the middle.
00:13We weren't sure was it going to actually meet.
00:16How do you build a 1,500-foot bridge that supports itself almost entirely from above?
00:22There were many sleepless nights.
00:24This tensegrity bridge, it had never been attempted anywhere in the world.
00:28And how do you build a colossal skyscraper in record time with an engineering technique never used like this before?
00:37Everyone came with this mentality.
00:40We don't know how we could get it done, but we'll figure it out.
00:43Welcome to a world where anything is possible.
00:49The space where innovation and creativity collide.
00:54This isn't just impressive, it's revolutionary.
00:58Where the only limit is human imagination.
01:02This wasn't just ambitious, it was audacious.
01:06No one had ever attempted anything like it.
01:11Unpacking the miracles and mysteries of construction.
01:16Sometimes buildings can change the world.
01:18And this is one of them.
01:24To ask, how did they build that?
01:28You know that phrase, so many books, so little time?
01:34Well, when an inspiring new library was proposed for Calgary, Canada, it was more a case of so many books and a totally unsuitable site for a building big enough to keep them all in.
01:45Of course, if there's one thing great architects love, it's an impossible project.
01:50And the building they produced is seriously worth shouting about, even inside a library.
01:55Shh.
01:55Oh, sorry.
01:56Shh.
01:57Shh.
01:57Sorry.
01:58Sorry.
01:59At the turn of the 21st century, Calgary, Alberta is one of Canada's fastest-growing cities, thanks to its thriving energy and financial sectors.
02:14But Calgary's East Village neighborhood has been struggling to keep up since the 1940s.
02:20It hadn't really been taken care of.
02:25There was a lot of buildings that were in disrepair.
02:30Things only got worse in the 1980s with the introduction of the new light rail train.
02:37When the light rail transit line went in, it was literally a physical barrier.
02:42It cut off access between the west of the city and the East Village.
02:46The city decides it needs to reinvigorate this part of town.
02:52And in 2007, plans are drawn up to redevelop it.
02:57Our challenge was to change perceptions of the district.
03:02At the heart of it will be a brand-new library built on a plot of land with the train tracks running right through it.
03:09The new central library project became an opportunity to reconnect these two parts of the city.
03:17They settled on a design from a local company, Dialog, and global firm, Snohetta, a company with a reputation for complicated buildings.
03:28So the difficult site doesn't daunt them.
03:31In fact, it inspires them.
03:33We realized that the library could be formed around the curve of the train line so that the library could lift itself up over the train line and then create this prowl, like a boat, towards the center of the city and connect the east side and the west side of the town where it had previously been cut off.
03:55I think that at the start, we knew that we were on to something that had the potential to be great.
04:05The architect's goal is for the building to be much more than a simple library.
04:12Sitting on top of the tracks, it will bridge the two parts of the city.
04:16First, they will have to find a way to safely enclose the 600-volt electric cable that powers the trains and figure out how to keep the train noise from disturbing the readers.
04:34Next, they need to find a way to support the elevated building and the 180 tons of books that will be inside.
04:41To join the two sides of the tracks, there will be a passageway under the library.
04:51Its complex curving design will mean bending thousands of pieces of wood, each to the exact right shape.
05:01But they will need to do all of this without disrupting the train service running through the site.
05:05If they can pull it off, they will have successfully reunited Calgary's downtown with the East Village.
05:17So this is a project that actually was going to be a challenge from day one all the way actually to the end of the project.
05:25The team arrives on site in spring 2014.
05:31Their first problem, working out how to build over one of the busiest rail lines in North America, which carries 90 million passengers a year.
05:40When we started looking at the plans and visiting the site, the reality set in as to how close the active railway corridor was to the geometry of the building.
05:51It will require both a feat of engineering and steady nerves as the team works to carefully enclose the active train tracks in a concrete box almost 500 feet long.
06:07We're doing all this work, which is very complicated anyway.
06:10And in the middle of it all, you have a train passing and the passengers are waving at you and it's like, what is happening?
06:17Now they need to install the roof.
06:21It was directly over top, you know, just a few inches above the contact wire that has thousands of volts.
06:30If you even get close, there's a chance of getting electrified. You don't even have to touch it.
06:37Turning the power off costs 100,000 U.S. dollars a day.
06:42So the transit company will only allow one 48-hour shutdown.
06:47The only way they stood a chance of getting the roof in quickly enough was to make it off-site.
06:55Huge concrete panels were prefabricated, then lifted into place like a giant puzzle.
07:03At midnight on August 22nd, 2015, the power is turned off.
07:08And in the 24 hours, it was go, go, go.
07:15All these pieces had to fit perfectly and had to be erected seamlessly.
07:19All 60 of them and each one being unique.
07:22It's a race against the clock.
07:24There was a lot of anxiety, a lot of anxiety with that.
07:32Finally, with eight hours to spare, the last panel slides into place.
07:38Once that roof was placed, there was a huge moment, sigh of relief.
07:48With the light rail enclosed in September 2015, the team can start work on the library itself.
07:55But finding a structural system to hold it up is a massive challenge.
08:01Engineers love columns, plenty of vertical supports that direct forces down into the foundations.
08:09The trouble here was the architects wanted a grand open entrance without a single column in sight.
08:18The books alone will weigh an incredible 180 tons.
08:22How do we take all of these enormous lords and try and spare them all the way down the building?
08:31So the solution for that was to design very large structural steel trusses.
08:39The huge trusses were built from interlocking triangles, which are nature's strongest shape.
08:45They don't just hold the weight, they distribute it perfectly, making them nearly unbreakable.
08:5380 enormous steel beams, the largest 170 feet long and weighing 30 tons,
09:00the same as a humpback well, are welded together to form the five enormous trusses.
09:07There's weeks of welding, weeks and weeks of welding.
09:10Then, as the trusses are being put together, they discover a massive problem.
09:16There was a couple members where the steel after the fabrication had a series of hairline cracks.
09:26Even the tiniest fall in those massive steel trusses could cause the whole building to collapse.
09:32They had to be rock solid.
09:34No one really knew what was causing those cracks.
09:41The team realizes the issue is in how the steel is being made.
09:45Steel isn't perfect.
09:48Every single piece has tiny flaws.
09:51If it cools too fast, these flaws turn into stress points.
09:56And stress points turn into cracks.
10:01Those can lead to big trouble.
10:05To overcome it, they start again, this time with a slower cooling process.
10:12It solved the challenge. We didn't see it happen again.
10:14And by November 2016, the fifth and final truss is in place.
10:22The team can move on to the next challenge.
10:25Making sure the noise caused by vibrations from the passing trains doesn't disrupt the library.
10:33Instead of the concrete being rigidly connected to the pile foundation,
10:37you basically break that connection and it's a series of layers of rubber pads and steel
10:44that help dissipate that rumble from the tracks.
10:51Over the next six months, they build the main structure
10:56before wrapping it in almost 500 crystalline panels to create the glimmering facade.
11:03Finally, the building's beauty is starting to shine through.
11:08When you're inside, walking along the corridors alongside that facade,
11:12which is getting all of these reflections, it's like being in a kaleidoscope.
11:19The next major challenge will be creating the wood-covered passageway,
11:23which was inspired by the weather over the Rocky Mountains.
11:28When two pressure systems meet, they create this arched cloud,
11:31this vast arch, and it can stretch 100 miles across the horizon.
11:36It's called a Chinook cloud.
11:38To create this swooping overhead entrance,
11:41they decide to use locally sourced western red cedar timber.
11:46Beautiful, durable, and sustainable, but not very pliable.
11:50Once you bend a piece of wood to a certain point, I mean, eventually it cracks, it splits, it breaks.
11:56In Calgary, Alberta, Canada, the team behind an incredible library built on top of the city's light rail train
12:07or creating a swooping entrance made from local red cedar timber.
12:14But how do you bend a huge wooden arch without breaking it?
12:18You reboot technology used by the ancient Egyptians.
12:25Steam bending works by placing wood into a sealed box and filling it with steam.
12:31The heat and the moisture soften the wood just enough to bend it into shape, but only for a short critical window.
12:37It created this incredible, intense moments in manufacturing where it would be,
12:44okay, go guys, steam box is ready, we're taking the battens out of the box,
12:48we gotta run over to the jigs, push them down before they kind of harden.
12:53Twisting and bending the arch in two directions is incredibly complicated,
12:59and needs some 21st century technology to help pull it off.
13:03We created a highly accurate three-dimensional computer model of the entire ceiling structure
13:10to be able to know exactly where each piece of timber should go,
13:14and we used incredibly complex software algorithms to actually model the geometry of each individual wood batten.
13:22Then, the 21,000 square feet of curving cedar needs to be fitted quickly.
13:29Due to the schedule, we had to build this ceiling structure with two crews at once.
13:36So we started from the ground, as you can imagine, with one crew,
13:39and we started way over here at the other end from the other crew,
13:42and then there's this moment where they had to meet in the middle.
13:47We weren't sure, was it gonna actually meet?
13:52Four months after starting, they're about to find out.
13:55I still remember our site supervisor calling me, and he was like,
14:01it fit!
14:03Just an incredible moment, right?
14:07After four and a half years of construction,
14:11on November 1st, 2018, Calgary's incredible new central library opens its doors to the public.
14:21That opening day was so amazing.
14:25To see everyone else see what I'd seen over the last five years was very emotional.
14:32When we first came here, we were like, wow, this is amazing.
14:36Definitely, we have to come back.
14:39I walked in here, and it was like, wow, I couldn't believe what I was seeing.
14:42It didn't look like a library to me.
14:44This is breathtaking.
14:46But this is more than a library.
14:50Its extraordinary timber-framed walkway sits above the railway,
14:53healing the divide between the East Village and the rest of downtown.
14:59With the addition of the library, East Village has really gone from a part of our downtown
15:05to being a part of Calgary that shouldn't be missed.
15:08A temple to reading unlike any other on the planet.
15:14It's just such an incredible building and an incredible library.
15:18I think Calgary has absolutely redefined what a library can be, and I would argue should be.
15:24When architects were tasked to build a new skyscraper on a super-tight deadline,
15:41they turned to a never-before-used construction concept to get it done, SpeedCore.
15:46And while any new engineering technique comes with a degree of risk,
15:50the people of Seattle were less concerned about the building going up,
15:53as they were about the 50-year-old architectural masterpiece next door crashing down.
16:02Seattle is the largest metropolis in the Pacific Northwest, with a stunning skyline to prove it.
16:09And in 2014, there are plans for a colossal new skyscraper to join it.
16:14The build site is on a block that is already home to the beloved Rainier Tower,
16:21a skyscraper whose chewed bottom has earned it a nickname.
16:27Locals call it the Beaver Building, and it was designed by Seattle-born architect
16:32Minoru Yamasaki, who's best known for New York's Twin Towers. So it's pretty special.
16:38Not surprisingly, the space comes with some seriously tight building restrictions.
16:46Any development plan for the remaining three-quarters of the block
16:50should not obstruct the views in the original Rainier Tower.
16:54That, though, isn't enough to stop Seattle architects in BBJ
17:00from coming up with a radical plan for 58 stories of mixed-use space.
17:04Retail at the bottom, offices in the middle, and then 18 floors of residential units at the top.
17:14Building it will come with a whole set of challenges.
17:18Because first, they will have to dig down 100 feet to create the foundation
17:22without bringing down its 50-year-old neighbor in the process.
17:29Then, they must stop the soil around the foundation from caving in.
17:35A traditional concrete core is going to be too slow and too expensive,
17:39so they need to find a revolutionary new way of holding the building up.
17:45And when they've done all that, the finished tower needs to complement the Beaver Building
17:49and not get in the way of its views.
17:55Definitely, probably one of the more complicated projects that
17:59I have been part of and our team has been part of.
18:04On May 8, 2014, the team wins the contract.
18:09The search for an engineer is on.
18:12Luckily, they don't have to look far.
18:16The building was literally right outside of my personal office window, 60 feet away.
18:21Having worked in the Beaver Building since the 90s, Ron knows the site, warts, and all.
18:29Of the many challenges on this building, one that we faced straight away was,
18:33how are we going to make the below-grade levels, the basements, if you will?
18:38The new Rainier Square Tower will have a six-story parking garage, all underground.
18:44And that means digging a very big hole.
18:48It's very daunting where you're going to dig a 100-foot hole immediately adjacent to an occupied
18:5440-story building.
18:55So this was kind of challenge number one.
19:02In Seattle, work starts excavating for the foundation of an enormous 58-story tower,
19:09which will sit feet away from one of the city's most iconic buildings.
19:15It's nothing if not challenging.
19:18How do you do that while not putting in peril the existing 40-story building?
19:23It's extraordinary shape makes it all the more difficult.
19:29What's really unique about this particular tower is that the base of the tower is a pedestal.
19:35This incredibly small footprint means it's putting even more pressure on the soil beneath.
19:43To stop the excavations from bringing it down,
19:46the team must hold the soil under the original tower in place by building a huge wall.
19:53The best analogy I can offer you, if you can imagine a dam that's holding back not water,
20:00but dirt. And that dirt happens to have a 40-story building on top of it.
20:05Perhaps, not surprisingly, this wall needs to be pretty special.
20:10The actual dam or the wall that we built is a secant pile wall.
20:16A secant pile wall is a set of overlapping concrete columns.
20:22Normally, a secant pile wall might be 24 to 30-inch diameter holes. In this case,
20:27we had holes that were five feet diameters. With the wall in place, work progresses very carefully.
20:37There was a very extensive monitoring system set up to determine if the building itself was moving in
20:42any way that was of any concern.
20:49It moved, but it moved within expectations. It all performed as it was intended to perform.
20:57Their next challenge is going to be building the tower.
21:02Around the world, many, many tall buildings have been designed and constructed
21:07using what is a reinforced concrete core.
21:11It's a column that runs through the center of the tower and usually houses the elevators and stairwells.
21:19It's what gives big skyscrapers their strength.
21:22It's a tried and tested method. But here, there's a pretty big problem.
21:27We made an evaluation of the cost and the time required to build that design.
21:34And the conclusion was that it cost too much and it took too long.
21:38And that was our cue to introduce this idea of SpeedCore.
21:44Developed in the 1990s in the United Kingdom, the SpeedCore building system was largely unknown.
21:52At the time, I'd never heard of it, but it had been used in nuclear facilities before
21:57for blast resistance, but never in a high rise.
22:01The concept of SpeedCore is to prefabricate steel modules and then stacked up one on top of another,
22:09kind of like Lego blocks. Then to add to its strength and stiffness, fill them full of concrete.
22:16Using it here to create the tower's strength will be revolutionary.
22:20What's amazing about the SpeedCore is you're able to build
22:24the core and the floors at the same time, which is where you're saving a huge amount of time.
22:31In theory, building this way will make it cheaper and quicker.
22:36We're able to go back to our client and report.
22:38But lo and behold, we think we can save 10 months on the schedule.
22:41And the client says, go for it.
22:46So 170 miles away in Portland, they start fabricating the steel module.
22:54These panels are very large.
22:56They were 14 feet tall and 30 to 40 feet long, and they weighed on the order of about 9 tons each.
23:03In October 2018, the first steel panels arrive on site in Seattle.
23:09As an engineer, this is a huge moment. If it works, it will reduce the schedule by months.
23:16If it doesn't, it will be a disaster.
23:21The team hold their breath as work gets underway.
23:26The first job is putting the steel modules in place.
23:29The core is composed of a bunch of sandwich panels, and then they're joined together
23:38to the next panel to complete a core section.
23:43Our panels were welded together. We didn't want to do a bolted connection,
23:48because having to line up bolt holes is very, very difficult.
23:53In the end, there was 26 miles of welding in this building.
23:59Normally, you do not measure welding in miles. That's not a unit of measure that's very typical.
24:07As they're filled with concrete, the tower shoots up.
24:11The biggest difference is just seeing the units put together
24:15at such a speed that you've never really seen before.
24:18They were able to set one entire floor of walls in a day, in one day, as opposed to five days.
24:25But as they get to 850 feet, there's a very different challenge. The team needs to defy the laws of physics.
24:34Pumping concrete at height is really kind of technically challenging. Just pumping something
24:42up 850 feet, you need to overcome the force of gravity to overcome the friction within the pipe.
24:49To pull this off, clearly any old concrete isn't going to do the job.
24:55We knew that it needed to be high strength. It needed to be very flowable, because it was going
25:01to have to flow from one module into the next. So we worked on an appropriate mix.
25:06What they came up with was a thinner mix with no aggregate in it that would fill the modules.
25:13The only downside was that it would take longer to set.
25:19It's a huge success. The Speed Corps knocks months off the construction schedule,
25:24leaving the team ready to face their next challenge, the glass facade.
25:32This is by far the most complex project that I've ever done,
25:35and I think that we as a company have ever done.
25:43In Seattle, work is about to begin on the curving glass facade that will maximize the tower's floor
25:49space while keeping the neighbor's view. But building it will be a nightmare.
25:56The geometry of each floor is different, so it just creates a lot of unique challenges for us.
26:00It's their steps up to level 40, and each floor has a unique step inward to the building.
26:09Usually, a skyscraper's glass skin hangs on an aluminum frame,
26:16where the bars that hold the glass in place slot together neatly floor after floor.
26:23But that doesn't happen here.
26:25Because every floor steps back a little, the vertical bars don't line up. Instead of nice,
26:31clean, 90-degree angles like you normally have, every connection is off by a little bit.
26:38To overcome this, they turned to a technology used in aeronautics, but rarely in construction.
26:45What we ended up deciding to do was look at a way to have a node that was 3D printed out of
26:55aluminum that kind of takes up all the geometric complexities into this printed part.
27:03Turned out really good. It's super precise.
27:05With each set of connectors individually printed, the team can now seal the building
27:14with the thousands of windows that make up the exterior.
27:23It's cool because no matter what side of the building you look at,
27:26and what corner you're looking at, there's so many unique aspects of it.
27:35In September 2020, the last window slides into place,
27:40finishing the three-year build and revealing Rainier Square Tower in all its glory.
27:54It's the most iconic project that I've ever done, and I think we've ever done as a company too.
27:58It's up there, highlighting my career.
28:01At 850 feet, the 58-story tower becomes the tallest mixed-use building on Seattle's skyline,
28:11elegantly complementing the iconic tower next door.
28:18Seattle has been changing significantly over the years, and to be able to add a significant project,
28:25to me, this is a once-in-a-lifetime opportunity.
28:27With 734,000 square feet of office space and 189 luxury apartments above, it may dwarf the neighbors.
28:39Its clever design, though, gives Ron the best seat in the house to watch over it.
28:46Every day that I came into my office was able to see the progress,
28:50was able to see the speed at which things were happening, and even somewhat frighteningly,
28:55seeing the steelworkers walking on the steel beams in outer space,
29:0030 or 40 stories in the air, right outside my window. It actually gave me knots in my stomach.
29:07Creating this tower has truly been an incredible journey, with results that speak for themselves.
29:16Everyone came with this mentality of,
29:19we don't necessarily know how we're going to get it done today, but we're smart and we'll figure it out.
29:32Would you use this toy to build a bridge?
29:35In Brisbane, Australia, they did.
29:37Well, sort of.
29:39Architects use the same principles of tension and compression that makes this toy enjoyable,
29:44to create one of the most revolutionary and fun bridges on Earth.
29:50How'd they do that?
29:55In the early 2000s, the city is growing fast.
30:00It needs a new bridge to cross the Brisbane River,
30:03linking the north side's busy city center to the Arts District on the South Bank.
30:09It was thought that it would be good to have more connections across that river,
30:13a pedestrian and cycle bridge out of the city, so that more people would walk and be healthy and cycle.
30:22So the city launches a competition for a bridge that will complement Brisbane's buzzing arts district.
30:30The bridge is located virtually at the front door of the Gallery of Modern Art.
30:36It needed to be a piece of art, a big piece of art.
30:39The engineers behind the iconic Sydney Opera House think they've got the winning idea.
30:46We looked at lots of different bridge types, but the one that met the brief best,
30:50in terms of being unusual and wonderful, was this idea of a lot of
30:55masts and cables to make it look like a sculpture.
30:59So how do you build a bridge that's also a work of art?
31:03You attempt something that's never been done before. Use a little-known engineering principle called tensegrity.
31:10Tensegrity exists in sculptures like this, where tension cables like these,
31:17hold isolated elements like these rods in place, creating a stable, self-supporting structure.
31:26Local architects Cox Rainer are up for the challenge.
31:29What excited us all was trying to do something that hadn't been done before.
31:38The thing about tensegrity is it doesn't make sense, and that's the mystery of tensegrity.
31:46You end up with something that looks like it's made out of sticks and string,
31:50or cat's cradle, as my son called it when he first saw it.
31:54The idea is that the entire bridge will be supported from above
31:58by this cat's cradle system of poles and wires, instead of by pillars underneath.
32:04If they can pull it off, it'll be a world's first.
32:08This was an opportunity to see can we apply the principles of tensegrity to a real, solid,
32:14big structure and make it effective.
32:19The team hopes to build a bridge across a 1,000-foot-wide bend in the Brisbane River,
32:24using tensegrity, and that will be both highly functional and look like a piece of art.
32:35First, they will need to find somewhere to construct the two supporting peers.
32:40One in the river itself, clear of the shipping lane.
32:43The other on the crowded north bank, home to an eight-lane freeway and bicycle path.
32:49Next, they'll have to find a way to support the bridge while they build out from each pier.
32:59And they need to make sure both sides meet in the middle.
33:08Then, somehow, the entire bridge needs to be supported from above with a complex system of
33:14cables and wires. And, as if that's not enough, the whole thing has to be finished in time for the
33:21state of Queensland's 150th birthday party in two years.
33:28This tensegrity bridge, it had never been attempted anywhere in the world,
33:33and we saw this as a milestone for Queensland.
33:37The place chosen for the bridge has great significance to the people who lived here first.
33:46Before work can start, the team consults with the local tribes.
33:51For thousands of years, it was the main crossing area for the tribes.
33:56Parents would carry their babies on their shoulders, or even the mothers on their babies,
34:01because it wasn't very deep.
34:02There's great cultural significance with the particular bridge location.
34:06We were a little bit nervous that we might not be doing something that the traditional owners
34:11thought appropriate.
34:15They spoke to us and asked us if we wanted to be involved, and we gave them names for the bridge.
34:23Kurilpa refers to the little kangaroo, rat, that's on the bend of the Brisbane River.
34:30That's the meaning. Kurilpa is the little kangaroo, rat, that plays on.
34:36With the bridge named Kurilpa, work begins in December 2007.
34:45The first job is finding somewhere to sink the two piers that will anchor the bridge on each side of the river.
34:52There were many challenges to the site. One was we had to cross a freeway on the city side,
34:59which was operational. There's a navigational channel as well, which usually in this river is
35:04somewhat in the middle. But in this particular location, it was located over towards the south bank side.
35:10A site is found in the river that sits clear of the shipping lane, but it brings many more challenges.
35:19We had professional doves that had to go down and dig the shelf and start the very first temporary pier
35:26in muddy water that had basically zero vision with great knots of water going through.
35:33It's critical that these piers are going to be strong enough to withstand whatever
35:38nature throws at them.
35:39The Brisbane River is well known to be prone to flooding. So you try and make sure that,
35:46A, you can resist the floodwaters, but B, anything floating down the river on the floodwaters.
35:56In Brisbane, Australia, the team is in the middle of constructing an extraordinary new
36:01pedestrian bridge, which has to be tough enough to handle a collision. The largest barge, I believe,
36:08was like a 2,000 ton barge going out of control, coming down in a flood event. So they had to
36:15withstand ship impact. And that means anchoring it to the riverbed. The main river up here of the Karupa
36:24bridge is supported on approximately 16 poles that go 18 feet into the rock. They're socketed in,
36:33but the only way we were able to socket those in is to basically drive through the alluvium that was
36:40at the base of the riverbed, approximately 10 feet, filled up with grout, a bit of concrete for mass or
36:48damping effect. They're all joined together and we concreted the pole cap in there.
36:53With the In River Pier secured on the South Bank side, the challenge is finding somewhere to build
36:59a pier on the North Bank. You had the Riverside Expressway, which is the busiest
37:05motorway basically in Eastern Australia, or definitely in Brisbane. You had the Bicentennial
37:09Bikeway and you had the Brisbane River itself. The only space to squeeze it is between the
37:16eight-lane expressway and the city's main bike path. We had to carefully bring a pier up between
37:24the two structures and also maintain the operation of the Riverside Expressway.
37:31To keep the project on track and traffic disruption to a minimum, the team works through the night.
37:38You can imagine all the lead-up work to understand what the total numbers were,
37:42and understanding the peaks in traffic flow on the Riverside Expressway, and actually how many
37:47night closures we'll need, how many day lane closures we had to make. Very challenging.
37:53After 12 months, with both bridge piers in place, attention turns to the next challenge.
38:03How to build the 420-foot deck between them.
38:07The problems with tensegrity are to do with construction, because it really only works when
38:17it's finished. All the cables are stretched, and they're all taught, and they all work in concert,
38:22but when you're building it, the cables are slack, so nothing is supporting the bridge deck.
38:27Where all the cables and poles are tight, the system works together to create this perfect balance of
38:34tension. But when they're not tight, the whole thing stops working. There's no support at all.
38:43The team has to find a way of supporting the bridge while they build it.
38:48We wanted to avoid putting any temporary piles or piers into the river itself that would get in
38:53the way of navigation. So it was a very intimate collaboration between builder and engineer,
38:59unusually intimate, to exactly work out the construction methodology.
39:04Their answer is to build the bridge out one mass and unit of precast deck at a time,
39:11and hope it stays up. There were many sleepless nights. There was always a fear that something could
39:19drop from that bridge under construction. That was my main concern.
39:24It was this idea of a self-extending construction method. You held up one bit of bridge from the
39:32mast you'd already erected, then you put down another mast, and that held it up the next bit of bridge.
39:36As they build out, temporary support struts hold up the bridge.
39:43To make clear which are permanent masts, the temporary supports are colored red.
39:48We had a lot of temporary works there, and that's when the structure is challenged its most,
39:55when it's under those extreme forces and under temporary works control.
40:00You know, you're going over one piece at a time, you're connecting one cable at a time,
40:05and to make it all match up to the millimeter, that was pretty challenging.
40:09As both sides of the deck extend out, the question is, will they meet in the middle?
40:18As you build it, it moves a lot because the cables stretch. At some stages, it was up to a meter
40:25out of position. So there was a nervousness. You knew it would have to be swaying because
40:30there was nothing holding it there.
40:32So as the last piece comes along, you still don't know, because it's still a long way out of position,
40:40whether the last piece will do the job it's meant to do, and lower it just enough to make it join
40:45together. But the bridge went in absolutely perfectly, which we thought was an astounding
40:57achievement by the combined team. It means the cat's cradle of cables and masts can be locked tight
41:04to start holding up the bridge, and temporary support struts can be removed.
41:11It was a great moment. It gave everybody a great sigh of relief and excitement.
41:20But with less than four months until opening, there's a problem with the deck.
41:24So since the Tacoma and Arrows bridge in America, which failed in the 50s,
41:31we've known that some bridges, if they have very thin bridge decks, are susceptible to galloping or
41:37lateral torsional twisting in the wind, where the bridge ends up collapsing because it twists more
41:43and more and more as the wind goes. Karupa Bridge was found to have that susceptibility when we modelled it
41:49in a wind tunnel. Which isn't good news in a city like Brisbane that's vulnerable to tropical cyclones.
41:57So the team comes up with an elegant engineering solution. So we added little fairings on each side
42:05that just control the wind enough to stop that effect. The simple triangular fairings improve its
42:11aerodynamics. So the wind flows over the walkway and doesn't catch it, making it twist.
42:19It prevents it from starting and therefore you never get into that mode of instability.
42:23Finally, on October 4th, 2009, Karupa Bridge opens to the public.
42:37And in time for the state's 150th birthday.
42:40I came up to Brisbane for the opening. Everybody was overjoyed because it came out exactly as we
42:48hoped it would at the beginning. We just felt that we'd really created something that contributed to
42:53the city. I like it because it's an olive branch that we were asked to be involved. There was a time
43:01that wouldn't even be a second thought to talk to the traditional people from the area.
43:05And at night, a photovoltaic lighting system transforms it into a colourful work of art.
43:15The bridge is beautiful. It allows people to stop on the way to sit above the river. There's
43:21little seats there. It's the wonderful sight. I go for my runs every single day on it. I use it for
43:27daily walking as well. I use it every day I'm at work so that I can go for a walk at lunchtime.
43:33And then back up that hill. That's a great workout. I love it.
43:38It's just nothing like I've ever seen before.
43:42I never really thought as project director that it would put Brisbane on the map.
43:46I couldn't be more proud of this project.
43:49A true world first. Karupa Bridge takes its place as one of the most audacious and technically ambitious
43:56ever built.
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