Longest pedestrian suspension bridge opens in Portugal | Hacker News Reader

Longest pedestrian suspension bridge opens in Portugal

reuters.com

109 pointsawb68 comments

The article loaded for a second and then was replaced with all sorts of other bullshit; here's another link if anyone else is suffering

https://www.npr.org/2021/04/30/992456396/portugal-opens-worl...

Also

https://en.wikipedia.org/wiki/Arouca_516

+ OSM:

https://www.openstreetmap.org/way/813680468#map=15/40.9634/-...

In case you want to just have a look at the bridge without going nuts.

https://i.cbc.ca/1.6007355.1619716182!/fileImage/httpImage/i...

The bridge also has its own website with photos: https://ponte516arouca.com/en/516-arouca-worlds-longest-pede...

Huh... websites. What a great idea.

I confirm some Reuters articles just disappear after opening the page. Been doing that since the new redesign, a few days ago. We are witnessing the slow death of Reuters.

According to the article this bridge cost €2.3MM to build, which seems crazy cheap, even for Portugal. Does that sound low to anyone else?

Doesn't sound too unrealistic. It's long but not very big. 1.2m in width. That does make quite a big difference in cost. So it's more of an walkway than proper bridge.

This reads like a puff piece, so I second your skepticism.

Yes, it sounds low to me. In Brazil they've have spent 10x that and would never finish it.

Well, give us an example then?

https://www.atlasobscura.com/places/viaduct-petrobras

https://brasil.estadao.com.br/noticias/rio-de-janeiro,telefe...

https://istoe.com.br/447384_A+CICLOVIA+MAIS+CARA+DO+MUNDO/

http://www.ihu.unisinos.br/78-noticias/579871-o-desastroso-l...

https://www.otempo.com.br/politica/mp-faz-operacao-para-apur...

Maybe because it's a pedestrian bridge? Cars are way too heavier (and you usually have 4 lanes)

Cars are lighter than people, because people pack much more tightly than cars do.

People have a design load in the 100psf range, cars are about half that.

(Source - I designed a pedestrian bridge in Seattle before leaving civil engineering)

Is it also more ornerous to control for oscillations in pedestrian bridges? Does that require extra structure, or just tuning?

Yes and no. It's certainly something to think about when you have an 'interesting' design that pushes the limits somewhere, and pedestrian bridges often are have that sort of arty component. Or, you don't and it's embarrassing if there's a resonance in the 1-2 second range.

Most road bridges just aren't that interesting. They're a concrete slab on a girder, either steel or precast, depending on your local construction environment.

(As my bridge wasn't structurally terribly interesting in the end, the biggest issues were clearance with the railroad below while fitting into the height profile we needed for the surface, given the 100yr old elevated structure we were connecting to. That and the extremely low quality soils at the site)

In comparison, a 300 meter utility pipes and pedestrian suspension bridge in Canada cost $12M CAD (approx €8M) a few years ago.

It was wider and stronger than this one to support the pipelines, and also required larger towers to support it on either end, which are surely a large part of the cost.

So it doesn't seem unreasonably cheap.

I opened the comments specifically to see if anyone else thought the price was unrealistic. I'd be surprised if that price would even cover the cost of materials.

Article says 1700lf and looks about 4ft wide, so that’s 6800ft of bridge deck. At $2.8M that would mean they spent $412/sf of deck. Where I live, the state DOT spends about $150/sf of bridge deck for traffic rated bridges. I’ve gotten prices for prefab ped bridges as low as $110 delivered (still have to pay a half-dozen guys for labor and the cost of a crane to place).

I guess there were some special construction challenges, but $415/sf is hardly a bargain for a bridge at first blush.

That may be low in some places where capital improvement costs are basically just graft.

It does sound awfully cheap to me. For reference, if you ever been to Las Vegas and walked on those pedestrian bridges on the strip , the approximate price tag of those 15 years back was around $20 million.

https://m.lasvegassun.com/news/2004/dec/09/cost-of-pedestria...

They all have multiple elevators and escalators, are sturdy enough to handle hundreds of people simultaneously, and were constructed over some of the busiest roadways in the world. Not really apples to apples.

For comparison, the Don Burnett Bicycle-Pedestrian Bridge over 280 cost just shy of $15 million, and is about 150 m long.

A 110 foot (33.5m) long pedestrian bridge in Atlanta cost over USD$23 million. Part of the cost was to get it ready in time for the Super Bowl. Due to security concerns, it was cordoned off and no one was permitted to use it during the Super Bowl.

Yeah, that sounds more like what I was expecting!

It sounded very cheap, and then I looked up what these types of bridges normally cost, and now it sounds expensive. The former world's longest pedestrian bridge, the Charles Kuonen Suspension Bridge in Switzerland, cost 720k Francs - and that was built in the Alps, with Swiss labor costs (Switzerland has the highest minimum wage in the world.)

By contrast, the minimum wage in Portugal is the lowest in Western Europe by far, at 665 euros (!!!) per month.

It's not like this bridge was built in particularly inhospitable terrain or something - it ends less than 300 meters from a paved road. The Swiss bridge appears to be 1750 meters from the closest road.

The bridges are very similar lengths - 494m vs 516m - and similar construction.

So why did the Portugese bridge cost 3.5x more?

As with most southern European countries, the answer is corruption.

Geierlay suspension bridge in Germany is 360 meters, costed 1.2 million euros. I guess germany is in southern europe too.

Pretty sure Germany has more corruption than Switzerland. It is just better hidden than in southern europe.

In this case I think Switzerland is the outlier though. The country is extremely efficient with alpine infrastructure.

Or could it perhaps just be that the requirements of the bridges are different? Things like oscillation tolerance, minimum width etc. Perhaps dictated by local laws and/or the kind of target public they want to attract, the average number of days a year the weather would permit transit etc etc ?

You are pretty much exactly describing how corruption works in a well regulated country. Since officials can't just pick the contractor but have to take the cheapest bid for the given requirements, they have to doctor the requirements until the contractor they want to hire has the best chance of making the best bid (or be the only contractor that effectively make a bid at all). This is exactly how it works from the lowest up to the highest level of government.

Since actual corruption is so hard to measure, we rank countries along a line of "corruption perception", i.e. how confident are people. Germany has an extremely good reputation. I believe you have to look at individual projects though and use a first principles approach: how much should it cost? What level of incompetence is believable vs plain corruption? Does the project make sense given larger government policy in the first place? Airport Berlin-Brandenburg, Wirecard, Nordstream are just the larger known cases, where corruption is the only possible explanation, there are tons of smaller projects as well, on which nobody bothers to put the spotlight.

It sounds like you are describing monopolies or regulatory capture. And sure enough, the US and Germany have some of the least competitive infrastructure construction markets.

The answer is corruption? Was that comment necessary? Do you have information that we don't have?

Also, it's not like corruption doesn't happen everywhere. For instance, not so long ago the Estonian government (that would be Northern Europe, I think) resigned because a corruption scandal (1).

https://www.theguardian.com/world/2021/jan/13/estonian-gover...

Is it tho? Or could it be the massive building boom in Portugal right now raising the prices? Or the fact that kind of "alpine" construction is very rare in Portugal and probably required a lot of foreign expertise? Or perhaps because there weren't many contractors biding on it, leading to a less competitive price? Or maybe because they're totally different designs? Or maybe there's a ton of factors you have no idea about and did no research on?

Corruption is really not as common in southern Europe as the media would make it out to be. Incompetence is a far bigger problem and also far harder to persecute, sadly.

Heh not really rare. They've been building loads and loads of crazy infra up in the mountainous North.

To quote myself from a comment on high speed trains the other day “[The French] build high speed lines for between 1/5th and 1/20th of the cost of the one the UK is building. Just to prempt the France is flat and land is cheap arguments. 1/5th is the cost of the section of line between Lyon and Marseille that crosses the Massif Central with 50 tunnels and bridges and plenty of earthworks. The cost of land acquisition is only £8bn of the £100bn+ cost of HS2.” So if we conclude this kind of cost difference is corruption, we clearly have a much bigger problem in Britain.

Well the other comments might be jumping to conclusions (which might have had an impact of course).

But the Portuguese bridge is over a river, this one is over a valley (though sure, the alps are a complication). They're also built slightly differently if you see the photos.

But yeah I think it's not only due to simple reasons.

You won't find any good builing workers at that price though. You're talking Switzerland, most of the construction work in Switzerland is foreign Portuguese workers. So the price in Portugal has to adjust slightly towards to Swiss prices if they want to hire any good people. Europe!

Puts into perspective how expensive car bridges really are.

Those two massive holding towers look completely out of place:

https://i.cbc.ca/1.6007355.1619716182!/fileImage/httpImage/i...

How come they couldn't build something like in Charles Kuonen hanging bridge (no tower), it's just 20m shorter:

https://media.schneemenschen.de/image/db/222235_haengebrueck...

My only guess would be since it's a suspenson bridge, maybe the length requires that type of bridge. I'm no bridgengineer though, and haven't looked up and compared the types.

It looks like the tradeoff is the angle/rise. The Kuonen bridge requires a 3,000 foot rise in elevation as you walk up it, so it has a sort of in-built tower on one end. The one in Portugal looks relatively flat in comparison.

The new bridge looks significantly wider than the Charles Kuonen bridge, so I guess it'll be heavier per meter.

For me, they look kinda epic :). I like the overall look a lot. But I can see your point about trying to be more minimalist and less invasive.

They point out the largest one in the US is the Gatlinburg SkyBridge https://www.gatlinburgskylift.com/skybridge and it looks like Eagle Canyon is the largest in Canada https://www.eaglecanyonadventures.ca/suspension-bridges/

Kind of sad that both of those bridges, as well as this new bridge, are all paid access. Walking on a bridge is one of those things you just take for granted as being free, I guess, until it isn't.

Thankfully, the former world's longest pedestrian bridge, the Charles Kuonen Suspension Bridge in Switzerland, is totally free.

It's not like these bridges are particularly expensive, either. The former longest in Switzerland cost only 720k euros to build, and that was constructed in the Alps by a Swiss company with expensive Swiss labor (I seem to recall they have the highest minimum wage in the world.) Seems like an excellent and cheap thing to build if you're a town looking to boost tourism.

Generally, there's no minimum wage in Switzerland (though some Cantons have one, Geneva is at $25/h). But yes, Swiss labour is expensive anyway.

Short video: https://www.theguardian.com/world/video/2021/apr/30/worlds-l...

On Alaskan Hiway they had see-through automobile bridges. Little uncomfortable to bicycle on, mostly because of damage on tires. https://youtu.be/pL2OtC_VLsU?t=1793

Very cool, although you'll never see me on it!

A perfect thing to look at from afar.

You are not the only one. There are dozens like us! Dozens!

This type of bridge is (was for me) an effective way to get over fear of heights. I went on multiple long treks in Nepal in 2019 and you don't have a choice in crossing bridges like this, other than turning around and canceling your trip. The first bridges was absolutely horrible and at the end of the trip the bridges (or other more unsafe places, like narrow trails with big drops) didn't bother me at all.

Obligatory bridge collapse fact: there have been a few historical bridge collapses resulting from walking/stepping/marching which causes vibrations in the bridge that create a feed back loop further syncing the stepping intensifying the vibrations ultimately leading to the failure. Soldiers are supposed to break stride when crossing bridges to prevent collapse.

Some people have a fear of the heights of these bridges, I have an irrational fear of vibrational collapse.

Back in the 80s the city of SF encouraged people to walk in the GG Bridge to celebrate its 50th anniversary.

Almost destroyed the bridge and killed everyone on it.

I feel like I remember that, but might be confusing it with another bridge incident. I remember there being elephants in the celebration, significant “waves” in the bridge and some pretty serious injuries...but again I may be confusing it with another incident.

Edit: watched video, GG flattened out. Not sure what I am remembering and maybe mixing up a few bridge “disasters” and collapses into one.

I looked it up and it seems that's not what happened.

_While there were some injuries, there were no fatalities and the bridge was not damaged._

_The weight of the 300,000 people flattened the normally arched roadbed, although bridge engineers later said there was never any real danger._

Source: https://www.sfgate.com/local-donotuse/article/Golden-Gate-br...

I read the same claim on Usenet about 30 years ago and researched it. My conclusion was that soldiers break stride to avoid nasty oscillations, but I couldn't find any actual collapses. There was one bridge that was claimed as a collapse from people marching on it, but it was actually very high winds that caused the collapse.

Well, London's Millennium Bridge did not collapse, but it did sway alarmingly when crowds of people walking on it were forced into resonance, resulting in the immediate closure of the bridge before it could be fixed.

https://en.wikipedia.org/wiki/Millennium_Bridge,_London#Reso...

And even now people still call it the “wobbly bridge”.

Apparently an incident took place in 1831 where a bridge collapsed under soldiers marching, but the Wikipedia article [1] notes that "The conclusion of the investigation was that the vibration caused by the marching precipitated the bolt's failure, but it would have failed eventually anyway".

There's more interesting information on synchronization and bridges on Veritasium's video, The Secret of Synchronization [2].

[1] https://en.wikipedia.org/wiki/Broughton_Suspension_Bridge [2] https://www.youtube.com/watch?v=t-_VPRCtiUg

That video link about synchronisation is very interesting. Thankyou. Synchronization of bridges, hearts, lightning bugs, metronomes, sailing clocks. Cool

In a documentary about London's Millennium Bridge, they showed videos of other bridges collapsing due to it. Sorry I don't have a link, just saying it's out there.

The Albert Bridge in London even has signs to remind soldiers to break step:

https://www.londonremembers.com/memorials/albert-bridge-troo...

Has "municipality builds kinda neat thing to revitalize local economy" ever worked?

Investing in tourist infrastructure in natural parks to increase tourism revenue? Why wouldn't that work?

Take a look at Niagara Falls, for example - those viewing platforms and paths and boat launches aren't natural features. Making it easy to get access to spectacular views seems like a pretty good investment in general.

When you throw millions at something, there is always something that works. The question being, is it better than not taking this tax money at all so citizen could revitalize their economy themselves.

In this case, it does. Bridge toll is 12€ per person, and it's inserted into one of the most popular pedestrian course in Portugal (Passadiços do Paiva).

This is a pretty nice region, they'll have lots of competition.

If you are coming from far, you'll likely prefer to spend your time in Porto and Aveiro.

I guess they'll have more local visitors. If I were in Alquerubim I'd definitely go there on the weekend.

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