Bridge down in Northolt - Paddington Arm

[IanD]

21 hours ago, 1st ade said:

I can't see...

...happening in 2023

We were both wrong then... 😉

[J R ALSOP]

On 18/03/2023 at 23:05, Goliath said:

Some lovely timber

surprised it ain’t been got at

 

It is laminated

On 19/03/2023 at 08:20, magnetman said:

Wood Hall Hewards ILDA would shift it. 90HP cummins and a four leaf clover prop on her. No worries !

 

 

 

Probably a lot of rubbish there though so would want a long stretchy line and snatch it rather than drag I think.

I don't do that anymore

[MtB]

3 hours ago, J R ALSOP said:

On 18/03/2023 at 23:05, Goliath said:

Some lovely timber

surprised it ain’t been got at

 

It is laminated

 

Is it?

 

From the article:

 

"David Posnett, of the Friends of the Grand Union Canal, said: "While the loss of this beautiful oak bridge is sad, Ealing Council correctly identified it was unsafe and closed it several years ago. "

 

Laminated oak perhaps?

[J R ALSOP]

I have been under it hundreds of times whilst working down there, it is/ was laminated, but what wood I wouldn't know.

[magnetman]

Obviously bad quality it is lucky nobody was going under it when it fell. This could could have severely damaged someone's Buckby can.

[Chris Lowe]

They make buildings using glu laminated timber, glulam beams, they are structual as well as look good.

[IanD]

50 minutes ago, magnetman said:

Obviously bad quality it is lucky nobody was going under it when it fell. This could could have severely damaged someone's Buckby can.

The female boater I mentioned nearly did ...

[Tim Lewis]

Open but not exactly cleared!

 

 

[Pluto]

This is my favourite wooden bridge, at Essing, on the Rhine-Main-Donau Canal. It is the world's only bridge using wooden beams in tension, and is called the Tatzlwurm. When they were building the canal through the Altmuhl Valley there was a lot of controversy, so for this section they had a series of competitions for each new bridge, and this was one of the winners. The gentleman bottom right was the English senior engineer for the canal. This photo was taken in 1994, and I was there again in 2018 when the bridge was still in excellent condition.

[Bacchus]

I bow to something of which you clearly have knowledge, but am struggling to see how that deck is in tension? It looks as if it is created to mimic a member following a basic catenary - at least I am guessing that it is a mimic with the glu-lam beams which are great in bending? The V-shaped supports look like members in compression which would make the bridge-deck a basic beam?

 

ETA  - fexcellent bridge whatever 😁 thank you for posting

Edited March 20, 2023 by Bacchus

[MtB]

21 minutes ago, Bacchus said:

I bow to something of which you clearly have knowledge, but am struggling to see how that deck is in tension?

 

Phew. I too was thinking that, but not so sure of my ground as my brain is mashed after ringing two touches of Bob Minor and two of Stedman Doubles tonight...

 

 

[Pluto]

It is definitely just in tension, and hangs over the two supports. Here are another couple of photos, one showing the joint holding the bridge in tension. It is a really interesting area from the canal enthusiasts point of view. Besides the modern canal, there are remains an aqueduct built undertaken during Hitler's time, when the new canal was first started, there is also the remains of Ludwig's Canal which opened in the 1830s, and the Fossa Carolina, the first Rhine-Danube link built by Charlemagne in 793AD. There are also some canal remains around Munich; another good reason for going to the Oktober Fest.

[arbutus]

A quick Google brings up this site

https://trid.trb.org/view/384852

 

THE ESSING TIMBER BRIDGE, GERMANY

 

A brief description is given of the design and construction of the Essing timber pedestrian bridge opened in September 1992 across the Rhein-Main-Donau Canal. With a maximum free span of 73m it is the first tension bridge of such a size which transforms 90% of the vertical loads into tension forces with only 10% acting as bending moments. A slim timber bridge was specified to fit in with the surroundings. Details are given of the materials used which include spruce, larch and a tropical hardwood. The bridge has the appearance of a sagging rope due to its geometry designed to transform vertical loads into tension forces. The extensive laboratory testing of the design including the use of the NASA programme NASTRAN is outlined. Prefabricated sections were joined on site without interruption using moveable glueing and pressing equipment in a tent.

 

[IanD]

1 hour ago, arbutus said:

A quick Google brings up this site

https://trid.trb.org/view/384852

 

THE ESSING TIMBER BRIDGE, GERMANY

 

A brief description is given of the design and construction of the Essing timber pedestrian bridge opened in September 1992 across the Rhein-Main-Donau Canal. With a maximum free span of 73m it is the first tension bridge of such a size which transforms 90% of the vertical loads into tension forces with only 10% acting as bending moments. A slim timber bridge was specified to fit in with the surroundings. Details are given of the materials used which include spruce, larch and a tropical hardwood. The bridge has the appearance of a sagging rope due to its geometry designed to transform vertical loads into tension forces. The extensive laboratory testing of the design including the use of the NASA programme NASTRAN is outlined. Prefabricated sections were joined on site without interruption using moveable glueing and pressing equipment in a tent.

 

 

Either way it's a lovely looking bridge 🙂

 

I hope they made the end anchors deep enough, going to be quite a lot of tension. Probably not as much as the Millennium (aka Wobbly) Bridge which is a similar (low-rise tension structure) concept but with steel tension cables, and which famously went "boing wobble" because nobody analysed it properly for undamped torsional resonance -- which came as a surprise to all us engineering students who were showed the famous film of the Tacoma Narrows Bridge (Galloping Gertie) in our lectures... 😉

[Ken X]

Nice piece of design work. Would like to have a look at the drawings. Guess it was tensioned after building to raise the centre span but could be wrong.

Funny thing tension, we used to show a bicycle to prospective employees and ask them to explain the load condition of the front wheel spokes. A lot of people with engineering degrees would say the top spokes were in tension and the bottom ones were in compression. 😳

[IanD]

1 minute ago, Ken X said:

Nice piece of design work. Would like to have a look at the drawings. Guess it was tensioned after building to raise the centre span but could be wrong.

Funny thing tension, we used to show a bicycle to prospective employees and ask them to explain the load condition of the front wheel spokes. A lot of people with engineering degrees would say the top spokes were in tension and the bottom ones were in compression. 😳

 

They weren't very good engineers then... 😉

[magnetman]

19 hours ago, Pluto said:

, at Essing, on the Rhine-Main-Donau Canal...

It is the world's only bridge using wooden beams in tension, and is called the Tatzlwurm....

 

That is a bold claim. 

I think there might be a sheep bridge somewhere with this design but perhaps not all that well known.

[Tim Lewis]

From Facebook

 

 

[Bod]

2 hours ago, Ken X said:

Nice piece of design work. Would like to have a look at the drawings. Guess it was tensioned after building to raise the centre span but could be wrong.

Funny thing tension, we used to show a bicycle to prospective employees and ask them to explain the load condition of the front wheel spokes. A lot of people with engineering degrees would say the top spokes were in tension and the bottom ones were in compression. 😳

All in tension?

 

Bod

[tree monkey]

2 hours ago, Ken X said:

Nice piece of design work. Would like to have a look at the drawings. Guess it was tensioned after building to raise the centre span but could be wrong.

Funny thing tension, we used to show a bicycle to prospective employees and ask them to explain the load condition of the front wheel spokes. A lot of people with engineering degrees would say the top spokes were in tension and the bottom ones were in compression. 😳

Can you explain the bike wheel thing to a none engineer?

[IanD]

13 minutes ago, Bod said:

All in tension?

 

Bod

Yes, unless the spoke tension is *far* too low or the rider is *far* too heavy... 😉

 

11 minutes ago, tree monkey said:

Can you explain the bike wheel thing to a none engineer?

Each spoke has typically 100kg or so of tension, which is why they go "ping".

 

Assume a wheel has 32 spokes, and to simplify things split them into 8 "top", 16 "side", and 8 "bottom".

 

With no rider on the bike, all the  spokes have 100kg of tension in them, which is what keeps the wheel rigid.

 

Even with a 400kg rider (!!!) over one wheel the top spoke tension would only increase by 25kg/spoke to 125kg/spoke (200kg "pulling up") and the bottom spoke tension would decrease by 25kg/spoke to 75kg/spoke (200kg less "pulling down").

Edited March 21, 2023 by IanD

[tree monkey]

12 minutes ago, IanD said:

Yes, unless the spoke tension is *far* too low or the rider is *far* too heavy... 😉

 

Each spoke has typically 100kg or so of tension, which is why they go "ping".

 

Assume a wheel has 32 spokes, and to simplify things split them into 8 "top", 16 "side", and 8 "bottom".

 

With no rider on the bike, all the  spokes have 100kg of tension in them, which is what keeps the wheel rigid.

 

Even with a 400kg rider (!!!) over one wheel the top spoke tension would only increase by 25kg/spoke to 125kg/spoke (200kg "pulling up") and the bottom spoke tension would decrease by 25kg/spoke to 75kg/spoke (200kg less "pulling down").

So under load there's a reduction in tension on the bottom spokes rather than any compression 

[IanD]

4 minutes ago, tree monkey said:

So under load there's a reduction in tension on the bottom spokes rather than any compression 

 

Correct. Unless the load is *really* heavy -- for this to happen with the numbers I gave and 2 wheels, the rider would have to weigh about 3 tons to reduce the lower spoke tension to zero.

 

Which will never happen, the wheel will buckle and collapse long before this...<sproing> 😞

Edited March 21, 2023 by IanD

[Paul C]

35 minutes ago, Bod said:

All in tension?

 

Bod

 

I don't think it was the intention for it to fall into the canal.

[Ken X]

Sorry all, had to pop out for a bit.

 

IanD has it spot on. 

 

We had great fun with our technical interviews.  The bicycle is a seemingly simple beast but covers all sorts of interesting engineering points and plonking one on the desk and pointing to bits like the spokes soon sorted out the practical engineers from the theoretical.

The forks, (why are they angled forwards and what loads do they see, particularly during braking?)  The frame and its loads, gearing, crank angles etc.  Let alone the materials used and why?  I thoroughly recommend a bike as an interview tool.🙂