Why does the Tees/Middlesbrough transporter bridge have a notch in the
middle?

https://upload.wikimedia.org/wikiped...ton_side.jp g

Seems to me it's got to be weaker than if it was braced across the gap.

Tim

Tim+ wrote

Why does the Tees/Middlesbrough transporter bridge have a notch in the
middle?

Because each side is essentially a self supporting cantilever on its
tower and so the join in the middle isn't taking any load at all.

https://upload.wikimedia.org/wikiped...ton_side.jp g

Seems to me it's got to be weaker than if it was braced across the gap.

See above.

On 07/04/2016 21:05, Rod Speed wrote:


Tim+ wrote

Why does the Tees/Middlesbrough transporter bridge have a notch in the
middle?

Because each side is essentially a self supporting cantilever on its
tower and so the join in the middle isn't taking any load at all.
It must do because the track has to be continuous, and as the trolley
thing moves towards the middle the cantilever will bend a bit so it will
have to pull the other one down with it. But I suppose your basic point
is correct, in that one cantilever alone, if it had no physical
connection with the other one, would be able to take the strain.

Bill

Bill Wright wrote
Rod Speed wrote
Tim+ wrote

Why does the Tees/Middlesbrough transporter bridge have a notch in the
middle?

Because each side is essentially a self supporting cantilever on its
tower and so the join in the middle isn't taking any load at all.

It must do because the track has to be continuous, and as the trolley
thing moves towards the middle the cantilever will bend a bit so it will
have to pull the other one down with it.

No, because the cantilever ensures that it doesnt bend enough to matter.

All the bit in the middle needs to do is to keep the two ends
that meet there aligned so that what is running on the rails
doesnt see a displacement where the ends touch.

But I suppose your basic point is correct, in that one cantilever alone,
if it had no physical connection with the other one, would be able to take
the strain.

And you can see the cables to the ground at the extreme
outer ends of the horizontal section that does the cantilever.

On 07/04/2016 19:37, Tim+ wrote:
Why does the Tees/Middlesbrough transporter bridge have a notch in the
middle?

https://upload.wikimedia.org/wikiped...ton_side.jp g

Seems to me it's got to be weaker than if it was braced across the gap.

The two halves are designed to be self supporting - they could take the
full weight of the car in cantilever, without the other side being
there. Hence you only need "enough" of a join to stop the ends wobbling
next to each other - there is no structural need for a stonger joint.



--
Cheers,

John.

/================================================== ===============\
| Internode Ltd - http://www.internode.co.uk |
|-----------------------------------------------------------------|
| John Rumm - john(at)internode(dot)co(dot)uk |
\================================================= ================/

John Rumm wrote:
On 07/04/2016 19:37, Tim+ wrote:
Why does the Tees/Middlesbrough transporter bridge have a notch in the
middle?

https://upload.wikimedia.org/wikiped...ton_side.jp g

Seems to me it's got to be weaker than if it was braced across the gap.

The two halves are designed to be self supporting - they could take the
full weight of the car in cantilever, without the other side being
there. Hence you only need "enough" of a join to stop the ends wobbling
next to each other - there is no structural need for a stonger joint.




Well yes but materials flex and stretch. When the gondola is in the middle
the counterbracing cables will obviously minimise droop, but not eliminate
it. Fully triangulating the top beam would surely help to reduce and
droop.

So, perhaps more to the point, why would one choose to NOT use a fully
triangulated beam? There are many similar (but not identical) designs of
transporter bridge but this is the only one with a "notch".

Tim

On 08/04/16 01:01, John Rumm wrote:
On 07/04/2016 19:37, Tim+ wrote:
Why does the Tees/Middlesbrough transporter bridge have a notch in the
middle?

https://upload.wikimedia.org/wikiped...ton_side.jp g


Seems to me it's got to be weaker than if it was braced across the gap.

The two halves are designed to be self supporting - they could take the
full weight of the car in cantilever, without the other side being
there. Hence you only need "enough" of a join to stop the ends wobbling
next to each other - there is no structural need for a stonger joint.




The University pf York has/had a footbridge like this between Wentworth
and Goodricke Colleges (as were - there's been a bit of a relocating of
some of the names since).

It was considered a sport to jump up and down on the middle at resonant
frequency

On 08/04/2016 06:57, Tim+ wrote:
John Rumm wrote:
On 07/04/2016 19:37, Tim+ wrote:
Why does the Tees/Middlesbrough transporter bridge have a notch in the
middle?
https://upload.wikimedia.org/wikiped...ton_side.jp g
Seems to me it's got to be weaker than if it was braced across the gap.
The two halves are designed to be self supporting - they could take the
full weight of the car in cantilever, without the other side being
there. Hence you only need "enough" of a join to stop the ends wobbling
next to each other - there is no structural need for a stonger joint.
Well yes but materials flex and stretch. When the gondola is in the middle
the counterbracing cables will obviously minimise droop, but not eliminate
it. Fully triangulating the top beam would surely help to reduce and
droop.
So, perhaps more to the point, why would one choose to NOT use a fully
triangulated beam? There are many similar (but not identical) designs of
transporter bridge but this is the only one with a "notch".

There is no need to entirely eliminate any flex; witness 'boinging' wind
loads, earthquake resistance, etc,etc .

There is no (or at least minimal) structure in the middle as it would
weigh more and so need more structure so would weigh more....

Nowadays a computer could work out the optimal structure but 'in those
days' some 'architect' drew it and said "that looks right" with some
'back of envelope calculations' a construction master would say "nope
needs to be stronger here and here can be thinner here and here" they
would settle on something that looked right but was thin enough to work
used as little material as possible to minimise costs. They didn't
always get it right and some times they went completely overboard
(witness the Forth bridge built just after the 'Tay bridge disaster' and
so well 'over engineered'.

Tim+ wrote
John Rumm wrote
Tim+ wrote

Why does the Tees/Middlesbrough transporter bridge have a notch in the
middle?

https://upload.wikimedia.org/wikiped...ton_side.jp g

Seems to me it's got to be weaker than if it was braced across the gap.

The two halves are designed to be self supporting - they could take the
full weight of the car in cantilever, without the other side being there.
Hence you only need "enough" of a join to stop the ends wobbling
next to each other - there is no structural need for a stonger joint.

Well yes but materials flex and stretch. When the gondola is in the middle
the
counterbracing cables will obviously minimise droop, but not eliminate it.

That's why the two halves are joined, so there never is a gap.

Fully triangulating the top beam would surely help to reduce and droop.

It wouldn't in fact make any difference when the two halves are joined.
Doesn't matter if the center does drop a bit, its not enough to matter.

So, perhaps more to the point, why would one
choose to NOT use a fully triangulated beam?

Because in that case the cantilevered approach works fine.

There are many similar (but not identical) designs of transporter bridge

Very few or none have those cables to the ground at the extreme ends.

but this is the only one with a "notch".

Because it is the only one with those cables to the ground at the end.

On 07/04/2016 19:37, Tim+ wrote:
Why does the Tees/Middlesbrough transporter bridge have a notch in the
middle?

https://upload.wikimedia.org/wikiped...ton_side.jp g

Seems to me it's got to be weaker than if it was braced across the gap.

Tim

It looks like the two halves could swing upwards to allow very tall
vessels through.

Cheers
--
Syd

"Tim+" wrote in message
...
Why does the Tees/Middlesbrough transporter bridge have a notch in the
middle?

https://upload.wikimedia.org/wikiped...ton_side.jp g

Seems to me it's got to be weaker than if it was braced across the gap.

Well anyway, if it collapses it's in Arizona now

Chris Hogg wrote
Rod Speed wrote
Tim+ wrote
John Rumm wrote
Tim+ wrote

Why does the Tees/Middlesbrough transporter
bridge have a notch in the middle?

https://upload.wikimedia.org/wikiped...ton_side.jp g

Seems to me it's got to be weaker than if it was braced across the
gap.

The two halves are designed to be self supporting - they could take the
full weight of the car in cantilever, without the other side being
there.
Hence you only need "enough" of a join to stop the ends wobbling
next to each other - there is no structural need for a stonger joint.

Well yes but materials flex and stretch. When the gondola is in the
middle
the counterbracing cables will obviously minimise droop, but not
eliminate it.

That's why the two halves are joined, so there never is a gap.

Fully triangulating the top beam would surely help to reduce and droop.

It wouldn't in fact make any difference when the two halves are joined.
Doesn't matter if the center does drop a bit, its not enough to matter.

So, perhaps more to the point, why would one
choose to NOT use a fully triangulated beam?

Because in that case the cantilevered approach works fine.

There are many similar (but not identical) designs of transporter bridge

Very few or none have those cables to the ground at the extreme ends.

but this is the only one with a "notch".

Because it is the only one with those cables to the ground at the end.

A few other transporter bridges were built with a cantilever design,
notably those at Marseilles http://tinyurl.com/gwq2xc5 and at Nantes
http://tinyurl.com/gnrvq8q ,

Sure, but neither of those used the same approach
with the horizontal section, being cable stayed.

both now demolished. Both had a separate small central
span, much like the central spans on the iconic Forth rail
bridge (also a cantilever design), but they relied on cable-
staying to support the cantilever rather than a girder design.

Precisely.

Most other transporter bridges seemed to rely on a suspension-type
design, with suspension cables running between the supporting towers
and anchored some distance behind them, much like the now-demolished
Runcorn transporter bridge http://tinyurl.com/zoh36st .

Lots of images of UK transporter bridges, past and present, here
http://tinyurl.com/hlm93z3

Yeah, the whole approach isnt really that viable compared
with a conventional bridge and only really needed where
you needed to allow very tall sailing ships to pass underneath
and not that much volume moving across the river.

On 07 Apr 2016, "Rod Speed" grunted:

Tim+ wrote

Why does the Tees/Middlesbrough transporter bridge have a notch in
the middle?

Because each side is essentially a self supporting cantilever on its
tower and so the join in the middle isn't taking any load at all.

Check out this design: http://tinyurl.com/hxvf5yo (or
http://www.mirror.co.uk/news/uk-news...-castle-death-
7616188)
.... there's actually a 4" gap i n the middle of the span


--
David

On 07/04/16 19:37, Tim+ wrote:
Why does the Tees/Middlesbrough transporter bridge have a notch in the
middle?

https://upload.wikimedia.org/wikiped...ton_side.jp g

Seems to me it's got to be weaker than if it was braced across the gap.

Tim

Never underestimate the 'because I did one like that last week and have
all the calculations done already' syndrome.

It looks like two standard land crane deigns joined in the middle

Darwin's law is not survival of the fittest, it's lack of survival of
the terminally dysfunctional. And that bridge is good enough, not optimal.

--
Outside of a dog, a book is a man's best friend. Inside of a dog it's
too dark to read.

Groucho Marx

On 08/04/2016 11:31, Lobster wrote:


Check out this design: http://tinyurl.com/hxvf5yo (or
http://www.mirror.co.uk/news/uk-news...-castle-death-
7616188)
... there's actually a 4" gap i n the middle of the span



I read last week "It will feature a 4in gap and will be just 7in wide at
its narrowest point when it is completed in 2019." and wondered how they
were going to square that with the Equality Act. That doesn't override
legislation which protects heritage buildings but a whole new bridge
which can't be used by users of wheelchairs, walkers etc???

--
Robin
reply-to address is (intended to be) valid

Lobster wrote
Rod Speed wrote
Tim+ wrote

Why does the Tees/Middlesbrough transporter bridge have a notch in the
middle?

Because each side is essentially a self supporting cantilever on its
tower and so the join in the middle isn't taking any load at all.

Check out this design: http://tinyurl.com/hxvf5yo (or
http://www.mirror.co.uk/news/uk-news...-castle-death-
7616188)
... there's actually a 4" gap i n the middle of the span

That's not a transporter bridge, it’s a suspension bridge.

On 08/04/2016 07:41, Tim Watts wrote:
The University pf York has/had a footbridge like this between Wentworth
and Goodricke Colleges (as were - there's been a bit of a relocating of
some of the names since).

It was considered a sport to jump up and down on the middle at resonant
frequency

It didn't do that when I was there...

Andy