Why do they?.........Q & A thread

[Bentley Bullet]

Why do they show signs saying 'weak bridge' on a weak bridge? What are you supposed to do to ensure you cross it as safely as possible? Do you tip-toe if walking, or raise your backside off the car seat if you're driving?

Also, why do they put great big concrete slabs on a weak bridge? Surely these are heavier than a bridge full of cars?

Sensible answers only please!

[Dutch Uncle]

And another one

Why do people say 'cheap at half the price'?

The fact that if it were half the price it might be cheap says nothing at all about the value at its full price.

BB - I presume the concrete slabs are each individually longer than the span of the bridge concerned? That might make sense if only the middle was weak.

[Bentley Bullet]

That's a good one DU, and very true. Don't know the answer though!

Going back to the OP, I'm hoping BST will provide an answer because I believe it is his field of expertise. In return I'll try to  answer his football queries because it's obvious that is where my superiority lies between us.



PS. Only pulling your leg BST......I'd be interested to know the answer though.

[Bentley Bullet]

And another one

Why do people say 'cheap at half the price'?

The fact that if it were half the price it might be cheap says nothing at all about the value at its full price.

BB - I presume the concrete slabs are each individually longer than the span of the bridge concerned? That might make sense if only the middle was weak.

DU, no there are several of them about say 10ft long lined up end to end along the whole length of the bridge.

[BillyStubbsTears]

BB. Go on then, you've hooked me.

Depending on the road type, the design
loading for the bridge will be about 1tonne for every foot length of the bridge, for every carriageway. That is far bigger a load than the concrete blocks will be ( to have a weight of 1tonne per foot length, concrete blocks would need to be about 4 foot square in cross section).

So the blocks are put down to reduce a dual carriageway to a single lane and hence reduce the potential load that might be placed on the bridge if the worst traffic occurred. Or, sometimes blocks are placed to reduce the width of the carriageway so that big 40t wagons can't get onto the bridge.

The "weak bridge" signs are put there to explain why the carriageway has been restricted in width.

[Donnywolf]

ok ... the tenuous link with my post is its about Bridges !

I saw this photo a few months ago and it needs no caption

[Bentley Bullet]

BB. Go on then, you've hooked me.

Depending on the road type, the design
loading for the bridge will be about 1tonne for every foot length of the bridge, for every carriageway. That is far bigger a load than the concrete blocks will be ( to have a weight of 1tonne per foot length, concrete blocks would need to be about 4 foot square in cross section).

So the blocks are put down to reduce a dual carriageway to a single lane and hence reduce the potential load that might be placed on the bridge if the worst traffic occurred. Or, sometimes blocks are placed to reduce the width of the carriageway so that big 40t wagons can't get onto the bridge.

The "weak bridge" signs are put there to explain why the carriageway has been restricted in width.

Thank you BST

[Bentley Bullet]

Why do people like quizzes, but hate exams?

[Wild Rover]

Perhaps the "Barriers" are made with Lytag ( Light Aggregate ) giving a density of say 1.4 tonnes /m3 as opposed to "Normal Aggregate" which gives a density of 2.3, and as the barriers will contain say 3 mts /3 that's 4.2 T/m3 as opposed to 7 ( or thereabouts ).

Mind you, I only know of 1 weak bridge and that has entrance barriers, not delineator barriers, so maybe I am talking b*llocks.

[Bentley Bullet]

The weak bridge I referred to is the one near Tesco at the bottom of North Bridge, over the Don canal towards the Greyfriers car park.

[Wild Rover]

Not seen that, in fact cant say I have been in that area for 25 years. My weak bridge is "Jubilee Bridge ( Thorne - Fishlake ).

[RoversDave]

The weak bridge I referred to is the one near Tesco at the bottom of North Bridge, over the Don canal towards the Greyfriers car park.
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The weak bridge I referred to is the one near Tesco at the bottom of North Bridge, over the Don canal towards the Greyfriers car park.

Mmm, Greyfriars bridge?