At best, Hammersmith bridge is likely to be closed for 6 years.

[David Mack]

21 minutes ago, Murflynn said:

 

this suggestion will work as a temporary measure - it basically involves building a conventional Bailey Bridge (think - army, temporary) spanning between the existing foundations of the towers and the landfalls.  https://www.constructionenquirer.com/2020/11/30/double-decker-temporary-fix-for-hammersmith-bridge/

With the temporary truss in place the bridge can reopen for vehicles and pedestrians, but as long as the original bridge structure remains in place around (and particularly below) the truss it is unlikely to be safe enough to reopen for river traffic.

[robtheplod]

Its quite amazing that a London bridge could get so bad that boats are even stopped from going underneath. They must think it could just collapse?

[David Mack]

7 minutes ago, robtheplod said:

Its quite amazing that a London bridge could get so bad that boats are even stopped from going underneath. They must think it could just collapse?

Indeed they do. Cracks were found in the cast iron plinths at the ends of the bridge some years ago and have been monitored ever since, hence closing the bridge to vehicles. Last summer the cracks were found to have grown quite significantly in a short period of time. This led to the closure to pedestrians and river traffic.

[ditchcrawler]

I can see how poking a bridge though the middle to carry the traffic would work for cars, but if the main structure is in danger of falling into the river with no traffic flowing over it how a tubular bridge is going to stop that,

[Murflynn]

31 minutes ago, ditchcrawler said:

I can see how poking a bridge though the middle to carry the traffic would work for cars, but if the main structure is in danger of falling into the river with no traffic flowing over it how a tubular bridge is going to stop that,

 

it won't but the main impact of the closure is disruption of a main road artery from West London to the southwest.

 

it's not a tubular bridge, it's a multiple panel Bailey bridge based on double or triple deep steel truss beams.

[ditchcrawler]

1 hour ago, Murflynn said:

 

it won't but the main impact of the closure is disruption of a main road artery from West London to the southwest.

 

it's not a tubular bridge, it's a multiple panel Bailey bridge based on double or triple deep steel truss beams.

Do you think that will support the weight of the bridge if it falls down. 

[Scholar Gypsy]

1 hour ago, ditchcrawler said:

Do you think that will support the weight of the bridge if it falls down. 

 The plan is that it will support the weight of the current bridge, as the chains and bearings will need to be removed for maintenance etc. 

 

There's a nice description of what is going on (including the way Bazalgette bodged the orginal design) in the Aecom report here. It's the sideways (shear) force on the pedestal that creates the risk of sudden failure. 

https://www.gov.uk/government/publications/hammersmith-bridge-engineering-reports

 

 

[TheBiscuits]

Can we not get an anti-vaxx protest to march in step across it?  That should reopen the river to navigation once the debris has been salvaged ....

[bizzard]

Plonk a load of horrid enormous prestige cars and 4X4's on it and run for it quick.

[Murflynn]

In olden days when a busload of troops crossed the Clifton Bridge the passengers were ordered off the bus and told to march across but not to keep in step with each other.   Keeping in step would set the bridge into resonant wobbling and would weaken it.    Having spent 5 years in the CCF, I found that immensely difficult.  

[Detling]

The low slung bridge outside Tate modern proved that if the bridge vibrated at a frequency near peoples walking footfall then everybody would alter their pace to naturally fall in sync with that frequency, making the wobbly greater hence eventually ever one is in sequence.  They had to change its resonance frequency to solve that one. 

[Alan de Enfield]

 

I remember a particular Physics lesson at school.

 

The subject was 'vibrations, harmonics and aeroelastic flutter'

 

 

 

 

[Hudds Lad]

you should never walk rhythmically as it attracts the big sandworms  

[Tim Lewis]

One solution ?

[Jen-in-Wellies]

If it does collapse, it will be a prime spot for magnet fishing. Hey. I've got another girder!

[Tacet]

[Scholar Gypsy]

1 hour ago, Alan de Enfield said:

 

I remember a particular Physics lesson at school.

 

The subject was 'vibrations, harmonics and aeroelastic flutter'

 

 

 

 

The film we had at school had a line in the commentary something like this:

 

"Note the engineer, who is sensibly walking along the nodal line, rather than the antinode."

[Tacet]

12 hours ago, Scholar Gypsy said:

 The plan is that it will support the weight of the current bridge, as the chains and bearings will need to be removed for maintenance etc. 

 

There's a nice description of what is going on (including the way Bazalgette bodged the orginal design) in the Aecom report here. It's the sideways (shear) force on the pedestal that creates the risk of sudden failure. 

https://www.gov.uk/government/publications/hammersmith-bridge-engineering-reports

 

 

Poor design, by Bazalgette as he failed to use maintenance-free roller bearings such that after only 100 years or so they seized.  Nothing was done (of course) when it was noticed that they rollers weren't free and after only another 30 years there are all sorts of problems.

 

Same with his sewers; he failed to allow for a population growth from around 2.5m to approaching 10m.

 

[Scholar Gypsy]

2 hours ago, Tacet said:

Poor design, by Bazalgette as he failed to use maintenance-free roller bearings such that after only 100 years or so they seized.  Nothing was done (of course) when it was noticed that they rollers weren't free and after only another 30 years there are all sorts of problems.

 

Same with his sewers; he failed to allow for a population growth from around 2.5m to approaching 10m.

 

The bodge was that the bearings were needed at all, to get around the foundations of the old bridge. 

 

To be fair the sewers are coping fine,  tthe issue is STW capacity and problems with storm water and concrete rather than grass. 

 

Did you see the excellent recent bbc documentary on the science of sewage? Good shots of Minworth STW....

[ditchcrawler]

16 minutes ago, Scholar Gypsy said:

 

 

Did you see the excellent recent bbc documentary on the science of sewage? Good shots of Minworth STW....

Is that an opener for Composting Loos

 

[Scholar Gypsy]

6 minutes ago, ditchcrawler said:

Is that an opener for Composting Loos

 

Yes there is an interesting section on composting toilets.

Edited April 6, 2021 by Scholar Gypsy

[Alan de Enfield]

2 hours ago, ditchcrawler said:

Is that an opener for Composting Loos

 

 

Are they not called seats and lids, as with conventional toilets ?

[cuthound]

I'm surprised Boris hasn't suggested replacing Hammersmith Bridge with a tunnel.

 

It could be a prototype for his tunnel to Northern Ireland, just like Newbold Tunnel was a prototype for the Netberton Tunnel. ?

[IanD]

7 hours ago, Tacet said:

We danced across Hammersmith Bridge when doing a 10k Morris dance for charity, and as the musician walking along I can tell you that at a particular point about 3/4 of the way across the span the whole walkway started to bounce up and down noticeably...

[cuthound]

18 minutes ago, IanD said:

We danced across Hammersmith Bridge when doing a 10k Morris dance for charity, and as the musician walking along I can tell you that at a particular point about 3/4 of the way across the span the whole walkway started to bounce up and down noticeably...

 

Sssh, they will send you the repair bill! ??