Name: 如何阻止巨大的橋樑腐蝕？ (How To Stop A Colossal Bridge Corroding)
Uploaded: 2021-01-14T12:28:00.000Z
Duration: 5 min 5 s
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- When it opened in 1981, the Humber Bridge

was the longest single-span suspension bridge in the world.

weighing 17,000 tonnes, held up by cables

that weigh thousands of tonnes themselves.

Those cables are made up of more than 14,000 individual wires,

all anchored into concrete foundations on the shore.

And those cables, and the whole structure in turn,

they're just a couple of centimetres further apart at the top

this bridge is about a third of the way through its design lifespan,

- Back in the '90s, in the United States,

severe cable corrosion in their early structures.

So, they were building suspension bridges in the '30s.

The way that the cables were designed to be kept watertight

the open wires were coated with lead paste,

around the outside of the cable, trapping the lead paste

and effectively keeping the cable watertight,

and it was thought that would be sufficient.

demonstrated that moisture was still penetrating

because, inside here was its own mini climate, in effect,

so it was affected by external temperatures,

- This is a brutal environment for the cables.

and down by the road there's engine exhaust and spray.

Remember, the cables aren't one sold piece of metal.

They're made up of thousands of individual wires.

they're cylinders, so there will always be a slight air gap between them,

cannot occur below 40% relative humidity.

there are plant rooms that produce dehumidified air.

That air is then pumped up to the main cable

and injected into a stainless steel sleeve

The relative humidity of the air blown into the cables

is low enough to have an affinity to collect moisture

drying the cable and exhausting the moisture to atmosphere,

and that is a continuous, 24-hour cycle, 365 days a year,

essentially for the rest of the bridge's life.

So, the Humber Bridge Board first inspected their main cables in 2009,

and then deployed dehumidification the following year, 2010.

reinspecting the main cable to ascertain the effectiveness

we drive the wedges in to form an open wedge in the cable.

From each wedge line, the consultant engineer

will select a wire, and then our guys will come along

and remove approximately a five-meter length

to then take the data that they need to collect from the cable.

We then select a five-meter length from the drum of the new wire

and splice that in with ferrules and then remove the wedges,

That is then repeated seven more times around the circumference of the cable,

and then that effectively is the inspection complete.

With 100-ton hydraulic jacks in each corner,

we compress the cable back to its original diameter.

- The idea that the wires are slightly corroded

could be worrying, but it's well, well within design tolerances,

and it's been noticed early and dealt with,

and they're keeping a watch on them just in case.

But bridges elsewhere in the world that aren't inspected,

where infrastructure isn't maintained, where cutbacks

Those should give you just a little cause for concern.

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如何阻止巨大的橋樑腐蝕？ (How To Stop A Colossal Bridge Corroding)

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