Sunday, 4 May 2008

The GE19 bridge push: Day 1

I was invited by TfL to use the official viewing galleries set up for this event, so I've had a very good view of the action.

I'll start with an overview of the site, taken from the east end:
This was taken around lunchtime after the bridge had been moved a fair distance, with the front dangling over the railway line.

While the wheels at the back are powered, the majority of the force comes from a pair of strand jacks:
These are basically just hydraulic rams that can pull themselves along cables. The two sets of cables are strung along underneath the bridge and anchored to the eastern abutment (ie they don't cross the railway line). The jacks should therefore roughly reach the end of the cable when the bridge is in its final position.

So that's the theory. Here's how it looked when I got there first thing:

The bridge had already been moved a significant distance, with the west end of the bridge proper (the brown bit) resting on the eastern abutment. The grey bit is a temporary extension and will be cut off and scrapped.

During the morning they moved it much further:

They then took a break to add a whole load of counterweights (kentledge) to the back. It started moving again:

With the tip of the bridge looming very close they started lubricated the western abutment:
The bridge is sliding on flat pads, with no bearings, though the pads are free to pivot front to back.

A short while later, the tip of the extension was hovering right over the pads:

This next bit surprised me. They were able to jack up the back of the bridge, tilting the opposite end down onto the pads:
Note that the left side touched down before the right. This caused a view anguished faces in the viewing gallery. It doesn't seem to have been a real problem, though they were briefly seen holding an ordinary builder's spirit level up against it.

They moved it a couple of feet further packing up:

I think they're now repositioning the counterweights. At time of writing it hasn't moved again, though you can watch the live webcam and be the first to know.

Thanks again to TfL for the invite.


Anonymous said...

Congratulations - super pictures I do hope you are saving them for your definitive book on the rebuilding of the railway.Have aword with Capital Transport Publishing -just their sort of "track-lit". You have also become part of the establishment with access to the official viewing area. It all seems to be going well. Any idea when the possession on the National Rail lines into Liverpool Street is due to end

Anonymous said...

Am I right in thinking there will be another separate bridge over Brick Lane - standing on that concrete pillar in the foreground?