Monday, 16 May 2011

Destroying LOFAR — Collapse!

Firstly, we'll start this report with a quick apology for all of those who have been sitting clicking 'refresh' on their browsers for the last couple of days. There have been some technical problems with the web log provider, which have caused some delays in posting the next reports on the LOFAR destruction tests.

However...

When we last left our heroes, they have piled over seven-and-a-half tonnes of icy snow on the raised HBA tile. An ominous crack had been heard and the digger engine was shut off and the team started checking the tile, noting some deformation under one of the cells.

Then, we started hearing clicks and creaks. As the gentle movement of Arctic air played over the mound of ice, the creaking would intensify and then subside. It genuinely sounded like being on an old sailing ship, with its wooden hull and masts flexing in the swell and breeze.

And then, the clicks and snaps and pops and creaks started to pick up pace and with a rush of noise that sounded like a tree being felled, there was splintering sound a sudden crash and most of the tile (and the snow on it) dropped down 20cm or so.

Part of the tile edge, showing the crushed tile.

The tile label and one of the anchor points. As the tile
did not fall through completely, no anchors broke.


As can be seen in this last image, the south-west side seems
to have remained partially intact. This is was, of course,
where the pile of snow was the thinnest, and also on the
opposite side of where the digger was dumping the snow.



What needs to be done now is to carefully clear the snow off the tile and then systematically dismantle the remains. What we want to do is look for not only the extent of the damage, but also the failure modes that triggered during the final milliseconds of this tile's life.

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