The Colombo skyline is littered with tower cranes, and a few days ago I had the opportunity to witness something I had heard about but never previously seen; how they grow taller as the building they are helping to construct also grows taller.

This is done by having a sleeve operated by hydraulic rams lift the tower above it higher whilst a new section of the tower that the crane has already lifted up is inserted.  The rams are then relaxed to allow the newly inserted section to take the compression load, whereupon it is pinned in place.  The sleeve then climbs higher and the process is repeated.

Two things that struck me; the first of these is the simple approach of welded plate and pin to hold things in place.  Just think of the bending moments that the tower is exposed to.  Click on the third image to expand it and you will understand what I mean; look carefully and you will see the plates and pins that hold the sections to each other.  Nothing else.

The second thing was when watching this eighty one seconds video of what I have just described, how much the tower rocks in the process.  I don’t think I’d like to be a crane operator even on a still day!

If you have ten minutes more to spare, also watch this video that brings insight to the huge amount of effort that goes in to even preparing a crane for erection – and in this case, then building it via another huge crane.

Steve