Cannon Place – Cannon Street London
June 5th, 2010
This has been a difficult week trying to identify an appropriate item about housing to highlight. Watching the emails come in with different items of building news. There was the intriguing and fascinating Cannon Street cantilever . . .
Click the picture above to see the full design
Finding somewhere to lay the foundations for an office block above London’s Cannon Street station proved so difficult, the engineers had to call on the structural principles of the Forth Bridge to get the job done
https://www.building.co.uk/technical/support-act-cannon-place/5000302.article
. . . which I went to see on Thursday 3rd June. It’s a fascinating sight, photo in due course I hope. However it’s not housing, that’s why this article is filed under Thoughts.
What the builders have done is to cantilever the two end sections off two piled foundations (avoiding the railway beneath) that are under the small X shaped supporting beams in the picture above just above the ground. The reference to the Forth Bridge is because if you look at a photograph of that bridge then you can see that the bridge has four piers beneath each span that support the steelwork above.
In the case of Cannon Street the structure has two longitudinal supporting structures and the flanking offices are supported by cables from the top while the floors are put in. When the steelwork is complete the cables will be removed and the frame will then be balanced and supported with the loads transferred through the giant steel X frames visible in the picture to the foundations in the centre. At the moment (11/6/2010) the entire structure is visible as a work in progress and the mechanics involved are obvious. This will be less obvious by the time of completion so now is a good time to go.
UPDATE: I went to have a look, this time with a camera, on Wednesday 16th June 2010 and these are the results.
Click the photo for a larger image
Here you can clearly see the cable stays holding the structure in place while the floors are added.
Click the photo for a larger image
Here the cable stays are more clearly visible.
Click the photo for a larger image
Above is shown the giant X supporting steel frame that transers the load from the two longitudinal piled foundations to the cantilevered arms presently cable supported to the right of the photograph.
UPDATE: I went back to have a look on Wednesday 24th August 2011 and these are the results.
I had to tilt the camera to get the three brackets in the shot. I did try a horizontal shot but it clipped the frames. When you compare the shot above with the earlier ones you can see how the builders have used the same type of frame as in the centre, to transfer the load of the office floors to the central frame, it is obvious which part of the frame is in compression and which under tension.
The new facade. To my eye it looks very elegant and ties in with the older but similar building to the left which also displays its structure on the outside.
The North West frame at the junction of Dowgate Hill and Cannon Street.
The Southernmost frame on Dowgate Hill transferring the floor loads back to the small frame partly hidden at the bottom of the photo.
If you look just above the wall in the above photograph there may be seen the two protruding wings of one of two cross frames that sit on the piles that support the building and transfer the loads from above down to the ground. There is an equivalent cross frame on the other side of the railway lines.
Entrance from opposite College Street cleverly designed to form an “end stop” when viewed by anybody approaching from that direction as below.
The view along Cloak Lane below.
Empty?
They include Cannon Place, which does not have a single tenant, although the developer said negotiations are ongoing.
VIDEO
I find it odd that nowhere in their examples does the Forth Bridge figure since it alone is the clearest example of a cantilevered structure.
On YouTube here:-