underpinning help
underpinning help
(OP)
does anybody have a example drawing of underpinning panel supporting a footing for a large multi storey building.
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RE: underpinning help
In the first edition of "Foundation Engineering Handbook" by Wnterkorn and Fang (1975), chapter 22 discusses underpinning and has a lot of drawings and photographs. If you can find a copy of that, you're in luck.
RE: underpinning help
RE: underpinning help
RE: underpinning help
Thats an awesome photo.
Where was that done?
RE: underpinning help
Intrusion Prepakt /marineconcrete.com
RE: underpinning help
RE: underpinning help
The photo attached by Doc08 is indeed impressive, but I would not take that as a good example of underpinning. My judgment is that that scheme was unstable and dangerous.
RE: underpinning help
depends on the loads involved, I dont think we know enough about the specifics to make that sort of comment.
I understand what you are getting at though. A more adequate lateral bece at the concrete beam and a shorter unbraced length would probably be wiser.
But the numbers probably add up and I dont think this is a high seismic/wind zone.
RE: underpinning help
RE: underpinning help
What type of piles are those? the bottoms loke like mini piles, and the tops look like augercast
RE: underpinning help
I appreciate your opinion and always apreciate a good advise especially that each and everyone of us is prone to mistakes. However, and strictly from a professional point of view, judging the system as "unstable and dangerous" just by looking at one picture and without asking for more details /clarifications is on its own, "dangerous". For what it is worth, about 15 years ago, I had the toughest time convincing structural engineers we dealt with that micropiles are more than just "tooth picks" and they indeed can function as decent structural elements. We have performed load tests up to 100 tons, on 22cm micropiles, with excellent results.
Indeed the next quake is due, in which case my primary concern would be about the integrity of the existing structure more so than the installed underpinning system. We cannot just shy away from challenges and wait around for the next big quake to come or design every structure, even if temporary, for a quake measuring 6 or more on the Richter scale. None of our proposals would be feasible and we would be quickly out of work. We can however, do our homework, trust our experience, follow the currently acceptable codes, and exercise sound engineering judgement.
DRC1:
you are absolutely right, the system was indeed temporary although we did adopt some out of the ordinary measures given that the structure itself was quite old and the structural frame consisted of bearing walls and arches made of only sandstone blocks (without any reinforcement) which does not permit much differential settlement between supports oterwise the arches would come apart and we'd end up with a pile of rubble. The piles were 25cm in diameter, cast with cement grout providing about 40MPa strength. These piles were braced every 2.5m on the way down and embedded a minimum of 5m into the limestone rock. The underpining system was in service a total of 13 months while the new structure was underway. The maximum recorded differential settlement was 3mm.
Cheers.
RE: underpinning help