Pile Cap STM
Pile Cap STM
(OP)
I'm currently working on the design for the cast in place bulkhead on top of a steel sheet pile. To resist the rather significant lateral loads, battered precast piles are being placed every 5 ft. I'm trying to check the design with a STM, essentially treating it as a sort of vertical concrete corbel. But I'm having trouble resolving the forces in a way that makes any sense - right now I have sort of a lonely tie force that I can't seem to pair up, and other force breakdowns I've played with give me similar problems. What exactly am I missing here?






RE: Pile Cap STM
1. The horizontal soil pressure is resisted by the horizontal component of the concrete pile compression.
2. The vertical component of concrete pile compression is resisted by vertical tension in the steel sheet pile. In other words, if the steel pile can't resist extraction, they will move upward, out of the ground. As the sheet pile wall collapses towards the left, it will tend to rotate the concrete pile counterclockwise.
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RE: Pile Cap STM
I've discussed it with another engineer, who's of the opinion that typically for battered piles that so long as your centerline intersection occurs within the pile cap, the cap is "ok" and you just need to check the possible failure surfaces/planes. Which makes a certain amount of sense. But I'd still feel better if I could cash it out in terms of struts and ties.
RE: Pile Cap STM
1) A moment at the top of the precast piles.
2) A moment at the top of the sheet piles.
3) Both #1 and #2 in some measure.
I've told one version of this story in STM below. It would seem to have rather important implications for:
1) The extension of the sheet pile into the cap.
2) The design of the precast piles.
3) The design of the cap connection to the precast piles.
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