Pile cap design for single H-pile refer( thread507-158100) and others
Pile cap design for single H-pile refer( thread507-158100) and others
(OP)
I need to design a pile cap for a single h-pile supporting a steel bridge column.
Seems like all the load from the column will be transferred to the pile below (pile located directly below column).
Since the cap will not take any loads, can I just design a small (say 3ft by 3ft and 24 in thickness) cap with minimum reinforcement top and bottom.
H-pile is HP 14x73. I was planning to embed the pile 6 inches into pile cap.
Since I am not very familiar with such design, your feedback would be very helpful.
Thanks.
Seems like all the load from the column will be transferred to the pile below (pile located directly below column).
Since the cap will not take any loads, can I just design a small (say 3ft by 3ft and 24 in thickness) cap with minimum reinforcement top and bottom.
H-pile is HP 14x73. I was planning to embed the pile 6 inches into pile cap.
Since I am not very familiar with such design, your feedback would be very helpful.
Thanks.






RE: Pile cap design for single H-pile refer( thread507-158100) and others
RE: Pile cap design for single H-pile refer( thread507-158100) and others
Contractor can be out by 2-3 inches. Any references on how to design this?
RE: Pile cap design for single H-pile refer( thread507-158100) and others
RE: Pile cap design for single H-pile refer( thread507-158100) and others
Perhaps you could consider the following as an alternative:
1. Drive the H-Pile and cut it off near ground level.
2. Weld the bottom of the column to the top of the H-Pile.
3. Form and place a reinforced concrete "collar" around the welded joint to protect the weld from weather and to LOOK like a pile cap.
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RE: Pile cap design for single H-pile refer( thread507-158100) and others
RE: Pile cap design for single H-pile refer( thread507-158100) and others
Mike McCann
MMC Engineering
RE: Pile cap design for single H-pile refer( thread507-158100) and others
RE: Pile cap design for single H-pile refer( thread507-158100) and others
I would never use a single pile cap that was not tied to a grade beam.
Mike McCann
MMC Engineering
RE: Pile cap design for single H-pile refer( thread507-158100) and others
I'd probably feel uncomfortable using a single pile (except possibly for monopole construction, but that's a special case) if normal operation/service loads put the resultant force outside the cross section of the pile even if the numbers worked. I'd be concerned about long term settling releasing some of that lateral restraint on the piles. Short term loads I'd be less concerned about. Also, you may not be allowed to use them without grade beams depending on your code and seismics in the area.
For actual design, just draw your free body diagrams at your critical sections and locations.
- Check anchorage of your column into the cap
- Make sure your cap can transfer the forces between the column and the pile. Either treat it as a column, a beam, a combination of the two or strut and tie depending on the situation. I've never really seen much that addresses this specific issue, but you can use a lot of the same concepts you'd use for a column pedastal so looking up design guides for that would likely be a good plan.
- Check anchorage of your pile into the cap
But first make sure your assumptions actually make sense. If you're transferring moment into the pile and it's a single pile cap you really have to make sure that your structure is relatively flexible in comparison to the pile including the geotechnical side or that you've actually modeled the whole system including foundation springs and things. Depending on the framing on top, you could easily have a structure that's an order of magnitude stiffer than the foundation. In that case, regardless of whether you design the piles to take that moment capacity, the connection will only be partially fixed. If that's true, you may be underdesigning your superstructure based on the assumption of a fixed cap.
While a direct welded connection is preferred from the engineering side of things, there are reasons to avoid it depending on the conditions you've got. It can be crappy for making fitup work, especially when you're talking about a single column on a single steel pile. You tend to have to screw around a lot on the welds and they're generally in terrible weld positions. Compression primary loads aren't terrible, because you can shim but if it's a reasonably significant moment connection or there's uplift, it can get ugly.
RE: Pile cap design for single H-pile refer( thread507-158100) and others
Decided to go with 2 pile. Didn't feel like trying something different :)