Attached is a typical steel pile/concrete pile cap section detail we use. Pile cap details are given in plan details, and of course vary with the number of piles in a cap.
This is a 'typical' detail, that can be used many places.
The left pile is for compression only piles (which are assumed unless noted otherwise on the drawings).
The right pile is a compression or tension pile (which would be specially noted on the plans or plan details). The rebar is to transmit uplift forces from the pile cap to the pile.
my question is a bearing plate required on top of the pile. I am assuming this is a 100 ton pile. How does the bearing of the steel section on the concrete in the pile cap work. Can get some pretty high bearing values. I have not seen bearing plates used but it seems like they should be. I have discussed this with other engineers and noboday has a good reason why bearing plates are not used on h-piles.
I think this is the question everyone comes to when they first do steel pile/concrete pile caps. I know I took a lot of convincing to accept that the bearing on the end of the H-piles works.
Many years ago, a mentor had me read a few articles that summed up research on this. The conclusion of the research was that the concrete in direct bearing with the steel pile is confined by the surrounding concrete to such a degree, that it can take very, very high bearing values. Unfourtunately, I did not make copies of those articles, and no longer have access to them.
CRSI Design handbook recommends that with a 6" pile embedment, cover plates for bearing are not required. See Chapter 13 of CRSI Handbook. (Page 13-15 specifically in the 1996 edition).
I use a pile cap made of steel plate, stiiffners, and a length of oversize pipe on minipiles. I have this assembly prefabricated and slipped over the end of the pile. If I have a net tension force I weld this to the pile casing. For analysis I check the punching shear through the pile cap by projecting planes at 45 degreees from the end of the plate. It seems to me that gravity loading on the pile cap is similiar to a flat slab load on a concrete column where you check to determine if a drop panel is needed.
An alternative detail for a positive connection is to have the iron workers burn one or two holes through the pile web, and slip a larger diameter (#8) length of rebar through the holes. This elimiates the field welding and is very quick because the holes can be left very rough. One change I would consider is to increase the embedment a little bit.
This is shown in the attached file from an older version of the Caltrans Standard Plans. For some reason, the newer version doesn't seem to include this detail, however the pipe pile detials use a similar detail around the circumference of the pipe.
The need for painting depends on the ground conditions, location and durability requirements.
I have used piles painted in "splash zones" offshore and unpainted H-piles straight in the ground. Steel piles for the most part if they are not exposed, act as grounding rods anyway, allow a nominal corrosion allowance. Geotech report should confirm ground resistivity.
