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maximum spacing of lap splice bars in tension

maximum spacing of lap splice bars in tension

maximum spacing of lap splice bars in tension

(OP)
Hi ,

I am doing a design of pile cap with single pile, in which the pile bars and the vertical reinforcement are spaced 150 mm center to center.
But the pile tolerance is 75 mm which sometimes makes the vertical bar of pile cap and pile bar in pile to 225 mm.
Can anyone suggest the maximum spacing between the pile reinforcing bar and pile cap vertical reinforcement.


http://files.engineering.com/getfile.aspx?folder=8...

Please give your valuable suggestion.

RE: maximum spacing of lap splice bars in tension

(OP)
Please see the picture attached for clarity

RE: maximum spacing of lap splice bars in tension

When your pile is out 75 mm, there will be a moment to be dealt with in the system. The only limitation is that your reinforcing needs to be able to deal with that moment.

Usually, I'll assume a perfectly vertical strut running from the center of the column base plate down to the top of the pile. That will induce a moment in the pile which is generally pretty easy to deal with. With this scheme, your pile cap reinforcement doesn't really do anything other than provide some extra confinement. I'm assuming that your only significant load here is downward load.

Another design model is to assume that the moment is resolved in the pile to cap connection. In that case, your best bet is as strut and tie analysis and whatever reinforcing layout stems from that.

I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.

RE: maximum spacing of lap splice bars in tension

(OP)
Hi ,

My concern is if the pile has an offset and the pile cap is in tension , the vertical bars in the pile cap is subjected to tension ,
How the tension force from the pile cap bars is transferd to the pile reinforcemnt . Can conrete be in tension to transfer the force from pile cap reinforcemnt to pile reinforcemnt .
This is my major concern ?

RE: maximum spacing of lap splice bars in tension

Once you're beyond the 150 / L/5 limit for non-contact laps, you're in strut and tie territory. You'll need transverse reinforcing in the top and bottom of the pile cap. And there's still a moment to deal with.

I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.

RE: maximum spacing of lap splice bars in tension

(OP)
It is not possible to place bottom bars in pile cap as it would clsh with the pile bars . Since the tolearance of pile is 75mm all direction ,
What i would do in this case ,

RE: maximum spacing of lap splice bars in tension

I see no reason why bottom bars in the cap can't be set between the pile reinforcement unless the pile bars are very congested. Another option is to lap your pile verts directly with your anchor bolts

I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.

RE: maximum spacing of lap splice bars in tension

(OP)
Thats also not possible since in most of the cases the pile bar might hit the anchor bolt . All the problems are due to the pile tolerance of 75 mm.
Is there any new solution for this .

RE: maximum spacing of lap splice bars in tension

Is the pile a driven precast pile? Where is construction at? Pile installed? Cap Formwork in place? How much tension force do you need to deal with.

It would be helpful if you posted sections of the pile and the cap so that we can see the arrangement of the vertical bars. Unfortunately, if you are unable to install horizontal tie bars, you don't have a whole lot of options for resisting serious tension.

See the sketches that I posted in this thread to get a feel for the mechanics of the situation and what needs to happen with regard to horizontal reinforcing: http://www.eng-tips.com/viewthread.cfm?qid=374061. You have a similar situation at both the top and bottom of your cap.

I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.

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