Rise Up Pile Cap

[neaveyoung]

Hi, I’m green in design and need yours some advice. I have some doubt regarding to rise up pile cap and combine with the beam and slab. When doing the design all elements is separated slab, beam and pile cap. But now all combine is that will affect the original design? I enclosed the sketch for more detail. Thanks.

 

[msquared48]

If I understand your question correctly...

Now your grade beams are continuous with the pilecap, but even so, you originally had continuity of the grade beams when they rested on top of the pilecap.

Really only one change here other than the elevation change and some additional steel needed between the pilecap and grade beams for the raised condition. The grade beams were pinned to the pilecap in the raised scenario, Now they are fixed to the pilecap. I assume the column is directly above the centerline of the pilecap.

Mike McCann
MMC Engineering
Motto: KISS
Motivation: Don't ask

 

[neaveyoung]

Hi msquared48,

I think you get my point. The column reinforcement is go up from the center line of pile cap. The beam is pin to the column / pilecap if the beam rest on the top of pile cap. But i'm not sure is fix if the beam go thru the pile cap.So if that is the case is there are any different between these two concept? Thanks your advice.

 

[dcarr82775]

I would think the beam is continuous over the pile cap in either case. The clear span of the beam was to the edge of the pier cap (dropped), but is now to the pile itself. that could increase your flexural/shear reinf in the beam.

 

[hokie66]

I would design the ground beams cast monolithically with the pile caps the same as if cast on top.

 

[tngv752]

Original, your pile cap was just like a pin support to pick up the load from the continuous beam and column.

I think the beam now is not continuous. It's stop and start at the pile cap. One beam now become 2 beams. The load from the column directly to the pile cap.
When you fix the beams to the sides of the the pile cap, then need to check the pile cap and piles with the moments and shears and axial forces transfered to the pile cap.

Need to check and detail the reinforcement between the pile cap and beam (and slab).

 

[neaveyoung]

Dear all,

Thanks to you all comments.

Dcarr : Offcource the shear link for the beam will go in the pile cap until the column interface.

hokie66: to rise up the pile cap is to minimise the excavation depth.

tngv: The beam will not seperate out but in continous as early design.

Thanks.