huangyhg

prestressed concrete pile to cap connection
i'm trying to accurately model a pier in which two 18" prestressed concrete piles (one battered) will be tied together using a simple pile cap. since there will be significant lateral loading and need for moment transfer, i'm trying to find typical detailing for a simple moment connection. the following are details that i've seen and/or used in the past:
1) simply embed the pile 12" into the cap.
2) embed the pile ~3-6" into the cap and expose the strands an additional 9-12".
3) cutoff the pile 6" into the cap and dowel moment transfer reinforcement into the pile.
i read in the florida dot manual that 12" embedment into the cap would be considered a pinned connection and 48" would be considered fixed. 48" seems high to me so i was hoping there would be an alternative/optimized solution.
anybody's thoughts/experience would be appreciated.
thanks.
#2 and #3 are most widely used.
but these would both of these be considered fixed? strands usually need quite a long development length so i'm hesitant to assume that this is 100% effective.
i have done this by embedding conventional reinforcing bar into the top of the piles. the grout may take the form of a high strenght epoxy resin which will not need a large anchorage depth- manufacturers details should be consulted.
i did my thesis on something similar, it was steel piles into a cip pile cap. what i noticed along with research is that if you have embed the piles 2 diameters into the cap it will act the same as if you had steel connecting the two with rienforcing. of course you must think about the size of the cap as well. my recommendation would be to embed the piles a development length above the centroid of the cap and forget the reinforcing. if you treat the lateral force as a point load that acts at the centroid of the cap then you must embed the piles above this centroid such that shear cracking can't fully develop. the spacing of the piles is also a consideration. look up the name mowka, he's done a lot of research on this topic. of course things change when the material changes too, i never tested precast.

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