Shear Flow in Grout Filled Pile

[InPlanePat]

Was asked to check the connection of a micropile (12.75" OD casing, grout filled) embedded 2' into our pile cap that was modeled as having full moment fixity (not my call). I took that to mean check stress in the concrete on the "front" and "back" of the connection as the pile tries to flex (the Marcakis and Mitchell method). But now the discussion has turned to whether or not the grout has enough bond strength with the inside of the pile casing to adequately transfer shear at the interface (i.e. shear flow between grout and pile).

I'm struggling to get my head around the whole setup and argued (to no avail) that:
1) This should have been considered as part of the pile design, not the connection
2) If the pile is in flexure, half of the grout cracks right off the bat and its bond to the casing should probably no longer even be considered

Any suggestions on setting up this problem? I don't even know what section properties (cracked, uncracked) I should be considering. Should I just consider the section as a solid circular rod and find the shear stress at point di away from the NA?

Any help is appreciated!

Thanks,

 

[HTURKAK]

Having full moment fixity literally means plastic hinge can develop just below the pile cap . Is this true ?


True .. moreover the value of the nominal allowable axial load transfer stress, btw pile surface and grout should not be taken more than 20 psi .

I will suggest ,
-provide shear keys inside the casing or,
- provide dowels welded to inside the casing ..
- provide more info. ( size of the pile cap, proposed conn. detail, design effects ..) to get better responds..

Good luck..





Use it up, wear it out;
Make it do, or do without.

NEW ENGLAND MAXIM

 

[CDLD]

AISC has a guide on youtube for concrete filled HSS.

https://www.youtube.com/watch?v=1fzqBwZKLJQ&t=3018s