Why is there a kink in the PCI interaction charts for Pn < 0 (pile is in tension) even though the phi factor for tension (=0.9) remains constant for all cases of axial tension/moment pairs?
I understand the kink on the compression side comes from the phi factor changing linearly from 0.7 to 0.9...
Does anybody know of some literature to design/determine the embedment length of mild steel rebar in prestressed concrete piles to transfer uplift loads?
