prestressed concrete

Dear Abaqus user

I am modeling a post-tensioned concrete pier with 4 part:

-concrete foundation,pier,cap(C3D8R) and tendon(wire,B31)

 I input prestress force by predefined file,stress in initial step.The first step is static,General to find equilibrium.

 I embeded the beginning & the end of wire in foundation & cap. contact between (foundation,pier) & (pier,cap) is hard normal contact and the tangential behavior is penalty.

the analysis run with Zero pivot warning and tension stress in wire did not transfer to the concrete as a compression stress!!!why?

I hope you help me.

best regard.

mojdeh.