ABAQUS Reinforced Concrete Beam Model

Hi All,

I am trying to model a simply supported reinforced concrete beam with longitudinal reinforcement. I am using 8-node solid elements for the concrete, and 2-node truss elements for the longitudinal reinforcement bars. I have embedded the reinforcement bars in the concrete using an Embedded Region constraint. I am then applying a displacement at the midspan (deflection control). I am using the Concrete Damaged Plasticity model for the concrete. My model begins to run but will not converge. Some of the error messages that I get are:

The plasticity/creep/connector friction algorithm did not converge at 1 points

***WARNING: THE SYSTEM MATRIX HAS 1 NEGATIVE EIGENVALUES.

***NOTE: THE SOLUTION APPEARS TO BE DIVERGING. CONVERGENCE IS JUDGED UNLIKELY.

***NOTE: MATERIAL CALCULATIONS FAILED TO CONVERGE OR WERE NOT ATTEMPTED AT ONE 
OR MORE POINTS. CONVERGENCE IS JUDGED UNLIKELY.

Does anyone have any thoughts of what I am missing?

Thanks