Nonconvergance of Reinforced Concrete Column Subjected to Monotonic Lateral Loading in ABAQUS

Hello:

 My name is Eric and I am working on my MS thesis project.  I have been tasked with analyzing a reinforced concrete column specimen in Abaqus and comparing the analysis results with the experimental measurements.  The column is subjected to cyclic lateral loading. 

I've built a preliminary model in Abaqus.  The concrete is modeled using 3-D continuum elements.  I explicitly modeled the longitudinal and transverse reinforcement using beam elements and the embedded element technique.  I am using the damaged plasticity model for the concrete.  Before I subject the column to cyclic loading I would like to just subject it to a monotonic axial load and monotonic lateral load to gain confidence in my model.  The boudnary conditions are such that the bottom face of the column is fixed against any translations.  For the monotonic axial load case I fixed the top face of the column from lateral translation and applied a gradually increasing vertical displacement.  The boudary conditions are approximately the same for the lateral load case except I fixed the top face of the column from lateral translation in one direction as well as vertical translation while applying a gradually increasing lateral displacement in the free direction.  The plasticity parameters are as follows:

 dilation angle = 35        eccentricity = 0.1        sigmab/sigmao = 1.16         k = 2/3

viscosity parameter = 0.001

 I have no problems with convergance when I subject the column to the axial displacement.  In fact, I get very favorable results.  However, when I try to apply the lateral displacement the analysis terminates due to nonconvergance upon the the first increment of the analysis step.  It should be noted that I apply an axial displacement in one analysis step and I sustain the axial load while applying the lateral load in the second analysis step.  I need help figuring out why I can't get the model to analyze the lateral displacement.  Also note that when I apply the displacement boundary conditions I apply the displacements to every node on the top face of the column.  I defined a nonzero viscosity parameter in hopes that it would take care of my convergance problem.  Also, I am utilizing the adaptive stabilization technique to mitigate local instabilities. 

Any help, comments, or suggestions would be very much appreciated!

Thanks,

Eric