Node to Surface Contact

[MDSmith526]

I have been looking at the zerolengthinterface2D element to use for contact between beams. There are two example scripts on the wiki for these. However, when I try to make the seperate structures come apart, as opposed to coming into contact, there are major issues. Is this element not capable of seperation after contact is made? If not, is there another method I can use for surface-to-surface or node-to-surface contact in OpenSees?

The basic problem I have is similar to having two cantilever beams, one just above the other and I want them to contact if I push the top one down, but not if I push it up.

Thanks for your help.