Progressive collapse in concrete column

I’m researching the progressive collapse. In summary, I want to see what happens if I apply un displacement controlled de 1200 mm under a reinforced concrete frame to simulate the loss of one central column. i.e I want to redo one model of this paper (usefi et al, 2016). Specifically this model: Figure 1.

I already have my model, but it doesn’t give me the correct results as in the paper. this is the model I made: figures 2 and 3

as you can see, the results are not logical. I apply a downward load but it gives me positive displacement. and it seems that there is some problem with the analytical surfaces I think I’m making basic mistakes because I’m not sure if I’m applying the loading speed correctly.

Any suggestions, please?

Figure 1

Figure 2

Figure 3