Dear, I hope someone could help me

I’m modeling a 144 in OD tower of 1.14 in thickness as a pipe, carbon steel, with 35 mts height and an anchor at botton base. I don’t understand why in sustained and Hydrostatic cases the displacements in all levels are negative like if the pipe were shrinking, some suggestion to avoid this effect?. I wouldn't like to model the tower as a rigid in order to have a better visual presentation of the model. We use Caesar II version 5.2

Thanks in advance