Absolutely yes. You have to divide your structure into several parts and then activate and deactivate your desired parts. I suppose you want to simulate the staged construction of dams, true? 

yes. i want to simulate the dam in 8 stage and in each stage add the gravity load.

i understand that i must use of model change in interaction module. but it dont work exactly.I dont why not.

I am not aware of Abacus capability to perform the desired analysis but PLAXIS can effectively do stage construction that I am sure.

I  found my answer. thank  you.