Your example does not seem to show stage construction. You are asking for a loading pattern to be added onto a model that has been deformed by a differnt laoding pattern. That is basically a load combination. That maeans creatindg a load combination. However, if you are concerned that the combined loading of both the stages may result in excessive displacements, then you should create a new load primary load case and use the REPEAT LOAD command, then use the PDELTA or NONLINEAR analysis.
The concept of STAGE CONSTRUCTION is when there is where part of the model is subject to a loading pattern and additional geometry is added and subject to a secondary load pattern, the effects of both are then combined to produce a final result.
The concept of STAGE CONSTRUCTION is when there is where part of the model is subject to a loading pattern and additional geometry is added and subject to a secondary load pattern, the effects of both are then combined to produce a final result.