staged construction

[AhmedFawzy]

hi all, i have problem making the construction stage
i use the OpenSees navigator from MATLAB

in my case, i am modeling two span precast beam bridge with a continuous slab so in our case, the beams will placed and deformed, then the continuous slab will be pored

so the slab shouldn't suffer from any deformation or straining action under deadload
and that is the reason for me need to make staged construction
if any one can help me and tell me how to perform that,
that will be great

thanks in advance