LBS Simple dead continuous live steel bridge analysis

Hello,

After searching past questions on the forum, I am still unsure how to model a simple for dead and continuous for live structure in Leap Steel. 

Is it possible to dictate different support conditions during the analysis? For example, have two lines of pinned bearings at an intermediate bent for the non-composite dead loads that become fixed bearings for the composite dead loads and live loads? My thinking is that this would represent no negative moment at the intermediate bent for the non-composite dead loads and then generate negative moments (that would be used to separately design the connection at the bent) for the composite dead loads and live loads. Are analysis stages that manipulate support conditions possible?

Thanks.