The Deck section of the Stack for a selected bridge allows you to choose your continuity method. By default, bridge continuity is set to Deck and Girders, which is a fully continuous arrangement.
You can change this at any time in Edit mode. With a fully continuous arrangement, the girders are connected together longitudinally with an in-situ diaphragm over the pier.
Select the bridge.
Select the bridge deck.
Open the Stack if it is not displayed already
Expand the Attributes section.
Toggle the drop-down menu in the Continuity field.
Click to select a different continuity arrangement.