To add conduits to a duct bank, you need to manually route the conduits using tools such as the offset command assistant to position a conduit into the duct bank's encasement. For more information, see Route conduit with an external offset.
If there is not sufficient space, the cross section of the duct bank must be increased as needed and the encasement and other conduits should be manually jogged to maintain the relative positioning. Change the size of the duct bank by selecting all the features of the entire duct bank and then changing their values on the ribbon.
The relation between the conduit run and the duct bank must be manually established or removed.