It could be 'relocating the structure' (it would be nice to have the prior context), but given that the text refers to the Bauwerkverschub, Überbaufverschub and Brückenüberbau in nearly a single breath, I'm inclined to think (based on the given context) that the Bauwerk is the Überbau.

The usual translation of Überbau in this context (we're talking bridge construction, right?) is 'superstructure'. It could means a flyover if you're talking about motorways, but that's a different context, and besides the word here is 'Brückenüberbau'.

Sliding a superstructure into position (either all at once or in sections) is a fairly common technique in bridge construction, especially when cranes cannot be placed below or alongside the bridge for some reason.

For a (hopefully) convincing example of the meaning of Überbau in this context, see e.g.


Zur Problematik an Überbauenden von Eisenbahnbrücken
dem Überbau, sondern auch auf dem an. die Brücke anschließenden Damm, wenn .... superstructure ends. The paper looks at some particular features of ...
www.eurailpress.com/archiv/showpdf.php?datei=/erparchiv/ei2...