Someone know the name of this kind of structures?

[zhddz]

I am writing an essay, and I need to know the name of this kind of structures.
It’s a structure to reinforce a bridge for heavy cargo transportation, so that the bridge can carry loads that it couldn’t carry originally. After the heavy cargo passing the bridge, in some circumstances, the structure is removed, and in the other circumstances, it is left there permanently.
The structure shares the foundation with the original bridge, like a multi-level bridge, or bridge on a bridge.
Does someone know how to call the structure?

 

[bridgebuster]

how about temporary shoring?

 

[Lomarandil]

I'd second that.

 

[ImminentCollapse]

Shoring was my first thought too, but it generally doesn't share the same foundation. For heavy loads, you probably shore mid-span or some distance away from existing piers and foundations. The bridge on a bridge comment sparked some vague recollection of someone, somewhere, affixing a Maybey bridge on a deck to supplement the existing superstructure in carrying an overload. In any case, this would be such a unique situation that I doubt it has a general name. So I am going to name it. What your are describing is a "Doubler-Bridge"TM (patent-pending to IC)

IC