The passive voice is formed by using a form of "to be" and the past participle of a verb. For example:
* Active: The carpenter built the house.
* Passive: The house was built by the carpenter.
Here, "built" is the verb that changes into the passive form.
"Structure" doesn't have a verb form, so it can't be changed into the passive voice.
However, you can use the passive voice with verbs that describe actions related to "structure." For example:
* Active: The architect designed the structure.
* Passive: The structure was designed by the architect.
In this example, "designed" is the verb that is transformed into the passive voice.