问一下几个句子的语法结构

chara21UID: 3051862

1.Amry that housed 26,000 troops and held up to 9,000 Confederate prisoners of war at Camp Chase located at what is now the Hilltop neighborhood of west  Columbus.

为什么用WHAT？WHAT在这里是做什么成分？

2.The arches illuminated the thoroughfare and eventually became the means by which electric power was provided to the new streetcars.

which后面的句子似乎不做成分，那是做什么用的？

3.It was a time when businesses were developing  from single-unit ,centrally managed oprations into umbrella-type structeres where a number of comparatively autonomous units shared certain overheads.

这里是省略了WHICH WAS的非限制性定语从句，修饰前面整个句子么？那be managed to是作动词形容词化，被动表主动的固定搭配解么？

jiang08UID: 2391146

1, cant explain.... [what is now XXX] serves as the object of the sentence.
2, [by which XXX] serves to modify "means". The normal sequence would be: Electric power was provided  to the new streetcars by the means.
3, you read the sentence wrong. [ operations] is the object after from. [centrally managed] is parallel with "single unit" to modify the object.  [where XXX] is used to modify "structures".

my suggestion is: dont get overwhelmed with the names of different sentence structures. they'll only confuse you. Just remember a few golden rules and you are good to go.
E.G.:
basic sentence structure: subject+verb+object