This is the 7935th most frequent Japanese word.
壊し
"壊し" means "breaking" or "destruction."
In this sentence, 壊し (kowashi) is derived from 壊す (kowasu), meaning 'to break'. It is used as part of the verb conjugated into past tense to indicate the action of breaking.
彼が窓を壊しました。
He broke the window.
Here, 壊れ (koware) comes from 壊れる (kowareru), meaning 'to be broken'. The word 壊れ indicates the state of being broken, describing the condition of the clock.
壊れた時計を修理しました。
I fixed the broken clock.
壊される (kowasareru) is the passive form of 壊す (kowasu), indicating that the action of breaking will be applied to the old bridge.