IPA: /ʌnˈɑːrtʃt/
KK: /ʌnˈɑrʧt/
Describing something that does not have an arch shape or structure.
The bridge was designed to be unarched for a more modern look.
Unarched → It is formed from "un-" (meaning not) and "arched" (from the root "arch" which comes from Old French *arche*, meaning a curved structure). The word "unarched" means not having an arch or not being curved.
Think of 'not' ('un-') having a 'curved structure' ('arched') — that's why unarched means lacking an arch.