Complex sentence: The Clarendon Building was added in 1973, as was the Stephenson Building in 1976, with both remaining in use for the Polytechnic's long-awaited conversion into a university.
Split into simpler sentences: The Clarendon Building was added in 1973, as was the Stephenson Building in 1976. Both of these buildings remained in use for the Polytechnic's long-awaited conversion into a university.