Complex sentence: The extensive rebuilding of the Luhansk steam locomotive factory was conducted in the years 1928--1933 by the construction board, Luhanbud, during which the present company's central building was constructed.
Split into simpler sentences: The extensive rebuilding of the Luhansk steam locomotive factory was conducted in the years 1928--1933 by the construction board "Luhanbud". During which the present company's central building was constructed.