sentences:  The institution attempted to expand its landmark building in 1978, commissioning UK architects Derek Walker and Norman Foster to design a tall tower alongside it, the first of several proposals from leading architects.But each time the effort was abandoned, because of either the cost or the design or both.To secure additional space for the museum's collections, then-director Thomas N. Armstrong III developed plans for a 10-story, $37.5 million addition to the main building.