ABSTRACT
The 20th Century was a key in the development of skyscrapers. This development was marked by the search for greater performance, making buildings taller and slenderer. New structural materials (like steel or high resistance concrete), new techniques (like post tensioning) and, over all, new structural concepts, have played a fundamental role in this development process. In this sense, those structural concepts derived from the tube of F. Khan and M. Goldsmith gain importance and mark a before and after in this kind of buildings.
