"Today, most engineers fear shells and domes: they are mysterious and difficult to assess and master. ...Historic arches, shells and vaults are too easily seen as risks instead of opportunities. Under the motto of 'safety', these structures are destroyed and replaced by common beam-column systems. This is regrettable: their great historic and aesthetical value is lost forever. A better understanding and assessment of their structural behaviour holds the key to their conservation. ...[S]hells and arches are highly efficient structures."