Fig. 5.12 Hagia Sophia, Istanbul, Turkey, from the sixth
century CE, The dome which spans the central space is
carried on four arches which transmit the weight to four
massive piers. These are buttressed by the surrounding
parts of the building. The combination of dome and arches
allowed a complex interior of very large volume to be
created. The architectural effect was one of a feeling of
immense space. [Copyright: Rowland Mainstone]
advantages of this were that it allowed great
overall thickness to be achieved without the
occurrence of a severe weight penalty, that the
weathertightness of the structure was
improved and that it allowed greater freedom
in the choice of the shapes for the inner and
outer visible surfaces of the dome.
The first very large structure to which this
idea was applied was the fifteenth-century
dome of Florence Cathedral (S. Maria del Fiore)
by Brunelleschi (Fig. 5.13).^4 The dome was
much higher in relation to its span than those
of the Pantheon or the Hagia Sophia and this
would have reduced the hoop stresses.4 An account of the construction of this very significant
structure has been given elsewhere - see Mark (op. cit.)
and Mainstone, Developments in Structural Form, London,
1975, Chapter 7.3 See Mark (ed.), Architectural Technology up to the Scientific
Revolution, Cambridge, MA, 1993, Chapter 4.
Pantheon dome^3 and that they had a sound
qualitative awareness of the behaviour of form-
active masonry structures.
A significant development in the history of
the masonry dome was the use of two struc-
tural skins separated by a voided core. The
155Masonry structures