Civil Engineering Reference
In-Depth Information
concrete dome when it had become a self supporting structure and the centering
had been struck.
Appendix: Large Span Dome Construction after the Pantheon
Large span concrete domes continued to be built by Roman Builders until concrete
construction came to an end during Constantinian times shortly at er the removal
of the Imperial capital to Byzantium (cf, e.g. the Temple of Minerva Medica,
span 24 m; h e Mausoleum of St Helena, span 20 m, ca 350 AD). Also domes of
ashlar masonry continued to be built in the East Roman provinces, but of rela-
tively small span (e.g. ca 5 m-6 m). Never during antiquity was ashlar masonry
used to construct vaults or domes of large span. Ancient builders always tried to
minimise the self load of domes by using light materials and considered ashlar
masonry impossibly heavy (cf C. Mango, “Byzantine Architecture,” p. 9). Large
span ashlar domes are Renaissance and later in date, e.g. new St Peters in Rome,
span 42 m, ca 1560 AD.
With the lapse of concrete as a building material, concrete domes ceased to be
built, and the adoption by Christianity of the timber framed gable roof basilica
as the form appropriate to monumental church building directed the concern
of builders elsewhere for two centuries. It was not until the i rst half of the 6th
century AD that the question of constructing domes of large span again came
in issue. h is occured in a striking manner, the circumstances forming a paral-
lel to the construction of the Pantheon 400 years previously. h e construction
of Justinian's Ayia Sophia was bold and novel, and was unmatched by any later
Byzantine church building.
Before considering the procedure of constructing the dome of Ayia Sophia (span
32.60 m) and the installations provided for this as a sequel to the construction
of the Pantheon dome (span 43.30 m) two basic considerations must be called
to mind. h e Pantheon dome was built of Roman Concrete and surmounted a
round building, factors which were characteristic of Roman domes. On the other
hand the Ayia Sophia dome was built of brick and surmounted a rectangular plan.
h is involved two consequences. h e building material of the Ayia Sophia dome,
unlike that of the Pantheon, did not require the installation of shuttering to con-
tain it while plastic. h at is to say the installation of centering at Ayia Sophia was
an issue entirely on its own merits, not involved in any way with the provision
of shuttering. Secondly whatever centering was required for building the dome at
Ayia Sophia there was the additional consideration of provision for building the
pendentives, the “pendant” spherical triangles to convert the square ground plan
Discon-
tinuance
of con-
crete dome
construc-
tion
411, 412
298-300
