Civil Engineering Reference
In-Depth Information
of the present day. Surely this was the prodigious achievement of Roman Concrete
building—before nothing like this, at er it always something like this, before it
impossible, at er it always possible.
B.
Structural Forms
In principle Roman builders employed three structural forms when erecting con-
crete rooi ng:
(1) h e Barrel Vault
(2) h e Cross Vault
(3) h e Dome
269, 270
278, 279
295-300
In general terms, they did not employ the simple barrel vaults for “display archi-
tecture”, i.e. rooi ng expansive assembly halls, e.g. in
thermae
. Roman builders
used the barrel vault for utilitarian purposes, e.g. rooi ng circulation passage ways
in the substructure of amphitheatres. Here the span was limited and, in fact, for
the most part on the same scale as ashlar construction (NB h e Colosseum con-
tains vaulted circulation passageways in both ashlar and Roman concrete, and if
anything the ashlar barrel vaults are of larger span). Another utilitarian applica-
tion of the barrel vault was also out of general viewing as cisterns or the like in
substructures. Higher in social standing are the clusters of barrel vaulted chambers
found in business and administrative premises, e.g. Trajan's Markets (cf
in extenso
L.C. Lancaster,
Building Trajan's Markets 1 & 2; Concrete Vaulted Construction
,
pp. 98-106). However although the sum of these apartments are impressive and
even on an imposing scale, the span of the individual barrel vaults is in the nature
of 4 m-6 m which is nothing innovative in measure. NB It is interesting here to
compare the contrasted destinies of brick vaulting in the Middle East as culminat-
ing in the Sassanian Palace (Taq-I-Kisra) at Ctesiphon. Here the vast mud brick
barrel vaults built without centering which roofed the pavilion halls were l ung
across a span of 26 m, which remained something of a world record until modern
times (v Vol. 1, p. 143). Perhaps with the Taq-I-Kisra attention should be drawn
to the Basilica of Maxentius at Rome on the Palatine (v D. Robertson, i g 111).
h e nave of this building is roofed by cross vaults with a span of ca 24 m and
quite exceptionally the nave cross vaulting is buttressed by barrel vaults of similar
span set transversally over the compartmentalised aisles. h e background to this is
little discussed. Is it connected with a possible orientalising trend discussed in the
Rom oder Orient controversy? In short it was not in their employment of barrel
vaulting that Roman builders were innovators. Here they continued the usages of
Hellenistic ashlar construction.
Barrel
Vaulting
399
392
