Civil Engineering Reference
In-Depth Information
h e most striking shit in Byzantine brick masonry from Roman practice was
in large span rooi ng. Whereas this was carried out in Roman building almost
entirely in concrete, in Byzantine building it was largely ef ected in brick. h ere
were several instances of sizeable brick domes of Roman construction, but these
were clearly exceptional. However in the heartland of the Byzantine Empire (Ana-
tolia, the Balkans, Greece and Italy) vaulted rooi ng in burnt brick was the norm.
h ere was moreover a most signii cant dif erence between the few Roman brick
domes and the Byzantine domes. h e former roofed a circular plan, the latter were
constructed over a square chamber (the circle of heaven over the four corners of
the world). Ef ecting a transition from a rectilinear plan into a circular plan is
a tentative af air in Roman concrete domes, it is the essence of Byzantine brick
construction—a fact little noticed. Byzantine builders employed both the penden-
tive and the squinch to ef ect this transition. h e pendentive was used during the
i rst century AD as a device in ashlar stone masonry vaulting in lands where the
Hellenistic tradition of stone masonry obtained (e.g. the Levant); the squinch i rst
appeared during the 3rd century in Sassanian Persian dome construction.
From the beginning of constructing brick domes Byzantine builders appreciated
that vaulted construction in brick was equally possible with or without centering.
h e model for constructing brick domes on centering was the Roman practice for
building concrete domes—with the possible choice of either l ying or standing
centering. Here the square bricks could be set radially (voussoir fashion which
increased the resistance to the dome spreading at the haunches). h e two methods
of building vaults of any nature without centering were by corbelled brickwork or
by pitched brickwork. In the i rst instance the bricks were set horizontally, each
course projecting beyond the lower. h e bricks were thus cantilevered with con-
sequent subjection to tensile stress induced by bending. However in a dome the
units were in compression horizontally which worked to hold them in place. In the
second instance the l at square bricks were set inclined at a constant angle from
the vertical, so that the mortared jointing of very quick setting mortar combined
with the resistance due to friction prevented them from sliding out of position
during setting.
Byzantine builders did not make use of corbelled construction for domes with
its characteristic steep proi le, but they knew of pitched brick construction. In
conclusion to exemplify the mixed nature of Byzantine building construction the
crowning achievement of Ayia Sophia may be adduced: the structural materials
employed were ashlar masonry, rubble masonry and burnt brick, while the brick-
work of the dome was pitched, but centering was used.
Large
span
vaulted
rooi ng
385, 413
378
411, 413
299, 300
393, 396
400, 401
370
391
385
