Civil Engineering Reference
In-Depth Information
rest there was no footing whatever. Workmen could not walk, clamber nor crawl
about the sheer domical surface of the shuttering. Clearly some form of stepped
wooden staging must have been supplied for carrying out this work. Perhaps the
simplest installation would be something akin to putlog scaf olding. To a certain
degree relevant installation may be sought in the construction arrangements for
traditional modern reinforced concrete domes. Here it is not so much the plac-
ing of the concrete which is the analogy, since modern concrete is “poured” not
placed. However the installation of the steel reinforcing af ords something of
a parallel—and this is generally ef ected from scaf olding. In this connection it
must also be remembered that whatever means of access was provided, this access
remained necessary for i nishing work on the dome—e.g. tiling of either terracotta,
marble or bronze.
E.
Structural Behaviour of Concrete Rooi ng
In the past confused and misleading statements have been published concern-
ing the structural behaviour of Roman Concrete rooi ng in the guise of domes.
Accordingly since domes are also the most common form of concrete rooi ng,
the following remarks on structural behaviour of Roman Concrete rooi ng will be
presented in the i rst instance in terms of domes. Further an attempt will be made
to rationalise some past comment.
When Roman Concrete domes were i rst discussed in manuals during the later
19th century, the basic point at issue appeared to be “Did the material of con-
struction (concrete)
ipso facto
determine the structural behaviour of the dome
(e.g. as opposed to domes of ashlar masonry or of brick masonry)?” Also, since
some Roman Concrete domes were observed to contain set within their fabric a
considerable amount of brick masonry, “What was the function of this inset brick
masonry?”
Two opposing attitudes were manifested:
Mono-
lithic
construc-
tion?
(a) Concrete because of its physical nature behaves in a dif erent way from masonry
construction. It acts as a “monolith”, and therefore concrete domes do not
spread at the base and thrust outward their supporting structure. In this event
the brick work inset into the concrete does not perform any structural service
in resisting this outward thrust.
(b) Concrete domes do not function as monoliths which transmit all loads verti-
cally downwards but behave in a manner akin to masonry domes and tend to
thrust outwards at the haunches. h us the brick masonry built into the concrete
fabric is intended to strengthen the structural behaviour of the dome.
