50 YeLairsst iAnggos
Reprinted from Volume 5 No. 4
June 1969
NSC 31
April 19
Landing a section of the roof steelwork
Like many other highly industrialised
nations, France has sought to solve its
desperate housing problems by making use of
prefabricated structures, in steel as well as in
other constructional media. For this purpose
various consortia have been established; one of
them consisting of architects and industrialists,
which was formed in 1962, is known as
GEAI (Groupement pour l'Etude d'une
Architecture Industrialisée). As a result of their
investigations, GEAI were able to construct a
prototype block of flats in Aubervillers early
in 1966, the principal virtue of which was that
a completely dry system of construction was
involved above the foundations. Subsequently,
a scheme for 500 flats, consisting of 25 blocks of
20 dwellings, was prepared for a site in Rouen,
the scheme being known as ‘Grand’Mare III’.
It is the object of this article to describe the
salient features of this project which is now
rapidly nearing completion and has been the
subject of a recent visit by representatives of
the European Convention of Constructional
Steelwork Associations, including the BCSA.
Structural elements
As will be observed from the accompanying
photographs, the elements erected on the site
are comparatively few in number. The loads
are carried by steel columns and an unusual
floor and roofing system comprising components
which are reminiscent of mattresses. These
mattresses consist of three-dimensional latticed
frames, 300 mm deep, formed into panels based
on a 900 mm square module, typical sizes on plan
being 3.600 m × 2.700 m, 4.500 m × 2.700 m and
5.400 m × 2.700 m. Within the blocks there are
steel staircases, but provision could be made for
lifts.
The floors comprise thin concrete slabs and the
ceilings, interlocking chipboard panels. Dry
partitions, either permanent or temporary, are
used, together with prefabricated wall panels,
balcony balustrading, joinery and blinds. It is
interesting to note that all the main elements
have been subjected to fire tests, with completely
satisfactory results.
The most original item in the GEAI system is
undoubtedly the floor mattress. As will be seen in
the photographs taken in the fabrication shops
in Rouen, the standard panels comprise top and
bottom grids, made from 10 mm round bars at
300 mm centres in both directions.. These grids
are staggered by 150 mm in both directions with
respect to one another in order to accommodate
the 8 mm lacing bars providing the infilling.
The main framework around the mattress
consists of four lattice girders comprising angle
chords and flat web members. All the units are
interchangeable as they are accurately fabricated
in jigs. There are also special panels to allow for
the passage of vertical ducts, etc.
A particular feature in the Grand’Mare III
scheme is that the exposed steelwork is in Corten
weathering steel. To prevent any possible
staining in the early stages of oxidation, the
columns are offset from the façades by the
insertion of special brackets.
Construction
The scheme occupies two adjacent sites where
provision has been made for 100 three-room flats,
312 four-room flats and 88 five-room flats.
The twenty-five blocks are all five storeys high,
the ground floor of each being limited to the
entrance hall, a perambulator area, a dustbin
store and the central heating unit. Nine blocks
are isolated but the others are in groups of two
or four.
Despite the fact that the weight of the GEAI
structures is about one-quarter of that of
traditional buildings of the same volume and
for similar purposes, it was necessary to employ
some piled foundations as the sub-soil conditions
were not good. There are eight driven piles per
block, 35 concrete bases and a lean-mix slab for
the enclosed portions of the ground floor.
Apart from pile-driving equipment, the only
vehicles on the site were lorries which delivered
the components and mobile cranes which erected
them.
Once the foundations and bases for a block
of flats had been completed. It was possible to
start erection. To ensure stability, braced panels
are incorporated in the design as strong points.
These units, consisting of two 180 mm deep
column sections, 15 m high and spaced at 3.600 m
centres, braced with channels and angles and
completely fabricated in the shops, were the first
components to be erected on the site where they
were held in position in temporary guys until
sufficient steelwork had been erected to make
the structure stable in all directions.
The central parts of the blocks are reserved for
vertical circulation and for the landings serving
the flats. The landings and the corresponding
portions of the roof were made from 5 mm thick
plate and light joists.
This steelwork, which was shot-blasted and
painted, together with the staircase steel, was
the only steelwork not in Cor-ten.
On the site, the various mattresses were bolted
edge-to-edge to make up the very large floor units
which were hoisted by mobile crane as shown in
the illustration. Once the steelwork had been
erected it was possible to fix the partitions and
cladding extremely quickly. In fact, the whole
operation could proceed almost independently of
the weather.
Acknowledgements
The architect responsible for the conception and
development of the GEAI system is Marcel Lods.
The BCSA also gratefully acknowledge the help
given by the Compagnie Française d'Entreprises
Métalliques (CFEA) who kindly supplied the
photographs.
GEAI,
Rouen
Welding the infilling for a GEAI mattress A view of a completed façade of a GEAI block