Palazzo de'Rossi. Una storia pistoiese

4. Interventi strutturali a Palazzo De’ Rossi
Uno dei criteri di fondo per una progettazione strutturale coerente col contesto architettonico
di un edificio storico quale Palazzo De’ Rossi è il rispetto delle caratteristiche statiche
particolari e di sistema del fabbricato e l’attuazione di interventi, non invasivi, che non apportino
modifiche al suo assetto generale e che, ancor meno, siano in contrasto con la sua
estetica e architettura.
Molte tecniche oggi consentono l’utilizzo di nuovi materiali compatibili con le caratteristiche
di quelli esistenti e determinano, tra gli altri effetti, una significativa riduzione delle
opere che potrebbero variare la rigidezza del fabbricato sotto l’effetto dell’azione sismica
orizzontale.
Prima dell’intervento di restauro, il fabbricato si presentava pressoché integro nelle strutture
e privo di evidenti segni di instabilità quali cedimenti o lesioni.
Sviluppato su tre piani completi fuori terra oltre ad un’altana nella zona centrale, in coincidenza
con lo scalone principale, ed un piano interrato, il palazzo ha struttura in muratura portante
di pietrame di vario spessore con orizzontamenti costituiti da volte a botte e solai piani ed è
coperta da una struttura lignea a travi e travicelli, mezzane e manto di tegole e coppi.
La maglia muraria dell’ edificio presenta una geometria regolare, con un grande vano scala al
centro e spessori di parete notevoli, specie ai piani inferiori e non mostrava segni di lesioni
o dissesti in atto.
Le volte che costituiscono la maggior parte degli orizzontamenti, non presentavano dissesti
conseguenti a particolari problemi statici e anche la buona tenuta dei muri d’imposta e l’assenza
di spostamenti relativi fra le pareti era tale da garantire la stabilità delle volte.
Gli interventi strutturali sono quindi stati circoscritti alla soluzione di situazioni critiche
puntuali o a tutte le lievi modifiche strutturali conseguenti per lo più agli adeguamenti normativi
e impiantistici.
Via del Carmine
2
1
Via De’ Rossi
3
Piazzetta
delle Scuole Normali
4
Vicolo De’ Rossi
4. Structural work on Palazzo De’ Rossi
One of the basic criteria for a structural project in keeping with the architectural context of
a historical building like Palazzo De’ Rossi is respect for the building’s detailed and systemic
structural characteristics and the implementation of non invasive measures which do not
alter its general layout and which, to an even lesser extent, are inconsistent with its aesthetic
and architecture.
Many techniques today allow for the use of new materials compatible with the characteristics
of existing ones and determine, among other effects, a significant reduction in works that
could affect the stiffness of the building under the effect of horizontal seismic action.
Prior to the restoration work, the building was for the most part structurally intact and devoid
of clear signs of instability such as collapse or cracks.
Covering three floors completely above ground as well as a roof terrace in the central area
above the main staircase, and a basement floor, the palazzo has a structure in load-bearing
rock walls of different thicknesses with horizontal elements made of barrel vaults and flat
floor slabs, roofed by a wooden beam and rafter structure with flat tiles and a roof covering
of terracotta tiles and curved tiles.
The building’s walls, geometrically uniform with a large stairwell in the centre and considerably
thick, particularly on the lower floors, showed no signs of cracking or instability.
The vaults which constitute most of the floors and roofs did not show any instability resulting
from static problems, and the soundness of the springing lines and absence of shifting
between the walls were such as to guarantee the stability of the vaults.
The structural interventions were thus confined either to solving isolated critical situations
or to all the slight structural alterations required mainly by statutory and installation
upgrading.
More generally, the design and realisation of the structural interventions regarded chang-
es to the building’s individual structural elements which did not involve either variations
in use or increases of the original loads (permanent and accidental), with the exception
of the realisation, in the outdoor courtyard and inside the embankment that faces Via
del Carmine, of a new building, completely below ground, to be used as a central heating
plant and ENEL electrical cabin. The construction of the underground central heating
plant and the electrical cabin meant the embankment had to be contained using piling on
three sides, made of a series of closely set posts, measuring two hundred and fifty millimetres
externally and reinforced with tubular steel, later cast with suitable mortar.
Of the various interventions, it is worth remembering the realisation of foundations
and the complete restoration of the basement floor, the realisation of a new lift shaft
with the foundation works on some stretches of supporting masonry for the creation
of the extended lift shaft, the formation of new openings with frame rings in structural
steel connected to the walls, the demolition of some floor slabs made in normal profiles,
hollow blocks and composite slabs and their replacement with floor slabs in fretted galvanised
steel elements duly fixed to the supporting structure in beams with wide toothed
wings in the supporting wall.
Furthermore, as mentioned, to comply with regulations – and particularly to allow outflow
from the function room on the first floor and create a link between the third floor and the
roof terrace – it was necessary to create a new indoor emergency staircase in structural
steel with sides in wide winged beams and steps in sheet metal, connected to the external
supporting wall.
Special attention was also paid to the ceiling of the “Salone delle Feste”, built as a highly
unusual domical vault, with an almost square base measuring about ten by ten metres and
a crown of about two metres sixty, made in 12cm thick bricks for the meridians and 24cm
ones near the imposts, stiffened by a series of buttresses in solid bricks set on the reins of
the vault and raised as far as the extrados as supports for the bracing countervaults.
Piano terra
Legenda
1. Ingresso
2. Atrio delle sculture
3. Portineria
4- Sale espositive
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