The Riding School in the Royal Palace of Naples: Transformations ...

The Riding School in the Royal Palace of Naples:
Transformations in the Timber Covering Structure
Carla Ceraldi, Ennio Russo Ermolli and Vincenza Tempone
INTRODUCTION
In the course of a larger research program aiming at the knowledge of historical developing of
carpentry in the Neapolitan region, from eleventh to nineteenth centuries, and especially at studying
evolution of building technology, an accurate survey is going on in the archives held by numerous
city institutions.
In the Historical Archive of the City of Naples, an unpublished document (ASN Busta n. 2154) has
been found which constitutes the fulcrum of the present paper, and has revealed of great interest to
give a deeper insight in technological means at the beginning of nineteenth century in the field of
timber truss carpentry. It is an estimative metrical evaluation, with illustrative plates and explaining
documents attached, which was the detailed relation on the re-making of the covering structures of a
building pertaining to the Royal Palace of Naples, made by the architect and scenographer Antonio
Niccolini (1772-1850). Born in 1772 at San Miniato, he had already reached become noteworthy by
working in Livorno, Pistoia and Florence, before coming in Naples in 1810, where he eventually
died in 1850. He carried out very important jobs as designer and works director, in which he
showed his great scenographer ability in designing the wonderful Floridiana Park, rich of
prestigious architectonical works, or the monumental stairs of Capodimonte Royal Palace, and also
the numerous transformations of Bourbon Royal Palace and the annexed St. Charles Theatre. These
last works gave him fame as the most important theatre decorator in Italy in the first half of
nineteenth century. During the realization of these transformations, he thought to allocate the scene
machinery in the attic of a building contiguous to the theatre, used as Royal Riding School, and at
this aim he built a new covering system. The found document is a detailed description of this
construction, at the scope of its economical quantification. All works needed for the dismantling of
the existing coverings, the realization of the new structures, partially re-employing timber elements
of the demolished structures, and provisional meanings, are reported in plenty of detais, with special
reference to working techniques and jointing technologies.
Basing upon this document, the analysis of Niccolini’s design for the new timber structures of the
Riding School has been possible, from a technological as well as structural point of view,
comparing the new trusses with the existing ones which he dismantled, and with other timber
covering structures still existing in other spaces of Naples Royal Palace, dating at the same period.
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In conclusion a noteworthy constructive knowledge can be recognized to Niccolini in facing the
special service conditions due to the new functions to be assigned to the attic.
THE ROYAL PALACE OF NAPLES AND ITS RIDING SCHOOL
The construction of the Royal Palace of Naples took place for desire of Viceroy Fernandez Ruiz de
Castro, in 1600, to accommodate the Spanish King and his court when staying in Naples. The job
was assumed by Domenico Fontana (1543-1607), a famous architect of papal court, but its
realization went on for centuries, and was almost completed only in 1848 by Gaetano Genovese
(1795-1875).
Particularly, apart of the royal apartments, the Palace was enriched with all the facilities which
characterised the great Courts of Europe: gardens, the Court Theatre, and the Riding School. The
last one was a typical structure of royal residences, and is also present in the most important
military barracks, where it is assigned to indoor training exercises.
As quoted by Donghi in his Manual of Architecture, (Donghi 1923, Vol. II, Part I, Section 1), riding
schools usually had quite small dimensions, from a maximum of 52.5 x 21 metres to a minimum of
38 x18 metres. Larger ones also had galleries to allow public attending equestrian exercises. So
these riding schools were different from large exercise halls, conceived for military training in
countries with very cold weather, and also used for military parades and shows in presence of
numerous public, like the Darmstradt exercise hall, built in 1771 (Ceraldi 2003) or the Manesh,
built in Moscow in 1818 by Betancourt, whose description is reported in Rondelet’s Treatise
(Rondelet 1833), both having timber trusses covering structures, with a span of about 42.00 and
50.00 m, respectively. In Italy an interesting example is represented by the riding school belonging
to the complex of Scuderie della Pace, built in Florence between 1865 and 1868; the rectangular
hall, now housing a gallery of plaster casts, is about 40 x 20 metres and is covered by timber
trusses at view, (Caselli 2005). For the present case, in any way, the riding schools built near the
great European courts are more significant; the most famous is the Spanish riding school in Vienna,
built for Emperor Leopold I in 1681, and restored in 1735 by the architect Josef Emanuel Fischer
von Erlach (1693-1742). In this category can’t be ignored the riding schools realized by Giacomo
Quarenghi (1744-1817), who was the court architect of tsarina Catherine II, from 1779, when he
moved to San Pietroburgo: the Imperial Guards Riding School, built in 1801 besides the Imperial
Palace, and the Royal Riding School in Munich, built for the King of Bavaria, both described in the
original drawings of the author, (Quarenghi 1845).
Apart from the climatic differences, the riding schools were also present in the Kingdom of Naples,
during the eighteenth century, in strong connection with the royal residences. The presence of a
covered space for training horses seems in this case a necessary adjoin to other related functions,
often housed outside the royal palace, as stables or coaches depots, as well as residences for the
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equired staff: pageboys, coachmen, equerries. Some unpublished drawings dating to the second
half of the eighteenth century (SBN, b. 27 A (71 1-4 ), related to the riding school built by Charles of
Bourbon at Mascabruno Palace for the utility of the new Royal Palace in Portici, show the presence,
in the north-west angle of the complex, of a large space named “covered manege”, a rectangular
hall with double height, directly accessible from the courtyard (Tempone 2005). A similar structure
was provided also in the new stables which Charles intended to establish in the Calabritto Palace in
Naples. The relative nearness of this noble building to the Royal Palace and its inveterate missing of
spaces induced the king to buy the Calabritto Palace in 1738, to house the large apparatus of horses
and coaches of the court. A design drawing, dating to the same age, signed by Antonio Canevari
(1681-1750?), shows the large amount of transformations and enlargements advised for the building
to create stables for about four hundred horses, coaches depots and residences for soldiers and
officers. In this drawing it is evident the presence of a space, situated on the north-east side of the
courtyard, labelled as covered riding school in the drawing legend. Also in this case it is a
rectangular room, whose regularity is interrupted on one side by the stairs giving access to the upper
floor. It is probable that the failing of this project of transformation of the Calabritto Palace - which
without any modification will be sold to the previous owner in 1754 – forced the king into deciding
to situate the royal riding school inside the Neapolitan Royal Palace. Starting from 1760, a large
square named “square of the riding school”, in the place of the ancient viceroy’s gardens was build.
As can be seen in some planning of the end of eighteenth century (ASSN Drawing by unknown
hand, Royal Palace of Naples, Plan of the piano nobile (fig.1); Naples, Museum of San Martino:
Topographic map of the city of Naples and of its borders, 1750-55, Tav. 18, by G. Carafa) and from
a model of the complex of the Royal Palace made by Antonio Niccolini in 1811, (fig.2), (held in the
Museum of the Historical Apartments of the Royal Palace), this square is enclosed on the south side
by the eighteenth century expansion of the palace, named new arm, and, on the side near Castel
Nuovo, by some low constructions used as stables and factories. A narrow portico on the west side
connects the new arm to the St. Charles Theatre, while on the north side, the square is delimited by
the theatre and the riding school, object of the present study.
The space is of rectangular shape. The elevation on the square, where there is the main entrance, is
divided by a sequence of round arched openings, marked by pilasters. Inside each of them there are
two superimposed windows, square in the lower level and with flat arches in the upper one. An high
masonry strip divides the arcades from the lower end of the two slopes roof.
A required datum for the study of the covering structures of the riding school is the approximate
dating of its construction. As a quo limit, the year 1737 can be taken with certainty, being the
building date of the St Charles Theatre; in fact the riding school connects to it perpendicularly,
showing no alignment with the standing wall of the viceroy’s garden. There are no surveys
suggesting that the construction was a transformation of a previous one, built by Antonio Domenico
Vaccaro (1678–1750) to house the Farnese Collection successively transferred in the Royal Palace
of Capodimonte (Mascilli Migliorini 2001). Also there is no evidence for the identification of the
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iding school with the construction made by Charles of Bourbon in the royal garden, probably in
1739, to house the new porcelains factory, also successively transferred in 1743 to Capodimonte
(Minieri Riccio 1878). Some documents, regarding the works of renovation made in the Neapolitan
Royal Palace in the years 1744-1745, testify the activity of many craftsmen inside a cavallerizza
(ASN F. 943 - Register of the works made as ordered by H.M. to Mr. D. Angelo Fernandez, from 1
January 1745 to 16 August of the following year). Even if this word could identify a covered riding
school, it’s more likely that it refers to a building of the seventeenth century, placed on the south
side of the Palace. On the other hand, the fact that in those years the riding school was not realized
yet, is also proved by the circumstance that in 1745 a place for housing, outside the Royal Palace,
stables and coaches depot was still looked for (ASN F. 944). In this document is quoted a report
dating 20 September about “the realization of stables in Chiaia”; and also an account about the
previous report, dating 9 October, by the Prince of Stigliano, responsible of royal riding schools and
stables, referring about “the places for housing coaches and horses”. It can be more probably
presumed that the edifice was built when also the large courtyard in front of it was realized, in
substitution of the existing viceroy’s garden. The trees and plants of this garden can still be seen in
a picture by Antonio Joli (1700-1777) dating about 1759, (fig.3), which shows the completion of the
new arm, intended to house the apartments of Royal Princes.
Figure 1. Eighteenth century plan of Royal Palace of Naples (ASSB)
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Figure 2. Model of Naples Royal Palace (Museum of Historical Apartments in the Royal Palace of Naples)
Figure 3. A. Joli, Royal Palace and Castel Nuovo, 1759, (Beaulieu, private collection)
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In conclusion, the building of the riding school ought to be inserted between those works made
probably in 1760, intended to configure the new inner square following a homogeneous formal
criterion, with the boundary buildings, the riding school and the portico, recalling in the prospects
the decorative pattern of the new arm of the Palace. In any case the riding school probably already
existed in 1771, when Ferdinando Fuga (1699-1781) built the confining edifice to house the new
porcelains factory for King Ferdinando IV. This last building, which closes the inner square on the
north side, was configured with the same pattern of arches and pilasters, and will be transformed in
saddlery during the decade of French occupation (ASN F375), (D’Arbitrio 2003).
The riding school and all the buildings quoted above were demolished, during a global renovation
of the Royal Palace, which took place after a big fire in 1837. Starting from 1842, in their place, an
English garden was created. While the porcelains factory was already demolished in 1843, to give
way to a new terrace beside the new garden, the riding school was only eliminated in 1845.
THE UNPUBLISHED DOCUMENT OF NICCOLINI
The document held in the Historical archive of the City of Naples (ASN Busta n. 2154) is dated 4
February 1824 and is entitled “Measure and evaluation of the different works made by the
contractor Mr. Antonio Scaramuzzino on commission of Domenico Barbaja in the attic of the Royal
Riding School under the supervision of the architect of the Royal House Sir Antonio Niccolini”
(fig.4).
Barbaja was the manager of the St. Charles Theatre in the first half of nineteenth century and the
fame of the theatre in this period was due to him, so that Alessandro Dumas defined him the “prince
of managers”.
Attached to the document there are two plates: “Demonstration of the demolished roof of the
covered Royal Riding School” and “Demonstration of the new roof of the covered Royal Riding
School, under whose trusses has been realized a new space to be used by the Royal St. Charles
Theatre to keep the machines and the scenes of the theatre”, the second of which is autographed by
Niccolini. Another drawing of the new covering structure, autographed by Niccolini as well, is held
in the National Library of Naples (Fondo Palatina, Banc. I 19 10 ).
The studied document is composed of two parts. The first one is a detailed estimative metrical
evaluation of the works needed for dismantling the existing covering system of the riding school,
and the re-building of the new one, including all those necessary to connect the attic of the riding
school to the open gallery covering the foyer of the contiguous theatre. At the end of 129 pages
there is the signature of the architect Pasquale Brunetti, as author of the measures verification and
economical quantification. The total amount of the described works is 16 614.36 ducats and is
confirmed by the signature of Niccolini, with an accompanying statement of finished works.
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Figure 4. Front page of the document
Then a letter follows sent by Niccolini to the Minister of Internal Affairs, explaining the reasons for
the considerable increase of charge, as requested by the Minister himself. Niccolini gives many
justifications for the larger expense:
- the fir wood employed, coming from Tuscany, has been carried in the harbour of Livorno
without using the more cheaper fluvial transportation on Arno River, due to the lasting
period of drought;
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- the expected re-employment of timber structural elements coming from the dismantling of
existing covering system has been possible only in a small part, due to the large degree of
deterioration;
- the previously designed structure has been strengthened to grant a greater level of security
for the underlying riding school, which ought to be used by the royal family. At this
scope Niccolini has foreseen to increase the number of trusses to limit their mutual
distance, and to use more wrought iron connecting devices, made with the best quality of
iron;
- moreover, to reduce the danger of fires and prevent the percolation of water from the
attic, he has believed it appropriate to build a paving of beaten lapillus over the plank
floor leaning on the tie-beams of the trusses. This has caused a large loading increase
leading to the necessary enlargement of the cross-section of the tie-beams and introducing
supporting timber trestles at their headpieces.
Niccolini’s worries about structural stability, which led him to strengthen the previously designed
structures, has been also due to the following circumstances: the pre-existing structures ought to be
restored only ten years after their construction; the metallic connections in the middle of the tiebeam,
which increased the reliability of the structure, could not be realized in the new trusses
because it was necessary to leave sufficient free space for the scene equipments and machines; these
new items induce a large loading increase.
The second part of the document gives a description of the works made inside the riding schools,
under the attic, which, in contrast with those described in the first part, were not in charge of the
Ministry of the Internal Affairs, but of the Royal House. This second estimative metrical evaluation
is composed of 96 pages and the total amount is 3 860.22 ducats.
Notes on the units of measures
The unity of measure used in the document for the economical quantification is the Neapolitan
Ducat, which, after the law promulgated on 14 August 1814, was divided in 10 carlines or 100
grana. This subdivision, confirmed by the law of 20 April 1818, was largely in use even after 1861
when with the Royal Ordinance of 17 July 1861, following the unification of the Reign of Italy, the
value of the ducat was fixed at 4.25 Italian lira. Up to date value of the Neapolitan ducat is about €
33; so the expense for the works computed in the first part of the document is about € 550 000,
while for those in the second part is about € 130 000.
Measures of length are given in Neapolitan palms, each palm divided in 12 ounces, and each ounce
in 5 minutes. After the introduction of the decimal system the Commission of the Royal Academy
of Sciences in Naples, in 1811, fixed the value of the Neapolitan palm in 0.263670 m.
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Measures of weight, also used to quantify the wrought iron connecting devices, are the cantaro,
divided in 100 rolls, and each roll in 1000 trappesi. The same Commission fixed for the cantaro the
value of 89.09972 kg, (Salvati 1970).
DESCRIPTION OF THE NEW TRUSSES DESIGNED BY NICCOLINI
The new covering structure of the Royal Riding School (fig.5), of which Niccolini made the design
and directed the construction, consisted of 16 trusses placed interspersed at intervals of 2.95 m
between trusses, with a pitches slope of about 39° and a clear span of about 22 m.
Figure 5. Plate autographed by Niccolini, showing the new truss
The truss scheme shows some significant peculiarities due to the new function which Niccolini
must assign to the attic of the riding school. In fact the court scenographer has to face up the need to
house the scene machineries of the St. Charles Theatre, mainly consisting of the scenery designed
for modern performances, as required by the position reached by the Neapolitan Royal Theatre in
the context of the European courts.
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It was in this period that the greatest composers of lyric music came to live in Naples, a city which
in these years reached its maximum splendour. Even if the Neapolitan School, with Zingarelli,
Pacini, Mercadante, was quite abreast of the new times, Barbaja guessed that, for the theatre he
managed, time had arrived to go beyond its tradition and he engaged as composer and artistic
director of the royal music theatres Gioacchino Rossini (1792-1868), who stayed from 1815 to
1822. When Rossini left, the manager substituted for him a rising star in the opera world, Gaetano
Donizetti (1797-1848), who remained at the St. Charles Theatre from 1822 to 1838, composing up
to 16 of the operas to be held here. A few years before, in 1826, Barbaja also put his trust in another
musician, a Sicilian student of the Neapolitan Conservatoire of San Pietro a Majella, Vincenzo
Bellini (1801-1835).
Thus it was to the new role as theatre storehouse that we can owe the modifications which Niccolini
is forced to introduce in the classic Palladian composite scheme, to which these trusses are in any
case referable: the larger distance of the lateral posts from the middle axis. This variation has
caused the lowering of the collar-beam, and the considerable increase of length of the central post,
with the consequent doubling of the upper diagonal struts.
The 19 trusses of the original structure, showed in the plate attached to the estimative metrical
evaluation (fig.6), and there described in detail, have the classical Palladian composite scheme and
consequently present the tripartition of the tie-beam span, realized with the connection to the lateral
posts, made using wrought iron strips, and a third central suspension point, jointed to the reduced
central post.
Figure 6. Plate autographed by Niccolini, showing the existing truss
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The clear span is the same of that of Niccolini’s trusses, but the pitches slope is smaller, about 31°.
The structural elements are constituted of rough-hewed timber beams and there is a floor resting on
the tie-beams, constituted by transversal joists and a chestnut plank floor. The roof covering was
constructed using purlins, chestnut planks and tiles.
This truss typology can be found in the covering system of other buildings in the Royal Palace,
where the original timber structures are still in place; particularly in the west part, which coincides
with the oldest part of the palace, built by the architect Fontana at the beginning of the seventeenth
century, timber trusses of fir still exist (fig.7), with a clear span of about 20 metres, which have a
structural scheme perfectly corresponding with that of the demolished trusses of the riding school,
also with the same pitches slope (Bamonte 2001).
Figure 7. The trusses of the west wing of the Royal Palace of Naples
The expectation of a large load to support has induced the designer, as can be deduced from the
letter just quoted, to use structural elements with a relevant cross-section as well as to employ a
larger number of them. In fact the structure of the slopes is constituted by principal rafters (308 x
409 mm), jack-rafters (308 x 308 mm) and lower rafters (286 x 308 mm), and also the tie-beam is
made by superimposing three timber elements of identical cross-section (330 x 330 mm) near the
leaning extremities, putting a timber corbel and a lower timber corbel under the tie-beam. From the
description given in the document it can be inferred that the presence of special devises to make the
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superimposed elements integral with each other, with the exception of the mortising between the
timber corbel and the lower timber corbel, and the widespread use of pins. All those timber
elements are made up of squared beams, in fir wood, while the principal rafters are of chestnut
wood. Also of chestnut wood are the lateral posts and all the diagonal struts; while the elements
making the collar-beam are in fir wood. The central post is oak.
As can be deduced from the detailed description of works done, the tie-beam is made of four timber
elements connected in the longitudinal direction using three Jupiter’s dart like joints, each locked by
five pins; near the headpieces of the tie-beam six rack-teeth are cut to allow the indentation with the
three structural elements of the slope. Also the principal rafter is not made of a single piece, but of
two timber elements, similarly connected by Jupiter’s dart like joints, locked by pins. The upper
ends of the rafters are jointed to the headpiece of the post with wolf mouth fittings, also used at the
upper ends of the lateral posts. The diagonal struts extremities are jointed to the connected elements
by simple mortising, locked using chestnut pillows.
The typology of the timber to timber connections used is that typically used for timber structures of
the period, widely documented in carpentry treatises and manuals of eighteenth and nineteenth
centuries (fig.8).
Figure 8. Classic timber to timber connections also used by Niccolini
A widespread use of wrought iron straps is made to joint the structural elements making up the
truss, usually fixed with simple pins, with the exception of those connecting the posts to the tiebeam
and the headpieces of the rafters to the tie-beam, where the use of cotter bolts is specified .
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An evident element thought to strengthen the structure, which causes another variation respect to
the classic Palladian composite scheme, is the introduction of trestles of chestnut wood at the
leaning on the masonry walls. Each trestle is realized with a timber inclined joist and a diagonal
strut, perpendicularly positioned in the middle of the first element, having a stabilizing action, both
with a large cross-section (308 x308 mm). Sliding of the upper end of the inclined joist is avoided
by the indented connection with the lower timber corbel under the tie-beam as well as by the
presence of a timber pillow pinned to the lower face of the corbel itself. The lower end of the
inclined joist is inserted in a hollow made in the lateral masonry wall, described in detail in the
document.
As noted by Niccolini himself, the presence of the trestles has prevented the construction of a
simple ceiling made with a cloth, and so the construction of a false vault made of timber was
needed, which is supported by the trusses by the mean of metallic hangers. This false vault is
realized with 52 centrings in poplar wood, each one made by superimposition of two curved planks,
with a total thickness of about 170 mm. The headpieces of the centrings are inserted in housing
arranged in the masonry. In the transversal direction, centrings are connected by six poplar timber
purlins (87 x 87 mm) and four chestnut timber purlins (87 x 87 mm) placed in contact with the
elements of the tie-beam. The inner face of the false vault is made with a plastered cloth enriched
by stuccos frames and swags.
In adjoin to the weight of the false vault, on the tie beams leans the load due to the wooden floor of
the attic, built with rectangular cross-section beams (176 x 132 mm), and half-cylindrical planks,
with a radius of 44 mm, in chestnut wood. Over them there is a paving of beaten lapillus with a
thickness of 88 mm, finished with lime and sand. The presence of a floor of such a relevant weight
(about 200 kg/m 2 ) is certainly justified by the new function of the attic.
The covering mantle, made of bent and flat tiles in lateritious, fixed with lime mortar, leans on a
timber plank, nailed to the elements of the secondary structure below; this structure is built with
chestnut timber purlins of rectangular cross-section (154 x 11 mm), disposed at a mutual distance of
about 1 metre.
Lighting of the attic is granted by the presence of ten dormer-windows, made with a chestnut timber
structure and finished with the same covering mantle of the main structure. The dimensions of those
dormer-windows are very large; in fact they have an opening surface of about 7 m 2 each one.
STRUCTURAL BEHAVIOUR OF THE TRUSS
The drawing in the attached plate and the detailed description of the constitutive elements of the
new truss allow the definition of the calculation scheme of the bearing structure which, for its new
function and for the large span, is certainly a timber structure of notable structural engagement.
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The possibility of evaluating the structural reliability of the design realized by Niccolini is
interesting as the riding school was demolished only 20 years after the building of the new covering
system: its preservation for a long period cannot thus testify of its efficiency.
The calculation scheme has been modelled in the hypothesis of a plane problem, with one-
dimensional finite elements, in the range of linear elasticity.
The presence of the Jupiter’s dart like joints, fixed with pins, between the timber elements
constituting the tie-beam and the principal rafters has allowed the schematization of those structural
parts as single beams, as the locked indentations obstacle mutual sliding. The timber corbel and the
lower timber corbel under the tie-beam cannot be assumed integral with it, and so in the scheme
can’t be inserted a variable cross-section tie-beam, because of the lack of special devices introduced
to prevent completely mutual sliding, as the insertion of hard timber wedges.
In any case, the introduction in the calculation scheme of elements modelling all the metallic strips
and connections described in the document allows the schematization of the effective transmission
and distribution of stresses between the structural elements. An analogous situation can be
envisaged referring to principal rafters, jack-rafters and lower rafters (fig.9).
Figure 9. Calculation scheme of the truss
As concerns the constraints between the timber structure and the perimeter masonry walls, the
possibility of sliding and rotation has been left for the truss headpieces, while for the lateral trestles
the absence of lower ends translations have been assumed, as those extremities are housed in slots
expressly cut in the masonry.
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As just described, the structure is made of timbers of different species, oak, chestnut, fir, and also
poplar for the centrings, used as illustrated in the following drawing (fig.10). For those different
timber elements, the characteristic values have been taken from the Italian norm UNI 11035-2 and
are quoted in (table 1).
Figure 10. Distribution of the different timber used in the truss
Table 1. Characteristic values assumed for the different timber employed
FIR CHESTNUT OAK POPLAR
f c,0,k (MPa) 23 22 27 22
f m,k (MPa) 29 28 42 26
f t,0,k (MPa) 17 17 25 16
E 0,mean (MPa) 12 000 11 000 12 000 8 000
G mean (MPa) 750 950 750 500
mean (kg/m 3 ) 415 550 825 460
The calculation scheme has been completed introducing loading as can be inferred from Niccolini’s
detailed description; particularly, action of the dormer-windows on the principal rafters as well as
that of the centrings on the tie-beams have been schematized as single forces transferred at the
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effective supporting elements. Moreover a relevant overload, 250 kg/m 2 , due to the new function of
the attic as a storehouse, has been considered acting on the tie-beam in between the two lateral
posts. Calculus, made with the software Nolian by Softing, has given the stress distribution which
corresponds the following diagrams of normal stresses (fig.11) and bending moments (fig.12).
Figure 11. Normal stresses diagram for the calculation scheme of fig.9
From the quoted diagrams, the presence of a large bending stress on the tie-beam can be inferred,
which is in contrast with the common behaviour of roof trusses. Obviously that behaviour is due to
the relevant loading applied directly on the tie-beam.
Specifically, larger stresses can be noticed in the middle point of the tie-beam and in
correspondence with the lateral trestles, where the design values fm,d of 14.95 MPa e 16.70 MPa are
reached, respectively. A limit state checking calculus, made following the Eurocode 5, assuming
kmod as 0.7 and M as 1.3, gives place to a reference value of 15.61 MPa; therefore the most
stressed cross-sections are in a limit condition.
The remaining parts of the structure, where the normal stress is prevailing, show very small stress
values, thanks to the employment of structural elements with large dimensions in cross-section.
Therefore the widespread strengthening of the structural elements, made by Niccolini to face up the
relevant envisaged loadings, is revealed as being excessive for elements subjected to compressive
stress. Allocating a larger amount of wood in the various elements working as tie-beam would have
been more efficient.
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Figure 12. Bending moments diagram for the calculation scheme of fig.9
In fact, the insertion of the lateral trestles has shown to be detrimental: their absence would affect
not much the distribution of bending moments, which would remain of about the same size, but the
values of the normal stresses, which would enlarge enormously, quadruplicating on the tie-beam
and the collar-beam. Obviously, the presence of the trestles induces a strong thrust on lateral
masonry walls, but not so large as to give rise to overturning phenomena. The loads resultant stay
inside the leaning base of the wall, giving a maximum compressive stress in masonry of about 0.9
MPa.
Structural interpretation of the behaviour of the centrings
In Niccolini’s estimative metrical evaluation, when speaking about the false vault of the riding
school, he said: “Description of the 52 poplar centrings, put under the tie-beams of the trusses to
more strengthen them”. From these words it seems that perhaps Niccolini thought that the centrings
did not just perform the simple function of making the ceiling, but also provided a structural
contribution to the main structure. So a calculation has been done inserting the false vault with its
poplar centrings between the bearing structural elements of the truss. Results are those shown by the
normal stresses diagram (fig.13) and bending moments diagram (fig.14) quoted below, from which
a reduction of the stresses on the tie-beam is evident. However this solution, if admissible, would
produce a considerable increase of the thrusts on the masonry walls, apparently sufficient to
overturn them, and consequently it can be concluded that this scheme is not a description of the real
behaviour of the structure built by Niccolini. Moreover, from the description given in the document
615

about the building phases of the false vault made under the tie-beams, it can be inferred that it was
constructed after the erection of the trusses and related trestles; so the rate of loads already leaning
on the truss would not have been completely transferred to the centring.
Figure 13. Normal stresses diagram for the calculation scheme with cooperating centring
Figure 14. Bending moments diagram for the calculation scheme with cooperating centring
616

Both the calculation schemes analyzed schematize limit situations, in between which the real
behaviour of the structure can be envisaged: the high stresses in the tie-beam, found in the first
scheme, will certainly been reduced by the presence of the co-operating centrings, with a related
increase of the thrusts on the perimeter masonry walls between admissible values, granting their
equilibrium.
REFERENCES
Manuscripts:
Archivio Storico della Città di Napoli (ASN)
Ministero degli affari Interni, Appendice II, busta n.2154
Segreteria di Stato di Casa Reale, F. 943, “Regesto degli espedienti che co’ loro decreti si son
consegnati d’ordine di S.E. al Sig.r D. Angelo Fernandez dal primo Gennaro 1745 a tutto li 16
agosto seguente”
Segreteria di Stato di Casa Reale, F. 944, “Regesto degli espedienti che co’ loro decreti si son
consegnati d’ordine di S.E. al S.r D. Angelo Fernandez dalli 18 agosto 1745 a tutti li 31 ottobre
seguente”
Intendenza Generale di Casa Reale, F. 375
Archivio Storico della Soprintendenza ai Beni Storici ed Artistici di Napoli (ASSN)
Royal Palace of Naples, Plant of the noble floor, Anonymous author.
Biblioteca Nazionale di Napoli (SBN)
b. 27 A (71 1-4 )
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Ceraldi, C and Russo Ermolli, E, 2003, “The marvellous timber trusses of XVIIIth century. The
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