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

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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