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

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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