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== Abstract ==

The saddle-shaped shells, or hyperbolic paraboloids, often joined together to form a
pitched roof or an inverted umbrella, were used by many pioneers in structural architecture,
such as Félix Candela, which introduced a very innovative use of reinforced concrete in thin
layers or together with some reticulated ribs.
An innovative semi-prefabricated building system was developed in Italy in the years ’30 of
XX cent by a very active brick factory near Piacenza, RDB: the SAP system, that allowed building curved surfaces by prefabricating light elements. After WW2, this technique was applied also for the new structures covering wide spaces for the developing industry or also for public leisure, using prefabricated panels of the desired length. A particularly interesting application was the BISAP (double-SAP) panel that could be adapted for building large shells.
In Codogno (LO), Italy, the BISAP panels were employed to cover a large sports hall,
spanning about 37 × 26 m, without intermediate supports, resting (mainly) on the four corner
pillars. Border pitch beams sustain at the top two crossed beams that separate (and support)
the four hypar fields. On the four sides, two rafter beams are connected by horizontal
prestressed tie beams, in order to minimize displacements and assure the preservation of the
original shape.
The first aim of the structural analysis was to assess the static conditions of the roof under
the service loads assigned by Italian code for SLS, and then to evaluate seismic vulnerability
at ULS of the whole sports hall, being a public space subjected to particular safety provisions.
The FE code used (Straus7) allowed a very careful discretization of the orthotropic slab with
the correct inclination and twist of the ribs, giving a reliable forecast of the behavior also in
seismic conditions: the dynamic analysis of the modal shapes gives a satisfactory response of
the shell, which maintains nearly unchanged his shape during free vibration modes. The seismic
safety of the structure can be then increased by simply augmenting the stiffness of the four corner supports, where shear action is concentrated, by adding ribs to the L-shaped sections
to form cross shaped ones. In this way also the slenderness (and weakness) of additional intermediated pillars could be overcome.

== Full document ==
<pdf>Media:Draft_Content_925257152p1145.pdf</pdf>
== References ==

[1] Sprague, T.S. ‘Beauty, Versatility, Practicality’: the Rise of Hyperbolic Paraboloids in Post-War America (1950-1962). Construction History, vol. 28, no. 1, pp. 165–184, (2013). JSTOR, http://www.jstor.org/stable/43856033.

[2] Engel, H. Structure Systems. (1968) London: Iliffe books.

[3] Journal of the International Association for Shell and Spatial Structures n. 163, Special Issue for the Centenary of the Birth of Félix Candela, Vol. 51 (2010) No. 1 March

[4] Burger, N. and Billington, D.P.: Felix Candela, elegance and endurance: an examination of the Xochimilco shell, Journal of the International Association for Shell and Spatial Structures, Vol. 47 (2006) No. 3 December n. 152, pp. 271-278(8).

[5] Modica, M. and Santarella, F.: Paraboloidi: un patrimonio dimenticato dell'architettura moderna. Firenze, Edifir (2014).

[6] Paolini C. and Pugnaletto, M.: Reinforced brick lightweight vaults. TEMA, vol. 3, No. 1 (2017).

[7] IL, Il Laterizio, bollettino tecnico RDB, RDB, Piacenza (1961) n. 70 e 71.

[8] IL, Il Laterizio, bollettino tecnico RDB, RDB, Piacenza (1976) n. 158-159.

[9] Zienkiewicz, O.C. and Taylor, R.L. The finite element method. McGraw Hill, Vol. I., (1989), Vol. II, (1991).

[10] Straus7, Theoretical Manual. Sydney Aus.: Strand7 Pty Limited, 2005.

[11] D.M. 17.01.2018 - Norme tecniche per le costruzioni, Supplemento ordinario alla Gazzetta Ufficiale n. 42 del 20 febbraio 2018 - Serie generale (2018).

[12] Circolare n.7 del 21.01.2019 Istruzioni per l’applicazione dell’Aggiornamento delle «Norme tecniche per le costruzioni» di cui al D.M 17 gennaio 2018. S.O. alla Gazzetta Ufficiale n.35 del 11 febbraio 2019 - Serie generale (2019).

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Scipediacontent: Scipediacontent moved page Draft Content 925257152 to P. Brugnera 2021a

Scipediacontent: Created page with "== Abstract == The saddle-shaped shells, or hyperbolic paraboloids, often joined together to form a pitched roof or an inverted umbrella, were used by many pioneers in struc..."