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Viene giustificata la scelta del numero 72 delle formelle come ricordo della scomparsa di Battista Sforza, di Battista Alberti e Giovanni Bessarione avvenuta nel 1472. Il confronto fra il contenuto delle formelle ed i primi 53 disegni del codice della B.A.V. Urb. Lat. 1377 permette di considerare due distinte fasi della composizione del fregio. Una prima stesura del fregio (con notevoli differenze stilistiche), viene identificata in continuità con l’idea dell’Alberti, esposta sugli zoccoli dei pilastri, dove sono esposti scudi romani con lance incrociate. In queste formelle Federico, come riconosciuto dal Bianchini, che l’ornamento più proprio di una tal fabbrica fossero gl’istromenti medesimi delle di lui vittorie, e del suo ingrandimento, ha la sua gente armata sulla quale si basa (sulla quale conta), rappresentata attraverso le loro armi, come se i suoi fossero pronti ad indossarle per seguirlo, come fossero quelle ben lucidate e lubrificate che si dice «sostassero» all’interno del portico del palazzo. Ci sono rappresentati, come direbbe Machiavelli : i fanti con lo scudo, i fanti con la picca, i capidiedi colla picca, i capidiedi con lo scudo, i veliti ordinari, i veliti straordinari, i centurioni, i centurioni delle battaglie, il capo del battaglione, il capitano generale, il suono, la bandiera, gli uomini d’arme, i cavalli leggeri, l’artiglieria. Accostando le idee neoplatoniche alla colta corte urbinate, si scoprono le sequenze evolutive del pensiero materializzate nella evoluzione delle macchine e si portano argomenti per comprendere lo studiatissimo disordine proprio della stesura di questa così pioneristica opera d’arte.

Straw bale construction is a building technique offering many advantages: it provides excellent hygro-thermal insulation; it ensures good performance against earthquakes; and it is sustainable. From a mechanical point of view, straw bales can act as a surviving cell for the building in case of calamity. For this reason, measuring the mechanical properties of straw bales is important for the comprehension of the behaviour of straw bale buildings. Despite the fact that the use of straw bales in construction has been constantly increasing since the ‘80s, the behaviour and the performance of straw bale buildings have not been fully assessed so far. Using a recently developed test methodology (Maraldi et al., 2016), an analysis of the performance of small prismatic straw bales under monotonic compressive loads has been conducted. Force-displacement curves obtained from the tests have been fitted with a two-parameter rheological model to extract bales performance indicators. Results show that bales laid flat are stiffer than bales laid on-edge. However, if the influence of bales initial geometry is disregarded by considering stress and strain instead of force and displacement, no difference in the elastic modulus between flat and on-edge orientation appears. Furthermore, bales stiffness and elastic modulus are dependent on the initial density of the bale. It has been also found that straw bales exhibit a typical deformation pattern which depends on the baling process and that the Poisson’s ratio does not remain constant along the longitudinal direction during loading, whereas it is null along the transverse direction.

From the point of view of environmental awareness, construction sustainability is a theme that is gaining considerable attention. This has brought to a re-discovery of the use of straw as a construction material, a technology that has been widely used in the past centuries. Straw is a natural material having excellent insulating capabilities, considerable mechanical properties when packed in bales and is relatively low cost (it is indeed a by-product of farming activity). Two are the techniques adopted in straw bale construction: post-and-beam, where the load is sustained by a wooden frame and straw bales are used merely as infill material; and load-bearing, where the entire load is sustained by the plastered straw bale walls. Especially regarding the latter technique, there is a need for a deeper understanding of the mechanical properties of straw bales. The characterization of the material is made difficult by the variability brought about by the variety of plants from which straw can be obtained, unpredictability of the baling process, moisture content in the bale and other parameters. Moreover, there is not a standard regulating the productive chain of straw bales to be used for construction. In this paper, a literature review on the tests performed on single unplastered straw bales is conducted and, based on this, some ideas are proposed for the development of a model describing the mechanical behavior of straw bales.

In this study we show that the key to understand why the same salt can cause damage in some conditions and not in others is the kinetics of re-crystallization. Salt contaminated porous materials are known to deteriorate with environmental fluctuations causing the weathering of rocks and buildings. Salts can be naturally present in the materials used for construction (such as mortars and bricks) or can derive from external sources (capillary rising ground water, eolian origin, sea water along rocky coasts, and atmospheric pollution). With the variation of outdoor climate such as relative humidity, temperature or rain, the entrapped salt crystals can form again a salt solution after contact with liquid water (dissolution) or with water vapor (deliquescence). The so formed salt solution is subsequently mobilized in the porous network and re-crystallizes with drying. We present both macroscopic and microscopic experiments assessing the recrystallization dynamics of NaCl in sandstone with wetting/drying and humidity cycling. Advanced techniques such as high resolution X-ray computed tomography and Scanning Electron Microscopy are used to study the recrystallization process in the porous network in parallel with the drying kinetics. Our results show that recrystallization following deliquescence and dissolution leads to very different crystallization patterns. With humidity cycling, recrystallization promotes the formation of localised bigger cubic crystals at the subsurface of the stone whereas rewetting leads to efflorescence in the form of large localised cauliflowers at the surface. The different growth dynamics have direct consequence on the drying behaviour of the sandstone and its deterioration. This work is part of the European Project KISADAMA, a JPI- Cultural Heritage : Joint Heritage European Programme.

Over the last thirty years, the use of strawbales as a construction material has re-gained a lot of popularity for several reasons: baled straw has superior thermal insulation properties; buildings made with straw-bales are less expensive; straw is a by-product, hence its usage can help reduce the costs and emissions related to its disposal; structures built with strawbales can resist earthquakes better than those built according to traditional techniques. In the context of using materials and techniques sustainable for the environment, strawbale construction appears a more than promising choice establishing a strong link with the territory as well. Indeed, straw has been extensively used as a construction material since pre-history; more recently, strawbale houses were built in Nebraska at the end of the 19th century. The use of strawbales in construction returned popular in the late 80's (King, 2003); in some countries, this has been also supported by the development of design standards. In Italy, the lack of similar codes represents an obstacle; the procedure to have a design approved is tedious and discourages builders. In spite of this, however, strawbale houses have been and are currently being built. A deep understanding of the mechanical behavior of straw and of the material typically used in the rendering of strawbale walls is crucial for the development of construction techniques employing load-bearing strawbale walls. In the literature, studies on the mechanical properties of strawbales and strawbale assemblies have appeared since the rediscovery of this construction technique (Zhang, 2000; Vardy, 2009). Such studies report results of experimental tests conducted on single bales and on stacks of multiple bales, plastered or unplastered, loaded both on-edge and flat. However, very few of them provide some modeling to substantiate the results. In this paper, a review of the relevant literature regarding the mechanical properties of single unplastered straw bales is proposed and critically analyzed in order to provide guidance for future modeling; furthermore, the procedure for a comparative LCA between the options of building with conventional materials and with straw bales is sketched out and preliminary results of such an analysis are discussed.