Shape and construction of brick vaults. Criteria, methods and tools for a possible catalogue

The use of cloister vaults in the construction of noble buildings, as covering elements for square or rectangular rooms, is widespread and well-known. The geometric continuity at the intrados makes generally possible the execution all over the span of frescoes, stucco and decorations. The construction of brick vaults, from the late Middle Age, was sped up by limiting the centering to the wooden planks arches that were instrumental in the profile determination. Nowadays, the availability of several procedures, phases and tools for carrying out a survey allows to draw reliable assumptions about the construction methods and the execution time. It is mandatory to determine the properties of the binders, the shape and dimensions of the bricks, and to carry out a comparison between the geometry of the intrados surface and the evidences emerging at the extrados. The support of the laser scanner technique allows to accurately identify the surface profile and thickness. All these indications, in turn, are useful, in view of an interpretation of the structural behavior, to identify weaknesses, and to highlight contributing factors of instability (if any). In addition, Italian culture lacks systematic studies that indicate a reliable common pattern among the different types of vaults. Similar intrados shapes are often characterized by radically different patterns that are rarely taken into account from the structural point of view. The culture of stereotomy, in France and Spain, takes this interpretation of vaults for granted, while more systematic studies, in German-speaking countries, offer a broad and solid framework. The Italian technical literature was in Modern Age relatively scarce and showed limited attention to structural problems, and this fact contributes to widen this gap. Providing a variety of accurate surveys, aware of the aforementioned framework and the related shortcomings, will enable to overcome them. As a matter of fact, an element like the vault characterizes the Italian built heritage, but in the structural analysis there is often an oversimplification of some geometrical properties, limited to hurriedly measure thicknesses and intrados profiles, something that may lead to wrong conclusions. The paper focuses on a well-documented case, the Magio Grasselli palace in Cremona, where late medieval existing buildings were partially dismantled and modified in a modern aristocratic palace, designed by architect Francesco Pescaroli starting after 1658 until the end of the century. However, only the part of the building facing the main street and the part of the room overlooking the inner court were completed. The construction was resumed only after 1760: the wing facing the court and garden was completed, and all the rooms of the main floor, including the entrance hall, were covered with cloister vaults. Later on, the part of the building overlooking the main street was transformed. Here also, five rooms facing the street were vaulted, but only the central room, entirely painted by Giovanni Manfredini (1785), was completed, while three other unfinished rooms were subdivided in the Nineteenth century. The cloister vaults of two main rooms show different construction systems, although they were built almost at the same time. In the one overlooking the court, the bricks were laid on edge in concentric rows that seem parallel to the walls of the room, but are slightly arranged upwards. The irregularities are compensated by the longitudinal key joints. Wall-ribs systems at the extrados (the so-called Italian frenelli) connected to reinforcing arches, which could have served as base framework, contribute to the global stability of the structure. Thus, the vault seems to be constructed without continuous centering. Again, the large dimensions and the almost square shapes of the room overlooking the street suggest a construction through subsequent phases. Here the arches, visible from the extrados, were the centering outlining the profile of the vault, and enabled to build it without the support of planks. In order to understand the similarities and differences, the construction techniques and the state of damage of the two halls vaults, an integrated survey using laser scanners, photogrammetry and thermographic investigations was carried out. Such a survey allowed understanding the vault morphology and the masonry pattern, highlighting certain critical aspects of the structural elements, the kind of instability and decay, and the crack patterns mechanisms. More in detail, the three-dimensional model of the intrados of the hall, obtained from the laser scanner clouds, has been integrated with the three dimensional model of the masonry pattern, visible from the extrados, obtained from an elaboration of photogrammetric images. The current structure is a frame vault, characterized by two large and respectively transverse and longitudinal arches which divide the surface in nine squares and support thinner vaults, made of tiles (3-5 cm), widely used since the Sixteenth century. The investigation of easily detectable extrados parts makes a deeper knowledge of such constructions possible: it allows a better interpretation of recurring situations, even more problematic to be detected. This interpretation, however, cannot be carried out without an accurate survey integrated by thermography that can be extensively used at the intrados surfaces. In addition, the patient reconstruction and understanding of a constructive richness, made of recurrent elements and specific features, allow sketching a mixed pattern of workers and constructive knowledge. This process may result into current geographical updatable abaci, such as the French repertoires; from the point of view of innovation, it could lead to BIM libraries of vaulted elements that should be, however, not aimed at flattening and oversimplifying these valuable items to a unique parametric matrix, “copy-and-pasteable” at will, with mere changes of dimensions. Unfortunately, an oversimplification of complex elements (such as vaults) is the rule in the application of BIM to the cultural heritage. This oversimplification is the demonstration of incomplete knowledge and deviate interpretation of BIM that should be used, on the contrary, to better handle differences and peculiarities. Through the concept itself of instances consisting of unique and complex elements, “hic et nunc” to every object, the families are enriched; what is different is the point of view that should be aimed not at unifying, but at the comprehension and rendering of the acquired knowledge. As testified by some recent experiences, BIM models support this different approach to modeling, although still in a rather complex way (even if the rendering of a complex model is always complex). The availability of a detailed three-dimensional model allows a backward knowledge of the construction technique, maybe not in its entirety, but sufficient enough to explain and highlight that the provision and use of centering in the constructive phase, as previously mentioned, “changes” the geometric shape by creating multiple variations. The archival, metric and thermographic information concerning the Magio Grasselli palace are abundant and considerable, and are integrated with the plurality of data, essential to define an elevated standard of documentation, which allows to justify both detailed hypotheses on the construction techniques, and classification criteria. It is important, however, to subject the whole to a critical examination, in order to define principles effectively shared and aimed at building a reference system, whose absence was already pointed out

THE HBIM ANALYSIS OF THE GEOMETRY TO UNDERSTAND THE CONSTRUCTIVE TECHNIQUE: THE USE OF THE <i>TROMPE</i> VOLUME IN A BRICK VAULT

The construction of brick-vaulted systems between the 16th and 18th centuries is a typical mark among the noble buildings in large part of Northern Italy. Nowadays they are still a witness of a high level of constructive knowledge by workers, formalized in historical treatises and manuals supporting a literature of theories and practices known since ancient times. The way a vault is geometrically built, regardless of its typology, is not unique and it differs in treatises, according to its location in time and space. The consequence is the generation of “mixed” solutions, where the result of the final volume is achieved by the integration of different generative models and spatial solutions. The observation of cloister vaults, apparently similar to each other but built adopting different constructive techniques within a single building, Magio Grasselli Palace in Cremona, helped to understand this topic

The role of structural survey in the geometrical analysis of historical constructions: Damaged mechanisms or constructive techniques?

Nowadays it is well known that the in-depth process of knowledge plays a key role in the field of cultural heritage. This knowledge should objectively allow identifying both the several structural elements and their mutual connections, both the quality and the state of damage of the materials characterising the case study. The final goal is the evaluation of the safety level of historical constructions. In some cases, the lack of documentation or, in some other cases, the incompleteness of the information provided by the existing documents, until the discrepancy between the design and the real construction, lead to obtain information by means of the direct analysis of the building. The structural survey, hence, which belongs to the broader topic of the structural diagnostics, becomes a tool that allows interpreting geometries and damages. A tool able to adapt to the several peculiarities of historical constructions and to address the investigation techniques to the specific problems. In this way, it is possible to define the state of damage, its causes, the safety level and to the select the most appropriate strengthening techniques to repair and improve the building structural behaviour. The comparative analysis of some case studies allows highlighting a wide range of situations that forces to consider each building as a unicum (although recurring constructive typologies are present). To this aim, specific investigation techniques and processes are required as well as an interdisciplinary approach, with the involvement of expertise coming from several fields. Contrary to what was believed in the past, safety and conservation are not antithetic concepts, but it is possible to guarantee a harmonic union between them by means of the structural survey as well

Towards a semantic based hub platform of vaulted systems: HBIM meets a GEODB

In the last years many efforts have been invested in the cultural heritage digitization: surveying, modelling, diagnostic analysis and historic data collection. Nowadays, this effort is finalized in many cases towards the Historical Building Information Modelling. The number of informative models testifying the multifaceted richness and unicity of the architectural heritage and its components is progressively increasing. Information and Model are generally acquired under researches and analysis phases addressed to the preservation and restoration process. Unfortunately, once concluded the research such documentation is mostly left abandoned in the drawers or in the local memory of the computers, and in some cases totally missed. Just a few of them are saved in a server or in the cloud for the duration of the restoration, but without any connection with the maintenance process of historic architectures or knowledge transfer purposes and dissemination. This data loss would lead to the breaking of the cycle of past, present and future, with loss of memory and knowledge. The paper start facing the aspect of managing the information and models acquired on the case of vaulted systems. Information is collected within a semantic based hub platform to perform cross co-relation at a PanEuropean level. Such functionality allows to reconstruct the rich history of the construction techniques and skilled workers across Europe, enriched by 3 case studies surveyed in Prague region. To this purpose a Vault DB has been undertaken with a Vocabulary enriched by the granular information gained from the HBIM models, and with the vault sub-Typologies highlighted by a detailed surveying

STRUCTURAL ANALYSIS OF A RESTORED BYZANTINE MONASTERY: EFFECTIVENESS OF THE INTERVENTIONS

The effectiveness of the restoration interventions carried out on the Byzantine monastery of St. Nicholas at Mesopotam, Albania, is discussed. The interventions aimed at consolidating the church, while bringing it back to its original conditions. Two finite element models were developed: one describing the church as it was until 2009, and one after the planned intervention. The models try to reproduce as accurately as possible the main geometric details of the building, and take into account the macroscopically orthotropic behaviour of masonry and the main cracks. Linear elastic analyses of both models were carried out considering gravity loads and lateral loads equivalent to seismic actions according to the Italian standards. The numerical results show that, in the occurrence of an earthquake, the stress in the building would considerably increase after the restoration interventions. In particular, removal of a buttress turns out to be an operation controversial, not to say detrimental

Indagini strutturali sulla Basilica di Santa Maria Novella

The present work describes the preliminary results of structural analyses carried out on a finite element model of the Basilica of Santa Maria Novella in Florence, aiming at assessing the current conditions of the Basilica and interpreting the surveyed crack pattern. The information gathered in a previous survey campaign (exact geometry of the vaults, crack pattern, and out-of-plumb of the columns and the walls) were employed to define a numerical model that matches the salient features of the real geometry of the Basilica, despite some simplifying assumptions. So far, linear elastic analyses taking only the self-weight of the structural elements into account, were carried out. Despite these limitations, the faults observed in the vaults of the lateral naves and in the perimeter of the transept could be explained. The agreement between numerical predictions and cracks detected in other parts of the Basilica, such as the vaults of the central nave and the transversal walls above this nave, is less satisfactory. Future analyses will include the effects of ground settlements and the out-of-plumb of the pillars of the central nave

identifying fault inducing phenomena in an old masonry building

Abstract The structural behavior of a masonry farmhouse exhibiting several faults is investigated. The building has an irregular plan, which is probably the outcome of different construction phases; the oldest part dates back to the seventeenth century. The building underwent several interventions of consolidation, including the addition of ties, a buttress, and micropiles. Despite these interventions, the building is still heavily damaged, with vertical and inclined deep cracks. A static monitoring system was installed to track the major cracks for a duration of 18 months: some were found to be still propagating. Interpretation of the crack pattern allows the causes that originated the main faults, including changes in geometry, to be better understood. An in-depth analysis on the building also allows some geometric anomalies to be highlighted. These anomalies can probably be traced back to the different construction phases, and locally weaken the structural strength. A detailed finite element model, taking the properties of the different materials into account, was developed. The main cracks existing in the building were also included in the model. Structural analyses were carried out taking gravity loads, ground settlements, and possible seismic actions into account. The tensile stresses in some parts of the building are found to be sufficiently high to induce further crack growth. The numerical results are used to propose simple retrofitting strategie

Difficulties in the design for conservation of archaeological remains: the G1 Temple in My Sơn

To apply conservation principles to archaeological remains is a difficult task especially when they are at a state of ruins due to destructive events like earthquakes, floods, storms, etc. or, even worse, to wars. This was the case of the Hindu temples of the archaeological site of My Sơn (Vietnam); the temples were built by the Cham people from the 5th to the 14th century a.C., partially destroyed during various invasions from China and during wars between Chams and Kmers and finally badly damaged by shells during the Vietnam war. The authors will describe their experience and try to draw some guidelines for the conservation design of these peculiar structures also in other Vietnamese sites