Settlements of foundation are the most common and frequent cause of damage in ancient buildings. This problem is accentuated if it refers to differential settlement in masonry structures. Because of their high stiffness this kind of fabric is fragile and therefore it cracks immediately at the beginning of the settlement, even if the damage led to dangerous state only in few cases. The settlement provokes a redistribution of forces between the structure and the foundation soil, with a reduction where the settlement happened and an increment in adjacent foundation elements. In general, before this attenuation occurs, the external load could have induced tensional states enough high to exceed the strength limit in some parts of the structure. The consequence is the formation of plastic hinges, damages and crushing. The target of this thesis is to produce a global structural analysis of an ancient masonry building, using as study case the San Bassiano’s church in Pizzighettone (CR). This approach is chosen because it permits to study the global interaction between the structural elements, an aspect that an analysis by parts could not highlight. First the theoretical models of the behaviour of each structural element are presented, then the study case and its 3D modelling in AutoCAD are introduced. The geometrical information extracted from the CAD model is used as the base for the preliminary analysis. In this first analysis the configuration of static balance of the structure is studied to have a first estimate of the forces exchanged between different elements. Then, a state of settlement analysis is conducted following an integrated method, which consist in an evaluation of the variation of the joint reaction using the damage pattern of the structure. Then the response of the soil is estimated in both the configurations and the safety coefficient for the bearing capacity is calculated. In the end, a proposal of consolidation of the foundation system is suggested to improve the stability of the structure.
I cedimenti delle fondazioni sono tra le cause più frequenti dei dissesti degli antichi edifici. L’elevata rigidezza delle strutture murarie rende particolarmente sensibili questo tipo di costruzioni all’influenza di cedimenti differenziali delle strutture di fondazione, anche se le lesioni conducono solo in alcuni casi ad effettive situazioni di pericolo. L’effetto del cedimento è una redistribuzione delle azioni mutue terreno-struttura, con una riduzione delle reazioni vincolari dove i cedimenti sono maggiori ed un incremento dove sono minori. In generale però, prima che questo effetto di attenuazione entri in atto i carichi agenti possono aver indotto stati tensionali tali da superare in alcune zone i limiti di resistenza del materiale con formazione di “cerniere”, lesioni o schiacciamenti. L’obbiettivo di questa tesi è produrre un’analisi strutturale globale su un edificio storico in muratura riferendosi ad un caso reale, la chiesa dedicata a San Bassiano a Pizzighettone (CR), valutandone l’utilità rispetto ad analisi per parti. Dopo aver presentato i modelli specifici per la descrizione del comportamento di ogni elemento strutturale e la creazione del modello geometrico tridimensionale si è studiata la configurazione di equilibrio statico della struttura. Riconoscendo l’entità dei cedimenti in atto e visto l’esteso quadro fessurativo, si è quindi impostata un’analisi in stato di cedimento secondo un approccio integrato, ovvero utilizzando le informazioni leggibili dal quadro fessurativo, con lo scopo di valutare le variazioni delle reazioni vincolari della struttura. Viene infine proposta una linea di intervento per il consolidamento delle strutture di fondazione.
Analisi strutturale e proposta di rinforzo delle fondazioni di un edificio storico. Il caso di studio della chiesa di San Bassiano a Pizzighettone
BERTOLLI, CAROLINA
2017/2018
Abstract
Settlements of foundation are the most common and frequent cause of damage in ancient buildings. This problem is accentuated if it refers to differential settlement in masonry structures. Because of their high stiffness this kind of fabric is fragile and therefore it cracks immediately at the beginning of the settlement, even if the damage led to dangerous state only in few cases. The settlement provokes a redistribution of forces between the structure and the foundation soil, with a reduction where the settlement happened and an increment in adjacent foundation elements. In general, before this attenuation occurs, the external load could have induced tensional states enough high to exceed the strength limit in some parts of the structure. The consequence is the formation of plastic hinges, damages and crushing. The target of this thesis is to produce a global structural analysis of an ancient masonry building, using as study case the San Bassiano’s church in Pizzighettone (CR). This approach is chosen because it permits to study the global interaction between the structural elements, an aspect that an analysis by parts could not highlight. First the theoretical models of the behaviour of each structural element are presented, then the study case and its 3D modelling in AutoCAD are introduced. The geometrical information extracted from the CAD model is used as the base for the preliminary analysis. In this first analysis the configuration of static balance of the structure is studied to have a first estimate of the forces exchanged between different elements. Then, a state of settlement analysis is conducted following an integrated method, which consist in an evaluation of the variation of the joint reaction using the damage pattern of the structure. Then the response of the soil is estimated in both the configurations and the safety coefficient for the bearing capacity is calculated. In the end, a proposal of consolidation of the foundation system is suggested to improve the stability of the structure.File | Dimensione | Formato | |
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https://hdl.handle.net/10589/146992