1,721,147 research outputs found
Modellazione a telaio equivalente di strutture esistenti in muratura e miste muratura-c.a.: formulazione di modelli sintetici
No full textFormulazione di elementi non lineari per l’analisi degli edifici esistenti a struttura mista muratura-c.a.
No full textAnalisi non lineari per la simulazione del danno di un fabbricato in San Felice sul Panaro (Emilia, 2012)
No full textNell’articolo è illustrata la simulazione numerica della risposta sismica di fabbricato sito in San Felice sul Panaro che ha subito danni significativi a seguito del terremoto che ha colpito l’Emilia nel Maggio del 2012. La simulazione è eseguita adottando l’approccio di modellazione a telaio equivalente tramite il software Tremuri (Lagomarsino et al. 2012) e svolgendo analisi non lineari statiche e dinamiche. Il confronto con il danno reale occorso e il potersi avvalere di una caratterizzazione della domanda sismica basata su registrazioni reali costituiscono un elemento fondamentale per potere validare i risultati ottenuti nonché, più in generale, l’attendibilità degli strumenti impiegati per la valutazione della sicurezza sismica del costruito in muratura. I risultati evidenziano una notevole accuratezza degli strumenti proposti nella capacità di previsione della risposta sismica
Seismic assessment of mixed masonry-reinforced concrete buildings by non-linear static analyses
No full textSince the beginning of the twentieth century, the progressive and rapid spread of reinforced concrete (RC) has led to the adoption of mixed masonry-RC solutions, such as the confined masonry. However, together with structures conceived with a definite role for earthquake behaviour, the spreading of RC technology has caused the birth of mixed solutions inspired more by functional aspects than by structural ones, such as: internal masonry walls replaced by RC frames, RC walls inserted to build staircases or raising made from RC frames. Usually, since these interventions rise from a spontaneous build-up, any capacity design or ductility concepts are neglected being designed only to bear vertical loads: thus, the vulnerability assessment of this class becomes crucial. To investigate the non-linear seismic response of these structures, suitable models and effective numerical tools are needed. Among the various modelling approaches proposed in the literature and codes, the authors focus their attention on the equivalent frame model. After a brief description of the adopted model and its numerical validation, the authors aim to point out some specific peculiarities of the seismic response of mixed masonry-RC structures and their repercussions on safety verification procedures (referring in particular way to the non-linear static ones). In particular, the results of non-linear static analyses performed parametrically to various configurations representative of different interventions are discussed
Performance-based approach to earthquake protection of masonry cultural heritage
No full textWithin the framework of Performance Based Assessment (PBA), the paper focuses on the implementation to the case of ancient masonry constructions. Actually, the complexity and wide variety of historical masonry buildings (such as churches, palaces, towers, columns, etc.) require the adoption of different modelling strategies, through a versatile procedure. Within this context, one of the main issues is the definition of performance levels on the capacity curve, provided by the nonlinear pushover analysis. Firstly, performance objectives have to be defined also considering cultural relevance concepts: thus, the preservation of the cultural heritage asset and the safety of the people using it should be considered in an integrated approach. To this aim, in the paper, a multicriteria approach to define damage levels is proposed by considering: a) the damage at the scale of structural element (local damage), b) the mechanisms in architectonic elements (macroelement), c) the global behaviour of the building (represented by its pushover curve). Then, proper criteria are established to correlate damage at the three scales and define performance levels on the capacity curve
Modelling the seismic response of unreinforced existing masonry buildings: a critical review of some models proposed by codes
No full textDistinctive features which characterize the existing unreinforced masonry building (such as the presence of flexible floors and/or weak spandrels) make the possibility of simulating the actual conditions of the structure crucial: indeed, models usually employed for new constructions are not always suitable for existing ones. Different strategies of modelling can be adopted with increasing levels of accuracy and computational effort. In this paper attention will be focused on very Simplified Models, such as “strong spandrel-weak pier” or “weak spandrel-strong pier”, and much more complex models such as “Equivalent Frame Model” proposing a critical review of their use and of the reliability of the assumptions which they are founded on. Particular attention will be paid to the issues related to the assessment of the in-plane strength of URM walls distinguishing between those related to the idealisation of the masonry wall in an equivalent model (e.g. geometry and boundary conditions assumed for each panel) and those related to the proper evaluation of the strength of each structural element, as defined by the previous step, on which the non linear response is concentrated (e.g. resistance criteria to be adopted distinguishing the case of pier from that of spandrel). In particular the fundamental role played by spandrel elements will be discussed
PERPETUATE guidelines for seismic performance-based assessment of cultural heritage masonry structures
No full textAncientmonumentalmasonry buildings are complex structures that were not based
on an engineered design, underwent many transformations during their life and often present lack of connections among the structural elements. Earthquakes are themain cause of damage for ancient masonry structures and, in order to reduce their vulnerability with compatible and light interventions, it is necessary to have accurate models for the seismic analysis, able to simulate the nonlinear behavior of masonry, and a well defined performance-based assessment procedure, aimed to guarantee the acceptable level of risk for the occupants and for the conservation of the monument itself. The paper outlines the guidelines that were developed within the PERPETUATE European research project. The wide variety of architectural assets is classified and the related proper modeling strategies are identified; moreover, immovable artistic assets are considered in the assessment. A displacement-based approach is adopted,
because these structures crack even for low intensity earthquakes and can survive severe ones only if they have a sufficient displacement capacity. Safety and conservation requirements are proposed by considering distinct sets of performance levels, related to use and safety of people, conservation of the building and of the artistic assets that might be present. Some indications on the seismic hazard assessment are provided, considering the distinctive features of some types of ancient structures. Within the fundamental knowledge phase, sensitivity analysis is proposed in order to address and optimize the in-situ investigation and to define proper confidence factors, aimed to consider epistemic and statistical uncertainties. Different
modeling approaches and methods of analysis are considered, depending on the characteristics of the structure; both static pushover and incremental dynamic nonlinear analyses are considered. Related verification procedures are defined to evaluate the seismic intensity measure, and the corresponding return period, which is compatible with each performance level that must be fulfilled
A methodology for the seismic risk mitigation based on mechanical models: the case of reinforced concrete school buildings in Genoa (Italy)
No full textRecent earthquakes have highlighted the potential seismic vulnerability of existing reinforced concrete buildings; not only in case of residential buildings but also strategic structures, such as schools or hospitals. Thus, a reliable vulnerability assessment at large scale becomes crucial in particular for public institutions to optimize the criteria to identify the priorities of intervention (priority lists) in order to better allocate the limited economic resources. Among the different approaches proposed in literature, the use of mechanical models seems particularly suitable to this aim. These models, being based on a limited number of geometrical and mechanical parameters, allow to describe the inelastic response of buildings by capacity curves. In the paper the attention is focused on the DBV-concrete model proposed in Lagomarsino et al. (2010) based on the displacement-based approach. It has been applied on the case of 55 schools of Genoa Province (North Italy). Results are compared to those provided by on observational vulnerability model in order to combine these different approaches for defining proper priority list
Non linear analysis of mixed masonry and reinforced concrete buildings
No full textFrom the early 20th-century the gradual transformation of the theory and constructive techniques led from the masonry buildings predominance to the reinforced concrete’s (RC) structures. Together with structures conceived with a definite role for the earthquake behaviour, the spreading of RC technology caused the birth of mixed solutions starting from existing structures in order to satisfy functional aspects: masonry structures subjected to internal demolishment, column insertions, RC staircases insertions, plan enlargements or raisings-up by mean of concrete structures. The structural variety is quite wide and the complex set of specific cases eludes the coded schemes: therefore subject of particular interest becomes the vulnerability of this class. Moreover, although there is a well-established background focused on the non linear analysis of masonry structures and RC frames, the set of numerical and experimental instruments for the study of the interaction effects is limited. In this paper, in the masonry’s idealisation as equivalent 3D frame (Galasco et al., 2004), a formulation and implementation of non linear elements is proposed in order to model RC columns, beams and walls. The adopted approach idealises the behaviour as elasto-perfectly plastic with limited resistance and plasticity concentrated at the end-element; the considered failure’s mechanisms are as follows: shear and axial stress as brittle failure and axial-bending as ductile failure. Some examples show the efficiency of this method and highlight the behaviour’s peculiarity of these structures
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