PRECAST REINFORCED CONCRETE ELEMENTS CONNECTED THROUGH BARS IN SHAPE MEMORY ALLOY: MODELLING AND ANALYSIS

Abstract This work of research investigates the behaviour of a particular beam-to-column connection of precast reinforced concrete (PRC) frames, through a finite element model with the aim of evaluating the possibility of substituting the standard structural steel with shape memory alloy bars. The results of an experimental study carried on by the UTCN Structures Dept. have been used to run a displacement-imposed pushover analysis, in order to plot the total base shear force versus top displacement graph of the structure, with the aim of indicating any premature failure or weakness. Despite the brilliant characteristics of the smart materials such as strain recovery and superelasticity, the configuration proposed has not sufficient rigidity for bearing the cyclic loading and undergoes the imposed deformation rapidly having the concrete bodies to reach the tensile stress: as constrained and in the present configuration the connection proposed does not fulfill the expectations for this material. Despite the high cost could represent a barrier for keeping on exploring the possibilities of its use, many challenges could be faced, playing with the different parameters involved or empowering the model with a damage-plasticity approach able to map the evolution of cracks and completely describe the failure of the concrete. Riassunto Il presente lavoro di ricerca ha lo scopo di indagare il comportamento di un particolare giunto trave-colonna in una struttura prefabbricata in cemento armato, attraverso la costruzione di un modello agli elementi finiti con cui valutare la possibilità di sostituire l’accciaio strutturale standard con barre a memoria di forma. I risultati di uno studio sperimentale avviato nell’amibito del Dip.di Strutture dell’ UTCN sono stati utilizzati per operare un’analisi push-over in controllo di spostamento, al fine di plottare un diagramma che mettesse in relazione il taglio alla base con lo spostamento in cima alla struttura, con lo scopo di indicature premature crisi o debolezze. Nonostante le brillanti caratterische dei cosiddetti “smart materials”, quali la superelasticità o la capacità di recuperare le deformazioni, la configurazione proposta non presenta sufficiente rigidezza nel sostenere un carico ciclico e incassa le deformazioni imposte al costo del raggiugimento della resistenza a trazione nel calcestruzzo: nella presente configurazione e con tale grado di vincolo, la connessione proposta non soddisfa I requisiti richiesti. Sebbene il costo possa rappresentare un ostacolo all’approfondimento delle possibilità di applicazione, molte sfide restano aperte, variando I parametri in gioco o meglio, potenziando il modello con un approccio di tipo damage-plasticity che possa mappare l’evoluzione delle fessure e abbia la capacità di descrivere completamente la crisi lato calcestruzzo

influence of mechanical parameters on non linear static analysis of masonry buildings a relevant case study

Abstract In seismic zones, suitable procedures to assess the seismic vulnerability of existing buildings are necessary also in view of optimal planning of interventions. Starting from the agreement between the Municipality of Florence and the Department of Civil and Industrial Engineering of the University of Pisa, a research program is ongoing, devoted to setup a simplified, fast but reliable procedure for the evaluation of seismic performance of masonry buildings. In this paper, a simplified non-linear pushover type method for the verification of unreinforced multi-story masonry buildings with both deformable and non-deformable slabs is presented, starting from some of the basic assumptions of the POR method. Various tests on the procedure show that the method is able to give results that are comparable with those obtained by the classical pushover analysis performed on equivalent frame models. The intuitiveness of the method and the low computational effort required by the new algorithm allow the evaluation of the sensitivity of non-linear static analysis regarding the definition of mechanical parameters. In particular, the relevant influence of the modulus of elasticity as well as the ultimate inter-story displacement assumed for masonry walls on the assessment of seismic performance are discussed in detail. The results are presented for a significant case study, the Primary School "G. Carducci" in Florence, a four-story masonry building, with a horseshoe layout where lateral appendixes detached from the central block

shear modulus of masonry walls a critical review

Abstract In the assessment of seismic performance of masonry buildings, the proper definition of mechanical parameters of masonry, the shear modulus in particular, is a critical issue. Moreover, considering that existing buildings are characterized by several masonry types, depending on the material as well as on the texture, mechanical parameters can vary in a very wide range, also because they depend on many other parameters and in particular on the integrity of the walls and on the stress level. Although the in situ or laboratory experimental evaluation of the G modulus has been the subject of a wide literature concerning flat jacks, diagonal and single compression and shear-compression test results, its outcomes are often contradictory. In effect, values given by different studies often differ significantly, even for the same class of masonry. Since the intrinsic scattering of the parameter is not sufficient by itself to justify the huge variability of the results, a critical discussion of the results as well as of the individual test arrangements is necessary to make the background more reliable, also in view of better addressing further studies- A huge database has been setup combining masonry test results available in the relevant scientific literature with the test results obtained in the framework of the in situ experimental campaign carried out by the authors for the assessment of seismic vulnerability of masonry school buildings in the Municipality of Florence. The analysis of the database underlines that values of the shear modulus G, which is a fundamental parameter for the definition of capacity curve for walls commonly used in non-linear static analysis, are extremely scattered. Testing methodology and arrangement are discussed and a possible procedure is proposed to arrive to sounder estimations of relevant mechanical parameter of existing building masonry

Influence of shear modulus and drift capacity on non-linear static analysis of masonry buildings

In nonlinear static analysis of masonry buildings, the hysteric behaviour of masonry walls is commonly idealized through a bi-linear resistance envelope defined by the lateral stiffness of the wall, the ultimate shear resistance and the ultimate inter-storey drift. Therefore, it becomes fundamental to properly set the modulus of elasticity and shear modulus for masonry as well as to properly evaluate the drift capacity of the walls. In the paper, the combined influence of shear modulus and drift capacity definition on the assessment of seismic performance of masonry buildings is investigated in details by means of a simplified non-linear pushovertype algorithm developed bythe authors. In particular, two different definitions are considered for the drift capacity, in terms of ductility and in terms of percentage of the inter-storey height, while for the shear modulus a reasonable set of values is investigated according a database collected combining masonry test results available in the relevant scientific literature with an in situ experimental campaign carried out by the authors. The results show how the variation in shear modulus can lead to conflicting outcomes for the evaluation of seismic performance of masonry buildings depending on the assumed definition of drift capacity

Non-linear static analysis of masonry buildings under seismic actions

Assessing existing masonry building in seismic zones is a critical issue, due to the high vulnerability of the built environment. Commonly, beside local analysis, refined assessment procedures are used based on non linear static methods, like the pushover method, supplemented, if necessary, by dynamic linear analyses, devoted to check the order of magnitude of the results. In non-linear static analysis masonry buildings are mostly modelled using the so-called equivalent frame model, but the resulting structural scheme is usually very complicted and the analysis requires to be "driven" step by step by very skilled users in order to obtain consistent results. An innovative and "robust" method is proposed for non-linear static analysis of masonry building. The method, which relies on very simple structural models, nearly independent on the user, recovers some basic assumptions of the classical POR method, and can be applied to mono or multi-story masonry buildings. Comparing the results obtained with the proposed method with those derived using the classical pushover analysis in several relevant case studies, allowed to validate it. Moreover, the practical applications confirmed that the method is suitable for refined assessment of the seismic performance of the structure, with a limited computational effort, so making possible also extensive sensitivity studies

Valutazione speditiva della vulnerabilità sismica di edifici esistenti su un campione statistico costituito dagli edifici scolastici del Comune di Firenze

In forza di una convenzione stipulata fra il Comune di Firenze ed il Dipartimento di Ingegneria Civile e Industriale dell’Università di Pisa, è stata avviata un’attività di ricerca per mettere a punto una metodologia speditiva per la valutazione della vulnerabilità sismica degli edifici con struttura in muratura o mista muratura-cemento armato. La metodologia è sperimentata su un campione molto numeroso, costituito dal patrimonio comunale di edilizia scolastica, per il quale è necessario individuare le priorità d’intervento e conseguire livelli di prestazione conformi alla Norma Tecnica di riferimento. A tal fine, è stata preliminarmente individuata una procedura da seguire, che riserva grande rilevanza alla fase di conoscenza dell’edificio, dalla sua anamnesi storica alle prove in situ: con martinetti piatti (singoli e doppi), prove di estrazione, opportunamente riadattate per l’utilizzo sulla muratura, e prove di qualificazione di campioni di malta prelevati in loco. Nella memoria sono riportate informazioni dettagliate sulla procedura e i risultati delle prove finora effettuate.Due to an agreement among the Comune di Firenze and the Department of Civil and Industrial Engineeringof the University of Pisa, it has been started a research project to assess the seismic vulnerability of the school masonry buildings belonging to the Comune di Firenze, in order to evaluate the priorities in retrofitting and achieve performance characteristics in line with the most updated structural Codes. Hence, it has been developed a procedure to be followed, focused on achieving information for a deep understanding of the building, starting from the historical inquiry to in-situ tests: single and double flat jacks tests, pull-out tests, properly adapted to masonry, and tests for evaluating the quality of samples of mortar extracted on site. In this paper, detailed information about the procedure will be given and the preliminary results of tests will be presented

Architettura e Museologia Liquida. Ricerca ideata e coordinata da Stefano Colonna Sapienza Università di Roma

L’Architettura Liquida rompe gli schemi simmetrici dell’Architettura Classica introducendo asimmetria, finestre disassate, pianta a zig zag, mancanza di una facciata propriamente intesa, corpi di fabbrica in aggetto e inversione degli spazî, dove i vuoti sono al piano terra invece che nei piani superiori, e si ispira alle geometrie non euclidee, ai frattali, allo specchio, al labirinto e anche a temi biblici del mostro, come nel caso di Giona e la balena reinterpretati in chiave laica. Il primo a ideare l’etichetta di Architettura Liquida è stato Marcos Novak nel 1991, ma Giulio Carlo Argan già nel 1930, in un importante articolo apparso nella rivista L’Arte, interpreta come “germi” del cosiddetto codice Anti-classico i presunti “errori” di Andrea Palladio evidenziati da Francesco Milizia nel Settecento. Seguiranno altri due libri di Argan e di Bruno Zevi, dedicati al codice Anti-classico, dove si evidenzia anche il carattere politico dell’Anti-classico in opposizione alla “dittatura della linea retta” usata dai regimi. Partendo dunque dalla consapevolezza che l’Anti-classico è precursore del liquido, il volume offre alla pubblica discussione saggi teorici, interpretazione analitica di alcuni edifici e musei liquidi particolarmente rappresentativi e un’Antologia di opere di Architettura e Museologia Liquida a partire dal 1989 (prima Architettura Liquida), con antecedenti dal 1906, disponendole in ordine cronologico per una migliore storicizzazione di questo importante movimento architettonico e culturale internazionale i cui edifici sono ancora “in fieri”.Liquid Architecture breaks the symmetrical schemes of Classical Architecture by introducing several innovations like as: asymmetry, offset windows, a zigzag plan, lack of a properly understood facade, overhanging buildings and inversion of spaces, where the voids are on the ground floor instead of in the upper floors. It is inspired by non-Euclidean geometries, fractals, the mirror, the labyrinth and even biblical themes of the monster, as in the case of Jonah and the whale reinterpreted in a secular key. The first to invent the Liquid Architecture label was Marcos Novak in 1991, but in 1930 – in an important article appeared in the magazine L’Arte – Giulio Carlo Argan already noticed the alleged “errors” of Andrea Palladio – highlighted by Francesco Milizia in the eighteenth century – as “germs” of the so-called Anti-classical code. Besides, two other books written by Argan and Bruno Zevi, dedicated to the Anti-classical code, highlight the political character of the Anti-classical, as opposed to the “dictatorship of the straight line” used by the regimes. Starting therefore from the awareness that the Anti-classical is a precursor of the liquid, this volume offers to the public discussion theoretical essays, analytical discussion of some particularly representative liquid buildings and museums and an Anthology of Liquid Architecture and Museology works, starting from 1989 onwards (first Liquid Architecture), with antecedents from 1906, arranging them in chronological order for a better historical interpretation of this important and international architectural and cultural movement whose buildings are still “in fieri”