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Structural diagnostic
No full textThis report describes the results obtained by applying an extensive NDTs experimental investigation in order to evaluate the extent of structural damage and their causes.
A correct preservation design of a historic structure should start from an accurate diagnosis of the state of damage based on: experimental on-site and laboratory investigacions, and a structural analysis using the result of said invesùgations. These operations will enhance knowledge of the building and help respect its authenticity through an appropriate choice of intervention techniques.
The lack of knowledge about the originai materials and structures has frequently been the main cause of unsuccessful interventions. In this context a further problem was found, namely the modality of past intervention on the building with inappropriate techniques. The questions to be answered are: What actually caused the failures? How dìd they develop? and, How serious were theìr consequences to the overall response of the building?
Masonry structures in seismic areas are subjected to severa!earthquakes during their lifetime, often followed by partia1 reconstruccion. They can also suffer for lack of maintenance, so that synergetic effects can cause their damage. In order to overcome the gap between our poor knowledge and the complexity of these structures an experimental on-site investigation is required as well as recommended by the Codes and Standards of severa! countries.
Non-Destructive Techniques (NDTs) and/or Minor Destructive Techniques (MDTs) can be helpful in detecting hidden features (wall texture, internal voids and Aaws and characteriscics of the wall section), which are crucial to define the structural behaviors under dead loads and environmental action. Before choosing the appropriate NDTs, it is therefore important to know which type of problem has to be solved, i.e. what is to be found by NDT.
In the case of ND tests, a correlation between the measured parameters and the mechanical ones is usually difficult, but it can give an overall qualitative indication of the masonry. At present the most diffused ND techniques are sonic (or ultrasonic), radar and thermography tests. Sonic and radar tests seem to be very promising when a diagnosis has to be clone on the state of damage present in inhomogeneous materials; therefore the designer is asked to interpret the results and use them at least as comparative values betwecn different parts of the same structure'smasonry or by using different ND techniqucs
Interventi di mitigazione degli impatti ambientali: il caso dell'aeroporto intercontinentale di Malpensa 2000
No full textMesures of mitigation environmental impact: the experience of the intercontinental airport Malpensa 2000
No full text
APPLICAZIONI DELLA TOMOGRAFIA PULSE-ECHO ALL'INGEGNERIA CIVILE
Full text linkUno degli strumenti più innovativi attualmente disponibili per le indagini ultrasoniche su elementi in calcestruzzo è il tomografo A1040 MIRA, prodotto dalla Acoustic Control Systems di Mosca. Questo strumento è stato ideato per implementare sistematicamente la tecnica pulse-echo tramite una matrice di trasduttori a onde di taglio accoppiata ad un solo lato della struttura. Caratteristiche particolarmente interessanti di questo dispositivo sono i sensori puntiformi con accoppiamento a secco, l'implementazione automatica di sezioni tomografiche (scansioni B) tramite una specifica tecnica di focalizzazione e la possibilità di disporre dei dati grezzi acquisiti per l’implementazione di elaborazioni avanzate. Approfittando di quest'ultima opzione, gli autori hanno iniziato ad estendere l'uso di questo dispositivo ad alcuni problemi specifici al di là della semplice localizzazione dei vuoti. Un primo esempio è l'estrazione di informazioni quantitative sulla grandezza e sulla fase degli impulsi derivanti dai riflettori rilevati. Un'altra applicazione è la valutazione del danno superficiale dovuto all'esposizione al fuoco. L'ultimo esempio riguarda la ricerca dei difetti dominanti nei tiranti in ferro battuto con il metodo delle Onde Guidate. Qui i sensori adattabili a contatto puntiforme si sono rivelati molto efficaci nell'accoppiare lo strumento alla superficie irregolare degli elementi. Queste particolari applicazioni potrebbero rafforzare l'interesse per uno strumento diagnostico già affermato nel campo delle strutture civili
Dissesti statici.Controllo dell’evoluzione mediante monitoraggio del quadro fessurativo e rete di livellazione
No full textThermovision: applications in conservation field to detect hidden characteristics of building structures
No full textThermovision is applied in several fields of investigations and is a technique useful to control the range of temperatures emitted by different materials. In conservation thermovision is basely used to observe surfaces hidden by rendering or plaster. The information provided by thermographic tests can reveal the geometry of the masonry components and also the presence of defects such as discontinuities, layer detachments and voids. It can also give many details of timber structures covered by frescoes or painting. The authors propose some critical remarks of the main results obtained by different on-site applications of IR thermography
Damage and defect detection through infrared thermography of fiber composites applications for strengthening of structural elements
No full textFiber Reinforced Polymer (FRP) composites are today widely used for the strengthening and seismic retrofitting of structures. The efficiency of this technology is strongly dependent on the correct positioning and bonding of the fibers on the surface of the structure to be reinforced. The connection between the surface of the substrate (concrete, masonry or steel) and the fibers is assured by the adhesives. The control of the application may be performed with different Non Destructive Evaluation (NDE) techniques but presently there are no standard procedures to assess the quality of the applications in civil engineering structures. Infrared thermography represents a valid tool for the detection and measurement of bonding defects or damage in the composite strips and can be used even for the definition of possible damage progression. The paper presents a series of results obtained using infrared thermography for different types of applications: masonry walls and concrete beams
Indagini endoscopiche e soniche sulla possibile connessione statua-ara e sulla connessione braccio e corpo
No full textFourier analysis applied to Infrared Thermography of Fiber Composites used for the Strengthening of Structural Elements
No full textFiber reinforced polymers (FRP) composites are an efficient method in the strengthening of civil structures. FRP systems are usually applied by means of a wet lay-up method. National guidelines recognize that Infrared Thermography (IRT) is a possible non-destructive evaluation (NDE) technique for the detection of bonding defects, voids and damages and the characterization of the surface layers without a direct contact between the device and the observed area.
Conversely, in the guidelines no clear indications are given about the inspection procedure
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