Platforms for prototyping minimally invasive instruments

The introduction of new technologies in medicine is often an issue because there are many stages to go through, from the idea to the approval by ethical committees and mass production. This work covers the first steps of the development of a medical device, dealing with the tools that can help to reduce the time for producing the laboratory prototype. These tools can involve electronics and software for the creation of a “universal”' hardware platform that can be used for many robotic applications, adapting only few components for the specific scenario. The platform is created by setting up a traditional computer with operating system and acquisition channels aimed at opening the system toward the real environment. On this platform algorithms can be implemented rapidly, allowing to assess the feasibility of an idea. This approach lets the designer concentrate on the application rather than on the selection of the appropriate hardware electronics every time that a new project starts. In the first part an overview of the existing instruments for minimally invasive interventions that can be found as commercial or research products is given. An introduction related to hardware electronics is presented with the requirements and the specific characteristics needed for a robotic application. The second part focuses on specific projects in MIS. The first project concerns the study and the development of a lightweight hand-held robotic instrument for laparoscopy. Motivations are related to the lack of dexterous hand-held laparoscopic instruments. The second project concerns the study and the presentation of a prototype of a robotic endoscope with enhanced resolution. The third project concerns the development of a system able to detect the inspiration and the expiration phases. The aim is to evaluate the weariness of the surgeon, since breathing can be related to fatigue

Experimental investigation on cyclic response of RC elements repaired by CFRP external reinforcing systems

This paper deals with the experimental results of an investigation aimed at studying cyclic response of half scaled RC specimens previously damaged and then repaired with externally bonded carbon fiber reinforced polymer sheets. The research involved the test of ten specimens. Two of them were tested without any external strengthening material in order to provide a reference for the response of repaired specimens. These latter were tested after a previous damaging procedure and a subsequent repair intervention with fiber reinforced polymer composites. The parameters under investigation were the level of initial damage, the strengthening configuration, and the level of axial load. Test results have pointed out effectiveness of the adopted strengthening systems, since repaired specimens exhibited better mechanical responses than the unstrengthened ones

Rinforzo di archi in muratura con cavi scorrevoli

La memoria descrive un modello analitico per la valutazione del comportamento meccanico di archi di muratura rinforzati con cavi disposti all’estradosso. Viene considerato un arco ad asse circolare, di materiale non resistente a trazione, soggetto ad un sistema di carichi e rinforzato con un cavo disposto all’estradosso, scorrevole senza attrito ed ancorato alle imposte. Il modello è formulato nell’ipotesi di spostamenti finiti. L’equilibrio del sistema in una generica configurazione viene imposto rendendo stazionario il potenziale delle forze agenti. Si mostra che se il cavo non è preteso, si ha un aumento di portanza ultima dell’arco solo se la rigidezza assiale del rinforzo è sufficientemente grande. Se invece il cavo è preteso si ha sempre un aumento del carico che provoca il primo spostamento dell’arco (massimo carico che la struttura può sopportare senza spostarsi); se poi la rigidezza del cavo è sufficientemente elevata l’arco collassa per un carico superiore a quello che ne provoca il primo spostamento

A Study of the fracture process at the FRP-masonry interface: the role of the periodic pattern of bricks and mortar joints

This paper sheds light into the effect of the periodic pattern of bricks and mortar joints on the load-carrying capacity of the interface between fiber-reinforced polymer (FRP) composites and masonry. Two simplified cohesive material laws are proposed for the FRP-mortar and FRP-brick interfaces, which allow for the computation in closed form of a finite effective bond length Leff of the interfaces. The aforementioned simplified interfacial laws are employed to compute the load response of the FRP-masonry interface, and to obtain the interfacial shear stress, the FRP axial strain, and the slip profiles along the bonded length. The results indicate that length of the stresstransfer zone (LSTZ) of the FRP-masonry interface varies periodically as its location shifts with respect to the position of the mortar joints. Furthermore LSTZ can be different from the effective length Lbeff of the FRP-brick interface and is influenced by the size of the bricks and mortar joints

Periodic variation of the transferable load at the FRP-masonry interface

This work sheds light into the effect of the periodic pattern of bricks and mortar joints on the stress transfer at the interface between fiber-reinforced polymer (FRP) composites and masonry. Experimental evidence is used to highlight that the fracture process at the FRP-masonry interface depends on the characteristics of the constituent materials and the geometry of the masonry. Two simplified cohesive material laws are proposed for the FRP-brick and FRP-mortar interfaces, which are associated with finite effective bond lengths of the two interfaces. The aforementioned simplified interfacial laws are employed to compute the load response of the FRP-masonry interface, which is compared with the experimental one. The results indicate that length of the stress-transfer zone of, and the transferable load at, the FRP-masonry interface vary periodically in accordance with the periodic pattern of bricks and mortar joints

Connettori in AFRP per l'incremento delll'efficienza di rinforzi in FRP: sperimentazione e modellazione

Il rinforzo di strutture in cemento armato con FRP (Fiber Reinforced Polymer) è una tecnica oggi supportata da numerose esperienze di laboratorio, indagini teoriche e applicazioni. Il rinforzo con FRP prevede l’applicazione di uno strato di fibre lunghe sulla superficie da rinforzare; le fibre sono impregnate con resina epossidica che funge anche da legante con il supporto. La crisi di elementi di calcestruzzo armato rinforzarti a flessione o a taglio con FRP avviene di solito per distacco (delaminazione, debonding) del rinforzo dal substrato, coinvolgendo generalmente alcuni millimetri di calcestruzzo. Nel caso di rinforzo a flessione di travi, si tenta di ostacolare tale meccanismo per mezzo di fasciature di FRP disposte a U, a guisa di staffa, alle estremità dei rinforzi longitudinali. Nella presente nota, è descritta una campagna sperimentale, condotta presso il LabSCo, relativa all’impiego di connettori di fibre aramidiche impregnate con resina epossidica. I risultati di prove di flessione di travetti di calcestruzzo rinforzati con CFRP e connettori di AFRP sono confrontati con quelli di provini analoghi ma privi di connettori. I risultati sperimentali, ed in particolare l’osservazione dei meccanismi di collasso, hanno consentito di delineare le ipotesi per la formulazione di una semplice modellazione analitica per stimare l’effetto del connettore sul carico di delaminazione del rinforzo. Il connettore considerato è risultato capace di incrementare l’efficienza del rinforzo, ostacolandone la delaminazione dal calcestruzzo, fino al raggiungimento della rottura del connettore stesso

Periodic variation of the transferable load at the FRP-masonry interface

This work sheds light into the effect of the periodic pattern of bricks and mortar joints on the stress transfer at the interface between fiber-reinforced polymer (FRP) composites and masonry. Experimental evidence is used to highlight that the fracture process at the FRP-masonry interface depends on the characteristics of the constituent materials and the geometry of the masonry. Two simplified cohesive material laws are proposed for the FRP-brick and FRP-mortar interfaces, which are associated with finite effective bond lengths of the two interfaces. The aforementioned simplified interfacial laws are employed to compute the load response of the FRP-masonry interface, which is compared with the experimental one. The results indicate that length of the stress-transfer zone of, and the transferable load at, the FRP-masonry interface vary periodically in accordance with the periodic pattern of bricks and mortar joints

Strengthening Historical Masonry with FRP or FRCM: Trends in Design Approach

Over the past two decades, composite materials, in forms of Fiber Reinforced Polymers (FRP), have been widely spread worldwide in the field of civil and monumental construction. Design guidelines and provisions were developed and provided by national and international institutions. In the last years, a new generation of materials, named Fabric Reinforced Cementitious Matrix (FRCM) were introduced as strengthening devices for concrete and masonry structures. Their application in the field of historical masonry has grown as a result of the recent Italian earthquakes. In this paper, starting from a retrospective on what has been done in recent years in the field of FRP applications, insights will be discussed for future research and applications of FRP and FRCM in heritage buildings. Some differences between FRP and FRCM materials will be highlighted, in terms of fiber-matrix interface and delamination mechanisms. The different micromechanical behavior in terms of fracture energy will be highlighted, and the macro-mechanical implications in terms of ductility will be pointed out, as a first attempt to quantify this complex problem. By considering the last innovative and pioneering applications of FRP/FRCM in heritage buildings, criteria for structural enhancement will be shown and discussed. This is done with a special focus on the ability, shown by these new technologies, to inhibit failure mechanisms in masonry artifacts