1,354,229 research outputs found
Minimal mass and self-stress analysis for innovative V-Expander tensegrity cells
No full textTensegrity structures are an intriguing kind of structures by virtue of their deployability, scalability and high stiffness to mass ratio. Fraddosio et al. recently proposed a family of five innovative V-Expander elementary tensegrity cells, characterized by an increasing degree of geometrical complexity, and designed as a morphological evolution of a concept originally proposed by Motro and Raducanu. Here, we study the mechanical behavior of these innovative V-Expander elementary tensegrity cells by referring to different topologies; in particular, we analyze for such cells the feasible self-stress states in the cases in which the components in compression are composed of 2, 3, 4 and 6 struts, respectively. In addition, we evaluate the minimal mass of the cells taking into account the buckling strength of members in the self-equilibrium states according to the indications of standard building codes
Documentare, comprendere e conservare le eredità di Luigi Santarella / Documenting, Understanding and Preserving the Legacy of Luigi Santarella
No full textThis panel has brought together a group of scholars in the disciplines of engineering and architecture to discuss the figure of Luigi Santarella, offering interdisciplinary insights and concrete examples of how we might look at his work to better understand his legacy not only as a construction scientist and theorist or as a pioneer of reinforced concrete structures, but also as an educator committed to training a new generation of designers in such a founding period as the early Twentieth century. In line with the general topic of the Study Day and with the contributions from the invited speakers, this panel was designed to outline possible broader approaches for a further deepening of a well-known figure — but still not fully investigated in its complexity — as that of Santarella. Bringing together the points of view of Enzo Siviero (engineer and professor of Structural engineering at IUAV University), Giuseppina Uva (engineer and professor of Structural engineering at the Polytechnic University of Bari), Rita Vecchiattini (architect and professor of Architectural restoration at the University of Genoa), Aguinaldo Fraddosio (engineer and professor of Structural mechanics at the Polytechnic University of Bari) and Lorenzo Pietropaolo (architect and research professor in Architectural history at the Polytechnic University of Bari), panelists’ contribution suggests to further document and investigate Santarella’s work with a holistic approach so to address substantive issues — also in terms of training of the younger generations — such as the interaction between Architecture and Engineering in design processes or the urgent challenges to preserve reinforced concrete architectures of the Twentieth century. This means promoting specific communication and dissemination actions, and conceiving new research outlines on Santarella’s theoretical and built legacy that may intertwine historical and archival studies, methods and techniques for structural analysis, for conservation, restoration or adaptive reuse of reinforced concrete heritage
A new numerical approach for determining optimal thrust curves of masonry arches
No full textIn this paper a new numerical approach for determining admissible thrust curves for masonry arches is proposed. Arbitrary loading conditions, including distributed loads applied to the extrados and to the intrados of the arch, but also horizontal inertial forces simulating the effects of seismic actions are considered for arches of any geometry. The admissible solutions, corresponding to equilibrium thrust curves entirely contained in the thickness of the arch, are consistent with the lower bound theorem of Limit Analysis and, thus, are “safe” solutions from a structural point of view. The well-established Milankovitch's theory for the equilibrium of masonry arches is reviewed and generalized. Then, a specific formulation of the theory is presented, allowing the construction of an effective and efficient numerical procedure based on the Point Collocation Method and enriched by a constrained optimization routine. The latter is aimed at determining, among all the admissible equilibrium solutions, the optimal solution matching specific requirements of interest for applications, as the solution corresponding to the maximum or minimum thrust. The proposed procedure is discussed and validated with reference to the cases of circular, parabolic and pointed arches. In particular, maximum and minimum thrust solutions have been determined for all the examined cases
A New Ultrasonic Immersion Technique for the Evaluation of Damage Induced Anisotropy in Composite Materials
No full textWe present a theoretical and experimental approach for the characterization of the damage induced anisotropy superimposed to the constitutive anisotropy of fiber-reinforced composite materials.
The proposed theoretical model has been developed in the framework of the Continuum Damage Mechanics theory and allows for determining a tensorial damage measure based on the change of the elastic moduli of the composite material. Moreover, the model is general since it is applicable independently of the fibers reinforcement nature, of the presence of cracks, interlaminar voids and delamination, of the geometry of this cracks, and from of failure mechanisms of the composite materials.
We perform damage experiments by employing an innovative goniometric device designed and built at our laboratory (Laboratorio “M. Salvati”), and aimed at the mechanical characterization of materials. In particular, by rotating the sample into a water tank, we measure the ultrasonic “natural” velocities of the undamaged composite material along suitable propagation directions. This allow us for classifying the degree of symmetry of the material and for determining the elastic constants, also in highly anisotropic materials. Then we measure the ultrasonic velocities of the artificially damaged composite and we determine again the elastic moduli. The comparison between the elastic moduli of the damaged and the undamaged composite allows us for the characterization of the anisotropic tensorial damage measure
Un nuovo approccio teorico e sperimentale alla caratterizzazione dell’anisotropia indotta da danno nei materiali compositi fibro-rinforzati
No full textLo studio teorico e sperimentale dell’anisotropia indotta da danno nei materiali compositi fibrorinforzati risulta molto complesso in quanto l’anisotropia indotta si sovrappone all’anisotropia costitutiva del materiale. Sulla base di recenti lavori sperimentali da noi condotti sulla caratterizzazione meccanica dei materiali anisotropi mediante tecniche ultrasoniche ad immersione [1- 2], abbiamo sviluppato un nuovo approccio teorico e sperimentale alla caratterizzazione dell’anisotropia indotta da danno nei materiali [3-4]. In questo studio, mostriamo i risultati sperimentali ottenuti da prove ultrasoniche effettuate su campioni di compositi fibro-rinforzati (GFRP) prima e dopo test di danneggiamento artificiale. L’analisi delle curve di ritardo e l’impiego di un modello di danno anisotropo hanno permesso di riconoscere la variazione della risposta acustica dei materiali compositi e di stimare l’anisotropia indotta da danno.The theoretical and experimental analysis of the damage induced anisotropy in fiber-reinforced composite materials is very difficult because the damage induced anisotropy is superimposed to the constitutive anisotropy of the material. Based on some recent experimental works by us on the mechanical characterization of anisotropic materials by ultrasonic immersion techniques [1-2], we developed a new theoretical and experimental approach for characterizing the damage induced anisotropy of materials [3-4]. In this study, we show the experimental results obtained by ultrasonic tests carried out on samples of a glass fiber-reinforced polymer composite (GFRP) before and after artificial damage tests. The analysis of the slowness curves and the use of an anisotropic damage model allowed us for recognizing the variation of the acoustic response of the composite and for estimating the anisotropy induced damage
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