9,791 research outputs found
Estimates for the stiffness, strength and drift capacity of stone masonry walls based on 123 quasi-static cyclic tests reported in the literature
No full text<p>Database of 123 shear and compression tests on stone masonry walls reported in the literature. Test references, geometrical and typological data, loading and boundary conditions, mechanical characterisation data, and synthetic test results are collected. Such test results include failure mode, force and displacement capacities for different limit states and estimates of the elastic and effective stiffness. Hysteretic force-displacement curves, digitalised from the sources, and the derived envelopes are provided, when available, as .csv files.</p>Please cite as: Vanin F., Zaganelli D., Penna A., Beyer K. (2017). Estimates for the stiffness, strength and drift capacity of stone masonry walls based on 123 quasi-static cyclic tests reported in the literature. Submitted to Bullettin of Earthquake Engineerin
Dynamics of massive point vortices in a binary mixture of Bose-Einstein condensates
No full textWe study the massive point-vortex model introduced in Richaud et al. [A. Richaud, V. Penna, R. Mayol, and M. Guilleumas, Phys. Rev. A 101, 013630 (2020)], which describes two-dimensional point vortices of one species that have small cores of a different species. We derive the relevant Lagrangian itself, based on the time-dependent variational method with a two-component Gross-Pitaevskii (GP) trial function. The resulting Lagrangian resembles that of charged particles in a static electromagnetic field, where the canonical momentum includes an electromagnetic term. The simplest example is a single vortex with a rigid circular boundary, where a massless vortex can only precess uniformly. In contrast, the presence of a sufficiently large filled vortex core renders such precession unstable. A small core mass can also lead to small radial oscillations, which are, in turn, clear evidence of the associated inertial effect. Detailed numerical analysis of coupled two-component GP equations with a single vortex and small second-component core confirms the presence of such radial oscillations, implying that this more realistic GP vortex also acts as if it has a small massive core
gamma-TiAl Fabricated by EBM as Innovative Material for Aerospace Applications with Low Environmental Impact
No full textThe purpose of this thesis is to investigate the material properties of gamma-TiAl (Ti-48Al-2Cr-2Nb) material manufactured by EBM for aerospace applications. Gas atomized Ti-48Al-2Cr-2Nb powders have been used as starting material in order to evaluate additive manufacturing for the production of near-net-shape gamma-TiAl parts to be employed in the field of aero-engines. In particular electron beam melting (EBM) is used to realize a selective densification of metal powder by melting it in a layerwise manner following a CAD model. The microstructure, the residual porosity and the chemical composition of the samples have been investigated both immediately after EBM and after heat treatments. High homogeneity of the samples, very low pickup of impurities (oxygen and nitrogen) with respect to the precursor powders have been observed and due to an extremely low level of internal defects, intrinsic to EBM process, the tensile properties of the EBM gamma-TiAl appear very consistent with a small scatter
Armatura a traliccio nei giunti di malta: una soluzione efficace per incrementare le prestazioni sismiche degli elementi in muratura
No full textSeismic assessment of existing and strengthened stone-masonry buildings: critical issues and possible strategies
No full textThe seismic performance of stone masonry buildings is known to be generally poor with respect to other structural typologies. However, significant differences can be observed for different architectural configurations, structural details and masonry mechanical properties. In particular, the seismic vulnerability of existing stone masonry structures is often governed by local failure modes, typically consisting of out-of-plane overturning of structural portions or crumbling of outer wythes in multi-leaf walls. In buildings with an adequate masonry quality, an overall behaviour controlled by the in-plane capacity of walls can develop and govern the global failure mode, provided that proper connections between perpendicular walls and between walls and floors are effective in contrasting the activation of early local failures. In these cases, the in-plane stiffness of diaphragms (typically vaults and timber floors/roofs) can play a significant role in coupling the response of the different walls, hence controlling the global building capacity. Recent experimental testing campaigns carried out in different laboratories have focused on several aspects of the seismic response of stone masonry buildings and on the effect of several strengthening techniques. The availability of such experimental results allowed validation and improvement of both analysis tools and procedures for the assessment of the seismic capacity of existing stone masonry structures. In order to make them available to all practitioners, the research achievements need to be incorporated in codes and guidelines for the assessment and strengthening of existing stone masonry buildings. The procedures currently proposed in several codes are already based on a rational approach, which starts from the acquisition of an adequate structural knowledge level and allows for using nonlinear analysis procedures. They could straightforwardly include new research findings and practical developments
Tools and strategies for the performance-based seismic assessment of masonry buildings
No full textPerformance-based earthquake engineering became popular in the last decades for both assessment and design of structures. This new trend in research determined the innovation of design codes for all structural typologies with the incorporation of seismic assessment procedures based on pushover analysis and the identifi-cation of damage states in terms of displacement thresholds. Within such a framework, the application of performance-based engineering to masonry struc-tures requires the solution of specific problems and the development of suitable methods and dedicated computational tools. Indeed, in existing masonry buildings the lack of proper connections between orthogonal walls and between walls and floors is rather common and can facilitate the activation of local failure modes, mainly related to the out-of-plane response of walls. Early local damage modes may prevent the development of a global building response governed by the in-plane behaviour of masonry walls and the floor in-plane stiffness. On the other hand, the presence of very flexible diaphragms (i.e. timber floors and roofs) makes the adoption of nonlinear static analysis procedures more complicated and requires to take into account specific issues which can be normally neglected for the global capacity assessment of buildings belonging to other structural typologies. All these issues, together with some lack of experimental information on the capacity limits of different masonry typologies, make dealing with the extension of per-formance-based seismic assessment approach to masonry buildings a more com-plex subject than its application to other structures. Recent research advances and the availability of computational tools based on frame-type macro-element modelling suggest possible strategies for a consistent evaluation of the seismic performance of masonry buildings. The need for further experimental, numerical and theoretical research on this topic is still evident. INGLES
Quantum dynamics of bosons in a two-ring ladder: Dynamical algebra, vortexlike excitations, and currents
No full textWe study the quantum dynamics of the Bose-Hubbard model on a ladder formed by two rings coupled by the tunneling effect. By implementing the Bogoliubov approximation scheme, we prove that, despite the presence of the inter-ring coupling term, the Hamiltonian decouples in many independent sub-Hamiltonians H-k associated with momentum-mode pairs +/- k. Each sub-Hamiltonian H-k is then shown to be part of a specific dynamical algebra. The properties of the latter allow us to perform the diagonalization process, to find the energy spectrum and the conserved quantities of the model, and to derive the time evolution of important physical observables. We then apply this solution scheme to the simplest possible closed ladder, the double trimer. After observing that the excitations of the system are weakly populated vortices, we explore the corresponding dynamics by varying the initial conditions and the model parameters. Finally, we show that the inter-ring tunneling determines a spectral collapse when approaching the border of the dynamical-stability region
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