Nonlinear and Linearized Analysis of Vibrations of Loaded Anisotropic Beam/Plate/Shell Structures

L'abstract è presente nell'allegato / the abstract is in the attachmen

Variable-kinematic finite beam elements for geometrically nonlinear dynamic analyses

This article investigates the dynamic nonlinear response of three-dimensional structures using variable-kinematics finite beam elements obtained with the Carrera Unified Formulation. The formalism enables one to consider the three-dimensional form of displacement–strain relations and constitutive law. The deformation mechanisms and the associated couplings are described consistently with the selected kinematic model. The Hilbert–Hughes–Taylor method and the iterative Newton–Raphson scheme are adopted to solve the motion equations derived in a total Lagrangian scenario. Various models have been obtained by using Taylor- and Lagrange-like expansions. The capabilities of the beam elements are assessed considering isotropic, homogeneous structures with compact and thin-walled sections

Vibration Analysis of Curved Panel Subjected to Internal Pressure and Axial Compression

This paper discusses the change of the natural frequencies and the corresponding mode shapes of an isotropic metallic curved panel subjected to combined internal pressure and axial compression. Tensor calculus is employed to devise the differential operator matrices of the geometrical relation in an orthogonal curvilinear reference system. In the framework of the Carrera unified formulation and by applying the finite element method, the principle of virtual work is used to describe the free vibration of a cylindrical shell subjected to progressive external loading conditions as a virtual procedure of the experimental test vibration correlation technique. Finally, numerical examples are provided, and the effects of the material and geometric characteristics are evaluated. The results show that crossing and veering phenomena between natural frequencies appear when varying the curvature of the panel and the value of the inner pressure, and those effects have to be taken into account for a proper design of this type of structure

Variable Kinematic Shell Finite Elements for Dynamic Analyses of Rotating Structures

This paper makes use of low- and high-fidelity finite plate and shell elements for vibrational analyses of various rotating structures. The two-dimensional models, developed with the Carrera Unified Formulation (CUF), are obtained by adopting two different kinematics expansions, namely the Lagrange-like (LE) and Taylor-like (TE) polynomials. The possibility of selecting different kinematic expansions enables various configurations such as composite, reinforced and sandwich structures to be considered. The equations of motion of rotors with arbitrarily shaped cross-sections are derived with respect to a co-rotating reference system. All contributions induced by the rotational speed (the Coriolis force, the spin-softening and the stress-stiffening terms) for both spinning and blade-like configurations are included in the equations of motion. Furthermore, the linearized and geometrically nonlinear approaches are presented to compute the speed-induced stiffening effect. Numerical simulations are performed on a swept-tip blade and a shallow shell to validate the formulation. Comparisons with solutions available in the literature demonstrated the accuracy of the approach

La asistencia psicológica en situaciones de crisis: los dos momentos en el abordaje de las personas afectadas

El artículo se propone realizar una revisión de dos intervenciones que forman parte de la asistencia psicológica a víctimas en situación de catástrofe: el protocolo en primera atención psicológica (PAP) basado en el modelo de las 4 C y la terapia de reprocesamiento y desensibilización por movimientos oculares (EMDR) para el tratamiento del trastorno por estrés postraumático (TEPT). Se analizan sus características principales, sus bases teóricas y eficacia. Además, se hace hincapié en que ambas intervenciones corresponden a distintos momentos del abordaje de la víctima que experimenta una situación de crisis: la intervención en PAP debe tener lugar en el momento inicial de ocurrencia del incidente mientras que el EMDR debe ser aplicado por un profesional de la salud altamente calificado en caso de que la víctima presente un TEPT en un momento posterior.Fil: Azzara, Sergio. Universidad de la Defensa Nacional. Facultad del Ejercito.; Argentina. Universidad de Buenos Aires. Facultad de Psicología; ArgentinaFil: Grinhauz, Aldana Sol. Universidad de la Defensa Nacional. Facultad del Ejercito.; ArgentinaFil: Squillace, Mario Rodolfo. Universidad de la Defensa Nacional. Facultad del Ejercito.; Argentina. Universidad de Buenos Aires. Facultad de Psicología; ArgentinaFil: Piñeyro, Diego Raúl. Universidad de Buenos Aires. Facultad de Psicología; Argentina. Universidad de la Defensa Nacional. Facultad del Ejercito.; ArgentinaFil: Azzollini, Susana Celeste. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad de la Defensa Nacional. Facultad del Ejercito.; Argentina. Universidad de Buenos Aires. Facultad de Psicología; Argentin

Preliminary results from EMERSITO, a rapid response network for site-effect studies

On May 20, 2012, at 02:03 UTC, a Ml 5.9 reverse-fault earthquake occurred in the Emilia-Romagna region, northern Italy, at a hypocentral depth of 6.3 km (http://iside.rm.ingv.it/), close to the cities of Modena and Ferrara in the plain of the Po River. The epicenter was near the village of Finale Emilia where macroseismic intensity was assessed at 7 EMS98 [Tertulliani et al. 2012, this issue], while the closest accelerometric station, MRN, located less than 20 km west-ward at Mirandola (Figure 1) recorded peaks of ground accelerations of about 300 cm/s2 (www.protezionecivile.gov.it/resources/cms/documents/Report_DPC_1_Emilia_EQSd.pdf). The mainshock triggered liquefaction phenomena a few kilometers eastwards of the epicenter, around the village of San Carlo. On the same day, two other shocks of Ml 5.1 followed (02:07, 13:18 GMT; http://iside.rm.ingv.it/). On May 29, 2012, at 07:00 UTC another Ml 5.8 earthquake hit the region (http://iside.rm.ingv.it/), with the epicenter close to the village of Mirandola (Figure 1). Three other strong aftershocks occurred afterwards, of Ml 5.3 (May 29, at 10:55), Ml 5.2 (May 29, at 11:00) and Ml 5.1 (June 3, at 19:20). For a detailed description of the seismic sequence, see Moretti et al. [2012], Scognamiglio et al. [2012], and Massa et al. [2012], in this issue. The Emilia seismic sequence resulted in 25 casualties, several of whom were among the workers in the many factories that collapsed during working hours, and there was extensive damage to monuments, public buildings, industrial sites, and private homes. […