Marcello Vasta | Università degli Studi "G. d'Annunzio" Chieti Pescara (original) (raw)

Papers by Marcello Vasta

ABSTRACT In the present paper, the seismic behavior of a physical 1:5.5 scaled model of the churc... more ABSTRACT In the present paper, the seismic behavior of a physical 1:5.5 scaled model of the church of the Fossanova Abbey is investigated by means of numerical and experimental analyses. Aiming at defining the seismic vulnerability of such a structural typology a wide experimental campaign was carried out. The achieved experimental results lead to the definition of a refined FE model reproducing the dynamic behavior of the whole structural complex. Then, the central transversal three-central bays of the church, as it mostly influences the seismic vulnerability of the Abbey, was investigated in a more detail by means of a shaking table test on a 1:5.5 scaled physical model in the Laboratory of the Institute for Earthquake Engineering and Engineering Seismology in Skopje. In the present paper a brief review of the numerical activity related to the prediction of the shaking table test response of the model is first proposed. Then, the identification of frequency decay during collapse is performed through decomposition of the measured power spectral density matrix. Finally, the localization and evolution of damage in the structure is analyzed. The obtained results shown that a very good agreement is achieved between the experimental data and the predictive/interpretative numerical analyses..

We used speleothem vulnerability for assessing the seismic ground shaking threshold probably expe... more We used speleothem vulnerability for assessing the seismic ground shaking threshold probably experienced or not in caves located within Apennines seismogenic areas. On the southern flank of the Pollino Range, which is considered a current seismic gap, cave observations suggest the lack of significant earthquake-related deformation in the last ~5-7 ka, but the widespread occurrence of creep. In the central Apennines, homogenously-trending collapses within the Grotta Cola (Petrella Liri, AQ) evidence a significant co-seismic deformation event radiometrically bracketed at ~4-5 ka. We supplemented the cave observations with numerical modeling and static test analysis of the speleothem mechanical behaviour to stipulate probability density functions for the bending stress leading to rupture, and established different vulnerability curves for speleothems according to their shapes. Model results are consistent with the co-seismic deformation at Grotta Cola as being caused by the Liri or by ...

International Journal of Dynamics and Control, 2015

ABSTRACT This paper deals with the identification of linear structural systems with random parame... more ABSTRACT This paper deals with the identification of linear structural systems with random parameters. The stiffness matrix of a four-storey shear frame structure is assumed to be linearly dependent on a random parameter ruling the damage evolution of the columns. The evaluation of natural frequencies and the mode-shapes is in the context of random eigenvalue problems in structural dynamics. Using a Taylor expansion of the mass and stiffness matrices, a perturbation technique is first applied to derive the asymptotic solution up to the second order. Then, the evaluation of the statistic of the frequencies and mode-shapes is derived up to the second order. Finally a stochastic identification technique is proposed to characterize the statistics of the random parameter.

III European Conference on Computational Mechanics, 2006

State vector of a dynamic system under a Poisson train of impulses is a non-diffusive Markov proc... more State vector of a dynamic system under a Poisson train of impulses is a non-diffusive Markov process and its joint probability density function satisfies an integro-differential generalized Fokker-Planck- Kolmogorov equation which is also called Kolmogorov-Feller equation. If the train of impulses is driven by non-Poisson, for example renewal, counting processes, the state vector is not a Markov process. Non-Markov pulse

Journal of Computational and Nonlinear Dynamics, 2009

Probabilistic Engineering Mechanics, 2014

The paper tackles the dynamic identification and the damage detection carried out by a spectral-b... more The paper tackles the dynamic identification and the damage detection carried out by a spectral-based method on the well-known Z24 bridge, a three-span prestressed concrete bridge located in Switzerland. Before being destroyed, the bridge was progressively damaged and tested in the framework of the Brite Euram project SIMCES. Starting from this benchmark, the presented spectral-based identification technique is validated and the usefulness of this method as a non-destructive tool able to catch the dynamic behavior of a structure and locate the damage is widely discussed. Firstly, a FE model of the bridge was built and calibrated in order to analyze its response to different excitation types (free vibration, triangular pulse, swept sine, shaker and random vibrations) and several damage scenarios. Secondly, aiming at identifying both the modal parameters and the damage of the bridge, the spectral-based method is applied making use of the power spectral matrix decomposition. Finally, a proper index is defined and applied to this case-study in order to locate the damage.

In this paper an approximate explicit probability density function for the analysis of external o... more In this paper an approximate explicit probability density function for the analysis of external oscillations of a linear and geometric nonlinear simply supported beam driven by random pulses is proposed. The adopted impulsive loading model is the Poisson White Noise , that is a process having Dirac’s delta occurrences with random intensity distributed in time according to Poisson’s law. The

ABSTRACT The evaluation of pressure fields acting on slender structures under wind loads is curre... more ABSTRACT The evaluation of pressure fields acting on slender structures under wind loads is currently performed in experimental aerodynamic tests. For wind-sensitive structures, in fact, the knowledge of global and local wind actions is crucial for design purpose. This paper considers a particular slender structure under wind excitation, representative of most common high-rise buildings, whose experimental wind field on in-scale model was measured in the CRIACIV boundary-layer wind tunnel (University of Florence) for several angles of attack of the wind. It is shown that an efficient reduced model to represent structural response can be obtained by coupling the classical structural modal projection with the so called blowing modes projection, obtained by decomposing the covariance or power spectral density (PSD) wind tensors. In particular, the elaboration of experimental data shows that the first few blowing modes can effectively represent the wind-field when eigenvectors of the PSD tensor are used, while a significantly larger number of blowing modes is required when the covariance wind tensor is used to decompose the wind field.

It is shown that, for a non-linear oscillator responding to non-white random excitation, the ener... more It is shown that, for a non-linear oscillator responding to non-white random excitation, the energy envelope of the response can be modelled approximately as a one-dimensional Markov process. Using a self-consistent asymptotic analysis, for small damping, simple expressions for the drift and diffusion coefficients of this Markov process are derived: these involve Fourier coefficients derived from the solution for free,

Applied Mechanics and Biomedical Technology, 2003

ABSTRACT

Proceedings of the 6th International Conference on Computational Stochastic Mechanics(CSM-6), 2011

International Journal of Non-Linear Mechanics, 2006