86,873 research outputs found
Dynamical Tests on a Damaged Bridge
No full textThe results of a series of dynamical tests on a damaged reinforced concrete bridge are presented in this paper. Several damaged configurations were studied and the corresponding variation of modal parameters was observed. Both harmonically forced and ambient dynamical tests have been conducted comparing the ability of different techniques to capture the structural modifications induced by damage on the lower natural frequencies and modal shapes of the bridge
Dynamic Testing and Structural Identification of a Curved Multi-Span Viaduct
No full textAn interpretation of dynamic testing carried out on a curved multi-span post-tensioned reinforced concrete viaduct is presented in this paper. The viaduct has been recently built in the new highway line connecting the cities of Pordenone and Conegliano (North-Eastern Italy). Output-only vibration tests under traffic loads were carried out to extract the dynamic pa-rameters of the lower vibration modes of the structure. A comparison between experimental data and numerical results obtained from a preliminary finite element model of the viaduct is pre-sented and discussed
Nonlinear feedback control for the stabilization of cable oscillations: analytical and experimental models
No full textNumerical simulations of chaotic dynamics in a model of elastic cable
No full textThe finite motions of a suspended elastic cable subjected to a planar harmonic excitation can be studied accurately enough through a single ordinary-differential equation with quadratic and cubic nonlinearities. The possible onset of chaotic motion for the cable in the region between the one-half subharmonic resonance condition and the primary one is analysed via numerical simulations. Chaotic charts in the parameter space of the excitation are obtained and the transition from periodic to chaotic regimes is analysed in detail by using phase-plane portraits, Poincaré maps, frequency-power spectra, Lyapunov exponents and fractal dimensions as chaotic measures. Period-doubling, sudden changes and intermittency bifurcations are observed
Un programma di manutenzione programmata per i ponti gestiti da enti pubblici territoriali: model updating e futuri sviluppi
No full textPost-critical finite, planar dynamics of a circular arch: Experimental and theoretical characterization of transitions to nonregular motions
No full textThe role of the experimental analysis in the formulation and validation of a reduced order analytical model of a planar arch under a vertical, sinusoidally varying, concentrated force on the tip, is analyzed in this work. One of the main dynamical phenomena exhibited by such systems is the loss of stability of the directly excited simple, 1-mode, symmetric, periodic solution and the evolution towards different regular and nonregular coupled motions where anti-symmetric components of the motion arise. The experimental analysis allows one to characterize the different classes of motion, bifurcation paths and main characteristics of the spatial flow and gives useful hints to be used in the analytical approximation. A minimal analytical model able to reproduce the actual dynamics of an experimental prototype is eventually proposed
PLANAR NON-LINEAR OSCILLATIONS OF ELASTIC CABLES UNDER SUBHARMONIC RESONANCE CONDITIONS
No full textPlanar non-linear oscillations of elastic cables under 1/2 and 1/3 subharmonic resonance conditions are studied. In both cases a perturbation analysis is accomplished, with various orderings considered for the damping and excitation parameters. The regions of existence of steady state non-trivial subharmonics, and the frequency-response curves, are determined, as well as stability and domains of attraction of the solutions. A parametric investigation of the dynamic phenomena for technical cables is performed. Results of numerical integration are also presented, and used to discuss the accuracy of the asymptotic solutions and to evaluate the importance of the free secondary component in the system response
PLANAR NON-LINEAR OSCILLATIONS OF ELASTIC CABLES UNDER SUPERHARMONIC RESONANCE CONDITIONS
No full textPlanar non-linear oscillations of elastic cables under order two and three superharmonic resonance conditions are studied. As referred to one ordinary equation of motion, second order perturbation analyses are developed and the solutions are used to enlight the features of the two dynamic phenomena for technical cables with various sag-to-span ratios. Some aspects of interaction between the two main superharmonic components occurring in the motion are discussed, and the results of numerical integrations of the original equation are presente
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