1,721,171 research outputs found
Effects of cables damage on vertical and torsional eigenproperties of suspension bridges
No full textThis paper presents a continuum model for the nonlinear coupled vertical and torsional vibrations of suspension bridges with arbitrary damage in one main cable and, after pursuing a suitable linearization of the equations of motion, an investigation of damage effects on modal parameters. Damage is modeled as a diffused loss of cross-section representing the typical effect of fretting fatigue and it is introduced in the formulation by enforcing relevant literature results providing analytical solution for the static response of damaged suspended cables. The coupled nonlinear equations of motion of the damaged bridge, including the effects of shear deformation, rotary inertia and warping of the cross-section of the girder, are derived by application of Hamilton׳s principle. In this way, the equations of motion available in the literature for undamaged suspension bridges are generalized to the presence of arbitrary damage in one main cable and the resulting eigenfrequencies and eigenfunctions are derived in an analytical fashion. An extensive parametric investigation is finally presented to discuss damage effects on eigenfunctions and eigenfrequencies under variation of practically meaningful parameters
Nonlinear state observation for cable dynamics
No full textWe explore the applicability of non-linear state observation to cable dynamics. The aim is to capture
from the minimal number of measurements a larger description of the state to be employed in active
or semi-active control policies. To this end, a non-linear state observer is designed analytically, in the space
of modal amplitudes, following relevant literature results. The main theory of non-linear state observation
is preliminary reviewed and the applicability to the dynamics of structural cables is discussed, including asymptotic
stability and minimal number of measurements. Next a sample non-resonant cable is considered
and numerical simulations are carried out in order to test the observation error stability under different conditions.
A non-collocated feedback control strategy, based on transversal actuation, is finally considered, in
which the control algorithm is based on the estimated state variables. The with-observer control solution is
compared with the ideal case in which the entire state of the system is known, thus highlighting the limits
and potentialities of the proposed approach
Confronto di due tecniche per l'identificazione e il monitoraggio dei cavi strutturali mediante prove sperimentali
No full textNonlinear vibration of shallow cables with semiactive tuned mass damper
No full textThe nonlinear vibration of shallow cables,
equipped with a semiactive control device is considered
in this paper. The control device is represented
by a tuned mass damper with a variable out-of-plane
inclination. A suitable control algorithm is designed
in order to regulate the inclination of the device and
to dampen the spatial cable vibrations. Numerical
simulations are conducted under free spatial oscillations
through a nonlinear finite element model, solved
in two different computational environments. A harmonic
analysis, in the region of the primary resonance,
is also performed through a control-oriented nonlinear
Galerkin model, including detuning effects due to the
cable slackening
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