Affiliations: Research Center for Mechanics of the Machines, and
Technological Equipments, Faculty of Engineering, "Dunarea de Jos" University
of Galati, Braila, Romania
Abstract: A highly efficient seismic protection of bridges have been
demonstrated by the passive control systems with mechanical links with
selective viscoelastic energy dissipation through viscous friction and dry
friction. These systems are able to take over the deformations and movements
caused by temperature variations, those due to seismic activities and from road
traffic. A number of natural factors such as atmospheric and anthropogenic
parameters, such as shock and vibration from road traffic, lead to the
degradation of the viscoelastic bonds of passive control systems based on
rubber molding. The presence of the elastic and dissipative nonlinear forces in
the functioning of antiseismic systems inevitably leads to quantitative and
qualitative changes of the structural responses of bridges and viaducts both in
time and spectral domains. The implications of these changes on the integrity
and stability of the bridge or viaduct sections may be from the simplest to the
most severe depending on the type of seismic excitation to which they are
subjected. For these reasons, it is imperative that we should identify and
quantify the degree of nonlinearity of antiseismic systems embedded in the
structure of bridges and viaducts in order to prevent accidents with severe
socioeconomic implications. In this way can determine the dependence of the
nonlinear behavior of the bearing system and the degree of degradation of their
viscoelastic links. From a theoretical point of view the following parameters
of the vibration of the system will be comparatively analyzed: the displacement
and acceleration of the bridge deck in time and frequency domains, the
hysteretic loop, the representation in the plane of phases, the power spectral
density and the spectrograms of the acceleration signals. From an experimental
point of view there will be identified and plotted the parameters able to
provide information regarding the abnormal operation of the bearings from the
elastomer: system acceleration, representations in time and frequency and its
spectrogram.
