<p>This paper presents the results of ambient vibration tests carried out on ten pedestrian bridges located in the city of Querétaro, Mexico. Mathematical models of some bridges were developed and calibrated with the results of the experimental data. Afterwards, pedestrian load models were used to study the analytical response of the bridges and damping devices were simulated based on data available in the literature. The main objective of the study was to decrease the magnitude of structural vibrations and improve human comfort for pedestrians.</p>
This paper deals with the frequency-amplitude response of parametric resonance of alternating current (AC) electrostatically actuated nonuniform micro-electromechanical system (MEMS) cantilever resonators. The resonators consist of a cantilever of linear thickness and constant width, parallel to a ground plate, and under AC voltage producing soft excitations. AC frequency is near first natural frequency of the cantilever. The fringe effect is included in the electrostatic force. Two reduced-order models (ROMs), namely ROMs using one and two modes of vibration, are developed. Two methods are used to solve these ROMs: the method of multiple scales (MMS), and numerical integration. The frequency-amplitude response shows a softening effect and two bifurcation points, one subcritical and another one supercritical. The two bifurcation points occur at zero amplitude. Three branches of steady-state solutions are predicted, one zero amplitude branch, and two non-zero amplitude branches, one stable and one unstable. Pull-in occurs for constant frequency with initial amplitudes above the unstable branches, or when the frequency is swept down from frequencies larger than supercritical bifurcation frequency. The range of frequencies between the bifurcation points decreases as damping increases and/or voltage and fringe effect decrease. Between the two bifurcation points, damping, voltage, and fringe effect have the greatest effect on the subcritical bifurcation point.
The main objective of this work is to carry out a parametric study of stay cables of a bridge under simulated spatially correlated buffeting forces. This vibration mechanism is simulated with an Autoregressive and Moving Average (ARMA) model, and applied to mathematical models of the stay cables of the tallest cablestayed bridge in Mexico. The use of auxiliary damping devices to mitigate vibration is evaluated. The analysis results showed that the use of a more realistic model to represent and characterize the variation in space and time of the fluctuating wind, which is not capture by the white noise or harmonic functions, is advantageous and offers a new alternative to evaluate the structural response of stay cables without and with dampers. The implications of the analyses results in the structural behavior of the stay cables of the bridge are discussed.
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