Abstract. This paper focuses on energy harvesting of traffic-induced vibrations in bridges. Using a pre-stressed concrete highway bridge as a case study, in situ vibration measurements are presented and analyzed. From those results, a prototype of cantilever piezoelectric harvester was designed, tested, and modeled. Even though the considered bridge vibrations are characterized by small amplitude and a low frequency (i.e. below 15 Hz), it is shown that mean power of the order of 0.03 mW can be produced, with a controlled voltage between 1.8 and 3.6 V. A simple model is proposed for the theoretical prediction of the delivered power in terms of traffic intensity. That model shows good agreement with the experimental results and leads to a simple but effective design rule for piezoelectric harvesters to be used on bridges.Piezoelectric energy harvesting from traffic-induced bridge vibrations 2
International audienceThe article aims at detecting and quantifying early structural damages usingdeterministic and probabilistic model updating techniques. To achieve this purpose,local information in a form of optical strain measurement is employed. Thestrategy consists in updating physical parameters associated to damages, suchas Young’s modulus, in order to minimize the gap between the numerical strainobtained from finite element solves and the strain sensor outputs. Generally,the damage estimation is an ill-posed inverse problem, and hence requires regularization.Herein, three model updating techniques are considered involvingdifferent type of regularization: classical Tikhonov regularization, ConstitutiveRelation Error based updating method and Bayesian approach.An illustration of these three approaches is proposed for localizing and quantifyingan early damage in a real 8 meter post-tensioned concrete beam. Numericalresults show that all the methods properly localize the damaged areaand give similar estimation of the damage leve
The paper deals with the results of an experimental campaign carried out on a post tensioned concrete beam with the aim of investigating the possibility to detect early warning signs of deterioration based on static and/or dynamic tests. The beam was tested in several configurations aimed to reproduce 5 different phases of the ‘life’ of the beam: in the original undamaged state, under increasing loss of tension in the post tensioning cables, during and after the formation of cracks at mid span, after a strengthening intervention carried out by means of a second tension cable, during and after the formation of further cracks on the strengthened beam. Responses of the beam were measured by an extensive set of instruments consisting of accelerometers, inclinometers, displacement transducers, strain gauges and optical fibers. In this paper data from accelerometers and displacement transducers have been exploited. The paper presents the test program and the dynamic characterization of the beam in the different damage scenarios in terms of the first modal frequency, identified from dynamic tests and of the bending stiffness monitored during static tests
This paper deals with the theoretical and experimental analysis of magnetically tuned mass dampers, applied to the vibration damping of large structures of civil engineering interest. Two devices are analysed, for which both the frequency tuning ratio and the damping coefficient can be easily and finely calibrated. They are applied for the damping of the vibrations along two natural modes of a mock-up of a bridge under construction. An original analysis, based on the Maxwell receding image method, is developed for estimating the drag force arising inside the damping devices. It also takes into account self-inductance effects, yielding a complex nonlinear dependence of the drag force on the velocity. The analysis highlights the range of velocities for which the drag force can be assumed of viscous type, and shows its dependence on the involved geometrical parameters of the dampers. The model outcomes are then compared to the corresponding experimental calibration curves. A dynamic model of the controlled structure equipped with the two damping devices is presented, and used for the development of original optimization expressions and for determining the corresponding maximum achievable damping. Finally, several experimental results are presented, concerning both the free and harmonically forced vibration damping of the bridge mock-up, and compared to the corresponding theoretical predictions. The experimental results reveal that the maximum theoretical damping performance can be achieved, when both the tuning frequencies and damping coefficients of each device are finely calibrated according to the optimization expressions.
International audienceThis paper addresses the dynamic behavior of piezoelectric cantilevers under base excita-tions. Such devices are frequently used for applications in energy harvesting. An Euler-Bernoulli model that accounts for large-deflection effects and piezoelectric nonlinearities is proposed. Closed-form expressions of the frequency response are derived, both for direct excitation (i.e. with a base acceleration transverse to the axis of the cantilever) and parametric excitation (i.e. with a base acceleration along the axis of the cantilever). Experimental results are reported and used for assessing the validity of the proposed model. Building on the model presented, some critical issues related to energy-harvesting are investigated , such as the influence of nonlinearities on the optimal load resistance, the limits of validity of linear models, and hysteresis effects in the electrical power. The efficiency of direct and parametric excitation is also compared in detail
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