In this paper, a piezoelectric energy harvesting device consisting of a proof mass and a corrugated cantilever beam is proposed in order to enhance its performance (i.e., an increase in output voltage as well as a reduction in resonant frequency). The sinusoidal or trapezoidal shape of a cantilever beam is able to make the bonding area of piezoelectric materials (e.g., polyvinylidene fluoride (PVDF) film) much larger, resulting in higher output voltages. Moreover, the natural frequency of the device can be significantly decreased due to low flexural rigidity of the beam member. This lownatural frequency device would fit well for civil engineering applications because most civil structures such as bridges and buildings have low natural frequencies. In order to examine the geometrical characteristics of the proposed device, an analytical development and a numerical simulation are carried out. Besides, shaking table tests are conducted with a prototype of energy harvesting device. It is demonstrated from numerical and experimental studies that the proposed energy harvester can shift down its resonant frequency considerably and generate much higher output power as compared with a conventional one having a flat (or straight) cantilever beam.
The feasibility of an active mass damper (AMD) system employing the time delay control (TDC) algorithm, which is one of the robust and adaptive control algorithms, for effectively suppressing the wind-induced vibration of a building structure is investigated. The TDC algorithm has several attractive features such as the simplicity and the excellent robustness to unknown system dynamics and disturbance. Based on the characteristics of the algorithm, it has the potential to be an effective control system for mitigating excessive vibration of civil engineering structures such as buildings, bridges and towers. However, it has not been used for structural response reduction yet. In order to verify the effectiveness of the proposed active control method combining an AMD system with the TDC algorithm, a series of labscale tests are carried out.
In the field of structural health monitoring using wireless sensors, considerable research attention has been recently given
to vibration-based energy harvesting devices for exploring their feasibility as a power source of a wireless sensor node.
Most of the previous studies have focused on lab-scale tests for performance validation. For real application, however,
field tests on developed energy harvesting devices should be conducted, because their performance may be considerably
affected by change in the testing environment. In this study, a new electromagnetic energy harvester is proposed, which
is more suitable for civil engineering application, and the preliminary field test on a real cable-stayed bridge are
conducted to validate its effectiveness.