An optimized tuned mass damper/harvester device

Much work has been conducted on vibration absorbers, such as tuned mass dampers (TMD), where significant energy is extracted from a structure. Traditionally, this energy is dissipated through the devices as heat. In this paper, the concept of recovering some of this energy electrically and reuse it for structural control or health monitoring is investigated. The energy-dissipating damper of a TMD is replaced with an electromagnetic device in order to transform mechanical vibration into electrical energy. That gives the possibility of controlled damping force whilst generating useful electrical energy. Both analytical and experimental results from an adaptive and a semi-active tuned mass damper/harvester are presented. The obtained results suggest that sufficient energy might be harvested for the device to tune itself to optimise vibration suppression

Robust identification of backbone curves using control-based continuation

AbstractControl-based continuation is a recently developed approach for testing nonlinear dynamic systems in a controlled manner and exploring their dynamic features as system parameters are varied. In this paper, control-based continuation is adapted to follow the locus where system response and excitation are in quadrature, extracting the backbone curve of the underlying conservative system. The method is applied to a single-degree-of-freedom oscillator under base excitation, and the results are compared with the standard resonant-decay method

Layered composite entangled wire materials blocks as pre-tensioned vertebral rocking columns

This work focuses on entangled wire materials as an option for use between segments of a novel self-centring bridge pier inspired from the human spine mechanism to increase energy dissipation capability of the pier in rocking. A comprehensive set of free-decay vibration tests was conducted on small-scale columns with and without entangled wire materials. Wooden blocks are used as vertebrae with entangled wire materials as intervertebral disks. The whole system is tied together using a pre-tensioned tendon. Dynamic properties of columns (i.e. frequency and damping ratio) were then identified and compared. It is found that the use of entangled wire materials significantly increases the energy dissipation capacity of the system during rocking. This finding is very encouraging for future use of entangled wire materials composite systems in large-scale testing of the proposed rocking column, while their shear and axial stiffness needs be improved to reduce large shear and axial deformations

Experimental investigation of a novel class of self-centring spinal rocking column

This paper explores a proof of concept self-centring spinal column concept experimentally. The idea of the system is inspired by the mechanical interaction of the vertebral bones and intervertebral discs in human spine. Experimental tests are undertaken to explore whether a similar bridge pier system could be constructed to withstand seismic dynamic loading in an equally efficient manner. The experimentation is performed on tied (pre-tensioned) wooden blocks (vertebrae) with and without rubber strips between the vertebrae acting as the intervertebral discs. Small-scale test specimens are excited sinusoidally using a small-scale shake table, and the response of the system recorded through triaxial accelerometers attached to the structure. The nonlinear dynamic response and mechanics of the system are then investigated under sinusoidal dynamic excitation. It is found that the integration of intervertebral rubber discs into wooden vertebrae reduces the nonlinearity of the system, and increases the flexibility and damping. The experimental results show that the proposed system can sustain large lateral displacement without any residual deformation after the excitation

Simulation of the Load Evolution of an Anchoring System under a Blasting Impulse Load Using FLAC 3D

A limitation in research on bolt anchoring is the unknown relationship between dynamic perturbation and mechanical characteristics. This paper divides dynamic impulse loads into engineering loads and blasting loads and then employs numerical calculation software FLAC 3D to analyze the stability of an anchoring system perturbed by an impulse load. The evolution of the dynamic response of the axial force/shear stress in the anchoring system is thus obtained. It is revealed that the corners and middle of the anchoring system are strongly affected by the dynamic load, and the dynamic response of shear stress is distinctly stronger than that of the axial force in the anchoring system. Additionally, the perturbation of the impulse load reduces stress in the anchored rock mass and induces repeated tension and loosening of the rods in the anchoring system, thus reducing the stability of the anchoring system. The oscillation amplitude of the axial force in the anchored segment is mitigated far more than that in the free segment, demonstrating that extended/full-length anchoring is extremely stable and surpasses simple anchors with free ends