Wave Mode Control of Cantilever Slab Structure of T-Beam Bridge with Large Aspect Ratio

The cantilever plate structure in a T-beam bridge with a large aspect ratio will cause vibration under the influence of environmental disturbance and self-stress, resulting in fatigue damage of the plate structure. Wave control based on elastic wave theory is an effective method to suppress the vibration of the cantilever plate structure in a beam bridge. Based on the classical thin plate theory and the wave control method, the active vibration control of the T-shaped cantilever plate with a large aspect ratio in the beam bridge is studied in this paper. The wave mode control strategy of structural vibration is analyzed and studied, the controller is designed, the vibration mode function of the cantilever plate is established, and the control force/sensor feedback wave control is implemented for the structure. The dynamic response of the cantilever plate before and after applying wave control force is analyzed through numerical examples. The results show that the response of the structure is intense before control, but after wave control, the structure increases damping, absorbs the energy carried by the elastic wave in the structure, weakens the sharp response, and changes the natural frequency of the structure to a certain extent.

Little-known facts of the creative way of the outstanding Ukrainian restorer OI Minzhulin: to the problem of restoration of objects of underwater archeology

The article highlights little-known facts from the biography and scientific restoration activities of O. Minzhulin, related to the restoration of underwater archeology. The paper describes the first methodology of restoration and conservation of materials of underwater archeological researches of Ukraine initiated by Minzhulin. This methodology involves: This methodology gradually included: placing the lifted objects in an alkaline aqueous solution, applying the method of intensive washing in deionized water, the method of desalination with sesquicarbonate, the method of alkaline-sulfite treatment of iron, the involvement of an ultrasonic device with frequency wave control and more. Innovative were the methods of restoration of underwater archaeological ferrous metal. An underwater volcano is named after the outstanding restorer.

Traveling-wave control of the bending wave in a beam for high quality sound radiation

The bending wave generated by the actuator exciting a panel can be controlled to be in the traveling wave form void the structural resonances, which deteriorates the radiated sound if the panel is used as a speaker. Although such traveling-wave control method (TCM) yields a wider effective frequency range than the modal control method, the requirement of using many actuators is the practical problem yet. If a beam is employed instead of a plate as a panel speaker, the number of actuators can be reduced despite a smaller radiating surface than a plate. This study adopts three actuators for the beam control using TCM. An actuator excites the beam in the middle position, and the two actuators near the two edges are used to suppress the reflected waves from the boundaries. The control result shows that the driving-point mobility of the primary actuator is converted into that of an infinite beam, which means that the boundaries are changed into anechoic ones and the structural resonances are eliminated. Accordingly, the beam radiates a smooth sound spectrum without sharp peaks and troughs related to the resonant responses. Effects of material and dimension in determining the effective frequency range are also explored.

Numerical Analysis of Stem Wave Control Effect of a Curved Slit Caisson Breakwater

Curved slit caisson has been the preferred structural type of breakwater in South Korea, and effective control of stem waves is a crucial design factor significantly affecting the performance of a curved slit caisson breakwater. Most of the past studies on stem waves heavily relied on wave drivers like the cubic Schrödinger Eq. due to the intrinsic difficulties in analyzing stem waves. However, considering the perturbation method evoked in the derivation of cubic Schrödinger Eq., the wave driver mentioned above could give erroneous results in the rough sea due to the higher-order waves that appeared in the wave field by resonance wave-wave interaction. In this rationale, in this study, the numerical simulation was implemented to verify the stem wave control effect of curved slit caisson using the ihFoam, toolbox having its roots on OpenFoam. It was shown that curved slit caisson breakwater effectively alleviates the scope and height of stem waves.