Papers by Keyword: Structural Vibration

Abstract: Conducting surveys of multi-storey buildings is a laborious task, because large volumes of visual and instrumental research should be carried out. Reduction of labor costs with an increase in the reliability of information about the state of damage and technical condition is an actual scientific and practical task. One of the ways to solve it is to use non-destructive vibration diagnostic methods. The purpose of carrying out diagnostics with the use of vibration based damage detection methods is to search for damages in structural elements that can cause the deviation of the dynamic parameters of a structure from calculated ones. Determination of the dynamic parameters of the structure, in particular natural frequencies and mode shapes of mechanical systems, is one of the most important tasks that allows obtaining integral information about the state of a structure. This article presents the results of calculations for the localization of slabs defects in a multi-storey building with a transverse crack, span L = 4.5 (m), height H = 0.2 (m), with prestressed reinforcement d = 0.05 (m). Vibration based Damage Index method was used to localize the defect. During the study, reliable localization values of the defect area of the slab were obtained, this indicates that the vibration method for determining the damage index with a sufficient degree of accuracy allowed predicting the site of damage to the structure.

Abstract: Damping is one of the several important parameters in the dynamic system. It reduces amplitude response of a structure, especially around the resonance. The higher the damping, the better the performance (more comfort, lower stress, less fatigue), and the longer the life cycle of the structure will be. There are many types of damper amongst other is the tuned mass damper (TMD), where mass and spring are designed in such that the TMD frequency is close to the natural frequency of the structure in question where the phase angle is about 180 degree out of phase. Applying steel-rubber composite beam as a damper in the TMD system is expected to increase the damping of the structure of interest. The objective of this study is to test experimentally and numerically the dynamic parameters of the rubber-steel composite beam upon a cantilever support system under static load-displacement test and flexural dynamic excitation. The addition of steel (in the form of wire mesh) embedded in the rubber beam significantly increases the stiffness, but the damping ratio, at a small range of displacement. The effectiveness of rubber material in the steel-rubber composite beam is expected when large displacement occurs, meaning that more energy dissipation and larger damping ratio. The established numerical model is able to generate dynamic parameters close to results of the experimental model, but the damping ratios.

Abstract: In this paper, we depart from the basic vibration equation deduced from Vibro sand tower structure recurrence formula. Using ANSYS finite element software to simulate the red sand of the top ten tower structural vibration modal. Of which the first two modal solutions in accordance with the conventional prismatic cantilever closer to theoretical calculations, the results of the finite element solution proved authentic, we provide a theoretical basis for the use of finite element methods for solving the structural problems of sand washing tower.

Abstract: Structure vibration is one of the main causes of noise. Thin-walled workpiece has a smaller stiffness,it will easily produce vibrations at work ,and become a source of noice. It is very necessary to study acoustic radiation characteristics of plat,so can we effectively control the structure and connection type of panel structure to change acoustical radiation characteristics.This paper advance a element method to test acoustical radiation characteristics of plat,and take experiment with magnesium alloy sheets.

Abstract: In order to improve working frequency band and damping effect of a dynamic vibration absorber, a new kind of dynamic vibration absorber is presented. Its resonant frequency could be real-time adjusted by adapting the stiffness of the spring. The vibration attenuation characteristics are analyzed theoretically and numerically. According to simulation analysis, effects of geometrical parameters are researched and optimum geometric parameters are determined. The damping effect was simulated in a flat structure, the results show that the working frequency band and damping effect of the DVA are both remarkable.

Abstract: This paper studies how the external shock loads induces vibration, and proposes a method to analyze the effect of external shock loads on building structure vibration. On basis of elastic mechanics and dynamics theory, the method calculates pressure load on each bearing node of the building produced by finite element model in accordance with the nodal displacement equivalent principle, and takes the load as excitation to study vibration of the building structure. The accuracy of the analytical method is verified by comparing with classical theory and the analysis' results of other scholars. Experiments show that the vibration analysis model can efficiently perform analysis of vibration induced by uncoupled external shock for building with complex spatial structure.

Abstract: According to the vibration in a residential building, a field investigation was conducted. Using the elimination strategy, the primary vibration source was determined, the vibration serviceability of the residential building was assessed by the environmental vibration tests, and the measures for vibration reduction were proposed. The results show that the vibration in the residential building is caused by 5 textile mills nearby, among which, Mill II has significant effect on the residential building. By applying the measures for vibration reduction to Mill II and reinforcing the residential building, the vibration serviceability can be improved.

Abstract: The dynamic characterization of vehicle structures is a crucial step in NVH analysis and helps in refining the vibration and noise in new vehicles. This paper investigates the dynamic properties of two parts of the vehicle structure which are door and hood panels. Theoretical modal analysis which is referred to as Finite Element Analysis (FEA) and Experimental Modal Analysis (EMA) or modal testing has been used as investigative tools. The paper investigates the structural dynamic properties of door and hood panels of a local car. ME'scope software was used to analyze the data obtained from Pulse to extract the dynamic properties of the panels. LS-DYNA software was used to analyze the dynamic behavior of the structure. The comparison between the results obtained from both analyses showed some similarity in frequencies and mode shapes. Finally the paper concludes that experimental modal analysis and finite element analysis can both be used to extract dynamic properties of structures.

Abstract: This paper presents a novel approach for the determination of the loss of composite action for timber composite systems using only measurements from non-destructive vibration testing. Traditionally, the composite action of a system is evaluated from static load testing using deflection measurements. However, static load testing is expensive, time consuming and inappropriate for existing flooring systems. The method proposed in this paper is based on the Damage Index (DI) method, which uses changes in modal strain energies, to detect locations and severities of damage. In the proposed method, a new Loss of Composite Action Index (LCAI), which is derived from direct mode shape measurements obtained from dynamic testing, is introduced to evaluate the loss of composite action. The proposed method is tested and validated on numerical and experimental models of a timber composite beam structure, which consists of two timber components that are connected with different numbers of screws to simulate various degrees of partial composite states. The results obtained from the new method are very encouraging and show a clear trend of the proposed dynamic-based LCAI in indicating the loss of composite action in the investigated timber composite structure.

Abstract: This paper presents a new method for sensing the radiation mode amplitudes by using piezoelectric fibers for vibrating beams with different boundary conditions. Two straight and one curved fibers bonded on the surface of the beam are taken as a sensor. The sensor output is defined as the output current of the curved fiber subtracting the output currents of the other two straight fibers. By means of designing the appropriate shape of the curved piezoelectric fiber, the sensor output can directly lead to the corresponding radiation mode amplitude of the beam. The equations which define the curved sensor shapes are independent of the type and position of the external excitation. Finally, a numerical example is given and the effects of shape error and location error of such type sensor are discussed.