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Journal ArticleDOI

A New Insight to Vibration Characteristics of Spans under Random Moving Load: Case Study of 38 Bridges in Ho Chi Minh City, Vietnam

TL;DR: The idea behind this method is to use the representative power spectrum density as a powerful tool to evaluate the stiffness decline of spans during their operation period and a new measurement method has been introduced to replace the traditional method of monitoring the health conditions of bridges through a periodic measurement technique.
Abstract: We propose a novel representative power spectrum density as a specific characteristic for showing responses of spans during a long operational period. The idea behind this method is to use the representative power spectrum density as a powerful tool to evaluate the stiffness decline of spans during their operation period. In addition, a new measurement method has been introduced to replace the traditional method of monitoring the health conditions of bridges through a periodic measurement technique. This helps to reduce costs when carrying out testing bridges. Besides, the proposed approach can be widely applied not only in Vietnam but also in many other underprivileged countries around the world. Obtained results show that, during the operational process of spans, there is not only a pure vibration evaluation such as bending vibration and torsion vibration tests but also a combination of various vibration types including bending-torsion vibration or high-level vibrations like first-mode bending and first-mode torsion. Depending on each type of structure and material properties, different types of vibrations will appear more or less during the operational process of spans under a random moving load. Furthermore, the representative power spectrum density is also suitable for evaluating and determining many different fundamental vibrations through the same measurement time as well as various measurement times.

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Citations
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Journal ArticleDOI
TL;DR: This study improves the model of Hooke’s traditional linear mechanical change using a nonlinear model to truly express the nature of structures in reality and adds to the current framework regarding changes in the mechanical properties of a material according to the Kelvin-Voigt model.

4 citations

Journal ArticleDOI
TL;DR: In this paper, the authors investigated changes in the power spectral density caused by beam damage and proposed a parameter to monitor a structure's deteriorating conditions based on the shape of the damaged beam.
Abstract: Using the vibration signals of damaged beams under the act of a moving load, this article investigates changes in the power spectral density caused by beam damage. Based on the results, the authors have proposed a parameter to monitor a structure’s deteriorating conditions. Cracks were created in beams that changed the stiffness of the structure, and simulations of deterioration were conducted. The features proposed in this article are based on the changing shapes of power spectral density from which deterioration in a damaged beam structure can be detected. The experiment was designed to achieve the simulation that best corresponds to a realistic flow of traffic along bridges. Acceleration sensors installed along the beams received the vibration signals that were used to establish the power spectral density. The results of this article show that for a damaged beam, changes in the shapes of power spectral density are much more prominent than changes in the fundamental frequency value. In other words, when compared to using fundamental frequency changes, using shape changes in power spectral density will increase the likelihood of detecting damage for a variety of beam structures.

3 citations

Journal ArticleDOI
TL;DR: In this article, the maximal overlap discrete wavelet transform (MODWT) method combined with the method of fast Fourier transform (FFT) is used to separate the synthetic vibration signal into a structure's discrete vibration and other extraneous vibrations.
Abstract: Power spectral density (PSD) is used for evaluating a structure’s vibration process. Moreover, PSD not only shows a discrete form of vibration but also presents various components in a vibration structure. The superposition of multiple vibration patterns on the same spectrum poses difficulty in analyzing the spectral information in the way needed to find the structure’s discrete vibration. This paper proposes a method for separating the synthetic vibration signal into a structure’s discrete vibration and other extraneous vibrations using the maximal overlap discrete wavelet transform (MODWT) method combined with the method of fast Fourier transform (FFT). With the combination of these two algorithms, MODWT and FFT, the signals of the synthesized vibration have been separated into component signals with different frequency ranges. This means that PSD will be formed, which is based on the combination of the single power spectra of the component signals. Thus, the single spectrum of each of these constructed components can be used to evaluate the types of discrete vibrations coexisting in a structure’s vibration process. The survey results in this paper show the sensitivity and suitability of select types of discrete vibrations to be separated out during the assessment of the structural change, so as to achieve the best possible plan for eliminating the unwanted and unexpected noise and vibration components.

2 citations

Journal ArticleDOI
TL;DR: In this article , the authors proposed a nonlinear model to evaluate structural change in concrete structures by combining a structural model and an unstructured model, based on the Hooke's Law principle.
Abstract: Through the combination of two approaches to evaluating structure change, a structural model and an unstructured model, a constructed model has been proposed in this article that evaluates structural change through the expansion of a linear model following the Hooke’s Law principle. The study has relied on the pure compression model of a structure’s concrete beam with elastic modulus (E) and has added the coefficient of viscosity resistance (C) to suggest a new evaluation method. By defining the aggregation of values of both coefficients C and E through the experimental model, the input parameters are the amplitude values of the vibration spectra and the values of frequencies based on machine learning, through which Z EC values are generated. The Z EC values determine a regression plane accumulated from the aggregation of values for both C and E. The article has introduced the Z EC concept as a useful parameter for the assessment of the quality of concrete structures by the nonlinear model with the appearance of the coefficient C. The results show that the Z EC values have expressed the distribution validity according to the structure’s differing degrees of change. Depending on the texture type and the structure status, these Z EC values will form different shapes. By implementing the actual surveys from many bridges with two types of beam structures, prestressed concrete and conjugated concrete, the Z EC values show the same development trend. On the contrary, in the case of a change in mechanical structure, the Z EC values tend to increase. This evidence proves, in regard to the process of structural change, that the larger the changes in the structure, the more pronounced the distribution of Z EC values, and the wider the distribution range. This shows that the ratio of the damping coefficient C to the elastic modulus E will become increasingly unstable as the structure becomes weaker and weaker. In the future, the results from this study can be applied in the assessment of many types of actual structures.

2 citations

Journal ArticleDOI
TL;DR: In this article, the authors proposed a plan to use the vibration signals acquired from the random circulation status to determine the structure's behavior so as to utilize the signal information during the bridge span's operation.
Abstract: A sufficiently strict conduction of supervision during bridge operation is a crucial matter for many countries, including the underdeveloped country of Viet Nam. In recent times, the budgets in developed countries used for funding the implementation of quality-assessment procedures are quite high compared to the lower budgets in underdeveloped countries. The plan proposed in this work addresses the current lack of information available in the process of structure-quality evaluation. The vibration signals will be acquired from the random circulation status to determine the structure’s behavior so as to utilize the signal information during the bridge span’s operation. The study’s main goal is to find various parameters that can be used to evaluate the actual bridge performance. These parameters must meet certain criteria, such as high sensitivity, low measurement cost, and efficiency in the measurement process, but must not affect the itinerary of vehicles moving on the bridge. The actual structural vibration signals used in this work currently serve as a best trend model for evaluating the operation of the bridge span structure. This study will focus on determining the relationship among deflection, acceleration, and vehicle load so as to evaluate the structure’s working process. This study has also fabricated an experimental model to evaluate and test the sensitivity of the parameters utilized in this study in order to verify the results obtained. The results obtained in this research will be applied for the quality-control process in several bridge models with span structures built with the composite steel concrete cross section of the beam. Many developing countries, including Viet Nam, will receive benefit in the future from the useful advantages presented in this study.

1 citations

References
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Journal ArticleDOI
TL;DR: In this paper, a new method for natural frequency analysis of beam with an arbitrary number of cracks is developed on the bases of the transfer matrix method and rotational spring model of crack.

167 citations

Journal ArticleDOI
TL;DR: In this article, the authors used the acceleration signal instead of the deflection signal, employing a vehicle-bridge finite element interaction model, and developing a novel wavelet-based approach using wavelet energy content at each bridge section, which proves to be more sensitive to damage than a wavelet coefficient line plot at a given scale as employed by others.

161 citations

Journal ArticleDOI
TL;DR: In this paper, the authors examined the sensitivity of wavelet technique in the detection of cracks in beam structures, and the effects of different crack characteristics, boundary conditions, and wavelet functions employed are investigated.

156 citations

Journal ArticleDOI
Qing Zhang1
TL;DR: In this article, a statistical damage identification procedure for bridge health monitoring is presented, where a hierarchical sequence matching scheme is suggested for data normalization to account for the effects of various environmental and operational conditions on the structural dynamics.

117 citations