نوع مقاله : پژوهشی اصیل (کامل)
کلیدواژهها
موضوعات
عنوان مقاله English
نویسندگان English
Regarding the importance of bridges as one of the most critical infrastructures, their maintenance, and health monitoring is of high priority. Interaction between the moving vehicles and bridges is amongst the fields of study that have been investigated in depth by numerous researchers in the field of bridge engineering. Among different proposed methods of structural health monitoring of bridges, the indirect methods that do not need the healthy structure response are of high interest because of their ease and low maintenance costs.
The response of a moving mass passing through a bridge can be analyzed for the indirect prediction of the beamchr('39')s mechanical properties. This can lead to the detection of possible damages or degradations in the structure. By mounting high precision accelerometers on the moving vehicle and recording the corresponding signals, it is possible to capture the sudden change of mechanical properties pertaining to the existence of damage in the bridge.
In the current study, an FE code is developed in order to analyze the moving vehicle response. In this code, the bridge is modeled as an Euler-Bernoulli beam, and a complete model comprising stiffness and damping of the suspension system of moving vehicle is built. In order to verify the results of the code, comparisons are made with the outcomes of modal analysis. The sensitivity of the FE results with respect to the number of elements is examined. These comparisons clearly show that both methods reach the same values for a sufficiently high number of elements for the moving vehicle response.
Following verification of the code, a brief review of the concepts underlying the variational mode decomposition (VMD) method is given for a self-contained representation. The VMD can be used to decompose a signal into a number of signals with limited bandwidth. Although it has found many applications in different signal processing cases (e.g. in the field of electronics, mechanical vibrations of machines, or even in the analysis of economic and financial time series), extending its application to the field of structural health monitoring is entirely a recent and ongoing topic of research.
After the introduction of the VMD, damage in the beams is implemented by using fracture mechanics concepts. Different damage scenarios are applied in order to check the reliability and robustness of using VMD as a damage detection method. These include different damage locations (single, dual) and damage severity represented in terms of crack depth. By having a reliable means for the analysis, the novel variational mode decomposition (VMD) is applied to analyze the signals recorded from the vehiclechr('39')s back axel in search of any possible irregularity in the signal properties. By monitoring results attained for several damage cases, the following conclusions can be given:
• The variational mode decomposition (VMD) can highlight the presence of irregularities in mechanical properties that can be reached directly from decomposed signals.
• The location of these signal irregularities coincides with the presumed location(s) of the crack(s).
• The severity of the signal irregularity and corresponding instantaneous energy is proportional to the degree of damage imposed on the beam.
• The moving vehiclechr('39')s natural frequency plays an essential role in the bridgeschr('39') structural health monitoring. The signal processing results exhibit amplified abrupt changes for the vehicles with the natural frequencies close to the beamchr('39')s fundamental frequencies.
Regarding the above conclusions, analyzing moving mass response with the VMD can be a reliable damage detection technique.
کلیدواژهها English
مهندسی عمران مدرس