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Rail transit’s wheel–rail system periodically encounters defects such as wheel polygons, rail corrugation, and rail fastener failure, which are intricately linked to the modal parameters of track structures. Identifying these modal parameters is essential for refining wheel–rail dynamics models, understanding track defect mechanisms, and defect detection. This study reviews the current methodologies for identifying track structure modal parameters, emphasizing their significance in track engineering. It categorizes various identification techniques, examines their development, and highlights their application in updating track dynamics theoretical models. The relationship between track modal parameters and wheel–rail defects is discussed, alongside a summary of modal parameter-based defect remediation strategies globally. The paper also evaluates the current state of defect identification research utilizing track modal parameters. In the “prospects” section, three forward-looking research avenues are proposed. These approaches are poised to streamline and improve the efficiency of modal parameter extraction, marking potential breakthroughs in the field.

The paper delineates the procedure to assess probable failure sections through the dynamic conditions of a vertically tapered frame using the experimental modal analysis (EMA), which is validated through the finite element analysis (FEA). The modal parameters are experimentally determined by the frequency response functions (FRFs) using the accelerometer, force transducer, electro-dynamic shaker, dynamic signal analyzer (DSA) and post processed by the ME’Scope software. The ANSYS Workbench 14 was used for finding the modal parameters through the FEA. The FEA model was also tested by convergence study. The boundary conditions of the vertically tapered frame in the FEA is kept similar to the EMA. The values obtained by the two methods have been compared for their proximity.

This paper proposes a novel optimization algorithm called modal force information-based optimization (MFIBO) to identify the location and severity of damage in structures. The main idea behind the MFIBO is to take advantage of information captured from the modal force of structural elements to seek the optimum damage variables. The modal element force, defined as the internal element force caused by the action of mode shapes, allows the MFIBO to recognize promising directions in the search space and assists in accelerating the optimization process. Indeed, unlike meta-heuristic optimization algorithms, which disregard explicit information about the problem and rely only upon time-consuming stochastic search computations, the MFIBO employs an informed search strategy to perform optimization in a rational and directed manner. In order to assess the effectiveness and applicability of the proposed MFIBO algorithm, four benchmark damage identification examples of truss and frame structures are conducted under both noise-free and noisy conditions. In each example, the results of the MFIBO are also compared with those attained by two well-known meta-heuristic algorithms, namely the differential evolution and the teaching–learning-based optimization. The obtained results reveal that the MFIBO is able to accurately and reliably identify structural damage with a significantly lower computational burden compared to the meta-heuristic algorithms.

In this paper, a modified eigensystem realization algorithm for modal parameter identification and relaxation parameter is extended from a viscous damping system to a nonviscous damping system. The equation of motion with nonviscous damping in second-order form is expressed in the state space formulation. The eigenvalues of the second-order form equation are proved equal to the state space formulation. The extended method is based on the proposed nonlinear relationship between the eigenvalues and the damping parameters of a nonviscous damping system. The identified procedure of the proposed method is given in detail. Finally, the method is validated using three numerical examples for assessing its accuracy.

This study investigates the seismic behavior of long-span prestressed concrete box-girder bridges subjected to long-duration (LD) ground motions and spectrally equivalent near-fault (NF) and far-fault (FF) short-duration ground motions. For this purpose, the Kömürhan and Gülburnu Highway Bridges built with the balanced cantilever method using prestressed concrete box-girder were selected. This paper consists of two main sections. First, ambient vibration tests were conducted to identify the modal parameters of the bridges and calibrate the finite element models. Second, using three ground motion sets consisting of 42 acceleration records applied to the orthogonal and vertical directions of the bridges, the structural responses were evaluated and compared. In order to determine the type of ground motion that is critical for this type of bridge, these sets consist of 14 long-duration ground motions, 14 spectrally equivalent near-fault short-duration ground records, and 14 spectrally equivalent far-fault short-duration records. The comparison parameters considered for this study were displacements and internal forces in the piers and decks. The results strive to highlight the extent to which the duration and characteristics of the ground motion sets affect the structural behavior. Results indicate that the mean deck displacements of selected bridges obtained from FF short-duration records were nearly 10.70% and 7.44% less than those obtained from the LD and NF short-duration ground motions. These trends were also observed in the bridge piers. Moreover, increases of up to 17.54% and 26.65% in the mean shear forces of the piers under LD and NF short-duration ground motions were observed compared to those determined from the FF short-duration counterparts. Similar trends were observed in the bending moment values. It was also observed that far-fault short-duration records may have substantial consequences on such structures.