International Journal of Structural Stability and Dynamics

The safety of railway vehicles running on bridges needs to be evaluated in the seismic design of bridges. This study examined the spectral intensity calculated from the lateral vibration of the bridge deck during earthquakes, a Japanese code-based index to measure bridge vibration’s strength. In addition, the effect of the torsion of the bridge deck on vehicle derailment is investigated using a nonlinear vehicle–track–bridge model. The bridge deck torsion increases the derailment risk, especially for bridges with a low natural frequency. The reason lies in that the lateral and torsional deck motions are highly correlated for bridges with lower frequency. Based on this observation, a code-type formula was proposed to evaluate the vehicle running safety including both lateral and torsional motions of the bridge deck. The accuracy of the proposed formula was demonstrated by comparison with vehicle–track–bridge simulation excited by ground motion records. The new procedure overcomes the non-conservative assessment of derailment caused by ignoring bridge torsion.

To reduce the aerodynamic load of super high-speed elevators, in this paper, the coefficient of drag $C_d$ and the coefficient of yawing moment $C_{ym}$ of the elevator are selected as optimization objectives for the optimization of the air rectification cover (ARC) shape. The elliptic curve method was used to build the parametric model of the ARCs, six design variables were selected, and the design space of the ARC was determined. With the optimal Latin hypercube design method, the training points were selected, and the computational fluid dynamics numerical simulation was conducted to calculate the corresponding responses. Then, the relationship between the design variables and the responses was analyzed. The radial basis function (RBF) surrogate model of the relationship between the design variables and responses was constructed. Finally, the non-dominated sorting genetic algorithm-II (NSGA-II) was employed to optimize the shape of the ARC. The results show that the $C_d$ and $C_{ym}$ decrease by 16.51% and 60.92%, respectively, compared with the unoptimized ARC, indicating that the ARC designed in this paper is optimized and can effectively reduce the aerodynamic load. Furthermore, among all the design variables, the bluntness of the ARC in the $X$-direction has the most significant effect on the aerodynamic load, and the height of the ARC ($h_1$ and $h_2$) has the second most significant effect on the aerodynamic load of elevators.

This paper develops a new homogenization method for free vibration problems of periodic composite plates. In this new method, three-dimensional (3D) periodic plates are equivalent to Reissner–Mindlin plates with both effective stiffnesses and effective inertia coefficients. The effective stiffnesses for the dynamic problems are the same as those for the static problems, and they can be achieved by the equivalence principle of macro- and microscopic internal virtual work. To fully take the inertia effects into account, the effective inertia coefficients including the effective translational, translational–rotational and rotational inertias are determined by the two-scale equivalence principle of kinetic energies under three rigid modes. In addition, cell size effects in the thickness direction of composite plates are investigated by using the proposed method and the asymptotic homogenization method (AHM). Numerical experiments validate the effectiveness of the proposed equivalent method for different scale factors, and show that the rotational inertia cannot be ignored for out-of-plane deformations, especially for higher-order modes. Besides, numerical comparisons show that the cell size effects are not negligible when using the AHM to analyze the out-of-plane deformations, and three or more repeated unit cells in the thickness direction are required to ensure accuracy.

Time-history responses of the bridge induced by the moving vehicle provide crucial information for bridge design, operation, maintenance, etc. As inspired by this, this work attempts to provide a new paradigm for vehicle–bridge interaction (VBI) by highlighting the comparison of different deep learning algorithms applied to the prediction of time-history responses of the bridge under vehicular loads. Particularly, three deep learning architectures with few and measurable input features developed by using fully-connected feedforward neural network, long short-term memory (LSTM) network, and convolutional neural network (CNN) are proposed on the basis of the governing equation of bridge vibrations. Three VBI systems with various vehicle models are developed and further validated to produce reliable training data. To examine the accuracy of the predictive models, two advanced metrics are exploited for time-history estimate. Moreover, the proposed deep learning models are comprehensively investigated through a parametric study on the influential factors associated with the VBI system and network architecture. The results show that deep feedforward neural network (DFNN), LSTM network, and CNN can be applied in VBI analysis to estimate the bridge time-history response. The three neural networks have comparable prediction accuracies. When considering the irregularity excitation, CNN is found to be the most efficient predictive model, while DFNN needs the least training time under perfect bridge surface condition.

Buckling analysis of steel structures can be performed using either linear (LBA) or nonlinear buckling analysis (NLBA). Each method is only effective in particular conditions and improper use might lead to inaccurate predictions. Despite the extensive use of these two methods, there is a lack of research on the accuracy of each method and their limitations regarding the range of application. In this paper, these two methods are evaluated and compared for steel plate girders with a wide range of geometry and the limitations of each method are presented. The numerical modeling of steel plate girders is developed using Abaqus software. The numerical models are verified with the existing experimental results in the literature. An extensive parametric study is conducted using 123 models to investigate the effect of web height, web thickness and beam length on the results. The buckling loads predicted from the numerical models using different analysis methods are compared with those determined based on the AISC 360-16 and EN 1993-1-5 formulations and recommendations are made. Results indicate that while the nonlinear buckling analysis provides accurate predictions of buckling load and mode shape of steel beams, the linear buckling analysis is accurate only for the case of elastic buckling mode without tension field action. A new formulation is proposed to modify the LBA results in order to obtain the advantages of both analysis methods. In addition, based on the NLBA results, a much simple yet accurate equation is proposed to predict the buckling load using plate geometry and material properties instead of the complicated code equations. The accuracy of the proposed equation in comparison with the code equations is also demonstrated for 500 plate girders selected with random geometry.

With the ongoing development and deployment of medium-low speed maglev vehicles in China, it has become common to increase operational speeds from 100km/h up to 140km/h or even 160km/h, necessitating further studies and simulation models to understand the implications of these changes. This paper analyzes medium-speed maglev vehicle-track-girder coupling dynamic performance at a speed of 160km/h. First, a field dynamics experiment is carried out on the Changsha Maglev Express with a running speed of 80–140km/h. Then we introduce the distributed coupling simulation platform for maglev transportation system (MTS-DCSP) and the vehicle-track-girder coupling model, taking into account the complex vehicle structure, the guideway structure, and the Proportion Integral Differential (PID) levitation control system. Together, this platform and model can conduct a simulation of the complete process at scale and at all degrees of freedom to obtain accurate results. Our analysis of the results gives an accurate portrayal of the coupling dynamics properties and validates the coupling model. The results from the field experiments together with the coupling simulation demonstrate that the medium-speed maglev train can operate safely and stably within the range of 140–160km/h. While at 140km/h, however, the Sperling ride quality index (RQI) is about 2.5, which is within the Excellent grade range, at a speed of 160km/h, the Sperling ride quality index can increase to as high as 2.74, which is a grade of Good. Therefore, it is necessary to optimize the parameters of the secondary suspension system to improve the ride comfort of the maglev vehicle at 160km/h.

The buckling behaviors of drill string may cause serious down-hole problems, such as high friction during drilling, loss of weight on bit (WOB), and even drill string failure. This paper analyzes the dynamic buckling characteristics of drill string, considering the friction between drill string and wellbore. In the theoretical research, the key parameter expressions are determined, especially the contact behaviors of drill string and mathematical models are proposed, which include axial displacement, angular displacement and contact force. The numerical calculation results show that the influence of friction on the drill string buckling is mainly reflected in angular displacement. The influences of friction effect on the dynamic characteristics of drill string become greater with the increase of inclination angle, while become lower with the increase of drill string length. The friction effect appears to have insignificant influence on drill string condition with the accumulation of time. The comparison results indicate that the friction affects the action of axial load on drill string and delays the onset of buckling. On the other hand, the angular displacements decrease with drill string length increasing, while the axial displacements have an opposite effect. The research results provide theoretical references for studying dynamic buckling characteristics; furthermore, we can determine the methods and solutions to prevent drill string buckling based on this, and improve the safety of downhole drilling.

The outer skins of aerospace structures, which are frequently experiencing variations of temperature, are threatened by thermally induced vibration. Vibration in space has dangerous effects on the safety of structures and may result in structural failure. So, the construction of an active control system to suppress thermally induced vibrations is necessary. Active thermally induced vibration control of homogenous isotropic beams, and plates through magnetostrictive layers are presented here. Negative velocity feedback with a constant gain is employed to make appropriate strain in the magnetostrictive actuator layer. Ultimately, a closed-form solution is presented for thermally induced vibration control of the hybrid magnetostrictive-Aluminum beams and plates. Effects of material properties, thickness of magnetostrictive layers, and control gain on vibration suppression have been evaluated.

This work proposes an enhanced particle inerter device (EPID) capable of significantly enhancing the vibration control effect (VCE) of a conventional particle tuned mass damper (PTMD). EPID, an inerter is coupled to the PTMD device, that is, the inerter is attached to the damper cavity on one end and to the ground on the other, mainly using its mass amplification effect. To accomplish the goal, the EPID’s mechanical model is established first. Then, the system’s governing equation is derived based on the single degree of freedom (SDOF) system, and the EPID’s effectiveness is verified via inputting seismic excitation. Finally, the parameter analysis and multi-objective optimization design are carried out for EPID, and the superiority of the proposed multi-objective optimization design method compared with the traditional design method is verified. The results indicate that EPID can effectively minimize the main structure’s displacement and acceleration response. In particular, under the El Centro wave’s excitation, the vibration reduction rate of the dynamic responses (peak response and root mean square response) is close to 50%, which is over 35% increasing compared to PTMD, and its VCE is better for excitation band changes. At the same time, it is found that the lower the damper’s auxiliary mass ratio, the more obvious the enhancement of the inerter system’s VCE is, which brings about the lightweight design of the high-control effect of PTMD.

The out-of-plane buckling behavior of arches is closely related to the element torsional behavior. The traditional 12-degree-of-freedom second-order element stiffness matrix which uses a simplified element torsional stiffness GJ/$L$ (where $G$ is the shear modulus, $J$ the St. Venant torsion constant, $L$ the element length) may significantly underestimate the out-of-plane buckling loads of funicular arches. This paper presents a simple and effective exact matrix stiffness method (MSM) for the out-of-plane buckling analysis of funicular arches. The developed MSM uses a 14-degree-of-freedom second-order element stiffness matrix of three-dimensional beam-columns considering both torsion and warping deformations. The out-of-plane buckling analysis of funicular arches is performed by using the global structural stability stiffness matrix, which combines the transformed second-order element stiffness matrices. The proposed MSM with the exact 14-degree-of-freedom second-order element stiffness matrix for the out-of-plane buckling analysis is verified by comparing with some classical solutions of funicular circular and parabolic arches with box sections and I-sections. Further discussions show that the 14-degree-of-freedom second-order element stiffness matrix may be reduced to a simplified 12-degree-of-freedom form only by deriving the exact element torsional stiffnesses, which could be significantly larger than GJ/$L$ for members with large cross-sectional torsional stiffness parameters (especially open cross-sections).

This paper investigates the behavior of a pre-stressed arch under a sliding load, where the initial configuration can be obtained from the buckling of a straight column. The shape of the pre-stressed arch can be varied by increasing the end shortening. Subsequently, a sliding load is applied at a certain height level. The orientation of the applied load maintains the right angle with respect to the tangential line of the arch. By moving the load horizontally, the behavior of the arch can be explored. The governing differential equations of the problem can be obtained by equilibrium equations, constitutive relation, and nonlinear geometric expressions. The exact closed-form solutions can be derived in terms of elliptic integrals of the first and second kinds. In this problem, the arch can be divided into two segments where each segment is a part of a buckled hinged-hinged column mounted on an inclined support. The shooting method is employed to solve the numerical solutions for comparing with the elliptic integral method. The stability of the pre-stressed arch is evaluated from vibration analysis, where the shooting method is again utilized for solving the natural frequencies in terms of a square function. A simple experiment is set up to explore the equilibrium shapes. Poly-carbonate sheet is utilized as the pre-stressed arch. From the results, it is found that the results obtained from elliptic integral method are in excellent agreement with those obtained from shooting method. The equilibrium shapes from the theoretical results can also compare with those from the experiment. The pre-stressed arch can lose its stability and snap into an upside-down (inverted) configuration depending on the ratio of rise to span-length and loading height. The instability of the arch is not only detected during the pushing of the sliding load but a pulling load can also cause unstable behavior of the arch.

This paper focuses on the dynamic response, mainly dynamic amplification factors (DAFs), of partial-interaction composite beams (PICBs) based on the Timoshenko beam theory (TBT). By assuming that each sub-beam behaves as an independent Timoshenko beam, the governing differential equations of motion of the PICBs are derived under the action of dynamic load. The natural frequencies and modal shapes for simply supported PICBs are also extracted. For decoupling the governing differential equations of motion, the orthogonality property of two distinct vibration modes is checked and applied for further analysis. The modal superposition method is then utilized to derive the analytical expressions of transverse deflection, interfacial shear slip, and normal stresses of the PICBs subjected to the moving load. Finally, two test beams are organized to validate the proposed methodology. For this purpose, the results which are calculated by ANSYS and obtained from available methods are appropriately compared. The effects of shear connector stiffness and speed of the moving load on the DAFs of the PICB acted upon by the moving constant load are discussed.