International Journal of Structural Stability and Dynamics

Installing mechanical dampers near the cable anchorage is a commonly used measure for suppressing rain-wind-induced vibrations (RWIVs) of stay cables. However, the high-mode vortex-induced vibrations (VIVs) are still observed on super-long stay cables installed with dampers. To this end, the study presents the combination of a negative stiffness damper (NSD) and Stockbridge dampers (SDs) to simultaneously suppress cable RWIVs and VIVs. In the proposed cable–NSD–SDs system, the NSD is installed near the cable anchorage to suppress cable RWIVs, and the SDs are installed at a higher location to suppress cable VIVs. First, the generalized characteristic equation of the cable–NSD–SDs system is derived for computing the coupled damping effect. Subsequently, a novel design method of an NSD and two SDs for mitigating cable multi-mode vibrations is proposed, and its effectiveness is numerically verified on an ultra-long stay cable of the Sutong Bridge. Finally, the control performance of an NSD and two SDs for the cable under white noise and harmonic excitations is emphatically evaluated and compared. Results indicate that the NSD–SDs system is quite effective for mitigating high-mode vibrations of super-long stay cables. Compared with the cable–NSD system, the cable acceleration response of the cable–NSD–SDs system is reduced by over 35%.

Compared with the marine structures such as sea-crossing bridges and offshore wind turbines, the marine artificial islands are bottom sitting structures and particularly sensitive to site conditions. Therefore, the study focuses on determining the effect of seabed site conditions and construction methods on the seismic performance of marine artificial islands. A seismic wave analysis model of seabed-seawater layer–artificial island coupling is developed by combining the self-programmed fluctuation analysis program and the dynamic analysis software. Firstly, the seismic response of marine artificial islands with different site conditions are analyzed by inputting P and SV waves. On that basis, the effects of incidence angles on the seismic response are explored. Then the study further explores the effects of different backfill materials and protective structures on the seismic response of the artificial island. Numerical results show that the silty soft soil layer can amplify the seismic response of seabed sites, and this amplification effect increases with the increase of the depth of silty soft soil layers. Moreover, the coral sand as backfill material can reduce the seismic response of marine artificial islands. The seismic response of marine artificial islands can also be reduced in the model with a protection structure. These results will provide some theoretical references for the site selection and construction method of marine artificial islands.

Thin-Walled Structures (TWS) play a crucial role in enhancing both the collision safety and lightweight characteristics of vehicles. Structural design and optimization have demonstrated significant potential in improving their crashworthiness and overall weight reduction. Several interconnected factors, including the cross-sectional shape and parameters of distinctive structural characteristics (known as induction grooves), impact the TWS’ resistance to collisions. Another critical aspect in the optimization of TWS design is striking the delicate balance between the surrogate model’s effectiveness and precision. Taking all these factors into account, this paper conducts an in-depth investigation into the cross-sectional shape, grooves, and other geometric attributes of various TWSs through a comparative analysis. It reveals that the thin-walled structure with a Double-Ribbed Rectangle cross-section (DR-TWS) proves to be the optimal choice, particularly in low-speed axial impact scenarios. Furthermore, we present an enhanced Least Squares Support Vector Machine (LSSVM) method, augmented with an adaptive $T$-distribution Sparrow Search Algorithm (TSSA), referred to as the TSSA-LSSVM surrogate model. The optimized design of the DR-TWS is realized through the integration of the TSSA-LSSVM surrogate model with the adaptive hybrid multi-objective particle swarm optimization (AHMOPSO) algorithm. This paper not only provides substantial theoretical support but also offers valuable guidelines for the application of TWSs in the automotive industry.

The friction-induced vibration of a continuous system consisting of two flexible beams in sliding contact to represent a brake system is studied in this paper. Besides the motion of relative sliding when the two beams are in contact, the separation of beams may also happen in the system dynamics. The complex eigenvalue analysis for the stability of the steady sliding state and the transient dynamic analysis for the characteristics (intensity and periodicity) of the steady-state responses of the system are carried out. Moreover, the results obtained using different numbers of beam modes are acquired and compared. It is found that only a few low-order beam modes need to be incorporated to get accurate results of the stability of the steady sliding state and the steady-state responses of the continuous frictional system, which therefore theoretically justify the omission of high-order modes of continuous structures when investigating the friction-induced vibration of continuous systems and thereby greatly reduce the computational cost. Additionally, the inclusion of the separation and re-contact behavior has a significant effect on the number of required modes for accurate steady-state responses compared with that when no separation is considered, which also verifies the important role of the separation and re-contact behavior in the system dynamics. Besides, a reduced dynamic model that can produce identical dynamic behaviors to those of the continuous frictional system is constructed, with the structural parameters of the reduced model derived from the several key low-order modes of beams.

This study investigated the nonlinear dynamic behavior of suspension bridge subjected to multi-frequency boundary excitations. Firstly, the nonlinear dynamic model of the suspension bridge subjected to multi-frequency boundary excitations is established. The in-plane vibration equations are derived based on Hamilton’s principle, taking into account the effects of geometric nonlinearity of the girder-deck and main cable as well as the stiffness of hangers. Secondly, the Galerkin method is used to solve for the frequencies and corresponding mode shape functions. Thirdly, the corresponding modulation equations are obtained based on the multiple scales method, and the 3:1 internal resonance between two symmetrical modes is analyzed. Combined with numerical analysis, the nonlinear dynamic behavior between modes of the suspension bridge is demonstrated through the frequency–response, force–response, and time history curves. The results indicate that the drift phenomenon appears when perturbing the amplitude and frequency of the different excitations, and the system exhibits intricate dynamic responses.

To investigate the vibration characteristics of long-span suspension bridges under the impact of high-speed trains, a method for conducting a time–frequency domain analysis of the dynamic response of a coupled system is presented in this study. First, the finite element model of a suspension bridge is established to conduct modal analysis, and simulation results are compared with measured data to validate the correctness of the bridge model. Subsequently, a multi-body dynamics model of a high-speed train is developed. Then, two approaches, the dummy method and flexible-track method, are employed to create the train–bridge coupled system. Finally, the flexible-track method is used to perform time–frequency domain analysis of the system under complex operational conditions. The research revealed that large-span suspension bridges exhibit lower natural frequencies. The vertical bending vibrations of the main beam have the potential to significantly impact train operations. Under the combined impact of cable tension and wheel–rail forces, the vibration patterns of large-span suspension bridges become notably intricate. The number of trains and their loading configurations both exert influence over the dominant frequencies and amplitudes in the PSD of bridges. In the complex traffic of large-span suspension bridges, the rational arrangement of travel lanes can reduce the possibility of resonance in the bridge–train system.

Structural dynamic response corrupts frequently due to the sensor malfunction. The loss of dynamic response will hinder the structural condition assessment. In recent years, significant efforts have been devoted to recovering the dynamic response during the linear elastic stage of the structure. However, relevant researches on the response recovery of damaged structures are rarely reported due to its strong nonlinearity. With the growing significance of post-disaster structural maintenance, it is critical to develop effective methods for recovering missing data in damaged structures. To this end, this paper proposes a dynamic response recovery method for damaged structures using residual learning enhanced fully convolutional networks (FCN), which can provide a baseline for the recovery of monitoring data in operational civil infrastructure. Specifically, a FCN incorporating residual learning and skip connections is designed to capture high-dimensional nonlinear relationships between input and output channels, thereby achieving the data recovery for any concerned channel. Then, a time–frequency domain evaluation mode is constructed, in which L2 norm is used to measure the difference of recovery results in the time domain, while instantaneous frequency is employed to evaluate the integrity of the spectral information of recovery results. Finally, a destruction test of an experimental arch was conducted, and the acceleration data under different damaged state were collected to investigate the feasibility of the proposed method. Besides, the recovery effects concerning input channel location and quantity, multi-channel response and cross-state recovery are examined. The results show that even in a severely damaged state, the proposed method effectively recovers the missing data. In addition, improving the correlation between input and output channels and increasing the number of input channels can further enhance the recovery accuracy.

Long-span bridges are the key component of the human transportation system, linking communities over vast obstacles. To ensure the safe operation of long-span bridges, structural health monitoring (SHM) is perhaps the most effective solution. This study takes a 430m four-span continuous girder bridge as an example and systematically presents an implementation example of the SHM system on the bridge regarding monitoring items, sensor placement, and sensor parameters. The monitoring data including operational load and bridge response are analyzed and the statistical rules of these monitoring data are presented. Besides, the modal parameters of the girder are tracked from long-term vibration monitoring data. Furthermore, the correlations between structural temperature and bridge response are analyzed, and the correlation formulas between bridge modal frequency, static responses, and structural temperature are finally given. The analysis results reveal significant seasonal variations in the responses of the continuously monitored girder bridge, offering valuable insights for data-driven assessment and early warning systems for bridges.

This paper aims to analyze the wave propagation in functionally graded carbon nanotube-reinforced composite (FG-CNTRC) beams placed on a viscoelastic foundation utilizing an improved first-order shear deformation theory (FSDT). The material properties are derived from the mixture rule. Four carbon nanotube distribution patterns are considered in the analysis. The extended Hamilton’s Principle is utilized to derive the governing wave equations for the CNTRC beam. A comparison between the present theory results and those in the literature is conducted for validation. The wave dispersion investigation is mainly based on the phase and group velocities. The results illustrate the wave propagation responses for the different CNT configurations. In addition, the influence of the CNTs volume fraction, foundation stiffness parameters, and damping coefficient on the wave characteristics is examined.

Due to the unobservable nature of underground construction and the destructive nature of horizontal directional drilling rigs with high power, this type of construction has become one of the most important causes of failure of long-distance natural gas pipelines. In recent years, horizontal directional drilling construction has caused pipeline accidents frequently. Once the accident occurs, the normal operation of natural gas pipelines cannot be ensured. Therefore, studying the damage mechanism of buried natural gas pipelines under horizontal directional drilling loads is important for the safe operation of pipelines. This paper combines the construction characteristics of horizontal directional drilling and the actual situation of natural gas pipelines to explore the relationship between horizontal directional drilling and pipelines. The force situation of pipelines after contacting directional drilling bits is analyzed by the drill bit-soil-pipe finite element model created in the ABAQUS software. The Johnson–Cook ductile damage model was utilized to determine the pipe’s damage condition. The sensitivity analysis results show that he order of the impact of key parameters on the dynamic response of the pipe is bit thrust $>$ wall thickness $>$ bit diameter $>$ pipe diameter $>$ bit speed $>$ number of bit teeth $>$ pipe operating pressure. Therefore, priority should be given to controlling the size of the drilling thrust and the speed of the drill bit to reduce the damage to pipelines by horizontal directional drilling construction. In addition, appropriately reducing the pipeline operating pressure can also reduce the risk of the pipeline being damaged by horizontal directional drilling construction.

The concrete shear keys (CSK) are the conventional component in the girder bridges to restrain the seismic-induced excessive displacement in the transverse direction. However, the failure of the CSKs is often observed in strong earthquake events, which indicates the inadaptability of the CSKs in such extreme circumstances. This study proposes a novel frictional sliding shear key (FSSK) to improve the seismic performance of girder bridge especially under the earthquakes with high intensities. The configuration and the working mechanism are first introduced to derive the governing equations and the hysteretic models. A design method is proposed on the premise of the safety of the pier columns to determine the parameters of the FSSK. The mitigation effectiveness of the FSSK is investigated through a case study of a typical isolated bridge subjected to a suit of 80 ground motion records with 12 levels of seismic intensities. Results demonstrate that the lateral force and the energy-dissipating ability of the FSSK both increase dramatically with the increase of its lateral deformation, which implies the FSSK could play a more significant role under strong earthquakes. The numerical results of the case study denote that the FSSK can prominently reduce the bearing deformation of the bridge model under strong earthquakes, while the seismic responses of the pier could be enlarged. Besides, the combination of the FSSK and the CSK could further decrease the bearing deformation and only slightly increase the pier responses at high seismic intensities. The findings of this study are aimed at improving the transverse performance of the girder bridges under strong earthquake.

This paper investigates the free vibration, buckling and dynamic stability of spinning bi-directional functional gradient materials (BDFGMs) conical shells. The material properties vary along the thickness and axial direction. The dynamics model is established based on the first-order shear deformation theory and the governing equations and boundary conditions of the conical shell are derived employing Hamilton’s principle. Subsequently, the differential quadrature (DQ) method is employed to discretize the governing equations into an algebraic system of equations for solving and analyzing the free vibration characteristics of the conical shell. The theoretical model’s accuracy and the solution method’s reliability are rigorously verified. The effects of temperature, functional gradient index, and rotation on the vibration characteristics, traveling wave vibration and critical speed of the conical shell in a thermal environment are systematically explored through numerical analysis. The results indicate that both the material gradient index and temperature increase lead to a decrease in the shell’s natural frequency. For the spinning BDFGMs shell, elevated temperature causes the occurrence of trailing wave vibration to advance to the critical speed. Centrifugal force emerges as the primary factor influencing the critical buckling load and unstable region variation of the spinning shell.