Adaptive decomposition, reconstruction, and denoising of bridge structure monitoring signals are critical parts in the research field of bridge health monitoring. To provide efficient and effective time-frequency domain denoising methods for these signals, an Adaptive Variational Mode Decomposition and Reconstruction (AVMDR) method was proposed for signal denoising, which can overcome the disadvantage of VMD (Variational Mode Decomposition) type methods that the number of decomposition components needs to be determined inadvance. The Empirical Mode Decomposition (EMD) method was introduced to adaptively determine the number of decomposition components, and then the Multi-scale Principal Component Analysis (MSPCA) was used to denoise each component and reconstruct the signal. The denoising performance of the proposed AVMDR method was validated and compared using both simulated signals—linear stationary and nonlinear non-stationary signals with varying noise levels—and real signals obtained from two cable-stayed model bridges. The results indicate that the AVMDR method outperforms other commonly used methods in terms of denoising performance, achieving optimal scores across all denoising performance evaluation metrics. Moreover, the AVMDR method can effectively retain more structural information while eliminating noise.

To solve the problem of a lack of theoretical guidance in the simplification process of space pipe truss structure, the equivalent bending moment of inertia of space pipe truss structure was deduced by using the knowledge of material mechanics, and the corresponding calculation formula was put forward. Based on the principle of equal torsional strain energy, the formulas for calculating the equivalent thin plate thickness of the web members and the top and bottom lateral bracing of the pipe truss were derived, and the continuous equivalent section was constructed. The formula for calculating the equivalent torsional moment of inertia of the space pipe truss structure was proposed by using the thin-walled bar theory. The cantilever method was used to verify the accuracy of the calculation formula of equivalent moment of inertia. The equivalent analysis of the tennis court of Lanzhou Olympic Sports Center was carried out. The results show that the formula for calculating the equivalent moment of inertia is reasonable, and its error is within 4% compared with that of the cantilever method. Under the action of deadweight, the errors of the maximum displacement value and the maximum stress value between the original structure and the simplified structure of the tennis court are less than 9%. The vibration modes of the first five steps of the original structure are similar to those of the simplified structure, and their errors of the natural frequency are less than 4%, so the simplified structure has high accuracy.

To analyze the seismic response of different forms of long-span arch bridge-track systems, four different forms of arch bridges, namely 112 m basket handle arch bridge, 140 m steel box tied arch bridge, (24+160+24) m tied arch bridge and (52+382+52) m steel box arch bridge, are used as examples. The study revealed the dynamic characteristics of long-span arch bridge-track systems under seismic action and explored the effects of seismic waves, seismic intensity, and traveling wave speed on the seismic response. The results show that the stress envelope of the rail under seismic uniform excitation is antisymmetrically distributed, with the maximum value appearing near the end of the beam and the maximum axial force of the arch rib at the arch foot. There are large differences in the dynamic characteristics of the system under different spectral characteristics of seismic wave excitation. The change in seismic intensity mainly affects the rail stress near the end of the beam, and has less effect on the middle beam section. The traveling wave effect has a significant impact on the seismic response, with a significant increase in the axial force of the arch rib. The maximum stress in the rail increases by 149.2% compared to the seismic uniform excitation, and the longitudinal force in the rail at the middle of the span increases significantly, up to 503.4 MPa. Furthermore, the stress in the rail is greater when the apparent wave speed is smaller. Similarily, the stress on the rail increases as the traveling wave speed decreases. As the traveling wave speed increases, the stress distribution on the rail gradually approaches that of consistent excitation.

The acoustic black hole (ABH) effect, which decelerates the propagation of elastic waves and suppresses boundary reflections, presents a novel mechanism for vibration energy harvesting. A dual-ABH piezoelectric beam energy harvester has been designed for application in railway track systems. A semi-analytical electromechanical coupling model was developed using the energy functional variational principle and Gaussian expansion method. Validation was conducted through finite element simulations. Under train-induced loading, energy harvesting behavior was investigated with respect to ABH geometric parameters and terminal mass. Four principal energy harvesting bands were identified within the 0~1500 Hz range, yielding a peak output voltage of 4.83 V and a maximum efficiency of 2.23%. Optimal energy conversion was achieved when the piezoelectric patch length equaled half the bending wave wavelength of the host structure. Efficiency was further improved by strengthening the ABH effect or through appropriate tuning of the terminal mass.

At present, the layout plan of cable force sensors for cable-stayed bridges usually selects different specifications of cables and cables with large cable forces or significant stress amplitude changes for monitoring, lacking a scientific method of cable force sensor placement. This study proposes an optimal cable force sensor placement method for long cable-stayed bridges based on sensitivity analysis, aiming to identify the structural damage in cable-stayed bridges. The proposed method is based on the sensitivity analysis of cable force to structural damage, and a genetic algorithm is used to obtain the minimum number and placement position of cable force sensors that required to identify structural damage in cable-stayed bridges. In addition, engineering experience and sensor placement habits are fully considered when determining the initial population and constraint condition of genetic algorithm. The proposed method is applied to the numerical model of the Yuxi River Bridge, and the optimal cable force sensor placement for cable-stayed bridges with the target of damage identification is realized. Moreover, the influence of sensitivity threshold on the optimal placement of sensors is discussed.

A nested Chebyshev polynomial surrogate model and an improved particle swarm optimization (IPSO) algorithm are proposed to identify the bounds of input and structural parameters in the inverse dynamical problem of flexible multibody systems with interval uncertainty. Specifically, the dynamical model equations for a multibody system incorporating interval uncertainty are established. The interval midpoint and interval radius are used to describe the given output response with interval uncertainty. The Chebyshev polynomial surrogate model is established for the output response of a flexible multibody system. The IPSO algorithm is used to reverse the interval midpoint and interval radius of the unknown parameters in the flexible multibody system. The Chebyshev polynomial surrogate model is used in the proposed method to approximate the original interval uncertain flexible multibody system, thereby significantly reducing the computational cost of the optimization process of the IPSO algorithm.

The present study aims to improve the aerodynamic stability of a single-axis PV tracker. The effects of turbulence intensity, natural frequency and damping ratio on the aerodynamic stability of the single-axis PV tracker are studied by a sectional model wind tunnel test to reveal the sensitivity of these parameters. The results show unstable torsional vibration of the single-axis PV tracker system in a large tilt angle range with strong aerodynamic coupling and self-excited characteristics. The critical wind speed for the unstable vibration is low. The critical wind speed is high at 0° tilt angle (PV module is horizontal). The increase of turbulence intensity leads to the increase of the unstable vibration tilt angle range, which is not good for the aerodynamic stability. Increasing the damping ratio has an inconsiderable effect on increasing the critical wind speed at small tilt angles (0° and 5°). However, it works well when the tilt angle is larger than 15°. With the increase of natural frequency, the critical wind speed is significantly increased at all tilt angles.

Ambient vibration energy harvesting technology can provide green self-powered supply technology for low-power electronic devices in the Internet of Things (IoTs). In response to the shortcomings of traditional linear cantilever beam energy harvesters with high natural frequencies and low energy capture efficiency, a tuning fork-shaped cantilever beam structure is proposed to collect vibration energy in the environment. This overcomes the disadvantage of traditional cantilever beam structures, where the free end section, due to its small strain during vibration, is not conducive to energy collection. As a result, the energy harvesting efficiency of the system is significantly enhanced. The Lagrange equation is used to establish the dynamic equation of a tuning fork piezoelectric cantilever beam under harmonic excitation. The influence of structure size, added tip-mass and load resistance on the energy capture characteristics of the system are analyzed through a combination of the theoretical analysis, finite element simulation (FEM) and experimental results. The results show that introducing a bifurcation structure at the free end of the cantilever beam can reduce the fundamental frequency of the system, proving that the tuning fork piezoelectric cantilever beam energy harvester is more conducive to low-frequency ambient vibration energy harvesting. When the acceleration excitation amplitude is 0.5 m/s², the peak output power of the system is 7 mW. Further optimization of the structure by adding a 20 g tip-mass at the free end increases the peak energy capture output power to 18 mW. Design a piezoelectric energy capture interface circuit to collect and convert electrical energy directly to power LED lights (light emitting diodes). Experimental results can simultaneously light up 50 LED lights. The research results can provide theoretical support for energy collection in low-frequency vibration environments and for achieving self-powered design of low-power IoT sensors below 80 Hz.

A structural system for energy dissipation and shock absorption with displacement amplification damping walls across multiple stories is presented. According to structural characteristics of the cable-bracing displacement amplification damping wall, the deformation and force characteristics of the device were analyzed, and presented theoretical formulations for the cable-type damping wall system’s damping force and energy dissipation. The simplified numerical model was established, the parameters that affect the structural performance indicators were analyzed in detail, the fixed-point theory was used to design the optimal parameters of the cable-type damping system, and the energy-dissipating deformation magnification equation was derived to quantify the degree of damping efficiency. A 30-story concrete frame core tube was analyzed for the seismic time-history analysis, though the vibration absorption efficiency of the three damping wall layout schemes of displacement amplification damping wall installed in single story and cable-bracing displacement amplification damping wall system installed in multi-story were compared, it is found that the cable-bracing displacement amplification damping wall system installed in multi-story has a better shock-absorption effect.

Aiming at the problem of secondary impact caused by mismatching parameters of traditional isolation system with displacement restrictor, firstly, a mechanical model of the quasi-zero stiffness (MMPDQZS) isolation system was established by using the opposed disc spring as the negative stiffness component and the repulsive permanent magnets was used to adjust the nonlinear positive stiffness. The static characteristics of the system were analyzed. Then, the mathematical model of MMPDQZS isolation system was established. The influence law of different damping parameters on the impact isolation performance of MMPDQZS isolation system was analyzed. The impact characteristics were compared and analyzed through simulation and experimental study for without and with equivalent linear displacement restrictors and MMPDQZS limiters. The results show that for any initial clearance, there is an optimal viscous damping ratio that minimizes the system’s buffer coefficient. Smaller initial clearances generally lead to better impact isolation effects. Considering different initial clearance, the damping ratio of power-law fluid damping is 0.02, the velocity correlation index obtains the optimal buffer coefficient within the interval [2.2, 2.3], and the optimal initial clearance is when the clearance is equal to 4 mm. For any initial clearance, the buffer coefficient is proportional to coulomb damping, and smaller initial clearances result in better buffering performance. Compared with the equivalent linear limit isolation system, MMPDQZS limit isolation system can not only effectively limit the relative displacement, but also greatly reduce the buffer coefficient of the system and improve its impact resistance.