A novel type of tuned viscous mass damper(TVMD)device incorporating eddy current damping and metal springs as its damping and spring elements, respectively, was developed. First, dynamic tests of the TVMDs were conducted to investigate their dynamic characteristics. Subsequently, four methods were proposed to identify the TVMD parameters from the test data: the peak point fitting method, hysteretic curve fitting method, time-history fitting method, and transfer function fitting method. The dynamic test results indicate that the TVMD exhibits the inertial mass amplification and damping enhancement effects. The spring and inerter elements demonstrate ideal linear behavior, while the damping element exhibits nonlinearity, primarily owing to the nature of eddy current damping and inherent friction in the TVMD device. The parameter identification results indicate that all four methods can reasonably determine the TVMD parameters. The transfer function fitting method can provide an equivalent damping coefficient useful for tuning design, while the other three methods can identify parameters of nonlinear damping models. The hysteretic curve fitting and time-history fitting methods exhibit improved accuracy in parameter identification, while the peak point fitting and transfer function fitting methods exhibit higher computational efficiency.

To address the issue that conventional disturbance observer(DO)design did not consider actuator saturation, which is prevalent in practical systems, a DO-based control(DOBC)strategy with anti-windup compensation is proposed. First, the reason of windup phenomenon in the conventional DOBC when the actuator is saturated is studied. Then, an anti-windup compensator is designed by minimizing the performance index, and patched to the DO so that the modified DOBC can effectively handle actuator saturation. Finally, local asymptotic stability analysis is performed on the resulting closed-loop systems. Comparative simulation results show that when there is actuator saturation, the proposed method has smaller errors in position tracking and disturbance estimation, and the designed compensator can maintain the DO states to be as close as possible to those without actuator saturation. This verifies that the proposed method is superior in anti-disturbance and anti-windup.

The limitations of conventional cable force optimization methods, which fail to automatically optimize and consider the overall performance of the bridge structure, as well as the drawbacks of extensive calculations, lengthy processing time, low efficiency, and slow convergence speed, when combined with intelligent optimization algorithms, should be addressed. Ansys and Matlab are used as the structural calculator and master control programs, respectively, with the minimum bending moment energy as the control objective.Moreover, the influence matrix and elite retention strategy are incorporated into the genetic algorithm to optimize the cable force during the bridge formation stage. This method can simultaneously account for the force characteristics of the main girder and pylon. Utilizing the influence matrix, the issue that each generation requires finite element evaluation can be resolved, thereby drastically reducing the amount of calculation. In addition to capitalizing on the benefits of the conventional influence matrix method, the proposed approach considers the iterative process of parameter selection and permits the addition of special constraint requirements to critical sections of the structure, thereby enhancing the realism of the optimization procedure. Furthermore, the introduction of the elite retention strategy enhances the convergence speed and stability of evolutionary iterations. Finally, a practical engineering application is utilized to validate the viability of the proposed method.

To accurately identify sensor faults caused by complex environmental conditions and ensure that structural health monitoring systems correctly perceive the structural state, a self-detection method for sensor nodes based on mean shift and sliding window techniques was proposed. The self-detection method comprises two stages, i.e., fault prescreening and fault self-detection. During the fault prescreening stage, the method rapidly identifies potentially abnormal data using the quartile method combined with the sliding window technique, significantly improving the efficiency of the method. During the fault self-detection stage, the method employs the mean shift algorithm to perform adaptive clustering of the abnormal data, effectively detecting various faults. Data from the Canton Tower were used to test the effectiveness of the method by setting four types of sensor faults, i.e., offset, drift, gain, and stuck. Then, the proposed method was compared with extremely randomized trees, random forests, support vector data description, and one-class support vector machines. Results show that the proposed method can detect the four aforementioned faults with high accuracy and computational efficiency.

A photoexcited switchable single-band/dual-band terahertz metamaterial absorber with polarization-insensitive and wide-angle absorption is reported. The function switching is realized by modulating the conductivity of the photosensitive GaAs embedded in the resonator, and the surface currents at different GaAs conductivities are extracted to physically explain the absorption mechanism of the metamaterial absorber. The results show that the absorber can realize switching from dual-band absorption at 0.568 and 1.442 THz with 99.08% and 99.56% absorptivity, respectively, to a shift single-band absorption at 0.731 THz with 95.43% absorptivity. The device has an intensity modulation depth of 61.4% and a frequency tuning bandwidth of 60.6%. With these values, the device can be used to fabricate intensity modulators and frequency-selective absorbers in the terahertz band. In addition, the proposed absorber exhibits polarization-independent and wide-angle absorption for transverse electric(TE)and transverse magnetic(TM)polarization waves. The realization of tunable metamaterial absorbers offers opportunities for mature semiconductor technologies and potential applications in active terahertz modulators and switchers.

To assess the combined risks of long-span suspension bridges under continuous wind loads and occasional earthquakes, a risk assessment framework for cross-sea suspension bridges based on improved Bayesian networks was proposed by combining the quantitative analysis of the structural damage probability and the qualitative assessment of the damage consequences during bridge operation. First, the damage degree of each component was obtained according to the characteristics of the suspension bridge and the results of wind and earthquake analyses. Then, the failure probability of the bridge structure was calculated using the theory of structural reliability. Finally, the risk assessment model of the suspension bridge based on improved Bayesian networks was proposed to evaluate the risk during bridge operation. The results show that considering the varying impacts of different bridge components, the bridge damage level can be categorized into four degrees based on its disaster resilience. Taking the Lingdingyang Bridge as an example, the maximum risk level under multihazard risks is level 3 according to the proposed method, which requires traffic restrictions and maintenance. Therefore, this method can guide the emergency management strategy of sea-crossing bridges in response to multihazard risks.

A comprehensive model based on continuum theory is adopted to conduct the parametric analysis of the primary resonance of the nonlinear vibration of spatial cable suspension bridges. This model can simultaneously account for the geometric nonlinearity of both the vertical motion of the deck and the vertical-horizontal motion of the cable. Based on this model and the multiple scale method(MSM), the modulation equations of the primary resonance responses are derived for spatial cable suspension bridges. Nonlinear coefficients in the modulation equations are determined to have notable influences on the maximum response amplitude of the primary resonance of the system and the hardening or softening characteristics of the investigated vibration mode. Meanwhile, system parameters, such as the inclination angles of the main cable and hanger, the sag-to-span ratio of the cable, and the tensile stiffness ratio between the deck and cable, can notably influence the nonlinear coefficient. The dynamic properties of the system can change dramatically in the form of sudden changes in the nonlinear coefficient of the symmetric vibration of the deck and cable if the parameter is located near the singularity, which should be avoided in the design of the system. This study can provide reference for the design of the bridge structure.

To develop comprehensive similarity indicators for assessing the fitting degree of hysteretic curves shape descriptors, widely used in image feature extraction, are introduced. A specific process is proposed to delineate the formation of indicators based on these descriptors, enabling the calculation of curve similarity between numerical simulation and experimental data. Following this process, an indicator is devised based on shape context. First, the similarities of the hysteretic loops in the numerical simulation curve are calculated. Subsequently, the weighted sum of these similarities is calculated to derive the similarity of the entire curve. To verify the effectiveness of the indicator, the Bouc-Wen model is utilized to conduct a numerical simulation study. Five parameters of the model are adjusted, resulting in the formation of 51 numerical simulation curves. Similarities of the curve, along with errors in the force peak point, energy dissipation, and stiffness, are calculated. The results show that the absolute values of Spearman’s correlation coefficients between similarity and errors all exceed 0.78, which has a strong correlation, thus verifying the feasibility of the indicator and the effectiveness of the process for forming the indicators.

To explore the benefits and potential of electricity and hydrogen as alternative fuels for regular buses, a mixed-integer planning model was constructed to determine the schedule optimization scheme for bus fleet replacement. The model was based on the comprehensive analysis of carbon emissions and the total cost of ownership from a life cycle perspective. Using actual operational data of buses powered by diesel, natural gas, hybrid, plug-in electric, and hydrogen fuel cells, the effects of uncertainty in the power mix, acquisition cost, hydrogen production, and hydrogen usage cost on the fleet replacement schedule were explored. The results reveal that plug-in electric buses are currently the optimal choice for bus fleet replacement. Given the current level of vehicle technology and hydrogen production, hydrogen fuel cell buses(HFCEBs)are advisable during bus fleet replacement. Until the production of blue or green hydrogen becomes commercially viable, promoting HFCEBs on a large scale by extending financial subsidies is not recommended. The proposed method can help authorities identify optimized bus fleet replacement options under specific constraints and desired objectives to promote green and sustainable development.

Asphalt mixtures were prepared in the laboratory using reclaimed asphalt pavement(RAP)at a 40% mass concentration to investigate the homogeneity characteristics of RAP during the mixing process, taking into account the mixing duration and aging rate. Specifically, titanium dioxide powder was incorporated into RAP binders as an identification tracer. Homogeneity indices were subsequently established to evaluate the homogeneity characteristics of asphalt mixtures. Computed tomography(CT)was used to create digital images of asphalt mixtures, and Mimics software was used to identify the components. Finally, a homogeneity evaluation system was established to assess the uniformity of both the components and RAP agglomerates. The results indicate that homogeneity is mostly influenced by the distribution of coarse aggregates, followed by asphalt binders and air voids. Homogeneity improvement is hindered by the formation of new agglomerates during the mixing process, whereas it is increased by prolonging the mixing time. A homogeneity evaluation system based on components and agglomerates can effectively reveal the principles governing homogeneity characteristics and provide a reference for the construction of high-quality recycled asphalt pavement.

To address the challenge of solving free vibration problems in beams with uniform cross-sections, beams with variable cross-sections, and Euler-Bernoulli beams with concentrated masses, an innovative method combining the Rayleigh method and the Monte Carlo method is introduced. This dual-method strategy offers a novel solution by first discretizing the continuous beam structure model, followed by employing the Monte Carlo method to determine the vibration modes of the beam structure. Subsequently, these identified vibration modes are integrated into the Rayleigh method to calculate the fundamental frequency and vibration modes. The process involves a meticulous comparison with the minimum value obtained during calculations to ensure the satisfaction of the convergence condition. The results show that this combined method achieves a maximum error of 10% or less in predicting the fundamental frequency across different calculation models. This accuracy level is well within acceptable engineering requirements. The control parameters for accuracy and time can be easily adjusted to meet various needs. The method, which is simple in theory and widely applicable, enables the quick and precise determination of fundamental frequencies and vibration modes for diverse beam structures.

A novel composite plate made of carbon fiber-reinforced polymer(CFRP)grids and bamboo scrimber, termed CBCP, was developed to enhance the mechanical properties of bamboo scrimber and reduce its anisotropic defects. To investigate the mechanical behavior of CBCP and assess the influence of its composite fabrication method, uniaxial tensile tests were performed on eight sets of CBCP tensile specimens, and pull-out tests were conducted on eighteen groups of CBCP pull-out specimens. Three similar constitutive models were selected to depict the bond stress-slip curves of the pull-out specimens. The critical anchorage lengths between CFRP grids and bamboo scrimber were determined. The effects of the number of CFRP layers, characteristics of transverse CFRP bundles, and anchorage length on the bonding performance between CFRP grids and bamboo scrimber were analyzed. The results reveal that integrating a CFRP grid can increase the tensile strength of bamboo scrimber, both parallel and perpendicular to the grain, by 35.77% and 135.20%, respectively. This enhancement effectively reduces the anisotropic defects of bamboo scrimber. The increase of the number of grid layers and the grid spacing can enhance the tensile performance of CBCP. With the increase of the anchorage length, the average interface bonding strength decreases exponentially while the peak load slip decreases linearly.