In this investigation, deformations of a deep foundation pit in hard rock strata, respectively, under delayed and in-time supporting schemes of one-layer transverse reinforced concrete bracings at the top of the foundation pit, one-layer steel bracings at a depth of 8 m, and one-layer prestressed anchorages at a depth of 22.5 m during excavation were characterized according to lateral deformations of the foundation pit, settlements of the surrounding ground, and axial forces of the steel bracings according to numerical calculations and on-site monitoring. Numerical calculation results showed that the maximum lateral deformations of the foundation pit and settlements of the surrounding ground were, respectively, 10.34 mm and 8.49 mm at an excavation depth of 31 m, which were obviously larger than those under in-time supporting. Meanwhile, under delayed supporting conditions, lateral deformations of the foundation pit and settlements of the surrounding ground were far less than the allowed values, respectively, being 0.3% and 0.15% of the excavation depth, required in the Chinese standard of GB50007-2011, indicating that the foundation pit under delayed supporting conditions had good stability. Therefore, when excavating deep foundation pits in hard rock strata, proper delayed supporting schemes could be considered so that strengths of the surrounding hard rocks could be utilized to the fullest, and at the same time, more spaces for excavation could be freed up, and construction duration and construction costs could thus be lowered.

The benefits of noise can be found in nonlinear systems where a type of resonances can inject the noise into systems to enhance weak signals of interest, including stochastic resonance, vibrational resonance, and chaotic resonance. Such benefits of noise can be improved further by adding some items into the nonlinear systems. Considering the time-dependent memory of fractional-order derivative and time-delay feedback which makes the nonlinear systems take advantage of their historical information and makes the output of nonlinear systems affect the input by feedback control, therefore, we attempt to design the model of stochastic resonance (SR) enhanced by both fractional-order derivative and time-delay feedback. Among them, fractional-order derivative and time delay would reinforce the memory of nonlinear systems for historical information and feedback would use the output of systems to control the systems precisely. Therefore, we hope that their advantages would be fused to improve the weak signal detection performance of SR further. Then, it would be applied to bearing fault diagnosis and compared with that without fractional-order derivative and time-delay feedback and even other diagnostic methods. The experimental results indicate that the SR enhanced by fractional-order derivative and time-delay feedback where a local signal-to-noise ratio is designed as the objective function to optimize these tuning parameters of the proposed method could enhance early fault signature of bearings and outperform that without fractional-order derivative and time-delay feedback and even infogram method.

In wind turbine systems, bolted connections are frequently subjected to gravitational and centrifugal loads transmitted by the blades during operation. This can lead to the attenuation of bolt preloading, resulting in bolt loosening or uneven loading, which in turn affects the service life of the generator unit. Therefore, the study of bolt preloading variations is crucial. However, there are numerous factors influencing bolt preloading, and the existing techniques struggle to precisely assess bolt preloading. This paper proposed a bolt preloading evaluation technique based on the hammer modal method. Focusing on the 42CrMo4 bolted connection of a pitch bearing, a test platform for bolt preloading assessment is constructed. Hammer modal tests are conducted under various preloading forces. By combining finite element modal analysis, the correspondence between preloading changes and the bending frequencies and modes of the bolted connection is obtained. The research illustrated that with changes in bolt preloading, variations occur in coherence, phase, and natural frequencies of frequency response functions. The fundamental correlation between bolt preloading and the second-order bending frequency can be utilized to assess changes in preloading. Furthermore, the applicability of this method has been validated, offering a reference for evaluating bolt preloading.

This study presents the design of an integrated floating breakwater-wind turbine device. The hydrodynamic performance was evaluated in a two-dimensional water tank under typical operating conditions to investigate its kinematic response and wave dissipation effect, while the original design was improved and optimized to enhance the overall performance of the integrated device. The improved integrated device had lower heave and sway motion amplitudes, better wave resistance, and better wave dissipation performance than the prototype. The improved integrated device can effectively reduce costs and optimize the allocation of resources by using a floating breakwater as a carrier for wind power generation and has broad application prospects.

The structure of soil refers to the properties and arrangement of soil particles and pores, as well as their interactions, which have a significant impact on the mechanical behavior of soil. Clarifying the strengths and weaknesses of soil structure can effectively ensure engineering safety during designing. In this study, the structural soft soil in the Wujiaba area of Kunming City was studied. A comprehensive structural parameter γ was proposed by analyzing one-dimensional consolidation test data, which consider both the moisture content and yield stress. Due to its high moisture content and lacustrine features, the soft soil in Kunming possessed obvious structural characteristics. As the moisture content increased, the structural characteristics of the soft soil gradually weakened, making it more prone to compression failure. Moreover, the initial consolidation pressure decreased with the increase in moisture content. And the soft soil was more susceptible to deformation failure with higher moisture content. The conclusions drawn from this study have important implications for predicting the settlement of layered soft soil foundations.

Roadheader is important large equipment in coal mining. The roadheader has a higher failure rate due to its harsh working environment and high working intensity. In this paper, we proposed a fault diagnosis method based on reference manifold (RM) learning by using the vibration signals of roadheader in the actual production process. First, health and fault vibration signals were extracted from a large number of field data. The abovementioned signals were analyzed by time domain and wavelet packet energy analysis and got the characteristic parameters of the signal which can form the characteristic parameter sets. RM method can reduce the dimension of the characteristic parameters, and the projection of different characteristic parameters was obtained. Finally, the health parameters and fault parameters of different characteristic parameters were segmented by linear discriminant analysis (LDA). It could get the different segment area range of characteristic parameters for health signals and fault signals. This method provides a set of fault analysis ideas and methods for equipment working under complex working conditions and improves the theoretical basis for fault type analysis.

In order to investigate the vibration characteristics and propagation mechanism of ground vibrations induced by high-speed train passing through the viaduct, a field experiment is carried out, and the measured data is deeply analyzed. Besides the independent time domain and frequency domain analysis, the continuous wavelet transform (CWT) is performed on the vibration signal to analyze the energy distribution characteristics of ground vibrations from the view of time-frequency synchronous analysis. The experimental results show that the ground vibrations have obvious nonstationary characteristics; the first dominant frequency of ground vibration is concentrated between 40–55 Hz, which is affected by the excitation frequency of the train wheel axle and the peak frequency of wheel-rail interaction force. The ground vibrations attenuate gradually as the distance from the railway track increases, in which the high-frequency components above 50 Hz attenuate faster, low-frequency components below 8 Hz continuously decay in the near field, and medium-frequency components within 8−50 Hz decay slower with a longer transmission distance. Compared with traditional methods, time-frequency synchronous analysis of ground vibration signals is more accurate and intuitive, and the CWT can be used as a promising method in the analysis of ground-borne vibration from high-speed railway.

The failures of steel guides can excite complex and intense transverse oscillations of hoisting containers in the mine hoisting process. The present paper mainly contributes to reveal the response characteristics of the transverse oscillations of mine conveyances excited by various faults such as interface misalignment, local bulge, orbital gap, bending deformation, and orbital tilt. First, a rigid-flexible coupled virtual prototype model between the conveyance and the steel guide was established. Subsequently, the vibration response characteristics of the container under various single and coupling excitations were simulated and analyzed. Eventually, a new type of roller cage shoe with a magnetorheological damper was put forward to decrease the transverse impact responses. Based on the hyperbolic tangent model of magnetorheological dampers, a semiactive fuzzy PID method was studied to explore the vibration suppression of the container. The results showed the fuzzy PID method can play a good role in the vibration reduction. This paper can give a fine scheme for the virtual simulation and semiactive vibration control of the mine hoisting system.

This study proposes a new methodology, based on the optimization procedure by a metaheuristic algorithm, for designing a hybrid vibration control system to mitigate the dynamic response of buildings under nonstationary artificial earthquakes (NSAEs). For illustration purposes, a 10-story shear building is studied. The hybrid control system involves the use of an MR damper (MR) and a tuned mass damper (TMD) located in different places of the structure. To describe the behavior of the MR, the modified Bouc–Wen model (MBW) was used. To calculate the damping force of the MR, the clipped optimal control associated with linear quadratic regulator (LQR), CO-LQR, was considered. The optimization was performed using the whale optimization algorithm (WOA) and seismic load generated by the Kanai–Tajimi spectrum. Different control scenarios were evaluated: MR-OFF, MR-ON, CO-LQR, STMD, and CO-LQR (MR + TMD) to determine the best control scenario that can effectively control the structure. Overall, the optimized hybrid control scenario (MR + TMD) was the only one able to adapt all story drifts to the control criterion of the consulted normative. Then, CO-LQR (MR + TMD), designed via the methodology proposed in this work, proved to be the best alternative to control the seismic response of this building.

The aim of this study is to compose a corotational finite element formulation for space frames with geometrically nonlinear behavior under dynamic loads. Using a moving frame through three successive rotations similar to Euler angles is one of the oldest techniques; however, there are still some gaps that require attention, mainly due to singularity. Hence, alternative techniques had been developed, sometimes elusive and computationally expensive. In this paper, we went back to the old technique and filled the gaps. Three-coordinate systems are used, i.e., the fixed global coordinate system, the fixed local coordinate system that is attached individually to every element, and the corotational local frame for each element that moves and rotates with the element. The deformation is always small relative to the corotational frame. The successive rotations between different coordinate systems are expressed using Tait–Bryan angles. Lagrange’s equation is used to derive the equation of motion, and the stiffness and mass matrices are obtained using the Euler–Bernoulli beam model. A MATLAB code is developed based on the Newton–Raphson method and the Newmark direct integration implicit method. In traditional techniques, singularity is attained when any rotation angle in the fixed local frame approaches π / 2 , and if any is greater than π / 2 , the techniques could fail to specify the location of the element. In this paper, each case is treated with a proper procedure, and special handling of trigonometric formulations prevents singularity and correctly specifies the location of elements in all situations. Different examples of beams and frames are analysed. While the method is not intricate, it is timesaving, is highly effective, provides more stable and robust analysis, and gives sufficiently accurate results. Compared to the parametrization of the finite rotations technique, the method has a significant reduction in the convergence rate because it avoids the storage of joint orientation matrices.