Reducing the seismic acceleration response of nuclear containment and ensuring the safety of nuclear power equipment under strong earthquakes is of practical significance for improving the seismic toughness of nuclear containment. Tuned mass damper (TMD) can effectively reduce the wind vibration response, but it has the disadvantages of narrow frequency band and low damping efficiency for seismic response control. By combining TMD with inertial volume, a tuned mass damper inerter (TMDI) is proposed to reduce the seismic acceleration of nuclear containment. Based on the performance requirement design idea and H_∞ optimization criterion, an optimal parameter design method for TMDI was established. On this basis, a numerical simulation method is developed by using the substructure idea combined with ABAQUS and Matlab, and the finite element simulation of the seismic response of nuclear containment under TMDI control is realized. The validity of the theoretical analysis is verified by the TMDI seismic control example of a finite element model of a nuclear containment. The results show that the peak acceleration absorption rate of the top of the nuclear containment is 46.1% when TMDI is used, and the tuning mass required when TMDI reaches the same damping index is reduced by 28.2%.

Conical pipe joints are widely used in pipeline systems of various aerospace vehicles, and the stability of their sealing performance directly impacts the reliability of the aircraft's operation. Engineering experience has shown that setting circular grooves on the conical surface can improve the stability of the sealing performance of conical pipe joints. However, there is currently a shortage of experimental data to support this viewpoint. This article takes a 74° conical pipe joint commonly used in aircraft engines as the object and demonstrates rotational bending fatigue tests that circular grooves can significantly improve the stability of the sealing performance of conical pipe joints under vibration condition. On this basis, this article verifies through finite element simulation that the edges of the annular groove can generate contact pressure concentration bands, which serve as a form of line sealing. Thus, a qualitative explanation is provided for the mechanism of improving the stability of sealing performance by the annular groove. This study provides a reference for improving the design of conical pipe joints and other forms of static sealing structures.

The Yellow River floodplain, covering an area of 250000 km² located in northern China, is a densely populated and economically developed region with a high level seismic background activity. In recent history, numerous earthquake-induced liquefactions occurred in this floodplain, however, relevant investigations and research are also lacking. So far, the knowledge of earthquake-induced liquefaction in the Yellow River floodplain is almost blank. In 2023, the Pingyuan M_S5.5 earthquake occurred in Shandong Province and induced soil liquefaction in the Yellow River floodplain. Through post-earthquake investigations, it is the first time that a case of real earthquake-induced liquefaction in the Yellow River floodplain has been analyzed in this paper. The characteristics of liquefaction induced by this earthquake have been obtained. The main points are as follows: this earthquake mainly induced soil liquefaction in silt and silty soils for 91% of sites in the total. The depth range of liquefied soil deposits is mainly of 7~12 m. The largest depth of liquefied soil deposit was confirmed at least 14 m, and possibly at an even deeper one. The depth of liquefied soil is beyond the common range of that in previous earthquakes. Liquefaction sites are mainly observed in the epicentral range of 6~12 km and are located in the seismic intensity 5 region and the boundary of intensity 6 region, which is significantly different from previous investigations. The abnormal distribution of liquefaction sites is closely related to the effect which is induced by the exclusive “highland-slope-lowland” microtopography in the Yellow River floodplain. In a moderate earthquake, the liquefaction in the Yellow River floodplain has induced moderate damage and has an especially different characteristic. It can be concluded that more severe liquefaction hazards may occur in large earthquakes. Therefore, it is urgent to develop a specific analysis procedure and evaluation method for soil liquefaction in the Yellow River floodplain. The work in this paper can improve the understanding of soil liquefaction during small and moderate earthquakes and provide firsthand information and new clues for research on soil liquefaction in the Yellow River floodplain.

Clutching inerter damper (CID) has been extensively studied in structural vibration control recently. Because the passive CID device does not take into account flywheel speed reset and cannot achieve an ideal piecewise model, its control performance is limited. Therefore, this study explores the semi-active implementation of the ideal CID model. This paper begins with a comparative study of the ideal and passive analytical models of CID, providing insight into the performance differences and limitations of the two models. Subsequently, an electromechanical clutching inerter damper (ECID) scheme is proposed, which includes energy harvesting and variable inertance. The implementation of the electrical inertance, flywheel speed reset, and energy recovery functions are also discussed, and an electromechanical hybrid simulation model of the ECID is established. This paper thoroughly examines the control and energy recovery performance of the ECID through theoretical and simulation analyses. It explores the effects of resistance and capacitance in the ECID circuit on system performance and demonstrates that the ECID has significant vibration control and energy recovery capabilities. This study presents a comprehensive scheme for the implementation of CID, variable inertance, and energy recovery, which has theoretical reference significance for the development of self-powered semi-active variable inertance devices.

In order to limit the excessive relative displacement between pier and beam, a latticed long-stroke restrainer(LLSR) based on shape memory alloy (SMA) bar is proposed on the basis of single long-stroke shape memory alloy restrainer (LSR). The device consists of SMA alloy bar with excellent superelasticity and re-centering performance, MC nylon, steel pipes and strips or plates. SMA bars can consume ground motion energy and provide re-centering capability. The MC nylon and steel pipe form an anti-buckling system to prevent the SMA bar from buckling under pressure. Firstly, the structure and working mechanism of single long-stroke shape memory alloy damper and lattice long-stroke shape memory alloy damper are described. Secondly, the tensile test of SMA bars under different heat treatment temperature was carried out to determine the SMA bar with the best superelasticity, which was then used as the inner core of the LSR. Then, the axial tension and compression experiment of a single LSR was conducted to further study its mechanical properties. Finally, based on the experimental data of the LSR and the finite element software of ABAQUS, the numerical analysis and parameter analysis of the LLSR were carried out, and the corresponding design method was proposed according to the results of numerical analysis and parameter analysis. The research shows that LLSR not only has stable energy dissipation capacity but also has good re-centering ability.

The dynamic response of compacted coarse-grained soil as a filling material for the surface layer of railway subgrade bedding is crucial for the overall performance of the subgrade structure under long-term cyclic train loads. This study conducted a series of cyclic triaxial tests to investigate the effects of fine content, confining pressure, and cyclic stress amplitude on the accumulated behavior of coarse-grained soils. The test results indicate that under the same cyclic loading conditions, specimens with higher fine content exhibit less accumulated axial strain. Furthermore, coarse-grained soil specimens exhibit less accumulated axial strain under higher confining pressure or lower cyclic stress amplitudes. Subsequently, the plastic shakedown limit of coarse-grained soils with different fine contents was determined based on a universal shakedown criterion. The results demonstrate that the plastic shakedown limit of coarse-grained soil specimens gradually increases with an increase in fine content. Under higher confining pressure, the corresponding plastic shakedown limit of coarse-grained soil is also higher. Additionally, by plotting the stress state corresponding to the plastic shakedown limit of coarse-grained soil on the plane of p-q, a relationship was established between the coefficient of fine content (FC) and the model parameters in the existing shakedown criterion. A united plastic shakedown criterion is then proposed for coarse-grained soils with different fine contents. The conclusions can provide a theoretical foundation for the design and stability assessment of railway subgrades.

The current seismic design codes for bridges primarily rely on design response spectra derived from far-field observational records, which fail to accurately reflect the ground motion characteristics and structural seismic response characteristics in near-fault regions. As a result, the seismic design for bridges in near-fault regions may be unsafe. To address the issue, near-fault ground motion time histories are selected from the Pacific Earthquake Engineering Research Center (PEER) database based on principles including source distance, moment magnitude, and peak ground acceleration(PGA). Average spectra are calculated using site foundation conditions and PGA as grouping principles, and then calibrated using a least-squares piecewise fitting method. This process yields statistical recommendations for three key parameters of the near-fault horizontal design gauge response spectrum: amplification factor, attenuation index, and characteristic period. Finally, adjustments were made to propose a gauge response spectrum that considers near-fault earthquake characteristics, providing a basis for incorporating near-fault ground motion effects into China's seismic design codes for bridges.

Proton and heavy ion therapy facilities have garnered significant attention and widespread application in recent years due to their high-precision treatment capabilities. Hospitals are often located in urban areas with busy traffic, raising concerns about the potential impact of the road traffic environment on the normal operation of these planned high-precision devices. It necessitates a detailed feasibility assessment of the construction proposal for the project. This paper focuses on an actual engineering project, employing on-site real measurements to study the frequency characteristics of site vibrations induced by road traffic loads and the decay pattern of peak accelerations. A three-dimensional finite element model of the actual structure was developed to analyze the dynamic response of the proton and heavy ion therapy platform influenced by traffic conditions. The findings indicate that the vibrations generated by road traffic are primarily concentrated in the 5 Hz to 20 Hz range. High-frequency vibrations decay rapidly with distance. Peak accelerations of traffic loads at various distances from the road's centerline exhibit a multi-level amplification phenomenon, and in some areas, the peak acceleration may exceed that of the vibration source itself. Through 1/3 octave band analysis, the environmental vibration frequencies mainly affecting the central area of the proton and heavy ion facility range between 5 Hz to 20 Hz and 40 Hz to 60 Hz. Z-vibration level analysis shows that the platform's environmental vibration dynamic response meets the predefined standards for dynamic response design. This study provides a reference for the feasibility demonstration of construction plans considering the impact of traffic environments on facilities requiring high-precision equipment platform stability.

The main task of the building structure array is to record the failure process of civil engineering structures in detail, and to provide structural response information for many related studies such as seismic design, seismic damage assessment, and earthquake safety alarm. However, due to the constraints of economic cost, field testing technology and data processing level, it is unrealistic to deploy sensor monitoring equipment on all floors of the entire structure, so how to obtain the most complete structural information with the least number of sensors is the purpose of optimizing the layout of structural array sensors. Considering the advantages and disadvantages of the effective independent method and the modal kinetic energy method, a unit stiffness energy-driving point retention method was proposed, considering the advantages and disadvantages of the effective independent method and the modal kinetic energy method. In this method, the unit stiffness modal energy is used as the information matrix, and the principle of effective independence method is used to screen the measurement points, so as to ensure that the high-energy measurement points maintain linear independence to the greatest extent. Finally, taking a steel frame as an example, the proposed method, the effective independence method, the modal kinetic energy method and the unit stiffness method are used to lay the sensors on the model respectively, and the modal assurance criterion and the Fisher information matrix criterion are used to evaluate the layout results of the four methods. The results show that, compared with the other three methods, the proposed method has the least number of sensors when the mode vectors are linearly independent, and the proposed method can obtain the most modal information with the same number of sensors.

To study the dynamic response characteristics of submarine sedimentary layer under seismic action, this paper establishes a single-layer unsaturated porous medium seabed model, presents its governing equations, boundary conditions and wave field expressions, and obtains the analytical solutions for the steady-state responses of unsaturated seabeds under different bottom permeability conditions. Through numerical examples, the influences of different bottom permeability conditions, saturation degrees, permeability coefficients, incident wave frequencies and depths on the solid surface displacement amplification factor and pore water pressure are analyzed, and the following main conclusions are drawn: under low-frequency conditions, the influence of the saturation degree of the sedimentary layer on the displacement amplification factor and pore water pressure is relatively weak. While in the case of increasing frequency, the influence of the saturation degree on the displacement amplification factor and pore water pressure is significantly enhanced. Under low-frequency conditions, for the sedimentary layer with a permeable bottom, the displacement amplification factor and pore water pressure are relatively large. While under high-frequency conditions, for the sedimentary layer with an impermeable bottom, the displacement amplification factor and pore water pressure are relatively large.