Based on the database of the Pacific Earthquake Engineering Research Center, the collected seismic records were classified according to the fault distance of the seismic stations, and the amplitude, spectrum and time characteristics of the ground motions under different site conditions were studied and quantitatively analyzed. Taking the Huangdeng gravity dam as the research object, based on the three response quantities of downstream displacement at the upstream dam face, principal tensile stress at the upstream dam face and principal compressive stress at the downstream dam face, the influence of near-fault earthquake pulse characteristics on seismic response of gravity dams was investigated. The results show that the relative displacement of the toe of the top dam of Huangdeng gravity dam under pulse earthquake is 44% larger than that under non-pulse earthquake. The principal tensile stress at the dam heel is 30% larger than that of the non-pulse type. The principal compressive stress at the toe of the dam is 31% greater than the response value of non-pulsed earthquake. The impact of pulse earthquakes on the structure is not negligible compared with non-pulsed earthquakes, and the response values of the structure were significantly larger. Therefore, it is necessary to consider the impulsive action of near-fault earthquakes in seismic fortification.

The fixed connection between the piers and the superstructure of rigid-frame bridges with high piers exhibits limitations in seismic design. Cracking of the cross-section and prestressing tendon stress loss can be found in the main girder subjected to seismic loads. The inertialr system ( i. e. tuned mass-damper-inerter, TMDI) contains an inertial container and a traditional tuned mass damper (TMD). It is a new method for structural seismic control in recent years. This study focuses a high-pier, long-span continuous rigid-frame bridge, considering the construction process and combining Midas Civil and the OpenSees to establish a nonlinear seismic response numerical model. Using 10 near-fault pulse-like ground motion records as input, this study investigates the seismic control behavior of a distributed configuration of multiple TMDIs. The results show that when the ground motion excites the bridge along the longitudinal direction, TMDIs can effectively prevent the cracking of the top and bottom slabs of the main girder, although the internal forces of the web of the main girder increase slightly. When the ground motion excites the bridge along the transverse direction, TMDIs significantly reduce the internal forces on the web of the main span. When ground motions are input in both horizontal directions, TMDIs can effectively mitigate the stress on the top slab, bottom slab, and web of the main span. Regarding the pier response, the average seismic reduction proportions of the maximum displacement at the pier top are 52% in the longitudinal direction and 21% in the transverse direction, respectively. The seismic reduction proportions of the maximum bending moment in the longitudinal direction is 31%. Although TMDIs increase the bottom bending moment of the pier by approximately 10% in the transverse direction, they effectively control the residual displacement of the bridge pier.

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 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.

On January 7, 2025, an earthquake of magnitude M_S6.8 struck Dingri County, Xizang Autonomous Region. In this paper, the near-field seismic wave field and instrumental intensity field were simulated using the strong ground motion simulation and prediction cloud platform of the Institute of Engineering Mechanics, China Earthquake Administration (CEA), combined with the kinematic seismic source model, the regional public velocity model and the digital elevation model. The simulated and measured instrumental seismic intensities are comparable at the stations of the National Seismic Intensity Rapid Reporting and Early Warning Project. The simulated high intensity zones are mainly distributed around the place of the surface projection fault, and the simulated instrumental seismic intensity field is basically the same as the survey seismic intensity field. On the basis, the earthquake damage to typical buildings (mainly earth/stone and wood structures) and casualties was evaluated and the evaluation results were also comparable to the actual data.

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%.

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 demountable reinforced concrete column-steel beam (RCS) combined frame consists of reinforced concrete columns, steel beams and demountable connectors. The beam-column joints are connected by bolted shear-resistant connectors, which can realize the disassembly of components for recycling and ensure the effective transfer of forces. However, the seismic performance of demountable RCS frame structure is still unclear, and there is an urgent need to conduct out research on the seismic performance of demountable RCS frame structure. To this end, for the proposed static test of non-demountable conventional RCS frame structure carried out by the team in the early stage, this paper adopts the finite element software ABAQUS to establish a finite element model, and compares the finite element calculation results with the test results through the damage modes, hysteresis curves, skeleton curves, and the cumulative energy dissipation, etc., to effectively verify the accuracy of the numerical simulation. With the help of the same finite element analysis method, a finite element model of the RCS frame with the new demountable connection was established, and the seismic performance of the RCS frame specimens under different node connections was studied in depth, including the force transfer paths, stress maps, hysteresis curves, skeleton curves, stiffness degradation, ductility, and energy dissipation, etc., and the feasibility of realizing the demountability of the frame structure is also analyzed. The results show that: the new demountable joints connection can control the plastic hinge in the region of the distal beam section, effectively protect the joints core area, and improve the ultimate load carrying capacity and stiffness. The hysteresis curve is fuller, slowing down the degradation rate of the load carrying capacity and stiffness, and greatly improving the frame's energy consumption capacity. The specimens with the new demountable joints connection can effectively ensure the continuity of the force transmission path, and its seismic performance indexes are significantly better than the traditional RCS frame structure. The research results and conclusions of this paper can provide a powerful design reference and data support for the seismic design of demountable RCS frame structures.

The failure of porcelain cylindrical electrical equipment during earthquakes is a key factor contributing to power supply outages. The meticulous assessment of the seismic resistance of these devices is a foundational requirement for accurately gauging the overall seismic robustness of power systems. The judicious choice of the support dynamic magnification coefficient plays a crucial role in precisely appraising the seismic behavior of porcelain cylindrical electrical equipment. In this research, to derive the support dynamic magnification coefficients for these devices, vibration tests were carried out on three main types of porcelain cylindrical electrical installations: in cluding disconnect switches, voltage transformers, and current transformers, all of which were evaluated as integrated units with their respective support structures under various seismic excitations and different peak ground acceleration levels. Based on these empirical results, finite element analysis was used to examine the effect of parameters such as the stiffness of supports on the natural frequencies of the equipment-to-support system configurations. This analysis also included a discussion on how the support dynamic magnification coefficients vary with different periodic characteristics of the equipment-support assembly systems. The study findings indicate that, within the scope of this study, the support dynamic magnification coefficient tends to increase as the combined or overall period of the equipment-support system increases. Notably, when the total system period exceeds T_g, the seismic response of the system remains at a relatively high level, significantly exceeding the reference values set by design spectra and clearly surpassing the conservative 1.2 limit established by present guidelines, thus implying a potential underestimate of safety margins. Therefore, it is proposed that the support dynamic magnification coefficient for porcelain cylindrical electrical equipment should optimally not be less than 2.0, and concurrently, the frequency of the supports should not be belower than 30 Hz to ensure enhanced seismic safety measures.