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 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.

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 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.