Влияние демпфирования по Рэлею на устойчивость земляного полотна железной дороги в условиях сейсмического воздействия

This work aims to further promote the research and development of flexible damping technology for the seismic damage control of underground engineering structures. On the basis of the understanding of the application of viscoelastic damping theory to the field of earthquake resistance of bridge buildings, impact tests on different rock damping layer– concrete specimens are conducted using the improved split Hopkinson pressure bar test system to analyze the energy absorption characteristics of the viscoelastic damping layers. A comparative analysis of the test results is also performed to differentiate the laws of energy absorption of the viscoelastic damping layer structure using different damping layer materials (rubber and silicone) and different damping layer shapes (honeycomb, corrugated, and cylindrical). Given damping layers with the same material and structure, the energy absorption laws of the structures with different damping layer thicknesses are compared and analyzed. The optimal thickness of the damping layers is also discussed. Results show that the incident energy absorbed by the damping layers of different materials increases by more than 10% relative to the control group (rock–concrete specimen). Such an increase indicates that the structures have superior energy absorption characteristics and that the rubber material can absorb more incident energy than the high-damping silicone as the damping layer. As for the damping layer shapes, the composite damping layer structure with a honeycomb shape achieves the best energy absorption among all structures. The comparison and analysis of the energy absorption effects when the damping layer thicknesses are 10, 20, and 25 mm reveal that a 20 mm-thick damping layer shows the best energy absorption effect. The current findings can provide theoretical foundation and data support for the application of composite damping layers to the seismic design of underground engineering structures.

Evaluation of the long-term thermal stability of a crushed-rock revetment embankment in pan-Arctic permafrost regions under the effect of snow drift

In the Northern areas the total thickness of structural layers in railway embankments is primarily governed by the design against harmful effect of seasonal frost. Because practically no frost heave can be allowed to take place on railway tracks with normal speed passenger traffic, the embankment must typically be built up to two or even two and a half meters thick. Meantime, the embankments have typically fairly steep slopes, for instance in Finland track embankments are normally built using a slope ratio of 1:1.5. Introduction of higher allowable axle loads and traffic speeds is, however, exposing the embankments structures to continuously increasing intensity of repeated loading which is also increasing the rate of permanent deformations accumulating into the embankment structure. In practical terms the embankment is widening as it deforms and the respective movements of the track must be compensated by more frequent maintenance actions. The most straightforward measures to increase the internal stability of a railway embankment are to make the embankment wider and/or to reduce the slope steepness of the embankment. Both of these actions mean, however, larger space requirement for the railway track and, above all, extensive increase in the use of high-quality non-frost-susceptible aggregate materials in connection with the embankment construction or renovation. Therefore, taking into account both the construction time costs on one hand and the maintenance costs of the track on the other hand, optimisation of the embankment dimensions and shape is an important issue regarding the life cycle costs of a railway line. In a research project going on at the Laboratory of Earth and Foundation Structures of the Tampere University of Technology the above mentioned problem is being studied by in-situ monitoring of a full scale railway track embankment having sections that are shaped in different embankment widths and slope angles. The long term deformations of the embankment have been monitored for about three years in addition to which also the short term responses of the embankment structure have been measured while trains are passing over the monitoring sections. In addition, model scale (1:4) test structures with different embankment widths and slope angles have been tested in laboratory using a loading system consisting of five hydraulic actuators operating consecutively so as to simulate the loading effect of a moving train. The results obtained so far indicate clearly that it is not only the embankment width and slope angle that are decisive concerning the permanent deformation behaviour of the railway embankment, but also the subgrade stiffness plays an important role in the overall performance of the embankment structure.

Shear walls increase the horizontal stiffness of multi-story buildings in wind and earthquake conditions. According to TCVN 2737:2023, Etabs software must be used to study how shear wall thickness affects internal stresses and horizontal displacements in multi-story buildings. This study examines the impact of varying initial shear wall thicknesses, starting with bw=200mm and subsequently increasing to bw=250mm (25%), bw=300mm (50%), bw=350mm (75%), and bw=400mm (100%). The focus is on type I high-rise buildings (under 16 floors) and type II high-rise buildings (from 17 to 25 floors), specifically analyzing how these changes affect internal forces and horizontal displacements at the building's top. The survey results of the 9-storey building indicate a 6% reduction in bending moment, a 13% increase in shear force, and a 7% increase in axial force when the shear wall thickness is increased by 100% compared to the original thickness. For the 21-storey building, increasing the shear wall thickness by 100% leads to a 31% reduction in the bending moment, a 47% reduction in the shear force, and a 12% reduction in the axial force compared to the original thickness. As the height of the building rises from 9 to 21 floors, the horizontal displacement increases by a ratio of 6.4 times in both directions

Model test study on the anti-saline effect of the crushed-rock embankment with impermeable geotextile in frozen saline soil regions

This paper presents the study carried out to analyze the static and seismic behavior of the retaining wall and backfill soil. The lateral earth pressure on retaining wall plays an important role to ensure safety of such structure. The dynamic lateral earth pressure on retaining wall during earthquake condition is always greater than static lateral earth pressure and can induce large destabilizing force. Plaxis 2D software accomplishes the analysis of retaining wall in static and seismic conditions. The retaining wall with backfill material was analyzed with inclusion of compressive material EPS geofoam, which was placed at the interface of retaining wall and backfill material as an absorber to decrease lateral earth pressures on retaining wall. Parametric study of retaining wall has been done by changing various densities of EPS geofoam and thickness. This study shows that inclusion of EPS geofoam reduces the pressure on retaining wall in static as well as seismic condition.

The Palestinian Ministry of Health introduced an essential medicines list (EML) in 2000 to improve rational use of medicines and contain costs. We have examined the effects of the EML in the Palestinian healthcare public sector. We obtained data on prescription patterns for medicines from 3570 prescriptions given during outpatient visits in 17 healthcare facilities in the West Bank from 1997 to 2003. We analyzed the prescriptions to measure rational use. We modeled indicators of rational use as a function of the EML and 16 health center indicator variables. The EML was effective in shifting all prescribing indicators toward standard values. To improve rational medicine use, treatment protocols for the most common diseases and continuous education for medical staff is required.

Anomalous absorption of electromagnetic waves in a layered structure with complex permittivities

Tapered composite beams are widely used in various engineering applications, the dynamic analysis of this structure appear more and more important in its employment areas. The purpose of this paper is to carry on a research of dynamic characteristic of a steel beam with taped damping layer by Differential Transformation Method(DTM).Since parameters of material used in the damping layer depend on frequency, the method which compares the natural frequency of the composite beam with material frequency is added to research of the free vibration characteristics of this structure.A comparison on calculation cost time between ANSYS and DTM which are applied to analyze same structure demonstrates that DTM has the advantages of far less computation time than ANSYS.

The accelerator-driven subcritical system (ADS) can transmute nuclear waste by using high-energy neutrons, which is the most effective nuclear waste disposal scheme at present. The zero-power lead-bismuth alloy device accurately constructed the interaction mode between nuclear fuel and lead-bismuth alloy coolant material, and more accurately simulated the core physical characteristics of lead-bismuth reactor. Moreover, the inherent safety of the reactor is enhanced by installing several passive safety shutdown systems. However, due to the particularity of the potential harm caused by radioactive material leakage, nuclear-grade equipment should maintain high safety performance under many working conditions, such as earthquake working conditions. To ensure the safe operation of the ADS zero-power device and the safe shutdown under seismic conditions, the motion of the control rod of the ADS zero-power device must be analyzed under seismic conditions. At present, most studies on the control rod drop analysis focus on water reactor, but this paper will analyze and calculate the control rod drop of the lead reactor. In this paper, the physical mechanism of rod falling of the control rod component is analyzed, and the influence of contact collision between the control rod component and the guide tube of the control rod on the whole rod falling time is considered. In this paper, the finite element method is used for transient analysis of ADS lead-bismuth alloy zero power reactor, and the time history diagram of the control bar position is obtained under the seismic conditions, thus verifying that ADS lead-bismuth alloy zero power reactor can be safely shut down under the safe shutdown earthquake (SSE).

Changes in land use for the development of the Mandalika Special Economic Zone (SEZ) have led to increased flooding. A rainfall intensity of 35 mm recorded at the ARR KEK Mandalika station led to a flood event, with a water level reaching 1.2 meters on March 23, 2022. Therefore, a study is needed to determine the flood discharge that affects the Tabelo Watershed and to identify the appropriate structural mitigation measures for flood management. After conducting frequency analysis with Hydrognomon and Generalized Extreme Value (GEV), the flood discharge for the 50, 100, and 200-year return periods was 149.5 m3/s, 162.5 m3/s, and 175.2 m3/s. Structural mitigation by river normalization and levees construction on the Tabelo River was carried out along 1882.5 m at stationing P0 – P101 and 468.5 m at stationing S0 – S30. The levee construction is planned to be 14 m wide for the upstream section, up to the junction, and 16 m wide for the junction to the river mouth. The river levee is designed to be 3.30 meters high and 16 meters wide. The stability of the levee is calculated by considering its stability against overturning, sliding, and reactions from the foundation soil under both normal and seismic conditions. Based on the results of the stability calculations, the safety factor values for stability against shear forces under normal and earthquake conditions were obtained, namely, Fs (3.81 > 2.00) and Fs (1.27 > 1.25).

The functional layer of a flat‐tubular solid oxide fuel cell (SOFC) is examined using a three‐dimensional microscale electrode model. SOFC electrodes essentially include two types of layers: a structural layer and a functional layer. The structural layers, which are the anode support layer and the cathode current collector layer, are composed of large particles with a high porosity that facilitates gas diffusion. The functional layers consist of small particles with a low porosity that increases the triple phase boundary (TPB) reaction area and reduces the activation overpotential. In the model, the particle diameter and functional layer thickness are adjusted and analyzed. The effects of the two parameters on the performance of the functional layer are monitored in the contexts of several multilateral approaches. Most reactions occurred near the electrode–electrolyte interface; however, an electrode design that included additional TPB areas improved the electrode performance. The role of the functional layer in a flat‐tubular SOFC is examined as a function of the functional layer particle size and thickness. The performance of a cell could be enhanced by preparing a functional layer using particles of optimal size and thickness, and by operating the device under conditions optimized for these parameters.

Generic differential equations of motion for a three-layer sandwich shell with viscoelastic core are derived. The Hamilton’s principle and Donnell-Mushtari-Vlasov simplification are employed in the derivation. The differential equations, unlike the existing models with five displacements, contain only three displacements, that are one transverse displacement and two in-plane displacements of the host structure. The proposed theory is generic and can be specialized to account for many other commonly occurring geometry, such as spheres, cylinders, plates, cones, ..., etc. The theory can be directly applied to the studies of shells / plates with constrained damping (CLD) layer. The theory can also be degenerated into one single layer or two-layer structures. Specialization of the generic theory to cylindrical shell is focused and an example is demonstrated in this paper. The results of one single layer shell agreed well with the classical shell theory. Two-layer shell models proved to be accurate and can be used for the studies of active vibration control and smart material developments.

Application of the extreme gradient boosting method to quantitatively analyze the mechanism of radon anomalous change in Banglazhang hot spring before the Lijiang Mw 7.0 earthquake

In recent years, earthquake rockfalls have occurred frequently all over the world, resulting in heavy casualties and property losses. Unfortunately, research on rockfall dynamics upon earthquake events is still rare due to limited field and experimental data, and restricted to numerical simulations of only two dimensions. In order to primarily reveal the role of earthquakes on rockfall, this study focused on the stability of rock blocks on an inclined slope, and following rockfall dynamics by three-dimensional discontinuous deformation analysis (3-D DDA). First, earthquake input methods were discussed and implemented for the triangulated regular network (TRN) in 3-D DDA. The effectiveness was verified by comparison with analytical solution results of a single block on the inclined slope under seismic loads. Further, by discussing the variations of the boundary chart of failure modes, it indicated that the block was more prone to slide even with a large friction angle, became instability under seismic conditions. Moreover, a regular dodecahedron rock block was released on a stochastic roughness slope with two platforms through parallel realizations. The indices of the movement characteristics of the block, such as runout distance, lateral displacement range, and resting position, were investigated. The results showed that the maximum runout distance was not sensitive to seismic load, but the lateral displacement range was significantly sensitive to seismic load and increased appreciably. Through the 3D-DDA numerical simulations, both rock stability and rockfall behaviors under earthquake conditions could be better understood. Furthermore, it will be helpful to by analyzing trajectories and kinetic energies predict earthquake rockfall disasters and design reasonable protective countermeasures under earthquake scenarios.