Dynamic Model Tests Research Articles

Analysis of the Effect of Quay Container Crane Available on Dwelling Time at Jakarta International Container Terminal

The efficiency of loading and unloading dwelling time at the port has been done a lot. The problem at PT JICT is that there has been a decrease in throughput for the last three years, this has an effect on operational performance. operational performance is a representation of the achievement of all targets, thus the company always aims to improve its operational performance. Another problem is that the terminal's operational equipment has begun to be obsolete, which hinders the loading and unloading operation time, the lack of operational equipment that supports the loading and unloading process. The operational equipment studied is the Quay Container Crane which is seen from the available condition. All of these problems will have an impact on dwelling time at PT JICT which can affect operational performance. This research is expected to provide recommendations to PT Jakarta International Container Terminal to prepare adequate operational equipment so that the resulting dwelling time is known. This research method uses a dynamic system model and validation test with behavior pattern test. The results of the dynamic system model validation obtained dwelling time between 2.79 - 4.56 days, mean error of 3% and standard deviation error of 11%. Maintenance of quay container cranes has an influence on unloading productivity which has an impact on dwelling time. Based on 60 data, the quay container crane available variable is seen based on quartile values consisting of quartile 1 (Q1), quartile 2 (Q2) and quartile 3 (Q3). In the quay container crane available variable, the dwelling time value in quartile one is 1.34 days, quartile two is 1.47 and quartile three is 1.51 and the dwelling time value in quartile one is 14 units, quartile two is 12 units and quartile three is 10 units.

Experimental study on deformation characteristics of new prestressed subgrade under static and dynamic loads

An in-deep comprehension of the static and dynamic operational characteristics of prestressed subgrade is essential for its analysis, design, and service performance evaluation. Based on the Buckingham π theory, a novel scaled static and dynamic model test system of the prestressed subgrade has been developed. The structural components, functional characteristics, and working mechanism of the test system were comprehensively elucidated, and a suite of static and dynamic model tests was conducted to study the deformation characteristics of the prestressed subgrade. It is demonstrated that the prestressed steel bars underwent prestress loss due to the additional stress induced creep of the soil elements below and adjacent to the load transfer plates (LTPs). Therefore, it is advisable to over-tension the prestressed steel bars in practical engineering. Upon the application of prestress, the subgrade surface experienced slight uplift deformation, which did not change the geometric shape and smoothness of the subgrade surface and demonstrated that the prestress reinforcement effect could diffuse to the subgrade surface. In the static double-load-plates tests, the prestressed subgrade presented obvious advantages in controlling the subgrade surface settlement and slope lateral deformation compared to the unreinforced subgrade, which could therefore improve the deformation resistance of the subgrade. In the short-term dynamic loading tests, both the acceleration and dynamic displacement of the subgrade approximately linearly decreased with an increase in the prestress, implying that the horizontal prestress had a notable beneficial impact on mitigating the subgrade vibration. Additionally, with the long-term dynamic loading, the prestress reinforcements could significantly restrain the cumulative plastic deformation of the subgrade, with the cumulative deformation decreasing as the applied prestress increased. The developed test system offers viable and implementable technical means for investigating the enhancement mechanism of a prestress reinforced subgrade, and the insights gained from the tests contribute to elucidating the effect of prestress reinforcements on the subgrade’s static and dynamic performance.

Validation of a scaled dynamic test system for simulating a high‐speed train passing bridges under seismic excitation

AbstractThis study presents the validation of a dynamic test system to simulate a high‐speed train passing bridges under seismic excitation. The system comprises scaled models of a CRH380A high‐speed train and an 11‐span simply supported bridge on a shake table array. This innovative apparatus combines seismic loading with the moving train load to replicate train‐track‐bridge interaction (TTBI) during earthquakes. It allows investigation of various train speeds and seismic excitations, providing invaluable insights into TTBI. First, the detailed similarity design principle based on the equations of motion was discussed, and its applicability to the wheel‐rail contact relationship was verified. Then, the dynamic characteristics of the scaled model were identified, and the impact of the error between the scaled model and the theoretical model on the TTBI response was assessed. Furthermore, the comparison of the dynamic test model and the numerical simulation in acceleration responses validated the accuracy of the rigid‐flexible coupling model method for the actual TTBI system. Test cases without external excitation, with simple harmonic excitation and with seismic excitation were conducted on the dynamic test system. Results showed that the influence of track irregularity and running speed on train response aligns with the classical train‐bridge interaction theory. The successful implementation of this test system marks a significant advance in understanding TTBI mechanics and has significant implications for seismic safety enhancement of railway infrastructure.

Nonlinear spatiotemporal characteristics of wind–rain flow around the trains passing through the tunnel entrance during rainstorms

Tropical storms present a significant risk to the safety of high-speed trains due to the extreme wind and rainfall they bring. This study employs Eulerian multiphase and Shear-Stress Transport k-ω turbulence models for three-dimensional numerical simulations, focusing on wind–rain interactions involving tunnels, embankments, and trains. The reliability of the numerical analysis method for train slipstream pressure is verified by dynamic model test. Based on the scenario of single train running on the embankment and train intersection at the tunnel portal, the train flow around and wake are analyzed successively with different rainfall intensity. The characteristics of nonlinear wind–rain-train flow field are analyzed from the aspects of velocity field, pressure field and turbulent flow. Finally, the mechanism of the influence of rain on the relative flow field is revealed by the spatiotemporal distribution characteristics of rain phase. With the increase of rainfall intensity, the increase of rain phase distribution on the leeward side of the single train strengthened the backflow on the leeward side of the train. Under the condition of the trains intersecting at the tunnel portal, the relatively closed area between the train and the water film weakened the slipstream effect of the train.

Transforming capital: The role of human capital structure in modulating environmental outcomes across economic transitions

Based on the perspective of new structural economics, this study builds a theoretical framework of human capital structure and environmental pollution. Human capital structure on pollution has different manifestations at different stages of development, the effect of pollution based on human capital structure follows the environmental Kuznets curve. Using multinational panel data (1990–2015) and provincial panel data for China (2004–2020), examined the dynamic relationship between human capital structure upgrading and pollution by introducing an interaction term between human capital and economic development level, applying random-effect, fixed-effect models, and a dynamic model test. The results support our theoretical analysis.

Liquefaction characteristics of aging earth dam body by dynamic centrifugal model test

Earth dams have been damaged or even collapsed owing to earthquake liquefaction. Although a liquefied foundation is a major factor affecting the safety of earth dams, the damage caused by the liquefaction of the dam body itself cannot be ignored, particularly for aged earth dams. However, in the presence of high water levels, liquefaction of the dam body cannot be considered solely in terms of the seismic load. Consequently, in this study we used dynamic centrifuge tests and numerical analysis to simulate the liquefaction process of an earth dam body under high water levels and analyzed the damage mechanism. The aging dam body, which can be easily liquefied, was simulated by controlling the density of the dam body, the low-density dam body exhibiting greater acceleration-amplification characteristics and displacement. Liquefaction was evident in the contact area between the slope and water level, with segmental settlement occurring. Through numerical analysis, it was evident that the core area accumulated considerable plastic deformation, and the sliding damage extended from the water contact surface to the dam toe. This study could compensate for the dearth of liquefaction model experiments of earth dams, providing a necessary reference for the seismic reinforcement of earth dams.

A Study on Seismic Dynamic Response of Pile-Supported Tunnels in Deep Backfill Area of Soil–Rock Mixture Based on a Model Test

Aiming to address the problem of construction and environmental risks in tunnel construction through the soil–rock mixture backfill area, this paper carried out a seismic dynamic response model test of a pile-supported tunnel based on practical projects. Firstly, the stress–strain curves and failure characteristics of the soil–rock mixture in the study area were obtained through triaxial tests, and based on this, similar materials for the model test were developed. Then, a vibration table model test was devised to investigate the seismic dynamic response of the pile–tunnel structure. The findings revealed the following: when subjected to seismic waves, the soil–rock mixture stratum displayed a “skin effect” in its acceleration response, indicating that closer proximity to the surface led to heightened horizontal acceleration responses; the horizontal peak acceleration of the grouting mixture stratum in the vertical direction exhibited a “Zigzag” pattern; the peak values of strain response and bending moment in the tunnel lining cross-section exhibited an “X” shape and inverted “V” shape, respectively. The bending moment at the pile crown increased alongside the peak value of the input seismic wave acceleration. The maximum surface settlement in the model ranged from 0.5 to 1 cm, with the tunnel–pile structure effectively mitigating surface settlement.

Dynamic impact of unsupported sleepers on railway infrastructure with a coupled MBD-DEM-FDM model

This paper introduced a numerical simulation model of vehicle-track-substructure system, which combines the multi-body dynamics method (MBD), the discrete element method (DEM) and the finite difference method (FDM). In this model, rail, fastener, sleeper and ballast particles were built based on the DEM by using Particle Flow Code (PFC) software, substructure (including subgrade and foundation) was built based on the FDM by using Fast Lagrangian Analysis of Continuum (FLAC) software, and the vehicle was built based on the MBD by self-programming. Here, two-way coupling calculation is implemented to satisfy the force equilibrium and displacement compatibility between railway components established by different method. And then, this coupled MBD-DEM-FDM model was validated by comparing the results with those from the classical vehicle-track dynamic model (VTCD model) and field test results. Afterward, the influence of unsupported sleepers on meso and macro dynamic behaviour of railway infrastructure was investigated. The coupled MBD-DEM-FDM model possesses the capability to accurately simulate the interaction between trains and tracks, analyze the meso mechanical responses of railway infrastructure, and capture significant subgrade deformations. Consequently, the proposed model offers a comprehensive understanding of the deterioration processes within railway infrastructure.

Cyclic Fatigue of Different Reciprocating Endodontic Instruments Using Matching Artificial Root Canals at Body Temperature In Vitro.

Reciprocating motion expands the lifetime of endodontic instruments during the preparation of severely curved root canals. This study aimed to investigate the time to fracture (TTF) and number of cycles to failure (NCF) of different reciprocating instruments (n = 20 in each group) at body temperature using a dynamic testing model (amplitude = 3 mm). Reciproc Blue (RPB), size 25/.08, WaveOne Gold (WOG) 25/.07, Procodile (Proc) 25/.06, R-Motion (RM_06) 25/.06 and R-Motion (RM_04) 30/.04 instruments were tested in their specific reciprocating motion in artificial matching root canals (size of the instrument ± 0.02 mm; angle of curvature 60°, radius 5.0 mm, and centre of curvature 5.0 mm from apical endpoint). The number of fractured instruments, TTF, NCF, the and lengths of the fractured instruments were recorded and statistically analysed using the Chi-Square or Kruskal-Wallis test. Both TTF (median 720, 643, 562, 406, 254 s) and the NCF (3600, 3215, 2810, 2032, 1482 cycles) decreased in the following order RM_06 > RPB > RM_04 > Proc > WOG with partially significant differences. During testing, only six RM_06 instruments fractured, whereas 16/20 (RPB), 18/20 (Proc), and 20/20 (RM_04, WOG) fractures were recorded (p < 0.05). Within the limitations of the present study, blue-coloured RPB and RM instruments exhibited a significantly superior cyclic fatigue resistance compared to SE-NiTi and Gold-wire instruments. Heat treatment, cross-sectional design and core mass significantly influenced the longevity of reciprocating instruments in cyclic dynamic testing.

Seismic Safety Analysis of Interlaminar Rock Mass in the Distributed Underground Reservoir of a Coal Mine

This study focuses on the seismic safety of distributed underground reservoirs in coal mines, especially in scenarios involving the establishment of multiple reservoirs within the same mining area, spanning different coal seams. Dynamic similarity model tests and numerical simulations are employed to investigate the construction and operation of these reservoirs under extreme conditions, such as mine tremors or earthquakes. Utilizing the Daliuta coal mine underground reservoir as a case study, a similarity material model test platform is established to represent both upper and lower coal mine underground reservoirs. Stability tests are conducted on the interlayer rock mass under various levels of seismic intensity, and the safety of the interlayer rock mass at different safety distances is comparatively analyzed. Meanwhile, using the finite element method, the responses of the upper and lower coal mine underground reservoirs under different seismic intensity levels are simulated with the same conditions of model tests. Through the two types of simulations, the mechanical response and safety of the surrounding rock of the Daliuta coal mine underground reservoir under the influence of different seismic intensities are systematically analyzed, and the reasonable safety distances between the upper and lower reservoirs are obtained. This study provides a valuable scientific insight into the safe design of underground reservoir embankments in coal mines.

How do R&D capital market distortions affect innovation efficiency in China? Some evidence about spatial interaction and spillover effects

Improving innovation efficiency (IE) and refining capital market distortions are important considerations for promoting national innovation strategies. This study uses the dynamic spatial Durbin model and mechanism tests to explore the direct impacts, spatial effects, and influencing mechanisms of R&D capital market distortions on IE based on Chinese provincial panel data from 2009 to 2019. The main results can be summarized as follows. First, China’s IE is characterized by temporal inertia and spatial agglomeration. In both the spatial and temporal dimensions, IE in neighboring areas in the previous period can inhibit local IE in the current period. Second, R&D capital market distortions have a weakening effect on IE in the short- and long-term. Third, R&D capital market distortions have significant spatial interaction and persistent positive spatial spillover effects on IE. Finally, R&D capital mismatch and technology lock-in effects are essential mechanisms related to R&D capital market distortions that can inhibit IE. Based on these results, policy recommendations have been proposed to improve IE.

Experimental study of structural vibration control of 10-MW jacket offshore wind turbines using tuned mass damper under wind and wave loads

As slender structures, offshore wind turbines (OWTs) are prone to vibration and deformation under wind and waves. Tuned mass dampers (TMDs) have become among the most promising vibration-mitigation methods owing to their simplicity and practicability. To study the vibration control effect of a TMD on a jacket OWT under wind and wave conditions, we conducted a fully coupled dynamic model test of a 1/75 scale jacket OWT with and without a TMD. The physical model of the jacket OWT included scaled rotor-nacelle assembly (RNA) and support structure models. For the scaled RNA model, a redesigned blade model was used to ensure similarity of the aerodynamic thrust loads without modifying the scaled test winds. Drivetrain and pitch-control system models were designed to simulate the operating state of an actual OWT. The support structure model was established based on the hydro-structural elastic similarity. Furthermore, a TMD model was designed and manufactured based on the first mode of the scaled OWT. A fully coupled dynamic model test of a 10 MW jacket OWT with a TMD under wind and wave conditions was performed, and the vibration-mitigation performance of the designed TMD model on the structural responses of the scaled OWT model was evaluated.

Study on vibration characteristics of fine breccia soil subgrade reinforced with a new prestressed structure under train cyclic loading

Train cyclic loading generally results in significant dynamic responses of the breccia soil subgrade, resulting in a series of subgrade problems. A new prestressed reinforcement structure (PRS) is proposed to reinforce subgrade structures. However, characteristics of the prestressed subgrade under dynamic loading have not been investigated. This study investigates the vibration characteristics of a new prestressed subgrade structure under train cyclic loading. The acceleration responses of the subgrade surface under different train axle loads and prestress levels are measured and discussed by developing a 1:5 scale dynamic model test on a prestressed fine breccia soil subgrade structure. Subsequently, a three-dimensional dynamic finite element model of the prestressed subgrade is constructed for an in-depth analysis of the internal acceleration of the prestressed subgrade. The results showed that a periodic acceleration response of the subgrade should be observed, and its mean crest and mean trough are used to characterize the long-term vibration degree of the subgrade. The peak vertical acceleration of the subgrade is significantly affected by the prestress level, and the dynamic response of the subgrade around the lateral pressure plate (LPP) is reduced more obviously by the prestress than that of the subgrade’s inner region. The peak vertical acceleration at the subgrade shoulder presents linear increase and exponential attenuation with the rise in the train axle load and prestress level, respectively. In addition, an empirical model describing the relationships among the peak acceleration, train axle load, and prestress is proposed. The vertical dynamic displacement and dynamic stress decrease with the increase of the prestress. The average elastic deformation and peak dynamic stress of the subgrade under a prestress level of 100 kPa are found to be 95.8% and 87.22–90.07% of that with the absence of prestress, respectively. The vertical vibration of the prestressed subgrade structure can be reduced by taking measures such as adjusting the prestress magnitude and increasing the subgrade slope ratio, thereby achieving an effective prestress reinforcement effect.

Evaluation of the dynamic behavior of pile groups considering the kinematic force of the slope using centrifuge model tests

In this study, dynamic centrifugal model tests were performed by installing a pile group on the slope to examine the effect of the kinematic force of the slope on the pile. Based on the results of this experiment, a method for calculating the slope kinematic force applicable to the pile foundation was derived, and the pseudo-static analysis was performed. The results showed that the moment difference from the experiment occurred at the top of the pile by 14-49% in the analysis model without ground kinematic force, but decreased to 3-35% when the ground kinematic force was considered. In particular, in the lead pile, which is most affected by the ground kinematic force, the moment difference was less than 20% when the ground kinematic force was considered, indicating that the pile moment by depth was most appropriately simulated.

Numerical Evaluation of Dynamic Earth Lateral Pressure on Basement Walls in Cohesionless Soils (A Case Study of Iranian Earthquakes)

Various earth-retaining structures are extensively used in different civil engineering projects. Using the results of experimental and numerical modeling, the effect of the earthquake loading on the distribution of the earth lateral pressures on basement walls was investigated. The UBCHYST constitutive model was used in the performed numerical simulations, and using the results of 12 centrifuge dynamic model tests, a calibration process was conducted to obtain the proper input parameters for numerical models. Based on the results, some correlations between the dynamic increment coefficient of earth lateral pressure (ΔKae) and the free-field peak ground acceleration (PGAff) were established. The correlations are different for stiff and flexible basement walls. In the end, the results of the model calibration process were verified by the examination of 12 major earthquakes that occurred in the Iran plateau. The results showed that the proposed ΔKae-PGAff correlations are precise enough for the applied design projects.

합성곱 신경망과 복셀화를 활용한 선박 저항 성능 예측

The prediction of ship resistance performance is typically obtained by Computational Fluid Dynamics (CFD) simulations or model tests in towing tank. However, these methods are both costly and time-consuming, so hull-form designers use statistical methods for a quick feed-back during the early design stage. It is well known that results from statistical methods are often less accurate compared to those from CFD simulations or model tests. To overcome this problem, this study suggests a new approach using a Convolution Neural Network (CNN) with voxelized hull-form data. By converting the original Computer Aided Design (CAD) data into three dimensional voxels, the CNN is able to abstract the hull-form data, focusing only on important features. For the verification, suggested method in this study was compared to a parametric method that uses hull parameters such as length overall and block coefficient as inputs. The results showed that the use of voxelized data significantly improves resistance performance prediction accuracy, compared to the parametric approach.

Magnetorheological semi-active shock mitigation control. Part I: numerical analysis and preliminary tests

Minimizing shock loads transmitted to sensitive structures or equipment is the objective of shock mitigation control. The core of shock mitigation control using magnetorheological (MR) energy absorber (EA) to minimize impact load is to make full use of the piston stroke of MREA so as to achieve “soft-landing.” The key lies in the precise description of the hysteresis of MREA and the shock mitigation control method. In this part, a single-degree-of-freedom (SDOF) shock mitigation control system using MREA is established, and the corresponding dynamic model and drop-induced shock mitigation test system are established. Based on the optimal Bi number control method and constant force control theory, feedforward controllers featuring resistor-capacitor (RC) operator-based hysteresis model and Bingham model are established to realize “soft-landing” in sequence. Specific performance evaluation indexes for shock mitigation control systems, that is, average velocity change rate (AVCR) and velocity-acceleration conversion ratio (V-ACR), are proposed. The effectiveness of shock mitigation control methods with different models on the MREA-based shock mitigation control system in profiles of simulation and tests are compared and analyzed.

Mitigation Effect of Helmholtz Resonator on the Micro-Pressure Wave Amplitude of a 600-km/h Maglev Train Tunnel

A 600-km/h maglev train can effectively close the speed gap between civil aviation and rail-based trains, thereby alleviating the conflict between the existing demand and actual capacity. However, the hazards caused by the micro-pressure wave amplitude of the tunnel that occurs when the train is running at higher speeds are also unacceptable. At this stage, mitigation measures to control the amplitude of micro-pressure waves generated by maglev trains at 600 km/h within reasonable limits are urgent to develop new mitigation measures. In this study, a three-dimensional, compressible, unsteady SST K–ω equation turbulence model, and an overlapping grid technique were used to investigate the mechanism and mitigation effect of Helmholtz resonators with different arrangement schemes on the micro-pressure wave amplitude at a tunnel exit in conjunction with a 600-km/h maglev train dynamic model test. The results of the study showed that a pressure wave forms when the train enters the tunnel and passes through the Helmholtz resonator. This in turn leads to resonance of air column at its neck, which causes pressure wave energy dissipation as the incident wave frequency is in the resonator band. This suppresses the rise of the initial compressional wave gradient, resulting in an effective reduction in the micro-pressure wave amplitude at the tunnel exit. Compared to conventional tunnels, the Helmholtz resonator scheme with a 94-cavity new tunnel resulted in a 31.87% reduction in the micro-pressure wave amplitude at 20 m from the tunnel exit but a 16.69% increase in the maximum pressure at the tunnel wall. After the Helmholtz resonators were arranged according to the 72-cavity optimization scheme, the maximum pressure at the tunnel wall decreased by 10.57% when compared with that before optimization. However, the micro-pressure wave mitigation effect at 20 m from the tunnel exit did not significantly differ from that before the optimization.

Parameters of dynamic compaction based on model test

Several large–scale outdoor dynamic compaction model tests with energy levels, drop distances, masses and diameters of falling weight as variables, and different types of acceleration sensors are respectively designed in this paper to monitor inside soil mass, ground surface and falling weights dynamically. The following results are presented: the soil damping ratio changes with the increase of tamping times; at the same energy level, the horizontal reinforcement effect of a heavy falling weight on shallow and deep soil is better than a light falling weight and the ground surface vibration caused by heavy falling weight is small; the combination of tamping impulse and falling weight diameter is appropriate as the control standard of final cumulative settlement; the construction and detection of dynamic compaction can be assisted by the statistical relationship between the tamping impulse I, the impact time T and the single tamping settlement y. The results of this study are instructive for improving the construction quality of dynamic compaction.

Experimental Study on the Dynamic Characteristics of a New Long-Short Pile Composite Foundation under Long-Term Train Load

Long-short pile composite foundation (PC-LSPCF) composed of part-screw pile and cement-soil compaction pile is a new railway foundation treatment method, which has been widely used in high-speed railway construction projects in China. To explore the dynamic characteristics and deformation characteristics of railway PC-LSPCF under long-term train loads, the dynamic characteristics of long piles, short piles, and soil between piles under long-term train loads are tested by an indoor dynamic model test. The dynamic amplification of pile and soil under dynamic load and the temporal and spatial distribution of peak response are analyzed, and the stress and deformation development mechanism of PC-LSPCF under cyclic loading of large-cycle trains is revealed. The results show that the neutral point of the long pile is at 1/2 of the pile length and that of the short pile is at 3/8 of the pile length. The part-screw pile has a certain absorption effect on vibration energy. The deformation of a long-short pile composite foundation under long-term train loads can be divided into three stages: extreme growth, transition, and stability. The train speed is negatively correlated with the cumulative settlement of the long-short pile composite foundation. The higher the train speed, the smaller the cumulative settlement, and the smaller the number of cycles of the N-S curve entering the gentle period. As the number of train cyclic loads increases, the load-sharing relationship of the long pile-short pile-soil system will be redistributed. The research results have important reference significance for the optimization design of high-speed railway foundation treatment.