This study investigated the impact of axial load on the dynamic response of reinforced concrete (RC) members to asymmetrical lateral impact loads. A series of asymmetrical-span impact tests were conducted on circular and square RC members with and without Carbon Fiber Reinforced Polymers (CFRP) while varying the axial compression ratios. The impact process was simulated using ABAQUS software, and the time history curves of deflection and impact were measured. The study found that specific impact loads caused bending and shearing failures. The axial compression ratio ranged from 0.05 to 0.13 when the impact curve reached its maximum deflection before the component's impact resistance decreased. Analysis of the impact point and inclined crack location revealed that axial load affects the maximum local concrete. The speed of inclined crack penetration and inclined cracks take longer to form, with weaker resistance to damage to local concrete when the axial compression ratio is between 0.05 and 0.13. When the axial compression ratio is greater than 0.13, inclined cracks form sooner with more brittle and severe damage to the impact point's concrete. The study also identified key parameters affecting the dynamic response of RC members, including impact height, CFRP layer thickness, axial force, and impact location. Thicker CFRP layers in RC can improve impact resistance, especially when the impact location is farther from the center. However, there is a limit to the impact of axial force on this resistance.

This paper aims to validate circular reinforcement concrete (RC) members' responses to the effect of an asymmetrical lateral impact span train collision. It was determined that the RC members' failure mechanism and dynamic response characteristics were important. Numerical analyses were conducted on four specimens. The specimen's crack development pattern, failure mode, impact force, and deflection time history curves are verified. Due to the difference in impact velocity, longitudinal reinforcement, and stirrups ratios, shear cracks indicate two types. A finite element (FE) modeling method has been proposed and successfully demonstrated. Using the control variables to study the failure process and mode, which were affected by reinforcement ratio, impact velocity, and slenderness ratio, by analyzing impact response characteristics. It is found that parameters greatly influence shear cracks' type and development range. Simultaneously, the changes in impact velocity and slenderness ratio affect the failure mode of the members. RC members' mechanical properties and failure mechanisms are studied using test and FE analysis. Members' failure modes, bending moment distribution and development, shear forces, reinforcement strain, and energy consumption are also investigated. The development of type I and type II shear cracks is discussed. A method to determine the shear cracks was proposed through regression analysis by supplementing other scholars' test data and combining it with the study test data.

This paper investigates the responses of circular CFRP-RC components when subjected to an asymmetrical impact force. The impact performance of CFRP-RC components was investigated using drop-hammer impact test equipment. The failure mechanism and dynamic response properties of the CFRP-RC components were considered critical to obtaining. Three specimens were used in the experiments. The specimen's crack propagation pattern, failure mechanism, impact force, and deflection time history curves are all obtained. The test results indicate that shear fractures occur between the impact point and the adjacent support. The failure mode of reinforced concrete components transforms from bending to shear related to the unequal span impact load. A finite element modeling method was proposed and demonstrated efficiently. The control variables were used to analyze the failure mode and mechanism. Once the impact velocity or the number of CFRP layers decreases, the component fails in shear rather than bending. During an impact load, the internal force distribution of components differs significantly from that of a static load. The mechanical properties and failure mechanisms of CFRP-RC components are investigated using test and FE analysis. The failure modes of the components and the distribution and development of bending moments, shear forces, reinforcing strain, and energy consumption are all investigated.

The dynamic response of Reinforced Concrete (RC) and Carbon Fiber Reinforced Polymers with Reinforced Concrete (CFRPRC) is studied. These tests were performed on RC members covered in one to six layers of CFRP. Once the energy is high, the two components' deflection-time histories are produced. It increases component impact resistance in studies. Component deflection is reduced by carbon fiber reinforced polymer (CFRP). RC members shear while CFRPRC components bend due to significant concrete damage. It fractures more easily when wrapped with CFRP. The model's predictions match the tests adequately. A numerical simulation study looked at the impact force of members under unequal-span lateral collisions. Regardless of impact velocity, lateral impact on an unequal span induces severe shear failure of RC members. However, CFRPRC component bending deformation reflects impact velocity. Increasing the reinforcement ratio of RC members has little effect on the impact resistance of CFRPRC components. To avoid steel fracture, greater reinforcing ratios are used.

With the fast growth of high-speed rail in recent years, derailment has become the first hidden danger of high-speed rail transportation. The high-speed train passes near the station building. So the train may derail and hit the station building. Building a high-speed railway station usually uses a reinforced concrete structure. As a result of high impact energy on the impact body, the reinforced concrete (RC) member may fail; the impact point is near the member's foot; the structural member's constraint can be considered fixed support. This paper investigates the dynamic behavior of four types of circular reinforced concrete members under unequal lateral impact loads. The RC member's failure mechanism and dynamic response addressed the significance of unequal lateral impact load. The usual circular reinforced concrete members are used as the model to perform the drop-weight impact test. The specimens' crack pattern, failure mechanism, impact, deflection, and strain time–history curves are obtained. Findings show that between the impact point and the adjacent support, shear fractures occur that fail in shear mode. Shear cracks are based on impact velocity, longitudinal reinforcement ratio, and stirrup ratio. One type is more destructive to members and nodes. A shear fracture occurs when a longitudinal reinforcement fractures towards the closer support. The effects of impact velocity, longitudinal reinforcement ratio, and stirrup ratio on the dynamic impact response are studied. The experimental results may help improve structural member impact resistance. The critical section (right side) computed the static shear resistance using shear force, whereas the maximum external load resistance determines static bending moment resistance. Understanding how circular members fail to be subjected to unequal lateral impact loads provides insight into circular RC members' impact design and damage evaluation.

Traffic accidents and derailed train-related incidents have occurred more often than ever in recent years, resulting in some economic damage and casualties. Reinforced concrete (RC) constructions often involve derailed train and vehicle accidents. Rarely are such side collisions studied in previous studies. To do this, high-fidelity simulation-based finite-element (FE) models are created in this paper to accurately simulate the collision of circular RC members with a derailed train. The reinforced concrete member structure is common in high-speed railway stations. The impact energy of the impact body is significant, causing structural member failure. It analyses the dynamic behavior of reinforced concrete members under unequal span impact loads. Numerical implementations of impact issues are discussed from the perspective of geometric, contact, and material properties. The reliability and precision of the ABAQUS code to solve impact issues are verified by comparing failure modes, impact, and deflection time history experimental outputs. By analysing the impact response characteristics, used the control variables to study the failure process and mode (including the characteristics of impact and reaction forces, deflection time history curve, impact force–deflection curve, and bearing reaction force–deflection curve). The reinforcement ratio, impact velocity, concrete strength, and slenderness ratio significantly affect shear crack pattern and development. Changes in impact velocity and slenderness ratio also affect member failure modes.

The energy absorption characteristic of steel tube material and concrete material is an important indicator to reflect the impact resistance of circular concrete-filled steel tubular (CFST) members. In order to efficiently simulate the material energy absorption of the steel tube and concrete under lateral impact, a nonlinear finite element model considering the material strain rate of the circular CFST member was established and validated based on the drop weight tests. Then, the energy absorption mechanism of circular CFST members subjected to lateral impact was investigated including the revelation of the energy absorption process and the determination of the energy absorption distribution for the steel tube material and concrete material, which are obtained respectively based on the comprehensive analysis of dynamic response and innovative establishment of the segmented numerical model. In addition, the influence of impact momentum on energy absorption process and the effect of impact location on energy absorption distribution are further carried out. The observations of this investigation can provide reference for the anti-impact design and damage reinforcement of circular CFST members subjected to lateral impact.

The effects of nitrogen injection on the heat load in the scape-off layer are systematically investigated in the EAST double-null divertor configuration using EMC3-EIRENE code. Nitrogen impurities injected near the separatrix line and away from the separatrix line give rise to a non-axisymmetric distribution of heat load on the target plate. With impurity injection near the separatrix line, the occurrence of the toroidal asymmetric heat load is observed only nearby the toroidal injection location, while with injection away from the separatrix line the regions of the asymmetric heat load extend and deviate from the toroidal injection position. The competition between the friction force and the ion temperature gradient force has been analyzed. It shows that when impurities are injected away from the separatrix line more impurities can be parallelly transported to a further toroidal location, which results in the extension and deviation of the non-symmetric electron temperature. When the input power is increased, the non-symmetric phenomenon of the heat load turns to be insignificant due to the reduction of the impurity density in the downstream regions, as illustrated by the field line tracing technique. Furthermore, by scanning various injection positions in the EAST tokamak, the optimum location of impurity injection has been discovered.

A nonlinear finite element model of the circular concrete-filled steel tubular (CFST) member under lateral impact is established based on the existing drop weight tests, and the accuracy of numerical simulation is validated by comparing with the test results. Then the segmented numerical model of the circular CFST member is divided evenly to obtain the distribution of energy consumption along its length. The results indicate that the prime areas of energy consumption for the circular CFST member are distributed at the impact position (within 1/6 of the effective length) and the support position (within 1/12 of the effective length). On this basis, the affect of impact position on energy absorption distribution is carried out to reveal the changes of the prime areas of energy consumption. The results of this investigation can provide a reference for the impact resistant design and damage reinforcement of circular CFST members under lateral impact.

Original article: EPL , 129 (2020) 35001 .

1 Institute of Fusion Science, School of Physical Science and Technology, Southwest Jiaotong University, Chengdu, China 2 National Institute for Fusion Science, National Institutes of Natural Sciences, Toki, Japan 3 SOKENDAI (The Graduate University for Advanced Studies), Toki, Japan 4 Physics Department, Sichuan University, Chengdu, China 5 Hefei Keye Electro Physical Equipment Manufacturing Co., Ltd, Hefei, China

Kasper et al. have found that solar-wind helium could be heated to be nearly 7 times hotter than hydrogen on average from the observation of the Wind spacecraft. The stochastic Fermi mechanism is employed to investigate this phenomenon via the ion-cyclotron resonant process (Kasper J. C. et al., Phys. Rev. Lett., 110 (2013) 091102). Due to strong ion cyclotron resonances caused by counterpropagating Alfvén waves, the helium could be thermalized to be 7 times hotter than hydrogen. In this paper, a new aspect, the non-resonant interaction between thermal non-equilibrium particles and turbulent Alfvén waves, is utilized to illustrate the above observation analytically and numerically. The result of our model is broadly consistent with the observational result. Additionally, this paper predicts that the various temperature anisotropies of ions may exist in the solar-wind core which different thermal non-equilibrium factors lead to. This work builds up a close relation among non-resonant heating of thermal non-equilibrium ions, differential flow, and temperature anisotropy.