Search Results (116)

To address the impact-induced damage to concrete pile foundations of transmission structures caused by nearby blasting vibrations, this study investigates the dynamic splitting tensile behavior of an environmentally friendly lightweight rubberized concrete—Rubber-Toughened Ceramsite Concrete (RTCC)—under impact loading. Quasi-static tests show that the static splitting tensile strength increases first and then decreases with increasing rubber content, reaching a maximum value of 2.01 MPa at a 20% replacement ratio. Drop-weight impact tests indicate that RTCC20 exhibits the highest peak impact force (42.48 kN) and maximum absorbed energy (43.23 J) within the medium strain-rate range. Split Hopkinson Pressure Bar (SHPB) tests further demonstrate that RTCC20 shows the highest strain-rate sensitivity. Overall, RTCC with 20% rubber content provides the best comprehensive performance, achieving a favorable balance between strength and toughness across the entire strain-rate range. These findings offer experimental support for applying RTCC to blast-vibration-resistant transmission structure foundations. Full article

As a widely used structural material in construction, the energy dissipation characteristics of concrete under dynamic impact are crucial for evaluating a structure’s impact resistance and safety performance. However, conventional methods for evaluating energy dissipation characteristics fail to adequately account for the multi-parameter coupling effects during dynamic impact processes. Herein, the dynamic behavior of C15, C20, C30, and C40 concrete specimens was investigated using a split Hopkinson pressure bar (SHPB) apparatus. The dynamic response and energy dissipation mechanisms under impact loading were analyzed. The correlation between energy dissipation density and multiple parameters—including initial loading conditions, peak strain, dynamic compressive strength, and strain rate—was examined. Based on this analysis, a performance index P_i, grounded in energy dissipation density, was proposed for evaluating dynamic energy dissipation. The results show that under dynamic impact loading, concrete specimens of different grades basically show brittle damage mode and obvious strain-rate strengthening effect. Specifically, the dynamic compressive strength of C15-3 is 22.10 MPa, representing an increase of approximately 47.3%, while that of C40-3 is 46 MPa, showing an increase of approximately 15%. The energy transfer in concrete specimens is influenced by initial loading conditions, concrete material properties, and damage modes, among other factors. All of these parameters exhibit a strong correlation with the energy dissipation density. The comprehensive multi-parameter performance index P_i for dynamic energy dissipation yields superior evaluation results compared to using energy dissipation density alone. The research results provide an innovative reference for structural safety protection. Full article

Grouted corrugated duct connections offer advantages of simplicity and cost-effectiveness over alternative connection methods. Seismic damage investigations have revealed that severe out-of-plane damage can occur in shear walls, a vulnerability that is markedly exacerbated when single-row connection configurations are used. To evaluate their out-of-plane seismic performance, low-cycle reversed loading tests were conducted on six full-scale specimens comprising four precast walls (with vertical bar layout and axial load ratio varied as single-/double-row and 0/0.12) and two cast-in-place reference walls. The results indicate that all specimens failed in flexure, with precast walls exhibiting stiffness degradation patterns similar to their cast-in-place counterparts. Under an axial load ratio of 0.12, both wall types demonstrated hysteretic behavior with significant pinching. Although the bearing capacity of precast walls was reduced by up to 14% compared to cast-in-place walls, their ductility was markedly enhanced: displacement ductility coefficients reached 3.92 (double-row) and 5.37 (single-row), considerably exceeding the value of 2.73 for the cast-in-place wall. Under zero axial load, no strength degradation was observed at the test termination. The single-row connected specimen exhibited pronounced rocking behavior, with rocking displacement accounting for 49% of the total displacement. This resulted in severely pinched hysteresis loops and a cumulative energy dissipation capacity of less than 40% of that of the corresponding cast-in-place specimen. These findings necessitate the implementation of structural enhancement measures for single-row connections under low axial load ratios. Full article

Polypropylene (PP) fibers, known for their high fracture strength, low density, and cost-effectiveness, can significantly enhance the impact resistance of concrete, making the material suitable for specialized engineering applications. This study combined Split Hopkinson Pressure Bar (SHPB) tests with a three-dimensional mesoscale numerical model to investigate the dynamic compressive behavior of PP fiber-reinforced concrete (PFRC). The model, developed using MATLAB, explicitly represented polyhedral aggregates, mortar, the interfacial transition zone (ITZ), and PP fibers. Numerical simulations of impact compression were then performed using LS-DYNA and validated against experimental results. The simulated results exhibit close agreement with the experimental data in terms of peak stress, peak strain, and failure characteristics. The incorporation of 0.1% polypropylene fibers significantly enhanced the dynamic compressive strength of the specimen by 24.45%, with a mere 2.10% deviation from the experimental measurement. When the impact velocity was increased to 8 m/s and 10 m/s, the peak stress showed increases of 6.14% and 22.62%, respectively, while the peak strain increased by 11.72% and 23.32%. Damage analysis revealed that the aggregates experienced minimal failure, with cracks primarily initiating from the mortar and the ITZ. The polypropylene fibers improved the dynamic mechanical performance by dissipating energy through both fiber fracture and pull-out mechanisms. Furthermore, as the impact velocity increased, the fibers absorbed more energy, leading to a progressive increase in their own damage. Full article

Coupled high temperature and dynamic loading often leads to the complicated degradation of performance in industrial kilns, enclosures, or other concrete structures, which constitutes a serious hazard to the safety of concrete structure. To bridge this research gap, this study investigates not only the mechanical response but also the damage mechanisms of normal concrete (NC), basalt fiber-reinforced concrete (BFRC), and steel fiber-reinforced concrete (SFRC) under the coupled effects of high temperature and dynamic loading. Test specimens were conditioned for ambient conditions, 200 °C, 400 °C, and 600 °C, and underwent quasi-static and dynamic splitting tensile tests using the Split Hopkinson Pressure Bar (SHPB) with strain rates varying between 24 and 91 s⁻¹. Significantly, the high-temperature-induced degradation of all types of concrete is remarkably suppressed by fibers, especially steel fibers. The best thermal degradability resistance was displayed by the SFRC with the highest remaining residual dynamic strength, peak strain, and energy dissipation, especially in the most severe (600 °C, 0.15 MPa) circumstances among these three types of materials. All materials revealed a clear strain rate strengthening effect. An empirical model, integrating the coupling effect of strain rate, temperature, and fiber type in DIF, was also developed, yielding better prediction capability than those already available. This reveals that the comprehensive performance of SFRC can meet structure requests, so it is suitable for applications involving steel fiber in environments characterized by high temperature and high strain rates. Full article

Building structures are inherently susceptible to damage from extreme dynamic loads, while conventional concrete exhibits inadequate tensile resistance. While hybrid fibers systems can surpass the limitations of single-fiber reinforcement through their synergistic action, their internal damage mechanisms under impact loading remain inadequately understood. This study investigates the dynamic splitting behavior of hybrid fibers-reinforced cementitious composites combining polyvinyl alcohol (PVA) with either steel (SF) or polyethylene (PE) fibers, using Split Hopkinson Pressure Bar (SHPB) tests at strain rates of 5–31 s⁻¹, along with industrial CT scanning for meso-scale damage analysis. Results indicate that the SF–PVA hybrid improved strength by up to 15.6% compared to mono-PVA, while the PE–PVA hybrid achieved an 11.1% increase. All hybrid systems exhibited improved energy dissipation (which rose 25–45% with strain rate) and displayed secondary stress peaks. Quantitative CT analysis revealed distinct damage patterns: the mono-PVA specimen developed extensive damage networks (porosity: 7.20%; crack ratio: 4.48%), the SF-PVA hybrid system displayed the lowest damage indices (porosity: 3.29%; crack ratio: 1.76%), whereas the PE-PVA hybrid system exhibited the most significant dispersed damage pattern (crack-to-pore ratio: 39.32%). The hybrid systems function via distinct mechanisms: SF–PVA offers multi-scale reinforcement and superior damage suppression, whereas PE–PVA enables sequential energy dissipation, effectively dispersing concentrated damage. These insights support tailored fiber hybridization for impact-resistant structural design. Full article

In order to address the problems of high mechanical damage rate (MDR) and poor variety adaptability in mechanical peanut shelling, this paper improves a small, flexible arc-plates drum–circular grid bar concave screen-type peanut-shelling device. Firstly, by combining the Hertz theory and the Weibull distribution model, the shelling and separation models of drums of rigid rods and flexible arc-plates were established. Through comparative analysis, it was verified that the latter has a lower MDR and energy consumption and has excellent shelling performance. Then, through single-factor experiments and an Analysis of Variance (ANOVA), the influence laws of peanut moisture content, drum speed, shelling spacing, and hardness of flexible material (silicone) on the MDR and shelling efficiency (SE) were explored. Subsequently, Box–Behnken’s four-factor three-level regression experiments were carried out, and the optimal shelling operation parameters were obtained by using the response surface multi-objective optimization method (RSM) and verified experiments. The results show that when moisture content is 11%, drum speed is 227 rpm, shelling spacing is 24 mm, and silicone hardness is 40 HA, the kernel’s MDR after shelling is 4.73%, which is reduced by 5.51% and the SE is 95.21%, which is increased by 3%. The R² and the Root Mean Square Error (RMSE) of the actual value versus the predicted value of the model were 0.9921, 0.9624, 7.99 × 10⁻², and 3.1 × 10⁻³, respectively. The relevant research provides references for reducing losses, improving quality, and applying new materials for components in mechanical peanut shelling. Full article

Cyclic dynamic loading significantly influences the dynamic mechanical properties of cemented tailings backfill (CTB). This study investigates the dynamic mechanical properties and mesoscopic characteristics of CTB under cyclic dynamic loading. Using a Split Hopkinson Pressure Bar (SHPB) system, impact tests were conducted on CTB specimens subjected to varying numbers of cyclic impacts. The dynamic peak compressive strength (DPCS), elastic modulus, energy evolution, and failure modes were analyzed. Additionally, computed tomography (CT) scanning and 3D reconstruction techniques were employed to examine the internal pore and crack distribution. Results indicate that cyclic impacts lead to a gradual reduction in DPCS and energy absorption capacity, while the elastic modulus shows strain-rate dependency. Mesostructural analysis reveals that cyclic loading promotes the initiation and propagation of microcracks. This study establishes a correlation between mesoscopic damage evolution and macroscopic mechanical degradation, providing insights into the durability and stability of CTB under repeated blasting disturbances in mining environments. Full article

Understanding the combined effects of water and dynamic disturbance on rock behavior is essential for deep underground engineering, where groundwater and blasting often coexist. Existing studies have mainly emphasized static weakening by water or the strength characteristics under impact, while the energy evolution process remains insufficiently addressed. To fill this gap, uniaxial impact compression tests were conducted on dry and water-saturated skarn specimens using a separated Split Hopkinson Pressure Bar system. The relationship between peak stress and impact pressure was analyzed, and the total input energy, releasable elastic strain energy, and dissipated energy were quantified to examine their evolution with strain. The results indicate that water saturation significantly reduces dynamic strength and modifies the damage process. During the compaction and elastic stages, dissipated energy is low but slightly higher in water-saturated specimens due to microcrack initiation. In the plastic stage, dry specimens exhibit faster energy dissipation, while water-saturated specimens show reduced capacity for crack propagation dissipation. Damage–strain curves follow an S-shaped pattern, with water-saturated specimens presenting higher damage growth rates in the plastic stage. These findings clarify the energy-based damage mechanisms of skarn under impact loading and provide theoretical support for evaluating stability in water-rich underground environments. Full article

In order to study the damage evolution and fracture characteristics of rock with different composite modes in three layers under dynamic loading, rock specimens with different composite modes were made by using three materials: sandstone, marble and granite. The dynamic fracture impact test was carried out by using the Hopkinson pressure bar impact loading system, the voltage signal on the Hopkinson pressure bar was calculated and processed, and the crack propagation mode of the specimen was captured by using a high-speed camera, and the stress wave characteristics, stress time–history relationship and energy change characteristics of rocks with different composite modes were studied. At the same time, combined with Distinct Lattice Spring Model numerical simulation, the fracture process of the specimen was inverted, and the changes in stress intensity factor, stress change and load–displacement change in monitoring point were analyzed to compare the dynamic fracture behavior differences between different composite rocks. The results show that the dynamic fracture process captured by the high-speed camera has a good fit with the crack propagation process simulated by numerical simulation. When marble is used as the upper material, the energy transmittance is larger, and the transmission energy ratio between sandstone and granite is basically the same due to the large difference in hardness. When the comprehensive hardness of the specimen is the same, the smaller the hardness of the material at the cracking position, the faster the cracking will be, and the smaller the hardness of the second layer of the specimen at the cracking position, the faster the cracking speed of the specimen. In terms of dynamic fracture toughness, for specimens with little difference in hardness, when the impact end material is sandstone, the dynamic fracture extreme value of the specimen is lower, and when the sandstone material is used as the impact end material, it is more likely to crack. When the first layer of material is the same, the dynamic fracture toughness of the specimen with less hardness of the second layer of material is smaller, and the easier the crack development is. Full article

Rammed earth (RE) dwellings are characterized by accessible materials, low cost, and environmental sustainability. However, their poor seismic resistance limits their application. To address this issue, three conventional technical approaches have been developed: (1) adding cement to improve strength; (2) improving structural integrity using reinforced concrete ring beams and columns; and (3) embedding vertical steel bars in order to provide resistance against horizontal seismic actions. While effective, these methods rely on energy-intensive materials with high carbon emissions. In this study, we analyze the seismic damage characteristics and construction mechanisms of RE walls. The results reveal that the horizontal joints in RE walls significantly weaken their resistance to horizontal seismic actions. To mitigate this, three types of undulating joints are proposed and six specimens tested. The maximum horizontal loads of the specimens with local subsidence-type joints are 132.44 kN and 135.41 kN, respectively, which are approximately 50% higher than specimens with horizontal joints, whose maximum horizontal loads are 80.7 kN and 85.83 kN, respectively, while the maximum horizontal loads of the specimens with horizontally concatenated gentle arc-type joints are 151.17 kN and 173.58 kN, respectively, and they exhibit nearly double the shear capacity of the specimens with horizontal joints. Building on these findings and test results, we also include recommendations for integrating elegant RE wall texture design with seismic-resistant undulating joint technology. Full article

Dynamic fatigue of rocks under repeated cyclic impact is a nonconservative property, as surrounding rocks in real environments subjects them to variable impact disturbances, and the degree of damage varies under different energy level loads. To evaluate the dynamic response and fatigue damage characteristics of rocks under multi-level cyclic impacts, uniaxial cyclic impact tests were carried out on granite with various stress paths and energy levels using a modified split Hopkinson pressure bar. Dynamic deformation characteristics of specimens under different loading modes were investigated by introducing the deformation modulus of the loading stage. Evolution of macroscopic cracks during the impact process was investigated based on high-speed camera images, and the microscopic structure of damaged specimens was examined using SEM. In addition, cumulative energy dissipation was used to assess the damage of rocks. Results show that the deformation modulus of the loading stage, dynamic peak stress and strain of specimens increase with the impact energy, and the deformation modulus of the loading stage decreases as the damage level increases. Propagation rate of tensile cracks in rock was correlated with participation time of the higher energy level, which observed the following sequence: linearly decreasing > same > linearly increasing energy level, and cyclic loading of nonlinear energy level produced more tensile cracks and rock spalling than the same energy level. Compared with cyclic impacts of the same energy level, multi-level impacts form more microcracks and fatigue striations. The cumulative rate of specimen damage under the same energy change rate is as follows: linear decreasing > same > linear increasing loading. This provides a new case study for evaluating the dynamic damage, crushing efficiency and load-bearing capacity of rocks in real engineering environments. Full article

This study proposes a precast concrete bridge pier system designed to enhance seismic resilience and post-earthquake reparability. The structural configuration integrates ultra-high-performance concrete (UHPC), externally replaceable steel-angle energy-dissipating components, and unbonded post-tensioned tendons. The seismic performance of the system was evaluated through quasi-static tests under cyclic loading. Experimental results demonstrated that the proposed pier exhibited stable hysteretic behavior and minimal residual displacement, effectively concentrating damage within the intended plastic hinge region. The superior strength of UHPC further contributed to improved load-bearing capacity and less localized concrete compressive damage at the rocking interface. The external steel angles improved the energy dissipation capacity of the precast column significantly, and its external arrangement made the post-earthquake replacement much easier as compared to internal energy dissipation bars. The feasibility of the proposed seismic-resilient pier system was successfully validated, offering a promising solution for bridge design in high-seismic-intensity regions. Full article

Microwave-assisted rock fragmentation has been considered as one of the most promising technologies in rock excavation, but due to the fact that excavation is usually carried out in water-rich environments, understanding the dynamic fracture properties of rocks with different water contents after microwave irradiation is thus desirable. This study employed an enhanced split Hopkinson pressure bar (SHPB) system to perform dynamic fracture tests on pre-cracked semi-circular bending (SCB) specimens. It systematically explores the changes in the mechanical properties of sandstone under both dry and saturated conditions after exposure to 700 W of microwave radiation for 10 min. Infrared thermal imaging was utilized to capture the temperature distribution across the specimens, while digital image correlation (DIC) and high-speed photography were used to simultaneously record the crack propagation process. Based on the principle of energy conservation, the analysis of energy dissipation during fracture was performed, and the micro-damage evolution mechanism of the material was revealed through scanning electron microscopy (SEM). The results demonstrated that saturated sandstone exhibited a more rapid heating response and significantly lower dynamic fracture toughness and fracture energy compared to dry samples after microwave irradiation. These findings indicate that water saturation amplifies the weakening effect induced by microwaves, making the rock more susceptible to low-stress fractures. The underlying damage mechanisms of microwave radiation on water-bearing sandstone were interpreted with the theory of pore water pressure and structural thermal stresses. Full article

Aramid fibre has become a critical material for individual soft body armour due to its lightweight nature and exceptional impact resistance. To investigate its energy absorption mechanism, quasi-static and dynamic tensile experiments were conducted on Kevlar^® 29 plain-woven fabric using a universal material testing machine and a Split Hopkinson Tensile Bar (SHTB) apparatus. Tensile mechanical responses were obtained under various strain rates. Fracture morphology was characterised using scanning electron microscopy (SEM) and ultra-depth three-dimensional microscopy, followed by an analysis of microstructural damage patterns. Considering the strain rate effect, a viscoelastic constitutive model was developed. The results indicate that the tensile mechanical properties of Kevlar^® 29 plain-woven fabric are strain-rate dependent. Tensile strength, elastic modulus, and toughness increase with strain rate, whereas fracture strain decreases. Under quasi-static loading, the fracture surface exhibits plastic flow, with slight axial splitting and tapered fibre ends, indicating ductile failure. In contrast, dynamic loading leads to pronounced axial splitting with reduced split depth, simultaneous rupture of fibre skin and core layers, and fibrillation phenomena, suggesting brittle fracture characteristics. The modified three-element viscoelastic constitutive model effectively captures the strain-rate effect and accurately describes the tensile behaviour of the plain-woven fabric across different strain rates. These findings provide valuable data support for research on ballistic mechanisms and the performance optimisation of protective materials. Full article