Lateral Impact Research Articles

Refining Operative Indications for Zygomaticomaxillary Complex Fracture Repair

Study Design Case-control. Objective Although zygomaticomaxillary complex (ZMC) fractures are among the most common facial injuries, the optimal approach to management remains controversial. This study analyzes the relationship between displacement measures derived from pre-operative CT imaging and clinical symptomatology to enhance surgeon understanding of the need for operative intervention. Methods A retrospective analysis was conducted on 95 patients with ZMC fractures seen at a single institution between 2015 and 2020. Patient demographics, CT characteristics, and symptoms prompting surgery were recorded from the medical record. Statistical analysis was conducted to determine relationships between radiographic characteristics, symptomatology, and need for operative intervention. Results Malar flattening or facial asymmetry was significantly predicted by lateral maxillary wall impaction (OR = 1.36 , P < .001) and anterior-posterior displacement (OR = 1.18, P = .01). Infraorbital rim step-off was significantly associated with lateral maxillary wall impaction (OR = 1.23, P < .01). Vertical displacement predicted complaint of malocclusion (OR = 1.47, P = .03). Moreover, fractures with posterior displacement greater than 2.5 mm (OR = 14.3, P < .001) or lateral maxillary wall impaction greater than 4.5 mm (OR = 12.0, P < .001) were significantly more likely to be considered operative. Fractures displaced less than 15 mm total in all directions (OR = 16.0, P < .001) were less likely to require surgery. Conclusions CT characteristics of ZMC fractures reliably predict a patient’s likelihood of developing symptoms, indicating surgical intervention. We hope these findings will aid in surgical decision-making regarding the management of ZMC fractures.

Lateral force controlled impact tribometer characterizing transient friction: Effect of contact pressure

A new Lateral Force Impact Tribometer (LFIT) is designed to quantify the dynamic friction of synthetic seat belt and D Ring Polymer (DRP) under transient conditions during the initial sliding period. LFIT simulates the sliding between two bodies subjected to a sudden lateral force applied, resulting in relative motion. Transient friction under suddenly applied initial acceleration conditions is obtained from the displacement response. LFIT overcomes stiffness concerns of most displacement-controlled tribometers in which the sensors and actuators influence the contact stiffness, nature of asperity interaction, and frictional characteristics. The displacement vs. time response showed the variation in displacement during the initial 0.3 mm sliding distance. LFIT is modelled as a spring-mass-Coulomb damper system applied for transient analysis. The effect of contact pressure on the transient Coefficient of Friction (CoF) is studied in the present work. This paper perhaps presents the first report that enables the capture of the friction transition within 10 ms from the start of sliding.

Finite element analysis of locally strengthened stainless-steel tube under lateral impact loading

In this study, a Finite Element (FE) model of locally strengthened high-strength stainless-steel tube subjected to lateral impact loads is established using LS-DYNA to investigate its dynamic behaviours. The accuracy of the FE results is verified by comparing with the test results. The impact force, bending moment, stress and strain responses as well as the internal energy dissipation histories of the strengthened tube are analysed during the entire impact process. The results indicate that the impact resistance of the strengthened tube is obviously enhanced as compared to hollow stainless-steel tube. Furthermore, parametric studies are conducted to reveal the influence of axial compressive force, impact position, impact velocity and material strength on the impact behaviour of the strengthened tube. The results show that the application of axial compressive force reduced the impact force and increased the deformations of the strengthened tube. The impact resistance of the strengthened tube performed an increasing trend when moving the impact position towards the support and increasing the material strength. In addition, the increase of impact velocity significantly reduced the impact duration. Finally, design recommendations and process were proposed to facilitate the application of locally strengthened tube.

Hip joint center lateralization minimally affects the biomechanics of patient-specific flanged acetabular components: A computational model.

Patient-specific flanged acetabular components are utilized to treat failed total hip arthroplasties with large acetabular defects. Previous clinical studies from our institution showed that these implants tend to lateralize the acetabular center of rotation. However, the clinical impact of lateralization on implant survivorship is debated. Our goal was to develop a finite element model to quantify how lateralization of the native hip center affects periprosthetic strain and implant-bone micromotion distributions in a static level gait loading condition. To build the model, we computationally created a superomedial acetabular defect in a computed tomography 3D reconstruction of a native pelvis and designed a flanged acetabular implant to address this simulated bone defect. We modeled two implants, one with ~1 cm and a second with ~2 cm of hip center lateralization. We applied the maximum hip contact force and corresponding abductor force observed during level gait. The resulting strains were compared to bone fatigue strength (0.3% strain) and the micromotions were compared to the threshold for bone ingrowth (20 µm). Overall, the model demonstrated that the additional lateralization only slightly increased the area of bone at risk of failure and decreased the areas compatible with bone ingrowth. This computational study of patient-specific acetabular implants establishes the utility of our modeling approach. Further refinement will yield a model that can explore a multitude of variables and could be used to develop a biomechanically-based acetabular bone loss classification system to guide the development of patient-specific implants in the treatment of large acetabular bone defects.

Accessing quasi-static impact process by 3D-NPR corrugated metamaterials

The conventional impact process is a quintessential impulse process that causes substantial damage due to the high initial impact force. However, the impact effect can be significantly diminished by making the impulse process quasi-statically by using a three-dimensional negative Poisson's ratio corrugated metamaterial (3D-NPRCM) structure. This paper proposes a novel 3D-NPRCM obtained by folding the 2D-NPRCM. This study examines the crashworthiness properties and impact force of 3D-NPRCM subjected to impact using the finite element method (FEM). The results reveal that the sequential matrix structure has the ability to make impact impulse processes quasi-statically. The effects of various folding angles, arrangements, and geometrical parameters on the properties are also explored. Finally, the 3D-NPRCM is employed in an automobile crash box design. Through axial quasi-static compression simulation, the peak crushing force of the 3D-NPRCM crash box is reduced by 25.374 % from 211.652 kN to 157.946 kN, and the energy absorbed is increased by 23.830 % from 11.259 kJ to 13.942 kJ, compared to the conventional crash box. Through cart lateral impact simulation, the peak crushing force of the 3D-NPRCM crash box is reduced by 18.076 % from 206.9 kN to 169.5 kN, and the compressive displacement is decreased by 9.457 % from 235.8 mm to 213.5 mm. This work presents a novel design proposition for a crash box in vehicle engineering and demonstrates a fresh approach to expand the design of three-dimensional mechanical metamaterials.

Dynamic behaviors of eccentrically loaded RC column under lateral low-velocity impact

This study aims to examine the influence of eccentric axial loads on the lateral low-velocity impact behaviors of RC columns. Firstly, the numerical simulation approach is validated by accurately reproducing the impact force, as well as the deflection, axial load and failure mode of columns in pendulum impact and eccentrically loading tests. Secondly, the effects of the axial load ratios and eccentric distances on the dynamic behaviors of RC columns are analyzed as follows: (i) Increasing the axial load ratio and the eccentric distance at the impact direction can reduce the deflection of RC columns when the axial load ratio is relatively low; (ii) the instability failure could occur on columns with large enough axial load and impact energy; (iii) the eccentric distance of axial loads on the fixed-supported RC column can be neglected since the induced boundary rotation is constrained by fixed supports; (iv) for RC columns with pinned-fixed or pinned-pinned supports, the eccentric distance at the impact direction should be considered, while the eccentric distance at the vertical impact direction can be neglected. Furthermore, the dynamic coupled flexural and shear resistance function of eccentrically loaded RC columns are established and validated. A 2DOF model is presented to predict low-velocity impact behaviors of RC columns with varying axial load ratios and eccentric distances. The failure modes transition mechanism induced by the axial load is further revealed. Increasing axial loads can enhance columns’ flexural resistance and tendency of failure mode from flexural to shear/flexure-shear. The P-δ effect is amplified by larger axial loads and deflections, causing the instability failure of columns. Finally, a theoretical impact energy of the critical instability of eccentrically loaded RC columns is proposed to assist the structural impact-resistant design.

Experimental and numerical study on the blast performance of the corrugated double steel plate concrete composite wallboard under blast loads

The corrugated double steel plate concrete composite wallboard (CDSCW) exhibits superior axial compressive load-bearing capacity, lateral flexural stiffness, impact resistance, and seismic performance compared to the traditional reinforced concrete wallboard and plane double steel plate concrete composite wallboard (PDSCW). Therefore, it has great potential application in offshore engineering and military engineering. This study designs and fabricates two types of CDSCW specimens. Firstly, a comparative analysis is conducted to examine the damage patterns and dynamic responses of the two specimens under near-field explosion experiments. Secondly, the damage mechanisms and explosion response of CDSCW and PDSCW subjected to close-in explosions are numerically investigated by using ANSYS/LS-DYNA, and the results are then compared with experimental findings. Parameter analysis is performed to assess the influence of concrete thickness, steel plate thickness, and explosive charge on the blast resistance of CDSCWs. Furthermore, a nonlinear resistance equation and an equivalent single degree of freedom (ESDOF) theoretical model for simply supported beams is established to predict the dynamic response of CDSCWs under near-blast loads. This theoretical model considers the constitutive model of bilinear materials and the effect of plastic hinges. The reliability of the proposed theoretical model is verified by comparing the residual deflection of CDSCWs obtained from explosion tests with validated numerical simulation results. The results demonstrate that the CDSCWs, with the same concrete and component dimensions (length, width), exhibit greater flexural stiffness and superior energy dissipation capacity subjected to close-in explosion. Moreover, their blast resistance significantly surpasses that of PDSCWs. In particular, an increase in corrugation depth effectively improves the blast resistance of CDSCWs. The dynamic response equations, based on the established elastic-plastic model and primarily considering bending deformation of the components, precisely predict the dynamic response of simply supported CDSCWs under near-blast loads. consequently, these findings can provide a robust foundation for further research and the design of blast-resistant structures.

Changes in ulnar and median nerve conduction velocity after reverse total shoulder arthroplasty: Correlation with distalization and lateralization

PurposeThe purpose of this study was to assess ulnar and median nerve injury after reverse total shoulder arthroplasty (RSA) by measuring the sensory nerve conduction velocity (SCV). The secondary objective was to evaluate the impact of lateralization and/or distalization on SCV changes. MethodsTwenty consecutive cases were prospectively included and retrospectively reviewed. SCV of the ulnar and median nerves as well as humeral lateralization/distalization quantified by plain radiography were evaluated pre-operatively and at 1 week post-operatively. Changes in SCV were tested using the paired t-test, and correlations between humeral lateralization/distalization and SCV changes were tested using Kendall's rank correlation coefficient and maximal information coefficient (MIC). ResultsThe SCV of the ulnar nerve was delayed from 55.4 ​m/s pre-operatively to 53.0 ​m/s post-operatively (p ​= ​0.021), whereas there was no significant change in the median nerve (p ​= ​0.17). There was a weak to moderate correlation between ulnar nerve SCV delay and lateralization (τ ​= ​−0.38; p ​= ​0.021; MIC ​= ​0.70) but no significant correlation with distalization (p ​= ​0.65; MIC ​= ​0.56). ConclusionsFollowing RSA, a small but significant delay in SCV of the ulnar nerve was observed. A negative correlation was found between lateralization and SCV delay of the ulnar nerve.

Experimental investigation of aluminium alloy gusset joints’ dynamic response to lateral impact loads: Evaluating the influence of gusset plate bending stiffness

The traditional aluminium alloy gusset plate (AAG) joint is commonly regarded as a representative semi-rigid joint characterized by limited stiffness. This deficiency in stiffness significantly hampers its capacity for load transmission and resistance against progressive collapse in spatial grid structures. Notably, the dynamic response characteristics of semi-rigid joints, especially when subjected to short-term, highly intense loads such as impacts and explosions, deviate substantially from those of rigid joints. This research examines the dynamic failure behavior of six distinct traditional AAG joints with varying degrees of stiffness when subjected to impact loads. The first group comprises three specimens where the variance in AAG joint stiffness is achieved by altering the gusset plate’s diameter. The second group comprises three specimens aiming to manipulate the AAG joint’s stiffness by modifying the gusset plate’s thickness. The study yielded comprehensive data, including stress profiles, displacement patterns, acceleration time history curves, and failure modes of AAG joints. The experimental findings revealed that both groups of AAG joints under lateral impact loads exhibited brittle failure. The predominant failure modes included the rupture of the H-shaped aluminium alloy beam, distortional buckling of the beam, and warping of the thinner gusset plate. It is evident from the stress, displacement, and acceleration time history curves that the AAG joint adheres to the characteristics of a typical semi-rigid joint, and the diameter and thickness of the gusset plate exert significant influence on the AAG joint’s dynamic response. Subsequently, the six test conditions were simulated using ANSYS/LS-DYNA software. This simulation considered the stress distribution, impact force time history curves, and strain energy time history curves of AAG joints. It facilitated a detailed discussion of the failure mechanism underlying AAG joints when subjected to lateral impact loads.

Using leeward air-blowing to alleviate the aerodynamic lateral impact of trains at diverse yaw angles

The safety risks of high-speed trains in crosswind environments escalate with increasing train speeds. The present study employs the improved delayed detached eddy simulation method based on the shear stress transport k–ω turbulence model to evaluate an active control method targeting the reduction of lateral forces acting on the train. The effects of air blowing strategy on the leeward side of the train are examined considering different yaw angles and blowing speeds. The findings reveal that the active air blowing, mixed with the flow laterally downstream the train roof, induces the increase in the local turbulence and alters the surface pressure distribution. Within the investigated range of yaw angles, the active air blowing yields a lateral force reduction ranging from 1.0% to 8.8%. Varying the blowing speed can further decrease the lateral force of the entire train by 5.9% and 0.8% at yaw angles of 15° and 75°, respectively. The power invested in active blowing demonstrates maximum returns at a yaw angle near 45° while diminishing with increasing blowing speed.

Dynamic response of piles embedded in granular soil to lateral impacts

Soil-embedded vehicle barriers, such as W-beam guardrail systems, play a pivotal role in transportation safety, mitigating the risks associated with vehicular collisions with roadside hazards. The efficacy of these barriers greatly depends on the pile-soil system's kinetic energy dissipation capability during vehicular impacts. However, a comprehensive understanding of how soil strength, embedment depth, and impact velocity collectively govern the dynamic behavior of the pile-soil system remains a gap in current research. This study explores the dynamics of lateral impacts on piles embedded in various granular soils. The process of dynamic lateral impact and interaction between the pile and the soil was modeled using the Updated Lagrangian Finite Element Method (UL-FEM). A damage-based element erosion algorithm was incorporated into the model to accommodate severe mesh distortions and element entanglements of the soil material brought by the pile impact. Validation against well-documented large-scale physical impact tests ascertained the model's fidelity. Our findings elucidate the significant differences in resistive forces between piles in strong versus weak granular soils – notably, the former exhibited resistive forces roughly double their weaker counterparts under equivalent embedment depths and varied impact velocities. Intriguingly, a stiff pile in weak soil necessitates nearly double the embedment depth to match the energy dissipation of its strong-soil counterpart. Furthermore, the study discerned consistent depth of rotation point ranges for piles embedded in distinct soil strengths, regardless of embedment depth and impact velocity.

Correlation between Malocclusion and Mandibular Fractures: An Experimental Study Comparing Dynamic Finite Element Models and Clinical Case Studies.

Mandibular fractures are very common in maxillofacial trauma surgery. While previous studies have focused on possible risk factors related to post-operative complications, none have tried to identify pre-existing conditions that may increase the risk of mandibular fractures. We hypothesized, through clinical observation, that anatomical conditions involving poor dental contacts, such as malocclusions, may increase the risk of mandibular fractures. This work was subdivided into two parts. In the first part, Digital Imaging and Communications in Medicine (DICOM) data of four healthy patients characterized by different dentoskeletal occlusions (class I, class II, class III, and anterior open bite) have been used to develop four finite element models (FEMs) that accurately reproduce human bone structure. A vertical and lateral impact have been simulated at increasing speed on each model, analyzing the force distribution within the mandibular bone. Both vertical and lateral impact showed higher level of stress at the impact point and in the condylar area in models characterized by malocclusion. Specifically, the class III and the open bite models, at the same speed of impact, had higher values for a longer period, reaching critical stress levels that are correlated with mandibular fracture, while normal occlusion seems to be a protective condition. In the second part of this study, the engineering results were validated through the comparison with a sample of patients previously treated for mandibular fracture. Data from 223 mandibular fractures, due to low-energy injuries, were retrospectively collected to evaluate a possible correlation between pre-existing malocclusion and fracture patterns, considering grade of displacement, numbers of foci, and associated CFI score. Patients were classified, according to their occlusion, into Class I, Class II, Class III, and anterior open bite or poor occlusal contact (POC). Class I patients showed lower frequencies of fracture than class II, III, and open bite or POC patients. Class I was associated with displaced fractures in 16.1% of cases, class II in 47.1%, class III in 48.8% and open bite/POC in 65.2% of cases (p-value < 0.0001). In class I patients we observed a single non-displaced fracture in 51.6% of cases, compared to 12.9% of Class II, 19.5% of Class III and 22.7% of the open bite/POC group. Our analysis shows that class I appears to better dissipate forces applied on the mandible in low-energy injuries. A higher number of dental contacts showed a lower rate of multifocal and displaced fractures, mitigating the effect of direct forces onto the bone. The correlation between clinical data and virtual simulation on FEM models seems to point out that virtual simulation successfully predicts fracture patterns and risk of association with different type of occlusion. Better knowledge of biomechanics and force dissipation on the human body may lead to the development of more effective safety devices, and help select patients to plan medical, orthodontic/dental, and/or surgical intervention to prevent injuries.

Impact force curve feature and failure mode identification method of concrete-filled steel tube members under lateral impact

A collision accident caused by derailed trains is a potential safety hazard for the structure adjacent to high-speed rail lines. Concrete-filled steel tube (CFST) columns are frequently utilized in modern high-speed railway stations, however CFST station columns may suffer severe damage from train collisions because of their high impact energy. Therefore, the method of identifying CFST members' failure modes under large impact energy was investigated in this paper. Adopting numerical simulation by LS-DYNA, the corresponding relationship between the local indentation and impact process was researched, the characteristic impact force time-history curve was proposed, and the effects of impactor and CFST specimen parameters on impact force feature were analyzed. The plateau proportion was established and quantified, then the mapping relationship between plateau proportion and failure degree was acquired. Research results indicated that local indentation developed primarily at impact force plateau stage. CFST specimens showed bending deflection when plateau proportion was below 67.5%, experienced fracture failure when it was above 77%, and exhibited crack failure when it was in between respectively. Finally, the empirical formulas for plateau proportion and maximum deflection were established, and a simplified approach for predicting the failure modes was put forward. The research provides suggestions for identifying damage patterns and strengthening CFST columns subjected to lateral impact loads.

Comprehensive Numerical Modeling of Prestressed Girder Bridges under Low-Velocity Impact

Accidental collisions involving over-height trucks that exceed vertical clearance limits and bridge superstructures frequently happen, resulting in compromised girders and potential threats to structural safety and performance. The numerical simulation of large-scale prestressed girder bridge collisions poses challenges due to the associated nonlinearities, as well as the limited availability of large-scale experimental testing data in the literature due to cost and complexity constraints. This study introduces a numerical modeling approach to efficiently capture the response of prestressed girder bridges under lateral impact loads. A finite element (FE) model was developed using LS-DYNA and meticulously validated against experimental data from the literature. The study explored four methods for applying prestressing forces and evaluated the performance of four concrete material constitutive models, including the Continuous Surface Cap Model (CSCM), Concrete Damage Plastic Model (CDPM), Karagozian &amp; Case Concrete (KCC) model, and Winfrith concrete model, under impact loads. Furthermore, an impact study was conducted to investigate the influence of impact speed, impact mass, and prestressing force on the behavior of prestressed girder bridges. Utilizing the dynamic relaxation (DR) approach, the developed FE model precisely captured the response of prestressed girders under impact loads. The CSCM yielded the most accurate predictions of impact forces, with an error of less than 8%, and demonstrated a strong ability to predict damage patterns. Impact speed, mass, and the presence of prestressing force showed a significant influence on the resulting peak impact force experienced by the girder. Furthermore, the study underscores the composite nature of the bridge’s response and emphasizes the importance of analyzing the bridge as a whole rather than focusing solely on individual girders.

Influence of centroid acceleration acquisition and filtering class on head injury criterion evaluation

BackgroundAlthough the Head Injury Criteria (HIC) has been widely applied to assess head impact injuries, it faces two outstanding problems: 1) HIC is affected strongly by the cut-off frequency when processing acceleration signals. And these cut-off frequencies are experiential and lack unified guidelines; 2) If the head was impacted on a different part, should the corresponding HIC threshold be the same? If these problems are not resolved, it could potentially lead to a critical misinterpretation of the safety assessment. MethodsFinite element method was used to reconstruct head impacts. The head model includes tissues like skull, brainstem, cerebrospinal fluid, etc. The head model was impacted in the frontal, occipital, parietal or lateral direction with different impact velocities. Acceleration signals of the head model were extracted directly from the skull and the head centroid node. To obtain a robust HIC, the filtering class of acceleration signals were analyzed carefully. Then, the relation between rigid body HIC and the centroid node HIC were studied systematically. ResultsWhen the filtering class of rigid body acceleration and centroid node acceleration reached the cut-off frequency, the corresponding derivative of HIC tended to change smoothly. Using these cut-off frequencies, robust HICs were obtained. The rigid body HIC far exceeded that of centroid node HIC, such as 8, 9, 14 and 31 times exceeded in the frontal, occipital, parietal and lateral impact conditions, respectively. Moreover, approximate linear relations were found between the rigid body HIC and the centroid node HIC in different impact directions, respectively. From these relations, the injury thresholds of rigid body HIC of various directions were given quantitatively. ConclusionsThe rational filtering class like CFC 800 and CFC 700 were given for rigid body HIC and centroid node HIC, respectively. The rigid body HIC had a significant discrepancy from the centroid node HIC. Linear relations between the rigid body HIC and centroid node HIC were found, and their slopes changed with impact directions. From these relations, we can adjust the injury thresholds reasonably if the head receives different impacts. These findings can effectively enhance the applicability of HIC.

The Influence of a Booster Seat on the Motion of the Reclined Small Female Anthropomorphic Test Device in Low-Acceleration Far-Side Lateral Oblique Impacts.

Belt-positioning booster (BPB) seats may prevent submarining in reclined child occupants in frontal impacts. BPB-seated child volunteers showed reduced lateral displacement in reclined seating in low-acceleration lateral-oblique impacts. As submarining was particularly evident in reclined small adult female occupants, we examined if a booster seat could provide similar effects on the kinematics of the small female occupant to the ones found on the reclined child volunteers in low-acceleration far-side lateral oblique impacts. The THOR-AV-5F was seated on a vehicle seat on a sled simulating a far-side lateral-oblique impact (80 deg from frontal, maximum acceleration ∼2 g, duration ∼170 ms). Lateral and forward head and trunk displacements, trunk rotation, knee-head distance, seatbelt loads, and head acceleration were recorded. Three seatback angles (25 deg, 45 deg, 60 deg) and two booster conditions were examined. Lateral peak head and trunk displacements decreased in more severe reclined seatback angles (25-36 mm decrease compared to nominal). Forward peak head, trunk displacements, and knee-head distance were greater with the seatback reclined and no BPB. Knee-head distance increased in the severe reclined angle also with the booster seat (>40 mm compared to nominal). Seat belt peak loads increased with increased recline angle with the booster, but not without the booster seat. Booster-like solutions may be beneficial for reclined small female adult occupants to reduce head and trunk displacements in far-side lateral-oblique impacts, and knee-head distance and motion variability in severe reclined seatback angles.

Treatment strategy for severe implosion injuries of the lateral chest wall

In the majority of cases implosion injuries to the thoracic wall are caused by blunt, massive force acting on the thorax. Basically, different regions and directions of the acting energy have to be taken into account. In common usage, the term implosion injury has become established, especially for the sequelae of lateral energy impact. Particular attention should be paid to the stability of the shoulder girdle, the underlying hemithorax and its intrathoracic organs.

Stability analysis and control countermeasures of surrounding rock of gob-side entry formed by roof-cutting in inclined coal seams

The stability of the surrounding rock in the inclined coal seam stope is crucial for the safety of the gob-side entry. In this article, we systematically analyze the surrounding rock stability of the gob-side entry formed by roof-cutting (GEFR) in an inclined coal seam. We identify three forms of roof structure evolution in the formation process of GEFR and analyze the two main modules affecting the deformation of the surrounding rock structure. We determine the critical elements of surrounding rock deformation in different stages of the GEFR retaining process. Further, we propose a classification of the deformation of the surrounding rock structure of GEFR into stress and structural types during stabilization. We analyze the length of the gangue side's bearing area and calculate the lateral gangue's impact energy. We establish three instability modes of the roof based on the fractured state of the roof structure of the GEFR and provide a mechanical criterion of instability. Finally, based on the results of our theoretical analysis, we propose a control principle for the surrounding rock deformation of GEFR and establish countermeasures for controlling the roof-cutting angle and an asymmetric coupling support system. A field case study was conducted under conditions involving an inclined thick coal seam to investigate the surrounding rock deformation and overburden stress evolution using field monitoring data. The field test results confirm that the control measures of the control roof-cutting angle and the asymmetric coupling support system positively impact the stability of the surrounding rock of the roof-cutting entry in an inclined coal seam.

Investigating the effectiveness of CFRP strengthening in improving the impact performance of RC members

Rising global rail infrastructure expansion has increased accidents involving train derailments. Reinforced concrete (RC) elements require impact-resistance enhancement to prevent structural damage or failure. While extensive research has analyzed CFRP-strengthened concrete columns under dynamic loading, further understanding of CFRP's impact on RC members is needed. Considering dynamic factors, this study investigates CFRP-RC components' performance under asymmetric impact. Components wrapped in one, four, or six CFRP layers underwent high-energy asymmetric lateral impact testing to obtain deflection-time curves. Results showed that multiple CFRP layers significantly improved impact resistance by increasing plateau force, reducing maximum deflection to 42%, and shortening duration. Longitudinal-circumferential bonding conferred better reinforcement than other arrangements. However, multiple CFRP layers increased fracture susceptibility due to severe concrete damage. An equation was derived from dynamic equilibrium principles. Finite element modeling validated experimentally was used to simulate lateral impact. Impact force, deflection, and bending moment over time were compared. Impact resistance, flexural capacity, plastic deformation, and energy absorption were also examined. Internal force distribution and development were analyzed. A simplified calculation estimated maximum deflection. CFRP reinforcement methods' effects were examined. Results indicate CFRP elevates plateau impact force and average bending moment while significantly decreasing deflection and duration, greatly enhancing impact resistance and flexural bearing capacity.

Experimental and theoretical investigation on residual bearing capacity of CFDST-T joints after lateral impact

This study investigates the residual performance of concrete-filled double-skin steel tubular (CFDST) T-joints after lateral impact. One hollow T-joint and five CFDST-T joints with various steel tube thickness and hollow rate were first tested by a pendulum machine. The axial compression test was subsequently performed to explore the residual performance in terms of failure mode, residual bearing capacity, ductility, energy dissipation, and strain evolution. Results indicated that the failure modes of the CFDST-T joint and hollow T-joint were characterized by global bending and severe local indentation, respectively. Besides, the CFDST-T joints exhibited the strongest residual bearing capacity with a hollow rate of 0.52 and the greatest ductility of 0.63. Moreover, increasing the outer tube thickness improved the residual bearing capacity and simultaneously reduced the ductility coefficient while the inner tube exerted little effect on residual performance. Simplified calculation formulas were finally derived to predict the impact residual deflection and residual bearing capacity of the CFDST-T joint based on parametric analysis. This study will provide a reference for future research to contribute to the design of more reasonable CFDST-T joints and promote their application.