Reduction Of Displacement Research Articles

Modeling of the shear thickening fluid damper and vibration control for stay-cable

Based on the arctangent function, this work proposes a parametric model to predict the mechanical behavior of a shear thickening fluid damper. The parameters of this model are a function of the maximum operating velocity of the damper. The validity and accuracy of the model's damping force and displacement relationship under different sinusoidal loads and various seismic wave excitations are verified based on experimental data. On this basis, compared to a viscous damper, the finite element models of a stay-cable and shear thickening fluid damper system are established to evaluate the vibration reduction performance and mechanical advantages of the shear thickening fluid damper. The research shows that a shear thickening fluid damper can significantly reduce the amplitude of the stay-cable's primary resonance and main parametric vibration, with displacement reduction rates of 72.5 and 81.9%, respectively. Importantly, compared to viscous dampers, under the premise that both have the same damping force, the vibration reduction effect of shear thickening fluid dampers is more significant, 1.3 times and 1.15 times that of viscous dampers, and the stroke is only 55.2 and 59.7% of that of viscous dampers. These data indicate that shear thickening fluid dampers can provide a more significant damping force for stay-cable in limited space.

The role of an active muscular subsystem in prone instability test during rest and leg raise conditions.

Clinicians commonly used prone instability test (PIT) by assessing the posterior-to-anterior (PA) displacement to identify lumbar instability. Most studies focusing on passive subsystem found greater mobility in lower lumbar (L4-L5) than upper lumbar (L1-L3) spine. However, there is still a lack of evidence to demonstrate the role of active subsystem. Additionally, it is unclear whether sex affects PA displacements. To determine differences in displacement among five lumbar segments, between two testing positions (rest and leg raise), and between male and female during PIT in individuals with chronic non-specific low back pain (CNLBP). A cross-sectional study design. Spine biomechanics laboratory. Individuals with CNLBP. An electromagnetic tracking system was used to measure PA displacement with sensors attached at T12, S2 and a hand-held dynamometer. Participants were asked to perform PIT, while a 100N force was applied to each lumbar segment during resting and leg raise positions. Significantly less PA displacement (P<0.05) was seen in lower compared to upper lumbar spine and in leg raise compared to rest at L1 to L4. No significant interaction of sex with different lumbar levels and conditions (P>0.05) during PIT was found. Although previous studies have reported that the lower lumbar spine had greater mobility, the lower amount of displacement during the rest position suggests the role of an active subsystem contributing to lumbar stability regardless of sex. A reduction in displacement during the leg raise position across L1 to L4 suggesting an interaction of stabilizing subsystems of the spine to provide lumbar stability.

Meta-Material Layout for the Blast Protection of Above-Ground Steel Pipes

The current study investigates the capacity of the proposed meta-material layout for the blast protection of above-ground steel pipes against explosions. The philosophy of the meta-material layout’s design is described adequately, and the 1D periodic structures’ theory is adopted for the analytical prediction of the layout’s band-gaps. The special characteristics of the blast loading are explained, and specific time-related parameters are calculated. The layout is tested numerically for nine explosion scenarios of various magnitude via the finite element program ABAQUS, and the CONWEP model is selected for the simulation of the explosions. The results demonstrate a significant reduction in the maximum displacements developed on the pipe’s spring line and crown within a blast loading. This study composes an extension of the author’s previous research on buried steel pipes and surface explosion, advancing now the applicability of the meta-material layouts for the cases of above-ground steel pipes towards explosions and blast hazards. The outer goal is the investigation and the further spreading of the beneficial exploitation of meta-materials concepts for the scope of the pipelines’ effective blast protection, readdressing that this way is a major hazard for this type of structure and a gap in the current literature.

The elasticity distribution of under-band based on pressure comfort and breast support performance for seamless sports bras

Seamless knitted sports bra is becoming popular for its high performance in tactility and pressure comfort, however, it also encounters the problem of insufficient support. To improve the support performance, it is always knitted with strong elastic material in a reduced size than the body dimension, which will generate much pressure on the body, leading to discomfort. As the pressure distribution may affect the pressure comfort and support performance of the sports bra, this study aimed to explore novel information in optimizing the pressure comfort and support performance by applying elasticity distribution. 4 sports bras with different elasticity distribution on the under-band were developed to compare with the one without elasticity distribution, and 12 healthy women were involved as subjects. The pressure distribution and pressure comfort sensations both in static and dynamic conditions, and the reduction of breast displacement (RBD) of 5 sports bras were measured and analysed by ANOVA analysis. The results indicated that the pressure distribution, the pressure comfort and RBD were effectively changed by elasticity distribution. Bra D with a high Young’s modulus on the side area of the under-band was ideal and typical both in pressure comfort and RBD.

Study on the influences of the fractal dimension of the root system and slope degree on the slope stability

The problem of quantifying the effect of the alfalfa root morphology on the stability of the shallow surface layer of the slope of the Haizhou open-pit coal mine and the optimal slope degree in terms of the reinforcement of the shallow surface layer by the alfalfa root system was addressed. In this study, the mechanical parameters of plain soil and alfalfa root–soil composite samples were measured by indoor soil tests and triaxial compression tests, and a calculation model for the slope of the Haizhou open-pit coal mine was established in FLAC3D numerical simulation software to analyze the influence of the alfalfa root system on the maximum displacement of the shallow surface layer of the slope and the relationship with the fractal dimension of the alfalfa root system. The fractal dimension was applied to quantify the influence of the alfalfa root morphology to further investigate the relationship between the fractal dimension of the root system and the optimal slope of the shallow surface layer. The analysis showed that the fractal dimension of the alfalfa root system varied at different slope degrees, i.e., 40° > flat > 30° > 50°; the maximum soil displacement of the shallow surface layer of the slope increased with slope in nonlinear increments. Analysis of the fractal dimension of the alfalfa root system and the maximum displacement reduction rate at the different slope degrees revealed that the optimal slope degree of the shallow surface layer reinforced by alfalfa varied between 30° and 40°. The study results could provide a basis for further explaining the nature of the role of the alfalfa root morphology in reinforcing shallow surface soil and the optimal slope degree of the slope of the Haizhou open-pit coal mine reinforced by alfalfa roots.

Effects of a short period of postural training on postural stability and vestibulospinal reflexes.

The effects of postural training on postural stability and vestibulospinal reflexes (VSRs) were investigated in normal subjects. A period (23 minutes) of repeated episodes (n = 10, 50 seconds) of unipedal stance elicited a progressive reduction of the area covered by centre of pressure (CoP) displacement, of average CoP displacement along the X and Y axes and of CoP velocity observed in this challenging postural task. All these changes were correlated to each other with the only exception of those in X and Y CoP displacement. Moreover, they were larger in the subjects showing higher initial instability in unipedal stance, suggesting that they were triggered by the modulation of sensory afferents signalling body sway. No changes in bipedal stance occurred soon and 1 hour after this period of postural training, while a reduction of CoP displacement was apparent after 24 hours, possibly due to a beneficial effect of overnight sleep on postural learning. The same period of postural training also reduced the CoP displacement elicited by electrical vestibular stimulation (EVS) along the X axis up to 24 hours following the training end. No significant changes in postural parameters of bipedal stance and VSRs could be observed in control experiments where subjects were tested at identical time points without performing the postural training. Therefore, postural training led to a stricter control of CoP displacement, possibly acting through the cerebellum by enhancing feedforward mechanisms of postural stability and by depressing the VSR, the most important reflex mechanism involved in balance maintenance under challenging conditions.

A Low-Noise Micromachined Accelerometer with Reconfigurable Electrodes for Resonance Suppression.

We present a high-performance capacitive accelerometer with a sub-µg noise limit and 1.2 kHz bandwidth for particle acceleration detection applications. The low noise of the accelerometer is achieved through a combination of device design optimization and operation under vacuum to reduce the effects of air damping. Operation under vacuum, however, causes amplification of signals around the resonance region, potentially resulting in incapacitating it through saturation of interface electronics or nonlinearities and even damage. The device has thus been designed with two sets of electrodes for high and low electrostatic coupling efficiency. During normal operation, the open-loop device utilizes its high-sensitivity electrodes to provide the best resolution. When a strong signal near resonance is detected, the electrodes with low sensitivity are used for signal monitoring, while the high-sensitivity electrodes are used to apply feedback signals efficiently. A closed-loop electrostatic feedback control architecture is designed to counteract the large displacements of the proof mass near resonance frequency. Therefore, the ability to reconfigure electrodes lets the device be used in high-sensitivity or high-resiliency modes. Several experiments were conducted with DC and AC excitation at different frequencies to verify the effectiveness of the control strategy. The results showed a ten-fold reduction of displacement at resonance in the closed-loop arrangement compared to the open-loop system with a quality factor of 120.

Autonomous Respiratory Motion Compensated Robot for CT-Guided Abdominal Radiofrequency Ablations

Radiofrequency ablation (RFA) is an effective minimally-invasive treatment used for a variety of solid tumor cancers, including lung, breast, kidney, pancreatic, and liver. However, effective RFA for abdominal tumors relies on accurate ablation needle targeting, which can be a challenging task due to respiratory motion. This paper presents the design, fabrication, modeling, and benchtop characterization of a CT-guided parallel robot, and a novel respiration motion compensation protocol (RMCP) for effective robot-assisted abdominal RFA needle placement. The robot consists of a Stewart platform with a friction drive roller insertion module for autonomous needle deployment. Strain energy models are used to predict needle insertion force, the primary technical contribution of this work, providing a mean error of 0.49±0.28 N. The free-space accuracy characterization experiments indicate that the robotic platform is able to provide a needle tip position and orientation accuracy of 2.00±0.75 mm and 0.81±0.48±, respectively. A dynamic targeting experiment using an ex-vivo liver indicates an improvement in position and orientation error of 57% and 30%, respectively, when using the proposed RMCP. Finally, an animal study using a sexually-mature swine undergoing assisted respiration at nine breaths per minute indicates a 77% reduction in additional insertion displacement when using the RMCP.

Bending analysis of carbon nanotube coated–fiber multi-scale composite beams using the refined zigzag theory

The present work aims to investigate the bending analysis of sandwich and laminated carbon nanotube coated–fiber multi-scale composite (CFMC) beams employing the Refined Zigzag Theory (RZT). The model encompasses core fiber, surrounding carbon nanotube (CNT) coating region, and polymer matrix covering all scales from nano to macro-scale. Hierarchical multi-scale modeling is utilized where information is only transmitted from the fine-scale to the next coarser scale. The CNT coating region (CCR) consists of CNT, matrix, and non-bonded interphase whose mechanical properties are determined employing the Eshelby–Mori–Tanaka method and the equivalent continuum fiber approach. Considering different configurations of grown CNTs around the core fiber, two CCRs are constructed, comprising axially aligned (ACCR) and randomly oriented CCRs (RNCCR). The mechanical properties of the core fiber coated with the surrounding CCR are then obtained through the composite cylinder assemblage (CCA) method. Consequently, four RZT kinematic variables are acquired for the CFMC beams, and the effects of CNT volume fraction, coating thickness, and coating types are thoroughly investigated for various laminated and sandwich beams. The results reveal a substantial reduction in the maximum transverse displacements of the CFMC beams compared to the conventional composite beams, considering the low volume fraction of the CNTs in the coating region. Moreover, by employing a combination of ACCR and RNCCR for the layers in the sandwich CFMC beams, a pronounced decline in the transverse shear stress of the core medium is demonstrated, which can postpone the core shear failure in the sandwich structures. A great agreement is observed between the obtained results and the outcomes predicted by finite element analysis.

Investigation on behavior of anchored sheet pile quay wall improved by cement-soil: Centrifuge and numerical modelling

By using the centrifuge test and three-dimensional (3-D) finite element (FE) simulation with an advanced soil constitutive model, this study investigated the suitability and reinforcement effect of cement deep mixing (CDM) for stabilizing the anchored sheet pile quay (ASPQ) in soft clay. Besides, a parametric study was designed to analyse the influence of three factors, including the excavation depth ratio, the slenderness ratio and the strength of the CDM block, on the responses of quay wall and quay-surface settlement. The results showed that the effectiveness of CDM was closely related to its strength, slenderness ratio, and excavation depth ratio. There existed a critical slenderness ratio of the CDM block to minimize the lateral deflection of the quay wall. The influence of CDM block strength on the response of the quay wall was significant only when it had low rigidity. As a result of material improvement, the reduction in maximum wall displacement became more significant as the excavation depth ratio increased. A CDM block-to-excavation-strength shape factor was proposed to characterise the lateral response of quay walls in cement-improved soil.

Nontraditional configuration of tuned liquid column damper inerter for base-isolated structures

In this paper, the concept of a novel passive control device, namely the Nontraditional Tuned Liquid Column Damper Inerter (NT-TLCDI), is investigated in combination with seismic base isolation (BI), to control lateral displacement demands in base-isolated structures during seismic events. The considered NT-TLCDI is a revision of the ordinary configuration of the recently proposed Tuned Liquid Column Damper Inerter (TLCDI). Unlike the traditional TLCDI layout, which involves a secondary liquid mass in a U-shaped tank coupled with a grounded inerter and connected to the isolation system by a spring-dashpot system, in the NT-TLCDI configuration, the damper is in parallel with the inerter rather than the spring. The optimal design, including the determination of the tuning frequency and damping ratios of the NT-TLCDI, is discussed with the purpose to reduce the base displacement variance of the BI system assuming a white noise base excitation. Under the optimal tuning condition, it is found that the proposed NT-TLCDI provides a larger suppression of vibration amplitude of the BI system than the traditional TLCDI in both the frequency domain and time domain. A more interesting aspect is the reduction of the device displacement achieved by the NT-TLCDI, which may be beneficial in practice when the space for housing the device is limited.

A Quantitative Method to Predict the Shear Yield Stress of Rock Joints

The shear mechanical properties of rock joints are crucial in assessing the stability and safety of rock structures, including slopes, rock dams, and tunnels. The yield stress serves as a pivotal point that distinguishes the linear and non-linear mechanical characteristics of rock joints. Due to its significance in risk monitoring and safety evaluation, this paper first provides an overview of the commonly employed methods for identifying the yield stress. Then, a novel displacement reduction method based on the displacement reduction coefficient is proposed and systemically examined. The comparison between the proposed method and existing methods based on shear experimental data suggests that the former is more adept at accurately determining the yield stress without subjective interference. Finally, this innovative method is employed to estimate the effects of external environmental factors on the yield stress of rock joints.

Analysis of the Feasibility of Immersive Virtualization in Technical Training

Goal: propose a method of training in regulatory standards using immersive virtualization, aiming at improving student knowledge retention compared to traditional online models.&#x0D; &#x0D; Theoretical Reference: use of literature through research on similar methods already applied in immersive training, dissertations, articles and national standards.&#x0D; &#x0D; Method: practical application of training in an immersive environment in two large industries located in the metropolitan region of Curitiba, PR, where the evaluated ones completed an evaluation questionnaire according to their degree of satisfaction, which is the main parameter used in this work to prove the efficiency of the method.&#x0D; &#x0D; Results and conclusion: the practical application of immersive training, compilation of data and analysis of results confirm the viability proposed in the method. As the country develops technologically, the method will have its applicability increasingly accessible and proven.&#x0D; &#x0D; Research implications: a method of technological training developed as an alternative to the current molds, will certainly bring great contributions to the academy, and, at the same time, with the reduction of machine downtime, displacements, logistical costs and agglomerations, this work will bring contributions to the industry.&#x0D; &#x0D; Originality/Value: with the advent of the covid-19 pandemic experienced in recent times, traditional methods of professional training needed to be quickly adapted, aiming to minimize the impact caused by the restriction of physical contact between people. The proposed method provides the possibility of maintaining professional training processes, offering society the possibility of being trained effectively.&#x0D;

Stability, Deformity and Fixation of the Floating Shoulder: A Cadaveric Biomechanical Study.

Floating shoulder injuries cause instability and deformity due to disruptions of the scapula, clavicle and superior shoulder suspensory complex (SSSC) ligaments. Resulting deformity of the glenopolar angle (GPA) has not previously been established, nor has the impact on stability and deformity when surgical fixation is performed. This study sought to quantify stability and deformity for multiple injury patterns, and the improvement to these parameters provided by clavicle and coracoclavicular (CC) ligament fixation. Fourteen cadaveric specimen upper extremities were used, which included the entire upper extremity, scapula, clavicle and cranial-most ribs. After being mounted upright, a scapular neck fracture was created, followed by either a midshaft clavicle fracture or sectioning of the acromioclavicular (AC) and coracoacromial (CA) ligaments. Subsequent sectioning of the other structure(s) followed by the CC ligaments was then performed. In all specimens the clavicle was then plated, followed by a CC ligament repair. At each step, a radiograph in the AP plane of the scapula was taken to measure GPA, and displacement of the glenoid fragment using radiopaque markers placed in the scapula. These radiographs were taken both unloaded and with a 100N applied medializing force. When evaluating deformity related to sectioning, the GPA was reduced when the CC ligaments were sectioned compared to an isolated scapula fracture (p=0.022) and compared to a combined scapula and clavicle fracture (p=0.037). For stability, displacement with a 100N force was significantly increased when the CC ligaments were sectioned compared to an isolated scapula fracture (p=0.027). In cases of an ipsilateral scapula neck and clavicle fracture with intact ligaments, fixation of the clavicle alone provided a statistically significant improvement in GPA (p=0.002); but not in reduction of displacement (p=0.061). In cases of an ipsilateral scapula neck and clavicle fracture with concomitant disruption of the CA, AC and CC ligaments, GPA was improved by clavicle fixation (p<0.001), and increasingly so by subsequent CC ligament repair (p<0.001). Displacement was also improved in these two states respectively (p<0.001, p=0.008). This biomechanical study confirmed the importance of the AC, CA and CC ligaments in conferring stability in SCCC injuries. Disruption of the CC ligaments created significant deformity of the GPA and instability with a medializing force. Clinical treatment should consider the integrity of these ligaments and their repair in conjunction with clavicle fixation, knowing that this combination should restore a biomechanical state equivalent to an isolated scapula fracture.

Optimal design of negative-stiffness dampers for improved efficiency of structural seismic isolation

Over the past two decades, negative-stiffness devices have attracted increasing interest in the community of structural vibration isolation and control. They are typically used in combination with supplemental damping devices, and the combined systems are often referred to as negative-stiffness dampers (NSDs). Different types of NSDs have been developed and studied using both theoretical and experimental methods. However, comprehensive comparative studies between optimally designed NSDs for improving the efficiency of structural seismic isolation are inadequate. In this paper, three types of NSDs, i.e., the negative-stiffness viscous damper (NSVD), negative-stiffness viscoelastic damper (NSVeD), and negative-stiffness inertoviscous damper (NSiVD) are considered and compared in terms of their efficiencies for structural seismic isolation. Analytical formulas are derived to calculate the optimal damping coefficients of the NSVeD and NSiVD to maximize the modal damping ratio, thus minimizing the peak transmissibility. Frequency- and time-domain responses of low-frequency structures separately equipped with the three types of NSDs are compared when they are designed to achieve equal modal damping ratios. Moreover, based on the derived analytical optimal formulas, a multi-objective minimization design method is presented to determine the optimal characteristic parameters of NSDs, and simultaneous reduction of isolator displacement and floor response acceleration of a benchmark base-isolated building structures under a suit of design-level ground motions is achieved. The results indicate that the three types of NSDs can be more effective than conventional viscous dampers in reducing floor response accelerations of base-isolated structures without compromising the isolator displacement, and the NSVeD has superior performance over the NSVD and NSiVD in terms of improved efficiency of structural seismic isolation.

Seismic Optimization for Hysteretic Damping-Tuned Mass Damper (HD-TMD) Subjected to White-Noise Excitation

The hysteretic damping tuned mass damper (HD-TMD) is composed of a spring element, a hysteretic damping (HD) element, and a mass. The HD force is proportional to the displacement of the tuned mass damper (TMD). Recently, the application of HD-TMD has emerged, but its optimal design is still lacking. To fill this academic gap, numerical solutions for optimal parameters of HD-TMD subjected to white-noise excitation were obtained based on the H2 optimization criterion. Performance balance optimization with a weighting factor was carried out to improve the response of a structure with the HD-TMD system. A set of earthquake records and harmonic excitations were conducted to prove the effectiveness of the optimal numerical solutions and the performance balance design. It was found that the performance of the HD-TMD is slightly better than that of the traditional optimized TMD. As a real TMD application of HD-TMD, the variable friction pendulum TMD (VFP-TMD) was selected to experience earthquakes with the proposed optimal methods. Results showed that the optimal solutions provided the best performance but raised the problem of difficulty in maintaining linearity with a large displacement. Nevertheless, the performance balance design helped reduce this defect and provided impressive seismic mitigation capacity. Compared with the optimal numerical solution results, the performance balance design demonstrated 2.847% of loss in the maximum structural displacement reduction rate and 3.709% of loss in the root mean square reduction rate during the earthquake-excited period, respectively.

Null-Space Minimization of Center of Gravity Displacementof a Redundant Aerial Manipulator

Displacements of the base during trajectory tracking are a common issue in the control of aerial manipulators. These are caused by reaction torques transferred to the base due to the manipulator motion and, in particular, to the motion of its center of gravity. We present a novel approach to reduce base displacements of a kinematically redundant aerial manipulator by using null-space projection in the inverse kinematic control. A secondary objective function minimizes the horizontal displacement of the manipulator center of gravity. We test this algorithm on different trajectories for both three and four degrees of freedom (DOF) manipulators in a simulation environment. The results comparing our algorithm with inverse kinematic control without the null-space projection show up to an 80% reduction in the end-effector position error and an average of about 56% reduction in maximum base displacement. The simulation implementation also runs faster than in real-time in our code implementation. We provide a workspace analysis based on multiple stopping criteria such as excessive base displacement, joint velocities and end-effector position error for the 3 and 4 DOF manipulators. As expected, the 4 DOF manipulator has a larger workspace.

Characterizing Structural Bearing Capacity and Deformation Behaviors of Micropiles under Multi-Stage Static Loading

This study investigates the structural bearing capacity and deformation behaviors of micropiles considering various influence factors including the length (L) of micropiles, outer diameter (d) and wall thickness (t) of steel pipes, diameter (r) and spacing (s) of grouting holes, and water cement ratio (w/c) of grout. Multi-stage axial compressive tests were performed on 20 micropiles to obtain their deformation behavior and axial compressive loads respectively corresponding to the cracking of surrounding grout (Pcr), yielding of steel pipes (Py), and global structural failure (Pult). Experimental results reveal that Pcr and Py are respectively 0.20–0.45 and 0.85–0.95 times Pult. In general, Pult decreases with L. Increasing d produces a more significant improvement in Pult compared to increasing t. The influences of r and s on Pult are associated with the weakening of stiffness and strength of the steel pipes. Micropiles with various w/c levels perform similar Pult, whereas their axial displacement at Pult increases with w/c. Under the same L or w/c condition, increasing d leads to an obvious reduction in the axial displacement at Pult. In the existing criteria, the performance of prediction equations for Pult and allowable axial compression load (Pc) was compared and evaluated. Furthermore, several empirical models were proposed to respectively predict Pult and Pc of the micropiles considering the influences of L, d, t, r, s, and w/c and achieve well predictions.

Seismic Analysis of Soft Storey Building in Earthquake Zones

In this paper (G+8) building is modeled like a bare frame, a bare frame with the shear wall, and a bare frame with X bracing by changing the soft storey to different floors. The static analysis effect is determined for all three models with zone IV and zone V using Staad pro-V8i software. The main objective of the research was to assess the impact of a soft storey in various earthquake zones and by varying places of the soft storey from first to the top floor and for frames with different column shapes by seismic analyses in staad pro. The results of variable building models are obtained from the research regarding various parameters such as displacement, storey drift, and base shear. More significantly, comparing different structural systems revealed a reduction in lateral displacement and story drift. The shear wall reduced the Storey Displacement by 98.838% and storey drift by 99.86%. The Steel bracing reduced the Storey Displacement by 97.846 % and storey drift by 92.6%. Finally, it has been found that the Shear wall reduces lateral displacement and storey drift, thus significantly contributing to greater structural stiffness. The analysis results recommended that the shear wall use reinforced concrete frames for the seismic hazard zones and the Steel bracing recommended for the low seismic zones.

Surgical Management of Unstable Superior Femoral Epiphysiolysis with Great Displacement

Introduction: Superior femoral epiphysiolysis (SFE) is a most progressive but sometimes abrupt displacement of the femoral head relative to the superior femoral metaphysis through the cervicocerebral growth plate of the femur. The displacement of the femoral head is most often downward and backward. It is a typical pathology of the pubescent adolescent, most often overweight. It occurs on average at the age of 12 years in girls and 14 years in boys. Unstable forms with large displacements have a high risk of femoral head necrosis and chondrolysis. Although in situ fixation is the generally accepted treatment for minor SFE, the treatment of more severe cases remains controversial. When the extent of the displacement makes it impossible to pass a screw between the femoral neck and the femoral head, the only option is to reduce the displacement. This reduction must be gentle, progressive and limited to the minimum necessary for osteosynthesis. Objective: The aim of the work was to evaluate the results of the technique of progressive reduction of epiphyseal displacement by transtibial traction followed by percutaneous fixation of the femoral head by screw. Patients and Method: This was a retrospective descriptive study over a 10-years period from January 1, 2013 to December 31, 2022. It focused on the surgical treatment of unstable upper femoral epiphysiolysis with large displacement in the orthopaedic trauma department of the University Hospital of Kati. All patients operated on in our department for large displacement SFE were included in this study. Cases of secondary large displacement upper femoral epiphysiolysis and patients who had already undergone surgery on the proximal femur were excluded. Continuous progressive traction on the Boppe splint through a pin under the anterior tibial tuberosity was performed for 15 days in all patients. The hip was flexed to 45° and the knee to 35°. Fixation was performed with one or two screws. No contralateral preventive fixation was performed. Minimum follow-up was one year. Functional outcome was assessed by the Postel Merle d’Aubigné score. Anatomical outcome was assessed by the quality of reduction, the occurrence or non-occurrence of femoral head necrosis, and chondrolysis. Results: We identified nine patients with a mean age of 12.8 years and extremes of 9 and 17 years. There were three boys and six girls. Trauma was mentioned in four cases. The cause was idiopathic in five cases. Functional impotence was complete in all patients. The slippage was acute on a chronic background in all patients. The left side was affected in 7 cases and the right side in 2 cases. The patients were overweight in 7 cases. The patient’s weight was within the normal range in two cases. At final follow-up, all nine patients were asymptomatic. Anatomically, all nine patients had a femoral head free of avascular necrosis. In eight patients, the posterior tilt was absent, identical to that obtained after the traction period. Only one patient had a moderate posterior tilt with a neck uncovering of less than 25%. Functionally, the PMA score was very good in eight cases and good in one case. Conclusion: This study shows that the treatment of acute and unstable forms of upper femoral epiphysiolysis by progressive reduction with transtibial traction can lead to satisfactory results. Reduction in large displacement forms should be gentle, progressive and limited to the minimum necessary for osteosynthesis. Magnetic resonance imaging examination is an essential and indispensable prognostic element. Indications for preventive fixation should be selectively reserved for specific cases.