Decrease In Force Research Articles

Loosening Phenomenon on Thin Plates Bolted Joint due to Offset Load

In this study, the new loosening behavior was discovered and investigated when offset loads were repeatedly applied to both ends of a bolted joint initially tightened to a thin plate made of high-tensile steel. In the experiments, the impact of offset distance on reduction of clamp force was investigated through multiple applications of symmetric offset axial load to the bolted joint assembly. The experimental results showed that even a slight offset load reduced the clamp force, and the larger the offset distance, the greater the reduction of the clamp force. It was also found that the decrease in clamp force depends not on the number of times the offset load is applied but on the magnitude of the offset load. Until now even if the thin plate bolted joint was subjected to an offset load, as long the plates do not deform significantly due to plastic deformation, it has been generally recognized that the clamp force is not reduced. This loosening phenomenon is new and its mechanism has not been elucidated yet. In order to clarify the mechanism that may lower the clamp force, this study conducted FE analysis using a simplified model of a bolted joint. In the FE model, the bolt and nut are considered as a single unit and the effect of slippage between the thread surfaces and the effect of plastic deformation is ignored by using elastic analysis. The results of the FE analysis showed that the main factor causing the reduction in clamp force was slippage between the thin plates to be joined, which was caused by offset load, and that the slippage didn't return to the original position resulting in the reduction in clamp force.

Analysis of the Impact of Population Ageing on China's Economy

Abstracts: This paper is based on the background of population aging in China's society and economy, in order to study how aging affects China's economy and how to cope with its impact. The paper is based on a literature survey and a case study approach to the topic of labor markets, the silver economy, and the consumption of the elderly population. The results of the study show that the labor force receives a larger ripple effect and that an increase in the aging population inevitably leads to a decrease in the labor force. The silver economy is a senior-centered economy driven by aging, and the aging of the population has increased the burden on society and the government. The Chinese government needs to introduce an appropriate security system for the aging population to facilitate the integration of the elderly into society and to guide the changes that need to be made in all sectors to cope with the aging of the population.

Neuromuscular Performance and the Intensity of External Training Load During the Preseason in National Collegiate Athletic Association Division I Men's Collegiate Basketball Players.

Curtis, M, Kupperman, N, Westbrook, J, Weltman, AL, Hart, J, and Hertel, J. Neuromuscular performance and the intensity of external training load during the preseason in National Collegiate Athletic Association Division I men's collegiate basketball players. J Strength Cond Res XX(X): 000-000, 2024-The aim of the study was to determine whether acute changes in neuromuscular performance can be detected through countermovement jumps (CMJs) conducted pre- and postpractice sessions in conditions of high or low intensity measured by microsensors technology. Using an observational repeated measures design, data were collected from 10 male collegiate basketball players. Countermovement jump data were collected before and after practice exposures over 4 weeks of preseason. Select CMJ kinetics were compared in conditions of high and low training load intensity to detect neuromuscular performance changes in displacement of the center of mass and kinetics. Kinetic measures were categorized as output, underpinning, and strategy-related variables. We investigated "output" defined as displacement (jump height [JH]), "underpinning" defined as force-related (mean eccentric force, mean concentric force, force at zero velocity), and "strategy" defined as time-related (countermovement depth [CMD], eccentric duration (EccDur), concentric duration [ConcDur]) variables. There were significant condition × time interactions in CMJ variables namely eccentric mean force (EccForce), force at zero velocity (Force@0), CMDepth, EccDur, and ConcDur. In conditions of high intensity, players had significant, but small decreases in EccForce and Force@0, with small increases in CMD, EccDur, and ConDur, respectively. However, there were no significant decreases in JH. High-intensity practice exposures did not impact neuromuscular performance specific to "output," suggesting that collegiate basketball athletes can maintain JH despite alterations in "underpinning" and "strategy-related" variables. This could have relevance in understanding how fatigue associated with higher-intensity training exposures may potentially alter jump strategy and force production capacities due to external load intensity in collegiate basketball athletes.

Investigation of Low Velocity Impact Behavior of Aluminum Honeycomb Sandwich Structures with GFRP Face Sheets by Finite Element Method

The aim of this study is to examine the low velocity impact behavior of aluminum honeycomb sandwich structures with glass fiber reinforced plastic (GFRP) face sheets with the help of finite element method. In the study, low velocity impact tests were carried out in the LS DYNA finite element program to examine the effects of face sheets thickness, core number, wall thickness, impact location and impact velocity on maximum contact force, absorbed energy efficiency and damage mode. Progressive damage analysis based on the Hashin damage criterion and the combination of Cohesive Zone Model (CZM) and the bilinear traction-separation law was performed using the MAT-54 material model. At the end of the study, it was determined that the face sheets thickness in sandwich structures had a significant effect on the impact resistance up to a certain impact energy. It has been observed that as the impact velocity gradually increases, there is a decrease in the contact force after a certain threshold value. As the impactor velocity increases, the energy absorption efficiency also increases. It has been determined that the location of the impact is very effective on peak force and energy absorption efficiency. The effect of the number of core layers depends on the face sheets thickness. When the face sheets thickness was not damaged at first contact, the peak force value increased in parallel with the number of layers. It was determined that the dominant damage mode after impact was matrix damage. It has been observed that as the energy level of the impactor increases, damage also occurs on the back surfaces.

Effect of fatigue on intermuscular EMG-EMG coupling during bench press exercise at 60% 1RM workload in males

ObjectiveTo explore the neuromuscular control mechanism and quantifying the fatigue response during bench press exercise is important references to prescribe an appropriate exercise program. However, current literature struggles to provide a concrete conclusion on the changes of intermuscular EMG-EMG coupling between synergistic and antagonist muscles during the exercise. Thus, the current study was designed to reveal fatigue-related changes of intermuscular EMG-EMG coupling during bench press exercise.MethodsThirty-one healthy male participants performed a bench press exercise on the Smith machine at 60% One Repetition Maximum (1RM) workload to exhaustion, while surface electromyographic signals (sEMG) were collected from triceps brachii (TB), biceps brachii (BB), anterior deltoid (AD), posterior deltoid (PD), and pectoralis major (PM). Surface EMG signals were divided into the first half and second half of the bench press exercise. Phase synchronization index (PSI) was calculated between sEMG of synergistic muscle pairs AD-TB, AD-PM and antagonist muscle pairs BB-TB, AD-PD.ResultsEMG power of TB, AD, PD, PM muscles in alpha (8–12 Hz) frequency band and EMG power of each muscle in beta (15–35 Hz), and gamma (35–60 Hz) frequency bands were all increased during the second half of contraction compared with the first half of contraction. PSI of gamma frequency band was significantly decreased in BB-TB muscle pair while EMG-EMG coupling of AD-TB in gamma frequency band was significantly increased during the second half of contraction compared to the first half of contraction.ConclusionsThe results indicated a decrease of interconnection between synchronized cortical neurons and the motoneuron pool of BB and TB, and an increase of interconnection between AD-TB muscles during fatiguing bench press exercise at 60% 1RM workload. The changes of intermuscular coupling may be related to the supraspinal modulations to compensate for the decrease of muscle force as well as a result of unbalanced changes of agonist and antagonist muscle contractility.

Numerical Investigation on the Hysteretic Performance of Self-Centering Precast Steel–Concrete Hybrid Frame

To improve the construction performance and seismic resilience of precast reinforced-concrete frame structures, an innovative self-centering precast steel–concrete hybrid frame has been proposed and subjected to cyclic loading tests. In this paper, a comprehensive numerical analysis was conducted to further investigate the frame’s hysteretic behavior. Initially, a numerical model was developed using the finite element software OpenSees. Numerical analyses of two frame specimens were conducted, demonstrating good agreement between the numerical and experimental hysteretic characteristics, thus validating the model’s accuracy. Subsequently, based on the numerical simulations, a quantitative comparison of hysteretic performance between a novel frame and a traditional reinforced-concrete frame of the same scale was performed. While the proposed frame exhibited slightly lower initial stiffness and energy dissipation capacity than the traditional frame, it outperformed in terms of load-carrying capacity and self-centering ability. Finally, parametric analyses were carried out to assess the influence of various design parameters on the hysteretic performance, including friction force in the web frictions devices, initial post-tensioned force of the prefabricated steel–concrete hybrid beams, the steel arm length, and the column longitudinal reinforcement ratio. The results showed that increases in these four parameters improved the load-carrying capacity and initial stiffness of the proposed frame. Additionally, an increase in the friction force, steel arm length, or column longitudinal reinforcement ratio enhanced the frame’s energy dissipation capacity, while an increase in the initial post-tensioned force or a decrease in the friction force enhanced the frame’s self-centering capacity.

Study on the Susceptibility of Steel Arches with Letting Pressure Nodes Based on Incremental Dynamic Analysis

When soft rock tunnels pass through fractured fault zones, they are particularly susceptible to extrusion and large-scale deformations, especially during seismic events. To address these challenges, this study introduces an innovative yield-support steel arch design featuring a circumferential letting pressure node at its core. This design delivers incremental support resistance within the deformation zone and a susceptibility curve is applied to evaluate the damage probability of the steel arch with a letting pressure node under seismic loading conditions. Measurements of the surrounding rock pressure and structural forces on the steel arch with the letting pressure node were conducted at the Baoshan Jewel Mountain Tunnel in China. The field experiment results revealed a 23% reduction in the surrounding rock pressure and an 11% decrease in the internal forces of the support structure. These findings demonstrate the successful application of the letting pressure node-supported steel arch in mitigating large deformations in soft rock environments. Additionally, using finite element software ANSYS 2022, a seismic time-history analysis was conducted, employing the relative deformation rate of the letting pressure node steel arch as the damage index and the peak ground acceleration (PGA) as the strength parameter to generate the incremental dynamic analysis (IDA) curve. According to the susceptibility curve derived from the incremental dynamic analysis, at the design ground motion level of 8 degrees, the letting pressure node steel arch has a 94% probability of exceeding its normal service life limit and experiencing damage. The findings of this study offer a novel approach to addressing large deformations in soft rock tunnels. The proposed susceptibility curves for steel arches with letting pressure nodes provide a robust foundation for predicting the damage probability of yielding support structures under seismic conditions.

A novel method for identifying rock interfaces and fragmentation zones based on drilling response characteristics

The rapid measurement and acquisition of the fracture characteristics and strength of the surrounding rock are crucial for evaluating the stability of underground engineering. In this study, a laboratory/coal mine universal drilling test platform was developed to enable real-time measurement of drilling parameters. The testing results demonstrate that under identical rotation speed conditions, both thrust force and torque increase exponentially with increasing drilling speed, while under identical drilling speed conditions, both thrust force and torque decrease linearly with increasing rotation speed. In intact rock layers, variations in torque, thrust force, and drilling speed with depth remain relatively stable, in rock layer interfaces and fragmentation zones, sudden changes occur within a drill displacement range of approximately 3–7 mm, which become more pronounced as strength differences between adjacent rock layers increase.Based on the cutting mechanics model of drill bit, the evaluation index of drilling energy consumption of unit rock mass (Eη) is derived. Subsequently, based on drilling speed, rotation speed, thrust force, torque and energy index, a machine learning model for predicting rock strength is established using the LS-SVM nonlinear regression approach. Field practice has shown that drilling platform can effectively identify both the rock interface and range of fragmentation areas. The experimental results are of great value to the selection of supporting types in the process of coal mine roadway excavation.

Insights into vibration-induced softening effect: A thermodynamic approach

This work investigates the wear behavior of nickel-based alloy during ultrasonic vibration-assisted machining (UVAM) by combining molecular dynamics simulation and thermodynamic theory. The research reveals that the tangential force exhibits periodic variations during UVAM, with a period half of the vibration period. Tangential force and total resistance decrease due to the synergistic effect of vibration-induced softening and thermal softening. A deeper understanding of the total resistance variation during the UVAM process can be achieved by the dimensionless resistance coefficient, which is difficult for the traditional friction coefficient (CoF). The Bejan number elucidates the contributions of the thermal softening and vibration-induced softening effects in the wear process. The findings highlight that the vibration-induced softening effect dominates when adjusting the amplitude for the active control of friction. In contrast, when the frequency is modulated, the contributions of vibration-induced softening and thermal softening effects are nearly equivalent. Furthermore, the wear mode transitions with increasing vibration frequency, characterized by the Strouhal number (Srw). The vibration wear mode attains dominance when Srw > 1.88. This work provides essential theoretical guidance to gain insight into the wear behavior in UVAM to optimize the machining performance.

Investigation on the material removal mechanism in ion implantation-assisted elliptical vibration cutting of hard and brittle material

Ductile-regime machining has been used to generate damage-free surface of hard and brittle materials by setting the cutting depth to be smaller than the ductile-brittle transition depth (DBTD). However, the ductile-regime cutting of sapphire remains challenging owing to its extreme hardness, small DBTD, serious surface fractures, and severe tool wear. To solve this problem, ion implantation-assisted elliptical vibration cutting (Ii-EVC) has been proposed in this study to enhance the machinability of hard and brittle materials. Taking sapphire as an example, high-energy phosphorus ions were implanted into the workpiece to modify its surface. Nanoindentation tests revealed that the modified materials undergo plastic and elastic deformation more easily due to the decrease in hardness and modulus. Compared with nanocutting without implantation assistance, the DBTD of implanted sapphire has been increased by more than five times. The advantageous effects of Ii-EVC achieve great enhancement in machinability, including surface fractures suppression, tool-wear reduction, chips morphology transformation from discontinuous to continuous, and cutting force decrease. Furthermore, even near the cracks in the brittle region after Ii-EVC, the subsurface microstructure showed a more complete lattice arrangement and a strain distribution close to zero, indicating that crack propagation was effectively suppressed. Due to the promoted localized plastic deformation, the stress distribution in the implanted material is much smaller than that in pristine workpiece. Implantation-induced defects not only serve as a core for absorbing external energy from the high-frequency vibration and improving the in-grain deformation but also facilitate the formation of shear bands. The interface with high distortion between the modified layer and substrate can effectively dissipate strain energy and hinder crack propagation to the free surface. The turning experiments verified that Ii-EVC can achieve better surface quality, less tool wear and higher optical transmittance. Overall, Ii-EVC addresses the challenges of tool breakage and surface fracture caused by high-frequency collision between tool and workpiece in traditional EVC, overcomes the problem of limited modification depth in ion implantation, and increases the ductile-regime removal depth of extremely hard and brittle materials to several microns. Such findings demonstrate that Ii-EVC is a promising method for the ultra-precision manufacturing of advanced materials.

Acute effects of local vibration inducing tonic vibration reflex or illusion of movement on maximal wrist force production.

Local vibration (LV) mainly stimulates primary afferents (Ia) and can induce a tonic vibration reflex (TVR) and an illusion of movement. This study aimed to evaluate the effect of these two phenomena on maximal voluntary isometric contraction (MVIC) capacity. LV (80 Hz) was applied to the wrist flexor muscles in two randomized experiments for 6 min. LV conditions were adjusted to promote either TVR (visual focus on the vibrated wrist) or ILLUSION [hand hidden, visual focus on electromyographic activity of the flexor carpi radialis muscle (FCR)]. Mechanical and electromyographic (EMG) responses of the FCR and extensor carpi radialis muscles were recorded during MVIC in flexion and extension and during electrically evoked contractions at supramaximal intensity. Measurements were performed before (10 min and just before) and after (0 and 30 min) LV protocol. An increase in FCR EMG was observed during LV in the TVR condition (+340%) compared with the illusion condition (P = 0.003). In contrast, the movement illusion was greater in the ILLUSION condition (assessed through subjective scales) (P = 0.004). MVIC was reduced in flexion only after the TVR condition ([Formula: see text], all P < 0.034). Moreover, the decrease in force was correlated with the amount of TVR recorded on the FCR muscle (r = -0.64, P = 0.005). Although potentiated doublets of each muscle did not evolve differently between conditions, a decrease was observed between the first and the last measure. In conclusion, when conducting research to assess maximal strength, it is necessary to have better control and reporting of the phenomena induced during LV.NEW & NOTEWORTHY The maximal force production of the vibrated muscle is reduced after 6 min of LV only in TVR condition. Furthermore, the amount of TVR is negatively correlated with this force decrease. When measuring the effects of LV on maximal force production, it is important to control and report any phenomena induced during vibration, such as TVR or movement illusion, which can be achieved by recording EMG activity of vibrated muscle and quantifying illusion.

Effects of wind barriers on the aerodynamic forces and driving safety of vehicles on a wide bridge girder at various angles of attack

This paper presents the effects of angles of attack (AOA) on the windproof effect of wind barriers and the driving safety of highway vehicles on a wide bridge girder. The aerodynamic force coefficients of the vehicles were obtained using the force measurement technique. Computational fluid dynamics simulations were employed to investigate the mean wind velocity field on the upper surface of the girder. A comparison was made between the aerodynamic forces on a vehicle at various AOA on a bridge deck with guardrails and a deck with wind barriers. The windproof effect of wind barriers at various AOA was accessed by the safety factor of a vehicle. The results showed that the maximum of the aerodynamic forces of vehicles was not typically observed at a 0° AOA. The windproof effect of wind barriers became more pronounced as the magnitude of the AOA increased. As AOA increases, the height of the low wind velocity zone above the deck shows an upward trend. Compared to the deck with the guardrails, the height of the low wind velocity zone was much higher in the presence of wind barriers. The increase in the height of the low wind velocity zone will result in a decrease in the aerodynamic side force and an increase in the rolling moment acting on vehicles. It is also noteworthy that the installation of wind barriers can cause a reduction of overturning and side-slip safety factors of vehicles at specific AOA. This suggests that the wind barrier may potentially compromise driving safety at specific AOA.

Dynamics of a droplet on the surfactant-infested free surface of another liquid

The dynamics of liquid droplets surfing over the surfactant-infested free surface of another liquid have been explored experimentally. We analyze the motion of oil droplets that has been initiated through the creation of a surface tension gradient resulting from the deposition of a drop of surfactant at the water surface contained in the petri dish. The experiments reveal that the location of surfactant deposition with respect to the droplet position influences its motion. Due to the presence of a surface tension gradient, the footprint area of the droplet reduces and its shape changes. We have studied the temporal variation in the velocity (|vx|) of the droplets in relation to their proximity to a wall. Based on the evolution of droplet shape and change in droplet velocity, the drop dynamics can be experimentally divided into four distinct zones. Results indicate that in zone-1, |vx| grows with t as |vx|≈tn, where n is between 0.8 and 1.0. The scaling argument shows that in this zone, the surface tension force dominates the drag force, and thereby, |vx| of the droplets increases linearly with t expressed as |vx|∝t. The experimental investigation and the scaling law exhibit a reasonable agreement. In zone-2, |vx| remains more or less constant, as it is postulated that the surface tension force balances the drag force. In zone-3, a decrease in surface tension force results in a deceleration of the droplets. In zone-4, the deceleration becomes more prominent as the droplet approaches the petri dish wall.

Rehabilitation of steel structures using innovative brace members equipped with YSPD damper

Earthquakes are serious risks to human life and infrastructure. An earthquake's influence on human life and its socioeconomic consequences highlight the need to investigate and create the most efficient and easily adaptable ways to minimize losses. The basic concept of different control mechanisms used for protecting structures from the destructive impacts of earthquakes is to dissipate the energy efficiently, therefore ensuring that the structure remains undamaged or sustains minimum damage. To achieve this purpose, the passive control mechanism is a particularly suitable and reliable technology as it doesn't rely on external power to actively dissipate energy. The present study proposes using a passive energy dissipation device called the Yielding Shear Panel Device (YSPD) for strengthening the current steel structures. The YSPD consists of a square hollow section (SHS) that houses a diaphragm plate. The fundamental concept of the YSPD involves harnessing the lateral deformation of a steel plate to absorb and disperse the seismic energy. The Bouc-Wen-Baber Noori (BWBN) material has been used for simulating the hysteresis force-deformation relationship of YSPDs by pinching. YSPDs are simulated as spring components that connect between the beam and the V-brace. A nonlinear time history dynamic analysis was performed to assess the alteration in the structural capacity with the setting up of YSPDs. The performance of the tested structure was assessed considering story drift, story displacement, story shear, column shear, and YSPD hysteresis loops. The results indicated that YSPD installation has improved the structure's capacity. However, the use of dampers resulted in significant drift in all stories, a reduction in total floor displacement, and a decrease in the shear force of the stories. However, the results demonstrated that the YSPD dampers effectively absorbed energy and exhibited stable hysteresis loops.

A Critical Analysis on the Low Birth Rate Problem and the Effectiveness of Relevant Policy

This paper discusses the importance of the birth rate problem and the effectiveness of Chinas Three-Child policy. In order to efficiently elaborate problems, this paper analyses the issue from several perspectives. Firstly, a declining birth rate will have a negative impact on the global and domestic economic development due to the decrease in labour force. Secondly, this paper suggests that the key reason for this declining birth rate is the rising economic pressure on young people. This paper finds that China, Japan, and South Korea face the same low birth rate problem. Hence, this paper investigates the different wage levels and house prices among these East Asian countries and elaborates on the relationship associated with declining birth rates. Furthermore, this paper also discusses how to ensure the successful implementation of the Three-Child policy, and what effect the social welfare and the Three-Child policy can bring to help the society and the economy.

Posterior Glenoid Bone Grafting in the Setting of Excessive Glenoid Retroversion Does Not Provide Adequate Stability in a Cadaveric Posterior Instability Model

Background: Excessive glenoid retroversion is a known risk factor for posterior shoulder instability and failure after soft tissue stabilization procedures. Whether excessive glenoid retroversion is a risk factor for failure after posterior glenoid bone grafting is unknown. Purpose: To evaluate the biomechanical effectiveness of posterior iliac crest bone grafting (ICBG) for posterior shoulder instability with increasing glenoid retroversion. Study Design: Controlled laboratory study. Methods: Six fresh-frozen cadaveric shoulders had a posterior glenoid osteotomy allowing the glenoid retroversion to be set at 0°, 10°, and 20°. At these 3 preset angles, 4 conditions were simulated consecutively on the same specimen: (1) intact glenohumeral joint, (2) posterior Bankart lesion, (3) 20% posterior glenoid bone defect, and (4) posterior ICBG. Stability was evaluated in the jerk position (60° of glenohumeral anteflexion, 60° of internal rotation) by measuring (A) posterior humeral head (HH) translation (in mm) and (B) peak translational force (in N) necessary for translation of the HH over 25% of glenoid width. Results: At 0° of retroversion, the ICBG restored posterior HH translation and peak translational force to values comparable with those of the intact condition (P = .649 and P = .979, respectively). At 10° of retroversion, the ICBG restored the peak translational force to a value comparable with that of the intact condition (22.3 vs 24.7 N, respectively; P = .418) but showed a significant difference in posterior HH translation in comparison to the intact condition (4.5 vs 2.0 mm, respectively; P = .026). There was a significant increase in posterior HH translation and significant decrease in peak translational force with the ICBG at 20° of glenoid retroversion compared with the intact condition (posterior HH translation: 7.9 vs 2.0 mm, respectively; P < .006; peak translational force: 15.3 vs 24.7 N, respectively; P = .014). Conclusion: In this cadaveric study, posterior ICBG was able to restore stability to a level comparable to that of the native condition at 0° and to some extent at 10° of retroversion. However, posterior ICBG was not able to provide adequate stability at 20° of glenoid retroversion. Clinical Relevance: Posterior glenoid bone grafting with ICBG should be used with caution when performed in isolation in the setting of posterior instability associated with glenoid bone loss and combined glenoid retroversion of >10°.

The peeling behavior of film/substrate systems with periodic and discontinuous bonding

Discontinuous bonding is a common adhesion state in multilayer structures within the shipbuilding, automotive, and semiconductor industries, as well as in biological adhesion. Based on the cohesive theory and the Euler-Bernoulli beam model, we investigate the peeling behavior of a film from the rigid substrate subjected to periodic and discontinuous bonding. Different from the continuous bonding model, the peeling force during the peeling process exhibits repeated fluctuations. The increase and decrease of peeling force correspond respectively to the initiation of cohesive zones within the non-bonded and bonded segments. Furthermore, the bonding state at the crack tip influences the change pace of the energy release rate. Specifically, when the cohesive zone initiates within a bonded segment, the decrease in the energy release rate accelerates noticeably as the crack tip enters a non-bonded segment. Additionally, the influence of diverse bonding ratios and varying periodic lengths is discussed. This paper provides insights into the peeling behavior under discontinuous bonding effects in nature, and offers potential applications for the optimization and design of multilayer structures.

Automatic evaluation of progressive collapse performance of braced frames

Braced frames are among the most effective systems for resisting progressive collapse; however, determining the optimal bracing system remains challenging. Evaluating different bracing systems in this study was simplified using VBA programming tools and a flowchart that complied with the Unified Facilities Criteria (UFC)regulations (chapter 5). Applying control processes and automated VBA programming tools was beneficial for examining plastic hinges and guaranteeing adherence to the Unified Facilities Criteria (UFC)Design Strategies for Preventing Progressive Collapse in Building Structures.The study examined several types of braced frames, such as CBF and EBF, and found that the inverted V-braced systems (CBF and EBF) were the most efficient. They reduced the amount of vertical movement and dispersed the stresses on the remaining linked parts. Although there was a substantial vertical displacement, all beams and columns showed a decrease in overall force. The absence of a bracing system in the frame led to a violation of the regulatory criteria outlined in the control flowchart. The remaining structural systems exhibited exceptional performance.

Grouting sleeve/bird’s nest anchor cable anchoring capacity characteristics and numerical simulation study

With the deepening of coal mining resources, the safety issues of broken soft coal seams become increasingly prominent, severely affecting the safety of deep mining operations and workers. Traditional anchoring methods alone are ineffective in achieving secure anchorage. Therefore, the grouting anchor cable composite structure is explored to address the safety of roadway excavation in deep broken soft coal seams. Indoor grouting anchorage tests and pull-out tests for grouted anchorages are conducted to study their bearing characteristics and failure mechanisms. Discrete element numerical simulation methods are employed to verify the findings from indoor tests. Research indicates that the ultimate pull-out forces at grouting pressures of 0.5, 1.0, 1.5, and 2.0 MPa are 87, 104, 118, and 131 kN, respectively. The pull-out force of the grouted anchorage is positively correlated with the grouting pressure. At the loading end, shear stress and axial force reach their maximum values of 1.8 MPa and 106 kN, respectively, under 2.0 MPa grouting pressure. The distribution patterns of shear stress and axial force decrease gradually with increasing anchoring depth. Microscopic analysis reveals that the failure of the anchor body model is primarily due to the tensile cracks formed by the particle flow code in two dimensions. This finding is consistent with the failure mode observed in indoor tests, which involves the slip and debonding failure of the anchor cable. Crack evolution is categorized into three stages: initiation, continuous propagation, and anchor failure. As the inter-particle contact forces within the anchor body model decrease, the region of chain fracture expands. These results provide technical support for understanding the bearing characteristics of grouting anchor cable composite structures.

Dedifferentiation- and aging-induced loss of mechanical contractility and polarity in vascular smooth muscle cells: Heterogeneous changes in macroscopic and microscopic behavior of cells in serial passage culture

Dedifferentiation and aging of vascular smooth muscle cells (VSMCs) are associated with serious vascular diseases, such as arteriosclerosis and aneurysm. However, how cell dedifferentiation and aging affect cellular mechanical behaviors at the single-cell and intracellular structure levels remains unclear. An in-depth understanding of these interactions is extremely important for understanding the mechanism underlying VSMC mechanical integrity and homeostatic regulation of vascular walls. Herein, we systematically investigated changes in VSMC morphology, structure, contractility, and motility during dedifferentiation and aging induced by serial passage culture using traction force microscopy with elastic micropillar substrates, laser nanodissection of cytoskeletons, confocal fluorescence microscopy, and atomic force microscopy. We found that VSMC dedifferentiation started in the middle stage of serial passage culture, accompanied by a transient cell spreading in the cell width and decrease in contractile protein expression. Dedifferentiated VSMCs showed a significant decrease in the contraction and stiffness of individual actin stress fibers; however, their overall cell traction forces were maintained. Simultaneously, a significant increase in cell motility and the number of actin fibers was observed in dedifferentiated VSMCs, which may be associated with the enhancement of cell migration and disruption of cell/tissue integrity during the early stage of vascular diseases. As cell senescence progressed in the later stage of serial passage culture, VSMCs displayed reduced cell spreading and migration with decrease in the overall cell traction forces and drastic reduction in mechanical polarity of cell structures and forces. These results suggested that cell senescence causes loss of mechanical contractility and polarity in VSMCs, which may be an important factor in vascular disease progression. The experimental systems established in this study can be powerful tools for understanding the mechanisms underlying cellular dedifferentiation and aging from a biomechanical perspective.