Initial Tension Research Articles

Study on Thin Lamination of Carbon Fiber Based on Mechanical Broadening.

Carbon fiber has excellent mechanical properties and plays an important role in modern industry. However, due to the complexity of the carbon fiber widening process, the industrial application of carbon fiber is limited. By designing the carbon fiber widening equipment of automaton, the relationship between the widening width of carbon fiber and the process parameters is studied, and the optimum developing process parameters are obtained, to improve the performance of carbon fiber composites to a certain extent. In this study, the widening process of carbon fiber was studied based on the mechanical broadening method. Firstly, an automatic broadening equipment was designed, and the effects of the initial tension, the number of straight rods, the number of convex rods, and the drawing speed on the widened width during the broadening process were discussed. The widening effect was evaluated by SEM imaging and mechanical testing. At the same time, the factors affecting the broadening width and broadening defects during the broadening process were analyzed, and the optimal broadening process parameters were obtained. The results showed that within a specific range, a higher initial tension, a greater number of convex rods, and an appropriate speed resulted in relatively smaller damage to the broadening of carbon fibers. Through the design of automatic broadening, this experiment explores optimal broadening process parameters, provides a reference for the improvement of the carbon fiber broadening process and further promotes large-scale industrial applications of carbon fiber.

Numerical investigation of the effect of bubble properties on the linear resonance frequency shift due to inter-bubble interactions in ultrasonically excited lipid coated microbubbles

Ultrasonically excited microbubbles (MBs) have numerous applications in various fields, such as drug delivery, and imaging. Ultrasonically excited MBs are known to be nonlinear oscillators that generate secondary acoustic emissions in the media when excited by a primary ultrasound wave. The propagation of acoustic waves in the liquid is limited to the speed of sound, resulting in each MB receiving the primary and secondary waves at different times depending on their distance from the ultrasound source and the distance between MBs. These delays are referred to as primary and secondary delays, respectively. A previous study demonstrated that the inclusion of secondary delays in a model describing the interactions between MBs exposed to ultrasound results in an increase in the linear resonance frequency of MBs as they approach each other. This work investigates the impact of various MB properties on the change in linear resonance frequency resulting from changes in inter-bubble distances. The effects of shell properties, including the initial surface tension, surface dilatational viscosity of the shell monolayer, elastic compression modulus of the shell, and the initial radius of the MBs, are examined. MB size is a significant factor influencing the rate of linear resonance frequency increase with increasing concentration. Moreover, it is found that the shell properties of MBs play a negligible role in the rate of change in linear resonance frequency of MBs as the inter-bubble distances change.The findings of this study have implications for various applications of MBs in the biomedical field. By understanding the impact of inter-bubble distances and shell properties on the linear resonance frequency of MBs, the utilization of MBs in applications reliant on their resonant behavior can be optimized.

Determining the rational structure of multilayer technical fabric for woven power clamps

The object of research is multi-layered technical fabrics for woven power clamps. A task to determine the rational structure of a multi-layer technical fabric for power clamps has been solved, which makes it possible to achieve an effect when introduced into production through the minimization of raw material costs and the reduction of energy costs for manufacturing a unit of products. The value of the beating force, the tension of warp threads of the outer protective layers, the force layers, the warp threads for connecting the outer protective layers, and the force layers for two structures of multilayer technical fabric were studied. A comparative analysis of conditions for the formation of two multilayer fabrics from polyamide threads was carried out and a multilayer fabric with the most rational structure was selected, the formation of which would require less technological effort. Experimental studies have made it possible to build regression dependences on determining the influence of the initial tension of warp threads of the outer protective layers on the beating force value. The joint effect of the size of an overstep and the different tension of a shed on the beating force value was established, depending on the structure of a multilayer technical fabric. It is shown that when the tension of warp threads of the outer protective layers increases, the beating force value increases. A value of the tension of warp threads in outer protective layers, force layers, warp threads for connecting the outer protective layers and force layers in the position of an overstep and at the moment of thread beating was determined. Analysis of regression dependences will make it possible to determine the optimal loading parameters of the loom. It has been proven that the beating force value is affected by the structure of a multi-layer technical fabric and the tension of warp threads in outer protective layers. The improved multi-layer technical fabric is used for laying pipes with an external factory-made polyethylene coating

Number of intra-operative cyclic knee motion required to achieve stable graft tension in anterior cruciate ligament reconstruction; a prospective clinical study.

Applying pretension by cyclic knee motion immediately before graft fixation in anterior cruciate ligament (ACL) reconstruction surgery decreases graft elongation during the postoperative course. However, the expected change in graft tension caused by cyclic knee motion remains unclear. We measured graft tension changes caused by cyclic knee motion during double-bundle ACL reconstruction. We included 39 patients undergoing primary anatomical double-bundle ACL reconstruction with autologous hamstrings as graft sources, at multiple centers between February 2021 and August 2022. After securing the anteromedial (AM) and posterolateral (PL) bundle grafts to the femoral cortex, they were initially tensioned to 40 N per bundle. After 10 cycles of knee extension and flexion motion, ranging from 0 to 90-110°, tension was re-measured and re-tensioned to 40 N if the graft tension had decreased. This was repeated thrice for 10 cycles on each graft. Every 10 cycles, we recorded graft tension changes (ΔGT) and compared the mean ΔGT in the AM and PL bundles. Furthermore, we assessed relationships between total ΔGT in each bundle, age, sex, and graft diameter. Twenty-five women and 14 men with a mean age of 27.4 ± 12.4 years were included. The mean ΔGT in AM and PL bundles after every 10 cycles were 6.6 ± 3.7 N, 3.0 ± 2.3 N, 1.4 ± 1.5 N, and 9.9 ± 3.8 N, 4.9 ± 2.6 N, and 2.5 ± 1.9 N, respectively. There were significant differences in ΔGT in both bundles after every 10 cycles (p < 0.01). ΔGT in the AM bundle was significantly lower than in the PM bundle at the same number of cycles (p < 0.01). No correlation was observed between ΔGT in either bundle and age, sex, or graft diameter. The initially applied graft tension decreased by intra-operative cyclic knee movement, and the changes in graft tension decreased after retention and repeated cycles. Three sets of 10 cycles knee motion may avoid initial tension loss of the hamstring autograft in the early phase after double-bundle ACL reconstruction.

Rock anchor hanger effect on single-tower earth-anchored suspension bridge mechanical performance: An analytical model and multi-objective golden eagle optimization

The application of a composite saddle in single-tower earth-anchored suspension bridges (STEASBs) replaces the tower on the steep slope side, which is a cost-effective solution that improves bridge safety and provides environmental protection for the steep bank slope of the valley. However, this novel bridge design needs an appropriate model to evaluate the effect of rock anchor hangers on the structure in the non-girder area and adjust their parameters to optimize the mechanical response of the whole bridge structure. This study proposes an approach to quickly evaluate the most unfavorable load cases of the STEASB and further optimizes the structural parameters of rock anchor hangers to enhance structural safety. An analytical model for the STEASBs under the live load is proposed and verified by the finite element model (FEM), with the maximum relative error not exceeding 7.37%. Combined with the golden eagle optimizer (GEO), the most unfavorable load cases of the corresponding design indices are yielded. The Pareto optimal solutions for the spacing, cross-sectional area, and initial tension of the vertical rock anchor hangers are obtained through multi-objective optimization to improve the mechanical behavior of STEASBs. In addition, it is clarified that the main function of rock anchor hangers is to reduce the peak value of the stress amplitude of the hangers and girder-end rotation, providing a theoretical basis for the STEASB design.

Seismic resilience mechanism of self‐centering dual‐limb thin‐walled rocking piers with replaceable energy dissipation beams

AbstractThis paper presents an innovative self‐centering dual‐limb thin‐walled rocking pier with replaceable energy dissipation beams (DLTW‐REDB), combining self‐centering hybrid system concepts with DLTW bridge piers. It addresses the issue of DLTW piers being prone to damage in the longitudinal direction during strong earthquakes, enabling rapid post‐earthquake recovery. The study focuses on the following aspects: (1) A 1:5 scale quasistatic reversed cyclic test was conducted to assess the seismic performance of the system. The results demonstrated that the hybrid system exhibited a characteristic “flag‐shaped” hysteretic response, similar to traditional rocking bridge piers. It exhibited excellent energy dissipation and self‐centering capability. Moreover, plastic damage primarily occurred in the replaceable energy dissipation beam, which could be easily replaced within 2 h while restoring the original structural behavior. (2) The self‐centering mechanism of the system was analyzed based on principles of structural mechanics, explicitly deriving the hysteresis, and residual deformation expressions. A quantitative index, the self‐centering coefficient (λ), was established to measure the self‐centering capability. (3) Numerical models were employed to analyze the sensitivity of parameters such as the prestressed reinforcement ratio, initial tension in prestressing tendons, and yield force of the energy dissipation beam. The results suggested that raising the initial tension enhanced the bearing force and reduced the residual displacement. However, raising the yield force improved the bearing capacity and energy dissipation capability, while residual displacement increased. Therefore, it is recommended to set the self‐centering coefficient at approximately 1.0 to achieve a trade‐off between effective energy dissipation capacity and acceptable residual deformation.

Characterization of droplet impact dynamics onto a stationary solid torus

The impingement mechanism of a liquid droplet on a solid torus surface is demonstrated using numerical simulations and an analytical approach. A computational model employing the volume of fluid method is developed to conduct simulations for the present investigation. Several influencing parameters, namely, diameter ratio (Dt/Do), contact angle (θ), initial droplet velocity (described by Weber number, We), surface tension (specified by Bond number, Bo), and viscosity of liquid drop (described by Ohnesorge number, Oh) are employed to characterize the impacting dynamics of a water drop onto a stationary toroidal substrate. The pattern of temporal and maximum deformation factors is elaborated by considering various relevant influencing factors to describe the fluidic behavior of the drop impingement mechanism. The key findings indicate that the developed central film gets ruptured at the early stage when the value of Dt/Do is lower because a relatively thin film is developed. Concomitantly, the very tiny drops get pinched off at Dt/Do= 0.83, whereas the detached drops are relatively large-sized in the case of lower Dt/Do= 0.16 due to the higher drainage rate of liquid mass through the hole at lower Dt/Do. It is also revealed that the first pinch-off is found to be faster with the continual upsurge of We for a specific value of Dt/Do and θ. Aside from that, efforts are made to show a scattered regime map in order to differentiate the pattern of droplet configuration during impingement. We have also attempted to establish a correlation that effectively characterizes the maximum deformation factor, which closely matches with the numerical findings. The developed correlation exhibits a firm agreement with the numerical data within deviations of 8.5%. Finally, an analytical framework is formulated to predict the deformations factor, which closely agrees with the computational findings.

Initial tension at suture fixation affects the suture breakage following medial meniscus posterior root repair: A retrospective cohort study

ObjectivesThis study aimed to investigate whether the initial suture tension when pullout sutures are fixed affects postoperative clinical outcomes following medial meniscus posterior root repair. MethodsThe data of 48 patients who underwent transtibial pullout repair using two simple stitches (outer and inner sutures) with an additional all-inside posteromedial pullout were retrospectively investigated. The patients were sequentially divided into two groups to compare the clinical efficacy of the initial pullout tension (N) when pullout sutures were fixed: the 30 N Group (April 2019 to September 2019, 24 patients) and the 15 N group (October 2019 to February 2020, 24 patients). The rate of suture breakage (suture cutout or rupture) at the second-look arthroscopy at 1 year postoperatively and clinical outcomes at 2 years postoperatively were compared between the two groups. ResultsIn both groups, each clinical score significantly improved at 2 years postoperatively. At the second-look arthroscopy, the rate of posteromedial suture breakage was significantly higher in the 30 N group (19 patients, 79 ​%) than in the 15 N group (10 patients, 42 ​%); the rate of outer suture breakage was also higher in the 30 N group (five patients, 21 ​%) than in the 15 N group (no patients). On comparing 2 years of preoperative clinical scores between the groups categorized according to posteromedial suture breakage, the pain score was significantly higher in the suture breakage group. ConclusionsThe initial tension of pullout repair of the medial meniscus posterior root tear is related to suture breakages. To prevent suture breakage, 15 N is a more initially suitable condition than 30 N. Level of evidenceLevel III.

Optimization of resting tension for wire myography in male rat pulmonary arteries.

Wire myography to test vasomotor functions of blood vessels ex-vivo are well-established for the systemic circulation, however, there is no consensus on protocols for pulmonary arteries. We created a standardized wire myography protocol for healthy rat PAs and validated this in a pulmonary hypertension (PH) model. Vessels stretched to higher initial tensions (5.0, 7.5 and 10.0 mN) exhibited a uniform response to phenylephrine, a larger dynamic range, and lower EC50 values. The endothelium-mediated relaxation showed that moderate tensions (7.5 and 10.0 mN) produced robust responses with higher maximum relaxation and lower EC50 values. For endothelium independent responses, the higher initial tension groups had lower and more consistent EC50 values than the lower initial tension groups. Pulmonary arteries from rats with PH were more responsive to vasoactive drugs when subjected to a higher initial tension. Notably, vessels in the PH group subjected to 15.0 mN exhibited high dynamic ranges in contractile and relaxation responses without tearing. Lastly, we observed attenuated cholinergic responses in these vessels-consistent with endothelial dysfunction in PH. Therefore, a moderate initial tension of 7.5-10.0 mN is optimal for healthy rat pulmonary arteries and a higher initial tension of 15.0 mN is optimal for pulmonary arteries from animals with PH.

Dynamics and frequency response analysis of encapsulated microbubble under nonlinear ultrasound

Bubble dynamic behavior and frequency response of encapsulated microbubbles in nonlinear acoustic field is significant in applications such as tumor therapy, thrombolysis, tissue destruction, and ultrasonic lithotripsy. The acoustic cavitation effect includes stable cavitation and transient cavitation. The transformation from stable cavitation to transient cavitation requires a certain threshold, which is also called the transient cavitation threshold. Phospholipid-coated microbubbles are commonly used to enhance acoustic cavitation. However, the acoustic effects of different coating materials are not very clear, especially when considering the nonlinear effects caused by diffraction, scattering, and reflection during ultrasonic propagation. In this paper, the bubble dynamic behaviors and frequency responses of microbubbles under different frequencies, acoustic pressures, and viscoelastic properties of different shell materials are analyzed by coupling the Gilmore-Akulichev-Zener model with the nonlinear model of a lipid envelope and using the KZK equation to simulate the nonlinear acoustic field. At the same time, the influence of the coated material and nonlinear acoustic effects are considered. The bubble dynamic behavior and frequency response under the actually measured sound field are compared with those simulated by the KZK equation. The results show that the nonlinearity will lead the velocity of the microbubble wall to decrease, and when the pressure of ultrasound increases, the main frequency component of the microbubble oscillation increases, making the radial motion of the microbubble more violent. When the frequency changes, the closer the oscillation frequency of the microbubble is to the resonant frequency, the stronger the radial motion of the microbubble is. The coating material can change the harmonic component in the oscillation frequency. When the harmonic is close to the resonance frequency, the radial motion of the microbubble is enhanced. The elasticity of the coated material has almost no effect on the microbubble's frequency response, and the initial viscosity and surface tension of encapsulated microbubble will change the oscillation frequency distribution of encapsulated microbubble. When the initial viscosity of the coated microbubble is smaller, the subharmonic component of the microbubble oscillation increases. When the frequency of the subharmonic is closer to the resonance frequency than the main frequency, the acoustic cavitation effect is significantly enhanced. On the other hand, when the initial surface tension of the encapsulated microbubble increases, the main frequency and subharmonic component of the microbubble oscillation are enhanced, so that the acoustic cavitation effect is also enhanced. Therefore, this study can further elucidate the bubble dynamics of encapsulated microbubbles, stimulated by nonlinear ultrasound, benefiting the frequency response analysis of coated microbubbles under nonlinear acoustic fields.

Short-term strength adaptation in isometric training to volitional failure depends on initial specific tension in elbow flexors

Short-term strength adaptation in isometric training to volitional failure depends on initial specific tension in elbow flexors

Interference screw versus suture button fixation for tibialis anterior tendon transfer: a biomechanical analysis.

Tibialis anterior tendon (TAT) transfer to the lateral cuneiform is commonly utilized to treat dynamic supination for relapsed clubfoot deformity. Traditional suture button fixation (SBF) may lead to skin necrosis at the button/skin interface. While interference screw fixation (ISF) would mitigate this concern, this fixation method has not been investigated in clubfoot patients. This study aims to investigate the performance of ISF versus SBF for TAT transfer in a cadaveric model. Ten matched pairs of cadaveric feet were obtained. One of each matched specimen underwent TAT transfer to the lateral cuneiform using ISF and the other underwent TAT transfer using SBF. For each ISF specimen, the tension of the transferred TAT required to bring the ankle to neutral was measured. This tension was then applied to both matched specimens using an MTS machine. Tension dissipation was measured after a 20-minute interval. In specimens with SBF, a load cell was positioned between the plantar skin and suture button to determine plantar skin pressure at the time of initial tension application. Average tension necessary to achieve neutral dorsiflexion was 49.4 N. Average tension dissipation after 20 min was significantly less in the IFS group (20 N versus 23.6 N, P = 0.02). No fixation failures occurred in either group. Average plantar foot skin pressure was 196.5 mmHg at initial tension application, exceeding thresholds for tissue ischemia. ISF allows for tendon tensioning at forces beyond those expected to result in skin necrosis with SBF with less dissipation of tension over time.

A spatial stability theory of thin-walled steel beams pre-stressed by spatially inclined un-bonded cables and its FE formulation

A spatial stability theory of mono-symmetric thin-walled steel beams pre-stressed (PS) by spatially inclined cables is firstly derived using an energy method where it is assumed that deviators are rigid. Its FE formulation is then presented under bonded/un-bonded multi-deviator conditions. After that, validity and accuracy of the present formulation is demonstrated through numerical examples. Finally, effects of initial tension, deviator numbers, inclined cable profiles, and un-bonded/bonded conditions on lateral-torsional buckling (LTB) of the PS bi-/mono-symmetric beams are investigated under external loadings. Particularly, new findings on LTB characteristics of the PS beams are presented with a specific emphasis on the effects of increasing initial tension.

Postoperative quadriceps weakness and male sex are risk factors for patellofemoral articular cartilage lesions after anatomical anterior cruciate ligament reconstruction

PurposePatellofemoral (PF) compartment cartilage lesions are a frequent problem after anterior cruciate ligament (ACL) reconstruction. This study aimed to determine the factors that influence PF cartilage lesions after anatomical ACL reconstruction.MethodsThis study enrolled a total of 114 patients who did not manifest PF compartment cartilage lesions during anatomical ACL reconstruction and underwent second-look arthroscopy 18 months postoperatively. Arthroscopy using the International Cartilage Repair Society (ICRS) classification was used to assess cartilage lesions. The correlation between surgical findings, radiographic factors, and clinical factors and change of ICRS grade was analysed. Multivariate regression analysis was conducted to reveal the independent risk factors for PF cartilage lesions among patients’ demographic data and parameters that correlated with the change of ICRS grade in the correlation analyses.ResultsICRS grade changes in PF cartilage were significantly correlated with age, sex, quadriceps strength at 1 year postoperatively, hamstrings strength at pre- and 1 year postoperatively, and single leg hop test at 1 year postoperatively. However, no significant correlation was found between the time between injury and surgery, posterior tibial slope angle, pre- and postoperative Tegner activity scale, graft type, initial graft tension, meniscus injury, meniscus injury treatment, pre- and postoperative range of motion, anteroposterior laxity and preoperative quadriceps strength, and the change in ICRS grade. Multivariate regression analysis revealed male (P = 0.019) and quadriceps strength weakness at 1 year postoperatively (P = 0.009) as independent risk factors for PF cartilage lesions.ConclusionsQuadriceps strength weakness 1 year after ACL reconstruction and males were correlated with a new PF cartilage lesion after anatomical ACL reconstruction, with no significant correlation between bone-patellar tendon-bone autograft, initial graft tension, or extension deficit and new PF cartilage lesion. Rehabilitation that focuses on quadriceps strength after ACL reconstruction is recommended to prevent new PF cartilage lesions.Level of evidenceLevel IV.

Historical aspect of international mediation and current trends in its development

The article «Historical aspect of international mediation and modern trends of its development» explores the evolution and role of international mediation throughout history and analyzes the current trends of its development in the modern world. The article examines the role of mediation in conflict resolution in different eras, starting from ancient civilizations to the present. Particular attention is paid to key stages in the development of international mediation, such as the Renaissance, the 19th and 20th centuries, and modernity, with a focus on the influence of international organizations and technological innovations. Current trends are also analyzed, including the expansion of actors, the use of modern technology, the increasing role of regional organizations, and cultural sensitivity. The article emphasizes that contemporary international mediation is becoming a more complex and multidimensional phenomenon, playing an important role in conflict resolution and maintaining stability on the world stage.&#x0D; The article considers international mediation as one of the alternative ways of resolving legal conflicts. The historical aspect of the emergence of international mediation is analyzed, the main trends of its development are highlighted.&#x0D; The historical aspect of the development of international mediation and modern trends of its development reflect significant progress in the field of international conflict resolution. Since ancient times, people and groups have sought to use mediation to resolve disputes and prevent wars. In the modern world, international mediation has become an increasingly recognized and effective tool for conflict resolution and peacekeeping.&#x0D; Current trends in the institution of international mediation encompass a number of important aspects that reflect changes in world politics, technological advances, and cultural preferences.&#x0D; Here are the key ones:&#x0D; S As the role of various regional players, such as regional organizations, has strengthened, their influence on international mediation has grown. They are becoming important mediators of conflicts in their regions and can play a crucial role in maintaining stability.&#x0D; S Information and communication technologies are opening up new avenues for mediation, including virtual platforms and cyber-mediation. They facilitate the exchange of information and enable remote interaction between parties to a conflict.&#x0D; S In addition to States and international organizations, non-governmental organizations, academic institutions and private companies are increasingly involved in international mediation. Their expertise and neutrality can make a significant contribution to conflict resolution.&#x0D; S Modern mediators are increasingly paying attention to the cultural, religious and social dimensions of conflicts. Understanding local customs and values can contribute to effective mediation.&#x0D; S Mediation is increasingly linked to economic motives and measures to stimulate peace and cooperation. Economic support can be a means of encouraging constructive solutions.&#x0D; S An important aspect of current trends is the development of standards and ethics for mediators. Professionally trained and competent mediators contribute to successful conflict resolution.&#x0D; S Modern mediation increasingly focuses on conflict prevention and avoidance, as well as on rapid response to initial tensions.&#x0D; У Media and public opinion play an important role in creating an atmosphere of trust and support for successful mediation. Modern mediators are increasingly engaging with the public and using media platforms for communication and influence.&#x0D; The combination of these trends points to the evolution of the institution of international mediation towards a more flexible, integrated and adaptive system that can better meet the challenges of contemporary international conflicts.&#x0D; Current trends in the development of the institution of international mediation include the growing interest in the use of mediation in international disputes, the establishment of specialized international mediation centers and the development of professional standards for international mediators.

Configuration Evolution of a Particle Raft with a Preprepared Crack Driven by the Diffusion of a Surfactant.

In the present study, the morphology evolution of a particle raft with a preprepared crack, which is caused by injecting the surfactant sodium dodecyl sulfate (SDS) into water, is demonstrated. Experimental results on the process of crack closure and configuration evolution are captured and are in excellent agreement with the numerical simulations. Then a surface diffusion model on SDS is proposed to quantify the detailed physical scenario. The surface diffusion factor is determined through the shooting method based on the experimental result of dynamic surface tension. As a result, the analytical solution for the SDS concentration distribution is given. The theoretical result on the dependence relationship between the profile shrinkage ratio and the time variable is consistent with the experimental result. At last, the relation between the initial surface tension difference of SDS and the profile shrinkage ratio is obtained in the light of experiments and dimensional analysis, and the two results are very close. These analyses provide a comprehensive understanding of the coupling between chemicals and mechanical behaviors of soft matter, and the modulation of defects in the particle raft provides some inspiration for engineering new devices at the microscale.

Effects of Bolted-Joint Parameters on Axial Tension after Hydraulic Tightening

The axial tension remaining in a bolt after the hydraulic tightening is less than the initial tension from the hydraulic load, and the ratio of the residual tension to the initial tension, an effective tensile coefficient, is the most critical factor to securely tighten a pressure vessel. In this study, an analysis model simulating the hydraulic joint processes by using a finite element model was developed to clarify the effects of various joint parameters on the effective tensile coefficient. The analysis model could estimate the effective tensile coefficient within a 5% error compared to the hydraulic tightening experimental results. The simulated results of the analysis model showed that the effective tensile coefficient changed largely depending on the thickness and the surface pressure of the flange, and that the coefficient hardly changed by the height of the nut and the friction coefficient at the bearing surface.

LTB analysis of pre-stressed steel beams using mono-symmetric thin-walled beam and spatially inclined un-bonded cable elements

A FE procedure is proposed for spatial buckling analysis of thin-walled steel beams that are pre-stressed (PS) by spatially inclined cables. Here, the beams are simply supported, and their cross section can be bi/mono-symmetric. Also, the pre-stressing cables are connected to several deviators under bonded/un-bonded conditions. For lateral–torsional buckling (LTB) analysis of the PS beams, a thin-walled beam element for the steel beam and solid beam elements for the deviator members are firstly formulated using total potential energies. After that, the potential energies of two-node bonded and multi-node un-bonded cable elements are rigorously derived, and the corresponding elastic and geometric stiffness matrices are explicitly presented. Finally, the validity and accuracy of the present FE formulation are demonstrated through numerical examples, and a set of parametric studies is conducted to investigate the effects of initial tension, multi-deviators, vertical and lateral eccentricities, and flexible deviators on the LTB of the PS beams.

Research on Reasonable Construction Plan for Cast-in-Place UHPC Bridge Deck Plate of Cable-Stayed Bridge

This article takes a single-tower cable-stayed bridge with a steel-UHPC composite deck steel box girder as the research object and develops different casting plans for the UHPC layer on the bridge deck. It analyzes the influence of factors such as the block casting sequence of the UHPC layer on the bridge deck, whether or not to set up a post-casting section, whether or not to set up bridge deck counterweights and the range of it on the additional deformation and stress of the formed UHPC bridge deck during the construction stage, exploring the impact of various factors on the structural target bridge’s completion status (cable force, bridge completion linearity, bridge deck and steel box girder stress) under different pouring schemes. Research has shown that under the constant initial tension of stay cables, adjusting the pouring sequence of UHPC bridge decks and setting post-pouring sections is not significant in reducing the tensile stress of UHPC bridge decks. The more effective technical measure is to use bridge deck counterweight pouring during construction; the closer the counterweight is to the later stage constant load loading value, the more significant the decrease in UHPC tensile stress is. When factors such as on-site construction conditions, construction period, and labor costs are limited, local weight balancing on the bridge deck can be used.

Numerical study of the geometric characteristics and kinetic behavior of single bubble rise processes in different liquids

The characterization of single bubble in gas–liquid two phase flow is a critical yet unresolved issue in both science and industry. In this study, the volume-of-fluid (VOF) method is used to numerically simulate and experimentally investigate the effect of initial bubble diameter, liquid viscosity, and surface tension on bubble deformation and the internal flow field of the bubble in a pool of stationary liquid. The findings indicate that as liquid viscosity increases, the bubble's rising speed decreases, and the bubble tends to oscillate. The variation in bubble deformation ratio and the degree of fluctuation increase with the bubble's initial diameter and decrease with the viscosity of the liquid phase. Additionally, as the surface tension of the liquid decreases, the bubble becomes more prone to rupture, and the number of ruptures increases. The flow field inside the bubble can be classified into three categories: “double main vortex type,” “double main vortex type with separated vortex,” and “double main vortex type with scattered vortex.” The velocity reaches its maximum at the center of each vortex type, and the velocity at the interface varies as the bubble interface shape changes. This work lays the foundation for the study of the flow field inside the bubble and improves the predictability of gas–liquid equipment design.