Force Transfer Research Articles

Moving morphable components structural optimum approach considering wire arc additive manufacturing constraint and its application in satellite

The thin-walled reinforced structure is important for achieving structural lightweight in spacecraft. With the rapid development of additive manufacturing technology, large-size, thin-walled, stiffened structures with complex structural forms can be manufactured. However, topology optimization considering manufacturing constraints has always been difficult in this field. This paper proposes a design method for reinforced structures that enables control over structural connectivity based on the Moving Morphable Components (MMC) method, which uses reinforced components with explicit geometrical parameters as primitives for topology optimization. The proposed method solves the challenges of rapidly designing complex geometric reinforcements, forming clear force transfer paths, and effectively reduces the structural topology optimization challenges caused by process constraints associated with the arc start/quench process of wire arc additive manufacturing (WAAM). This method was used to design a core load-bearing structure of a large satellite, i.e., the 3.5-meter tank supporting structure, which was fabricated by the WAAM process for the first time in the spacecraft field. The structure passed the mechanical test and eventually achieved a weight reduction of 31.6%.

Load introduction to composite columns revisited—Significance of force allocation and shear connection stiffness

The AISC 360-16 Specification recommends that the design shear force between parts of a composite column in the load introduction area shall be calculated based on the force allocation at ultimate limit state. Applicability of this straightforward method to the load levels that usually arise in slender composite columns is questionable, as this capacity-based force allocation is only true when the axial force is equal to the plastic resistance of the composite cross-section. Next, the number of required shear connectors is calculated as a quotient of the design shear force and the strength of a single shear connector. We demonstrate that: first, for the lower load levels, the stiffness-based force allocation gives a more accurate estimate of the shear force; second, the number of shear connectors satisfying the strength requirement can lead to insufficient force transfer between parts of the composite cross-section. To investigate the shear transfer mechanism in composite columns, we derive an analytical model with linear elastic constitutive relations both for steel and concrete and three types of shear force slip laws: elastic, elastic plastic, and rigid plastic. The case studies carried out for different shear transfer scenarios demonstrate the importance of the shear connection stiffness on the effectiveness of the load introduction. The remaining portion of the shear force is transferred outside the load introduction area, which hampers the column’s ability to withstand shearing from varying bending moments or incipient buckling. To control the shear force transfer efficiency by enhancing the shear connection stiffness, we propose an original Stiffness Method and provide design charts as an aid in the design process.

Load introduction and transfer mechanism of K-type CFST circular section connections

This paper investigates the mechanism of load introduction and transfers for K-type concrete-filled steel tubular (CFST) circular section connections experimentally and numerically. Six K-type CFST connections were tested. Three-dimensional finite element (FE) models were then developed and validated against the test results, where the degradation and failure of the direct bond interaction were considered explicitly. The longitudinal strain distribution along the circumferential direction of chord-wall demonstrated that the non-uniform force transfer in the chord was caused by the one side load introduction through braces. The effects of the chord length, cross-sectional slenderness and interfacial interactions on the force transfer of tube-concrete interface were evaluated: 1) the chord length above the connecting region has a positive influence on the force transfer; 2) for the K-type CFST connections in this study, the material strength of concrete in the chord with non-compact and slender sections could not be fully utilized due to the insufficient force transfer; 3) the direct shear interaction dominated the force-transferring process from chord-wall to concrete for the compact section chord with reinforcing plates. Furthermore, the test and FE result confirmed that the load introduction length of the CFST chord with braces included the chord above the connecting region and the full connecting region. In addition, the equation of effective load introduction length for the CFST chord of the K-type connections was proposed.

Experimental analysis on the out-of-plane structural performance of single-face superposed shear walls with different horizontal connections

Single-face superposed (SFS) shear wall is a novel precast concrete sandwich panel (PCSP) wall that can be used as load-bearing walls in high-rise buildings and underground structures in seismic zones. This paper investigates the out-of-plane structural performance of SFS shear walls with different horizontal connections. Three SFS shear walls with different lap-spliced rebar connection configurations at the horizontal connections were designed and tested to compare their out-of-plane structural performance with that of a cast-in-place specimen, in terms of failure modes, cracking patterns, load-displacement curves, stiffness degradation curves, ductility, and force transfer mechanism of lap-spliced rebar connections. The test results showed that the SFS shear wall specimens exhibited and maintained a high level of composite action until failure, and the studied three different horizontal connections can allow effective force transfer between the upper shear walls and the lower. The stiffness, ductility, and ultimate bearing capacities of SFS shear walls under out-of-plane monotonic loading were significantly higher than those of cast-in-place shear walls. The bearing capacity was found to depend to a large extent on the location of additional vertical connecting rebar, the displacement mainly caused by rigid body rotation and related to crack width at joint. A calculation method of the ultimate bearing capacity of a SFS shear wall under out-of-plane horizontal loads was proposed. Finally, some suggestions on the setting of the vertical connecting bar are put forward.

Experimental tests of a modular composite frame corner for integral abutment bridges with sheet‐piling foundations

AbstractWith the increasing need to replace ageing bridge infrastructure, new concepts for sustainable constructions are needed. Ways to achieve this include material choice, concept design and the consideration of life‐cycle‐costs. Within the scope of FOSTA research project P1521, a concept will be derived for a modular frame corner for bridge spans up to 45 m. The load transfer of horizontal and vertical forces, as well as the bending moment of the frame corner, are analyzed in experimental tests and subsequent numerical studies.To determine the bending resistance, load paths and critical details of the connection, the node is split into an upper and lower part, connecting the main girder and the sheet‐piles respectively to the abutment. Composite dowels with high fatigue resistance are used to transfer both forces and moments through a newly designed shear connection. This article looks at the results of 4 static tests from the upper‐part series as well as numerical studies.The results of both experimental as well as numerical models shows a high load bearing capacity of the connection with the composite dowels contributing positively to the constraining of the main girder. The concept shows promising results for future application.

Analysis of the Impact of the Ribbon Track on Unconventional Fixing on a Steel Multi‐Span Bridge

AbstractThe presented analysis deals with the influence of ribbon rail track on its unconventional fixing on a steel multi‐span bridge. Specially adapted stiffeners for the transfer of horizontal forces from the track to the superstructure are used in such cases. Local defects created over the years point out the overstressing of the fixing stiffeners to the combined response of the structure and the track. Subsequently, there is an adverse effect on the continuous ribbon track and the speed or pass‐ability of the bridge can be significantly limited.Numerical analyses are confronted with in‐situ experimental measurements realized at the 450 m long 14‐span‐bridge within an international railway line. Experimental measurements were focused mainly on influence of temperature and breaking/accelerating forces. The results showed a significant impact of temperature effects on the rails leading into unexpected longitudinal displacements and unwanted stresses in the analyzed details of the track fixation. A global model and local sub‐models in two FEM software were elaborated to analyze real behavior in a theoretical way.Researchers from the university and the R&D staff of the state railway administrator's institute collaborated in this research within the mutual long‐term cooperation.

Classification of Urban Agricultural Functional Regions and Their Carbon Effects at the County Level in the Pearl River Delta, China

Exploring the transformation process of urban agricultural functions and its interaction with carbon effects based on regional differences is of great positive significance for achieving a low-carbon sustainable development of agriculture in metropolitan areas. By using the index system method, self-organizing feature maps (SOFM) network modeling, and Granger causality analysis, we divided the agricultural regional types of the Pearl River Delta (PRD) based on the spatio-temporal changes in urban agricultural functions and carbon effects at the county level in the PRD from 2002 to 2020, and analyzed the carbon effects generated by the agricultural functions according to the differences between the three agricultural regional types. The results show the following: (1) The changes in the basic functions of agriculture, the intermediate functions of agriculture, and the advanced functions of agriculture were different from the perspectives of both time and space. (2) The carbon effects produced by the areas with weak agricultural functions, the areas with medium agricultural functions, and the areas with strong agricultural functions were different. (3) The evolution of agricultural production types aggravated the grain risk in the PRD, and urban agriculture has potential in improving food security. (4) Based on the regional types of agricultural functions and considering the constraints of land and water, strategic suggestions such as integrating natural resources, improving utilization efficiency, upgrading technical facilities, and avoiding production pollution are put forward. (5) The green and low-carbon transformation of urban agriculture has its boundaries. The positive effects of the factors, namely the innovation of agricultural production methods, the change in agricultural organization modes, the impact of market orientation, and the transfer of the agricultural labor force, is limited. The findings of this paper provide valuable and meaningful insights for academia, policy makers, producers, and ultimately for the local population in general, driving the development of urban agriculture in a low-carbon and sustainable direction.

Macroscale Collagen‐Actomyosin Hybrid Actuator Built from Bioderived Materials

AbstractBiological muscles mainly consist of motor proteins that play essential roles and have a hierarchical structure covered with collagen that can transmit the tension to bones via tendons. The artificial reconstruction of motor proteins is highly expected from the viewpoint of engineering and biology. Although artificial muscles have been developed via synthetic and biological molecular motors, there is a considerable gap between the components of artificial and biological muscles, resulting in a significant obstacle to further scale‐up and force transfer through macroscale structures. To overcome these obstacles via bioderived biomolecules, this study proposes a collagen‐actomyosin hybrid soft actuator inspired by the structure of biological muscles. Collagen gel entrapping actomyosin can play roles in maintaining the actuator's shape and transmitting the tensile force. The generated forces reach the micro‐newton range, enabling the actuation of millimeter‐scale mechanical components. These properties may be helpful for the fabrication of soft robotic systems with advanced functionalities.

Melting Heat Transfer Rheology in Bioconvection Cross Nanofluid Flow Confined by a Symmetrical Cylindrical Channel with Thermal Conductivity and Swimming Microbes

Nonlinear thermal transport of non-Newtonian polymer flows is an increasingly important area in materials engineering. Motivated by new developments in this area which entail more refined and more mathematical frameworks, the present analysis investigates the boundary-layer approximation and heat transfer persuaded by a symmetrical cylindrical surface positioned horizontally. To simulate thermal relaxation impacts, the bioconvection Cross nanofluid flow Buongiorno model is deployed. The study examines the magnetic field effect applied to the nanofluid using the heat generated, as well as the melting phenomenon. The nonlinear effect of thermosolutal buoyant forces is incorporated into the proposed model. The novel mathematical equations include thermophoresis and Brownian diffusion effects. Via robust transformation techniques, the primitive resulting partial equations for momentum, energy, concentration, and motile living microorganisms are rendered into nonlinear ordinary equations with convective boundary postulates. An explicit and efficient numerical solver procedure in the Mathematica 11.0 programming platform is developed to engage the nonlinear equations. The effects of multiple governing parameters on dimensionless fluid profiles is examined using plotted visuals and tables. Finally, outcomes related to the surface drag force, heat, and mass transfer coefficients for different influential parameters are presented using 3D visuals.

Influence of longitudinal prestress on the shear resistance of prefabricated shear stud connectors

In order to meet the requirements of accelerated bridge construction (ABC), the structure of steel–concrete composite bridges presents a development trend of the entire assembly. A Prefabricated Composite Shear Studs (PCSS) is proposed to speed up the assembly efficiency of traditional steel–concrete composite beams and improve the effectiveness of the prestress of prefabricated concrete decks in the negative moment zone. A finite element model (FEM) of the PCSS shear connector is established by considering the stress characteristics of different assemblies, thirty different steel tendon quantities, and relative arrangements are selected to analyse the impact of longitudinal prestress on the shear resistance of PCSS, the effectiveness of finite element model is verified this through test results. It is revealed that the steel tendon arrangement and quantity will change the shear resistance of the PCSS shear connectors. However, the magnitude, positive and negative effects are related to the position of the steel tendon along the deck height. When the steel tendon deviates downward from the neutral axis of the deck, the shear bearing capacity and shear stiffness increase; in addition, its force transfer mechanism is that the longitudinal prestress changes the lateral restraint effect of the PCSS on the concrete. Under the combined action of prestressing and transverse restraint of steel plate, the cooperative working ability of the stud and surrounding concrete can be enhanced or weakened. Thus, the yielding of stud and concrete damage can be delayed or accelerated, significantly affecting the shear bearing capacity and stiffness.

On topology design of compliant constant output/input force mechanisms with contact interactions

We seek monolithic topologies for constant output (CoFM) and input (CiFM) force mechanisms using topology optimization. We capture large displacements, buckling, contact interaction between members and external surfaces, and importantly, interaction of the mechanism with flexible workpieces to accurately simulate force transfer. Features of constant force characteristics, e.g., magnitude(s) of the desired force(s), range of input displacement over which slope of the force–displacement curve is near zero, and distance between workpiece and the mechanism are controlled individually. Two constant output and constant input force mechanisms each, are synthesized using stochastic optimization ensuring ready manufacturability. We observe that (a) accurate modeling of the mechanism-workpiece interaction is important. (b) Fixed external surfaces may not necessarily contribute to contact force characteristics though interesting alternative solutions are possible in their presence. (c) It behooves to model self contact between members than to reject viable solutions wherein members intersect in intermediate configurations. We finally fabricate the synthesized mechanisms and find that the desired constant force characteristics are by-and-large retained qualitatively, even when the mechanisms may undergo plastic deformation.

Inter-task transfer of force gains is facilitated by motor imagery.

There is compelling evidence that motor imagery (MI) contributes to improve muscle strength. While strong effects have been observed for finger muscles, only few experiments with moderate benefits were conducted within applied settings targeting large upper or lower limb muscles. The aim of the present study was therefore to extend the investigation of embedded MI practice designed to improve maximal voluntary strength on a multi-joint dynamic exercise involving the lower limbs. Additionally, we tested whether targeting the content of MI on another movement than that physically performed and involving the same body parts might promote inter-task transfer of strength gains. A total of 75 participants were randomly assigned into three groups who underwent a physical training on back squat. During inter-trial recovery periods, a first MI group (n = 25) mentally rehearsed the back squat, while a second MI group (n = 25) performed MI of a different movement involving the lower limbs (deadlift). Participants from the control group (n = 25) completed a neutral cognitive task during equivalent time. Strength and power gains were assessed ecologically using a velocity transducer device at 4 different time periods. Data first revealed that participants who engaged in MI of the back squat improved their back squat performance (p < 0.03 and p < 0.01, respectively), more than the control group (p < 0.05), hence supporting the positive effects of MI on strength. Data further supported the inter-task transfer of strength gains when MI targeted a movement that was not physically trained (p = 0.05). These findings provide experimental support for the use of MI during physical training sessions to improve and transfer force development.

Causes of Stiffness Degradation in Steel–UHPC Composite Beam-Bolted Connections

This groundbreaking study conducts the first-ever field push test on anchor bolts in steel–UHPC composite pavement in China, providing researchers with the opportunity to obtain the true mechanical performance of the anchor bolts after more than a decade of operation. As a result, the study comprehensively studies the long-term performance of anchor bolts in steel–UHPC composite pavement. The study established a finite element model of steel–UHPC pavement based on the mechanical properties of studs obtained from the field push-back tests, and the mechanical properties of studs were modeled by COMBIN39 and COMBIN14 elements. The reasons for the degradation of the bolt performance were analyzed by combining the anchorage force transfer model of the composite beam and the fatigue formula of the stiffness degradation of the bolt, based on the results of the finite element method. The study revealed that the stress of the anchor bolts gradually equilibrates along the longitudinal direction after prolonged service, with the end anchor bolts experiencing an offloading phenomenon and the middle span anchor bolts experiencing an increasing load phenomenon. Furthermore, the study identified the residual slip at the interface of the anchor bolt as a significant factor in the longitudinal stress redistribution of the anchor bolt, and construction errors further promoted stress redistribution. The study’s findings contribute to advancing the design and construction of steel–UHPC composite pavement. Additionally, the study proposes a novel approach to accurately evaluate the stiffness of pavements by combining the anchor bolt extrapolation test with a finite element model, with a maximum error of no more than 5 percent, which can be applied in future pavement design and construction.

Knockdown of TRPV2 inhibits the migration of RAW264.7 cells toward low fluid shear stress region.

Our previous studies have demonstrated that macrophages (RAW264.7) have a special ability for sensing the gradient of fluid shear stress (FSS) and migrate toward the low-FSS region. However, the molecular mechanism regulating this phenomenon is still unclear. In this study, we examined the transcriptome genes in RAW264.7 cells, MC3T3-E1 osteoblasts, mesenchymal stem cells, canine renal epithelial cells, and periodontal ligament cells. The expression levels of genes related to cell migration, force transfer, and force sensitivity in the Ca2+ signaling pathway were analyzed. We observed that the transient receptor potential cation channel type 2 (TRPV2) was highly expressed in RAW264.7 cells. Furthermore, we used lentiviral transfection to knockdown TRPV2 expression in RAW264.7 cells and studied the effect of TRPV2 on the migration of RAW264.7 cells under a gradient FSS field. The results showed that compared with normal cells, TRPV2-knockdown cells had impaired ability for sensing FSS gradient to migrate toward the low-FSS region and lower intracellular calcium response to FSS stimulation. This study may reveal the molecular mechanism of regulating the directional migration of macrophages under a gradient FSS field.

Relative contributions of the supraspinatus cord and strap tendons to shoulder abduction and translation

The supraspinatus (SS) is formed by a larger anterior bipennate muscle with a cord like tendon and a posterior unipennate muscle with a strap like tendon. There is a tendinous connection between the two SS subunits. Yet, the relative mechanical contribution of the SS cord and SS strap muscular tendinous units to load transmission and subsequent shoulder abduction force is unknown. We hypothesized that a simulated SS cord versus a SS strap tear will generate less shoulder abduction force; and further, an intact SS cord will offset the expected abduction loss from a SS strap tear, but the inverse will not be true. Twenty fresh-frozen cadaveric specimens were tested in a shoulder simulator with physiological load vectors applied to the upper and lower subscapularis, SS cord, SS strap, infraspinatus, and teres minor. The roles of the SS cord and SS strap muscles were delineated by varying their loads, while keeping constant loads on other muscles. The randomized testing trials included a Native condition and four test Cases which simulated tears by dropping the load and force transfer via the SS cord-to-SS strap connection by adding the load. Testing was completed at both 0° and 30° of abduction. During each test shoulder abduction force, rotator cuff strains and humeral translation were measured. Simulated isolated SS cord and SS strap tears lead to a significantly lower shoulder abduction force (p<0.001). A simulated cord tear at 0° and 30° reduced the abduction force by 53% and 38%, respectively. A simulated strap tear at 0° and 30° dropped the abduction force by 27% and 23%, respectively. The decline in abduction force was larger for the SS cord tear versus SS strap tear (p≤0.001). A SS cord tear with full load transfer to the strap was able to recover to native values at both 0° and 30° (p≥0.288). Likewise, a SS strap tear with full load transfer to the SS cord showed a similar recovery to native values at both 0° and 30° (p≥0.155). During full load transfer, the tendon strain followed the loading pattern. A SS cord tear or SS strap tear did not cause a change in humeral translation (p≥0.303). A mechanical findings support the efficacy of nonoperative treatment of small (<10mm) SS tears,11 because an intact SS strap tendon can effectively offset the abduction loss of a torn SS cord tear, and vice versa.

FATIGUE REAL SCALE TEST COMPARISON WITH ACTUAL BRIDGE MONITORING

In railway bridges, special attention needs to be paid to the interaction between the railway track and the bridge. Forces occur in the rails, as well as in the deck and the bearings of the bridge. These forces result in additional stresses, which need to be kept sufficiently low. Peak stresses due to e.g., temperature variations and bridge deck bending are especially to be feared at the bridge/abutment transition. Special rail fastening systems may be used to limit these additional stresses. Real scale tests were performed to verify the behavior of the track and the bridge equipped with such modified fasteners, which are designed to limit the transfer of longitudinal forces to the bridge. Based on the data from these tests, a detailed finite element model is constructed in this research paper. In contrast to the generally accepted modeling approach prescribed by international norms such as Eurocode NBN EN 1991-2 and UIC Code 774-3R, this research is performed, assuming the fact that the behavior due to track-bridge interaction can be simulated by a rail model supported by springs, i.e., without the need to model the actual bridge structure in detail. The results of these finite element model simulations are compared with data of a long-term monitoring program using strain gauges on all elements of the rails and support structure of an actual railway bridge in Belgium.

Institutional Forces and Transnational Transfer of Diversity Management

Institutional Forces and Transnational Transfer of Diversity Management

Effect of lower body, core and upper body kinematic chain exercise protocol on throwing performance among university shot put athletes: A pilot study

A coordinated sequence of movements is required to generate maximum power and velocity in shot put. Kinematic chains emphasize the interactions between various body segments during a movement. They suggest that force production and transfer are optimized by coordinating multiple joints and muscle groups. In previous research, the kinematic chain has been attributed to shot put performance. Few studies have examined the effects of a comprehensive kinematic chain exercise protocol on throwing performance among shot put athletes, particularly at universities. Pilot study investigating lower body, core, and upper body kinematic chain exercise protocol on university shot put athletes' throwing performance. A total of twenty-four young athletes specializing in shotput, with an average age of 19.87 years and a standard deviation of 1.31 years, were divided into two groups, namely the experimental group and the control group, using a random assignment method, the experimental group, consisting of 12 participants, underwent an 8-week kinematic chain training program alongside their regular training sessions. On the other hand, the control group, also consisting of 12 participants, only participated in their regular training sessions without any additional intervention. Pre- and post-training assessments were conducted to measure shotput throwing performance, preference for throwing style, and the participants' satisfaction with the exercise protocol, using a questionnaire. The athletes who took part in the kinematic chain program demonstrated a significant improvement in throwing distance compared to the control group (p = 0.01). Additionally, the athletes in the experimental group reported higher levels of satisfaction with the exercise protocol (p = 0.005). These findings indicate that incorporating an 8-week Lower Body, Core and Upper Body kinematic chain exercise protocol into regular training sessions can lead to more pronounced improvements in sport-specific throwing performance among young shotput athletes.

Thermal enhancement of nano-fluidic transport confined between disk and cone both rotating with distinct angular velocities and heat transfer

PurposeThis paper aims to study the fluid flow and heat transfer within the Casson nanofluid confined between disk and cone both rotating with distinct velocities. For a comprehensive investigation, two distinct nano-size particles, namely, silicon dioxide and silicon carbide, are submerged in ethanol taken as the base fluid.Design/methodology/approachThis paper explores the disk and cone contraption mostly encountered for viscosity measurement in various industrial applications such as lubrication industry, hydraulic brakes, pharmaceutical industry, petroleum and gas industry and chemical industry.FindingsIt is worth mentioning here that the radially varying temperature profile at the disk surface is taken into the account. The effect of prominent emerging parameters on velocity fields and temperature distribution are studied graphically, while bar graphs are drawn to examine the physical quantities of industrial interest such as surface drag force and heat transfer rate at disk and cone.Originality/valueTo the best of the authors’ knowledge, no study in literature exists that discusses the thermal enhancement of nano-fluidic transport confined between disk and cone both rotating with distinct angular velocities with heat transfer.

Shear force transfer efficiency of tapered bridges with trapezoidal corrugated steel webs

This study investigated the shear force transfer mechanism in a prestressed concrete (PC) tapered box girder bridge with trapezoidal corrugated steel webs (TCSWs) throughout the cantilever construction process by theoretical analysis, experimental verification, and finite element (FE) simulation. It has been determined that the assumption made in the current standards that TCSWs completely bear the shear force is inaccurate when designing tapered girders with TCSWs. The bending moment can cause a redistribution of shear force in a tapered case, which leads to the transfer of shear force from the TCSWs to the curved bottom flanges, resulting in the TCSWs and curved bottom flanges resisting shear force together. This study also reveals the shear force transfer efficiency in the maximum cantilever stage of the bridge. The results indicate that the shear bearing mechanism of the girder undergoes a gradual transition from a state where TCSWs are the primary shear resisting member at the section near the free end to a state where both TCSWs and the curved bottom flange collaborate to resist shear force as the section moves towards the pier. The study suggested that the maximum shear bearing ratio of the curved concrete bottom flange can reach 60.55% at the section near the pier, starting to replace the TCSWs as the main shear bearing member. Consequently, the shear force calculation method recommended by the existing standards may result in substantial computational errors, with the maximum error reaching as high as 155.62%.