Bar Forces Research Articles

Wood jam characteristics influence but do not fully explain wood jam morphologic functions

In-stream wood jams alter their surrounding channel morphology, thus setting riverscape morphology and ecosystem function. While wood jams clearly scour pools, retain sediment, and influence bank erosion, there is a lack of observational evidence of how wood jam characteristics themselves control morphologic effects. Here, I analyzed field observations of hundreds of wood jams to test the hypothesis that wood jam characteristics can predict local morphologic effects such as sediment retention, bar forcing, and pool scour. I found mixed support for this hypothesis: While jam characteristics such as porosity, channel blockage ratio, thalweg occupation, and having rootwads and multiple trunks significantly predicted morphologic effect occurrence and magnitude, they only explained a small portion of the variance in those morphologic effects. While wood jam characteristics are relevant in controlling their overall morphologic functions, those functions are both inherently variable and likely affected by numerous other factors, such as reach-scale topography, the sediment transport capacity to supply ratio, and interactions with surrounding wood and vegetation. Wood function restoration may be more effective if it targets reach-scale objectives across dynamic wood jam assemblages, instead of individual jams.

Innovative design and construction of a closure joint for inland-river immersed tunnels via dry-land construction methods: A case study of the Yuliangzhou tunnel in China

Closure joints constructed to fill the spaces between immersed tunnel elements or between the tunnel elements and adjacent cut-and-cover tunnels are crucial for the longitudinal stability of immersed tunnels and affect the overall cost and duration of tunnel construction. To avoid the obstruction of navigation and reduce the difficulty of constructing closure joints, dry-land construction methods have been widely applied to construct closure joints for inland-river immersed tunnels, in particular using procedures involving axial dry docks. However, the traditional dry-land construction method has many inherent drawbacks. For example, the construction of underwater large-scale reinforced concrete antiretreat structures involves many underwater works, complicated construction processes, long operation time spans and high costs. Based on the Yuliangzhou immersed tunnel in China, a new dry-land construction method for closure joints of inland-river immersed tunnels based on tunnel–soil interface friction was developed to address the abovementioned problems. Considering the adverse influences of back-silting sediment on tunnel–soil interface friction, large-scale laboratory and onsite shear tests were carried out to derive the interface friction coefficients between the tunnel element base slabs and prelaid pebble foundation beds. A composite concrete steel sandwich (CCSS) water-retaining system was designed and assembled to separate the water in the dry dock from the river course. A simplified analysis method based on numerical simulations for the determination of the equivalent horizontal thrust P applied to element ES caused by the dewatering of the axial dry dock was proposed. Based on horizontal antisliding stability analyses of the tunnel elements during the axial dry dock dewatering stage, equations for the key design parameters of the new dry-land construction method were established. Through examination of the static equilibrium of the tunnel elements in the tunnel longitudinal direction, temporary longitudinal displacement constraint (LDC) structures at the immersion joints were designed. Furthermore, the following key construction techniques for the new dry-land construction method were systematically designed: installation of a CCSS water-retaining system at the entrance of the axial dry dock, water sealing at contact gaps, installation of finish-rolled screw-thread (FRST) steel bars as the LDC structures at the immersion joints, and construction of rigid connections between tunnel element ES and the cut-and-cover tunnel. Finally, onsite observation of the deformation states of Gina gaskets and monitoring of the tensile forces of FRST steel bars at the immersion joints verified the successful implementation of the new dry-land construction method, supporting the use of these techniques in closure joint design and construction for inland-river immersed tunnels.

Stability Analysis of “321” Prefabricated Highway Steel Truss Bridge

The “321” prefabricated highway steel truss bridge is widely used for highway rescue, disaster relief, and emergency traffic. This paper uses a 33 m double-row monolayer “321” prefabricated highway steel truss bridge to analyze its mechanical properties and component stability. The actual traffic flow capacity of a total weight of 53.32 tons is used in this study. The results show that the maximum internal force in the truss chord (including the stiffening chord) occurs in the middle span section when a centrally distributed load is applied. Meanwhile, the maximum internal force of truss diagonal members and truss vertical bars appears at the fulcrum section. Under the eccentrically distributed load, the maximum internal forces of truss chords (including stiffening chords) appear in the middle span section, which is closest to the vehicle load, while the maximum internal forces of truss diagonal members and truss vertical bars appear in the fulcrum section, which is closest to the vehicle load. While the maximum internal forces under the eccentrically distributed load are greater than the maximum internal forces under the centered-layout load, under the vehicle load, truss chords (including stiffening chords) are prone to buckling instability, and the buckling mode is mainly reverse out-of-plane buckling. The inclined members of the truss are prone to buckling instability, and the buckling mode is mainly the combination of out-of-plane bending and two-way out-of-plane bending. Truss vertical bars have good stability and are not easy to buckle. The main conclusions of this paper can provide references for the optimal design and operation safety of prefabricated highway steel truss bridges.

Liquid Silicone Rubber Headlamp Lens Injection Molding Process Optimization Based on Tie Bar Elongation and NSGA III.

This study aimed to improve the injection molding quality of LSR material lenses by optimizing the process parameters. To achieve this goal, we employed the population-based optimization algorithm NSGA-III, which can simultaneously optimize multiple objective functions and identify an equilibrium point among them, thereby reducing the time required to find the optimal process parameters. We utilized analysis software to simulate the injection molding process of LSR material lenses, with a specific focus on examining the relationship between tie bar elongation and the optimized process parameters. During the study, we intentionally varied key process parameters, including the melt temperature, holding pressure, and holding time, to analyze their impact on the residual stress of the final product. In order to investigate the intricate relationship between the tie bar yield, injection molding process parameters, and lens residual stress, we installed strain sensors on the tie bar to continuously monitor changes in clamping force throughout the injection molding process. The experimental results showed that both the tie bar force and mold cavity pressure exerted significant influence on residual stresses. By applying the NSGA-III algorithm for optimization, we successfully determined the optimal process parameters, which included a melt temperature of 34.92 °C, a holding pressure of 33.97 MPa, and a holding time of 9.96 s. In comparison to the initially recommended process parameters during the design phase, the optimized parameters led to reductions of 12.98% in clamping force and 47.14% in residual stress. Furthermore, the average transmittance of the actual product remained within the range of 95-98%. In summary, this approach not only enables the prediction of the lens's residual stress trends based on the tie bar elongation, but also leads to a substantial enhancement of lens quality, characterized by reduced residual stress and improved transmittance through the optimization of process parameters. This methodology can serve as a valuable guide for optimizing real-world injection molding processes.

Perbandingan Hasil Analisa Perhitungan Rangka Kuda-Kuda Kayu Dengan Menggunakan SAP-2000 dan Metode Titik Buhul

This research is a study that discusses the comparison of the results of the analysis of the calculation of the forces on the wooden framework using the Structure Analysis Program-2000 (SAP-2000) and method of joint. The value of each force of vertical bars, horizontal bars, tensile bars, and compression members at each point of the wooden framework will be calculated on three wooden framework spans with spans of 7m, 9m, and 11m. Comparison of the results of the calculation of the value of the rod force from the two methods will be compared to see the efficiency of the calculation analysis of the two methods. From the results of the calculation of the method of joint and the Analysis of Structure Analysis Program-2000 (SAP-2000) in calculating and analyzing the value of each vertical bar force, horizontal bar, tension member, and compression member, the difference between each rod force is at (0- 0.51) kg. This shows that the calculation analysis using the Structure Analysis Program-2000 (SAP-2000) is faster and more efficient in calculating each bar force.

Fiber-based characterization of pulp refining

Fiber development in pulp refining can be characterized by three parameters: number of impacts on pulp, N; energy per impact, I, and bar force on fibers, F. These parameters enable comparisons of radically different refining conditions; determination of intensity for hardwoods and softwoods; assessment of effect of bar width on fiber shortening; and predictions of tensile strength increases.

Fracture Behavior and Digital Image Analysis of GFRP Reinforced Concrete Notched Beams.

This study presents three-point bending fracture tests on glass fiber-reinforced polymer (GFRP) reinforced concrete notched beams. Few studies have been conducted to date to understand the fracture behavior of this type of specimens. The specimens have nominal depth, width, and length equal to 150 mm, 150 mm, and 550 mm. Plain concrete notched beams with the same dimensions are cast from the same batch of concrete to compare the responses with GFRP reinforced concrete notched beams. The notch of the plain concrete specimens is either saw cut or cast. These two notch fabrication methods are compared based on the load responses. The peak load, crack mouth opening displacement (CMOD), GFRP bar slip at two ends, and load point displacement are used to discuss the results of the fracture tests. In addition, digital image analysis is performed to identify the fracture process zone (FPZ) and the location of the neutral axis, which are used to determine the force in the GFRP bar via cross-sectional analysis. Finally, the GFRP bar force versus slip responses are compared with those from the pull-out tests performed on the same bar to show that the bond of the bar in the pull-out tests represents an upper bound limit compared to the behavior in bending.

Failure analysis of the segment finger bar mower and force interaction of the blade segment with the plant stem

Scientific observations on the quality and reliability of combine harvesters have shown that of all the delays of equipment, 32...35% of the total operating time, technical failures account for 17.4...19.8%. Most of the failures were observed with the failure of combine parts, mechanical transmissions, hydraulic systems, etc. Quantitative analysis of harvester failures has shown that most failures occur in the operation of the cutting device, namely the finger bar mower. The working hypothesis is that it is possible to increase the reliability of the cutting device of harvesting machines in ordinary operating conditions and in the event of sudden failures by applying a coating on the blade segment, without significantly changing its geometric parameters, and performing notches that ensure both a decrease in the mass of the segment and its destruction without plastic deformation when foreign objects enter the cutting zone. The main problem of the reliability of segments of cutting device, harvesting equipment, is the cutting edge of the blade, which wears out and deforms during operation. From the above, it follows that the purpose of the study is to improve the reliability of segment finger bar mower machines by improving the mechanical properties of segments, these investigations are relevant and of practical interest. The study includes the use of mathematical probability and reliability theory, analysis, and a systematic approach to provide an analytical description of the operation of a cutting device segment. The consequence of this scientific investigation is an analysis of failures and malfunctions of the machinery, presented graphically, a diagram of how a plant stem segment is cut and the forces acting on the stem and the segment during the cutting process are depicted. These materials have scientific and informative content that would be of interest to engineers and scientists in the process of research and production of cutting device segments

Limit design of reinforced concrete haunched beams by the control of the residual plastic deformation

In this paper, a novel computational (optimization) model is presented to control the plastic behaviour of reinforced concrete haunched beams using complementary strain energy of residual forces formed inside the steel reinforcing bars. For this purpose, a numerical model validation process was held and then two non-linear optimization problems were outlined. In these optimization problems, different objective functions were considered applying the optimal elasto-plastic analysis and design of haunched reinforced concrete beams aiming to find the maximal loading or the minimum volume of the steel used to reinforce the beams as the plastic deformations are controlled by using constraints on the complementary strain energy of the residual internal forces of the steel bars. Moreover, the effect of these constraints on different haunch angle beams is studied. The applied method is described in terms of nonlinear mathematical programming and providing solutions when the plastic reserves of the body are not fully exhausted. It is worth mentioning that in this study a concrete damage plasticity constitutive model is applied in the numerical problems and calibrated in accordance with the data gained from laboratory tests. The optimal solutions of the nonlinear mathematical problems were calculated by MATLAB programming codes written by the authors taking into consideration different objective functions and equality and inequality constraints for each case. Finally, by performing a parametric study, the different optimization problems showed how beams behaved differently under different complementary strain energy limit values shifting from elastic into elasto-plastic state and then reaches the fully plastic state where results showed different comparisons taking into consideration the effect of the different complementary strain energy limit values on the maximum applied load, geometry of the beam and steel volume used to reinforce the beams. Thus, complementary strain energy limit value is used to control the plastic deformation inside steel bars during loading progress where avoiding the formation of the plastic deformation in the steel bars would reflect on the general behaviour of the haunched reinforced concrete beams.

Effects of plate wear on bar forces and fiber properties in a mill scale LC-refiner

Abstract A set of piezo electric force sensors is implemented in a 52-inch mill-scale low consistency refiner to explore the effect of refiner plate wear on bar force sensor measurements. The sensor replaces a short length of a stator bar and measures normal and shear forces applied during the passage of each rotor bar. In previous work with this type of force sensor, force profiles for individual bar passing events (BPE) were investigated. In the work presented here, force profiles for individual BPEs are identified based on key features in the time domain force data. The individual bar force profiles are classified as single peak events which feature one peak corresponding to the fiber compression force and as dual peak events corresponding to fiber compression force and the corner force. The bar passing events are then analysed, based on dual peak ratio and time to peak of the early peak in the dual peak events. Force measurements are evaluated over the full run time of a set of refiner plates. Findings are compared with refiner plate wear measurements and discharge fiber analysis. It is shown that the decrease in the prevalence of the corner force correlates with the wear of the leading edge of the refiner bars or bar rounding of the run time of the refiner plate. This is accompanied by a decrease in plate performance which is represented by a decrease in fiber length and freeness reduction for the same refiner load.

Interpretation of force profiles in mill-scale LC refining

Abstract A set of piezo electric force sensors is implemented in a 52-inch mill-scale low consistency refiner to explore the effect of varying operating conditions on bar force profiles. The sensor replaces a short length of a stator bar and measures normal and shear forces applied during the passage of each rotor bar. In previous work with this type of force sensor a rotary encoder was used to investigate force profiles for individual bar passing events (BPE) on a 16-inch laboratory-scale refiner. In the work presented here, force profiles for individual BPEs are identified based on key features in the time domain force data. The individual bar force profiles are classified as single peak events which feature one peak corresponding to the fiber compression force and as dual peak events corresponding to fiber compression force and the corner force. The bar passing events are then analysed based on their mean force profiles and their dual peak ratio in the bar passing event. Findings are compared and validated by previous work on bar force profiles. It is shown that dual peak events which are considered to represent the corner force, are present through out the whole range of refining and increase with increased refining energy. This increases the understanding of the way corner force contributes to the refining process. Furthermore, it is found that different radial positions on the stator plate are subjected to different force profiles. This is thought to be due to the difference in tangential speed and a change in the fiber and floc material properties at different radial positions.

Displacement Control of Nonlinear Pin-Jointed Assemblies Based on Force Method and Optimization

The geometry of the structure and internal bar forces under varying service load situations or prestressing actually impact on the structure’s serviceability. Or else, prestressed cable structures are defined by the joint locations and delicate to external stimuli due to their high flexibility and light weight, and the shape distortion is supposed unacceptable. Consequently, based on the force method, the displacement control through updating coordinates of the structure and optimization on the form of quadratic programming is suggested to attain the nonlinear displacement control (NDC) of the geometrically nonlinear systems (including prestressed cable structures). The technique preserves the prestress level in the structural bar elements to any level required. The proposed method has been compared with other prior NDC techniques corresponding to the requirements. It shows that the computational results of the current approach are in good response with the previous NDC techniques. The method can exactly achieve the target values without any significant errors for the corresponding outcomes. Simultaneously, the technique keeps the prestress level of the structural members to the targeted level. The proposed approach technique also proved to control both small and large displacement without any remarkable error.

Bar forces in pulp refiners

Abstract Refiners develop pulp properties by applying forces on fibres during bar crossings. The size of these forces is critical in developing fibre properties while avoiding fibre shortening. This study has shown that bar force calculated from Specific Edge load (SEL) gives the same result as vector-based derivations of average bar force. Predicted forces agree reasonably well with ones measured by a novel piezo-electric sensor in refiner bars and forces estimated from measurements of fibre shortening.

РАСЧЕТ НАДЕЖНОСТИ ЭЛЕМЕНТОВ СТАЛЬНЫХ ФЕРМ ПО КРИТЕРИЮ УСТОЙЧИВОСТИ С ИСПОЛЬЗОВАНИЕМ РБЛОКОВ

Abstract. The reliability of load-bearing structural elements is one of the indicators of structural safety. The article presents methods for steel trusses bars reliability analysis according to the buckling criterion using p-boxes. A p-box consists of two boundary probability distribution functions that form the area of possible distribution functions. Such model used for modeling random variables in conditions of incomplete statistical data by quantity or quality. An algorithm for summing p-boxes of random load models is demonstrated on the example of a probabilistic estimate of the force in the truss bar. The result of reliability analysis using p-boxes is presented in interval form. The use of p-boxes makes it possible to obtain a more cautious assessment of reliability in case of incomplete statistical data. To increase the informativity of the reliability analysis result, it is necessary to obtain more statistical data about random variables in design mathematical models of limit state, which will allow forming p-boxes with narrower boundary distribution functions.

Shear design method for non-prismatic concrete beams reinforced using W-FRP

Flexible fabric formworks and bespoke Wound Fibre-Reinforced Polymer (W-FRP) cages have been proposed to address the difficulties of constructing geometrically optimised concrete structures with minimised material consumptions. However, the existing codes of practice for FRP reinforced concrete structures are not able to provide accurate shear behaviour predictions, resulting in potential premature anchorage failure. This paper presents a revised shear design approach for non-prismatic beams reinforced with W-FRP based on the Modified Compression Field Theory (MCFT), which considers the non-prismatic geometries, geometrical nonlinearity and internal load redistributions. The revised shear design approach is calibrated against previous fabric-formed T beam tests and parametric analyses are conducted to minimise the material usage of the previous T-beams. The validity of the shear design approach is further confirmed with a new T-beam test. The new test shows that the T beam designed with the MCFT based approach failed in the expected flexural failure mode with an ultimate capacity of 245 kN applied load. The predictions can effectively model the bar force development of the inclined flexural reinforcement with a Normalised Root Mean Square Error (NRSME) of 4.4%. The proposed shear design method improved the prediction accuracy of flexural bar force at ultimate capacity by 40% compared to the codified shear design method. By addressing the shear contributions of inclined flexural reinforcement and required anchorage strength, further applications of this novel flexibly formed beams with optimised geometries are expected to achieve material consumption reduction and hence lower carbon emissions from concrete structures.

The Optimum Power Load: A Simple and Powerful Tool for Testing and Training.

The optimal power load is defined as the load that maximizes power output in a given exercise. This load can be determined through the use of various instruments, under different testing protocols. Specifically, the "optimum power load" (OPL) is derived from the load-velocity relationship, using only bar force and bar velocity in the power computation. The OPL is easily assessed using a simple incremental testing protocol, based on relative percentages of body mass. To date, several studies have examined the associations between the OPL and different sport-specific measures, as well as its acute and chronic effects on athletic performance. The aim of this brief review is to present and summarize the current evidence regarding the OPL, highlighting the main lines of research on this topic and discussing the potential applications of this novel approach for testing and training. The validity and simplicity of OPL-based schemes provide strong support for their use as an alternative to more traditional strength-power training strategies. The OPL method can be effectively used by coaches and sport scientists in different sports and populations, with different purposes and configurations.

Transient Roebel Bar Force Calculation in Large Salient-Pole Synchronous Machines

The radial and tangential force components acting on each sub-conductor of a Roebel bar in a large generator lead to mechanical vibration of the stator bars in the slot. This double-frequency vibration results in additional mechanical stress on fixation materials in the slot and causes insulation deterioration and looseness of stator bars. Particularly during short circuits, the stator bars are subjected to immense radial forces. Understanding the origin of these vibrations and developing models to anticipate them is essential to increase the reliability and expected life time of large generators. This paper presents an analytical method for the estimation of Roebel bar forces during symmetrical and asymmetrical short circuits. For this purpose, an analytical calculation method is developed to estimate the transient three-phase currents during different short circuits. These currents induce tangential and radial flux density components along the slot width and length, respectively. An analytical approach is introduced to estimate these flux densities as a function of the slot length. Subsequently, an analytical method for calculating the Roebel bar forces considering three-dimensional transpositions is developed and verified with finite element calculations. Beyond the state of the art, the impact of the rotor field on the radial and tangential components of the stray fluxes are analytically estimated. The result is a comprehensive analytical tool for the estimation of Roebel bar forces during different short circuits in large generators.

Contact element use peculiarities in the numerical model construction of the reinforcing bar force interaction with an anchoring field

The application experience of non-metallic composite materials is quite wide in foreign countries, as well as systematized and assembled into a single database. In Russia, since the necessary computing resources have become more relevant and accessible for design organizations, independent researchers, and graduate students of higher educational institutions, this question resurfaced only in the last decade. As well as benefits, non-metallic composite reinforcement has its disadvantages, which prevent it from wide usage in structures, including a relatively low elastic module, as well as the inability to bend during installation. To improve the reinforced structures with stressed reinforcement calculation and possible prestressing force loss prediction, the finite element model production has been discussed. This model would allow us to evaluate the damaging shear stresses in the reinforcement region. The bracing formation process in the scope of this model was presented in this article, with the purpose of simulation the contact layer stress-strain state between reinforcement and concrete. The calculation is performed in a linear setting. Model development of a T-section decking component reinforced with a composite reinforcement beam produced via LIRA SAPR software. Exert a force on shank ends that is equivalent to the clamping force when the prestressed reinforcement is released. The authors proposed a selection option of the junction stiffness by stem contact with the anchoring field. The stiffness is assumed to be constant along the entire length of the contact layer. Elastic coefficient variation of the contact layer was performed here. The contact layer is highlighted conditionally as a separate material. A model for three types of materials was discussed. The shear stresses patterns in the contact element region were obtained. The patterns of abutting end reinforcement bars motion are obtained. To create a span element with a pre-tensioned reinforcement, a full-scale experiment was performed, as well as reinforcement abatement. Upon abatement, the retraction was recorded. The retraction results of the shank ends were measured, the values of which are comparable to the numerical motion.

Performance and reference data in the jump squat at different relative loads in elite sprinters, rugby players, and soccer players.

The aims of this study were to compare the outcomes and provide reference data for a set of barbell mechanical parameters collected via a linear velocity transducer in 126 male sprinters (n = 62), rugby players (n = 32), and soccer players (n = 32). Bar-velocity, bar-force, and bar-power outputs were assessed in the jump-squat exercise with jump-squat height determined from bar-peak velocity. The test started at a load of 40% of the athletes’ body mass (BM), and a load of 10% of BM was gradually added until a clear decrement in the bar power was observed. Comparisons of bar variables among the three sports were performed using a one-way analysis of variance. Relative measures of bar velocity, force, and power, and jump-squat height were significantly higher in sprinters than in rugby (difference ranging between 5 and 35%) and soccer (difference ranging between 5 and 60%) players across all loads (40–110% of BM). Rugby players exhibited higher absolute bar-power (mean difference = 22%) and bar-force (mean difference = 16%) values than soccer players, but these differences no longer existed when the data were adjusted for BM (mean difference = 2.5%). Sprinters optimized their bar-power production at significantly greater relative loads (%BM) than rugby (mean difference = 22%) and soccer players (mean difference = 25%); nonetheless, all groups generated their maximum bar-power outputs at similar bar velocities. For the first time, we provided reference values for the jump-squat exercise for three different bar-velocity measures (i.e., mean, mean propulsive, and peak velocity) for sprinters, rugby players, and soccer players, over a wide range of relative loads. Practitioners can use these reference values to monitor their athletes and compare them with top-level sprinters and team-sport players.

An Approximate Linear Analysis of Structures Utilizing Incremental Loading of Force Method

A relatively simple technique has been introduced in this paper. The approach is based on the Linear Force Method (FM) with discretion of the applied loads to the subsequence steps and updating coordinates in each iteration to have new geometrical property. The accuracy of the technique depends on the size of the discretion which depends on the number of iterations. A small change in the configuration could hugely affect the displacement and internal forces in geometrically nonlinear structures, that’s why the current approach is vital. The proposed technique is validated with other techniques of nonlinear analysis of the structures with a very good agreement in both terms of external nodal displacements and internal bar forces.