Proposed Calculation Method Research Articles

Calculation Method for Flexural Bearing Capacity of Composite Girders with CFST Truss Chords

To study the flexural behavior of composite girders with concrete-filled steel tubular (CFST) truss chords under positive and negative bending moments, model tests, and theoretical analysis were carried out to investigate the evolution of their flexural behavior and the flexural bearing capacity. The results showed that the web members and joints of composite girders with CFST truss chords subjected to positive and negative bending moments had high strength and rigidity, which ensured that joint failures did not occur before the failure of the entire cross section. The longitudinal strains along the member axis changed linearly along the cross-sectional height, which confirmed the correctness of the plane-section assumption. The failure mode was due to the yield of the steel tube used in the chord and the rebars in the concrete slab under positive and negative bending moments, respectively. The contributions of the web members to the flexural bearing capacity under positive and negative bending moments were 12.5% and 8.6%, respectively. Calculation methods considering the contributions of the web members to the flexural bearing capacity under positive and negative bending moments were proposed. The deviation between the results of the proposed calculation methods and the test and the results of the finite-element parametric studies was less than 8.1%.

Design and Parameter Optimization of Trajectory Correction Control Strategy for Air Duct Structure Projectile

In order to make the new air duct structure trajectory correction projectile have good dynamic correction control effect, the control strategy of the projectile’s correction mechanism is studied in this paper. A design method of trajectory correction control strategy based on particle swarm optimization-cuckoo search (PSO-CS) hybrid algorithm is proposed to obtain the optimal control parameters that can make the projectile flight stable and correct accurately. Firstly, the mathematical model of the air duct structure projectile is established. Secondly, the multiobjective optimization problem is analyzed. The projectile’s correction control strategy optimization model is established by taking the start control time, the number of corrections, the correction working time, and the interval time as the control variables. The optimization model innovatively considers the influence of the correction action on the flight stability of the projectile and the influence of the start control time on the correction range. Finally, the PSO-CS hybrid algorithm is used to design the calculation method of the optimization model and solve the optimal correction working parameters. The simulation results indicate that the control strategy optimization model can be solved by the proposed calculation method. Moreover, optimal correction working parameters of the correction mechanism in the current state can be obtained. Compared with the results of using single PSO algorithm and CS algorithm, the correction scheme calculated by PSO-CS hybrid optimization algorithm is better. This correction control scheme can effectively reduce the impact point deviation and make the projectile flight stable. At the same time, the circular error probable (CEP) of the projectile after correction is reduced from 42.3 m to 4.6 m while the impact point dispersion is lowered. The research results show that the design method of correction control strategy proposed in this paper is effective for trajectory correction of the new air duct structure projectile.

Study on upper bound limit analysis of horizontal layers slope stability based on optimization method

Slope stability is an important problem in the field of geotechnical engineering. In order to widen the application range of upper bound limit analysis in engineering practice, this paper analyzes layered distribution characteristics of slope soil and establishes horizontal layers slope failure mechanism which satisfies the separation of velocity, then proposes calculation method for external force power and internal energy dissipation power using discrete algorithm. On this basic, this paper prepares cycle flow of slope stability analysis by upper bound limit principle and strength reduction principle, and develops stability analysis system by computer programming technology. Taking typical mine excavation slope as engineering background and calculates stability coefficient corresponding to different slope angles and evaluate analysis results accuracy by combining with limit equilibrium method. The results show that the stability coefficient error rate of two methods is between 3 and 5%, which can satisfy requirements of engineering practice. Moreover, stability coefficient obtained by upper bound limit analysis is an upper limit solution, and calculation errors are easy to eliminate, so it has certain applicability in slope engineering practice.

Punching shear strength model of reinforced concrete footing considering bilinear contact stress on subgrade

The present design codes assume a linear distribution of contact stress on subgrade. Actually, the contact stress on subgrade is a nonlinear distribution. To evaluate the error caused by linear contact stress relative to nonlinear contact stress on the punching shear strength of RC footing, this paper performed punching test of footing with different eccentricity and the column perimeter to effective depth ratio, considering nonlinear contact stress on subgrade. Based on the experimental results and analysis, a bilinear contact stress distribution on subgrade is proposed. Furthermore, the calculation method based on the most unfavorable side checking is proposed to weaken the influence of the overall nonlinear contact stress. Finally, the proposed calculation method is verified for reliability and applicability based on the available experimental data. The results show that eccentricity and column perimeter to effective depth ratio significantly affect the punching shear capacity. The error caused by linear contact stress should be a concern by the codes. The bilinear contact stress distribution on subgrade is suitable for non-cohesive soil. The proposed calculation method has good reliability and applicability, and it meets the challenge posed by the nonlinear contact stress on subgrade for the assessment of column footing punching shear capacity.

Force of cutting by a single abrasive grain

This paper investigates the cutting forces arising when using a single abrasive grain. Analytical studies were carried out using a model of a single abrasive grain in the form of a rod with a radiused apex acting on the workpiece material. The slip-line method (method of characteristics) was used to calculate the deformation intensity of a plastically edged workpiece material under the action of a single grain. Mathematical models were developed for the following factors: plastic deformation of the material, edging of the stagnated zone and its friction against the grain surface when moved upwards in the form of chippings, grain friction against the plastically deformed material, and the action of the dynamic component of plastic deformation. The significance of the dynamic component in the overall balance of forces related to plastic deformation was established by determining the ratio of dynamic stress on the break line and shear yield point. This dependence calculated for D16T and 30HGSA materials showed the feasibility of accounting for the dynamic component of the cutting force under the velocity of a single grain impacting the workpiece surface of above 50 m/s. Graphs depicting the relative grain force and the relative depth of grain penetration are given. The proposed calculation method for cutting forces using a single grain can be used to determine the total force of interaction between the single grain and the work-piece material. In order to adopt the defined processing method and the workpiece material, the number of grains in contact, the contact duration, and the cutting speed should be found. On this basis, the process performance and the quality of the workpiece surface can be calculated.

Nonlinear Calculation of the Reinforced Concrete Road Pavement Slabs of Highways on the Elastic Basis by the Zhemochkin Method

A rectangular reinforced concrete slab is considered taking into account its physical nonlinearity on a linearly elastic homogeneous base under the action of a vertical external load. The anisotropy and heterogeneity of the slab are due to the properties of reinforced concrete, as well as the formation of cracks from the action of an arbitrary load during operation. The nonlinear problem was solved by the Zhemochkin method using the iterative algorithm of the Ilyushin elastic solution method. The Ritz method (determining the deflections of a slab with a pinched normal) and the Boussinesq solution (determining the displacements of points on the surface of an elastic half-space) were used to determine the coefficients of the resolving equations of the Zhemochkin method. At the first iteration, the slab was calculated as linearly elastic, orthotropic, and homogeneous; at subsequent iterations, it was calculated as linearly elastic, anisotropic, and inhomogeneous at each Zhemochkin site. The deflections of the middle surface of the slab from a unit force were determined as a series according to the first five particular Clebsch solutions. Experimental and numerical researches have been carried out. The latter – with the help of the MATHEMATICA computer program. The results obtained showed that the proposed calculation method allows one to accurately describe the distribution of settlements and reactive stresses under the slab. Verification of the methodology for static nonlinear calculation of a rectangular reinforced concrete slab, taking into account its physical nonlinearity, was carried out by comparing the results of calculations of maximum settlement and average pressures under the slab, obtained using the proposed methodology, and the results obtained using the layer-by-layer summation method and modern software systems Lira and PLAXIS 3D.

Динамический расчет напряженно-деформированного состояния коленчатого вала

The paper describes application of the finite element method in the explicit formulation (Explicit) for dynamic calculation of the stress-strain state of the full-size crankshaft represented by a continuous model taking into account contact interaction with the supports and the rapidly varying nature of the loading. The procedure for preparing and imposing the corresponding force boundary conditions is described. The proposed calculation method makes it possible to simultaneously determine the instantaneous values of stresses due to the incoming torques and additional stresses caused by all types of oscillations (torsional, longitudinal and bending).

A Time-Domain Piecewise Analytical AC Harmonic Current Calculation Method Suitable for Capacitor Commutated Converter

The Capacitor Commutated Converter (CCC) is constructed as a conventional Line Commutated Converter (LCC) modified with a series capacitor between the converter transformer and thyristor valves in each phase. This paper proposes a time-domain piecewise analytical AC harmonic current calculation method for the CCC system. Compared to the existing calculation methods, the proposed method can calculate both characteristic and non-characteristic harmonics simultaneously when various asymmetric factors are considered. Firstly, the overlap angles are calculated considering the asymmetric factors after partitioning the piecewise intervals in a fundamental period. Secondly, the AC harmonic currents are calculated considering the DC side harmonic currents based on the Thevenin equivalent model of the DC circuit. Then, the effectiveness of the proposed calculation method is validated by simulation results in PSCAD/EMTDC. The comparison result shows that the proposed method is high-efficiency and high-accuracy for the AC harmonic current calculation of the CCC system and can meet the requirement of CCC filter design in practical projects. Finally, the influence of the asymmetric factors on the overlap angle calculation and the influence of the commutation capacitor variation on the commutation parameters are studied.

Seismic behavior and theoretical analysis of mortise–tenon joints reinforced with steel components

Wood structures have been vigorously popularized and developed because they have low carbon emissions and acceptable earthquake resistance. To solve the general pull-out failure of mortise–tenon joints (MTJs) under earthquake loads, reinforcement techniques, such as steel strip plate (SSP), hollow rectangular steel plate (HRSP), U-shape steel plate (USP), and T-shape steel plate (TSP) methods, have been proposed. Low cyclic loading tests were conducted on five joints to investigate the effect of reinforcement methods on the seismic behavior of MTJs. Furthermore, the peak bearing capacity of reinforced MTJs was theoretically analyzed based on European, American, and Chinese specifications; the calculations were compared with the test results. To verify the accuracy of the theoretical analysis, ABAQUS software, a finite element simulation application, was used. The test results show that the failure modes of joints with or without reinforcements are tenon pull-out, self-tapping screw pull-out, and shear failure. Moreover, the USP-reinforced MTJ exhibited the best seismic performance, followed by the MTJs reinforced with TSP, HRSP, and SSP. The theoretical calculation and test results are in good agreement. The simulation results indicate that the proposed calculation methods can accurately predict the peak bearing capacity of steel-reinforced MTJs.

Determination of rheological properties of crude oil blends

The article presents an overview of widely applicable methods of calculation of viscosity of liquid mixtures, as well as rheology characterisation of crude oil. It is focused on the evaluation of rheological properties, particularly in order to assess the flow conditions in pipelines at different temperatures and flow rates, especially in the case of waxy crude oils. A specific calculation procedure was proposed and described, suitable for practical purposes, i.e. field implementation in the form of a spreadsheet calculator. Using this method, it is possible to calculate the rheological properties of a mixture of known components at a given temperature over a range of shear gradients corresponding to a specified range of flow rates in a circular pipeline of specified diameter. The proposed calculation method was verified on the properties of specific types of oils and their mixtures.

Seismic performance of precast concrete walls with grouted sleeve connections using large-diameter bars

This paper proposes an innovative assembly technique using large-diameter bars anchored in several single-row, widely spaced grouted sleeves at the keyway-type horizontal joint to realize an indirect vertical connection between adjacent precast concrete (PC) walls, which has the advantages of high efficiency and ease of construction. To examine the effect of vertical connection strength (rebars' diameter at horizontal joints) on the seismic performance of PC shear walls, quasi-static cyclic loading tests on five full-size wall specimens, including one cast-in-place specimen and four PC specimens with grouted sleeve connections, are carried out. Seismic performance indicators in terms of failure modes, hysteresis characteristics, energy dissipation, ductility, and stiffness degradation of PC walls are investigated and compared with those of the cast-in-situ wall. Meanwhile, the method for predicting the bearing capacity of PC walls with large-diameter rebars is developed. The results show that the failure modes of cast-in-situ and precast walls are controlled by bending instead of shear, but there is an obvious difference in the crack propagation between the two types of walls. Carrying capacity, ductility factor, stiffness, and energy dissipation of PC walls are significantly enhanced by increasing the connection strength, by 44.1%, 23.9%, 72.1%, and 24.0%, respectively, when the connection strength reaches around 90%. Particularly, the PC wall's seismic performance is comparable to that of the cast-in-situ wall when the connection strength is 90%. The calculated results are well-matched with the experimental results, the proposed calculation method reliably predicts the bearing capacity of PC walls with large-diameter rebars. The assembly technique can be safely applied to multi-story PC wall panel structures in seismic zones.

Experimental investigation on composite girders with CSW-CFST truss chords subjected to combined flexure and torsion

As a new type of composite girders, composite girders with corrugated steel webs and concrete-filled steel tubular (CSW-CFST) truss chords are extensively utilized in bridge engineering. To examine the structural behavior of composite girders with CSW-CFST truss chords subjected to combined flexure and torsion, model tests and finite element analysis (FEA) are employed. Using these efficient tools, the strain distribution, deformation law, failure mode, and bearing capacity of these composite girders subjected to pure torsion and combined flexure and torsion are methodically obtained. The primary objectives are to probe the applicability of existing flexure-torsion relation curves and introduce the calculation method for the bearing capacity of composite girders with CSW-CFST truss chords subjected to combined flexure and torsion. The obtained results reveal that their failure mode is influenced by the initial torsional moment. Further, their bearing capacities due to the applied initial torsional and bending moments can be maximally enhanced by about 21.6% and 6.6%, respectively. The deviation between the predicted bearing capacity by the FEA and that obtained from the tests is less than 8.6%, demonstrating the high accuracy of the FEA model. The contribution of the torsional moment to the flexural bearing capacity is either ignored or underestimated by the existing flexure-torsion relation curves, with a minimum deviation of about 22.3%. By comparing the results acquired by the extended FEA and the calculation method proposed in this paper, it is proved that the proposed calculation method for the bearing capacity of composite girders with CSW-CFST truss chords subjected to combined flexure and torsion may reduce the deviation from 22.3% to 8.3%.

A deep learning-based bridge damage detection and localization method

Existing studies have utilized highly efficient partial least-squares regression (PLSR) to estimate nodal loads of the entire bridge using a small number of bridge sensors, and when the structure is damaged, the estimated nodal loads include damage information. Based on the ability of convolutional neural networks (CNNs) that can learn the PLSR method to estimate nodal loads, this paper proposes a bridge damage detection and localization method using inclination or deflection measurements. First, this study develops a method for estimating excessive nodal loads and establishes a framework for bridge damage detection and localization utilizing the change in the deviation of excessive nodal loads estimated by a CNN and the PLSR method before and after structural damage. Then, a CNN model is designed in this study, and the CNN model establishes a mathematical relationship between the monitoring point response as input and the estimated excessive nodal load as output through training. Finally, the detection and localization of bridge damage are realized using the proposed calculation method of damage indicator. The proposed method avoids costly finite element modeling and does not require difficult-to-obtain real structural damage information to train network models, and can achieve real-time detection and localization of bridge damage with a small number of sensors installed. Numerical simulations show that the proposed method can detect and locate damage very accurately and reliably in the presence of unknown loads, multi-damage, and measurement errors, revealing its potential in the field of bridge damage detection.

Estimation of the Impact of the Age Difference in Households of the Same Generation on the Age Level of Consumption

The available methods for calculating the age level of consumption focus on determining the level of consumption by children. At the same time, previous studies show a decrease in the level of consumption after retirement. From a research point of view, it is of practical interest to estimate the distortion of one-year age profile of consumption depending on the age difference between the adult members of the household. Among common episodic households, the paper compares the age profiles of consumption for households with two adults aged 18 to 80 years. The paper compares indexes of average per capita consumption, and estimates the level of age difference in households for the age level of consumption. The author introduces such a concept as “net consumption”, under the influence of which sensitivity to age is absorbed. To create “net consumption” in the general chronology, only households with a minimum age difference are examined.The purpose of the study. Estimation of the age level of consumption depending on the demographic characteristics of the household is little studied in modern literature. As a rule, the papers provide methods for assessing the level of children consumption. However, when creating age profiles of consumption, the age characteristics of households are not taken into account. The aim of the study is to assess the impact of the difference in the age of people living together in a household on the age profiles of consumption. Both in Russia and in the EU countries, the average difference in age between the first marriage is on average 2.5 years, and the largest difference can reach more than 30 years. From a statistical point of view, it is of practical interest to study the average per capita age level of consumption depending on the difference in the age of a married couple.Materials and methods. The source of data for the study is the Household Budget Survey (HBS) conducted by Rosstat for 2020. The paper compares age profiles of consumption created by the minimum age of the household, by the maximum, by the average, and by the classical method. In addition, the paper compares the age profiles created by the classical method, taking into account the limitation of the age difference between household members.Results. The results obtained from the 2020 HBS survey allow conclusions to be drawn about different age profiles depending on the proposed calculation methods. The results of the study showed that among households consisting of two people, almost a third of households (34.1%) have an age difference of more than 5 years. In the context of calculating one-year age profiles of consumption, a significant age difference in age will lead to a distortion of age profiles of consumption. Among households consisting of two people, the largest difference in the level of average per capita consumption between all households of two people and households of two people with an age difference of no more than 1 year is observed in early working ages (from 18 to 22 years). The introduced restrictions reduce the level of consumption by about a third at the age of 18-19 years. The introduced restrictions increase the average per capita level of consumption in the age group of 22-45 years by an average of 9.4% compared to classical calculations. The opposite situation is observed in the age group of 70-80 years old: the introduced restrictions reduce the average per capita level of consumption by 2.9%.Conclusion. The paper draws attention to the different results of the calculation of age consumption, depending on the methodological features. The author introduces the term “net age consumption”, which is calculated for households with an age difference between household members of no more than 1 year. Suggestions for estimating per capita consumption can be applied to model human consumption over the life cycle. At the same time, as a rule, the characteristics of households are far from the “model” consumption, which necessitates further study of the factors affecting the level of consumption depending on the characteristics of the household.

Особенности расчета предела огнестойкости балок из строительных сталей

One of the main directions of research in the field of increasing the actual limits of fire resistance of steel structures is the development and implementation of fire-resistant rolled products with increased thermal stability. Fire-resistant steels are steels whose yield strength when heated to 600 °C is at least 60 % of the yield strength at 20 °C. For their wide application in construction, information is needed on the change in the strength properties of fire-resistant rolled metal products at high heating temperatures. In addition, it is required to develop a method for assessing the bearing capacity of steel structures considering the nature of the temperature distribution in their cross section. The introduction of fire-resistant steels and the proposed method of calculation will in some cases will allow to ensure the normative limit of fire resistance of load-bearing structures or reduce the cost of their fire protection. The experimental and calculated data are obtained concerning the limits of fire resistance of beams made of steel rolled metal of classes S355, S390, as well as S355P and S390P with increased heat resistance. The use of the method for calculating the fire resistance limit of bent steel structures heated from three sides considering uneven heating in the cross section, demonstrates satisfactory convergence with the experimental data for beams made of building steels, including fire-resistant ones with increased thermal stability. Various levels of static load were modeled under the influence of the temperature regime of a standard fire. The research results contribute to the introduction of new types of fire-resistant building steels for the construction of buildings from metal structures. This will increase their safety and stability in case of fire and will lead to a reduction in the construction costs.

Mathematical Modeling of Screw Press Configuration for Processing Safflower Oil

This article is devoted to modeling the pressing process of an experimental screw press for safflower oil production in small enterprises of the grain processing industry. The theoretical analysis for developing the process of oil pressing in a screw press is considered. Using methods of mathematical modeling, the problem of squeezing the liquid phase from dispersed material is described and solved. The basic scheme and characteristics of the press equipment and the principle of its work are presented. The proposed method of the theoretical calculation of the pressing process helps to determine the optimal parameters and to press safflower oil using the proposed design of the screw press. During the process of pressing, the highest value of oil yield is reached at the diaphragm gap of δ = 0.1 mm and screw rotation speed of ω = 6.2 rad/s.

Calculating the ultimate strength of a tube–gusset KT joint with 1/4 ring stiffener plates

In this study, experiments, numerical simulations, and theoretical analyses were performed on tube–gusset KT joints with 1/4 ring stiffener plates, which are frequently used in electrical transmission line towers. The failure modes and mechanisms of the joint were determined to comprise either ‘chord failure’, in which the chord exhibits obvious deformation while the stiffener plate exhibits little deformation, or ‘stiffener plate failure’, in which the chord exhibits obvious concave deformation and the stiffener plate exhibits obvious warping deformation. An increase in chord axial compression caused the ultimate bearing capacity of the joint to decrease, though when the ratio of axial chord force to plastic limit was less than 0.2, this effect of was not obvious. Furthermore, an equation for the ultimate strength of a joint was proposed based on the conservation of energy, which was subsequently verified against test and finite element model results. In this equation, the influence of the chord axial compression on the bearing capacity of the joint is considered using the coefficient β, which is dependent on the ratio of the chord diameter to the chord thickness. Finally, the proposed bearing capacity calculation method was shown to reproduce the numerical analysis results more accurately than the Japanese code or CIDECT code. Thus, the proposed calculation method can be confidently used to guide joint design in electrical transmission line tower projects.

Estimation of the yield and angular distribution of neutrons for calculating the biological shielding of reconstructed heavy ion accelerators with energies from 1 to 6 MeV/u

A simple analytical formulas for estimation of the yield and angular distribution of neutrons from thick targets would be useful for calculating the biological protection of heavy ion accelerators with energy (1–6) MeV/nucleon. The results of the calculation with this formulas were compared with those obtained using the LISE++ and FLUKA programs as well as with the available experimental data. As a result, it can be stated that the proposed calculation method can be used for quick assessment. The deviation of the results of such calculations from more accurate ones does not exceed a factor of two, which is comparable with the deviations in the calculation of biological shielding due to a variety in the protection properties of the materials used or in their thickness.

Experimental and numerical study on the shear strength of new bolted connection assembled shear wall

Although the installation of assembled shear wall has been widely used in structure construction, the splicing zone and structural integrity are still issues of great concern. This paper proposes a new form of bolted connection assembled shear wall (BASW) to improve the construction efficiency and structural integrity of assembled shear wall. To investigate the mechanical behavior and shear strength calculation methods of the new bolted connection assembled shear wall under horizontal load, firstly, four shear wall specimens, including one cast-in-place (CIP) shear wall and three new BASWs, were designed and assembled. After the cyclic loads were applied to the four specimens, failure modes and hysteretic behavior were investigated. Secondly, a numerical model was established and validated by experimental results, and then it was used to analyze the effects of the axial compression ratio, shear-to-span ratio, and hoop ratio on the mechanical behavior and strength. Finally, on the basis of stress mechanism, we derived the calculation methods for the cracking strength, yield strength, and shear strength, respectively. The results show that the mechanical behavior of the BASW is close to that of the CIP shear wall. The shear strength increases with smaller shear span ratios or larger axial compression ratios, but ductility decreases. The lower hoop ratio presents larger shear strength and stiffness, but the range of increase tends to weaken. The calculated values obtained by the proposed calculation methods show good agreement with the experimental results of BASW strength. These results indicate that the bolted connection assembled shear wall has superior behavior, and the calculation nethod proposed in this paper have sufficient accuracy in predicting the BASW strength.

High-Dimensional Covariance Estimation via Constrained Lq-Type Regularization

High-dimensional covariance matrix estimation is one of the fundamental and important problems in multivariate analysis and has a wide range of applications in many fields. In practice, it is common that a covariance matrix is composed of a low-rank matrix and a sparse matrix. In this paper we estimate the covariance matrix by solving a constrained Lq-type regularized optimization problem. We establish the first-order optimality conditions for this problem by using proximal mapping and the subspace method. The proposed stationary point degenerates to the first-order stationary points of the unconstrained Lq regularized sparse or low-rank optimization problems. A smoothing alternating updating method is proposed to find an estimator for the covariance matrix. We establish the convergence of the proposed calculation method. The numerical simulation results show the effectiveness of the proposed approach for high-dimensional covariance estimation.