Practical Calculation Method Research Articles

Probabilistic Load Combination Factors of Wave and Whipping Bending Moments

Extreme values of wave and whipping bending moments are important in structural design of large containerships. Since the extreme values of these two, partially correlated processes do not occur at the same time instant and even at the same environmental conditions, it is necessary to combine them by using probabilistic load combination methods. The correlation analysis between wave and whipping bending moments is performed and a practical method for calculation of the most probable load combination factor between considered bending moments is presented. Short-term load combination factors are calculated by reconstruction of the signal from the frequency domain solution. Results are validated by comparison with model test data of the 9400-TEU containership for various sea states and speeds and heading angles. Practical regression equations for estimation of the most probable short-term load combination factor are formulated. Regression equations are then used in the computation of the long-term distribution of combined bending moment. The procedure is demonstrated on the example of the two large containerships.

Probabilistic Load Combination Factors of Wave and Whipping Bending Moments

Extreme values of wave and whipping bending moments are important in structural design of large containerships. Since the extreme values of these two, partially correlated processes do not occur at the same time instant and even at the same environmental conditions, it is necessary to combine them by using probabilistic load combination methods. The correlation analysis between wave and whipping bending moments is performed and a practical method for calculation of the most probable load combination factor between considered bending moments is presented. Short-term load combination factors are calculated by reconstruction of the signal from the frequency domain solution. Results are validated by comparison with model test data of the 9400-TEU containership for various sea states and speeds and heading angles. Practical regression equations for estimation of the most probable short-term load combination factor are formulated. Regression equations are then used in the computation of the long-term distribution of combined bending moment. The procedure is demonstrated on the example of the two large containerships.

Behaviour of steel reinforced concrete beams considering overall fire stages

Finite-element models (FEMs) for analysing the temperature field and mechanical performance of steel reinforced concrete (SRC) beams considering overall fire stages were established. This work also developed secondary programs for extracting the results of temperature and user subroutines for considering the influence of moisture at elevated temperature, steel creep at high temperature and the transformation of field variables. The results calculated using the FEMs were verified with related theoretical and experimental results. Based on the FEMs, the mechanical characteristics and parametric influences of SRC beams during the overall fire stage were analysed. Finally, practical calculation methods for the critical load level and the residual load-bearing capacity coefficient after fire were derived. The results show that, when the outer temperature drops, the temperature of the internal region keeps rising and the drop in temperature lags to some extent. The beam deflection increases further but gradually recovers after reaching the maximum deflection. For higher load levels, the time for deflection to reach the maximum and enter the recovery stage is later, and the extent of recovery is reduced. The critical load level and the residual load-bearing capacity coefficient after fire increase with a decrease in heating time or an increase in sectional dimension, section steel ratio or sectional depth-to-width ratio. The residual load-bearing capacity coefficient decreases with an increase in initial load level.

Practical Calculation Method for the Bearing Capacity at High Temperature of Concrete Filled Steel Tubular Columns Subjected to Fire

The fire resistance of concrete filled steel tubular column is usually obtained by the numerical analysis method, which is difficult to operate and not convenient in the actual civil engineering. So it is necessary to study the simplified calculation method. A large number of numerical simulation results of the temperature distribution of the section and the bearing capacity at high temperature of the concrete filled steel tubular columns are analyzed. The influences of secondary parameters are simplified. The simplified calculation method at 150 min and 180 min for the bearing capacity at high temperature of concrete filled steel tubular columns subjected to axial compression and fire is presented on the basis of comprehensive analysis of the numerical calculation results. The calculation results can be used as the basis to judge the fire resistance. It is shown by the comparison with the experimental results that the precision of the simplified calculation method can meet the requirements of engineering application.

Buckling design of steel tied-arch bridges

The structural behaviour of steel tied-arch bridges is determined by the introduction of a large compressive force. As a consequence, slender steel arches are highly sensitive to in-plane as well as out-of-plane buckling. At present, no specific buckling curves for out-of-plane buckling exist for non-linear or curved elements in the international codes and calculation methods. Hence, the buckling curves for straight columns, as determined by ECCS, are used, which leads to considerable inaccuracies in the assessment of the critical buckling load for arch bridges.This paper presents two practical calculation methods to design for the buckling behaviour of slender steel arch bridges. The first one follows the calculation method of the Eurocode, but proposes some augmented empirical formulas for the buckling length of the arches. This allows for a better representation of the out-of-plane stiffness of the arch cross section and of the wind bracings between both arches.In addition a second method is proposed, based on the use of simplified finite element models to determine the relative slenderness of the structure. Both methods are validated using results from very detailed three dimensional finite element models. Finite element models of several tied-arch bridges have been created. These models include variations of the bridge length, dimensions of the arch cross-section, boundary condition, and load type. The conclusion of these calculations is that for both of the proposed methods a higher buckling curve can be used than proposed by the code, thus resulting in a more slender bridge design.

Experimental study on hysteretic properties of SRC columns with high steel ratio

8 steel reinforced concrete (SRC) columns with the encased steel ratio of 13.12% and 15.04% respectively were tested under the test axial load ratio of 0.33-0.80 and the low-frequency cyclic lateral loading. The cross sectional area of composite columns was <TEX>$500mm{\times}500mm$</TEX>. The mechanical properties, failure modes and deformabilities were studied. All the specimens produced flexure failure subject to combined axial force, bending moment and shear. Force-displacement hysteretic curves, strain curves of encased steels and rebars were obtained. The interaction behavior of encased steel and concrete were verified. The hysteretic curves of columns were plump in shapes. Hysteresis loops were almost coincident under the same levels of lateral loading, and bearing capacities did not change much, which indicated that the columns had good energy-dissipation performance and seismic capacity. Based on the equilibrium equation, the suggested practical calculation method could accurately predict the flexural strength of SRC columns with cross-shaped section encased steel. The obtained M-N curves of SRC columns can be used as references for further studies.

A Network Security Risk Computation Approach Based on Attack Graphs

At present, with the rapid development of computer technology and network communication technology, and the Internet computer network application is increasingly wide and deep. Explore the scientific, reasonable and practical calculation method of the network security risk has become a hotspot in the research of network security, and a lot of research results have been reached. But because of the complexity of the network security risk calculation, there are still many challenges. Based on the shortcomings of the traditional network security risk calculation method, this paper mainly studies network security risk calculation method based on attack graph.

A semiclassical adiabatic calculation of state densities for molecules exhibiting torsion: application to hydrogen peroxide and its isotopomers

A practical computational method is discussed for obtaining the rotational–vibrational molecular state densities of molecules with large amplitude torsional degrees of freedom (DoFs). This method goes beyond the traditional harmonic oscillator/rigid rotor or separable hindered rotor approximations in that it includes coupling between the torsion, the remaining vibrational modes, and the overall rotation. The method is based on the vibrationally adiabatic approximation whereby the torsional motion is assumed to be slow compared to the remaining vibrational DoFs although the nonseparability may be large. The torsional coordinate therefore parameterizes the rotational constants and the effective vibrational potential. A semiclassical method is then introduced to calculate the total state density in which the torsion is treated classically while the remaining coordinates are treated quantum mechanically. The method is also formulated for reactive problems in which the density of states is parameterized by a second large amplitude degree of freedom, the reaction coordinate. The performance of the method is assessed using the dissociation reaction of the hydrogen peroxide molecule and its isotopomers. It is found that the method performs well based on numerical tests. The torsional nonseparability is found to yield errors of factors of 2–3 in the statistical rate coefficient when compared with results of traditional separable models.

Practical Calculation of Cable-Stayed Arch Bridge Lateral Stability

A long-span cable-stayed arch bridge is a new form of bridge structure that combines features of cable-stayed bridges with characteristics of arch bridges. In the present study, we derived a practical calculation method for the lateral destabilization critical loading of cable-stayed arch bridges during the construction process based the energy principle. The validity of the method was verified with an example. The calculation method provides a quick and efficient way to evaluate the lateral stability of a cable-stayed arch bridge and a concrete filled steel tubular arch bridge during the construction process.

Effects of temperature variations on safety of reinforced concrete structures during construction

Since 1960s, many research works on the reinforced concrete structure have been published and some concise and practical calculation methods for safety control during construction have been achieved. The reinforced concrete structure during construction is a time-dependent structure which consists of a partly completed structure and a formwork-shore system. Experience shows that the most critical condition of the time-dependent structure may happen when the formwork-shore system is partly removed or reset and accidents may occur. In the present paper, effect of ambient temperature variation between day and night is considered, new structural models for reinforced concrete frames, slab-column systems and shear wall structures are proposed, and a new software named Safety Analysis During Construction Considering Temperature (SACT) is also introduced. Compared with on-site measurements, the software SACT is validated for application on construction site.

A New Approach for Calculation of PID Parameters with Model Based Compact Form Formulations

PID controller is a popular control method still widely used in process industry. In literature there are model/non-model based calculation methods for PID parameters. However, a model based analytic formulation in compact form in discrete time has not been come across yet. This study presents a new approach for calculation of PID parameters with model based analytic formulation (MBCF), which is presented uniquely in this paper, in compact form, in discrete time. Furthermore, a procedure for implementation of the proposed formulas is given in four stages. The formulations in related literature for PID parameter calculation are all derived for continuous time. Therefore, extra transformations are required for a discrete time design. The proposed MBCF formulation method reduces extra calculation burden and simplifies calculation complexity. Moreover, this method provides a direct calculation method for digital PID controller design in discrete time. The derived expressions in this study also provide a fast, easy-implemented, and practical PID parameter calculation method for all field researchers and application engineers. The validation of proposed MBCF formulations are comparatively proved with the simulations and the real time application results. DOI: http://dx.doi.org/10.5755/j01.eee.20.3.4415

Engineering calculation of dynamic impedances and starting characteristics for high-voltage induction motors

Starting characteristics and dynamic impedances are the key parameters for the research of high-voltage induction motor. The measurement of starting characteristics and dynamic impedances for high-voltage induction motors can present problems for both manufacturers and users, so a practical and feasible calculation method is necessary. In order to facilitate the engineering application, this paper presents a set of useful calculation method for motor transient torque, current, and impedances. In the calculation, the influence of dynamic characteristics and impedances on each other, which are often neglected in previous calculation, is considered. So the influence of impedances on the characteristic curves can be analyzed more accurately using this method. Based on the earlier analyses, this paper further studies the influence of different start-up voltages on the stator leakage reactance. Finally, through the analysis and calculation results of many motors, it can be verified that only when the relation between starting characteristics and dynamic impedances is considered in calculation process will the results be better in line with the actual value. The algorithm is suitable for engineering use. Copyright © 2014 John Wiley & Sons, Ltd.

Finite Element Analysis of Concrete Filled Double-Skin (CHS Inner and CHS Outer) Steel Tubes under Lateral Impact

As a new type of steel-concrete composite structure, Concrete-Filled Double Skin Steel Tubes not only have the advantages of the traditional steel concrete structures, but also carried out cross-section and great bending stiffness. This structure is widely used in high-rise buildings, bridges and power facilities. During the whole life cycle, concrete-filled double skin steel tubes may inevitably suffer from various impact loads. In current the research about steel-concrete composite structure focuses on the performance about axial compression, bias, bending, and low cyclic loads. but the research about it under lateral impact is equally import. In this paper, the behavior of concrete-filled double skin steel tubes (CFDST) with fixed boundary condition was analyzed by Finite Element Analysis method ,to analyze the destruction modal, impact force (F) , deflection () as well as other dynamic responses of CFDST under different lateral impact energy. The work mechanic and full range analysis of concrete filled double steel tube under lateral impact were analyzed. The results show that the damage of CFDST with fixed boundary condition under lateral impact is in ductile manner. Analyzed the whole process of the dynamic response basically , laid the foundation for further parametric analysis and practical calculation method.

The Solution of an Integer Problem Based on Geometric Method

This paper studies the integer solution of the Markowitz mean-variance model. To avoid solving the quadratic equation with constraints directly, it uses geometric linear approximate method, and gives a practical and effective calculation method. Then it conducts the corresponding calculations regarding the real data, and reaches an optimal solution while the time of calculations is largely reduced, compared to the direct way and the algebraic approach.

Практический метод расчета осадок фундаментов с учетом деформационной анизотропии грунтов основания

Практический метод расчета осадок фундаментов с учетом деформационной анизотропии грунтов основания

Development of a modified sampling and calculation method for isotope plasma clearance assessment of the glomerular filtration rate in patients with cirrhosis and ascites

The aim of this study was to identify a practical sampling regimen and calculation method that could be used to measure the glomerular filtration rate in patients with ascites using plasma sampling. Thirteen potential liver transplant patients with cirrhosis and ascites were injected with Cr-51 ethylenediaminetetraacetic acid, and plasma samples were obtained at up to 16 time points for each patient. Reference clearance values were calculated using the area under the plasma clearance curve, which was calculated using all the available data points. Clearance calculations were then performed using three and four data points from each patient and three different calculation methods to identify a sampling regimen and calculation method that yielded good agreement with the reference values. The reference clearances ranged from 6 to 80 ml/min. Sampling at 2, 4, 8 and 24 h and calculation of the area under the plasma clearance curve using a log-linear trapezoidal rule with extrapolation to zero and infinity yielded a relative root mean square difference from the reference of less than 7%. This method for measuring glomerular filtration rate in patients with cirrhosis and ascites was found to be more accurate than the slope-intercept technique and is a practical alternative to urine collection.

Practical Use and Calculation of CCT and Duv

Correlated color temperature (CCT) is often used to represent chromaticity of white light sources, but chromaticity is two-dimensional, and another dimension, the distance from the Planckian locus, is often missing. Duv is defined in ANSI C78.377 for this purpose but is not yet widely used. In this article, the use of a combination of CCT and Duv is proposed as an intuitive expression of chromaticity of white light sources for general lighting. In addition, this article presents practical calculation methods to calculate CCT and Duv, having sufficient accuracy, within an error of 1 K, in a wide range of chromaticity, from 1000 to 20,000 K in CCT and −0.03 to 0.03 in Duv.

Design and Calculation of the Cam Mechanism Profile Curve Based on MATLAB

This paper discusses the design and calculation thinking of the cam mechanism profile curve, using MATLAB method, programmed the design and calculation of the cam mechanism profile curve , solved the large amount and complicated calculation data processing in design of the cam mechanism profile curve. Provided a practical calculation method of the cam design to the factory.

Study on Vacuum Degree of Mechanical Cleaning System for Product Oil Tank

A practical calculation method to determine the vacuum degree of a mechanical cleaning system is proposed mainly based on the theories of fluid mechanics. The system for cleaning of product oil tanks is operated relying on vacuum suction and simplified without heating section comparing with the system for crude oil tanks. It shows that the determination of vacuum level depends on two factors: to overcome the frictional resistance of suction tank's inlet pipes and to meet the net positive suction head (NPSH) required for a centrifugal pump fixed on outlet pipes of a suction tank. So, the higher and lower limits of vacuum degree can be found. The calculating method of vacuum degree is proved in a real system.

Analysis of thermal energy demand and saving in industrial buildings: A case study in Slovakia

Energy saving through incorporation of automation techniques in buildings is usually too complicated and costly and it is necessary to protect environment. Presently, there is no single directive and standard method to estimate and validate the energy consumption process in industrial buildings for heating to maintain a comfortable environment for working. The purpose of this study was to find and develop a practical method for analysis and calculation of thermal energy consumptions and saving in buildings. The energy required for heating in an industrial building in Kosice, Slovakia was studied using measurements, calculations and dynamic simulations. The energy needed for heating was determined according to the Slovakian and Austrian national standard methods using the simplified calculation method that is applied for non-residential buildings and the ESP-r and BuilOpt-VIE simulation programs. The repeatability of the experimental data and possibility of rapid assessments in an optimized process using these methods were studied. It was found that the clear definitions of the heat consumers inside the building, including all machinery and occupants, are very important for evaluation of energy needed for heating. Using dynamic simulation, it is not possible to reproduce actual temperatures at various heights without prior knowledge of the exact functionality of the heating and cooling systems. The simulations results also indicated that integration of lighting, heat recovery and door opening automation can significantly reduce the heating energy consumption.