Fatigue Safety Assessment of Concrete Continuous Rigid Frame Bridge Based on Rain Flow Counting Method and Health Monitoring Data

The fatigue of concrete structures will gradually appear after being subjected to alternating loads for a long time,and the accidents caused by fatigue failure of bridge structures also appear from time to time.Aiming at the problem of degradation of long-span continuous rigid frame bridges due to fatigue and environmental effects,this paper suggests a method to analyze the fatigue degradation mechanism of this type of bridge,which combines long-term in-site monitoring data collected by the health monitoring system(HMS)and fatigue theory.In the paper,the authors mainly carry out the research work in the following aspects:First of all,a long-span continuous rigid frame bridge installed with HMS is used as an example,and a large amount of health monitoring data have been acquired,which can provide efficient information for fatigue in terms of equivalent stress range and cumulative number of stress cycles;next,for calculating the cumulative fatigue damage of the bridge structure,fatigue stress spectrum got by rain flow counting method,S-N curves and damage criteria are used for fatigue damage analysis.Moreover,it was considered a linear accumulation damage through the Palmgren-Miner rule for the counting of stress cycles.The health monitoring data are adopted to obtain fatigue stress data and the rain flow counting method is used to count the amplitude varying fatigue stress.The proposed fatigue reliability approach in the paper can estimate the fatigue damage degree and its evolution law of bridge structures well,and also can help bridge engineers do the assessment of future service duration.

Fluid Flow and Solidification Simulation in Beam Blank Continuous Casting Process With 3D Coupled Model

Based on turbulent theory, a 3D coupled model of fluid flow and solidification was built using finite difference method and used to study the influence of superheating degree and casting speed on fluid flow and solidification, analyze the interaction between shell and molten steel, and compare the temperature distribution under different technological conditions. The results indicate that high superheating degree can lengthen the liquid-core depth and make the crack and breakout possible, so suitable superheating should be controlled within 35℃ according to the simulation results. Casting speed which is one of the most important technological parameters of improving production rate, should be controlled between 0. 85 m/min and 1.05 m/min and the caster has great potential in the improvement of blank quality.

Formaldehyde degradation by UV/TiO_2/O_3 process using continuous flow mode

The degradation of formaldehyde gas was studied using UV/TiO2/O3 process under the condition of continuous flow mode. The effects of humidity, initial formaldehyde concentration, residence time and ozone adding amount on degradation of formaldehyde gas were investigated. The experimental results indicated that the combination of ozonation with photocatalytic oxidation on the degradation of formaldehyde showed a synergetic action, e.g,, it could considerably increase decomposing of formaldehyde. The degradation efficiency of formaldehyde was between 73.6% and 79.4% while the initial concentration in the range of 1.84--24 mg/m^3 by O3/TiO2flJV process. The optimal humidity was about 50% in UV/TiO2/O3 processs and degradation of formaldehyde increases from 39.0% to 94.1% when the ozone content increased from 0 to 141 mg/m^3. Furthermore, the kinetics of formaldehyde degradation reaction could be described by Langmuir-Hinshelwood model. The rate constant k of 46.72 mg/（m^3.min） and Langmuir adsorption coefficient K of 0.0268 m^3/mg were obtained.

Fluid flow in large-capacity horizontal continuous casting tundishes

The configuration of the tundish for a two-strand horizontal continuous caster was designed and optimized through water modeling. Three designs of the tundish were studied： the original tundish without any flow control devices, the tundish with a turbulence inhibitor at the bottom, and the tundish with an inlet launder and an inclined dam. The residence time, the location and size of the dead zone, and the fluid field pattern were investigated. At the same time, the asymmetry flow field and wavy inlet jet in the horizontal tundish were observed and the reasons for them were discussed. The results indicate that the mndish with an inlet launder and an inclined dam is the best of the three designs.

POWER FLOW ANALYSIS FOR THE FINITE CONTINUOUS ISOLATION SYSTEMS

A universal expression for the transmitted power to the flexible foundation via the finite continuous isolation system of asymmetry is derived where the concept of effective mobility for the coupled system with continuous contact points is put forward. On the basis of the theoretic calculation and analysis, effects of structure parameters of the system on the power flow transmission as well as on the isolation efficiency are fully investigated.

Flow of Steel in Mold Region During Continuous Casting

The particle image velocimetry （PIV） technique was used to study the fluid flow phenomena that occurred during continuous casting, using a water model with dimensions of 1 840mm× 280 mm. Two types of solidified shells, i. e. , the smooth type and the coarse type, were used to characterize the dendrite in order to simulate different liquid-solid interfacial conditions. The influence of the nozzle angle and the immersion depth of nozzle, as well as the casting speed on the flow behavior was investigated quantitatively. The results were as follows： （1） There are two large recirculations above and below the fluid jet in the mold, respectively, under the smooth interface condition. However, in the case of the dendrite solidified shell, it was found that the flow velocity of the fluid decreased and more smaller vortices appeared in the upper region of the mold. （2） The angle and the immersion depth of nozzle are two important factors affecting the flow pattern, and they are also capable of bringing about the change in the flow direction. （3） The higher the casting speed, the higher are the jet stream and the impacting point on the narrow face. However, the high casting speed causes serious fluctuation of the meniscus, and correspondingly leads to various defects.

Effects of correlative factors on the interdendritic melt flow brought by the bulge in continuous casting slabs

The effects of various factors on the flow speed of interdendritic melt were analyzed in detail in the process of continuous casting slabs. When the solid-liquid interface bends periodically, the expression of solute distribution in the columnar crystal zone was deduced, and the quantitative calculation was also made. The results show that the bulge and the interdendritic spacing are responsible for the flow speed of interdendritic melt. At the initial stage of solidification the bulge operates, and at the final stage the interdendritic spacing operates. The experimental results of macrosegregation in the slabs validated the calculated results of the flow speed of interdendritic melt, which shows that the calculated results are basically consistent with the experimental ones.

Effects of operating parameters on the flow field in slab continuous casting molds with narrow widths

Computational simulations and high-temperature measurements of velocities near the surface of a mold were carried out by using the rod deflection method to study the effects of various operating parameters on the flow field in slab continuous casting(CC)molds with narrow widths for the production of automobile exposed panels.Reasonable agreement between the calculated results and measured subsurface velocities of liquid steel was obtained under different operating parameters of the CC process.The simulation results reveal that the flow field in the horizontal plane located 50 mm from the meniscus can be used as the characteristic flow field to optimize the flow field of molten steel in the mold.Increases in casting speed can increase the subsurface velocity of molten steel and shift the position of the vortex core downward in the downward circulation zone.The flow field of liquid steel in a 1040 mm-wide slab CC mold can be improved by an Ar gas flow rate of 7 L·min^−1 and casting speed of 1.7 m·min^−1.Under the present experimental conditions,the double-roll flow pattern is generally stable at a submerged entry nozzle immersion depth of 170 mm.

POWER FLOW ANALYSIS AND APPLICATION SIMULATION OF ELECTROMAGNETIC CONTINUOUSLY VARIABLE TRANSMISSION

With the structure of two air gaps and two rotors, the electromagnetic continuously variable transmission（EMCVT） is a novel power-split continuously variable transmission（CVT）. There are two kinds of power flowing through the EMCVT, one is mechanical power and the other is electric power. In the mean time, there are three power ports in the EMCVT, one is the outer rotor named mechanical power port and the other two are the inner rotor and the stator named electric power ports. The mechanical power port is connected to the driving wheels through the final gear and the electric ports are connected to the batteries through the transducers. The two kinds of power are coupled on the outer rotor of the EMCVT. The EMCVT can be equipped on the conventional vehicle being regarded as the CVT and it also can be equipped on the hybrid electric vehicle（HEV） as the multi-energy sources assembly. The power flows of these two kinds of applications are analysed. The back electromotive force（EMF） equations are illatively studied and so the dynamic mathematic model is theorized. In order to certify the feasibility of the above theories, three simulations are carried out in allusion to the above two kinds of mentioned applications of the EMCVT and a five speed automatic transmission（AT） vehicle. The simulation results illustrate that the efficiency of the EMCVT vehicles is higher than that of the AT vehicle owed to the optimized operation area of the engine. Hence the fuel consumption of the EMCVT vehicles is knock-down.

Numerical Evaluation of Two k-εTurbulence Model for Predicting Flow and Solidification in Continuous Casting Slab

A steady three-dimensional fluid flow and solidification model was built based on CFD software by high-Reynolds-number and Lam-Bremhorst low-Reynolds-number k-ε model.During the simulation,the fixed-grid enthalpy-porosity technique was used to represent the solidification,and Darcy law was adopted to simulate the flow in mushy region.The prediction for steel flow and solidification was evaluated by the comparison of two turbulence models.It is found that both Lam-Bremhorst low-Reynolds-number and high-Reynolds-number k-ε models predict the same trend of the steel flow and temperature distribution.However,due to the effect of turbulent flow on heat transfer,the low-Reynolds-number turbulence model predicts longer penetration depth of molten steel in sub-mold region,less shell growth and higher shell surface temperature at the narrow face compared with standard k-ε model.

Validation of the numerical simulation of fluid flow in the continuous casting tundish

The 3-dimensional fluid flow in a water model of the continuous casting tundish is simulated with the k-ε two-equation turbulence model. The methods to decide the size of wall-adjacent grids and the effects of residuals and mesh size on the simulation accuracy are discussed. The current investigation concludes that the following condition should be satisfied to get accurate enough simulation results: (1) If the dimension of the domain is in the order of cubic meters, the average size of cells in the mesh system should be at least smaller than 30 mm; (2) The normalized non-scaled residual should be reached at least smaller than 10-4.

Numerical Simulation of Fluid Flow and Heat Transfer in Funnel Shaped Mold of Thin Slab Continuous Caster

Thin slab casting is used widely in the world. The control of molten steel flow and solidification in the mold is difficult due to the high casting speed and complicated configuration of the mold. Numerical simulation was carried out to study the fluid flow and heat transfer in the funnel shaped mold. The influence of nozzle design, casting speed and nozzle submersion depth on the flow and temperature fields in the mold was investigated, and guidance for selecting configurations of submerged nozzle was obtained.

Methanolysis of amides under high-temperature and high-pressure conditions with a continuous tubular reactor

The methanolysis of amides,which is widely employed in the synthetic organic chemistry,hardly occurs under mild conditions.To safely and controllably intensify the methanolysis reaction with hightemperature and high-pressure environment,a continuous tubular reaction technology is developed,whose space-time yield is over twice of that of the conventional batch reaction.The methanolysis of acetanilide is selected as the representative reaction,and the influences of temperature,pressure,reactant and catalyst concentration,and residence time on the reaction performances are systematically investigated.Taking the advantages of precise temperature and reaction time control by the tubular reactor,the kinetics of acetanilide methanolysis are determined and compared to the kinetics of acetanilide hydrolysis reaction.The tubular reaction method is also employed to test a variety of other amides to show the effects of substituents,steric hindrance,and alkalinity on the reaction rate of methanolysis.

Numerical study on three-dimensional flow field of continuously rotating detonation in a toroidal chamber

Gaseous detonation propagating in a toroidal chamber was numerically studied for hydrogen/oxygen/nitrogen mixtures. The numerical method used is based on the three-dimensional Euler equations with detailed finiterate chemistry. The results show that the calculated streak picture is in qualitative agreement with the picture recorded by a high speed streak camera from published literature. The three-dimensional flow field induced by a continuously rotating detonation was visualized and distinctive features of the rotating detonations were clearly depicted. Owing to the unconfined character of detonation wavelet, a deficit of detonation parameters was observed. Due to the effects of wall geometries, the strength of the outside detonation front is stronger than that of the inside portion. The detonation thus propagates with a constant circular velocity. Numerical simulation also shows three-dimensional rotating detonation structures, which display specific feature of the detonation- shock combined wave. Discrete burning gas pockets are formed due to instability of the discontinuity. It is believed that the present study could give an insight into the interest- ing properties of the continuously rotating detonation, and is thus beneficial to the design of continuous detonation propulsion systems.

Reagent-free determination of amikacin content in amikacin sulfate injections by FTIR derivative spectroscopy in a continuous flow system

The quantitative estimation of amikacin （AMK） in AMK sulfate injection samples is reported using FTIR-derivative spectrometric method in a continuous flow system. Fourier transform of mid-IR spectra were recorded without any sample pretreatment. A good linear calibration （r40.999, %RSDo 2.0） in the range of 7.7-77.0 mg/mL was found. The results showed a good correlation with the manufacturer＇s and overall they all fell within acceptable limits of most pharmacopoeial monographs on AMK sulfate.

An online method to determine chlorine stable isotope composition by continuous flow isotope ratio mass spectrometry (CF-IRMS) coupled with a Gasbench Ⅱ

An online method using continuous flow isotope ratio mass spectrometry （CF-IRMS） interfaced with a Gasbench Ⅱ was presented to determine chlorine stable isotope composition. Silver chloride （AgCl） was quantitatively derived from chloride by using silver nitrate （AgNO3）, and then was reacted with iodomethane （CH3Ⅰ） to produce methyl chloride （CH3Cl）. A GasBench Ⅱ equipped with a PoraPlot Q column was used to separate CH3Cl from any other gas species. Finally, chlorine stable isotope analysis was carried out on CH3Cl introduced to the IRMS in a helium stream via an active open split. The minimum amount of Cl used in this method is of the order of 1.4 μmol. Inter-laboratory and inter-technique comparisons show that the total uncertainty incorporating both the precision and accuracy of this method is better than 0.007%. Furthermore, ten seawaters sampled from different locations have a narrow δ37Cl value range from -0.008% to 0.010%, with a mean value of （0.000±0.006）%. This supports the assumption that any seawater can be representative of standard mean ocean chloride （SMOC） and used as an international reference material.

Phragmén-Lindelf and continuous dependence type results in a Stokes flow

This paper investigates the asymptotic behavior of end effects for a Stokes flow defined on a three-dimensional semi-infinite cylinder. With homogeneous Dirichlet conditions of the velocity on the lateral surface of the cylinder, solutions either grow or decay exponentially in the distance from the finite end of the cylinder. In the case of decay, the effect of perturbing the equation parameters is also investigated.

Continuous flow analysis of dissolved total phosphorus in seawater by UVK_(2)S_(2)O_(8) online digestion method

Several methods for analysis of dissolved total phosphorus in seawater were reviewed. Discussions were focused on UVirradiation and persulphate oxidation methods which are the most popular dissolved organic phosphorus determinationmethods presently. The compounds used for the phosphorus recovery test were categorized into three groups accordingto their chemical structure. It was found that low power UV irradiation can decompose POC or PC bonds efficientlybut may be inefficient for POP bonds. Heating-bath in acid condition is useful for decomposing POP bonds. Usingthe continuous flow analysis system (Auto-analyzer II), UV digestion and heating-bath, series experiments were carriedout based on the above analysis. Eleven model compounds were employed for the phosphorus recovery test and thefactors influencing the decomposition efficiency of dissolved compounds containing phosphorus were clarified. Finally,the optimal design for determination of dissolved total phosphorus in seawater based on the routine continuous flowanalysis system was presented. For the organic mono-phosphate, the recovery is more than 90% and a recovery of33%~51% was obtained for inorganic or organic polyphosphates. Up to now, this is the highest decompositionefficiency for dissolved phosphorus based on the continuous flow analysis system.

Flow and Temperature Fields in Slab Continuous Casting Molds

In order to develop super-board and super-thick slabs, the flow and temperatur fields were studied in slab continuous casting molds under different practical conditions, such as slab dimensions, with-drawing slab speed, design of nozzles, and superheat tempera-ture. The results showed that it is preferred to incline nozzle bores downwards and the submerged depth of the nozzles is best kept be-tween 250-300 mm. In addition, the solidified shell is thicker at the wide face than that at the narrow face, while the thin points alongthe wide face ekist both in the center and in the some area toward each respective end.

Modeling of unsteadiness of fluid flows and level fluctuations in thin slab continuous casting moulds

Unsteady fluid flows and level fluctuations in a thin slab continuous casting mould have significant influence on product quality. In this study, the phenomena concerning transient flow features and free surface motions were analyzed by means of the large eddy simulation （LES） software with the smagorinsky SGS model--VisualCast （VCast） II, where the Simpler algorithm on a body-fitted mesh was used to resolve governing equations. A series of water analog experiments on the fluid flow and the surface wave in the moulds of thin slab continuous casting were also performed. The results of fluid regions, middle of vortex and level fluctuation from digital simulations were identical with the results of the water analog experiments.