Maximum Design Values Research Articles

Effects of Jack Thrust on the Damage of Segment Lining Structure during Shield Machine Tunnelling

Constructing a tunnel with a large longitudinal slope and a small-radius sharp curve is challenging. During the construction process, it necessitates a series of intricate operations, including adjusting the horizontal and vertical posture of the shield machine, controlling the tunnelling thrust, and consistently ensuring the appropriate over-excavation amount inside and outside of the turn. Improper operations can easily induce undue stress on the segments. This study establishes a finite element numerical model of lining segments subjected to jacking force under various construction conditions. The concrete damage plasticity (CDP) constitutive model was used to characterize the mechanical behavior of concrete under load. The mechanical characteristics and damage behavior of segments under construction conditions, such as significant thrust escape, vertical attitude adjustment of the shield machine, excavation in soft and hard interbedded strata, line turning, sudden failure of the propulsion system, and eccentricity of brace boots, were analyzed. The results revealed that, when advancing according to the maximum thrust design value (50 MPa), cracks in the tensile plastic damage zone near the brace boot plate and the edges of the segment can develop. This can lead to localized corner failure of the concrete at the lining’s edge. Therefore, it is recommended that the jack’s thrust value should not surpass 30 MPa. Maintaining the usual uneven jack thrust state of shield tunnelling along the design axis is unlikely to result in segment concrete cracking. Damage to the segment caused by the eccentricity of the brace boot plate is the most severe; hence, avoiding the eccentricity of the brace boot plate during construction is crucial. The findings of this research can guide the control of jack thrust during shield tunnelling construction and offer insights into the design of segment parameters.

Optimization of supply air flow and temperature for VAV terminal unit by artificial neural network

The purpose of this paper is to optimize the supply air flow rate and temperature of the variable air volume (VAV) terminal unit by artificial neural network (ANN). In general, the setpoint of the VAV terminal unit are supply air flow rate and supply air temperature. These setpoints are determined by the design value, and are calculated by the maximum indoor heating/cooling load and the ventilation requirements. The setpoints calculated based on the design value does not cause any problems in maintaining the indoor environment. However, energy consumption cannot be optimized because it is based on the maximum design value. In order to improve the existing control method, it is important to apply the setpoints according to the real time indoor conditions. The real time indoor condition can be utilized for control through prediction model. In this study, the indoor load, indoor air quality and energy consumption were predicted and used for VAV system control. In addition, the predictive model was developed with the ANN algorithm, and the process of selecting input data and optimizing the predictive model was performed. The performance of the ANN based optimal control algorithm (suggested CASE) for the VAV terminal unit in the target building was compared with those of the dual maximum control algorithm (existing CASE), one of the VAV terminal unit control algorithms. The comparison of heating season showed that the ANN based control algorithm of VAV terminal unit reduced 16.7% of supply fan energy consumption and 19.5% of reheat coil energy consumption compared to the existing CASE using the fixed setpoint.

Температурний режим грунтових масивів Як геологічний вплив на основи будівель

Проаналізовані результати спостережень за температурою ґрунту на 11 метеостанціях України. Розроблена методика визначення мінімальних та максимальних розрахункових значень температури ґрунту. Визначені розрахункові значення температури ґрунту для глибин до 3,2 м, проаналізовані та описані їх залежності від глибини й періоду повторюваності. Результати дослідження можуть бути використані в теплотехнічних розрахунках підземних частин будівельних об’єктів.

A Simulation Study of the Emergency Double-Row Micropile Reinforcement of the Xituo Landslide

This paper studies the suitability of a double-row anti-slide micropile solution for the emergency reinforcement project of the Xituo landslide. The FLAC3D program was used to simulate the stability of the landslide before and after micropile installation. Several key parameters were monitored in the simulation such as the landslide displacement, the shear strain rate at the slip surface, as well as the bending moments and the shear forces exerted on the piles. Both the displacement graph and the shear strain rate cloud map of the landslide before reinforcement indicate that the Xituo landslide is in an unstable state and tends toward accelerated collapse. After the double-row anti-slide micropiles were installed, the displacement of the slope toe gradually stabilized, and the displacement on the river side of the highway was significantly reduced. Moreover, the shear strain rate cloud diagram at the location of the micropiles developed upward, and the shear strain rate was small. These changes indicate that the double-row anti-slide micropiles could effectively restrain further deformation and damage because of the Xituo landslide. Furthermore, the simulated maximum shear forces exerted on the piles, 115.5 and 75.8 kN, are much lower than the maximum micropile design value of 260 kN. The simulated maximum pile body bending moments, 3173.8 and 1170.0 kNm, also fall below the recommended maximum value of 4500 kNm. Therefore, double-row anti-slide micropiles are an effective and practical solution for stabilizing the Xituo landslide.

Numerical Investigation of Water Film Evaporation with the Countercurrent Air in the Asymmetric Heating Rectangular Channel for Passive Containment Cooling System

Passive containment cooling system (PCCS) is an important passive safety facility in the large advanced pressurized water reactor. Using the physical laws, such as gravity and buoyancy, the water film/air countercurrent flow is formed in the external annular channel to keep inside temperature and pressure below the maximum design values. Due to the large curvature radius of the annular channel, one of the short arc segments is taken out, as a rectangular channel, to analyze the main water film evaporation heat transfer characteristics. Two numerical methods are used to predict the water film evaporative mass flow rate during the heat transfer process in the large-scale rectangular channel with asymmetric heating when the water film temperature is not saturated. At the same time, these numerical simulation results are validated by the experiment which is set up to study water film/air countercurrent flow heat transfer on a vertical back heating plate with 5 m in length and 1.2 m in width. It is shown that the maximum deviation between numerical simulation and experiment is 30%. In addition, the influences on these parameters, such as heat flux, evaporative mass flow rate, and water film thickness, are evaluated under the different tilted angles of the rectangular channel and horizontal plane, water/air inlet flow rates, water/air inlet temperatures, heating surface temperatures, and air inlet relative humidities. All these results can provide a good guidance for the design of PCCS in the future.

Evaluation of High Resistance Connection in Automotive Application

<div class="section abstract"><div class="htmlview paragraph">Electrical connections have a normal operational temperature range. A high resistance, such as a poor connection, in an electrical circuit has been reported to cause a temperature increase exceeding normal operational range at the connection.</div><div class="htmlview paragraph">This study measures the temperature increase in a typical automotive bolted battery cable connection with low to zero torque values and simulated high resistance under different load conditions. The torque is changed from maximum design value to 0 Nm and the temperature increase at the connection is measured. The high resistance connections, manually created by adjusting the contacts, are tested for several power loss values at the connection. The temperature rise under these conditions at the connection is measured and subsequently recorded.</div><div class="htmlview paragraph">The maximum temperature increase at the bolted cable connection recorded at low torque values including 0 Nm torque compared to the maximum typical design value of 17 Nm is 10.5 °C. The maximum temperature increase for the high resistance bolted connection is a function of the power loss and the voltage drop at the connection.</div></div>

Experimental evaluation of the fatigue life of hydraulic gate cast iron rollers

AbstractFixed‐wheel gates with wheels mounted on both sides that roll on roller path plates are used in both emergency intake gates and spillway gates in hydrogenerating stations. Environmental corrosion along with high wheel loads cause differences in the profile of the roller path surface. Combined with the relatively high torsional stiffness of the gate end girders, a condition of wheel load redistribution occurs where some wheels are relieved of load while others are loaded beyond their maximum design values. Failure of one wheel could jeopardize the overall operation of the gate. Furthermore, frequent operation of these gates result in changes in the stress profile in both wheels and roller paths that, potentially, could lead to failure. Currently, design guidelines for gate wheels and roller paths do not consider the fatigue life of these elements. Research‐based evidence is provided to support changes to these guidelines.

Geometallurgical Studies on Gold Ore for Enhanced Comminution and Leaching

Many gold processing plants are experiencing challenges as mining pits are becoming deeper, rocks are getting harder and more complex polymetallic and refractory ores are being encountered. The variations in the characteristics of ores lead to deviations from the established parameters, and these affect gold extraction efficiency. This paper presents a study where geological characteristics of the ore types from some mining pits were used to ascertain the influence of ore blends on improving the performances of comminution and leaching circuits. To achieve this, mineralogical, comminution, gravity recoverable gold and leaching investigations were conducted on fresh and weathered ore samples and their blends. Mineralogical study showed that the main rock types associated with the mine pits were dolerite, phyllites, conglomerates and sandstone. The dominant minerals were quartz, plagioclase, with traces of pyrites. The Crushability Work Indices of the rocks were between 30 and 37 KWh/t, which are generally higher than the maximum design value of 31.9 kWh/t, and this situation will pose throughput challenges in that section. The Bond Ball Mill Work Indices of the blends tested were between 16.4 kWh/t and 9.6 kWh/t and a blend ratio of 85% fresh and 15% weathered was found to have a Bond Ball Work Index almost equal to the design value of 14 kWh/t. With gold assays of 2.5 g/t for dolerite, 2.1 g/t for phyllite, 3.7 g/t for sandstone and 3.4 g/t for conglomerate, the gravity recoverable gold was in the order of sandstone 36% > phyllite (31.5%) > dolerite (29.5%) > conglomerate (18%). The overall gold recoveries were in the sequence of conglomerate (95%), sandstone (94%), phyllite (92%) and dolerite (87%). This information could be utilised in developing a proactive plant operations strategies for an operating plant in order to ultimately manage the plant and enhance achievement of set targets. Keywords: Geometallurgy; Ore Blends; Characterisation; Communition Circuit Performance; Gold Recovery

Simulation of hydrogen distribution and effect of Engineering Safety Features (ESFs) on its mitigation in a WWER-1000 containment

In this study, thermal–hydraulic parameters inside the containment of a WWER-1000/v446 nuclear power plant are simulated in a double-ended cold leg accident for short and long times (by using CONTAIN 2.0 and MELCOR 1.8.6 codes), and the effect of the spray system as an engineering safety feature on parameters mitigation is analyzed with the former code. Along with the development of the accident from design basis accident to beyond design basis accident, the Zircaloy–steam reaction becomes the source of in-vessel hydrogen generation. Hydrogen distribution inside the containment is simulated for a long time (using CONTAIN and MELCOR), and the effect of recombiners on its mitigation is analyzed (using MELCOR). Thermal–hydraulic parameters and hydrogen distribution profiles are presented as the outcome of the investigation. By activating the spray system, the peak points of pressure and temperature occur in the short time and remain below the maximum design values along the accident time. It is also shown that recombiners have a reliable effect on reducing the hydrogen concentration below flame propagation limit in the accident localization area. The parameters predicted by CONTAIN and MELCOR are in good agreement with the final safety analysis report. The noted discrepancies are discussed and explained.

Studies of the Core Conditions of the Earth and Super-Earths Using Intense Ion Beams at FAIR

Abstract Using detailed numerical simulations, we present the design of an experiment that will generate samples of iron under extreme conditions of density and pressure believed to exist in the interior of the Earth and interior of extrasolar Earth-like planets. In the proposed experiment design, an intense uranium beam is used to implode a multilayered cylindrical target that consists of a thin Fe cylinder enclosed in a thick massive W shell. Such intense uranium beams will be available at the heavy-ion synchrotron, SIS100, at the Facility for Antiprotons and Ion Research (FAIR), at Darmstadt, which is under construction and will become operational in the next few years. It is expected that the beam intensity will increase gradually over a couple of years to its maximum design value. Therefore, in our studies, we have considered a wide range of beam parameters, from the initial beam intensity (“Day One”) to the maximum specified value. It is also worth noting that two different focal spot geometries have been used. In one case, a circular focal spot with a Gaussian transverse intensity distribution is considered, whereas in the other case, an annular focal spot is used. With these two beam geometries, one can access different parts of the Fe phase diagram. For example, heating the sample with a circular focal spot generates a hot liquid state, while an annular focal spot can produce a highly compressed liquid or a highly compressed solid phase depending on the beam intensity.

Functional Characteristics Improvement of Metal Transformable-Volume Structures for Space Applications

Under conditions of the influence of space environment factors, the thin-walled load-carrying transformable-volume structures are subjected to volumetric deformation and long-time exposure to external loads, close to maximum permissible design values. The required functional properties of transformable-volume structures are ensured on the basis of applying surface engineering methods, whose effectiveness is difficult to confirm as there is no possibility to reproduce the space environment factors complex under the terrestrial conditions. The method for verification of applied technologies regarding the modification of surface properties was described. It was based on the comparison of finite-element and experimental-computational models of displacements in equivalent fragments of the transformable volume structures surface. Qualitative and quantitative evaluation of methods is given, allowing changing the rigiditystrength strength characteristics of transformable-volume structures for space applications without alteration of their mass and compactness.

Study of Deformations in a Large-Capacity Oil Storage Tank in the Presence of Subgrade Inhomogeneity Zones

Characteristics of a joint action of a subgrade and a large 50000 m3 capacity storage tank have been overviewed. The maximum allowable values of the RVSPK-50000 base immersion in the presence of the inhomogeneity zone have been determined given the stiffness of metal structures. To simulate the inhomogeneity zone we applied the Drucker–Prager model – a linear elastoplastic material implemented in the finite element software package ANSYS. The dependences of the maximum design value of the outer tank bottom contour immersion on the inhomogeneity zone sector length have been obtained (in the range of 10 to 95 meters). It has been found that 95% of all cases of uneven immersion occurring in practice fall within this range according to data on diagnostics of 40 vertical steel tanks.

The Research of Slurry Foaming of Wet Flue Gas Desulfurization System of Steel Works

This paper focus on the analysis of the slurry foam of the sinter band plant Wet Flue Gas Desulfurization (WFGD) process, and put forward suggestions according to the actual conditions of the Steel Works. The experimenter compared the actual operating parameters of slurry and system design parameter. Then found out the main incentive to form foam on top of the absorber’s slurry tank. This paper analyzed the major constituents of overflow foaming of WFGD system. Analysis results indicated that it is the same composition of byproducts gypsum of WFGD. So the experiment focus on the research of slurry constituents of the absorber. The result of basic data analysis shows that the slurry density of absorber is 1.25Kg/L which exceeds the maximum design value i.e.1.15Kg/L, and the Chloride concentration is 80000mg/L which exceeds the maximum design value i.e. 15000mg/L. The supernatant of slurry is formed of colloidal solution and the solid percentage of supernatant slurry is 10.64% (Weight percentage). Meanwhile the supernatant slurry shows Tyndall phenomenon significantly, and the remaining solution indicators are much higher than the design value. For identification purpose, the experimenter had an experiment about desulfurization slurry and found the relationship among solid content, supernatant concentration, foaming ability and foaming stability. Experimental results show that the foaming ability get strong first and then get weak with the increase of the solid content and the foaming ability get weak gradually with the decrease of the concentration of Mg2+and Cl-. The slurry almost has no foaming when the solid content is less than 10% and the concentration of Mg2+ less than 1000mg/L and the concentration of Cl- less than 20000mg/L.

Estimation of thermoelectric and mechanical performances of segmented thermoelectric generators under optimal operating conditions

The conversion efficiency is the most important indicator describing the thermoelectric performance of thermoelectric (TE) devices. Under large operating temperature difference, the efficiency can be enhanced by the fabrication of segmented thermoelements structure. For running safety, the thermomechanical behavior of TE devices must be considered. In this paper, a 3D finite element model is established to estimate the TE and mechanical performance of the segmented thermoelectric generator (STEG) under optimal operating conditions. The effects of the segment lengths on the TE conversion efficiency and the maximum stress level of TE materials are examined at a given operating temperature. And for different operating temperatures, the maximum conversion efficiency and maximum stress level of TE materials are also investigated, individually. By the mechanical strength evaluation and mechanical reliability analysis, the TE behaviors of STEG are verified. The results indicate that, for a given operating temperature, some segmented cases do not satisfy the strength requirements, and the theoretical maximum efficiency does not equal to the actual optimal one; for different operating temperatures, the STEG cannot always achieve the maximum design value of conversion efficiency. These findings will have some significant positive impact on the optimal design and practical application of the STEG.

Modeling of Leachate Collection Systems with Filter Separators in Municipal Solid Waste Landfills

AbstractA numerical model is used to estimate the service life and clogging of gravel leachate drainage layers with a filter separator layer, such as those used in municipal solid waste landfills. A filter separator layer between the waste and the drainage layer is shown to reduce the leachate strength entering the gravel drainage layer and to extend the time that it takes to clog the drainage layer to the point when the leachate level exceeds the maximum design value (the service life). The filter layer is shown to have a far more significant effect in extending the service life when pea gravel (dg=6 mm) is used in the drainage layer, and less effect when coarse gravel (dg=27 mm) is used in the cases examined, although most of the benefit of a filter separator layer was achieved by using a 3-mm-thick needle-punched nonwoven geotextile. This geotextile may be sufficient for many practical purposes that are similar to those examined. The results from modeling leachate collection systems with filter separ...

RFX-mod wall conditioning by lithium pellet injection

Plasma–wall interaction is one of the most important issues that present magnetic confinement devices have to face. In the RFX-mod reversed field pinch experiment plasma–wall interaction has become a hard point increasing plasma current up to the RFX-mod maximum design value of 2 MA, since in this case local power deposition can be as high as 10 MW m−2. Since the first wall of RFX-mod is entirely covered by graphite tiles different techniques have been tested to control hydrogen wall influx: He glow discharges cleaning, He discharges at high plasma currents, wall boronization and baking. With the best results obtained by boronization, at high plasma currents all such techniques improve the situation but do not allow a complete and stationary hydrogen influx reduction. Furthermore, in the presence of localized high power load the wall still responds providing very high influxes. In order to improve this situation wall conditioning by lithium has been tested. As a first lithization method to deposit a controllable amount of lithium on the wall, a room temperature pellet injector has been used (maximum pellet diameter of 1.8 mm and maximum length of 5 mm). Lithium coatings with a theoretical thickness of about 10 nm have been applied both to clean graphite tiles and over boronized ones. Lithization demonstrated to be effective in lowering hydrogen wall recycling to a value smaller than that of boronized graphite, with the effect lasting 20–30% more than in the boronized case. Compared with boronization, lithization slightly improves (by about 30%) particle confinement time and also clearly affects edge particle transport providing a lower edge density and more peaked density profiles. Lithization also reduces carbon content by about 10% over boronization but still no clear improvement has been observed in terms of energy confinement. Similar results have been obtained performing lithization over boronized graphite.

ANALYSIS OF THERMODYNAMIC PROPERTIES OF CONDENSED CARBIDES

An approximate generalized equation of temperature dependence of Gibbs energy change in atomization reactions of condensed silicides is obtained, subject to the number of atoms contained in silicides and design boiling temperatures. Deviation of maximum design value from average was not more than 10 % for 16 examined silicide compounds. This gives rise to use the obtained technique for: similar data checking from other information sources; for approximate prediction of thermodynamic properties of previously unsearched silicide compounds.

Factored Modal Combination for Evaluation of Earthquake Load Profiles

To accurately predict the inelastic earthquake response of a structure by pushover analysis, the prescribed load profiles should be consistent with the actual force profiles which develop maximum design values during the time-history response of the structure. In the present study, a new modal combination method, factored modal combination (FMC), was developed to predict the earthquake load profiles of building structures affected by higher dynamic modes. In the FMC, multiple story load profiles are predicted by combining the modal spectrum responses multiplied by the modal combination factors. Based on the results of parametric studies on moment-resisting frames and walls, the modal combination factors were defined according to the hierarchy of each mode affecting the dynamic responses of structures. The FMC was applied to prototype buildings with and without vertical irregularity. The results showed that the FMC predicted the actual story load profiles which developed during the elastic and inelastic time-history responses of the structures.

220 既設炉への水冷ストーカ適用によるトータルコストの低減化(焼却・溶融・ガス化溶融,資源循環・廃棄物処理技術)

Calorie of the waste to be burnt has been increased comparing to the original design value at an existing MSW incineration plant. Incineration capacity and quality of the flue gas exhausted from the plant could be improved by adapting of Water-cooled stoker system with keeping the flue gas amount within the maximum original design value. By the improvement of the plant, total expenses of the waste treatment operation were reduced including of the initial modification cost. The overall improvements of the facilities by adapting Water-cooled stoker and other related systems contribute to reduce the maintenance cost very much and could be confirmed as a technology to be able to satisfy both in environmentally and economically.

Chapter 9: The FTU Machine - Design Construction and Assembly

The main design features and guidelines for the construction of the 8-T cryogenically cooled Frascati Tokamak Upgrade (FTU) are presented. The main features include the very compact toroidal magnets based on the concept of the “Bitter” type of coil with wedge-shaped turns, utilized for the first time for the Alcator A and C magnets, and the original configuration of the vacuum vessel (VV) structure, which is fully welded in order to achieve the required high strength and electric resistivity. The present toroidal limiter has been installed following several years of operation, and this installation has required the development of specific remote-handling tools. The toroidal limiter consists of 12 independent sectors made of stainless steel carriers and molybdenum alloy (TZM) tiles. The main fabrication processes developed for the toroidal and poloidal coils as well as for the VV are described. It is to be noted that the assembly procedure has required very accurate machining of all the structures requiring several trials and steps. The machine has shown no problem in operating routinely at its maximum design values (8 T, 1.6 MA).