• Title, Summary, Keyword: Regular Load Reduction

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Mechanical characteristic of overhead transmission lines by forest fires (화염에 노출된 가공송전선의 기계적.재료적 특성 검토)

  • Kang, J.W.;Jang, T.I.;Kim, B.K.;Park, C.G.;Bang, H.K.
    • Proceedings of the KIEE Conference
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    • pp.339-341
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    • 2002
  • The remaining life of ACSR exposed to the atmosphere for a long period may rely on deterioration caused by environmental indices such as atmospheric corrosion, galvanic corrosion, crevice corrosion and fatigue corrosion. One of reduction of useful life in overhead transmission lines built on the ridge of mountain is often caused by forest fires. This paper deals with investigation of strength deterioration performance of ACSR due to fires through several testing and analyzing data for both tension load and material analysis. Test samples are ACSR $480[mm^2]$ conductors, which are artificially fired to regular durations. As a result, it can be verified that tension load of ACSR are reduced by increasing fro duration. Hence, it is obvious that ACSR due to forest fires may lead to mechanical deterioration.

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Noise Reduction Technique by Three-Points Ensemble Averaging in Uroflowmetry (삼점 신호 평균기법에 의한 요속신호의 잡음 축소 기법)

  • Choi, Seong-Su;Lee, In-Kwang;Lee, Sang-Bong;Park, Jun-Oh;Lee, Su-Ok;Cha, Eun-Jong;Kim, Kyung-Ah
    • The Transactions of The Korean Institute of Electrical Engineers
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    • v.58 no.8
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    • pp.1638-1643
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    • 2009
  • Uroflowmetry is a convenient clinical test to screen the benign prostatic hyperplasia(BPH) common in the aged men. A load cell is located beneath the urine container to measure the weight of urine. However, it is sensitive to the impact applied on the bottom of the container by the urine stream, which could be a noise source lowering the reliability of the system. With this aim, our study proposed a noise reduction technique by computing ensemble average of the weighted signals that were acquired from three-load cells forming a regular triangle beneath the urine container. Simulated urination experiment was performed with three different collection methods, all of which demonstrated significant noise reduction by ensemble averaging. Furthermore, the best results can be obtained without any special urine collection devices. Thus, our novel method can be usefully applied to uroflowmetry for enhancing measurement in terms of accuracy and reliability.

A Study on Forecasting Method for a Short-Term Demand Forecasting of Customer's Electric Demand (수요측 단기 전력소비패턴 예측을 위한 평균 및 시계열 분석방법 연구)

  • Ko, Jong-Min;Yang, Il-Kwon;Song, Jae-Ju
    • The Transactions of The Korean Institute of Electrical Engineers
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    • v.58 no.1
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    • pp.1-6
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    • 2009
  • The traditional demand prediction was based on the technique wherein electric power corporations made monthly or seasonal estimation of electric power consumption for each area and subscription type for the next one or two years to consider both seasonally generated and local consumed amounts. Note, however, that techniques such as pricing, power generation plan, or sales strategy establishment were used by corporations without considering the production, comparison, and analysis techniques of the predicted consumption to enable efficient power consumption on the actual demand side. In this paper, to calculate the predicted value of electric power consumption on a short-term basis (15 minutes) according to the amount of electric power actually consumed for 15 minutes on the demand side, we performed comparison and analysis by applying a 15-minute interval prediction technique to the average and that to the time series analysis to show how they were made and what we obtained from the simulations.

Experimental Study on Friction Characteristics of Pb-free Pin Bushing for an Internal Combustion Engine (내연기관용 무연 핀부싱의 마찰특성에 관한 실험적 연구)

  • Kim, Chung-Kyun;Oh, Kyoung-Seok
    • Tribology and Lubricants
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    • v.23 no.6
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    • pp.306-311
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    • 2007
  • This paper presents the friction characteristics of pb-fres pin bushing bearings for an automotive gasoline engine. The external load is 100 N to 600 N and the speed of the pin bushing bearing is 1000 rpm to 3000 rpm against the rubbing surfaces. And the contact modes of rubbing surfaces between a piston pin and a pb-free pin bushing specimen are a dry friction, an oil lubricated friction and a mixed friction that is starved by a lack of engine oil. Two influential factors of a contact rubbing modes and a material property are very important parameters on the tribological performance of a friction characteristic between a piston pin and a pb-free pin bushing. The experimental result shows that the pin bushing speed of 2000 rpm shows a typical oil film lubricated sliding contact mode in which means that as the applied load is increased, the friction loss is increasing. But other contact mode depending on the speed and the load may affect to the fiction coefficient without a regular and uniform trend. In summary, the oil lubricated rubbing surface definitely decreases a running-in period in short and increase oil film stiffness, and this may leads the reduction of a friction loss.

Effect of internal angles between limbs of cross plan shaped tall building under wind load

  • Kumar, Debasish;Dalui, Sujit Kumar
    • Wind and Structures
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    • v.24 no.2
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    • pp.95-118
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    • 2017
  • The present study revealed comparison the pressure distribution on the surfaces of regular cross plan shaped building with angular cross plan shaped building which is being transformed from basic cross plan shaped building through the variation of internal angles between limbs by $15^{\circ}$ for various wind incidence angle from $0^{\circ}$ to $180^{\circ}$ at an interval of $30^{\circ}$. In order to maintain the area same the limbs sizes are slightly increased accordingly. Numerical analysis has been carried out to generate similar nature of flow condition as per IS: 875 (Part -III):1987 (a mean wind velocity of 10 m/s) by using computational fluid dynamics (CFD) with help of ANSYS CFX ($k-{\varepsilon}$ model). The variation of mean pressure coefficients, pressure distribution over the surface, flow pattern and force coefficient are evaluated for each cases and represented graphically to understand extent of nonconformities due to such angular modifications in plan. Finally regular cross shaped building results are compared with wind tunnel results obtained from similar '+' shaped building study with similar flow condition. Reduction in along wind force coefficients for angular crossed shaped building, observed for various skew angles leads to develop lesser along wind force on building compared to regular crossed shaped building and square plan shaped building. Interference effect within the internal faces are observed in particular faces of building for both cases, considerably. Significant deviation is noticed in wind induced responses for angular cross building compared to regular cross shaped building for different direction wind flow.

Mechanical Deterioration of Overhead Transmission Lines by Forest Fires (산불에 의한 가공 송전선로의 기계적 열화 특성)

  • 김영달;김성덕;심재명;정동화;강지원
    • Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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    • v.14 no.6
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    • pp.26-34
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    • 2000
  • The considerations for remaining life of ACSR (Aluminum Stranded Conductors Steel Reinforced) in transmission lines have become gradually important to hold reliability and stability of power supply. The remaining life of ACSR exposed to the atmosphere for a long period may rely on deterioration caused by environmental indices such as atmospheric corrosion, galvanic corrosion, crevice corrosion and fatigue corrosion. One of reduction of useful life in overhead transmission lines built on the ridge of mountain is often caused by forest fires.This paper deals with investigation of strength deterioration performance of ASCR due to fires through several testing and analyzing data for tension load and extension of blazed ACSR. Test samples are ACSR 480[$\textrm{mm}^2$] conductors, which are artificially fired to regular durations. Mechanical properties such as tension load and extension for fired ACSR conductors are tested and estimation functions for mechanical performances corresponding to fire duration are determined. As a result, it can be verified that both tension load and extension of ACSR are reduced by increasing fire duration. Hence, it is obvious that ACSR due to forest fires may lead to mechanical deterioration.

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Collapse response assessment of low-rise buildings with irregularities in plan

  • Manie, Salar;Moghadam, Abdoreza S.;Ghafory-Ashtiany, Mohsen
    • Earthquakes and Structures
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    • v.9 no.1
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    • pp.49-71
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    • 2015
  • The present paper aims at evaluating damage and collapse behavior of low-rise buildings with unidirectional mass irregularities in plan (torsional buildings). In previous earthquake events, such buildings have been exposed to extensive damages and even total collapse in some cases. To investigate the performance and collapse behavior of such buildings from probabilistic points of view, three-dimensional three and six-story reinforced concrete models with unidirectional mass eccentricities ranging from 0% to 30% and designed with modern seismic design code provisions specific to intermediate ductility class were subjected to nonlinear static as well as extensive nonlinear incremental dynamic analysis (IDA) under a set of far-field real ground motions containing 21 two-component records. Performance of each model was then examined by means of calculating conventional seismic design parameters including the response reduction (R), structural overstrength (${\Omega}$) and structural ductility (${\mu}$) factors, calculation of probability distribution of maximum inter-story drift responses in two orthogonal directions and calculation collapse margin ratio (CMR) as an indicator of performance. Results demonstrate that substantial differences exist between the behavior of regular and irregular buildings in terms of lateral load capacity and collapse margin ratio. Also, results indicate that current seismic design parameters could be non-conservative for buildings with high levels of plan eccentricity and such structures do not meet the target "life safety" performance level based on safety margin against collapse. The adverse effects of plan irregularity on collapse safety of structures are more pronounced as the number of stories increases.

Evaluation of structural safety reduction due to water penetration into a major structural crack in a large concrete project

  • Zhang, Xiangyang;Bayat, Vahid;Koopialipoor, Mohammadreza;Armaghani, Danial Jahed;Yong, Weixun;Zhou, Jian
    • Smart Structures and Systems
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    • v.26 no.3
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    • pp.319-329
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    • 2020
  • Structural damage to an arch dam is often of major concern and must be evaluated for probable rehabilitation to ensure safe, regular, normal operation. This evaluation is crucial to prevent any catastrophic or failure consequences for the life time of the dam. If specific major damage such as a large crack occurs to the dam body, the assessments will be necessary to determine the current level of safety and predict the resistance of the structure to various future loading such as earthquakes, etc. This study investigates the behavior of an arch dam cracked due to water pressure. Safety factors (SFs), of shear and compressive tractions were calculated at the surfaces of the contraction joints and the cracks. The results indicated that for cracking with an extension depth of half the thickness of the dam body, for both cases of penetration and non-penetration of water load into the cracks, SFs only slightly reduces. However, in case of increasing the depth of crack extension into the entire thickness of the dam body, the friction angle of the cracked surface is crucial; however, if it reduces, the normal loading SFs of stresses and joints tractions reduce significantly.

Photoelastic Stress Analysis of Fixed Partial Dentures (가공의치(架工義齒)에 작용(作用)하는 Stress에 관(關)한 광탄성학적(光彈性學的) 분석(分析))

  • Cho, Won-Haeng
    • The Journal of Korean Academy of Prosthodontics
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    • v.18 no.1
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    • pp.15-35
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    • 1980
  • The purpose of this study was to investigate stresses in the various components of fixed partial dentures restoring the posterior teeth of the lower jaw, and to measure quantitatively the effects of certain modifications in structural design on the stresses in the restorations using two-dimensional photoelasticity. Two-dimensional photoelastic methods were used in this study. Several models of fixed partial dentures were constructed. Shoulder less margins and anatomic occlusal reduction were incorporated in Model 1. Rounded shoulders and flat occlusal reduction were incorporated in Model 2, while Model 3 was a cantilever fixed partial denture. Other similar fixed partial dentures were constructed with V and U notches deliverately included in the region of the fixed joints for comparative reasons. The birefringent materials used in this study were PSM-1 and PSM-5 in standard sheets. PSM-1 was used for constructing the substructure, and PSM-5 was used in making the components of the fixed partial dentures. The two materials were used in the construction of composite photoelastic models. Improved artificial stone was used to represent dental cement in luting the composite photoelastic models. Static loading procedures were used at preplanned sites to represent occlusal loads in the mouth. 35 mm color and B/W film were used to record isochromatics in accordance with photoelastic procedures. Data reduction was performed using the grid method, which helped in, the mathematical integration procedure (Shear difference method) to separate the principal stresses. The results were as follows. 1. Fixed partial dentures do not function in bending as a symmetrical beam. Alternate areas of tension and compression were demonstrated when multiple contact loading was used. 2. The weakest part in posterior fixed partial dentures is the fixed joint. 3. (1) Models I and modified Model I were loaded on the pontic using a 50 pound vertical static load. The shear stress near the posterior fixed joint in Model 1 (U notches) was+129.4 p.s.i., and at the same fixed joint in modified Model 1 (V notches) was+239.4 p.s.i. The concentration of stress in fixed joint was reduced by 50% when U notches replaced the V notches. (2) Modified Model 2 was loaded using a multiple contact loader at a total load of 125 pounds. The difference between the principal stresses (${\sigma}_1-{\sigma}_2$), shear stress, at the V notches was+600 p.s.i., and at the U notches was+3l7 p.s.i. The shear stress was reduced by 50% when U notches replaced the V notches. V-grooves at the fixed joints should be avoided, and should be replaced by regular shaped U-grooves. 4. Cantilever fixed partial dentures had much higher stresses at the fixed joint than fixed partial dentures that were attached at both ends.

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An Experimental Study on the Fire Resistance Capacity of Asymmetric Slimflor Beam (비대칭 H형강 슬림플로어 보의 내화 성능에 관한 실험적 연구)

  • Park, Won-Sup;Kim, Heung-Youl;Kim, Hyung-Jun
    • Fire Science and Engineering
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    • v.24 no.1
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    • pp.40-45
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    • 2010
  • Asymmetric Slimflor Beam had been unveiled with Thor beam (Hat beam) in Sweden since the late 1970s and had been developed by British Steen and SCI. In the major advanced countries in Europe after the early 1990s have interested in and developed this method, it has been concrened as the absence of hot-rolled section steel in the United Kingdom and welded of asymmetric section steel in Finland in the 2000s. It can be increase total floor area about 10%, save the interior and exterior materials, reduce the waste through reduction of the floor height. And it has more excellent fire resistance performance because less exposed than a regular composite steel beam in fire. This study is purpose that, a fire resistance performance of the Asymmetric Slimflor Beam in fire, it compared the temperature range with deflection of structure by fire behavior and load ratio of structure through change the shape of the steel cross-section in standard fire condition.