• Title/Summary/Keyword: 소성변형모형

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Effect of additional firing process after sintering of monolithic zirconia crown on marginal and internal fitness (단일구조 지르코니아 크라운의 소결 후 추가 소성 과정이 변연 및 내면 적합도에 미치는 영향)

  • Shin, Mi-Sun;Lee, Hyeonjong
    • The Journal of Korean Academy of Prosthodontics
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    • v.57 no.4
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    • pp.321-327
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    • 2019
  • Purpose: To evaluate an effect of additional firing process after sintering of monolithic zirconia crown on marginal and internal fit through three-dimensional analysis. Materials and methods: Ten monolithic zirconia crowns were fabricated using titanium abutment model. Monolithic zirconia crowns were designed, milled, and sintered as a control group, and additional firing with coloring was performed as a test group. Three dimensional analysis were performed by using triple-scan protocol, and cross-section analysis on mesio-distal and disto-lingual section was evaluated to measure marginal and internal fitness. Then, three-dimensional surface difference on between two groups was evaluated (${\alpha}=.05$). Results: There was statistically significant difference between the control group ($32.0{\pm}24.3{\mu}m$) and the test group ($17.0{\pm}10.8{\mu}m$) in the mesial axial wall (P < .02) and the control group ($60.2{\pm}24.3{\mu}m$) and the test group ($71.8{\pm}21.5{\mu}m$) in the distal axial wall (P < .01). There was no statistically significant difference at the remaining point. Conclusion: There was no statistical significance on the deviation of inner surface of crown according to firing number, and the results of both group were considered clinically acceptable.

Mathematical Hysteretic Model of RC Frame Elements (철근 콘크리트 프레임 요소의 수리적(數理的)인 이역(履歷)모델)

  • Chung, Young Soo;Kim, Se Yoll
    • KSCE Journal of Civil and Environmental Engineering Research
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    • v.12 no.1
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    • pp.19-27
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    • 1992
  • An enhanced version of the Roufaiel and Meyer model is developed for the simulation of the hysteretic response of reinforced concrete members. This model takes into account the finite size of plastic regions and considers the effects of stiffness degradation, strength deterioration, shear and axial force. A significant improvement is the way in which strength deterioration is simulated during inelastic cyclic loadings. The accuracy of this model has been demonstrated by analytically reproducing numerous laboratory experimental load-deformation curves.

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A Study on the Behavior of Deformation in Soft Soils Subjected to Lateral Flow (측방유동을 받는 연약지반의 변형거동에 관한 연구)

  • 안종필;홍원표
    • Geotechnical Engineering
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    • v.10 no.2
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    • pp.25-40
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    • 1994
  • In order to investigate behavior of lateral flow by plasticity of soils and construction control due to it, in the case of unsymmetrical surcharge load on the soft soils, we examine the existing theoretical background, and compared and analysed the experimental results by model test. After model test fabricated by model test apparatus, which made full remolding samples of soft soils, we observed the state of behavior for deformation with increasing load step to constant time interval. The critical surcharge and ultimate capacity showed tendency to approach to the proposed value of Jaky and Meyerhof, and the lateral flow pressure of which the maximum value was acted on the depth calculated by z/H=0.26+1.71cu and one third value of the maximum lateral flow pressure acted on the ground surface, approach the trapezoid distribution And maximum lateral flow pressure will be calculated by proposed equation of Hong or simple equation which($\alpha=0.4$) the flow pressure coefficient . of proposed equation by Tschebotarioff exchanged to($\alpha=K_0$) . Basides, the failure surcharge by [(q/$y_m$)-q] and [$S_y-(y_m/S_y)$] showed the smaller than ultimate bearing capacity, especially failure criteria line of control diagram of [$S_y(y_m/S_y)$] will be calculated by following equation. $S_y.=3.15exp[-0.58(y_m/S_y)$

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A Study on Characteristics of Passenger Injury for Effective Impact Speed in Vehicles Frontal Collision and Rear-ender (차량 정면충돌 및 추돌시 유효충돌속도에 따른 탑승자 상해특성에 관한 연구)

  • Cho, Joeng-Kwon;Yoon, Jun-Kyu;Lim, Jong-Han
    • The Journal of the Institute of Internet, Broadcasting and Communication
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    • v.15 no.4
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    • pp.239-247
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    • 2015
  • Recently, various research studies on frontal collision and rear-ender which occur more frequently compared to others are underway as the public interest on them is growing. This study analyzes scientifically the relationship between effective impact speed and injury incidence for vehicle crash accident reconstruction and presents a relevant model formula. Because real vehicle experiments have certain limitations such as possible injuries, this study efforts to collect and analyze as many materials as possible to substitute real vehicle experiments, including data from various collision tests and human experiments. As a result, this study present a threshold in which head-on collisions and rear impacts do not cause injuries under 7 km/h of effective impact speed, and suggests a model formula showing that injury extent is linearly proportional to effective impact speed through collision speed and amount of plastic deformation. In conclusion, a model formula for estimating effective impact speed and injury incidence newly proposed in this study is expected to be used as a minimum standard of judgment in disputes on the injury extent of passenger in head-on collisions and rear impacts. Furthermore its availability in terms of technological analysis in legal arguments is expected to be very high if this study will be enhanced by referring to scientific analyses of various real accidents so as to apply it in various types of collision accidents.

A Numerical and Experimental Study on Structural Performance of Noncomposite and Composite Eco-Arch Structures subjected to Concentrated Loads (집중하중을 받는 비합성.합성 생태아치구조물의 성능평가를 위한 수치해석 및 모형실험 연구)

  • Kim, Yong-Hee;Park, Jong-Sup;Lee, Young-Ho;Oh, Min-Su
    • Journal of Korean Society of Steel Construction
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    • v.22 no.2
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    • pp.173-183
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    • 2010
  • In this study, noncomposite and composite eco-arch structures with I-beams and precast concrete(PC) decks were investigated. Four finite-element models(a steel-girder model, a steel-girder-and-several-PC-panels model, a three-steel-girder model, and a three-steel-girder-and-several-PC-panels model) using a general finite-element program, ABAQUS, were reviewed to predict the strength of the noncomposite and composite arch structures. Based on the results of the finite- element analysis, the behaviors of the four models were investigated, and deflection and strain gauges for the experimental specimen consisting of three steel girders and several PC panels were set up to obtain the ultimate strength. The ultimate strength of the specimen was estimated to be 1,961kN. The ultimate strength was much larger than the 1,380-kN load calculated using AASHTO LRFD Bridge Design Specifications(2007). The noncomposite and composite arch bridges were found to have enough strength for safety.

Developments of Advanced Connection Type for Improvements of Mixed Structures(I) : 3D Nonlinear Analysis of the Various Connection Types for Deriving Advanced Connection Type (혼합구조의 성능 향상을 위한 개선된 접합방식의 개발 (I) : 개선된 접합방식을 도출하기 위한 3차원 비선형 해석)

  • Yun, Ik Jung;Huh, Taik Nyung;Kim, Moon Kyum;Cho, Sung Young
    • KSCE Journal of Civil and Environmental Engineering Research
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    • v.28 no.1A
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    • pp.89-94
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    • 2008
  • The problem of interaction between the structures interconnected at discrete points as like composite structures, has a attracted considerable attention for a prolonged period of time. Recently, mixed structures are applied for overcoming structural limits by developed countries. In this paper, advanced connection type of mixed structures are presented by numerical approach. Also it is performed on extensive literature review from theoretical method to numerical analysis. For analysing behaviors of mixed structures according to connection type, 2 different connections and 1 reinforced connection are compared by 3D nonlinear numerical analysis. Nonlinear analysis of mixed structures is carried out by utilizing contact elements of a general purpose structural analysis computer program(ABAQUS). By using 6 criteria, each connections are investigated. From this result, proper reinforcing and well designed connection type are proposed. And results also show that the deflections which are induced by discontinuity on mixed structures, has a linear distribution that should decrease as applying proposed connection type.

Behavioral Characteristics and Safety Management Plan for Fill Dam During Water Level Fluctuation Using Numerical Analysis (수치해석을 이용한 수위변동시 필댐의 거동특성 및 안전관리방안)

  • Jung, Heedon;Kim, Yongseong;Lee, Moojae;Lee, Seungjoo;Tamang, Bibek;Heo, Joon;Ahn, Sungsoo
    • Journal of the Korean Geosynthetics Society
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    • v.20 no.1
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    • pp.45-55
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    • 2021
  • In this study, the behavioral characteristics of the fill dam were analyzed during water level fluctuations through a numerical analysis model, and the reservoir safety management plan was prepared. The variation in plastic deviatoric strain, horizontal displacement, stress path, pore water pressure, etc., due to elevation of water level in the upper and lower sides of shell and core were analyzed using numerical analysis software, viz. GTS NX and LIQCA. The analysis results manifest that as the water level in the dam body increases rapidly, the pore water pressure and displacement also increase quickly. It was found that the elevation of the water level causes an increase in pore water pressure in the dam body as well as an increase in the saturation of the dam body and decreased effective stress. It is considered that this type of dam behavior can be the cause of the reduction of strength and stiffness of the dam. Also, it is assumed that the accumulated plastic deviatoric strain due to the deformation of the dam body caused by water infiltration causes an increase in displacement. Based on these experimental results and the results of analyses of the existing reservoir safety diagnosis techniques, an improvement plan for dam safety diagnosis and evaluation criteria was proposed, and these results can be used as primary data while revising dam safety diagnosis guidelines.

Development of Long-Life Asphalt Pavements Method Using High Modulus Asphalt Mixes (고강성 기층재를 적용한 장수명 아스팔트포장 공법 개발)

  • Lee Jung-Hun;Lee Hyun-Jong
    • International Journal of Highway Engineering
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    • v.8 no.3 s.29
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    • pp.49-61
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    • 2006
  • This study suggests long-life asphalt pavement method which can save maintenance cost by increasing the design and performance period of pavements. The high modulus asphalt binder developed and then various physical tests are performed. Laboratory performance tests and accelerated pavement test are conducted for the high modulus and conventional mixtures. The test results show that dynamic modulus values of high modulus mixtures are higher than those of the conventional mixtures, The high modulus mixtures yield better fatigue, rutting and moisture damage performance than conventional mixtures. Structural analysis is performed and a database is built up for long life asphalt pavement design. Pavement response model is developed through a multiple regression analysis program, SPSS using the database. A design software for the long life pavements is developed based on the pavement response model and laboratory and field performance tests results. In addition, optimum pavement sections and materials are suggested. The suggested AC thickness of long life asphalt pavement is 29cm. A Life cycle cost analysis(LCCA) is conducted to check the economical efficiency of the long life pavement section. The LCCA result shows that initial construction costs of long life and conventional pavements are almost equal, but long life pavement is more profitable in terms of the LCCA.

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Seismic Performance and Flexural Over-strength of Hollow Circular RC Column with Longitudinal Steel Ratio 2.017% (축방향철근비 2.017%인 중공 원형 RC 기둥의 내진성능과 휨 초과강도)

  • Ko, Seong-Hyun
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.21 no.1
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    • pp.1-8
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    • 2017
  • Three small scale hollow circular reinforced concrete columns with aspect ratio 4.5 were tested under cyclic lateral load with constant axial load. Diameter of section is 400 mm, hollow diameter is 200 mm. The selected test variable is transverse steel ratio. Volumetric ratios of spirals of all the columns are 0.302~0.604% in the plastic hinge region. It corresponds to 45.9~91.8% of the minimum requirement of confining steel by Korean Bridge Design Specifications, which represent existing columns not designed by the current seismic design specifications or designed by seismic concept. The longitudinal steel ratio is 2.017%. The axial load ratio is 7%. This paper describes mainly crack behavior, load-displacement hysteresis loop, seismic performance such as equivalent damping ratio, residual displacement and effective stiffness and flexural over-strength of circular reinforced concrete bridge columns with respect to test variable. The regulation of flexural over-strength is adopted by Korea Bridge Design Specifications (Limited state design, 2012). The test results are compared with nominal strength, result of nonlinear moment-curvature analysis and the design specifications such as AASHTO LRFD and Korea Bridge Design Specifications(Limited state design).

Modelling of Principal Stress Rotation in Ko Consolidated Clay (Ko-압밀점토지반속 주응력회전 현상의 모형화)

  • Hong, Won-Pyo;Kim, Tae-Hyeong;Lee, Jae-Ho
    • Geotechnical Engineering
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    • v.13 no.1
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    • pp.35-46
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    • 1997
  • The isotropic single-hardening constitutive model has been applied to predict the behavior of soils during reorientation of principal stresses in the field. The predicted response by the model agrees well with the measured behavior for a series of torsion shear tests performed on hollow cylinder specimens of Ko consoildated clay along various stress -paths. This indicates that the soil behavior during reorientation of principal stresses can be predicted by using the model with application of simple informations given by isotropic compression tests and conventional consolidated-undxained triaxial compression tests. Isotropic elasto-plastic soil behavior has been served during primary loading from both the torsion shear tests and the predictions by the model. However, the directions of maj or principal strain increment given by the model have not coincided with the directions for tests during stress reversal, such as unloading and reloading, within isotropic yield surface for Ko consolidated stress. This indicates that kinematic hardening model instead of isotropic hardening model should be developed to predict the soil behavior during stress reversal. The experimental strain increment vectors in the work-space have been compared with the directions expected for associated and nonassociated flow rules.

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