• 한국지반공학회논문집
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• 제23권3호
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• pp.25-40
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• 2007

얕은 터널의 개착식 터널 라이닝에 발생하는 과잉토압은 라이닝의 변형과 손상을 유발하는 역학적 주요인자들 중의 하나이며(Kim, 2000), 과잉토압은 되메움토의 다짐불량, 자중에 의한 압밀, 강우의 침투에 의한 다짐, 차량에 의한 진동 등에 의해 발생할 수 있다(Komiya et al., 2000; Taylor et al., 1984; Yoo, 1997). 터널 라이닝에 발생하는 토압을 구하기 위한 많은 시험이 행해졌지만, 부등침하와 과잉토압을 줄일 수 있는 보강대책을 수립하기 위한 사례는 없다. 본 연구는 모래 지반에 $1.0D\sim1.5D$ 깊이에 개착식으로 시공하는 원형의 강성 터널에 작용하는 토압에 관한 것으로 진동다짐의 영향을 모형실험에서 충분히 반영하기 위하여 100Hz의 진동주파수를 사용하였다. 본 연구에서는 개착식 터널 라이링에 작용하는 부등침하와 과잉토압을 줄이기 위해서 지오텍스타일 매트를 설치하였다. 지오텍스타일 매트의 보강에 의한 부등침하와 토압의 감소효과를 확인하기 위해 실내모형실험을 수행하였다. 실내모형실험에서 토피, 매트 보강형태, 절취면의 거칠기 등을 달리하여 가장효과적인 방법을 구하였다. 절취면의 거칠기 달리하기 위해 사면에 사포#100, 사포#400과 acetate 부착하였습니다. 무보강과 매트 보강에 대한 모형실험을 실시하여 구한 토압을 비교하여 매트 보강효과를 살펴보았으며, 사진분석법(Park, 2003)을 이용하여 지반의 변형을 분석하였다.

• Computers and Concrete
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• 제27권2호
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• pp.85-97
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• 2021

In this study, the effect of steel fiber utilization, boundary conditions, different beam cross-section, and length parameter are investigated on the free vibration behavior of fiber reinforced self-compacting concrete beam on elastic foundation. In the analysis of the beam model recommended by Euler-Bernoulli, a method utilizing Stokes transformations and Fourier Sine series were used. For this purpose, in addition to the control beam containing no fiber, three SCC beam elements were prepared by utilization of steel fiber as 0.6% by volume. The time-dependent fresh properties and some mechanical properties of self-compacting concrete mixtures were investigated. In the modelled beam, four different beam specimens produced with 0.6% by volume of steel fiber reinforced and pure (containing no fiber) SCC were analyzed depending on different boundary conditions, different beam cross-sections, and lengths. For this aim, the effect of elasticity of the foundation, cross-sectional dimensions, beam length, boundary conditions, and steel fiber on natural frequency and frequency parameters were investigated. As a result, it was observed that there is a noticeable effect of fiber reinforcement on the dynamic behavior of the modelled beam.

• Computers and Concrete
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• 제30권5호
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• pp.357-367
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• 2022

In this paper, we propose an efficient control method that can be transformed into a general building control problem for building structure control using these reliability criteria. To facilitate the calculation of controller H∞, an efficient solution method based on Linear Matrix Inequality (LMI) is introduced, namely H∞-based LMI control. In addition, a self-tuning predictive grey fuzzy controller is proposed to solve the problem caused by wrong parameter selection to eliminates the effect of dynamic coupling between degrees of freedom (DOF) in Self-Tuning Fuzzy Controllers. We prove stability using Lyapunov's stability theorem. To check the applicability of the proposed method, the proposed controller is applied and the control characteristics are determined. The simulation assumes system uncertainty in the controller design and emphasizes the use of acceleration feedback as a practical consideration. Simulation results show that the performance of the proposed controller is impressive, stable, and consistent with the performance of LMI-based methods. Therefore, an effective control method is suitable for seismic reinforcement of civil buildings.

• Structural Engineering and Mechanics
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• 제39권2호
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• pp.241-266
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• 2011

The Self Compacting Concrete, SCC is the new generation type of concrete which is not needed to be compacted by vibrator and it will be compacted by its own weight. Since SCC is a new innovation and also the high strength self compacting concrete, HSSCC behavior is like a brittle material, therefore, understanding the strength effect on the serviceability performance of reinforced self compacting concretes is critical. For this aim, first the normal and high strength self compacting concrete, NSSCC and HSSCC was designed. Then, the serviceability performance of reinforced connections consisting of NSSCC and HSSCC were investigated. Twelve reinforced concrete connections (L = 3 m, b = 0.15 m, h = 0.3 m) were simulated, by this concretes, the maximum and minimum reinforcement ratios ${\rho}$ and ${\rho}^{\prime}$ (percentage of tensile and compressive steel reinforcement) are in accordance with the provision of the ACI-05 for conventional RC structures. This study was limited to the case of bending without axial load, utilizing simple connections loaded at mid span through a stub (b = 0.15 m, h = 0.3 m, L = 0.3 m) to simulate a beam-column connection. During the test, concrete and steel strains, deflections and crack widths were measured at different locations along each member. Based on the experimental readings and observations, the cracked moment of inertia ($I_{cr}$) of members was determined and the results were compared with some selective theoretical methods. Also, the flexural crack widths of the members were measured and the applicability for conventional vibrated concrete, as for ACI, BS and CSA code, was verified for SCCs members tested. A comparison between two Codes (ACI and CSA) for the theoretical values cracking moment is indicate that, irrespective of the concrete strength, for the specimens reported, the prediction values of two codes are almost equale. The experimental cracked moment of inertia $(I_{cr})_{\exp}$ is lower than its theoretical $(I_{cr})_{th}$ values, and therefore theoretically it is overestimated. Also, a general conclusion is that, by increasing the percentage of ${\rho}$, the value of $I_{cr}$ is increased.

• Steel and Composite Structures
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• 제48권5호
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• pp.565-582
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• 2023

The present research reports the application of engineered cementitious composites (ECC) as an alternative to conventional concrete to improve the seismic behavior of short columns. Experimental and finite element investigation was conducted by testing five reinforced engineered cementitious composite (RECC) concrete columns (half-scale specimens) and one control reinforced concrete (RC) specimen for different shear-span and transverse reinforcement ratios under cyclic lateral loads. RECC specimens with higher shear-span and transverse reinforcement ratios demonstrated a significant effect on the column lateral load behavior by improving ductility (>5), energy dissipation capacity (1.2 to 4.1 times RC specimen), gradual strength degradation (ultimate drift >3.4%), and altering the failure mode. The self-confinement effect of ECC fibers maintained the integrity in the post-peak region and reserved the transmission of stress through fibers without noticeable degradation in strength. Finite element modeling of RECC specimens under monotonic incremental loads was carried out by adopting simplified constitutive material models. It was apprehended that the model simulated the global response (strength and stiffness) and damage crack patterns reasonably well.

• 한국간호교육학회지
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• 제19권2호
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• pp.127-136
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• 2013

Purpose: The aim of the study was to evaluate the effect of self-monitoring of blood glucose (SMBG)-based Diabetes Self-Management Education (DSME) on glycemic control in type 2 diabetes. Methods: This study was designed to compare changes in glycemic control over 12months in SMBG-based DSME group (n=65) versus control group (n=65). Data were obtained from medical records type 2 diabetic patients treated with oral antidiabetic agents and above HbA1c 7.0% from June 2006 to August 2008. All participants completed DSME defined as informational intervention of lifestyle habits and reinforcement of educational Monthly News letter delivered by the diabetes nurse educator. SMBG-based DSME group requested to measure blood glucose 7 times a day for a week and to record their diary and received counseling with a focus on diet and lifestyle during the education. Assessments were conducted baseline, 3, 6 and 12 months. HbA1c was used as an index of glycemic control. Results: 12 months later, the level of HbA1c was reduced by $1.28{\pm}1.68%$ in experimental group and $0.49{\pm}1.05%$ in the control group. We found a significant effect of $Time^*$ Group interaction (p=.013). Conclusion: SMBG-based DSME for patients with type 2 diabetes with oral antidiabetic agents was effective in improving glycemic control and maintaining long-term glycemic control.

• 대한간호학회지
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• 제27권3호
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• pp.614-626
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• 1997

The main purposes of the study were to develop and test a model which explains the dynamic relationship among factors reported as affecting to the quality of life of individuals with rheumatoid arthritis and to examine the relationship between self-help response and quaility of life. Data for the study were collected from March 1996 to December 1996 from 153 female patients who regularly visited a clinic for people with rheumatism. The patients were introduced to the investigators by nurses who worked at that clinic, and then the investigator interviewed the patients for 30 to 40 minutes to collect the data. Instruments used in the study were modified self-report questionaires from the ones which were already developed in previous studies or from related literature. Data analysis were performed using LISREL(Lineal Structural Relations) 8 program to test whether the proposed hypothesized model fit the collected data. To test the fitablity of the hypothesized model both a general fit measure and a detailed fit measure were used. Based on the test results from the various fit measures, the hypothesized model was found to be well suited to the real data. As characteristics related to illness becomes severe, the feasibility for these characteristics leading to the perception of uncertainty about the illness tend to increase, but, the direct effects from the illness characteristics(such as level of physical symptoms, sense of social-psychologic change, limitations of action) as they are related to the other intrinsic variables (self-efficacy or self-help behavior and quality of life), were found to be not significant. It was found that uncertainty had a direct effect on self-efficacy but did not have a direct effect on self-help behavior or quality of life. Also, it is noted that self-efficacy had a positive effect on self-help behavior and quality of life and there was a bilateral relationship between self-efficacy and self-help behavior. Lastly, the hypothesis proposed from the theoretical model in this study was supported basis of the results that self-help behavior provides both direct and positive effects to quality of life. Particularity, since a bilateral relationship was also found between self-help behavior and quality of life in the modified model, as self-help behavior increased, so did quality of life. And, reversely, as quality of life increased, so did self-help behavior. In conclusion, the results of this study suggest that focusing on both acquirement and reinforcement of adjustment factors or self-help behavior is more efficient than focusing on the characteristics of illness in establishing the stategies for improving quality of life of individuals with rheumatoid arthritis.

• 벤처창업연구
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• 제12권1호
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• pp.73-85
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• 2017

본 연구는 예비창업자(특성화고, 대학생)들의 기업가정신 및 창업의지를 함양하기 위해, 예비창업자들이 지각하는 진로불확실성과 진로교육이 기업가정신 및 창업의지에 미치는 영향을 검증하는 동시에 진로불확실성과 창업의지(또는 기업가정신)의 관계에서 자기결정성의 매개 효과를 규명하였다. 예비창업자인 특성화고 및 대학생을 대상으로 설문방식으로 자료를 수집하였으며, 최종 381부를 분석에 사용하였다. SPSS Statistics 22를 이용한 실증분석 결과, 첫째, 예비창업자들이 지각하는 진로불확실성과 창업의지는 통계적으로 유의미하지 않았다. 둘째, 예비창업자들이 지각하는 진로불확실성은 기업가정신에 부정적인 영향을 주었다. 셋째, 진로교육은 창업의지에 유의미한 부정적인 영향을 주었다. 넷째, 진로교육은 기업가정신에 유의미한 영향을 주지 않았다. 다섯째, 진로불확실성은 자기결정성에 부정적인 영향을 주었다. 여섯째, 자기결정성은 진로불확실성과 창업의지의 관계를 완전 매개하는 것으로 분석되었다. 마지막으로 자기결정성은 진로불확실성과 기업가정신의 관계를 완전 매개하는 것으로 나타났다. 이러한 결과를 토대로 예비창업자의 창업의지를 향상시키기 위해서는 교육현장에서 진로교육의 범위를 확대 및 강화하여 진로불확실성을 낮추고, 창업자의 자기결정성을 강화하여 내재적 동기부여를 높여야 하겠다. 이때 창업의지와 기업가정신의 고취는 예비창업가의 자기결정성을 높이는 노력과 동시에 진로교육에 창업교육을 포함시키는 제도적 노력 또한 병행되어야 한다.

• 한국지반공학회논문집
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• 제22권11호
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• pp.89-99
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• 2006

프리캐스트 콘크리트 옹벽은 현장타설 콘크리트 옹벽에 비해 공기 단축효과, 품질의 우수성, 교통 및 인접구조물과의 간섭 최소화 등 많은 장점을 가지고 있다. 하지만 지반조건이 비교적 양호한 직접기초형태의 경우에는 별도의 보강조치를 고려하지 않으면 자중만으로 저항하게 됨에 따라 옹벽의 단면이 증가하게 되고 그에 따른 운반상의 어려움 및 공사비 증가 등의 단점이 있다. 본 연구에서는 이러한 문제점을 보완하기 위한 방법으로 마이크로파일공법의 적용성을 평가해 보았다. 마이크로파일공법은 소형장비로 시공이 가능하므로 작업공간의 제약이 없고, 저비용 및 고효율의 장점을 가지고 있으나 보강효과를 높이기 위해 설치한 마이크로파일의 역학적 거동특성이 명확히 규명되지 않은 상태이며, 마이크로파일의 길이, 직경, 설치각도 및 설치위치 등에 대한 설치기준이 없고 경험에 의존하고 있는 실정이다. 따라서 본 연구에서는 프리캐스트 콘크리트 옹벽에 보강된 마이크로파일의 최적보강형태 및 보강효과를 규명 제시하기 위하여 활동 및 전도거동에 대한 실내모형실험을 각각 시행하였다. 또한 실내모형실험 결과를 토대로 제시된 마이크로파일의 최적보강형태를 검증하기 위한 목적으로 유한요소해석 및 한계평형해석 등의 수치해석을 수행하여 마이크로파일의 최적 보강형태를 제시하였다. 실내모형실험과 수치해석으로 프리캐스트 콘크리트 옹벽에 보강되는 마이크로파일의 최적보강형태를 평가한 결과, 마이크로파일은 옹벽높이의 0.4배 저판길이의 0.04배 일 때가, 최적의 보강효율을 보이는 것으로 평가되었다.

• 대한치과보철학회지
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• 제34권4호
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• pp.823-832
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• 1996

The purpose of this study was to assess the effect of 1) the diameter(0.7,1.0,1.2mm) and number(1,2,3) of commonly available orthodontic metal wires embedded in self-curing orthodontic acrylic resin specimens($64{\times}10{\times}3mm$) and 2) the use of chemical adhesive system(Silicoater, Metalprimer) to prevent slipping at the interface between the resin and the metal wire on reinforcement by using three-point bending test. From this study, the following results were obtained. 1. No statistically significant difference was found among the transverse strengths for the control without reinforcement, one 0.7mm wire, two 0.7mm wires, three 0.7mm wires, and one 1.0mm wire groups(P>.05). 2. In the groups with 1.0 or 1.2mm wires, the transverse strength increased in proportion to the increase of number of wires(P<.05). 3. In the groups with 0.7 or 1.0mm wires, neither of Silicoater and Netalprimer increased the transverse strength significantly(P>.05). 4. No statistically significant difference was found in transverse strength between Silicoater groups and Metalprimer groups with same diameter of wires(P.>05). From these result, it is concluded that diameter of wires is a primary considering factor to reinforce the acrylic resin effectively and, when this requirement is satisfied, increased number of wires or chemical adhesive systems can be expected to produce the additional reinforcing effect.