• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2008년도 추계 학술발표회 제20권2호
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• pp.839-842
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• 2008

현행 기준식에서는 철근콘크리트 보의 취성적 전단 파괴를 방지하기 위하여 전단보강철근이 항복한 이후에 복부 콘크리트가 압축파괴하도록 최대전단철근비에 대한 제한을 두고 있다. 최대전단철근비에 대한 제한은 각 기준식마다 매우 상이하다. ACI 318-05, CSA-04 와 EC2-02기준에서는 최대전단철근비가 콘크리트의 압축강도에 따라서 변화하지만, 일본기준식은 압축강도와 무관하게 일정한 값이다. 고강도콘크리트가 사용될 경우에 CSA-04와 EC2-02기준에서 요구하는 최대전단철근비는 ACI 318-05의 두 배 이상으로 기준식마다 상이하게 최대전단철근비를 제한하고 있다. 이 연구에서는 10개의 철근콘크리트 보 실험을 통하여 최대철근비가 미치는 보의 거동 및 내력을 평가하였다. 실험 결과에 의하면 ACI 318-05에서 요구하는 철근비보다 많은 전단보강철근이 배근된 보에서도 전단보강철근이 항복한 이후에 콘크리트가 압축파괴하였다.

• 한국지진공학회논문집
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• 제28권1호
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• pp.47-57
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• 2024

Recently, in newly constructed apartment buildings, the exterior wall structures have been characterized by thinness, having various openings, and a significantly low reinforcement ratio. In this study, a nonlinear finite element analysis was performed to investigate the crack damage characteristics of the exterior wall structure. The limited analysis models for a 10-story exterior wall were constructed based on the prototype apartment building, and nonlinear static analysis (push-over analysis) was performed. Based on the finite element (FE) analysis model, the parametric study was conducted to investigate the effects of various design parameters on the strength and crack width of the exterior walls. As the parameters, the vertical reinforcement ratio and horizontal reinforcement ratio of the wall, as well as the uniformly distributed longitudinal reinforcement ratio and shear reinforcement ratio of the connection beam, were addressed. The analysis results showed that the strength and deformation capacity of the prototype exterior walls were limited by the failure of the connection beam prior to the flexural yielding of the walls. Thus, the increase of wall reinforcement limitedly affected the failure modes, peak strengths, and crack damages. On the other hand, when the reinforcement ratio of the connection beams was increased, the peak strength was increased due to the increase in the load-carrying capacity of the connection beams. Further, the crack damage index decreased as the reinforcement ratio of the connection beam increased. In particular, it was more effective to increase the uniformly distributed longitudinal reinforcement ratio in the connection beams to decrease the crack damage of the coupling beams, regardless of the type of the prototype exterior walls.

• 한국공작기계학회논문집
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• 제16권3호
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• pp.37-43
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• 2007

Recent technological developments in machine tools have been focused on high speed, low vibration machining and high precision machining. And the concern with multi-functional machining has been increased for the last several years. Multi-tasking machines are widely used in machine tool industries. Laser multi-tasking machine has been developed for high precision and fewer vibration machining. The purpose of this study is to evaluate the effects of structural reinforcement on Laser multi-tasking machine which is comprehensively combined turning center and laser machine. Up to date, for the structural stability evaluation of a multi-tasking machine, the analysis model has been considered only the weight of the upper parts. The positions of upper parts on multi-tasking machine have not been considered in the model. So, the results of the present FE model have revealed some difference with measurement data in case of multi-tasking machine. Design of the machine and structural analysis is carried out by FEM simulation using the commercial software CATIA V5. In the result of the structural analysis, effectiveness of reinforcement of the bed was confirmed.

• Structural Engineering and Mechanics
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• 제68권3호
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• pp.345-358
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• 2018

Heterogeneous structure and, particularly, low resistance to tension stresses leads to different mechanical properties of the concrete in different loading situations. To solve this problem, the tension zone of concrete elements is reinforced. Development of the cracks, however, becomes even more complicated in the presence of bar reinforcement. Direct tension test is the common layout for analyzing mechanical properties of reinforced concrete. This study investigates scatter of the test results related with arrangement of bar reinforcement. It employs results of six elements with square $60{\times}60mm$ cross-section reinforced with one or four 5 mm bars. Differently to the common research practice (limited to the average deformation response), this study presents recordings of numerous strain gauges, which allows to monitor/assess evolution of the deformations during the test. A simple procedure for variation assessment of elasticity modulus of the concrete is proposed. The variation analysis reveals different deformation behavior of the concrete in the prisms with different distribution of the reinforcement bars. Application of finite element approach to carefully collected experimental data has revealed the effects, which were neglected during the test results interpretation stage.

• Computers and Concrete
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• 제15권3호
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• pp.411-436
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• 2015

In this work, a comprehensive approach to model the structural behaviour of Reinforced Concrete (RC) beams subjected to reinforcement corrosion is proposed. The coupled environmental - mechanical damage model developed by some of the authors is enhanced for considering the main effects of corrosion on concrete, on composite interaction between reinforcement bars and concrete and on steel reinforcement. This approach is adopted for reproducing a set of experimental tests on RC beams with different corrosion degrees. After the simulation of the sound beams, the main parameters involved in the relationships characterizing the effects of corrosion are calibrated and tested, referring to one degraded beam. Then, in order to validate the proposed approach and to assess its ability to predict the structural response of deteriorated elements, several corroded beams are analyzed. The numerical results show a good agreement with the experimental ones: in particular, the proposed model properly predicts the structural response in terms of both failure mode and load-deflection curves, with increasing corrosion level.

• Structural Engineering and Mechanics
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• 제62권4호
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• pp.455-464
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• 2017

Rayleigh damping model is recommended in the recently developed Performance-Based Earthquake Engineering (PBEE) methodology, but this methodology does not provide sufficient information due to the complexity of the damping mechanism. Furthermore, each Rayleigh-type damping model may have its individual limitations. In this study, Rayleigh-type damping models that are used widely in engineering practice are discussed. The seismic performance of a large-span single-layer latticed dome subjected to earthquake ground motions is investigated using different Rayleigh damping models. Herein a simulation technique is developed considering low cycle fatigue (LCF) in steel material. In the simulation technique, Ramberg-Osgood steel material model with the low cycle fatigue effect is used to simulate the non-uniformly distributed material damping and low cycle fatigue damage in the structure. Subsequently, the damping forces of the structure generated by different damping models are compared and discussed; the effects of the damping ratio and roof load on the damping forces are evaluated. Finally, the low cycle fatigue damage values in sections of members are given using these damping models. Through a comparative analysis, an appropriate Rayleigh-type damping model used for a large span single-layer latticed dome subjected to earthquake ground motions is determined in terms of the existing damping models.

• Earthquakes and Structures
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• 제17권5호
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• pp.435-445
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• 2019

The collapses of curved bridges are mainly caused by the damaged columns, subjected to the combined loadings of axial load, shear force, flexural moment and torsional moment, under earthquakes. However, these combined loadings have not been fully investigated. This paper firstly investigated the mechanical characteristics of the bending-torsion coupling effects, based on the seismic response spectrum analysis of 24 curved bridge models. And then 9 reinforced concrete (RC) and circular column specimens were tested, by changing the bending-tortion ratio (M/T), axial compression ratio, longitudinal reinforcement ratio and spiral reinforcement ratio, respectively. The results show that the bending-torsion coupling effects of piers are more significant, along with the decrease of girder curvature and the increase of pier height. The M/T ratio ranges from 6 to 15 for common cases, and influences the crack distribution, plastic zone and hysteretic curve of piers. And these seismic characteristics are also influenced by the compression ratio, longitudinal reinforcement ratio and spiral reinforcement ratios of piers.

• 대한간호학회지
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• 제15권1호
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• pp.5-16
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• 1985

This study examined the effects of husband's supportive behavior reinforcement education on stress relief of primigravidas. The purpose was to reinforce husbands' supportive behavior and relieve primigravidas' stress. The purposes of this study were to determine lactors influencing Primigravidas' stress and the effect of husbands' supportive behavior reinforcement education on stress relief of primigravidas. The subjects, consisting of 140 primigravidas who registered or visited in three obstetrics and gynecology clinics in J city, were divided into at random experimental and control groups. Data were collectpe from April To July, 1984 through interviews during hospital visits, and by questionaires. The husbands' supportive behavior reinforcement education and the measurement tools were developed by the investigator from the literature and during pilot study: the instruments to measure primigravidas' stress and husbands' supportive behavior were tested for reliability and validity. Personality characteristisc were measured by Chestnuts' Stress Management instrument. T-test, ANOVA, ω², and Pearson Correlation were used in analysing the data to confirm the intensity of the influence and the relation between general characteristics and primigravidas' stress. Pearson correlation and Stepwise Multiple Regression were used to confirm the predictors of primigravidas' stress. Independent variables were compared by means of t-test and χ³-test to confirm significant discrepancy of experimental and control groups. T-test, paired t-test, pearson correlation were used in analyzing the data to confirm the effect of husband's supportive behavior reinforcement education on stress relief of primigravidas. The results of the study are summarized. Results from analyzing the effect of husbands' supportive behavior reinforcement education: There was no significant difference between the general characteristics of the experimental and control groups. And husbands' supportive behavior, personality, marital Satisfaction, natural abortion variables influenced at primigravidas' stress. A hypothetical test by comparative analysis of the measurement of primigravidas' stress and husbands' support behavior between the experimental and the control group before and after the experiment to confirm the effect of husbands' supportive behavior reinforcement education resulted in the following: The first hypothesis that husbands' supportive behavior reinforcement education will increase husbands' support behavior to relieve primigravidas' stress was supported. The second hypothesis that husbands' supportive behavior reinforcement education will relieve primigravidas' stress was supported. As a result, it u·as shown that husbands' supportive behavior reinforcement education relieved primigravidas' stress, and the hypotheses were supported. The third hypothesis that the higher the degree of husbands' supportive behavior, the lower the primigravidas' stress was supported. It was concluded that husbands' supportive behavior reinforcemen education increase husbands' supportive behavior and relieves Primigravidas' stress.

• 기독교교육논총
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• 제61권
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• pp.81-107
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• 2020

이 논문은 관찰학습에서 나타나고 있는 반두라의 대리강화에 대한 이론과 효과들을 살펴보고, 그 개념을 기독교교육에서 행해지고 있는 영적 롤 모델링 전략에 적용한 연구이다. 이를 위해 먼저 반두라가 소개하고 있는 대리강화란 무엇이며, 관찰학습에서 대리강화가 어떻게 발생하는가 그리고 대리강화가 관찰자의 행동 변화에 어떠한 영향을 미치는가에 대하여 살펴보았다. 특별히 반두라는 관찰학습과 모방 혹은 반모방 행동 안에서 일어나는 학습과정에 대하여 개념화하였다. 이를 바탕으로 하여 반두라는 관찰학습에서 일어나는 대리강화의 과정을 4단계(집중, 기억, 행동재생, 그리고 동기화)로 분류하여 설명한다. 그뿐만이 아니라. 대리강화의 효과에 대해 3가지(관찰학습효과, 억제-탈억제효과, 유발효과)를 제시하였다. 이러한 반두라의 대리강화 이론과 그 효과를 바탕으로 하여 기독교교육에서 논의되고 있는 예수님 닮아가기 혹은 제자훈련 안에서의 영적 롤 모델링 전략을 재평가했다. 특별히 성경에서 사용하고 있는 모방에 대한 개념을 반두라의 대리강화 이론과 비교하면서 재해석하였고, 사도 바울이 제시하고 있는 영적 롤 모델의 역할을 대리강화의 효과라는 차원에서 재점검했다. 그 결과 2가지 차원에서의 영적 롤 모델 전략을 발견하였다. 즉 바울의 영적 롤 모델 역할은 긍정적인 차원에서 대리강화로써 신자로 하여금 기대되는 행동을 실행할 수 있도록 도와주는 하나의 본보기가 된다. 반면에 바울의 명령은 신자들에게 명확한 탈억제 효과를 불러일으키는 부정적인 차원에서의 대리강화로 사용되고 있음을 발견하였다. 그리고 마지막으로 관찰학습에 대한 연구들과 성경적 영적 롤 모델링 전략을 서로 연관시킴으로써 반두라의 대리강화가 기독교교육에 미칠 가능성을 함의하였다.

• 한국구조물진단유지관리공학회 논문집
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• 제25권1호
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• pp.1-6
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• 2021

콘크리트 구조물은 재료의 열화나 초과된 하중 및 환경적 요인에 의해 점차 노후화 되며 그 성능이 감소하여 구조물의 사용성 및 안전성에 영향을 미치게 된다. 노후 교량의 보강 공법 중 외부긴장 공법이 널리 사용 중이지만, 노후도에 따른 보강 효과 및 영향 규명은 미흡한 실정이다. 따라서 이 연구에서는 구조물의 노후도를 콘크리트 압축강도 및 인장철근량의 감소로 가정하고 노후도에 따른 외부긴장 공법의 보강 효과를 확인하기 위해 무보강 및 외부긴장 공법을 적용한 실험체의 4점 재하실험을 수행하여 보강 여부에 따른 거동을 분석하고 보강 효과를 확인하였다. 실험 결과 정착구의 조기 탈락에 따른 극한 상태의 보강량을 확인하기 어려웠으며, 이에 따라 외부긴장 보강 공법의 적용 시 앵커 볼트에 관한 규정 준수가 필요하다. 외부긴장 보강 여부에 따라 균열하중 및 항복하중이 증가하였으나, 균열 이전에는 보강 전, 후의 강성이 유사하여 보강 효과를 확인하긴 어려웠다.