스테인레스 스틸 와이어 메쉬 보강공법의 보강조건 평가

김성훈 서울産業大學校 1999 논문집 Vol.50 No.2

Stainless steel wire mesh method(SSWM method) is a new technique for strengthening the deteriorated concrete structure and is consist of the combination with the stainless steel wire mesh for reinforcement materal and developed-permeability polymer mortar for repair materal. The strengthening effect of slab structure by SSWM method were already confirmed by the laboratory tests, but there are not any data for the reinforcement design and applicable conditions of this method. A total of 16 slab specimens with different strengthening conditions that consist of various parameters such as wire diameter, wire anchoring, chipping of concrete surface, the interval of transversal wire and thickness of mortar were tested under the three point bending test. And based on the analytical studies of test results, the optimum design method for strengthening the deteriorated concrete structures using the stainless steel wire mesh were presented.

구조물 노후도를 반영한 외부긴장 보강 효과에 관한 실험적 연구

김상현 ( Sang-hyun Kim ),정우태 ( Woo-tai Jung ),강재윤 ( Jae-yoon Kang ),박희범 ( Hee-beom Park ),박종섭 ( Jong-sup Park ) 한국구조물진단유지관리공학회 2021 한국구조물진단유지관리공학회 논문집 Vol.25 No.1

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 보강효과를 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 앵커볼트에 관한 규정 준수가 필요하다. 외부긴장 보강 여부에 따라 균열하중 및 항복하중이 증가하였으나, 균열 이전에는 보강 전, 후의 강성이 유사하여 보강 효과를 확인하긴 어려웠다. Concrete structures gradually age due to deterioration of materials or excess loads and environmental factors, and their performance decreases, affecting the usability and safety of structures. Although external tension construction methods are widely used among the reinforcement methods of old bridges, it is insufficient to identify the effects and effects of reinforcement depending on the level of aging. Therefore, in this study, a four-point loading experiment was conducted on the subject with the non-reinforced and external tensioning method to confirm the reinforcement effect of the external tensioning method, assuming the aging of the structure as a reduction in the compressive strength and tensile reinforcement of concrete, to analyze the behavior of the reinforcement and confirm the reinforcement effect. As a result of the experiment, it was difficult to identify the amount of reinforcement in the extreme condition due to early elimination of the anchorage. Therefore, compliance with the regulations on anchor bolts is required when applying the external tension reinforcement method. Crack load and yield load increased depending on whether external tension was reinforced, but before the crack, the stiffness before and after reinforcement was similar, making it difficult to confirm the reinforcement effect.

Experimental study of masonry walls strengthened with CFRP

Wei, Chang-Qin,Zhou, Xin-Gang,Ye, Lie-Ping Techno-Press 2007 Structural Engineering and Mechanics, An Int'l Jou Vol.25 No.6

In order to study the ductility and the lateral load carrying capacity of the masonry walls strengthened with CFRPs (Carbon Fiber Reinforced Polymer sheets), three pieces of masonry walls subjected to cyclic loads with low frequency and vertical load of constant amplitude have been tested. Two different strengthening methods have been used. The strengthening efficiency is affected by the strengthening method. A simplified calculation approach has been introduced based on the experimental test results, and the theoretical results agree reasonably well with the experimental results. It is found that the critical loads, the critical displacements, the ultimate loads, the ultimate displacements and the ductile coefficients of the masonry walls strengthened with CFRPs improve remarkably (6%~57%). Therefore, the masonry structures strengthened with CFRPs are of better ductility and of better lateral load carrying capacity than the masonry structures without any strengthening measurements.

기초학력 지도 현황 및 교원 전문성 강화 방안 분석

민윤경 학습자중심교과교육학회 2022 학습자중심교과교육연구 Vol.22 No.1

Objectives The purposes of this study were to ask what they believed to be necessary expertise to improve minimum academic competencies, and how they could strengthen such expertise for elementary and middle school teachers. Methods Survey respondents included 2,002 elementary school teachers and 1,311 middle school teachers, resulting in a total of 3,313 participants. In order to analyze the survey data, the ratio of responses to the survey questions was basically presented, and when asked about the importance and the degree of execution in some questions related to the professionalism of teachers, is there a difference in the degree of actual practice compared to the importance, and if there is a difference, the difference A t-test was performed to see if is statistically significant. In addition, analysis of variance was performed to examine differences in professionalism according to teacher experience. Results Survey results revealed that many schools currently provide remedial education to underachieving students through after-school programs; teachers believed that this form of guidance was most effective. Guidance for underachieving students was mostly provided by respective students’ homeroom teachers at the elementary school level, and subject teachers at the middle school level. The majority of participants responded that underachieving students were still being taught through in-person guidance, even after Covid-19. Participants also felt that teacher expertise was required in terms of sense of duty, eliciting student motivation, creating rapport, diagnosing causes of underachievement, creating an appropriate pedagogical strategy, and providing relevant learning materials. Yet, levels of implementation for these aspects were statistically significantly lower than their levels of importance. and it was confirmed that this differs depending on the number of years of service as a teacher. It can be confirmed that related teacher education is important for guiding students who do not have basic academic ability, and teacher training was found to be the most effective method. Conclusions The results of this study showed that teachers felt continuous, systematic training should be prepared in order to strengthen teachers’ proficiency to improve minimum academic competencies in the future. 목적 본 연구는 기초학력 지도 현황을 파악하고 기초학력 향상을 위해 요구되는 교원 전문성과 이를 강화하기 위한 방안이 무엇인지파악하기 위해 수행되었다. 방법 이를 위하여 초등학교와 중학교 교사들을 대상으로 설문조사를 실시하였으며, 초등학교 교사 2,002명, 중학교 교사 1,311명등 총 3,313명이 설문에 참여하였다. 조사 자료 분석을 위해 기본적으로 조사 문항에 대한 응답 비율을 제시하였으며, 교원 전문성과관련된 일부 문항에서 중요도와 실행도를 물은 경우에는 중요성에 비해 실제 행하고 있는 정도에 차이가 있는지, 차이가 있다면 그차이가 통계적으로 유의한지를 살펴보기 위해 t-검정을 실시하였다. 또한, 교사 경력에 따른 전문성의 차이 등을 살펴보기 위해서는분산분석을 실시하였다. 결과 자료 분석 결과, 현재 기초학력 지도는 방과후 지도가 가장 많이 이루어지고 있고 가장 효과적인 것으로 인식되고 있었다. 초등학교에서는 담임 교사, 중학교에서는 교과 교사가 기초학력 미달 학생 지도를 주로 담당하고 있는 것으로 나타났다. 코로나19 이후에도 대면지도가 가장 많이 활용되고 있었다. 기초학력 미달 학생 지도를 위해서는 교사의 사명감, 동기 유발, 래포 형성, 학습 상황및 원인 진담, 면담을 통한 지도 계획 수립, 교수 목표 설정, 교수학습지도 전략 수립, 개별적 학습 자료 제공 등이 요구되나, 그 중요도에 비해 실행도는 통계적으로 유의미하게 낮은 것으로 나타났으며, 이는 교사 재직 연수에 따라서도 차이가 있는 것이 확인되었다. 기초학력 미달 학생 지도를 위해 관련 교사 교육이 중요하다는 점을 확인할 수 있으며, 그 방법으로는 연수가 가장 효과적인 것으로나타났다. 결론 이러한 연구 결과는 향후 기초학력 지도를 위한 교원 전문성 강화를 위해 주기적이고 체계적인 교사 연수가 마련되어야 함을보여준다.

기초학력 지도 현황 및 교원 전문성 강화 방안 분석

민윤경(Min Yunkyung) 학습자중심교과교육학회 2022 학습자중심교과교육연구 Vol.22 No.1

목적 본 연구는 기초학력 지도 현황을 파악하고 기초학력 향상을 위해 요구되는 교원 전문성과 이를 강화하기 위한 방안이 무엇인지 파악하기 위해 수행되었다. 방법 이를 위하여 초등학교와 중학교 교사들을 대상으로 설문조사를 실시하였으며, 초등학교 교사 2,002명, 중학교 교사 1,311명 등 총 3,313명이 설문에 참여하였다. 조사 자료 분석을 위해 기본적으로 조사 문항에 대한 응답 비율을 제시하였으며, 교원 전문성과 관련된 일부 문항에서 중요도와 실행도를 물은 경우에는 중요성에 비해 실제 행하고 있는 정도에 차이가 있는지, 차이가 있다면 그 차이가 통계적으로 유의한지를 살펴보기 위해 t-검정을 실시하였다. 또한, 교사 경력에 따른 전문성의 차이 등을 살펴보기 위해서는 분산분석을 실시하였다. 결과 자료 분석 결과, 현재 기초학력 지도는 방과후 지도가 가장 많이 이루어지고 있고 가장 효과적인 것으로 인식되고 있었다. 초등학교에서는 담임 교사, 중학교에서는 교과 교사가 기초학력 미달 학생 지도를 주로 담당하고 있는 것으로 나타났다. 코로나19 이후에도 대면지도가 가장 많이 활용되고 있었다. 기초학력 미달 학생 지도를 위해서는 교사의 사명감, 동기 유발, 래포 형성, 학습 상황 및 원인 진담, 면담을 통한 지도 계획 수립, 교수 목표 설정, 교수학습지도 전략 수립, 개별적 학습 자료 제공 등이 요구되나, 그 중요도에 비해 실행도는 통계적으로 유의미하게 낮은 것으로 나타났으며, 이는 교사 재직 연수에 따라서도 차이가 있는 것이 확인되었다. 기초학력 미달 학생 지도를 위해 관련 교사 교육이 중요하다는 점을 확인할 수 있으며, 그 방법으로는 연수가 가장 효과적인 것으로 나타났다. 결론 이러한 연구 결과는 향후 기초학력 지도를 위한 교원 전문성 강화를 위해 주기적이고 체계적인 교사 연수가 마련되어야 함을 보여준다. Objectives The purposes of this study were to ask what they believed to be necessary expertise to improve minimum academic competencies, and how they could strengthen such expertise for elementary and middle school teachers. Methods Survey respondents included 2,002 elementary school teachers and 1,311 middle school teachers, resulting in a total of 3,313 participants. In order to analyze the survey data, the ratio of responses to the survey questions was basically presented, and when asked about the importance and the degree of execution in some questions related to the professionalism of teachers, is there a difference in the degree of actual practice compared to the importance, and if there is a difference, the difference A t-test was performed to see if is statistically significant. In addition, analysis of variance was performed to examine differences in professionalism according to teacher experience. Results Survey results revealed that many schools currently provide remedial education to underachieving students through after-school programs; teachers believed that this form of guidance was most effective. Guidance for underachieving students was mostly provided by respective students’ homeroom teachers at the elementary school level, and subject teachers at the middle school level. The majority of participants responded that underachieving students were still being taught through in-person guidance, even after Covid-19. Participants also felt that teacher expertise was required in terms of sense of duty, eliciting student motivation, creating rapport, diagnosing causes of underachievement, creating an appropriate pedagogical strategy, and providing relevant learning materials. Yet, levels of implementation for these aspects were statistically significantly lower than their levels of importance. and it was confirmed that this differs depending on the number of years of service as a teacher. It can be confirmed that related teacher education is important for guiding students who do not have basic academic ability, and teacher training was found to be the most effective method. Conclusions The results of this study showed that teachers felt continuous, systematic training should be prepared in order to strengthen teachers’ proficiency to improve minimum academic competencies in the future.

탄소섬유시트로 보강된 RC보의 해석 및 설계 프로그램 개발

김성도(Seong-Do Kim),김성수(Sung-Soo Kim) 한국철도학회 2004 철도저널 Vol.7 No.4

In this study, analysis and design programs of bending of RC beams strengthened with fiber sheets are developed by using Visual Basic Language. The program consists two groups, ultimate strength method and nonlinear flexural analysis method. Ultimate strength method regards concrete compressive stress as a rectangular stress block and do not consider tensile stress of concrete and load-deflection curves. On the other hand, nonlinear flexural analysis considers tensile stress of concrete, load-deflection curves, state of stress distribution and failure strain of strengthening material. Also, the analysis method used in this study regards nonlinear flexural stress as compressive stress of concrete. This program can be a good tool for determining the bending strength of strengthened RC beams and estimating the amount of fiber sheets for practical use.

Prediction of the Moment Capacity of FRP-Strengthened RC Beams Exposed to Fire Using ANNs

강성묵,김진국 대한토목학회 2023 KSCE Journal of Civil Engineering Vol.27 No.8

In this study, an Artificial Neural Network (ANN) model to predict the moment capacity of Fiber Reinforced Plastic (FRP) strengthened Reinforced Concrete (RC) beams exposed to fire is developed. The software ABAQUS heat transfer analysis is verified by comparison with the fire resistance test results. Through this heat transfer analysis, the temperature distribution of the beam section is determined, and 400 datasets are obtained using the moment capacity calculation method combined with the section equilibrium method. The data consist of eight input parameters: the beam width, beam height, FRP area, rebar area, concrete compressive strength, insulation thickness, concrete cover depth, and fire exposure time. The output parameter is the moment capacity. The ANN model is developed through a sensitivity study using the algorithm type and the number of hidden-layer neurons as variables. The average error between the predicted data of the developed ANN model and the target data obtained from the moment capacity calculation method was 0.35 kN·m, and the average relative error was 0.2512%, showing high accuracy. Therefore, the ANN model developed here can determine the moment capacity without complex calculations. The effects of the input parameters on the moment capacity of the FRP-strengthened RC beams exposed to fire are investigated using the ANN model.

Numerical modeling of the aging effects of RC shear walls strengthened by CFRP plates: A comparison of results from different “code type” models

Redha Yeghnem,Hicham Zakaria Guerroudj,Lemya Hanifi Hachemi Amar,Sid Ahmed Meftah,Samir Benyoucef,Abdelouahed Tounsi,El Abbas Adda Bedia 사단법인 한국계산역학회 2017 Computers and Concrete, An International Journal Vol.19 No.5

Creep and shrinkage are the main types of volume change with time in concrete. These changes cause deflection, cracking and stresses that affect durability, serviceability, long-term reliability and structural integrity of civil engineering infrastructure. Although laboratory test may be undertaken to determine the deformation properties of concrete, these are time-consuming, often expensive and generally not a practical option. Therefore, relatively simple empirically design code models are relied to predict the creep strain. This paper reviews the accuracy of creep and shrinkage predictions of reinforced concrete (RC) shear walls structures strengthened with carbon fibre reinforced polymer (CFRP) plates, which is characterized by a widthwise varying fibre volume fraction. This review is yielded by three commonly used international “code type” models. The assessed are the: CEB-FIP MC 90 model, ACI 209 model and Bazant & Baweja (B3) model. The time-dependent behavior was investigated to analyze their seismic behavior. In the numerical formulation, the adherents and the adhesives are all modelled as shear wall elements, using the mixed finite element method. Several tests were used to dem¬onstrate the accuracy and effectiveness of the proposed method. Numerical results from the present analysis are presented to illustrate the significance of the time-dependency of the lateral displacements and eigenfrequencies modes.

GSP와 CFRP 쉬트의 표면부착공법을 이용한 RC 슬래브의 보강성능 평가에 관한 실험적 연구

안기만,김광수,박선규,이영재 한국구조물진단유지관리공학회 2007 한국구조물진단유지관리공학회 논문집 Vol.11 No.6

교량의 노후화와 교통량의 증가로 성능개선이 요구되어 질 경우, 경제적인 측면에서 신축 보다는 보수·보강을 통한 성능개선이 보다 바람직한 유지관리이다. 많은 보강공법중 시공방법의 편리와 빠른 시공기간으로 교량의 성능향상을 위해 FRP 재료를 이용한 표면부착공법이 많이 이용되고 있다. 특히, FRP 재료는 철근보다 경량이고 인장강도는 약 10배정도 우수한 재료이다. 이를 이용한 보강성능을 평가하기 위하여 CFRP 쉬트와 GSP를 이용하여 실험을 수행하였다. Recently, an improved capacity for RC bridges is required by their deterioration or necessary to carry traffic increase. Strengthening is known as a better way to improve capacity of bridges than reconstructing in terms of economy. The surface bonded method, which is normally used with FRP material, has some advantages related to conveninent application and time-save among other strengthening methods. FRP material is light and has high tensile strength compared to steel. Therefore, this paper presents how structural capacity strengthed with CFRP sheet and Glass fiber-Steel Plate (GSP) is improved.

탄소섬유시트로 보강된 RC보의 해석 및 설계 프로그램 개발

김성도,김성수 한국철도학회 2004 한국철도학회논문집 Vol.7 No.4

In this study, analysis and design programs of bending of RC beams strengthened with fiber sheets are developed by using Visual Basic Language. The program consists two groups, ultimate strength method and nonlinear flexural analysis method. Ultimate strength method regards concrete compressive stress as a rectangular stress block and do not consider tensile stress of concrete and load-deflection curves. On the other hand, nonlinear flexural analysis considers tensile stress of concrete, load-deflection curves, state of stress distribution and failure strain of strengthening material. Also, the analysis method used in this study regards nonlinear flexural stress as compressive stress of concrete. This program can be a good tool for determining the bending strength of strengthened RC beams and estimating the amount of fiber sheets for practical use.