• Journal of the KSME
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• v.29 no.3
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• pp.231-243
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• 1989

복합재료의 탄성 문제를 정리하면 다음과 같다. 복합재료와 등방성 재료의 탄성학적 차이는 재료의 탄성계수에 기인하며 이것은 각각 다른 형태의 응력-변형률관계를 갖게 한다. 한편 응 력-변형률 관계식을 제외한 탄성학의 지배방정식은 재료의 종류에 관계없이 성립한다. 복합적 층판의 Stiffness와 응력 등은 Lamination 이론을 사용하여 구할 수 있다. 판이론은 평형식을 z방향으로 적분한 식, 즉 합력(resultant force)와 모멘트로 나타낸 평형식을 사용하는데 이 때 처짐 방정식을 구하기 위해 합력. 모멘트-곡률. 변형률 관계식을 이용하는데 이 관계식이 복합 재료와 등방성재료가 상이하다. 결과로 복합재료는 커플링 효과를 갖게 되며, 복합적층판을 대 칭으로 쌓으면 이 효과를 상쇄시킬 수 있다. 복합적층 보의 이론은 유효 굽힘 계수를 도입하면 등방체 보 이론을 사용하여 보의 처짐을 해석할 수 있다. 복합적층 보의 경우 굽힘 응력의 최 대치는 등방체와는 달리 보의 표면에서만 일어나지 않고 내부에서도 일어날 수 있다.

• Journal of the Korea Concrete Institute
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• v.20 no.6
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• pp.765-772
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• 2008

For RC structures, long-term deformation occurs due to the inherent characteristics, which are creep and shrinkage. In terms of serviceability, it is important to limit deflection caused by the deformation to the allowable deflection. In the recent years, various repair and strengthening methods have been used to improve performance of the existing RC structures. One of the typical methods is FRP externally bonded method (EBR). Fiber reinforced polymer (FRP) has been used worldwide as repair and strengthening materials due to its superior properties. Besides, it has to offer improved strengthening performance not only under instantaneous load but sustained load. Therefore, accurate prediction method of deflection for the RC members externally bonded with FRP under sustained load is required. In this paper, three beams were fabricated. Two beams were externally strengthened with one of CFRP plate and GFRP plate respectively. Total three beams were superimposed under sustained load of 25 kN. During 470 days, deflections at midspan were obtained. Moreover, creep coefficients and shrinkage strains were calculated by using ACI-209 code and CEB-FIP code. In order to predict the deflection of the beams, EMM, AEMM, Branson's method and Mayer's method were used. Through the experiment, it was found that the specimen with CFRP plate has the most flexural capacity and Mayer's method is the most precise method to predict total long-term deflections.

• International Journal of Highway Engineering
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• v.8 no.4 s.30
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• pp.115-124
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• 2006

The objectives of this paper are to develop the structural condition evaluation technique using Falling Weight Deflectometer deflections and propose the structural condition criteria for asphalt pavements. To figure out correlation between surface deflections and critical pavement responses, the synthetic database has been established using the finite element pavement structural analysis program. A regression approach was adopted to develop the pavement response model that can be used to compute the stresses and strains within pavement structure using the FWD deflections. Based on the pavement response model, the procedure for assessing the structural condition of pavement layers was proposed in this study. To validate the condition evaluation procedure for asphalt pavements, the FWD test, dynamic cone penetrometer test, and repeated triaxial compression test were conducted on 11 sections of national highway and 8 sections of local road. Test results indicate that the tensile strain at the bottom of AC layer and AC elastic modulus were good indicators for estimating the stiffness characteristics of AC layer. For subbase layer, the BDI value and compressive strain on top of the subbase layer were appropriate to predict the structural capacity of subbase layer. The BCI value and compressive strain on top of the subgrade were found to be good indicators for evaluating the structural condition of the subgrade. The evaluation criteria for structural condition in asphalt pavements was also proposed in this paper.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.34 no.6
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• pp.371-383
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• 2021

Steel-concrete single-leaf blast-resistant doors, having steel box and slab inside, are installed on the wall using supporting members such as hinges and latches. Several studies have been conducted on their deflection behavior in the same direction as that of the blast pressure, but studies on their deflection behavior in the opposite direction, that is, studies on negative deflection behavior are relatively insufficient. In this study, we conducted a parameter analysis using finite element analysis on blast-resistant doors, on their rebound behavior in the negative deflection phase. Results revealed that the plastic deformation of the door, and the change in momentum and kinetic energy during rebound, were major factors influencing the rebound behavior. Greater rebound force was developed on the supporting members in the impulsive region, than in the quasi-static region; due to the characteristics in the impulsive region, where the kinetic energy developed relatively greater than the strain energy. In the design process, it is necessary to consider excessive deformation that could occur in the supporting members as the rebound behavior progresses. Additionally, it was found that in the case of steel-concrete blast doors, the rebound force increased relatively more, when the effects of both rebound and negative blast pressure contributed to the negative deflection of the door. Since conditions for the occurrence of this superposition effect could vary depending on structural characteristics and explosion conditions, further investigation may be required on this topic.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1994.04b
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• pp.449-453
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• 1994

공작기계의 가공정밀도는 공구와 공작물간의 상대변위 크기로서 평가되는데, 이 상대변위는 가공중에 발생 하는 절삭력이 공구-척-주축-기계구조물-안내면-가공테이블-공작물로 이어지는 하중전달 폐곡선을 흐르면서 경로상의 정적, 동적 취약부의 주된 영향을 받아 생기거나 각 요소부품의 변형이 누적되어 생겨난다. 본 연구에서는 주축의 취약부를 규명하기 위하여 정적으로는 정적 처짐곡선을 이용하고, 동적으로는 진동모우드의 굽힘곡선을 이용하여 주축선단의 처짐에 가장 영향을 많이주는 부위를 파악하였다. 취약부의 개선방법으로는 주축지름을 변화시켜 주축선단 근처에서 굽힘이 집중되지 않도록 유도하였다. 그리고 구조개선의 효과를 확인 하기 위해서 기존 주축시스템과 개선 주축시스템의 정적, 동적 특성변화를 비교하였다.

• Journal of the Korea institute for structural maintenance and inspection
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• v.20 no.6
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• pp.113-119
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• 2016

In this study, the method to predict the lateral response by using strain data is presented on the steel moment frame. For this, the reliability of the proposed method by applying the example of five-story frame structure were verified. Using the strain value of columns, it predicted the lateral response of structure. It is assumed that all of four strain sensors for one column set up and the strain responses of both end of the column are utilized. The lateral response of member is calculated by using the slope deflection method. Also, using the acceleration response of the one layer, the stiffness of the rotation spring located in the supporting point is predicted. As a result, it was effective to understand the lateral displacement and acceleration responses and to predict local damage and location.

• Magazine of the Korea Concrete Institute
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• v.9 no.5
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• pp.233-244
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• 1997

구조적으로 손상을 입은 구조물들에 대한 보강방법으로 강판, 카본쉬트, 아라미드섬유쉬트 등을 이용한 접착공법이 최근 들어 많이 사용되고 있으며 그 중 가장 널리 Tm이는 방법은 강판접착공법이다. 강판접착공법에 대해서는 많은 연구가 진행되어 오고 있으나, 보의 구조적 거동에 영향을 미치는 다양한 인자들의 영향이나 강성, 파괴양상등에 미치는 영향들에 대해서는 체계적인 평가가 이루어지지 않은 실정이며 특히 강판접착공법에서 파괴에 큰 영향을 미치는 박리하중에 대한 연구는 미흡한 실정이다. 따라서 본 연구에서는 일련의 철근콘크리트보부재를 대상으로 하여 주요실험변수로 선행하중의 크기, 강판의길이, 강판의 두께, 앵커볼트의 간격과 유무, 강판의 층수, 측면보강높이를 실험변수로 하여, 휨인장에 대해 강판잡착공법을 적용하여 포괄적인 실험을 수행하였다. 3등분점하중법의 실험결과를 이용하여 처짐, 인장 및 압축 철근의 변형도, 콘크리트와 강판의 변형도를 분석하였고, 이를 토대로 파괴양상과 파괴하중을 분석하였다.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.10 no.1
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• pp.1-5
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• 2009

In this research, structural analysis was conducted by applying ANSYS commercial code in order to evaluate deflection quantitatively when each weight of tension controllers was centered and weights and moments on a controller controlling tension amounts was varied in a machinery manufacturing flexible flat cable. Based on the numerical structure analysis, stress, strain and amounts of maximum deformation were obtained and investigated structural validity and was reflected on design of the controller.

• Proceedings of the Korea Concrete Institute Conference
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• 2009.05a
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• pp.103-104
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• 2009

This paper focuses on the characteristics on long-term deflection and creep recovery of reinforced concrete beams under a sustained load of 25kN. In order to investigate the residual strengthen of the RC beam, a static flexural experiment was conducted. The result of the RC beam preloaded was compared with that of a RC beam, which was not preloaded.

• Magazine of the Korea Concrete Institute
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• v.10 no.1
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• pp.143-151
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• 1998

최근들어 반복하중에 의한 철근콘크리트 구조물의 손상이 자주 발견되고 있으며 교량 등의 구조물 등은 때때로 과적차량에 의한 초과하중을 받아 이러한 피로손상이 심화되고 있다. 본 연구에서는 이러한 반복 하중을 받는 철근 콘크리트보의 누적피로손상에 대한 실험적 연구룰 수행하여 피로하중에 의한 철근콘크리트보의 손상과정을 규명하였다. 실험 변수를 전단철근의 양과 반복되는 하중의 크기 및 반복횟수로 하여 실험부재를 제작하였으며, 하중제어에 의한 휨시험법에 의해 3Hz의 반복하중을 시편에 재하하였다. 사인장 균열하중과 사인장 균열 후 반복하중에서의 보의 손상누적거동 즉 처짐. 전단철근의 변형도, 에너지 손실 등의 변화를 실험적으로 평가하였으며, 이를 통하여 반복하중에 의한 누적손상에 의해 철근 콘크리트보의처짐 및 전단변형도가 초기하중상태에서는 급격히 증가하다가 이후 점진적으로 증가하는 것을 규명하였다. 본 연구의 결과는 사용하중상태에서 점진적으로 발생할 수 있는 피로손상의 누적과정을 기술하여 주고 있다.