• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1999년도 봄 학술발표회 논문집(I)
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• pp.135-140
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• 1999

The size effect of axial compressive strength of concrete in notched specimens was experimentally investigated. Based on the concept of the fracture mechanics and size effect law, theoretical studies for axial compressive failure of concrete were reviewed, and two failure modes of concrete specimen under compression were discussed. In this study, experiment of axial compressive failure, which is one of the two failure modes, was carried out by using double cantilever fracture specimens. By varying the slenderness of cantilevers and the eccentricity of applied loads with respect to the axis of each cantilever, the size effect of axial compressive strength of concrete was investigated, and predicted by Bazant's size effect law. The test results show that size effect appears conspicuously for all series of specimens. For the eccentricity of loads, the influence of tensile and compressive stress at the notch tip are significant and so that the size effect is varied. In other words, if the influence of tensile stress at the notch tip grows up, the size effect of concrete increases. And the fact that the fracture process zone must be sufficiently secured for more accurate experiment was affirmed.

• Structural Engineering and Mechanics
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• 제66권1호
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• pp.75-84
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• 2018

This study presents the reliability-based analysis of nonlinear structures using the analytical fragility curves excited by random earthquake loads. The stochastic method of ground motion simulation is combined with the random vibration theory to compute structural failure probability. The formulation of structural failure probability using random vibration theory, based on only the frequency information of the excitation, provides an important basis for structural analysis in places where there is a lack of sufficient recorded ground motions. The importance of frequency content of ground motions on probability of structural failure is studied for different levels of the nonlinear behavior of structures. The set of simulated ground motion for this study is based on the results of probabilistic seismic hazard analysis. It is demonstrated that the scenario events identified by the seismic risk differ from those obtained by the disaggregation of seismic hazard. The validity of the presented procedure is evaluated by Monte-Carlo simulation.

• 한국방재안전학회논문집
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• 제7권1호
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• pp.43-50
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• 2014

본 논문은 신뢰성 이론에 기초하여 철골보의 단경간 및 2경간 연속보의 파손확률을 결정하였다. 계산식에서 철골보에 가해지는 하중은 정규 분포로 가정하여 진행되었으며, 파손확률의 변화를 확인하기 위해 보의 중앙범위에 적용하는 하중을 보의 1대 1과 1대 2로 분할된 지점에 배치하였다. 보의 끝부분의 경계 결합조건 역시 연구에 포함되었다. 연구 결과 파손확률이 있는 보에 대한 결합조건 및 파손확률은 2차 분석에 따라 그 중요도가 낮은 것으로 나타났다. 결론적으로 일부의 경우를 제외하고 보의 파손확률은 보 양단의 경계조건에 따라 차이가 있는 것으로 나타났다.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2002년도 추계학술대회논문초록집
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• pp.384.1-384
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• 2002

Rocket propulsion systems generate very high level noise (acoustic loads), which is due to supersonic jet of rocket propulsion system. In practice, the sound power level of rocket propulsion systems is over 180 ㏈. This high level noise excites rocket structures and payloads, so that it causes the structural failure and electronic malfunctioning of payloads. Prediction method of acoustic loads of rocket enables us to determine the safety of payloads. (omitted)

• 한국산학기술학회논문지
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• 제16권3호
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• pp.2212-2218
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• 2015

세 종류의 얕은기초를 지지하는 기초지반의 하중지지거동을 살펴보고자 모래지반과 점토지반을 가정하여 유한요소 해석을 수행하였다. 띠기초를 지지하는 모래지반의 파괴영역의 형상 및 크기는 상대밀도에 따라 달랐으나 점토지반의 경우 강도에 따라 파괴영역에 차이가 거의 없으며 이론에서 고려되는 파괴영역과 유사한 결과를 보였다. 모래지반에 대한 수치해석을 통해 얻은 하중-침하곡선의 형상을 고려해 볼 때 느슨한 모래에 놓인 기초의 경우 거의 관입전단파괴양상을 보였으며 조밀한 모래에 놓인 기초의 경우 극한하중이 뚜렷하지는 않았다. 점토지반에 놓인 기초에 대하여 수치해석을 통해 얻은 하중-침하량곡선의 경우 침하가 급격하게 증가하는 항복점이 존재함을 알 수 있었다. 모래지반에 의해 지지되는 기초에 대해 이론식에 의해 예측된 극한하중은 수치해석에 의한 극한하중보다 큰 값을 보였으며 점토지반에 대해 이론식에 의해 예측된 극한하중은 수치해석에 의한 극한하중과 유사한 값을 보였다. 1 인치 침하기준법에 의해 결정된 극한하중은 수치해석을 통해 얻은 극한하중보다 약간 작은 값을 보여 안전측의 결과를 보였다.

• Structural Monitoring and Maintenance
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• 제6권1호
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• pp.19-32
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• 2019

One way to provide safe buildings and to protect tenants from the terrorist attacks that have been increasing in the world is to study the behavior of buildings members after being exposed to dynamic loads. Buildings behaviour after being exposed to attacks inspired researchers all around the world to investigate the effect of impact loads on buildings members like slabs and to deeply study the properties of High Performance Concrete. HPC is well-known in its high performance and resistance to dynamic loads when it is compared with normal weight concrete. Therefore, the aim of this paper is finding out the impact of dynamic loads on RPC slabs' flexural capacity, serviceability loads, and failure type. For that purpose and to get answers for these questions, three concrete slabs with 0.5, 1, and 2% steel fiber contents were experimentally tested. The tests results showed that the content of steel fiber plays the key role in specifying the static capacity of concrete slabs after being dynamically loaded, and increasing the content of steel fiber led to improving the static loading capacity, decreased the cracks numbers and widths at the same time, and provided a safer environment for the buildings residents.

• 대한수의학회지
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• 제63권3호
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• pp.24.1-24.6
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• 2023

This study compared the biomechanical properties of bone-stapling techniques with those of other fixation methods used for stabilizing tibial tuberosity fractures using 3-dimensionally (3D)-printed canine bone models. Twenty-eight 3D-printed bone models made from computed tomography scan files were used. Tibial tuberosity fractures were simulated using osteotomy. All samples were divided into 4 groups. Group 1 was stabilized with a pin and tension-band wire; group 2, with a pin and an 8 mm-wide bone staple; group 3, with 2 horizontally aligned pins and an 8 mm-wide bone staple; and group 4 with a 10 mm-wide bone staple. Tensile force was applied with vertical distraction until failure occurred. The load and displacement were recorded during the tests. The groups were compared based on the load required to cause displacements of 1, 2, and 3 mm. The maximum failure loads and modes were recorded. The loads at all displacements in group 4 were greater than those in groups 1, 2, and 3. The loads at 1, 2, and 3 mm displacements were similar in groups 1 and 3. There was no significant difference between groups 1 and 3. Groups 1 and 4 provided greater maximum failure loads than groups 2 and 3. Failure occurred because of tearing of the nylon rope, tibial fracture, wire breakage, pin bending, and fracture around the bone staple insertion. In conclusion, these results demonstrate that the bone-stapling technique is an acceptable alternative to tension-band wire fixation for the stabilization of tibial tuberosity fractures in canine bone models.

• Composites Research
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• 제32권1호
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• pp.37-44
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• 2019

스카프 접착 조인트를 마이크로 볼트로 보강하였을 때, 볼트의 보강효과를 얻을 수 있는지를 시험으로 연구하였다. 스카프 형상에 따른 조인트 보강효과를 확인하기 위해 3가지 스카프비(1/10, 1/20, 1/30)를 고려하였다. 접착면적에 따른 핀의 밀도를 동일하게 유지하기 위해, 1/10, 1/20, 1/30 스카프비를 가지는 조인트에 각각 16, 32, 48개의 볼트를 보강하였다. 기준값을 획득하기 위해 접착제로만 체결된 조인트와 마이크로 볼트만 사용한 조인트에 대한 시험도 수행하였다. 시험 결과 접착제만 적용한 경우, 각 스카프비(1/10, 1/20, 1/30)에 따른 파손하중은 29.7, 39.6, 44.8 kN로 나타났다. 마이크로 볼트로 보강한 경우 파손하중은 스카프비에 따라 각각 28.4, 37.2, 40.1 kN으로 나타났는데, 순수 접착 조인트 파손하중의 96, 94, 90%에 해당한다. 마이크로 볼트만 사용한 경우, 파손하중은 접착 조인트 인장강도의 13-25%에 불과하였다. 스카프비 1/10 조인트의 피로시험 결과 접착제와 볼트를 동시에 사용한 하이브리드 조인트의 피로강도가 접착제만 사용한 경우의 피로강도보다 증가하였지만, 증가율은 2-3%로 미미하였다. 본 연구를 통해 박리응력이 파손의 주원인이 되는 구조물에서와 달리, 전단응력이 파손의 주원인이 되는 스카프 조인트의 경우 마이크로 볼트의 보강효과는 나타나지 않는 것을 확인하였다.

• 한국복합재료학회:학술대회논문집
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• 한국복합재료학회 2001년도 춘계학술발표대회 논문집
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• pp.60-64
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• 2001

In this paper, the tension-compression fatigue test method and the fatigue life characteristics of carbon fabric/epoxy laminate coupon are presented. To avoid the buckling during the compression, a proper design for the test coupons is essential. The critical buckling loads for the coupons are calculated by assuming the coupons as columns under two types of fixed conditions. The first is that both ends of each coupon are perfectly clamped, the second is that both ends of each coupon are simply supported. The strain-load curves are obtained by compressing the representative coupons, on each surface of which a strain gage is attached. The buckling loads obtained from the tests are all between the two calculated critical buckling loads. All the coupons are broken by the compression during the fatigue tests. It is estimated to be the reason that the fatigue load causes delamination before the eventual failure of each coupon, and sequentially the micro-buckling in the delaminated region drives each coupon into fatigue failure during the compression. The S-N curve, the fatigue life characteristics of carbon fabric/epoxy is obtained.

• Computers and Concrete
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• 제14권1호
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• pp.41-57
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• 2014

Modern trend in structural design is to use smaller elements in order to ensure several purposes such as economy, functionality and aesthetic in appearance. However, because of decreasing rigidity of the structural elements, the system displacements increases and displacements become an important subject in this kind of structures takes into account both geometrical changes and the carrying capacity of the material after linear-elastic boundary. In this study, a method is proposed to calculate the failure loads and to analyse the reinforced concrete space frame systems. The numerical examples gathered from the literature survey are solved with this method utilising the prepared computer program and the comparable results are presented. The results show that the method is sufficiently accurate.