• 콘크리트학회지
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• 제8권3호
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• pp.209-218
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• 1996

프리캐스트 프리스트레스트 콘크리트 구조물의 정착부에 프리스트레스트 힘이 도입되면, 과다한 국부 집중 하중으로 인하여 균열이 발생할 수 있으며, 최근 이러한 구조물 건설시 텐던을 따라가며 심각한 균열이 발생한 경우가 있다. 본 논문은 프리캐스트 프리스트레스트 콘크리트 구조물의 정착부에 발생하는 국부집중응력의 분포 특성을 규명하고, 정착부 보강 형태에 따른 국부응력 효과를 규명하여 합리적인 정착부 설계 개념을 제시함에 목적이 있다. 이를 위하여 정착부 형태에 따른 역학적 거동 실험 및 해석연구가 수행되었다. 위의 연구 결과 나선형 보강철근이 극한 및 균열하중에 대한 저항능력이 가장 우수함이 집중응력 분포 특성을 고찰함으로서 나타났으며, 정착부의 파괴기구, 정착부 보강설계를 위한 기본 개념 및 그 방법이 제시되었다.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2005년도 추계학술대회 논문집
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• pp.732-739
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• 2005

The determination of sound pressure radiated from periodic plate structures is fundamental in the estimation of noise level in aircraft fuselages or ship hull structures. As a robust approach to this problem, here a very general and comprehensive analytical model is developed for predicting the sound radiated by a vibrating plate stiffened by periodically spaced orthogonal symmetrical beams subjected to a sinusoidally time varying point load. In this these, we experiment with the numerical analysis using the space harmonic series and the SYSNOISE for measuring the vibration mode and character of response caused by sound radiation with adding the harmonic point force in the thin isotropic plate supported by the rectangular lattice reinforcement. We used the reinforcements, beams of open type section like the style of 'ㄷ' letter; the space of the beams were chosen to be 0.2m, 0.3m, 0.4m. We studied the behavior of sound pressure levels, analysis of vibration mode between support points, connection between frequency function and sound pressure levels, and connection between position function and sound pressure levels.

• Structural Engineering and Mechanics
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• 제73권5호
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• pp.515-527
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• 2020

This paper presents a stress field approach for the shear capacity of stirrup-reinforced concrete beams that explicitly incorporates the contribution of principal tensile stresses in concrete. This formulation represents an extension of the variable strut inclination method adopted in the Eurocode 2. In this model, the stress fields in web concrete consist of principal compressive stresses inclined at an angle θ combined with principal tensile stresses oriented along a direction orthogonal to the former (the latter being typically neglected in other formulations). Three different failure mechanisms are identified, from which the strut inclination angle and the corresponding shear strength are determined through equilibrium principles and the static theorem of limit analysis, similar to the EC-2 approach. It is demonstrated that incorporating the contribution of principal tensile stresses of concrete slightly increases the ultimate inclination angle of the compression struts as well as the shear capacity of reinforced concrete beams. The proposed stress field approach improves the prediction of the shear strength in comparison with the Eurocode 2 model, in terms of both accuracy (mean) and precision (CoV), as demonstrated by a broad comparison with more than 200 published experimental results from the literature.

• 한국해양학회지:바다
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• 제28권4호
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• pp.121-132
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• 2023

표층 수온의 이상 고수온 현상인 해양열파는 해양생태계, 수산업, 기상 현상 등 인간 활동 및 해양 생물들에게 광범위하게 영향을 미치기 때문에 많은 해양학자들의 관심을 받고 있다. 본 연구에서는 여름철 동중국해의 해양 물성 변화를 유발하는 중요한 원인인 양자강 희석수 분포가 해양열파에 미치는 영향에 대해서 살펴보았다. 동중국해 표층 염분 분포는 6~8월에 양자강 희석수의 동쪽 확장으로 인해 제주도 및 대한해협까지 희석수의 영향을 받는 것을 알 수 있었고, 9월에는 양자강 희석수가 양자강 하구역에 제한적으로 존재하는 형태를 보여주었다. 여름철 해양열파 누적강도를 Empirical Orthogonal Function (EOF) 분석을 통해 분석하였다. EOF 첫번째 모드의 고유벡터와 주성분 시계열을 추출하여 양자강 희석수와 상관관계 분석을 실시한 결과, 양자강 희석수로 인해 염분이 낮은 해역과 해양열파 누적강도가 강하게 나타나는 해역의 공간 상관성이 매우 높은 음의 상관관계를 보임을 알 수 있었다. 이는 희석수로 인한 성층 강화가 해양열파의 강도 및 지속성을 증가시킬 수 있음을 보여준다. 본 연구결과는 한반도 연근해 해양열파 발생에 있어서 대기변화와 해양 환경이 모두 중요한 요인이 될 수 있음을 시사한다.

• Structural Engineering and Mechanics
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• 제39권1호
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• pp.125-145
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• 2011

Pushover analysis has gained significant popularity as an analytical tool for realistic determination of the inelastic behaviour of RC structures. Though significant work has been done to evaluate the demands realistically, the evaluation of capacity and realistic failure modes has taken a back seat. In order to throw light on the inelastic behaviour and capacity evaluation for the RC framed structures, a 3D Reinforced concrete frame structure was tested under monotonically increasing lateral pushover loads, in a parabolic pattern, till failure. The structure consisted of three storeys and had 2 bays along the two orthogonal directions. The structure was gradually pushed in small increments of load and the corresponding displacements were monitored continuously, leading to a pushover curve for the structure as a result of the test along with other relevant information such as strains on reinforcement bars at critical locations, failure modes etc. The major failure modes were observed as flexural failure of beams and columns, torsional failure of transverse beams and joint shear failure. The analysis of the structure was by considering all these failure modes. In order to have a comparison, the analysis was performed as three different cases. In one case, only the flexural hinges were modelled for critical locations in beams and columns; in second the torsional hinges for transverse beams were included in the analysis and in the third case, joint shear hinges were also included in the analysis. It is shown that modelling and capturing all the failure modes is practically possible and such an analysis can provide the realistic insight into the behaviour of the structure.

• Structural Engineering and Mechanics
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• 제78권5호
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• pp.599-610
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• 2021

Early detection of small concrete crack or reinforcement corrosion is necessary for Structural Health Monitoring (SHM). Global vibration based methods are advantageous over local methods because of simple equipment installation and cost efficiency. Among vibration based techniques, FRF based methods are preferred over modal based methods. In this study, a new coupled method using frequency response function (FRF) and proper orthogonal modes (POM) is proposed by using the dynamic characteristic of a damaged beam. For the numerical simulation, wave finite element (WFE), coupled with traditional finite element (FE) method is used for effectively incorporating the damage related information and faster computation. As reported in literature, hybrid combination of wave function based wave finite element method and shape function based finite element method can addresses the mid frequency modelling difficulty as it utilises the advantages of both the methods. It also reduces the dynamic matrix dimension. The algorithms are implemented on a three-dimensional reinforced concrete beam. Damage is modelled and studied for two scenarios, i.e., crack in concrete and rebar corrosion. Single and multiple damage locations with different damage length are also considered. The proposed methodology is found to be very sensitive to both single- and multiple- damage while being computationally efficient at the same time. It is observed that the detection of damage due to corrosion is more challenging than that of concrete crack. The similarity index obtained from the damage parameters shows that it can be a very effective indicator for appropriately indicating initiation of damage in concrete structure in the form of spread corrosion or invisible crack.