• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 2004년도 봄 학술발표회 논문집
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• pp.479-486
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• 2004

The purpose of this study is to practical use with increase safety, usablility and economical. In this study, the property of fatigue behavior was tested by comparing reinforced concrete and steel fiber reinforced concrete. The basic test, the static test and fatigue test were used as the research methods. Basic on the test, the material compressive strength test and split tensile strength test ware conducted 7 days and 28 days after the concrete was poured. In the static test, there ware four types of experimental variables of the steel fiber mixing ratio : 0.00%, 0.75%, 1.00%, and 1.25%. The ultimate load initial diagonal tension crack, and initial load of flexural cracking were all observed by static test. A methodology for the probabilistic assement of steel fiber reinforced concrete(SFRC) which takes into account material variability, confinement model uncertainty and the uncertainty in local and globa failure criteria is applied for the derivation of vulnerability curves for the serviceability and ultimate limit states, the reliability of SFRC using the proposed practical linear limit state model is evaluated by using the AFOSM(Advanced First Order Second Moment) method and MCS(monte-Calrosimulation) method.

• Computers and Concrete
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• 제18권1호
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• pp.69-97
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• 2016

Performance-based remaining life assessment of reinforced concrete bridge girders, subject to chloride-induced corrosion of reinforcement, is addressed in this paper. Towards this, a methodology that takes into consideration the human judgmental aspects in expert decision making regarding condition state assessment is proposed. The condition of the bridge girder is specified by the assignment of a condition state from a set of predefined condition states, considering both serviceability- and ultimate- limit states, and, the performance of the bridge girder is described using performability measure. A non-homogeneous Markov chain is used for modelling the stochastic evolution of condition state of the bridge girder with time. The thinking process of the expert in condition state assessment is modelled within a probabilistic framework using Brunswikian theory and probabilistic mental models. The remaining life is determined as the time over which the performance of the girder is above the required performance level. The usefulness of the methodology is illustrated through the remaining life assessment of a reinforced concrete T-beam bridge girder.

• Computers and Concrete
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• 제10권5호
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• pp.541-555
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• 2012

This paper presents an algorithm for the evaluation of stresses in reinforced concrete sections under service loads. The algorithm is applicable to any section defined by polygonal contours and is based on an analytical integration of the stresses. The nonlinear behaviour of concrete is represented by the parabola-rectangle law used in the Eurocode-2 for the ultimate concrete design. An integrated definition of the strains in concrete and steel is possible by the use of Heaviside functions, similarly to what is done for ultimate section design in Barros et al. (2004). Other constitutive equations for the definition of the stresses in the concrete or steel can be easily incorporated into the code. The examples presented consist in the evaluation of resulting axial load and bending moment in an irregular section and in a section in L shape. The results, for service stresses, can also be plotted in terms of design abacus; a rectangular doubly reinforced section is presented as example.

• 한국항해항만학회:학술대회논문집
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• 한국항해항만학회 2004년도 춘계학술대회 논문집
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• pp.77-82
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• 2004

노후선박의 구조적 안전성을 확보하기 위해서는 부식이나 피로균열 및 기계적인 손상에 의하여 선체 구조 강도가 어떠한 영향을 받는지 충분히 검토하여 적절한 수리 보수 등 이에 대한 대책을 강구할 필요가 있다. 본 연구에서는 이러한 관점에서 부식, 피로균열, 기계적인 손상과 같은 노후 선박에 발생할 수 있는 여러 가지 손상이 선체강도에 미치는 영향을 이론적, 수치적, 실험적인 방법을 통하여 조사하고, 이를 통하여 선각거더의 소성붕괴강도 저하를 고려한 신뢰성 평가법 및 보수, 수리를 통한 인정수준 이상의 선각강도를 유지하게 하는 지침도 연구하였다.

• Computers and Concrete
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• 제24권2호
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• pp.117-123
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• 2019

Optimization is an important subject which is widely used in engineering problems. In this paper, an analytical method is developed for optimum design of reinforced concrete beams considering both flexural and shear effects. A closed-form formulation is derived for optimal height and rebar of beams. The total material cost of steel and concrete is considered as the objective function which is minimized during the optimization process. The ultimate flexural and shear capacities of the beam are considered as the main constraints. The ultimate limit state is considered for deriving the relations for flexural capacity of the beam. The design requirements are considered according to the item 9 of the Iranian National Building. Analytical formulas and some curves are proposed to be used for optimum design of RC beams. The proposed method can be used to perform the optimization of RC beams without the need of any prior knowledge in optimization. Also, the results of the studied numerical example show that the proposed method results in a better design comparing with the other methods.

• 대한조선학회논문집
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• 제32권3호
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• pp.83-97
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• 1995

본 논문의 목적은 종굽힘모멘트를 받는 선각거더의 최종강도를 계산하는 간이식을 도출하는 것이다. 먼저 기 제안된바 있는 계산식들을 조사 분석하였으며, 지금까지의 계산식 도출방법을 크게 해석적 방법, 경험적 방법 및 선형근사법의 3종류로 분류하였다. 선각거더는 종굽힘모멘트의 증가와 함께 압축플랜지의 붕괴와 인장플랜지의 항복에 의해 전체적으로 최종강도에 도달한다고 알려져 있다. 이때 선측부도 압축플랜지 부근에서는 붕괴하며, 인장플랜지 부근에서는 항복상태에 도달해 있는 경우가 많다. 그러나, 중립축부근에서는 여전히 탄성상태에 남아있는 것이 보통이다. 이같은 사실을 근거로 선각 횡단면에 걸쳐 적절한 응력분포를 가정하였으며, 이것으로부터 최종강도 계산식을 해석적인 방법으로 도출하였다. 본 계산식의 정도는 기존의 모형실험 및 수치해석결과와 비교하여 검증하였다.

• Earthquakes and Structures
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• 제21권5호
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• pp.445-460
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• 2021

This study experimentally explored the behaviour of 12 concrete filled steel tube (CFST) and steel tube columns subjected to lateral cyclic loading. The L/D ratio was 12.3 while D/t ratios were 45.4, 37.8 and 32.4, classifying these 12 specimens into 3 groups. Each group included 3 CFST and 1 steel tube columns and were tested to failure. The experimental results indicated that CFST specimens reached the state of 'collapse prevention' (drift 4%) prior to the occurrence of local buckling. Strength degradation of CFST specimens did not occur up to the failure by buckling. This showed the favourable characteristic of CFST columns in preventing collapse of structures subjected to earthquakes. The high energy absorption capability in the post collapse limit state was appropriate for dissipating energy in structures. Compared to steel tube columns, CFST columns delayed local buckling and prevented inward buckling. Consequently, CFST columns exhibited their outstanding seismic performance in terms of the increased ultimate resistance, capacity to sustain 2-3 additional load cycles and significantly higher drift. A simple and reasonably accurate model was proposed to predict the ultimate strength of CFST columns under lateral cyclic loading.

• 한국해양공학회지
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• 제21권3호
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• pp.52-57
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• 2007

Composite material is one of the strongest candidates for deep see pressure hulls. Research regarding composite cylinders, subjected to hydrostatic pressure, has been ongoing for a couple of decades, abroad, but domestic research is very new. Experimental investigations seem necessary, in order to understand their structural behavior not only up to the ultimate limit state, but in the post-ultimate regime. That experimental information will be very helpful in the development of any theoretical methods or to substantiate any commercial numerical packages for structural analyses. In this study, ultimate strength tests on seven composite cylinders subjected to hydrostatic pressure are reported, which includes the fabrication method of models, mechanical properties of the material, initial shape imperfection measurements, test procedure, and strain and axial shortening measurements during the tests. The ultimate strengths of the models were compared with predictions of numerical analyses. The numerical predictions are higher than the test results. It seems necessary to improve the accuracy of the numerical predictions by considering the initial shape and material imperfections.

• 한국해양공학회:학술대회논문집
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• 한국해양공학회 2006년 창립20주년기념 정기학술대회 및 국제워크샵
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• pp.154-157
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• 2006

Composite material is one of the strong candidates for deep see pressure hulls. Research regarding composite unstiffened or stiffened cylinders subjected to hydrostatic pressure has a couple of decades history abroad but domestic research is very new. Experimental investigations seem necessary to understand their structural behavior not only up to the ultimate limit state but in post-ultimate regime. Those experimental information will be very helpful to develop any theoretical methods or to substantiate any commercial numerical packages for structural analyses. In this study, ultimate strength tests on seven composite cylinders subjected to hydrostatic pressure are reported, which includes the fabrication method of models, material properties of the material, initial shape imperfection measurements, test procedure and strain and axial shortening measurements during the tests. The ultimate strengths of the models were compared with those of numerical analyses. The numerical predictions are higher than the test results. It is necessary to improve the accuracy of the numerical predictions.

• 대한토목학회논문집
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• 제26권4A호
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• pp.735-742
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• 2006

실 설계에서 적용되는 강곡선 플레이트거더교의 기하학적인 설계범위 내에서 횡방향변형이 충분히 지지된 강곡선 플레이트거더 복부판의 극한전단강도는 비록 직선복부판에 비해 후좌굴강도는 감소할지라도 탄성좌굴강도가 상대적으로 증가한다. 또한 강곡선 플레이트거더 복부판의 극한전단강도는 후좌굴강도를 포함한 직선플레이트거더 복부판의 극한전단강도와 같은 크기를 발현하고 있음이 여러 연구를 통해서 입증되었다. 본 연구에서는 강곡선 플레이트거더 복부판이 극한전단강도를 발현하기 위한 중간수직보강재의 소요강성에 관한 수치해석연구를 수행하였다. 수치해석결과로부터 후좌굴거동이 존재하는 강곡 선플레이트거더 복부판이 후좌굴강도를 충분히 발현하기 위해서는 현행 Guide Specifications(AASHTO, 2003)의 중간수직보강재 강성이 후좌굴거동 시에 단순지지역할을 하기에는 부족한 것으로 조사되었으며, 이를 기초로 전단좌굴강도비에 따른 소요강성식을 제안하였다.