• Architectural research
• /
• 제17권1호
• /
• pp.41-48
• /
• 2015

Early investigations focused mainly on manipulating the confinement effect to develop a reinforced concrete column with lateral hoops. Based on this legacy model, Li's model incorporated the additional confinement effect of a steel jacket. However, recent experiments on plain concrete cylinders with steel jackets revealed relatively large discrepancies in the estimates of strength enhancement and the post-peak behavior. Here, we describe a modified constitutive law for confined concrete with an unbonded external steel jacket in terms of three regions for the loading stage. We used a two-phase heterogeneous concrete model to simulate the uniaxial compression test of a $150mm{\times}300mm$ concrete cylinder with three thicknesses of steel jackets: 1.0 mm, 1.5 mm, and 2.0 mm. The proposed constitutive model was verified by a series of finite element analyses using a finite element program. The damaged plasticity model and extended Drucker-Prager model were applied and compared in terms of the level of pressure sensitivity for confinement in 3D. The proposed model yielded results that were in close agreement with the experimental results.

• 전산구조공학
• /
• 제10권3호
• /
• pp.241-250
• /
• 1997

콘크리트에 발생하는 변형률 국소화는 연화거동에 수반하여 변형이 국부적으로 집중되는 현상으로 이를 유한요소해석 할 수 있는 일관된 알고리즘을 개발하는 것이 본 연구의 목적이다. 변형률 국소화현상이 발생한 콘크리트는 변형률이 집중되는 국소화영역과 그외의 영역인 비국소화영역으로 크게 구분할 수 있으며 국소화영역에서는 연화현상을 포함하는 탄소성거동을 하게 되며 비국소화영역은 손상제하거동을 수반하게 된다. 변형률 국소화현상이 진행중인 콘크리트의 국소화영역을 모델링하기 위하여 열역학적으로 정식화된 전형적인 소성모델에 콘크리트의 극한응력 이후에 비선형 연화로 표현되는 소성거동을 고려할 수 있는 일반화된 Drucker-Prager모델을 도입하였으며 소성이론식의 적분을 위해 return-mapping 알고리즘을 사용하고 일관된 알고리즘을 전개하였다. 또한, 콘크리트의 비국소화영역의 모델링을 위하여 열역학적 자유에너지함수를 수정하여 비선형 탄성 및 손상의 일관된 알고리즘을 전개하였다. 개발된 알고리즘에 의한 유한요소해석을 통해 압축을 받는 콘크리트 부재의 변형률 국소화 현상을 해석하였다.

• 한국전산구조공학회논문집
• /
• 제15권4호
• /
• pp.567-578
• /
• 2002

본 논문은 8절점 고체요소를 이용하여 항공기 충돌에 의한 원전 격납건물의 동적 거동을 분석하고 그 결과를 기술하였다. 콘크리트의 재료적 특성을 표현하기 위하여 Drucker-Prager항복기준을 바탕으로 항복면과 파괴면을 형성하였다. 이때 항복면과 파괴면은 콘크리트의 소성변형이 누적되면 가변하는 것으로 가정하였다. 철근의 재료특성은 변형도에 의존적인 탄성/점소성모델을 이용하여 표현하였다. 표준고체요소의 성능저하를 방지하기 위하여 Hughes가 제시한 B bar법을 바탕으로 변형도-변위관계 행렬을 형성하였다. 동적 시간이력해석을 수행하기 위하여 안정적인 수렴성을 가지는 암시적인 Newmark법을 도입하였다. 마지막으로 시간이력해석을 통하여 콘크리트 균열변형도의 수준과 충돌하는 항공기의 종류에 따른 격납건물의 동적거동변화를 조사하고 이를 정량적으로 기술하였다.

• 한국지반환경공학회 논문집
• /
• 제13권8호
• /
• pp.35-43
• /
• 2012

널말뚝을 해안지역이나 도심지역에 건설하는 경우 주변에 위치한 횡방향 재하 말뚝의 영향권 내에 존재하게 되는 경우가 발생하게 되지만, 기존 설계방법에서는 이러한 영향에 대하여 고려하고 있지 않다. 본 연구를 통해 말뚝에 횡방향 하중이 재하되는 경우 근접한 널말뚝에 미치는 영향을 정량적으로 예측할 수 있는 방법을 제안하고자 한다. 상용프로그램인 ABAQUS를 이용하여 3차원 유한요소 모델을 만들었으며 지반 구성모델로는 Drucker-Prager 모델, 널말뚝과 말뚝은 선형탄성으로 거동하도록 모사하였다. 널말뚝의 휨강성, 말뚝과 널말뚝 간의 거리, 굴착깊이, 그리고 지반의 탄성계수 등 총 4가지 변수들을 사용하여 횡방향 재하 말뚝이 주변 널말뚝에 미치는 영향을 분석해 보았다. 수치해석 결과를 이용하여 널말뚝에 발생하는 최대 횡방향 변위 및 휨모멘트를 측정할 수 있는 간단한 식을 제시하였다.

• 한국전산구조공학회:학술대회논문집
• /
• 한국전산구조공학회 2005년도 춘계 학술발표회 논문집
• /
• pp.151-158
• /
• 2005

For the safety analysis of large structures such as nuclear containment buildings, we conventionally prefer to use analytical approach using finite element method rather than empirical test. Therefor, this paper is mainly focused to develop low-order solid finite element model with the elasto-plastic material model for the safety analysis of nuclear containment building. Drucker-Prager failure criteria in uncracked concrete and maximum tensile stress criteria in cracked concrete are used to model the constitutive behavior of concrete. The concrete material model takes into account the aspects of tensile strain, compression strength reduction of concrete and shear transfer to improve the accuracy of the finite element analysis. Finally, numerical simulation to compare the performance of the developed model with experimental results is employed. The numerical results in this study agree very well with the experimental data.

• International Journal of Railway
• /
• 제3권2호
• /
• pp.73-82
• /
• 2010

Global and local behaviors of a lightly RC shear walls are investigated in this paper. For the sake of cyclic behaviors, nominal ground accelerations of 0.15 g, 0.40 g and 0.55 g which associated with natural periods of the walls are applied as listed in French CAMUS-2000 shake table test. Modified Kent & Park model, Drucker-Prager model for concrete material and $Giufr\acute{e}$-Menegotto-Pinto model for rebar are used for time history analyses using fiber/solids elements respectively. Alternatively, Eulerian beam analysis are discussed by imposing inelastic hinges at the most possible plastic hinge location using modified Takeda's trilinear model with stiffness reduction. Relative displacements, base shears, bending moments of 5-story shear building with 36-tons of mass under bi-lateral seismic excitation are extracted and compared with EC-8, PS-92 and KBC-09 provisions. Multi-scaled degradation process; material damage, elemental fracture and structural failure in turn is discussed in the view of numerical accuracy, efficiency and limitation depending on three different model-based analyses.

• Computers and Concrete
• /
• 제12권1호
• /
• pp.65-77
• /
• 2013

This paper examines the dynamic response of an arch dam subjected to blast loading. A damage model is developed for three dimensional analysis of arch dams. The modified Drucker-Prager criterion is adopted as the failure criteria of the damage evolution in concrete. Then, Xiluodu arch dam serves as an example to simulate the failure behaviors of structures with the proposed model. The results obtained using the proposed model can reveal the reliability degree of the safe operation level of the high arch dam system as well as the degree of potential failure, providing a reliable basis for risk assessment and risk control.

• Interaction and multiscale mechanics
• /
• 제5권2호
• /
• pp.157-168
• /
• 2012

The dilatancy of granular materials has significant influence on its mechanical behaviors. The dilation angle is taken as a constant in conventional associated or non-associated flow rules based on Drucker-Prager yields theory. However, various experimental results show the dilatancy changes during progressive failure of granular materials. A non-associated flow rule with evolution of dilation angle is adopted in this study, and Cosserat continuum theory is used to describe the behaviors of granular materials for considering to some extent the its internal structure. Numerical examples focus on the bearing capacity and localization of granular materials, and results illustrate the capability and performance of the presented model in modeling the effect on failure behavior of granular materials.

• Computers and Concrete
• /
• 제18권1호
• /
• pp.99-112
• /
• 2016

Since the preservation of monuments is very important to human societies, different methods are required to preserve historic structures. In this paper, 3D model of arch stone bridge at Pont Saint Martin, Aosta, Italy, was simulated by 1660 integrated separate stones using ABAQUS$^{(R)}$ software to investigate the seismic susceptibility of the bridge. The main objective of this research was to study a method of preservation of the historical stone bridge against possible earthquakes using FRP techniques. The nonlinear behavior model of materials used theory of plasticity based on Drucker-Prager yield criterion. Then, contact behavior between the block and mortar was modeled. Also, Seismosignal software was used to collect data related to 1976 Friuli Earthquake Italy, which constitutes a real seismic loading. The results show that, retrofitting of the arch stone bridge using FRP techniques decreased displacement of stones of spandrel walls, which prevents the collapse of stones.

• Computers and Concrete
• /
• 제13권5호
• /
• pp.633-648
• /
• 2014

The seismic safety of concrete dams is one of the important problems in the engineering due to the vast socio-economic disasters which may be caused by collapse of these infrastructures. The accuracy of the risk evaluation associated with these existing dams as well as the efficient design of future dams is highly dependent on a proper understanding of their behaviour due to earthquakes. This paper develops an anisotropic damage model for arch dam under strong earthquakes. The modified Drucker-Prager criterion is adopted as the failure criteria of the dynamic damage evolution of concrete. Some process fields and other necessary information for the safety evaluation are obtained. The numerical results show that the seismic behaviour of concrete dams can be satisfactorily predicted.