• 콘크리트학회논문집
• /
• 제15권3호
• /
• pp.433-442
• /
• 2003

본 연구에서는 단조하중, 반복하중, 비례하중, 비례하지 않는 하중을 받는 콘크리트 구조물의 3차원 유한요소해석을 위한 비선형 아소성 콘크리트 모델을 개발하였다. 이 구성모델은 등가일축변형률 개념을 기초로 하여 3차원 구성관계를 세 개의 서로 독립된 등가일축 구성관계로 바꾸고 이들 통하여 콘크리트의 거동을 예측하도록 모델되었다. 일축 구성관계는 Willam-Warnke의 파괴면을 이용하여 주응력공간에서 구해진 최대 압축응력으로부터 결정되었다. 특히 중수압축을 따라 재하되는 하중에 대한 콘크리트의 비선형 특성을 예측하기 위하여 파괴면에 캡면을 도입하였다. 일축 구성관계는 Popovis와 Saenz의 모델을 근거로 하여 구속응력이 증가함에 따라 취성에서 연성으로 변화하는 현상을 묘사할 수 있도록 새롭게 유도하였다. 개발된 모델을 모델의 성능을 평가하기 위하여 여러 실험결과와의 비교를 시도하였다. 먼저 일정한 구속응력과 단조하중을 받는 실험결과와 비교하였고, 이축압축실험과 비례하지 않는 하중과 반복하중을 받는 삼축압축 실험결과와 비교하였다.

• 대한소아치과학회지
• /
• 제23권4호
• /
• pp.818-839
• /
• 1996

The strain gage, holographic and photoelastic analysis etc. have been used for stress analysis of prosthesis, orthodontic or orthopedic appliances and filling materials. But these methods has some limitation in analyzing the internal stress. The Finite Element Analysis has been proved to compensate this defect and widely used in this area. The purpose of this study was to compare the stress distributions of the various temporary filling methods being used in pulpotomy procedure. Three different models were designed according to temporary filling material and method: amalgam filling with ZOE base(Model I), amalgam filling with ZPC sub-base and ZOE(Model II), IRM filling only(Model III). The results of the experiment were as follows: 1. In model I under the load case 6 and 1, the significant stress was shown to be concentrated on the buccal portion of crown. 2. Model II showed the similar pattern of stress distribution to Model I. 3. In model III under load case 2, the stress was mainly distributed on the buccal cusp tip and buccal margin of filling material. In same model under the load case 3, the stress was distributed on the lingual cusp tip. 4. Based on the above data, IRM can be assumed to have advantage over the other tested materials in reducing the incidence of crown fracture by localized the stress within the filling materials.

• 한국지진공학회논문집
• /
• 제8권3호
• /
• pp.87-96
• /
• 2004

최근에 수행된 보 플랜지 절취형 (Reduced Beam Section, RBS) 내진 철골모멘트접합부의 실험 결과에 의하면, 보 웨브를 볼트 접합한 시험체는 보 웨브를 용접 접합한 시험체에 비해서 조기에 스캘럽을 가로지르는 취성파단이 발생하는 열등한 내진성능을 보였다. 실험결과에 의할 때, 이러한 접합부 취성파괴가 발생하는 주요 원인은 웨브 볼트의 슬립과 고전 휨이론에 의한 예측과는 전혀 다른 응력 전달메카니즘에 의한 스캘럽 부근의 응력집중 때문으로 사료된다. 이는 고전 휨이론에 기초한 전통적 보 웨브 볼트접합부의 설계법을 재검토할 필요가 있음을 시사하는 것이다. 본 연구를 통하여 고전 휨이론에 기초한 현행의 보 웨브 설계법에 문제가 있음을 지적하였다. 실험 및 해석결과를 바탕으로 RBS 접합부의 실제 응력전달경로에 부합되는 새로운 보 웨브 볼트접합 설계법을 제안하였다.

• Steel and Composite Structures
• /
• 제20권1호
• /
• pp.167-184
• /
• 2016

This paper presents the details of Finite Element (FE) analysis carried out to determine the limiting deformation capacity and failure mode of Laced Steel-Concrete Composite (LSCC) beam, which was proposed and experimentally studied by the authors earlier (Anandavalli et al. 2012). The present study attains significance due to the fact that LSCC beam is found to possess very high deformation capacity at which range, the conventional laboratory experiments are not capable to perform. FE model combining solid, shell and link elements is adopted for modeling the beam geometry and compatible nonlinear material models are employed in the analysis. Besides these, an interface model is also included to appropriately account for the interaction between concrete and steel elements. As the study aims to quantify the limiting deformation capacity and failure mode of the beam, a suitable damage model is made use of in the analysis. The FE model and results of nonlinear static analysis are validated by comparing with the load-deformation response available from experiment. After validation, the analysis is continued to establish the limiting deformation capacity of the beam, which is assumed to synchronise with tensile strain in bottom cover plate reaching the corresponding ultimate value. The results so found indicate about $20^{\circ}$ support rotation for LSCC beam with $45^{\circ}$ lacing. Results of parametric study indicate that the limiting capacity of the LSCC beam is more influenced by the lacing angle and thickness of the cover plate.

• Structural Engineering and Mechanics
• /
• 제32권2호
• /
• pp.251-267
• /
• 2009

Reinforced concrete (RC) structures consist of two different materials: concrete and steel bar. The stress transfer behaviour between the two materials through bond plays an important role in the load-carrying capacity of RC structures, especially when they subject to lateral load such as blast and seismic load. Therefore, bond and slip between concrete and reinforcement bar will affect the response of RC structures under such loads. However, in most numerical analyses of blast-induced structural responses, the perfect bond between concrete and steel bar is often assumed. The main reason is that it is very difficult to model bond slip in the commercial finite element software, especially in hydrodynamic codes. In the present study, a one-dimensional slide line contact model in LS-DYNA for modeling sliding of rebar along a string of concrete nodes is creatively used to model the bond slip between concrete and steel bars in RC structures. In order to model the bond slip accurately, a new approach to define the parameters of the one-dimensional slide line model from common pullout test data is proposed. Reliability and accuracy of the proposed approach and the one-dimensional slide line in modelling the bond slip between concrete and steel bar are demonstrated through comparison of numerical results and experimental data. A case study is then carried out to investigate the bond slip effect on numerical analysis of blast-induced responses of a RC column. Parametric studies are also conducted to investigate the effect of bond shear modulus, maximum elastic slip strain, and damage curve exponential coefficient on blast-induced response of RC columns. Finally, recommendations are given for modelling the bond slip in numerical analysis of blast-induced responses of RC columns.

• Journal of Plant Biology
• /
• 제36권2호
• /
• pp.127-132
• /
• 1993

Self-incompatibility in Brassica campestris is controlled by multi-allele system in a single genetic locus, the S locus, and it is elucidated that S-glycoproteins are S gene products. In this experiments, we examined the genetic mode(pollen tube behavior and segregation of S-glycoprotein), characteristic of S-glycoproteins and DNA constitution within nuclear genome on S gene family that unexplained by single locus model, and investigated the segregation pattern of S-glycoproteins in bred F1 generation. By diallel cross among the 15 plants within one family the existence of three types of homozygotes and three types of heterozygotes were observed, and segregation of S-allele could not explained by single locus model. From the results of IEF-immunoblot analysis for non-segregated individual plant, the segregation pattern of S specific bands was corresponded with results of diallel cross except with one case(SaSa genotype). The molecular weight of 6 different S-genotype varied in near by 50 kD, and each genotype expressed with 2 or 3 bands. Specific bands in SaSa, SbSb, ScSc has almost similar molecular weight between them. Southern analysis of genomic DNA probed with S-glycoprotein cDNA for 6 different genotypes revealed that there are clear difference in polymorphism, multiple bands of hybridization, when restriction enzymes of EcoR I were used. It could be assumed that there are several sequences related to the S-glycoprotein structural genes within their nuclear genome. Therefore, we suggested the possibilities that S-allele system could be controlled by multi-locus, that dominance-recessive interactions could be explained by modifier gene or supressor gene based on the results of abnormal segregation of S-glycoprotein in bred F1. The F2 analyses are progressing in now.

• 대한기계학회논문집
• /
• 제11권3호
• /
• pp.376-385
• /
• 1987

본 연구에서는 평면응력 파괴인성치의 거동에 관한 일련의 연구로서 위와 같 은 점을 고려하여 얇은 두께의 시험편을 이용하여 z의 변화에 대한 평면응력 파괴인성 치와 J저항곡선을 실험적으로 고찰하였으며 크랙성장을 고려한 J적분식도 검토하였다. 크랙길이는 하중제거 컴플라이언스법에 의하여 구하였고, ASTM E813의 방법으로J= .sigma.$_{f}$ .DELTA.(2ａ)인 크랙둔화선과 J저항곡선의 교점에서 구한 J적분값을 J$_{c}$로 정 의하였다. 또한, 재료를 변형경화재료로 가정하여 HRR응력변형율장의 특성을 이용 하여 J적분값을 구한 후 실험치와 상호 비교 검토하였다.이때 입력자료는 실험치의 그것과 동일하게 하였다. 동시에 z의 변화에 대한 T의 변화도 함께 고찰하였다.다.

• 콘크리트학회지
• /
• 제8권6호
• /
• pp.223-234
• /
• 1996

본 논문에서는 단조증가하중을 받는 철근 및 프리스트레스트 콘크리트 슬래브의 비선형거동, 즉 탄성, 비탄성, 극한영역에 이르기까지의 모든 하중이력에 대한 응력-변형도 관계와 균열의 진행 및 철근 및 텐던과 콘트리트의 응력과 변형도 등을 정확히 해석할 수 잇는 해석법의 제시를 목적으로 한다. 이러한 목적을 위하여 본 연구에서는 재료적 및 기하학적 비선형성을 고려하였다. 기하학적 비선형성은 Von Karman의 가정에 기본을 둔 total Lagrangian formulation에 의해 고려하였으며 재료적 비선형성에 대해서는 균열콘크리트에대한 인장, 압축, 전단모델과 콘크리트 중에 있는 철근 및 텐던모델을 조합하여 고려하였다. 이에 대한 콘크리트의 균열모델로서는 분산균열모델을 사용하였으며, 철근 및 텐던에 대해서는 1축 응력상태로 가정하여 등가의 분산분포된 철근 및 텐던층으로 모델화하였다. 본 논문에서 제안한 해석방법의 타당성을 검증하기 위하여 몇 개의 실험치를 해석치와 비교.검토한 결과, 본 논문의 해석방법에 의하면 철근 및 프리스트레스트 콘크리트 슬래브의 비선형거동을 보다 정확하게 예측할 수 있었다.

• 한국해양공학회지
• /
• 제23권4호
• /
• pp.69-77
• /
• 2009

Structural analysis of a brake shoe for commercial vehicle was performed using finite element method. Since the strength of a brake shoe is affected by the magnitude and distribution shape of the contact pressure with the drum, the contact pressure between the shoe friction material and drum was calculated using a 2-Dimensional non-linear contact analysis in a state. And the brake was actuated by input air pressure and the drum of it was calculated both stationary and dynamic based on forced torque applied to the drum during the static state analysis. The results of the above analysis were then used as the load boundary conditions for a 3-Dimensional shoe model analysis to determine the maximum strain on the shoes. In the analysis model, the values of tensile test were used for the material properties of the brake shoes and drum, while the values of compression test were used for the friction material. We assumed it as linear variation, even though the properties of friction material were actually non-linear. The experiments were carried out under the same analysis conditions used for fatigue test and under the same brake system which equipped with a brake drum based on the actual axle state in a vehicle. The strains were measured at the same locations where the analysis was performed on the shoes. The obtained results of the experiment matched well with those from the analysis. Consequently, the model used in this study was able to determine the stress at the maximum air pressure at the braking system, thereby a modified shoe model in facilitating was satisfied with the required endurance strength in the vehicle.

• 마이크로전자및패키징학회지
• /
• 제9권4호
• /
• pp.35-45
• /
• 2002

열하중에 의한 언더필/칩 계면의 응력을 유한요소법을 이용하여 구하였다. 먼저 실리카 입자의 부피 분율이 언더필 재료의 물성에 미치는 영향을 알아보기 위하여 세 가지 재료 세트에 대하여 실리카 입자의 부피 분율에 따른 영계수, 포아슨비, 영팽창 계수를 Mori-Tanaka방법을 이용하여 계산하였고, 언더필과 칩이 형성하는 edge및 wedge에 대한 singularity를 계산하였다. 그 다음에는 앞에서 계산한 재료물성치를 가지고 실리카 입자의 부피 분율에 따른 언더필/칩 계면의 응력을 몇 가지 플립칩 형상에 대하여 살펴보았다. 언더필이 균일한 재료라는 가정과 플립칩 어셈블리를 구성하고 있는 재료들이 선형탄 성적거동을 하고 등방성을 보이며 그들의 성질이 온도에 무관하다는 가정 하에 다섯 가지의 플립칩 어셈블리 모델이 고려되었다.