Stochastic finite element based reliability analysis of steel fiber reinforced concrete (SFRC) corbels

Mehmet Eren Gulsan,Abdulkadir Cevik,AhmetEminKurtoglu 사단법인 한국계산역학회 2015 Computers and Concrete, An International Journal Vol.15 No.2

In this study, reliability analyses of steel fiber reinforced concrete (SFRC) corbels based on stochastic finite element were performed for the first time in literature. Prior to stochastic finite element analysis, an experimental database of 84 sfrc corbels was gathered from literature. These sfrc corbels were modeled by a special finite element program. Results of experimental studies and finite element analysis were compared and found to be very close to each other. Furthermore experimental crack patterns of corbel were compared with finite element crack patterns and were observed to be quite similar. After verification of the finite element models, stochastic finite element analyses were implemented by a specialized finite element module. As a result of stochastic finite element analysis, appropriate probability distribution functions (PDF’s) were proposed. Finally, coefficient of variation, bias and strength reduction (resistance) factors were proposed for sfrc corbels as a consequence of stochastic based reliability analysis.

Development of Finite Element Analysis for Intermediate Length Coupling Beams Considering Bond‑Slip Interface

Abu Bakar Nabilah,Chan Ghee Koh,Abd. Karim Izian,Farah Nora Aznieta Abd. Aziz 한국콘크리트학회 2020 International Journal of Concrete Structures and M Vol.14 No.5

Finite element analysis is performed on four reinforced concrete coupling beams of intermediate length using 2-D plane stress elements, under monotonic load up to failure. The model is verified using the results from (Nabilah and Koh in KSCE J Civil Eng 21:2807–2813, 2017). The bond-slip interface for the longitudinal reinforcement is modeled in the finite element, as it is found that it better predicts the load-deformation behavior compared to perfect bond. The comparison between finite element analysis and the experiment found that the model is able to predict the overall behavior of the structure, especially the maximum load capacity. The maximum deformation and the shear deformation from the finite element analysis are found to be underestimated, due to the inability of the model to predict shear deformation accurately. Flexural deformation (due to flexure and slip) is found to be well predicted, as the bond-slip behavior is modeled in the analysis. Generally, the shear deformation and slip are found to be significant in the intermediate length coupling beam and should not be ignored in the analysis. Finally, the effective stiffness prediction using finite element analysis is found to be overestimated and should be determined instead using existing equations.

箱形보의 有限要素解析에 관한 硏究

이임섭 동의공업대학 1999 論文集 Vol.25 No.1

In buildings and bridges, ever greater use is being made girders which can be considered thin-walled closed section girder, i.e., box-beam because of their proportions and high torsional stiffness, so I have studied box-beam used the finite element method as assembly of flat elements. For the analysis, the following assumptions are made. 1) the used plates are homogeneous and isotropic, and Hooke's law hold, i.e., stress is proportional to strain. 2) Navier hypothesis hold, i.e., plane sections remain plane and thus the strains are proportional to the neutral axis. 3) Kirchhof-Love hypotheses hold, which are used in the shell analysis. 4) In the formulation of the plate bending element, Mindlin's assumptions hold. In the finite element analysis, the box-beam structure was idealized by the triangular flat elements for the webs and flanges. The results of this study are as follows. 1) compared with the convergency speed of the result of the analysis, the case of using quadrilateral element is faster than that of triangular. 2) In the case of the low-stressed condition, the result of the analysis of using triangular element and that of quadrilateral element were converged to the same value by the subdividing the element, on the contrary in the case of the high-stressed condition, the result of the analysis of using triangular element and that of quadrilateral element were not converged to the same value. 3) The more subdivide the element, the better the result of the analysis was converged into a constant value, but that was not exact solution.

Seismic analysis of the APR1400 nuclear reactor system using a verified beam element model

Park, Jong-beom,Park, No-Cheol,Lee, Sang-Jeong,Park, Young-Pil,Choi, Youngin Elsevier 2017 Nuclear engineering and design Vol.313 No.-

<P><B>Abstract</B></P> <P>Structural integrity is the first priority in the design of nuclear reactor internal structures. In particular, nuclear reactor internals should be designed to endure external forces, such as those due to earthquakes. Many researchers have performed finite element analyses to meet these design requirements. Generally, a seismic analysis model should reflect the dynamic characteristics of the target system. However, seismic analysis based on the finite element method requires long computation times as well as huge storage space. In this research, a beam element model was developed and confirmed based on the real dynamic characteristics of an advanced pressurized water nuclear reactor 1400 (APR1400) system. That verification process enhances the accuracy of the finite element analysis using the beam elements, remarkably. Also, the beam element model reduces seismic analysis costs. Therefore, the beam element model was used to perform the seismic analysis. Then, the safety of the APR1400 was assessed based on a seismic analysis of the time history responses of its structures. Thus, efficient, accurate seismic analysis was demonstrated using the proposed beam element model.</P> <P><B>Highlights</B></P> <P> <UL> <LI> A simplified beam element model is constructed based on the real dynamic characteristics of the APR1400. </LI> <LI> Time history analysis is performed to calculate the seismic responses of the structures. </LI> <LI> Large deformations can be observed at the in-phase mode of reactor vessel and core support barrel. </LI> </UL> </P>

시간영역에서 유한요소법을 이용한 지진시의 지반응답해석

류희룡,이재영,박영택,You, Hee-Yong,Lee, Jae-Young,Park, Young-Tack 한국농공학회 2006 한국농공학회논문집 Vol.48 No.6

The finite element method is a practical tool to compute the response of the irregularly layered soil deposit to the base-rock motions. The method is useful not only in estimating the interaction between the structure and the surrounding soil as a whole and the local behavior of the contacting area in detail, but also in predicting the resulting behavior of the superstructure affected by such soil-structure interactions. However, the computation of finite element analysis is marched in the time domain (TD), while the site response analysis has been carried out mostly in the frequency domain (FD) with equivalent linear analysis. This study is intended to compare the results of the TD and FD analysis with focus on the peak response accelerations and the predominant frequencies, and thus to evaluate the applicability and the validity of the finite element analysis in the site response analysis. The comparison shows that one can obtain the results very close to that of FD analysis, from the finite element analysis by including sufficiently large width of foundation in the model and further by applying partial mode superposition. The finite element analysis turned out to be well agreeing with FD analysis in their computed results of the peak acceleration and the acceleration response spectra, especially at the surface layer.

비선형 유한요소해석 프로그램을 이용한 차체 구조물의 동강성 및 정강성 해석

김성현(Sunghyun Kim),김형일(Hyungil Kim),변형배(Hyungbai Byun),김동석(Dongseok Kim),이용훈(Yonghoon Lee),김일환(Ilhwan Kim),허승진(Seung Jin Heo),임홍재(Hong Jae Yim) 한국자동차공학회 2011 한국자동차공학회 부문종합 학술대회 Vol.2011 No.5

In this study, dynamic stiffness analysis and static stiffness analysis were conducted by using nonlinear finite element analysis program and linear finite element analysis respectively to compare the results and to confirm reliability about results of nonlinear finite element analysis program. First, dynamic stiffness analysis has been performed on side out panel, crash box, sub-frame and BIW(Body In White) that has been connected with front bumper, rear bumper and sub-frame. Second, static stiffness analysis has been conducted on crash box and hood that has been modeled with spot weld elements and rigid body elements. Consequently, differences of dynamic and static stiffness analysis results through nonlinear finite element analysis program and linear finite element analysis were below 6 % but difference was more than 6 % as to dynamic stiffness of BIW.

Micro-computed tomography 영상을 이용한 치아의 컴퓨터 3차원 모델 생성 및 유한요소 분석에의 응용

노세라 ( Se Ra Noh ),김명수 ( Myong Soo Kim ) 조선대학교 치의학연구원 2013 Oral Biology Research (Oral Biol Res) Vol.37 No.2

Purpose: Among mechanical stress analysis methods of teeth and prosthetic appliances, finite element analysis using computer generated 3-dimensional models has been widely applied. We tested a new method to generate 3-dimensional tooth models which can be applied to finite element analysis. Materials and Methods: Three-dimensional tooth models were generated from micro-computer tomography images using 3-dimensional graphic software and computer aided design (CAD) software, and the models were applied to finite element analysis. Results: The models generated using this method better mimicked the anatomical structure of natural teeth than those generated by other methods. As a sample case, a 3-dimensional model of an upper first molar tooth with a class I cavity was generated using 3-dimensional CAD software. Finite element analysis was carried out using this model by assuming that the cavity was filled with three different materials. Conclusion: The method used in the present study yielded high-quality 3-dimensional models of teeth that can easily be applied to mechanical stress analysis using finite element analysis and other dental applications.

환경하중과 B777 항공기 기어하중을 이용한 공항 콘크리트 포장의 최대인장응력 예측모형 개발

김동혁,마경훈,박해원,정진훈 한국도로학회 2018 한국도로학회논문집 Vol.20 No.5

PURPOSES : Previously, airport concrete pavement was designed using only aircraft gear loading without consideration of environmental loading. In this study, a multiple-regression model was developed to predict maximum tensile stress of airport concrete pavement based on finite element analysis using both environmental and B777 aircraft gear loadings. METHODS: A finite element model of airport concrete pavement and B777 aircraft main gears were fabricated to perform finite element analysis. The geometric shape of the pavement, material properties of the layers, and the loading conditions were used as input parameters for the finite element model. The sensitivity of maximum tensile stress of a concrete slab according to the variation in each input parameter was investigated by setting the ranges of the input parameters and performing finite element analysis. Based on the sensitivity analysis results, influential factors affecting the maximum tensile stress were found to be used as independent variables of the multi regression model. The maximum tensile stresses predicted by both the multiple regression model and finite element model were compared to verify the validity of the model developed in this study. RESULTS: As a result of the finite element analysis, it was determined that the maximum tensile stress developed at the bottom of the slab edge where gear loading was applied in the case that environmental loading was small. In contrast, the maximum tensile stress developed at the top of the slab center situated between the main gears in the case that the environmental loading got larger. As a result of the sensitivity analysis and multiple regression analysis, a maximum tensile stress prediction model was developed. The independent variables used included the joint spacing, slab thickness, the equivalent linear temperature difference between the top and bottom of the slab, the maximum take-off weight of a B777 aircraft, and the composite modulus of the subgrade reaction. The model was validated by comparing the predicted maximum tensile stress to the result of the finite element analysis. CONCLUSIONS : The research shown in this paper can be utilized as a precedent study for airport concrete pavement design using environmental and aircraft gear loadings simultaneously.

Staged Finite Element Modeling with Coupled Seepage and Stress Analysis

Lee, Jae-Young Computational Structural Engineering Institute of 2010 한국전산구조공학회논문집 Vol.23 No.6

This paper proposes an approach for staged finite element modeling with coupled seepage and stress analysis. The stage modeling is based on the predefined inter-relationship between the base model and the unit stage models. A unit stage constitutes a complete finite element model, of which the geometries and attributes are subject to changes from stage to stage. The seepage analysis precedes the mechanical stress analysis at every stage. Division of the wet and dry zone and the pore pressures are evaluated from the seepage analysis and used in determining input data for the stress analysis. The results of the stress analysis may also be associated with the pore water pressures. For consolidation analysis, the pore pressure and the displacement variables are mixed in a coupled matrix equation. The time marching solution produces the dissipation of excess pore pressure and variation of stresses with passage of time. For undrained analysis, the excess pore pressures are computed from the stress increment due to loading applied in the unit stage and are used in revising the hydraulic head. The solution results of a unit stage are inherited and accumulated to the subsequent stages through the relationship of the base model and the individual unit stages. Implementation of the proposed approach is outlined on the basis of the core procedures, and numerical examples are presented for demonstration of its application.

Finite element analysis of long-term changes of the breast after augmentation mammoplasty: Implications for implant design

Myung, Yujin,Lee, Jong-Gu,Cho, Maenghyo,Heo, Chan Yeong Korean Society of Plastic and Reconstructive Surge 2019 Archives of Plastic Surgery Vol.46 No.4

The development of breast implant technology continues to evolve over time, but changes in breast shape after implantation have not been fully elucidated. Thus, we performed computerized finite element analysis in order to better understand the trajectory of changes and stress variation after breast implantation. The finite element analysis of changes in breast shape involved two components: a static analysis of the position where the implant is inserted, and a dynamic analysis of the downward pressure applied in the direction of gravity during physical activity. Through this finite element analysis, in terms of extrinsic changes, it was found that the dimensions of the breast implant and the position of the top-point did not directly correspond to the trajectory of changes in the breast after implantation. In addition, in terms of internal changes, static and dynamic analysis showed that implants with a lower top-point led to an increased amount of stress applied to the lower thorax. The maximum stress values were 1.6 to 2 times larger in the dynamic analysis than in the static analysis. This finding has important implications for plastic surgeons who are concerned with long-term changes or side effects, such as bottoming-out, after anatomic implant placement.