SB Charite III ® 인공 추간판이 설치된 기능 척추 단위의 하중 분포: 유한 요소 분석 연구

윤상훈,김현집 대한척추신경외과학회 2010 Neurospine Vol.7 No.4

Objective: To evaluate the effects of SB Charite III® artificial disc implantation on the biomechanics of functional spinal units. Methods: A nonlinear intact osteoligamentous three-dimensional finite element model of L4-L5 was developed using 1-mm CT scan data from a human volunteer, and the material properties of each element were determined. The model was validated using biomechanical data. A model that was implanted with SB Charite III® artificial discs via an anterior approach was also developed. The stresses and strains of the vertebral bodies and surrounding spinal ligaments were investigated. The implanted model was compared to the intact model in terms of range of motion, force on facet joints with flexion-exten- sion, lateral bending, and axial rotation under 400N preloading. Results: There were no significant differences between the findings of this finite element study and other reports in the literature. Our analytical method proved useful method for the biomechanical evaluation of the effects of artificial disc implan- tation. The implanted model revealed an increased range of motion in flexion-extension, lateral bending, and axial rotation compared to the intact model. The stresses on facets were greater in the implanted model than in the intact model. Conclusion: The model that was implanted with artificial discs showed increased segmental motion and stress on the facet joints compared to the intact model. We hypothesize that the removal of the anterior longitudinal ligament is the major cause of increased segmental motion and stress on the facet joints in the implanted model. The development of new artificial discs should focus on compensating for these unwanted results. Objective: To evaluate the effects of SB Charite III® artificial disc implantation on the biomechanics of functional spinal units. Methods: A nonlinear intact osteoligamentous three-dimensional finite element model of L4-L5 was developed using 1-mm CT scan data from a human volunteer, and the material properties of each element were determined. The model was validated using biomechanical data. A model that was implanted with SB Charite III® artificial discs via an anterior approach was also developed. The stresses and strains of the vertebral bodies and surrounding spinal ligaments were investigated. The implanted model was compared to the intact model in terms of range of motion, force on facet joints with flexion-exten- sion, lateral bending, and axial rotation under 400N preloading. Results: There were no significant differences between the findings of this finite element study and other reports in the literature. Our analytical method proved useful method for the biomechanical evaluation of the effects of artificial disc implan- tation. The implanted model revealed an increased range of motion in flexion-extension, lateral bending, and axial rotation compared to the intact model. The stresses on facets were greater in the implanted model than in the intact model. Conclusion: The model that was implanted with artificial discs showed increased segmental motion and stress on the facet joints compared to the intact model. We hypothesize that the removal of the anterior longitudinal ligament is the major cause of increased segmental motion and stress on the facet joints in the implanted model. The development of new artificial discs should focus on compensating for these unwanted results.

깊은 신경망을 이용한 구조물의 유한요소모델 업데이팅

공밍,박원석 대한토목학회 2019 대한토목학회논문집 Vol.39 No.1

The finite element model updating can be defined as the problem of finding the parameters of the finite element model which gives theclosest response to the actual response of the structure by measurement. In the previous researches, optimization based methods have been developed to minimize the error of the response of the actual structure and the analytical model. In this study, we propose an inverse eigenvalue problem that can directly obtain the parameters of the finite element model from the target mode information. Deep Neural Networks are constructed to solve the inverse eigenvalue problem quickly and accurately. As an application example of the developed method, the dynamic finite element model update of a suspension bridge is presented in which the deep neural network simulating the inverse eigenvalue function is utilized. The analysis results show that the proposed method can find the finite element model parameters corresponding to the target modes with very high accuracy. 유한요소모델 업데이팅은 계측에 의한 구조물의 실제 응답과 가장 가까운 응답을 내는 유한요소모델의 매개변수를 찾는 문제로 정의할 수 있다. 기존 연구에서는 실 구조물과 해석 모델의 응답의 오차를 최소화하는 최적화에 기반 한 방법이 개발되었다. 이 연구에서는 목표 모드 정보로부터 유한요소 모델의 매개변수를 직접 얻을 수 있는 역 고유치 문제를 구성하고 역 고유치 문제를 빠르고 정확하게 풀기 위한 깊은 신경망(Deep Neural Network)을 구성하는 방법을 제안한다. 개발한 방법의 적용 예로서 현수교의 역 고유치 함수를 모사하는 신경망을 이용한 동적 유한요소모델 업데이트를 보인다. 해석 결과 제시한 방법은 매우 높은 정확도로 목표 모드에 대응하는 매개변수를 찾아낼 수 있음을 보였다.

Finite Element Model Updating of a Simply Supported Skewed PSC I-girder Bridge using Hybrid Genetic Algorithm

정대성,김철영 대한토목학회 2013 KSCE Journal of Civil Engineering Vol.17 No.3

Hybrid Genetic Algorithm (HGA) which combines the genetic algorithm as a global optimization and the simplex method as a local optimization is proposed for a finite element model updating of a real prestressed concrete bridge structure. In order to minimize the updating error between the measurement and the finite element model updating result, objective functions which are combinations of fitness functions based on the natural frequency, the mode shape and the static displacement are introduced. And an interface tool is also developed in order to utilize various element library and numerical analysis tools which are provided by commercial finite element and numerical analysis programs. A simply supported skewed PSC girder bridge which has 30 m span length is selected for the verification of the proposed FE model updating algorithm. Static vehicle loading test and forced vibration test by traveling vehicle as well as ambient vibration test were carried out to obtain the reference measurement data for numerical updating. A grillage model is used for the finite element analysis. Effect of the spring element to simulate the realistic support condition which is not perfectly free or restrained in real situation as well as that of the objective function on the updating accuracy are studied. From the result of parametric study, it is investigated that the use of spring element for support condition is effective to minimize the updating error for natural frequency and mode shape. Furthermore, including the static displacement fitness function together with those of dynamic properties may improve the global behavior of updated finite element model. It is concluded that the hybrid genetic algorithm proposed in this study is a very effective finite element model updating method to find an accurate result in updating real bridge structure based on measured data.

FRP 기둥 재킷 시스템이 보강된 지진 취약 철근콘크리트 건축물의 유한요소해석

신지욱,이상열,지동현,Shin, Jiuk,Lee, Sang-Youl,Ji, Dong-Hyun 한국공간구조학회 2021 한국공간구조학회지 Vol.21 No.2

This study develops finite element models for seismically-deficient reinforced concrete building frame retrofitted using fiber-reinforced polymer jacketing system and validates the finite element models with full-scale dynamic test for as-built and retrofitted conditions. The bond-slip effects measured from a past experimental study were modeled using one-dimensional slide line model, and the bond-slip models were implemented to the finite element models. The finite element model can predict story displacement and inter-story drift ratio with slight simulation variation compared to the measured responses from the full-scale dynamic tests.

초기수위해석을 이용한 2차원 유한요소모형의 개선

김상호,오현욱,최승용,한건연 한국방재학회 2012 한국방재학회논문집 Vol.12 No.6

Initial condition of water surface elevation with boundary condition is required to simulate two-dimensional finite element model. In general, in order to perform two-dimensional finite element model, unrealistic initial water surface elevation which is above all-terrain bed elevation and unmatched downstream boundary condition is used, which will make it difficult to perform stably. In this study, the water surface elevation caused by the actual river bed rather than a fixed value is applied automatically as the initial condition of a two-dimensional finite element model. The algorithm to automatically extract river cross section for simulation of one-dimensional hydraulic analysis from a two-dimensional element mesh is developed. And the accuracy of twodimensional model tried to upgrade by improving the two-dimensional finite element model, which used the results of one-dimensional non-uniform analysis as the initial condition of two-dimensional model. To examine the applicability of an improved model,the model was applied to the rectangular channel with a rapid slope, mild-steep slopes channel, steep-mild slopes channel and Han River. The results of the model, which the initial water surface elevation of one-dimensional flow analysis is used, were more stably converged than those of existing model and the stability of numerical computation was improved by using physical initial water surface elevation. 2차원 유한요소모형을 수행하기 위해서는 경계조건과 함께 대상구간에 대한 초기수위를 지정하여야 한다. 일반적으로 2차원모형을 수행하기 위해 하상의 모든 지형고보다 높으면서 하류단 경계수위와 일치하지 않는 비현실적인 초기수위를 사용하게 되며, 이는 모형의 안정적인 모의를 어렵게 한다. 본 논문에서는 2차원 모형의 초기수위가 고정값이 아니라 실제 하상경사로 인해 발생하는 하천의 수위를 사용하여 2차원 유한요소모형에 자동 적용되도록 하였다. 이를 위해 2차원 요소망으로부터 1차원동수역학 해석을 수행할 수 있는 하상자료를 자동으로 추출하는 알고리듬을 개발하였고, 2차원 모형 내에서 모의된 1차원 부정부등류 해석 결과가 2차원 모형의 전체구간에 대한 초기수위로 적용될 수 있도록 2차원 유한요소모형을 개선함으로써 모형의정확도를 향상시키고자 하였다. 개선된 모형의 적용성을 검토하기 위해서 급격한 경사를 가지는 직사각형 하도, 완경사-급경사하도 그리고 급경사-완경사 하도와 같은 가상하도 및 한강 본류구간에 대해 흐름해석을 실시하였다. 그 결과 기존의 2차원 유한요소모형의 결과보다 1차원 흐름해석 결과를 초기수위로 이용한 모형의 결과가 보다 안정적으로 해에 수렴하고 있는 것을 확인함으로써 물리적인 초기 수위값의 부여로 인한 수치계산의 안전성이 향상되었음을 확인할 수 있었다.

Modeling of helically stranded cables using multiple beam finite elements and its application to torque balance design

Kim, Sung-Yun,Lee, Phill-Seung Elsevier 2017 Construction and Building Materials Vol.151 No.-

<P><B>Abstract</B></P> <P>In this paper, a method for the effective modeling of helically stranded cables for which multiple beam finite elements (FE) are used is presented, and a design procedure for the torque balance of the cables using the beam FE model is proposed. Regarding the beam modeling, the wire-to-wire contacts and the elastoplastic material behavior are considered. The proposed beam model is advantageous because the accuracy of the corresponding numerical results is as good as that of the full solid FE model, while the computational cost is significantly reduced. Using the beam FE model, the mechanical behavior of helically stranded cables is analyzed under axial and transverse loadings. The numerical results are compared with those of full solid FE models and available experimental results, where accuracy and computational cost are investigated. This paper also proposes a practical procedure for torque balance design of helically stranded cables using the proposed beam FE model.</P> <P><B>Highlights</B></P> <P> <UL> <LI> A new FE modeling method of helically stranded cables is proposed. </LI> <LI> Multiple beam finite elements are adopted for the new FE modeling. </LI> <LI> The beam FE model is very effective in terms of accuracy and computational efficiency. </LI> <LI> Using the beam FE model, a practical procedure for torque balance design is presented. </LI> </UL> </P>

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>

Vibration based damage detection in a scaled reinforced concrete building by FE model updating

Temel Türker,Alemdar Bayraktar 사단법인 한국계산역학회 2014 Computers and Concrete, An International Journal Vol.14 No.1

The traditional destructive tests in damage detection require high cost, long consuming time, repairing of damaged members, etc. In addition to these, powerful equipments with advanced technology have motivated development of global vibration based damage detection methods. These methods base on observation of the changes in the structural dynamic properties and updating finite element models. The existence, location, severity and effect on the structural behavior of the damages can be identified by using these methods. The main idea in these methods is to minimize the differences between analytical and experimental natural frequencies. In this study, an application of damage detection using model updating method was presented on a one storey reinforced concrete (RC) building model. The model was designed to be 1/2 scale of a real building. The measurements on the model were performed by using ten uni-axial seismic accelerometers which were placed to the floor level. The presented damage identification procedure mainly consists of five steps: initial finite element modeling, testing of the undamaged model, finite element model calibration, testing of the damaged model, and damage detection with model updating. The elasticity modulus was selected as variable parameter for model calibration, while the inertia moment of section was selected for model updating. The first three modes were taken into consideration. The possible damaged members were estimated by considering the change ratio in the inertia moment. It was concluded that the finite element model calibration was required for structures to later evaluations such as damage, fatigue, etc. The presented model updating based procedure was very effective and useful for RC structures in the damage identification.

Review of the finite element models for a structural integrity evaluation of the sodium-cooled fast reactor high temperature piping

Chang-Gyu Park,Young-Sang Joo,김종범 대한기계학회 2012 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.26 No.9

We compared the structural analysis feature of finite element (FE) models for the structural integrity evaluation of the sodium-cooled fast reactor (SFR) high temperature piping and to evaluate the structural integrity against the typical duty cycle event. To evaluate the structural integrity of the high temperature piping per ASME Subsection NH rules, the structural analysis should be carried out first by using a 3-dimensional structural model. The object FE models under consideration in this study are pipe element model, 3-D full model,and 3-D simplified model. The pipe element model is based on the 3-D beam element and effective in understanding overall deformation but less favorable to the detailed stress distribution. The 3-D full model consists of solid structure as well as the contained coolant inside the piping structure with the fluid element. The 3-D simplified model consists of structure shape only, but its material properties are recalculated to reflect the coolant weight effect. The loading conditions for the structural analyses are the mechanical load including dead weight and steady state thermal load. From the analysis results, the piping element model shows the smallest stress intensity, and the required time for FE analysis is also the shortest. The 3-D simplified model shows the most conservative stress intensity output but its calculation time is less than the 3-D full model.

Analysis and design of demountable embedded steel column base connections

Dongxu Li,Brian Uy,Vipul Patel,Farhad Aslani 국제구조공학회 2017 Steel and Composite Structures, An International J Vol.23 No.3

This paper describes the finite element model for predicting the fundamental performance of embedded steel column base connections under monotonic and cyclic loading. Geometric and material nonlinearities were included in the proposed finite element model. Bauschinger and pinching effects were considered in the simulation of embedded column base connections under cyclic loading. The degradation of steel yield strength and accumulation of plastic damage can be well simulated. The accuracy of the finite element model is examined by comparing the predicted results with independent experimental dataset. It is demonstrated that the finite element model accurately predicts the behaviour and failure models of the embedded steel column base connections. The finite element model is extended to carry out evaluations and parametric studies. The investigated parameters include column embedded length, concrete strength, axial load and base plate thickness. Moreover, analytical models for predicting the initial stiffness and bending moment strength of the embedded column base connection were developed. The comparison between results from analytical models and those from experiments and finite element analysis proved the developed analytical model was accurate and conservative for design purposes.