• Title, Summary, Keyword: 역해석

### Automobile Collision Reconstruction Using Post-Impact Velocities and Crush Profile (충돌 후 속도와 충돌 변형으로부터 자동차 충돌 재구성)

• 한인환
• Journal of Korean Society of Transportation
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• v.18 no.4
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• pp.107-115
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• 2000
• We suggest a method which solves the planar, two vehicle collision reconstruction problem. The method based on the Principle of impulse and momentum determines the pre-impact velocity components from Post-impact velocity components, vehicle Physical data and collision geometry. A novel feature is that although the impact coefficients such as the restitution coefficient and the impulse ratio are unknown, the method can estimate automatically the coefficients and calculate the pre-impact velocity components. This reverse calculation is important for vehicle accident reconstruction, since the pre-impact velocities are unknown and Post-impact Phase is the starting Point in a usual collision analysis. However. an inverse solution is not always Possible with the analytical rigid-body impact model. Mathematically, one does not exist under the common velocity condition. On the other hand, our method has a capability of reverse calculation under the condition if the absorbed energy during the collision process can be estimated using the crush profile. To validate the developed collision reconstruction a1gorithm, we use car-to-car collision test results. The analysis and experimental results agree well in the impact coefficients and the Pre-impact velocity components.

### Electric Resistive Tomography using Finite Element Method and Genet (유한요소법과 유전 알고리즘을 이용한 전기비저항 탐사법의 저항역산)

• Lim, Sung-Ki;Kim, Min-Kyu;Kim, Hong-Kyu;Jung, Hyun-Kyo
• Proceedings of the KIEE Conference
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• pp.3-5
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• 1997
• 지구 물리학이나 의공학 분야등에서 이용되왔던 전기비저항 탐사법은 관심 영역에 전류 입력을 가한 후, 그에 대한 전압 응답을 측정하여 관심 영역 내의 전기비저항 분포를 규명하는 방법으로서 역해석 문제의 범주에 포함된다. 따라서 일반적인 역해석 문제가 지니고 있는 해의 존재성, 유일성, 그리고 측정 데이터에 대한 해의 연속적 의존성이라는 기본적 문제들을 가지게된다. 이러한 역해석 문제의 해결에는 정확한 정해석 풀이법과 효율적인 역해석 방법이 요구되어진다. 본 논문에서는 정해석 방법으로 유한요소법을, 역해석 방법으로는 전체 최적점을 발견할 가능성이 높은 유전 알고리즘을 최적화 방법으로 사용하였다. 기존의 역해석 문제의 해결책으로 제시되어왔던 기울기 방법에 기반한 결정론적 최적화 알고리즘들이 지니고 있는 국소해로의 수렴, 즉 단순한 전기비저항 분포의 불연속성 확인이라는 한정된 정보의 획득을 넘어서 실제 전기비저항 분포와 가장 가까운 분포는 전체 최적점 근처에서 발견될 수 있음을 보이고자 한다. 이러한 전기비저항 분포의 역해석적인 규명을 간단한 2차원 수치해석문제를 풀어보므로서 확인해본다.

### Development of a Back Analysis Program for Rock Tunnel using FLAC (FLAC을 이용한 터널 역해석 프로그램의 개발)

• 양형식;전양수
• Tunnel and Underground Space
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• v.12 no.1
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• pp.37-42
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• 2002
• A back analysis algorithm was developed to determine the major parameters for tunnel design; the elastic modulus(E) and the ratio of horizontal to vertical stress(K). The algorithm is based on direct search method and was coded by FISH language of FLAC, a commercial finite difference program. Developed code was applied on some models to verify the validity and estimate the efficiency of the algorithm. Verification by theoretical solutions and published results of Gens' research, was successful.

### Development of a back analysis program for reasonable derivation of tunnel design parameters (합리적인 터널설계정수 산정을 위한 역해석 프로그램 개발)

• Kim, Young-Joon;Lee, Yong-Joo
• Journal of Korean Tunnelling and Underground Space Association
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• v.15 no.3
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• pp.357-373
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• 2013
• In this paper, a back analysis program for analyzing the behavior of tunnel-ground system and evaluating the material properties and tunnel design parameters was developed. This program was designed to be able to implement the back analysis of underground structure by combination of using FLAC and optimized algorithm as direct method. In particular, Rosenbrock method which is able to do direct search without obtaining differential coefficient was adopted for the back analysis algorithm among optimization methods. This back analysis program was applied to the site to evaluate the design parameters. The back analysis was carried out using field measurement results from 5 sites. In the course of back analysis, nonlinear regression analysis was carried out to identify the optimum function of the measured ground displacement. Exponential function and fractional function were used for the regression analysis and total displacement calculated by optimum function was used as the back analysis input data. As a result, displacement recalculated through the back analysis using measured displacement of the structure showed 4.5% of error factor comparing to the measured data. Hence, the program developed in this study proved to be effectively applicable to tunnel analysis.

### Back Analysis of Field Measurements Around the Tunnel with the Application of Genetic Algorithms (유전자 알고리즘을 이용한 터널 현장 계측 결과의 역해석)

• Kim Sun-Myung;Yoon Ji-Sun;Jun Duk-Chan;Yoon Sang-Gil
• Journal of the Korean Geotechnical Society
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• v.20 no.7
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• pp.69-78
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• 2004
• In this study, the back analysis program was developed by applying the genetic algorithm, one of artificial intelligence fields, to the direct method. The optimization process which has influence on the efficiency of the direct method was modulated with genetic algorithm. On conditions that the displacement computed by forward analysis for a certain rock mass model was the same as the displacement measured at the tunnel section, back analysis was executed to verify the validity of the program. Usefulness of the program was confirmed by comparing relative errors calculated by back analysis, which is carried out under the same rock mass conditions as analysis model of Gens et at (1987), one of back analysis case in the past. We estimated the total displacement occurring by tunnelling with the crown settlement and convergence measured at the working faces in three tunnel sites of Kyungbu Express railway. Those data measured at the working face are used for back analysis as the input data after confidence test. As the results of the back analysis, we comprehended the tendency of tunnel behaviors with comparing the respective deformation characteristics obtained by the measurement at the working face and by back analysis. Also the usefulness and applicability of the back analysis program developed in this study were verified.

### Development of Inversion Analysis Framework to Determine Nonlinear Shear Moduli of Soils In Situ (현장시험을 통해 지반의 비선형 전단탄성계수를 산정하기 위한 역해석방법의 개발)

• Ahn, Jae-Hun
• Journal of the Korean Society of Hazard Mitigation
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• v.8 no.3
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• pp.87-93
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• 2008
• The large scale shaker can be employed to measure linear and nonlinear shear moduli of soils in situ as a function of shear strain. The method involves applying dynamic loads on a surface foundation measuring the dynamic response of the soil mass beneath the foundation with embedded instrumentation. This paper focuses on the development of a framework of the inverse analysis for the interpretation of test data to estimate linear and nonlinear shear moduli of soils along with the necessity of the inverse analysis. The suggested framework is based on the nonlinear least squares but it uses two iterative loops to account for the nonlinear behavior of soil that sensors are not located. The validity of the suggested inversion framework is tested through a series of numerical parametric studies. An example use of the suggested inversion framework is also shown. Because the field condition may affect the accuracy of suggested method, it is important to conduct a preliminary inverse analysis to quantify the discrepancy between the estimated modulus and the baseline.

### On the III-condition of Reverse Process from Structural Dynamic Response Data (구조시스템의 동적응답을 이용한 역해석에서의 악조건 특성 규명)

• 양경택
• Journal of the Computational Structural Engineering Institute of Korea
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• v.12 no.1
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• pp.83-94
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• 1999
• 본 연구에서는 시스템의 해석적 모델과 측정된 응답을 이용하여 입력하중을 추정하는 역해석 기법을 유한요소모델과 같은 해석적 모델을 알고 있는 경우와 주파수응답함수와 같은 실험적 모델을 알고 있는 경우에 대하여 제시하였으며 이때 발생되는 수학적 악조건의 특성을 규명하였다. 역해석시 발생되는 수학적 악조건은 시스템의 동강성행렬과 측정위치에 의해 결정되는 특성행렬의 조건수에 따라 결정되며 역해석기법을 공학문제에 적용하기 위하여는 특성행렬의 조건수가 낮아지도록 주자유도 및 측정점을 선택하여야 하고 특히 공진영역 및 반공진영역에서는 필연적으로 악조건이 발생됨을 알 수 있었다. 수학적 악조건의 특성을 명확히 규명하기 위하여 간단한 수치해석을 통하여 그 결과를 제시하였다.

### Time-domain Elastic Full-waveform Inversion Using One-dimensional Mesh Continuation Scheme (1차원 유한요소망 연속기법을 이용한 시간영역 탄성파의 역해석)

• Kang, Jun Won
• Journal of the Computational Structural Engineering Institute of Korea
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• v.26 no.4
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• pp.213-221
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• 2013
• This paper introduces a mesh continuation scheme for a one-dimensional inverse medium problem to reconstruct the spatial distribution of elastic wave velocities in heterogeneous semi-infinite solid domains. To formulate the inverse problem, perfectly-matched-layers(PMLs) are introduced as wave-absorbing boundaries that surround the finite computational domain truncated from the originally semi-infinite extent. To tackle the inverse problem in the PML-truncated domain, a partial-differential-equations(PDE)-constrained optimization approach is utilized, where a least-squares misfit between calculated and measured surface responses is minimized under the constraint of PML-endowed wave equations. The optimization problem iteratively solves for the unknown wave velocities with their updates calculated by Fletcher-Reeves conjugate gradient algorithms. The optimization is performed using a mesh continuation scheme through which the wave velocity profile is reconstructed in successively denser mesh conditions. Numerical results showed the robust performance of the mesh continuation scheme in reconstructing target wave velocity profile in a layered heterogeneous solid domain.

### DEA optimization for operating tunnel back analysis (운영 중 터널 역해석을 위한 차분진화 알고리즘 최적화)

• An, Joon-Sang;Kim, Byung-Chan;Moon, Hyun-Koo;Song, Ki-Il;Su, Guo-Shao
• Journal of Korean Tunnelling and Underground Space Association
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• v.18 no.2
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• pp.183-193
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• 2016
• Estimation of the stability of an operating tunnel through a back analysis is a difficult concept to analyze. Specially, when a relatively thick lining is constructed as in case of a subsea tunnel, there will be a limit to the use of displacement-based tunnel back analysis because the corresponding displacement is too small. In this study, DEA is adopted for tunnel back analysis and the feasibility of DEA for back analysis is evaluated. It is implemented in the finite difference code FLAC3D using its built-in FISH language. In addition, the stability of a tunnel lining will be evaluated from the development of displacement-based algorithm and its expanded algorithm with conformity of several parameters such as stress measurements.

### Evaluation of Soil Stiffness and Excavation Support Wall Deformation at Deep Excavation Site Using Inverse Analysis (역해석을 이용한 지반 강성 산정 및 굴착 지지벽체의 변형 평가)

• Kim, Taesik;Jung, Young-Hoon
• Journal of the Korean GEO-environmental Society
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• v.21 no.12
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• pp.5-10
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• 2020
• In this study, the evolution of soil engineering property values according to excavation was analyzed through the inverse analysis for the OO deep excavation site located in Incheon. The stiffness of the ground was updated by comparing the horizontal wall deformation of the excavation support wall calculated by the finite element analysis at each stage of excavation and the value measured using an inclinometer. The updated stiffness was used to predict the response of the excavation support wall in the next excavation step. The finite element analysis method using the Hardening Soil model was used, and the stratum where the excavation support wall is located was selected as the stratum for the inverse analysis. The inverse analysis results showed that the stiffness value at the stiffness value at the initial stage of excavation is larger than the stiffness used in the original design. As the excavation proceeds, the stiffness calculated through the second inverse analysis was found to decrease compared to the value derived by the first inverse analysis. Therefore, it can be stated that the deformation of the excavation support wall can be accurately calculated through finite element analysis when an appropriate stiffness value is input according to the excavation stage.