• Title/Summary/Keyword: Back Analysis

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Application of New Back Analysis Method for Landslide around Portal (터널 갱구부 주변의 산사태를 고려한 역해석법에 관한 검토)

    • Tunnel and Underground Space
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    • v.8 no.1
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    • pp.46-52
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    • 1998
  • The author conducted new back analysis method using monitoring data to a landslide which occurred around portal. In this case, because the tunnel being located under the sliding plane of the landslide, calculated value from the ordinary back analysis in which considered only stress release by the tunnel excavation didn't fit the measured value. Then, in the new method, a body force as the movement of the landslide mass was added to the ordinary back analysis and good results were obtained. Furthermore, the author carried out stability analysis of the landslide with the data of the back analysis and examined the loosened area and decreasing og the sliding plane strength due to the tunnel excavation.

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Back Analysis of Earth Retaining Wall Using Increment of Sequential Displacement (변위증분을 이용한 흙막이 벽의 역해석에 관한 연구)

  • 장범수;이승훈;김종민;김수일
    • Journal of the Korean Geotechnical Society
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    • v.19 no.5
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    • pp.7-14
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    • 2003
  • In the back analysis of braced excavation based on displacement measurements, the accumulated errors of abnormal displacement caused by unexpected loads are usually observed. To minimize such errors, in this study, displacement increment was used fur back analysis rather than displacement for the conventional method. That is, the increment of sequential displacement is used as the objective function and the back analysis program is developed by taking advantage of sequential linear programming method by modified method of feasible directions. Based on small scale model test, the analysis of proposed method is verified.

Optimal Design of Automotive Seat Back Frame Using Finite Element Analysis (유한요소해석을 이용한 차량용 시트 백 프레임의 최적설계)

  • Shin, Hyeonho;Kang, Hee Yong;Yang, Sung Mo
    • Journal of Auto-vehicle Safety Association
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    • v.11 no.4
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    • pp.57-62
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    • 2019
  • The seat back frame of the vehicle is subjected to load on the passenger behavior. Because of steel material, it is necessary to optimize the frame considering lightweight and safety. In this paper, finite element analysis is used for the optimal design of the seat back frame. First, a lightweight material is applied to reduce the weight of the seat back frame. Secondly, the design position of the pipe part fastened in the seat back frame was selected by considering the strength against the load generated by the occupant. Third, the shape of the side frame was derived by performing the phase optimization analysis for the AFT load condition. And we have compared the initial model with the optimal model to verify the light weighting and safety. As a result, the optimal design model of the seat back frame satisfying the weight reduction and safety has been proposed.

Numerical and Experimental Study on Spring Back in Automatic Multi-Stage Precision Cold Forging Process of a Steering Yoke (조향장치용 요크 자동다단 정밀냉간단조 공정에서 발생하는 스프링백의 수치적 및 실험적 검증)

  • Kim, K.M.;Kim, M.C.;Hwang, T.M.;Chung, S.H.;Chung, W.J.;Joun, M.S.
    • Transactions of Materials Processing
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    • v.28 no.3
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    • pp.115-122
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    • 2019
  • In this paper, finite element analysis of an automatic five-stage precision cold forging process of a yoke, a steering part of a passenger's car, is conducted with emphasis on spring back analysis at the yoke-forming stage and its experimental verification is subsequently made. An elastoplastic finite element method with MINI-element technique employed for the analysis of the entire process is explained. There is emphasis that the thin film of material formed between the punch and die in the stage may result to some errors especially in elastoplastic finite element analysis of spring back due to frequent remeshing. The numerical robustness of the spring back analysis in regards to remeshing is hence shown first through investigation into its effect on the predicted spring back. Experimental measurement of displacement due to spring back is carried out for comparison with the predicted results, and they are in a qualitative agreement with each other.

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.

Effectiveness of Electroacupuncture for Patients with Failed Back Surgery Syndrome: A Systematic Review and Meta-analysis

  • Shin, Donghoon;Shin, Kyungmoon;Jeong, Hwejoon;Kang, Deok;Yang, Jaewoo;Oh, Jihoon;Lim, Jinwoong
    • Journal of Acupuncture Research
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    • v.39 no.3
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    • pp.159-169
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    • 2022
  • Failed back surgery syndrome (FBSS) is a term that applies to symptoms such as persistent or recurring low back pain, paresthesia, sciatica, or numbness after spine surgery. Electroacupuncture (EA) has been reported to have excellent analgesic effects although there have been no systematic reviews on the effects of EA on FBSS. Therefore, a systematic review and meta-analysis of the effectiveness of EA on FBSS was conducted. Eight databases were searched for studies that used EA for FBSS and 7 randomized controlled trials (RCTs) were included. RCTs of EA as combination therapy for FBSS compared with conventional treatment demonstrated improvement in the level of pain, lumbar functional scale scores, and quality of life. However, meta-analysis showed that reduction in pain was not statistically significant, while evaluation of lumbar function significantly improved, although the quality of evidence in the RCTs was generally low. RCTs comparing EA alone with conventional treatment demonstrated an improved level of pain, lumbar function, and effective rate of treatment. Meta-analysis showed that pain was significantly decreased in the EA alone group compared with the control group, although the quality of evidence was low. To improve the quality of evidence, high-quality RCTs are required in the future.

Pain Patterns and Factors Affecting of Low Back Pain in Middle-aged Women (중년여성이 경험하는 만성요통의 통증양상 및 영향요인)

  • Ham, Young-Lim;Seo, Bok-Nam;Ahn, Yang-Heui
    • Journal of muscle and joint health
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    • v.14 no.1
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    • pp.33-41
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    • 2007
  • Purpose: The purpose of the study was to identify the pain patterns and factors affecting low back pain in middle-aged women with backache. Method: A descriptive research design was utilized. The participants were middle-aged women who visited to two back pain clinics in Wonju from October, 2006 through February, 2007. A total of 195 low back pain patients agreed to participate in this study, and data from 177 were analyzed. Data were collected using a questionnaire which included a modified short-form Korean pain rating scale, demographic factors, factors related to low back pain and health behavior. Descriptive statistics and multiple regression analysis was utilized in the analysis. Results: The mean score for low back pain was relatively low(M=21.57, SD=11.44). Among pain patterns, scores for dull pain were the highest of all the dimensions. In the regression analysis, significant factors affecting low back pain were found to be age, level of education, religion, BMI, experience of pregnancy, delivery type and exercise. These variables explained 24.8% of variance in low back pain(F=3.79, p<.001). Conclusion: These results suggest that nurses need for assessment and intervention to take into consideration pain patterns as well as factors affecting middle-age women with backache.

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A Study on Back EMF of BLDC Motor Using Numetical Analysis Method (수치해석 방법을적용한 BLDC 전동기의 역기전력 연구)

  • Kim, Hyun-Cheol
    • Journal of the Korean Society of Safety
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    • v.23 no.4
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    • pp.36-41
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    • 2008
  • This report describes the analytical solution of back EMF for BLDC motor using numerical analysis of air gap flux density. The analysis of air gap flux density is the key to expect the performance of back EMF for the design of brushless motor. The numerical analysis and FEM analysis are performed to vary attachment of stator side or rotor side, radial flux magnetization or parallel flux magnetization, magnet arc angle in the condition of constant air gap. This results have more reliable data comparing with test result of the back EMF for 7 phase BLDC motor.

Estimation of Tension Forces of Assembly Stay Cables Connected with Massive Anchorage Block (중량 앵커리지 블록과 연결된 조립 스테이 케이블의 장력 추정)

  • Jeong, Woon;Kim, Nam-Sik
    • Transactions of the Korean Society for Noise and Vibration Engineering
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    • v.15 no.3 s.96
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    • pp.346-353
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    • 2005
  • In this paper, the tension of assembly stay cable connected with massive anchorage block was calculated through back analysis of in-situ frequencies measured from a stadium structure. Direct approach to back analysis is adopted using the univariate method among the direct search methods as an optimization technique. The univariate method can search the optimal tension without regard to the initial ones and has a rapid convergence rate. To verify the reliability of back analysis, Tension formulas proposed by Zui et al. and Shimada were used. Tensions estimated by three methods are compared with the design tension, and are in a reasonable agreement with an error of more or less than 15%. Therefore, it is shown that back analysis applied in this paper is appropriate for estimation of cable tension force.

A Study on the Behavior Prediction of Underground Structures by Back Analysis (역해석에 의한 지하구조체의 거동예측에 관한 연구)

  • 장정범;김문겸
    • Tunnel and Underground Space
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    • v.8 no.2
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    • pp.139-145
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    • 1998
  • The reliable estimation of the system parameters and the accurate prediction of the system behavior are important to design underground structures safely and economically. Especially, the elastic modulus and the in-situ stresses are very important parameters in predicting the behavior of the underground structure. Therefore, the back analysis using the field measurement data is developed to determine accurately the elastic modulus and the in-situ stresses of the underground structural system in this study. A back analysis using the combined finite and boundary element is developed. It can consider the far field boundary condition and is efficient in computation. In this study, a back analysis is performed to predict behaviors of underground structures for the real construction site. The comparison between the results of the back analysis with field measurement data and the obtained material properties from the field test shows good agreement for the real construction site.

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