• Title/Summary/Keyword: 응답보정계수

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Sample size using response rate on repeated surveys (계속조사에서 응답률을 반영한 표본크기)

  • Park, Hyeonah;Na, Seongryong
    • The Korean Journal of Applied Statistics
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    • v.31 no.5
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    • pp.587-597
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    • 2018
  • Procedures, such as sampling technique, survey method, and questionnaire preparation, are required in order to obtain sample data in accordance with the purpose of a survey. An important procedure is the decision of the sample size formula. The sample size formula is determined by setting the target error and total cost according to the sampling method. In this paper, we propose a sample size formula using population changes over time, estimation error of the previous time and response rate of past data when the target error and the expected response rate are given in the simple random sampling. In actual research, we use estimators that apply complex weights in addition to design-based weights. Therefore, we induce a sample size formula for estimators using design-based weights and nonresponse adjustment coefficients, that can be a formula that reflects differences in response rates when survey methods are changed over time. In addition, we use simulations to compare the proposed formula with the existing sample size formula.

Conservativeness of Response Displacement Method used in Seismic Response Analysis of Power Cable Tunnels (전력구의 지진응답해석법에 사용되는 응답변위법의 보수성 평가)

  • Lim, Jae-Sung;Yang, Dae-Seung;Hwang, Kyeong-Min;Kim, Jae-Min
    • Journal of the Computational Structural Engineering Institute of Korea
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    • v.34 no.4
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    • pp.243-254
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    • 2021
  • In this study, the conservatism of the response displacement method (RDM) for the seismic response analysis of box-shaped power cable tunnels was evaluated. A total of 50 examples were used considering the cross-sections of 25 power cable tunnels and two soil conditions for each power cable tunnel. The following three methods were applied for the analysis by the RDM: (1) single cosine method, (2) double cosine method, and (3) dynamic free-field analysis method. A refined dynamic analysis method considering soil-structure interaction (SSI) was employed to compare the conservatism of the RDM. The double cosine method demonstrated the most conservative result, while the dynamic free-field analysis method yielded the least deviation. The soil stiffness reduction factor, C, for the double cosine method was recommended to be 0.9 and 0.7 for the operational performance and collapse prevention levels, respectively, to ensure a probability of at least 80% that the member force by the RDM is larger than that of dynamic SSI analysis.

A Study on the Improvement of FEM model in Plate Vibration by Modification of Young's Modulus and Shape (FEM 모델의 형상과 감쇠계수의 추정을 통한 평판진동해석의 개선에 대한 연구)

  • Park, Sok-Chu;Oh, Chang-Guen
    • Journal of Advanced Marine Engineering and Technology
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    • v.36 no.6
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    • pp.794-801
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    • 2012
  • Finite Element Method is a strong tool to analyse static and dynamic problem of a structure. FEM is a good method for static problem, but for dynamic problem there are some differences between real phenomena and analyzed phenomena. Therefore some modifications are needed to identify two results. In this paper authors propose a genetic algorithm method 1) to adjust dimensions of plate for identifying natural frequencies, 2) to fit amplitude of FEM Frequency Response Function(FRF) onto it of real FRF. Analysis by raw FEM data gave questions if the results were for the same object. By only adjusting Young's modulus much better accordances were obtained, but limitation existed still. Very good agreements were achieved by shape modification and damping coefficient identification.

Analysis on Application of Limit State Design Method for Bridge Evaluation Considering PSC Beam Bridge Experiment Results (PSC Beam교의 실측실험을 반영한 한계상태설계법 기반 교량 평가법 적용 분석)

  • Kim, Kyunghyun;Yoo, Minsun;Paik, Inyeol;Shin, Soobong
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.25 no.6
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    • pp.235-244
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    • 2021
  • This study analyzes the applicability of limit state design method on bridge evaluation by considering the experiment of the existing bridge. The test strength of the member is obtained from the PSC beam bridge experiment. The test strength is compared with the calculated strength obtained from the statistical characteristics of material test strength and the two values are almost the same. The response modification factor and dynamic impact factor are obtained from the vehicle loading test. The rating factor is calculated by applying limit state design method as well as current evaluation method and the results are compared. The reliability index of the test bridge is calculated by using the statistical properties of the member strength obtained from material test and simulation. When the statistical properties of the PSC beam tested in this study are applied, the reliability index with a larger value was obtained than the reliability index obtained with the statistical properties of the design code.

Evaluation of the Influence of Shear Strength Correction through a Comparative Study of Nonlinear Site Response Models (비선형 지반구성모델의 비교를 통한 전단강도 보정이 부지응답해석에 미치는 영향 평가)

  • Aaqib, Muhammad;Park, Duhee;Kim, Hansup;Adeel, Muhammad Bilal;Nizamani, Zubair Ahmed
    • Journal of the Korean Geotechnical Society
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    • v.36 no.12
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    • pp.77-86
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    • 2020
  • In this study, the importance of implied strength correction for shallow depths at a region of moderate to low seismicity with primary focus on its effect upon site natural period and mean period of the ground motion is investigated. In addition to the most commonly used Modified Kondner-Zelasko (MKZ) model, this paper uses a quadratic/hyperbolic (GQ/H) model that can capture the stress - strain response at large strains as well as small strain stiffness dependence. A total of six site profiles by downhole tests are used and 1D site response analyses are performed using three input motions with contrasting mean periods. The difference between non-corrected and corrected analyses is conditional on the site period as well as mean ground motion period. The effect of periods is analyzed by correlating them with the effective peak ground acceleration, maximum shear strains and amplification factors. The comparative study reveals that the difference is more prominent in soft sites with long site periods. Insignificant differences are observed when soil profiles are subjected to ground motion with very short mean period.

On the Errors of the Phased Beam Tracing Method for the Room Acoustic Analysis (실내음향 해석을 위한 위상 빔 추적법의 사용시 오차에 관하여)

  • Jeong, Cheol-Ho;Ih, Jeong-Guon
    • The Journal of the Acoustical Society of Korea
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    • v.27 no.1
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    • pp.1-11
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    • 2008
  • To overcome the mid frequency limitation of geometrical acoustic techniques, the phased geometrical method was suggested by introducing the phase information into the sound propagation from the source. By virtue of phase information, the phased tracing method has a definite benefit in taking the interference phenomenon at mid frequencies into account. Still, this analysis technique has suffered from difficulties in dealing with low frequency phenomena, so called, wave nature of sound. At low frequencies, diffraction at corners, edges, and obstacles can cause errors in simulating the transfer function and the impulse response. Due to the use of real valued absorption coefficient, simulated results have shown a discrepancy with measured data. Thus, incorrect phase of the reflection characteristic of a wall should be corrected. In this work, the uniform theory of diffraction was integrated into the phased beam tracing method (PBTM) and the result was compared to the ordinary PBTM. By changing the phase of the reflection coefficient, effects of phase information were investigated. Incorporating such error compensation methods, the acoustic prediction by PBTM can be further extended to low frequency range with improved accuracy in the room acoustic field.

Behavior of Truss Railway Bridge Using Periodic Static and Dynamic Load Tests (주행 열차의 정적 및 동적 재하시험 계측 데이터를 이용한 트러스 철도 교량의 주기적 거동 분석)

  • Jin-Mo Kim;Geonwoo Kim;Si-Hyeong Kim;Dohyeong Kim;Dookie Kim
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.27 no.6
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    • pp.120-129
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    • 2023
  • To evaluate the vertical loads on railway bridges, conventional load tests are typically conducted. However, these tests often entail significant costs and procedural challenges. Railway conditions involve nearly identical load profiles due to standardized rail systems, which may appear straightforward in terms of load conditions. Nevertheless, this study aims to validate load tests conducted under operational train conditions by comparing the results with those obtained from conventional load tests. Additionally, static and dynamic structural behaviors are extracted from the measurement data for evaluation. To ensure the reliability of load testing, this research demonstrates feasibility through comparisons of existing measurement data with sensor attachment locations, train speeds, responses between different rail lines, tendency analysis, selection of impact coefficients, and analysis of natural frequencies. This study applies to the Dongho Railway Bridge and verifies the applicability of the proposed method. Ten operational trains and 44 sensors were deployed on the bridge to measure deformations and deflections during load test intervals, which were then compared with theoretical values. The analysis results indicate good symmetry and overlap of loads, as well as a favorable comparison between static and dynamic load test results. The maximum measured impact coefficient (0.092) was found to be lower than the theoretical impact coefficient (0.327), and the impact influence from live loads was deemed acceptable. The measured natural frequencies approximated the theoretical values, with an average of 2.393Hz compared to the calculated value of 2.415Hz. Based on these results, this paper demonstrates that for evaluating vertical loads, it is possible to measure deformations and deflections of truss railway bridges through load tests under operational train conditions without traffic control, enabling the calculation of response factors for stress adjustments.

A Study on the Correction Factors of Soil Non-linearity Considering Korean Regional Conditions for Seismic Deformation Method Applied to Multi-Utility Tunnels (공동구의 응답변위법 해석 시 국내 특성을 반영한 지반 비선형 보정계수 연구)

  • Choi, Jeong Ho;Yun, Jong Seok;Choo, Yun Wook;Youn, Jun Ung
    • Journal of the Earthquake Engineering Society of Korea
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    • v.25 no.1
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    • pp.11-20
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    • 2021
  • The seismic deformation method is conventionally used as a seismic design for a multi-utility tunnel in Korea. In the seismic deformation method, the soil ground's natural period is one of the most critical factors for calculating the ground displacement using cosine functions. Correction factors for the natural period and shear wave velocity have been used to consider the non-linearity of dynamic soil properties. However, the correction factors have been issued because the correction factors have not been sufficiently studied to consider Korea's regional conditions. This paper aims to evaluate the natural periods for the seismic deformation method considering Korea's ground conditions. Ground response analysis was performed using seven real earthquake records on twelve sites with different soil conditions where actual multi-utility tunnels are installed. As a result, natural periods of the sites were analyzed and new correction factors were proposed according to seismic performance and Korea's regional conditions.

Undamped Forced Vibration Response of Curved Composite Panels using Enhanced Assumed Strain Finite Element-Direct Integration Method (추가변형률 유한요소-직접적분법을 이용한 복합적층 곡선패널의 비감쇠 강제진동응답)

  • Park, Won-Tae;Chun, Kyoung-Sik;Son, Byung-Jik
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.8 no.2
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    • pp.247-258
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    • 2004
  • The composite shell element is developed for the solution of undamped forced vibration problem of composite curved panels. The finite element used in the current study is an 4-node enhanced assumed shell element with six degrees of freedom per node. The composite shell element is free of both shear and membrane locking phenomenon by using the enhanced assumed strain(EAS) method. A modification to the first-order shear deformation shell theory is proposed, which results in parabolic thorough-thickness distribution of the transverse shear strains and stresses. It eliminates the need for shear correction factors in the first order theory. Newmark's direct integration technique is used for carrying out the integration of the equation motion, to obtain the repones history. Parametric studies of curved composite panels are carried out for forced vibration analysis by geometrical shapes and by laminated composite; such as fiber orientation, stacking sequence.

A Feasibility Study of Loading Test for Safety Assessment : Concrete Bridges (재하시험 수행에 관한 적정성 연구 : 콘크리트 교량)

  • Hwang, Jin Ha;An, Seoung Su;Kim, Ju Han
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.15 no.6
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    • pp.147-155
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    • 2011
  • The bridges where serious damages, defects, material degradations, etc. are not found can be presumed to have enough safety for the specified design loads, nevertheless, in many cases the loading carrying capacity is rated through loading tests. The safety specifications and manuals get no further than qualitative instructions for performing loading test or not. Some studies presented the improved appraisal methods for determining the load carrying capacity; however, the feasibility studies for loading test are scarcely carried out. This study examines an existing question, whether the loading tests are necessarily required in the safety assessment or not, and suggests an alternative for that via a statistical analysis for dozens of condition evaluation reports for concrete bridges.