• Title/Summary/Keyword: Load and Resistance Factor Design

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Stress-based topology optimization under buckling constraint using functionally graded materials

  • Minh-Ngoc Nguyen;Dongkyu Lee;Soomi Shin
    • Steel and Composite Structures
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    • v.51 no.2
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    • pp.203-223
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    • 2024
  • This study shows functionally graded material structural topology optimization under buckling constraints. The SIMP (Solid Isotropic Material with Penalization) material model is used and a method of moving asymptotes is also employed to update topology design variables. In this study, the quadrilateral element is applied to compute buckling load factors. Instead of artificial density properties, functionally graded materials are newly assigned to distribute optimal topology materials depending on the buckling load factors in a given design domain. Buckling load factor formulations are derived and confirmed by the resistance of functionally graded material properties. However, buckling constraints for functionally graded material topology optimization have not been dealt with in single material. Therefore, this study aims to find the minimum compliance topology optimization and the buckling load factor in designing the structures under buckling constraints and generate the functionally graded material distribution with asymmetric stiffness properties that minimize the compliance. Numerical examples verify the superiority and reliability of the present method.

Optimal Design of I-type Girders in 2-Span Continuous Steel Bridges by LRFD (LRFD에 의한 연속보 주부재의 조밀 및 비조밀 단면 최적화 설계)

  • Gook, Joong-Sik;Shin, Yung-Seok
    • Journal of Korean Society of Steel Construction
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    • v.12 no.3 s.46
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    • pp.329-337
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    • 2000
  • The Load and Resistance Factor Design(LRFD) Specification defines two sets of limiting width-to-thickness ratios. On the basis of these limiting values, steel sections are subdivided into three categories: compact, noncompact, and slender sections. In this paper, I-Type girders of a 2 span continuous steel bridge are divided into compact and non-compact sections and analyzed. In the design process, an optimization formulation was adopted and ADS, a Fortran program for Automated Design Synthesis, was used. In this study, we studied about change of the section between compact and non-compact using optimization formulation.

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Durability Evaluation of RC Structures subjected. to Chloride Attack (철근콘크리트 구조물의 염해 내구성 평가)

  • 백승우;남진원;송하원;변근주
    • Proceedings of the Korea Concrete Institute Conference
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    • 2003.05a
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    • pp.663-668
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    • 2003
  • In this paper, an environmental factor and a durability resistance factor which adapts the concept of the Load Resistance Factor Design for safety design of RC structures is derived and a basic principle of a durability evaluation for RC structures using the factors is proposed. It is shown that durability of RC structures can be evaluated by comparing predicted value of chloride ion concentration with limit value of concentration for steel corrosion generation in reinforcement steel position and the durability of concrete manufactured for the RC structures can be also evaluated by comparing characteristic diffusion coefficient of concrete with predicted diffusion coefficient during mixture design.

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Reliability-Based Structural Integrity Assessment of Wall-Thinned Pipes Using Partial Safety Factor (부분안전계수를 이용한 감육배관의 신뢰도 기반 건전성 평가)

  • Lee, Jae-Bin;Huh, Nam-Su;Park, Chi-Yong
    • Journal of the Korean Society of Manufacturing Technology Engineers
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    • v.22 no.3_1spc
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    • pp.518-524
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    • 2013
  • Recently, probabilistic assessments of nuclear power plant components have generated interest in the nuclear industries, either for the efficient inspection and maintenance of older nuclear plants or for improving the safety and cost-effective design of newly constructed nuclear plants. In the present paper, the partial safety factor (PSF) of wall-thinned nuclear piping is evaluated based on a reliability index method, from which the effect of each statistical variable (assessment parameter) on a certain target probability is evaluated. In order to calculate the PSF of a wall-thinned pipe, a limit state function based on the load and resistance factor design (LRFD) concept is first constructed. As for the reliability assessment method, both the advanced first-order second moment (AFOSM) method and second-order reliability method (SORM) are employed to determine the PSF of each probabilistic variable. The present results can be used for developing maintenance strategies considering the priorities of input variables for structural integrity assessments of wall-thinned piping, and this PSF concept can also be applied to the optimal design of the components of newly constructed plants considering the target reliability levels.

Evaluation of Response Modification Factors for Shear Wall Apartment Building (벽식 APT의 반응수정계수 추정에 관한 연구)

  • 송정원;송진규;이수곤
    • Proceedings of the Korea Concrete Institute Conference
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    • 2001.05a
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    • pp.859-864
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    • 2001
  • For earthquake resistance design, a response modification factor is used to reduce the design strength and it reflects ductility, reserve strength, redundancy and damping effect. But this factor has not theoretical basis. In this study, two response modification factors are compared and analyzed for shear wall apartment building.; the one is introduced by ATC-19 Procedures, the other is suggested FEMA-273 and ATC-40 through nonlinear static analysis. For the results, ATC-19 procedure gives a reasonable estimation to R factor. But $R_{u}$ by using FEAM-273 and ATC-40 methods is estimated so small in case of a minor or moderate earthquake region. Due to this fact, response modification factor is smaller than suggested load criterion 3.0. So, it needs to decrease wall volume and reduce the global strength and system stiffness for proper ductile behavior matching to domestic load criterion.

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Observer Based Estimation of Driving Resistance Load for Vehicle Longitudinal Motion Control

  • Kim, Duk-Ho;Shin, Byung-Kwan;Kyongsu Yi;Lee, Kyo-Il
    • 제어로봇시스템학회:학술대회논문집
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    • 1999.10a
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    • pp.185-188
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    • 1999
  • An estimation algorithm for vehicle driving load has been proposed in this paper. Driving load is an important factor in a vehicle's longitudinal motion control. An approach using an observer is introduced to estimate driving load based on inexpensive RPM sensors currently being used in production vehicles. Also, a torque estimation technique using nonlinear characteristic functions has been incorporated in this estimation algorithm. Using a nonlinear full vehicle simulation model, we study the effect of the driving load on longitudinal vehicle motion, and the performance of the estimation algorithm has been evaluated. The proposed estimation algorithm has good performance and robustness over uncertainties in the system parameters. An accurate estimate of the driving load can be very helpful in the development of advance vehicle control systems such as intelligent cruise control systems, CW/CA systems and smooth shift control systems.

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Constructing Database and Probabilistic Analysis for Ultimate Bearing Capacity of Aggregate Pier (쇄석다짐말뚝의 극한지지력 데이터베이스 구축 및 통계학적 분석)

  • Park, Joon-Mo;Kim, Bum-Joo;Jang, Yeon-Soo
    • Journal of the Korean Geotechnical Society
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    • v.30 no.8
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    • pp.25-37
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    • 2014
  • In load and resistance factor design (LRFD) method, resistance factors are typically calibrated using resistance bias factors obtained from either only the data within ${\pm}2{\sigma}$ or the data except the tail values of an assumed probability distribution to increase the reliability of the database. However, the data selection approach has a shortcoming that any low-quality data inadvertently included in the database may not be removed. In this study, a data quality evaluation method, developed based on the quality of static load test results, the engineering characteristics of in-situ soil, and the dimension of aggregate piers, is proposed for use in constructing database. For the evaluation of the method, a total 65 static load test results collected from various literatures, including static load test reports, were analyzed. Depending on the quality of the database, the comparison between bias factors, coefficients of variation, and resistance factors showed that uncertainty in estimating bias factors can be reduced by using the proposed data quality evaluation method when constructing database.

Evaluation of the Resistance Bias Factors to Develop LRFD for Driven Steel Pipe Piles (LRFD 설계를 위한 항타강관말뚝의 저항편향계수 산정)

  • Kwak, Kiseok;Park, Jaehyun;Choi, Yongkyu;Huh, Jungwon
    • KSCE Journal of Civil and Environmental Engineering Research
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    • v.26 no.5C
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    • pp.343-350
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    • 2006
  • The resistance bias factors for driven steel pipe piles are evaluated as a part of study to develop the LRFD(Load and Resistance Factor Design) for foundation structures in Korea. The 43 data sets of static load tests and soil property tests performed in the whole domestic area were collected and analyzed to determine the representative bearing capacities of the piles using various methods. Based on the statistical analysis of the data, the Davisson's criterion is proved to be the most reasonable method for estimation of pile bearing capacity among the methods used. The static bearing capacity formulas and the Meyerhof method using N values are applied to calculate the design bearing capacity of the piles. The resistance bias factors of the driven steel pipe piles are evaluated respectively as 0.98 and 1.46 by comparison of the bearing capacities for both of the static bearing capacity formulas and the Meyerhof method. It is also shown that uncertainty of the static bearing capacity formulas is relatively less than that of the Meyerhof method.

On the member reliability of wind force-resisting steel frames designed by EN and ASCE rules of load combinations

  • Kudzys, Antanas;Kudzys, Algirdas
    • Wind and Structures
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    • v.12 no.5
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    • pp.425-439
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    • 2009
  • The expediency of revising universal rules for the combination of gravity and lateral actions of wind force-resisting steel structures recommended by the Standards EN 1990 and ASCE/SEI 7-05 is discussed. Extreme wind forces, gravity actions and their combinations for the limit state design of structures are considered. The effect of statistical uncertainties of extreme wind pressure and steel yield strength on the structural safety of beam-column joints of wind force-resisting multistory steel frames designed by the partial factor design (PFD) and the load and resistance factor design (LRFD) methods is demonstrated. The limit state criterion and the performance process of steel frame joints are presented and considered. Their long-term survival probability analysis is based on the unsophisticated method of transformed conditional probabilities. A numerical example illustrates some discrepancies in international design standards and the necessity to revise the rule of universal combinations of loads in wind and structural engineering.

Optimum Design Criteria of Steel Structure members based on ETCM (ETCM에 의한 강구조부재의 최적설계규준)

  • 이증빈;박주원
    • Proceedings of the Computational Structural Engineering Institute Conference
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    • 1996.10a
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    • pp.277-287
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    • 1996
  • Based on the developments of the reliability-based steel structural analysis and design as well as the extending knowledgy on the probabilitic characteristics of loading and resistance the probability based design criteria have been successful Iy developed for many students. The existing design codes, which are genarally based on the structural theory and certain engineering experience, do not realistically consider the uncertainties of loads and resistance and the basic reliability concepts. It is recognized to develope the design criteria by ETCM(Expected Total cost Minimization). In this study, therefore, the proper probability based design criteria (Optimum load and resistance factor design formats ) has been developed based on the safety levels observed from calibration Iii th existing standards, which applies to the ultimate limit states of steel structural members.

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