• Title/Summary/Keyword: LRFD

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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.

Effect of Car-Crash at Edge Beam of U-Channel Bridge based on Korean Highway Bridge Specifications and AASHTO LRFD Bridge Design Specifications (도로교 설계기준 및 AASHTO LRFD 설계기준에 근거한 U-채널 교량측보의 차량충돌의 영향)

  • Choi, Dong-Ho;Na, Ho-Sung;Lee, Kwang-Won
    • Proceedings of the Computational Structural Engineering Institute Conference
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    • 2008.04a
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    • pp.490-494
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    • 2008
  • U-Channel Bridge is effective bridge type, because its edge beam performs role of barrier and enables to reduce additional dead loads. Although it is effective to reduce additional dead loads, there is possibility of bridge collapse under impact load due to car crash. Also, edge beam must have ability to induce safe driving and prevent falling accidents. Therefore, it requires behavior analysis and property investigation through the vehicle impact crashing edge beam. This study presents method of structural analysis of U-channel bridge and investigates design specifications for the effect of the edge beam under the vehicle impact. Also, it carries out stability investigation of behavior of edge beam and slab, based on Korean Highway Bridge Design Specifications and AASHTO LRFD Bridge Design Specification.

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The Optimum Design of Reinforced Concrete Structures Based on the LRFD (하중일- 저항계수 설계법에 의한 철근콘크리트 구조물 최적설계)

  • 구봉근;강종수;김우식;김태봉
    • Magazine of the Korea Concrete Institute
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    • v.2 no.2
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    • pp.63-72
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    • 1990
  • In this study, an optimization design of reinforced concrete structures is performed by using the structural optimization techniques based on the LRFD criteria. The target reliability index is estimated by the optimal reliability index considering the expected cost which is taken as a sum of the structural cost and the expected costs due to failure of the structure. The load and resistance factors calculated by using level I reliability theory with the target reliability index are compared for each load combination (D+L, D+L+w). The results of this study show that the resistance factors are ${\phi}_{M}$=0.90, ${\phi}_{V}$==0.70, ${\phi}_{C}$==0.65 and the load factors are 1.20D + 1.70L, 1.07L + 0.07L + 1.10W. The optimization techinques used to this study are S.L.P. The optimization design based on the LRFD criteria is more economical and rational than other criteria.

The Concepts and the Applications of Load and Resistance Factor Design and Partial Safety Factor Based on the Reliability Engineering (신뢰성공학에 근거한 하중-강도계수 설계법과 부분안전계수의 개념 및 적용)

  • Yoo, Yeon-Sik;Kim, Tae-Wan;Kim, Jong-In
    • Proceedings of the KSME Conference
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    • 2007.05a
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    • pp.309-314
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    • 2007
  • Recently, the LRFD and the PSF based on structural reliability assessment have been applied to NPP designs in behalf of the conventional deterministic design methods. In the risk-informed structural integrity, it is especially possible to optimize design procedures considering cost, manufacturing and maintenance because the structural reliability concepts have confirmed the reliability for which a designer aims. Generally, in order to evaluate the PSF, the LRFD which is the design concept for evaluating safety factors respectively on the limit state function including load and resistance. This study certifies the concept and its applications of the PSF using the LRFD based on the structural reliability engineering.

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Optimal Design of I-type Girder in 2 Span Continuous Steel Bridges by LRFD (LRFD에 의한 2경간 연속 강교량 주부재의 최적화 설계)

  • 국중식;신영석
    • Proceedings of the Computational Structural Engineering Institute Conference
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    • 1999.04a
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    • pp.78-85
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    • 1999
  • In this study, I-type girders used as main members of a two span continuous steel bridge, are optimally designed by a Load and Resistance Factor Design method(LRFD) using an numerical optimization method. The width, height web thickness and flange thickness of the main girder are set as design variables, and light weight design is attempted by choosing the cross-sectional area as an object function. The main program is coded with C++ and connected with optimization modul ADS, which is coded with FORTRAN. The results of the program show that the stress constraints of noncomposite section during the initial construction stage become active in the positive moment area and the service limit state constaints become active in the negative moment area.

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An Experimental Study on the Axial Stiffness of the Concrete Filled Circular Steel Tube Columns (콘크리트충전 원형강관 기둥의 축강성에 관한 실험연구)

  • Kim, Jeong-Hoi;Song, Hyung-Soo;Park, Jin-Soo;Min, Chang-Shik
    • Proceedings of the Korea Concrete Institute Conference
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    • 2006.05a
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    • pp.422-425
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    • 2006
  • AISC-LRFD, ACI 318 and Korean design specifications for concrete filled circular steel tube columns do not consider the increasing of axial stiffness such as the elastic modulus and the yield strength due to the confinement effect. AISC-LRFD and ACI 318, however, shows different basic philosophy and equations for computing the elastic modulus and the strength of CFT columns. Through this experimental study, 9 circular CFT column specimens were made by varying thickness steel tube and concrete strength, the axial stiffness were compared. The comparison between the design specifications and the test results shows different values on the elastic modulus and yield strength of the CFT columns. Even though, yield strength of the CFT columns are very similar between AISC-LRFD and Korean design specifications.

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Economic Evaluation Method by Design Method ASD and LRFD of Aluminum Curtain wall (알루미늄 커튼월의 ASD/LRFD설계방법에 따른 경제성 평가 방법)

  • Moon, Sang-Deok;Ock, Jong-Ho
    • Proceedings of the Korean Institute of Building Construction Conference
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    • 2014.05a
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    • pp.16-17
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    • 2014
  • The curtain wall construction applied on high-rise building facades in Korea became generalized, but specialty of the CMr(Construction Manager) who needs to perform economical project management with specialty in the curtain wall construction is still lacking. Therefore, this study analyzed the structure design standard of the curtain wall, researched economical design alternatives. Based on the research results, if the ratio of dead load against wind load is less than 0.1256, LRFD will be more economical.

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Minimum-weight design of non-linear steel frames using combinatorial optimization algorithms

  • Hayalioglu, M.S.;Degertekin, S.O.
    • Steel and Composite Structures
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    • v.7 no.3
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    • pp.201-217
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    • 2007
  • Two combinatorial optimization algorithms, tabu search and simulated annealing, are presented for the minimum-weight design of geometrically non-linear steel plane frames. The design algorithms obtain minimum weight frames by selecting suitable sections from a standard set of steel sections such as American Institute of Steel Construction (AISC) wide-flange (W) shapes. Stress constraints of AISC Load and Resistance Factor Design (LRFD) specification, maximum and interstorey drift constraints and size constraints for columns were imposed on frames. The stress constraints of AISC Allowable Stress Design (ASD) were also mounted in the two algorithms. The comparisons between AISC-LRFD and AISC-ASD specifications were also made while tabu search and simulated annealing were used separately. The algorithms were applied to the optimum design of three frame structures. The designs obtained using tabu search were compared to those where simulated annealing was considered. The comparisons showed that the tabu search algorithm yielded better designs with AISC-LRFD code specification.

Development of Live Load Moment Equations Using Orthotropic Plate Theory (직교 이방성 판 이론을 이용한 바닥판 활하중 모멘트 산정식 개발)

  • Ahn Ye-Jun;Nam Suk-Hyun;Park Jang-Ho;Shin Yung-Seok
    • Proceedings of the Computational Structural Engineering Institute Conference
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    • 2006.04a
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    • pp.749-756
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    • 2006
  • Because of the orthotropic elastic properties and significant two-way bending action, orthotropic plate theory may be suitable for describing the behavior of concrete filled grid bridge decks. Current AASHTO LRFD Bridge Design Specification(2004) has live load moment equations considering flexural rigidity ratio between longitudinal and transverse direction, but the Korea highway bridge design specification(2005) doesn't. The Korea highway bridge standard specification LRFD(1996) considers an orthotropic plate model with a single load to estimate live load moments in concrete filled grid bridge decks, which may not be conservative. This paper presents live load moment equations for truck and passenger car, based on orthotropic plate theory. The equations of truck model use multiple presence factor, impact factor, design truck and design tandem of the Korea highway bridge standard specification LRFD(1996). The estimated moments are verified through finite-element analyses.

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Comparative Study of Design Methods for Manufacturing of Steel Structure (철구조물의 설계방법에 대한 비교 연구)

  • Kim, Dong-Kwon;Choi, Jae-Seung;Hwang, Suk-Hwan
    • Proceedings of the KSME Conference
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    • 2000.11a
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    • pp.357-362
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    • 2000
  • Allowable stress design(ASD) method has been widely used to design steel structures such as boiler and heat recovery steam generator(HRSG) of power plant. However, many researchers are recently intrested in road and resistance factor design(LRFD) method which may take the place of ASD. In this work, the weight calculation of steel structure was compared when ASD and LRFD were applied respectively. For the calculation of weight of steel structure, computer program was developed and applied to obtain beam weight. Using this program and GTSTRUDL, structural design program, weight of steel structure is calculated. As a result of weight calculation, maximum 5.4% of weight reduction is achieved among examples of this study by applying LRFD comparing with the result of ASD, and those results quite dependent on the applied load and member classification.

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