• Title/Summary/Keyword: 극한 한계 상태

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Seismic Fragility Analysis of Reinforced Concrete Bridge Piers According to Damage State (철근콘크리트 교량 교각의 손상상태에 따른 지진취약도 해석)

  • Jeon, Jeong Moon;Shin, Jae Kwan;Shim, Jae Yeob;Lee, Do Hyung
    • KSCE Journal of Civil and Environmental Engineering Research
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    • v.34 no.6
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    • pp.1695-1705
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    • 2014
  • In the present study, a total of 275 tested specimens (149 of non-seismically designed and 126 of seismically designed) for reinforced concrete bridge piers with circular section have been investigated in order to suggest drift limits probabilistically according to damage states in seismic fragility analysis. Thus, quantitative damage states of the piers have been evaluated depending on details of the piers. Nonlinear time-history analyses have been conducted for a damaged bridge in terms of using the suggested drift limits. Then, seismic fragility analysis for a reinforced concrete bridge structure has been conducted using both suggested and existing drift limits. Comparative analyses have revealed that median values by the suggested limits is smaller than those by the existing limits. This implies that seismic performance of the structure can be overestimated when the existing limits are used.

Deflection Calculation Based on Stress-Strain Curve for Concrete in RC Members (콘크리트 응력-변형률 관계에 기반한 철근콘크리트 부재의 처짐 산정)

  • Choi, Seung-Won;Kim, Woo
    • KSCE Journal of Civil and Environmental Engineering Research
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    • v.30 no.4A
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    • pp.383-389
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    • 2010
  • The concrete structural design provisions in Korea are based on ultimate strength design. Up to service load stage, it is assumed a linear stress-strain relation, but there is no stress-strain relationship for a concrete material from service load stage to limat state. According to the current provisions, an independent method is provided for the each calculation of deflection and crack width. In EC2 provisions based on limit state design, however, a stress-strain relationship of concrete is provided. Thereby, it is able to calculate a strength as well as a deflection directly from concrete stress-strain relationship. In this paper the moment-curvature relationship is directly calculated from a material law using equilibrium and compatibility conditions. Then strength and deflection are formulated. These results are compared with the values from the current provisions in Korea. From the results, the deflection based on a moment-curvature relationship is well agreed with experimental results and it is appeared that the deflection after the yielding of steel is also possible.

The Rigidity of Transverse Intermediate Stiffener of Horizontally Curved Plate Girder Web Panels (강곡선 플레이트거더 복부판의 중간수직보강재 소요강성에 관한 연구)

  • Lee, Doo Sung;Park, Chan Sik;Lee, Sung Chul
    • KSCE Journal of Civil and Environmental Engineering Research
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    • v.26 no.4A
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    • pp.735-742
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    • 2006
  • In this study, the ultimate shear strength behavior of transversely stiffened curved web panels was investigated through nonlinear finite element analysis. It was found that if the transverse stiffener has a sufficient rigidity, then curved web panels used in practical designs are able to develop the postbuckling strength that is equivalent to that of straight girder web panels having the same dimensional and material properties. The nonlinear analysis results indicate that in order for curved web panels to develop the potential postbuckling strength. The rigidity of the transverse stiffener needs to be increased several times the value obtained from the Guide Specifications (AASHTO, 2003). However, in the case of thick web panels where the shear design is governed by shear yielding, the stiffener rigidity does not have to be increased. From the analysis results, a simple design formula is suggested for the rigidity of transverse stiffener under strength limit state.

Experimental Study on Ultimate Shear Strength of Horizontally Curved Plate Girder Web Panels (강곡선 플레이트거더 복부판의 극한전단강도에 관한 실험연구)

  • Lee, Doo Sung;Park, Chan Sik;Lee, Sung Chul
    • KSCE Journal of Civil and Environmental Engineering Research
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    • v.26 no.4A
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    • pp.727-734
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    • 2006
  • Although a limited number of experimental investigations and finite element analyses revealed that a curved web panel in practical design has a considerable reserve strength after the elastic buckling as a straight girder web panel, the current Guide Specifications for Horizontally Curved Steel Girder Highway Bridges (AASHTO, 2003) do not consider the postbuckling strength in the ultimate shear strength due to lack of a comprehensive study. In this study, the ultimate shear strength behavior of horizontally curved steel web panels was investigated through nonlinear finite element analysis and experimental test. It was found that curved web panels used in practical designs are able to develop the postbuckling strength that is equivalent to that of straight girder web panels having the same dimensional and material properties.

Thermodynamic Study on the Limit of Applicability of Navier-Stokes Equation to Stationary Plane Shock-Waves (정상 평면충격파에 대한 Navier-Stokes 방정식의 적용한계에 관한 열역학적 연구)

  • Ohr, Young Gie
    • Journal of the Korean Chemical Society
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    • v.40 no.6
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    • pp.409-414
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    • 1996
  • The limit of applicability of Navier-Stokes equation to stationary plane shock-waves is examined by using the principle of minimum entropy production of linear irreversible thermodynamics. In order to obtain analytic results, the equation is linearized near the equilibrium of downstream. Results show that the solution of Navier-Stokes equation which fits the boundary condition of far downstream flow is consistent with the thermodynamic requirement within the first order when the solution is expanded around the M=1, where M is the Mach number of upstream speed.

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Evaluation of Domestic and Foreign Design Standards for Soil Nailing Method by Analysis of Slope Restoration Case (비탈면 복구사례 분석을 통한 쏘일네일링 공법의 국내외 설계기준 평가)

  • You, Kwang-Ho;Kim, Tae-Won
    • Journal of the Korean GEO-environmental Society
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    • v.20 no.11
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    • pp.11-22
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    • 2019
  • Limit state design (LSD) and allowable stress design (ASD) are two main types of soil nailing design methodologies. In the LSD method, stability is determined by applying individual coefficients to ground strength, working load and etc. The ASD method calculates the safety factor and compares it with the minimum safety factor to determine the stability. The global design trend of soil nailing system is changing from the ASD method to the LSD method. The design method in Korea still adopts the ASD philosophy while others mostly do the limit state design. In this study, four soil nail design methods, 'FHWA GEC 7' in U.S. (2015), 'Clouterre' in France (1991), 'Soil nailing - best practice guidance' in U.K. (2005), 'Geoguide 7' in Hongkong (2008), and 'Design guide for slope in construction work' in Korea (2016) were applied to the evaluation of the stability and the results were analyzed comparatively in brief. It is revealed that the design method of 'the overall stability of soil nail walls' in Korea is the most conservative and next those by FHWA, Clouterre and CIRIA become more conservative in order. However, the difference of results obtained from FHWA and Clouterre is negligible. Also, this study found out that efforts to improve domestic design criterion are needed.

Estimation of resistance coefficient of PHC bored pile by Load Test II (재하시험에 의한 PHC 매입말뚝의 저항계수 산정 II)

  • Park, Jong-Bae;Park, Yong-Boo;Kwon, Young-Hwan
    • Land and Housing Review
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    • v.9 no.3
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    • pp.1-8
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    • 2018
  • In Europe and the United States, the use of limit states design has almost been established for pile foundation design. According to the global trend, the Ministry of Land, Transport and Maritime Affairs has established the basic design criteria of the bridge under the limit state design method. However, it is difficult to reflect on the design right now because of lack of research on resistance coefficient of the pile method and ground condition. In this study, to obtain the resistance coefficient of PHC bored pile which is widely used in Korea, the bearing capacity calculated by the LH design standard and the bridge design standard method, the static load test(21 times) and the dynamic load test(EOID 21 times, Restrike 21) The reliability analysis was performed on the results. The analysis of the resistance coefficient of PHC bored pile by loading test was analyzed by adding more than two times data. As a result, the resistance coefficient obtained from the static load test(ultimate bearing capacity) was 0.64 ~ 0.83 according to the design formula and the target reliability index, and the resistance coefficient obtained from the dynamic load test(ultimate bearing capacity) was 0.42~0.55. Respectively. The resistance coefficient obtained from the modified bearing capacity of dynamic load test(EOID's ultimate end bearing capacity + restrike's ultimate skin bearing capacity) was 0.55~0.71, which was reduced to about 14% when compared with the resistance coefficient obtained by the static load test(ultimate bearing capacity). As a result of the addition of the data, the resistivity coefficient was not changed significantly, even if the data were increased more than 2 times by the same value or 0.04 as the previous resistance coefficient. In conclusion, the overall resistance coefficient calculated by the static load test and dynamic load tests in this study is larger than the resistance coefficient of 0.3 suggested by the bridge design standard(2015).

Target Reliability Index of Single Gravel Compaction Piles for Limit State Design (한계상태설계를 위한 단일 쇄석다짐말뚝의 목표신뢰도지수)

  • You, Youngkwon;Lim, Heuidae;Park, Joonmo
    • Journal of the Korean GEO-environmental Society
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    • v.15 no.2
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    • pp.5-15
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    • 2014
  • Target reliability index in the limit state design indicated the safety margin and it is important to determine the partial factor. To determine the target reliability index which is needed in the limit state design, the six design and construction case histories of gravel compaction piles (GCP) were investigated. The limit state functions were defined by bulging failure for the major failure mode of GCP. The reliability analysis were performed using the first order reliability method (FORM) and the reliability index was calculated for each ultimate bearing capacity formulation. The reliability index of GCP tended to be penportional to the safety factor of allowable stress design and average value was ${\beta}$=2.30. Reliability level that was assessed by reliability analysis and target reliability index for existing structure foundations were compared and analyzed. As a result, The GCP was required a relatively low level of safety compared with deep and shallow foundations and the currd t reliability level were similar to the target reliability in the reinforced earth retaining-wall and soil-nailing. Therefore the target reliability index of GCP suggested as ${\beta}_T$=2.33 by various literatures together with the computed reliability level in this study.

Stochastic Reliability Analysis of Armor Units of Rubble-Mound Breakwaters Subject to Multiple Loads (다중하중에 따른 경사제 피복재의 추계학적 신뢰성 해석)

  • Lee, Cheol-Eung
    • Journal of Korean Society of Coastal and Ocean Engineers
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    • v.24 no.2
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    • pp.138-148
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    • 2012
  • A stochastic reliability analysis model has been developed for evaluating the time-dependent stability performance of armor units of rubble-mound breakwaters subjected to the multiple loads of arbitrary magnitudes which could be occurred randomly. The initial structural capacities and the damage rates of armor units of rubble-mound breakwaters could be estimated as a function of the incident wave height with a given return period by using the modified Hudson's formula and Melby's formula. The structural stability performances of armor units of rubble-mound breakwaters could be analyzed in detail through the lifetime reliability investigations according to the limit states such as the serviceability or ultimate limit state and the conditions of multiple loads. Finally, repair intervals for the structural management of armor units of rubble-mound breakwaters could quantitatively be evaluated by a new approach suggested in this paper that has been based on the target probability for repair and the accumulated probabilities of failure obtained from the present stochastic reliability analysis model.

Estimation of Flexural Strength of Hollow Prestressed Concrete Filled Steel Tube Piles (긴장력이 도입된 중공형 콘크리트 충전 강관말뚝의 휨강도 산정)

  • Paik, Kyu-Ho
    • Journal of the Korean Geotechnical Society
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    • v.35 no.12
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    • pp.91-100
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    • 2019
  • Hollow prestressed concrete-filled steel tube (HCFT) piles, which combines PHC piles inside thin-wall steel tubes, were developed to increase the flexural strength of the pile with respect to the lateral load. Since P-M curves are needed for evaluating the structural safety of piles when applying HCFT piles to fields, equations for plotting P-M curves of HCFT piles in limit states were proposed. When the yield strength is applied to the steel tube and PC steel bar of HCFT piles, the proposed equations significantly underestimated the flexural strength of HCFT piles. Unlike the flexural strength test results, the proposed equations also provide greater flexural strengths for 12 mm thick steel pipe piles with the same diameter than for HCFT piles. However, when the ultimate strengths are used instead of the yield strengths for the steel tube and PC steel bar, the proposed equations provide the flexural strengths very close to the flexural strength test results.