• Title, Summary, Keyword: ductility

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Evaluation of Ductility in Reinforced Concrete Members Using Material Models in Eurocode2 (유로코드 2 재료모형을 사용한 철근콘크리트 부재의 연성도 평가)

  • Choi, Seung Won
    • Journal of The Korean Society of Civil Engineers
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    • v.35 no.2
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    • pp.287-297
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    • 2015
  • In concrete structural design provisons, there is a minimum allowable strain of steel to ensure a ductility of RC members and a c/d is limited for the same purpose in EC2. In general, a ductility capacity of RC members is evaluated by a displacement ductility which is a ratio of ultimate displacement to yield displacement, and it is necessary to calculate accurately a yield displacement and an ultimate displacement to evaluate a displacement ductility. But a displacement in members is affected by various member characteristics, so it is hard to calculate a displacement exactly. In this study, a displacement ductility is calculated by calculating a yield displacement and an ultimate displacement through a moment-curvature relationship. The main variables examined are concrete strength, yield strength, steel ratio, spacing of confinement, axial force ratio and concrete ultimate strain. As results, as a concrete strength is increased, a ductility displacement is increased. But as yield strength, steel ratio, spacing of confinement and axial force ratio are increased, a displacement ductility is decreased. And a displacement ductility is necessary to calculate a response modification factor (R) of columns for seismic design, so it is appeared that it is important to calculate a displacement ductility more accurately.

Effect of Tension, Compression and Lateral Reinforcement In Ductility Ratio in RC Flexural Members (철근콘크리트 휨 부재에서 인장, 압축 및 횡보강근이 연성률에 미치는 효과)

  • 연규원;박찬수
    • Journal of the Korea Concrete Institute
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    • v.13 no.6
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    • pp.553-560
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    • 2001
  • The ductility capacity should be estimated for inelastic analysis and design of reinforced concrete flexural members. Therefore, to estimate the ductility capacity, the model of moment-curvature relationship of reinforced concrete flexural member is assumed in this study. The curvature, rotation, and displacement(deflection) of reinforced concrete cantilever beams are analyzed and tested. The analytical results are compared with the test results. According to the analytical and test results, the assumed model of moment-curvature relationship in this study is adequate in flexural analysis of reinforced concrete members because the analytical results are well agreed with the test results, and it is resonable to express the ductility capacity in the rotation or displacement ductility, Because the curvature ductility is the limited index in a certain section. It is investigated that the ductility capacity is proportional to lateral reinforcement and compression reinforcement and inversely proportional to tension reinforcement.

Ductility Relationship of RC Bridge Columns under Seismic Loading (지진하중을 받는 철근콘크리트 교각의 연성도 상관관계)

  • 손혁수;이재훈
    • Journal of the Earthquake Engineering Society of Korea
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    • v.7 no.4
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    • pp.51-61
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    • 2003
  • This research is a park of a research program to develope a new design method for reinforced concrete bridge columns under axial load and cyclic lateral load. The objectives of this paper are to investigate the relationship between curvature ductility and displacement ductility and to propose a correlation equation for designing of reinforced concrete bridge columns under axial load and cyclic lateral load. Computer program NARCC was used for parametric study, which was proved to provide good and conservative analytical result especially for deformation capacity and ductility factor compared with test result. A total of 7,200 spirally reinforced concrete columns were selected considering the main variables such as section diameter, aspect ratio, concrete strength, yielding strength of longitudinal and confinement steel, longitudinal steel ratio, axial load ratio, and confinement steel ratio. A new equation between curvature ductility factor displacement ductility factor with the aspect ratio was proposed by investigation of 21,600 data produced from the selected column models by applying 3 different definitions of yield displacement.

Ductility Confinement of RC Rectangular Shear Wall (장방형 철근 콘크리트 전단벽의 연성 보강)

  • 강수민;박홍근
    • Journal of the Korea Concrete Institute
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    • v.14 no.4
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    • pp.530-539
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    • 2002
  • In designing the boundary confinement of shear walls, the current design provisions and recommendations are empirical and prescriptive; they specify a certain confinement length and details, regardless of the actual requirement of ductility Therefore, they are inappropriate to the performance based-design. The purpose of the present study is to develop a ductility design method that Is applicable to the performance based-design of shear wall. For the purpose, experimental studies were performed to investigate variations in the ductility of shear walls with the length of the boundary confinement. Five specimens modeling the compressive zone of cross sections with different confinement area were tested against eccentric vertical load. Through the experimental studies, strength, ductility, and failure mode of the compression zone were investigated. In addition, nonlinear numerical analyses for the overall cross-sections of shear wall were performed to investigate variations of the stress and strain profiles with the length of compression zone. On the basis of the experimental and numerical studies, a ductility design method for shear wall was developed. By using the proposed design method, for a given ductility demand, the area of lateral confinement and corresponding reinforcement ratio can be precisely determined so that the ductile behavior and economical design are assured.

Evaluation of Ductility Factors for MDOF Systems in Special Steel Moment Resisting Frames (철골 연성 모멘트 골조에 대한 다자유도 시스템의 연성계수 평가)

  • Kang, Cheol-Kyu;Han, Young-Cheol
    • Journal of the Earthquake Engineering Society of Korea
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    • v.8 no.6
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    • pp.13-22
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    • 2004
  • Ductiluty factor has played an important role in seismic design as it is key component of response modification factor(R). In this stuty, ductility factors() are calculated by multiplying ductility factor for SDOF systems() and MDOF modification factors(). Ductility factors() for SDOF systems are computed from nonlinear dynamic analysis undergoing different level of displacement ductiluty demands and period when subjected to a large number of recorded earthquake ground motions. The MDOF modification factors() are proposed to account for the MDOF systems, based on previous studies. A total of 108 prototype steel frames are designed to investigate the ductility factors considering the number of stories(4, 8 and 16-stories), framing system(Perimeter Frames, PF and Distributed Frames, DF), failure mechanism(Strong-Column Weak-Beam, SCWB and Weak-Column Strong-Beam, WCSB), soil profiles(SA, SC and SE in UBC 1997) and seismic zone factors(Z=0.075, 0.2 and 0.4 in UBC 1997). It is shown that the number of stories, failure mechanisms (SCWB, WCSB), and soil profiles have great influence on the ductility factors, however, the structural system(Perimeter frames, Distributed frames), and seismic zones have no influence on the ductility factors.

Ductility demands and reduction factors for 3D steel structures with pinned and semi-rigid connections

  • Llanes-Tizoc, Mario D.;Reyes-Salazar, Alfredo;Ruiz, Sonia E.;Bojorquez, Eden;Bojorquez, Juan;Leal Graciano, Jesus M.
    • Earthquakes and Structures
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    • v.16 no.4
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    • pp.469-485
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    • 2019
  • A numerical investigation regarding local (${\mu}_L$) and story (${\mu}_S$) ductility demand evaluation of steel buildings with perimeter moment resisting frames (PMRF) and interior gravity frames (IGF), is conducted in this study. The interior connections are modeled, firstly as perfectly pinned (PP), and then as semi-rigid (SR). Three models used in the SAC steel project, representing steel buildings of low-, mid-, and high-rise, are considered. The story ductility reduction factor ($R_{{\mu}S}$) as well as the ratio ($Q_{GL}$) of $R_{{\mu}S}$ to ${\mu}_L$ are calculated. ${\mu}_L$ and ${\mu}_S$, and consequently structural damage, at the PMRF are significant reduced when the usually neglected effect of SR connections is considered; average reductions larger than 40% are observed implying that the behavior of the models with SR connections is superior and that the ductility detailing of the PMRF doesn't need to be so stringent when SR connections are considered. $R_{{\mu}S}$ is approximately constant through height for low-rise buildings, but for the others it tends to increase with the story number contradicting the same proportion reduction assumed in the Equivalent Static Lateral Method (ESLM). It is implicitly assumed in IBC Code that the overall ductility reduction factor for ductile moment resisting frames is about 4; the results of this study show that this value is non-conservative for low-rise buildings but conservative for mid- and high-rise buildings implying that the ESLM fails evaluating the inelastic interstory demands. If local ductility capacity is stated as the basis for design, a value of 0.4 for $Q_{GL}$ seems to be reasonable for low- and medium-rise buildings.

Modelling the Tensile Instability of Nanocrystalline Metallic Materials (나노금속재료의 인장불안정에 대한 모델링)

  • Kim H. S.
    • Proceedings of the Korean Society for Technology of Plasticity Conference
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    • pp.251-254
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    • 2001
  • In this paper, the effect of grain refinement on room temperature ductility of copper was addressed. Recent experimental results have shown that this material, as well as a number of other single-phase metals that are ductile when coarse-grained, loose their ductility with decreasing grain size in the sub micrometer range. A recently developed model in which such materials are considered as effectively two-phase ones (with the grain boundaries treated as a linearly viscous second phase) was applied to analyze stability of Cu against ductile necking. As a basis, Hart's stability analysis that accounts for strain rate sensitivity effects was used. The results confirm the observed trend for reduction of ductility with decreasing grain size. The model can be applied to predicting the grain size dependence of ductility of other metallic materials as well.

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Ductility of Column-Slab eoint in R/C Flat Plate System (플랫 플레이트 구조의 기둥.슬래브 접합부 연성에 관한 연구)

  • 김형기;박복만
    • Journal of the Korea Concrete Institute
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    • v.12 no.4
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    • pp.113-119
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    • 2000
  • The R/C flat plate system provides architectural flexibility, clear space, reduced building height, simple formwork, which consequently enhance constructibility. One of the serious problems in the flat plate system is brittle punching shear failure due to transfer of shear force and unbalanced moments in column-slab joint. Recently, the flat plate system accompanied with shear walls to resist the lateral loads is applied to high-rise buidings. Although the flat plate system is not considered in design as part of the lateral load-resisting system, it is required that this system keeps the ductile behavior for the lateral displacement of the building. However, it is unclear whether the column-slab joint possesses ductility enough to survive the lateral deformation. The objective of this paper is to investigate the major parameters that influence the ductility of R/C flat plate system by examining the existing experiments on column-slab joint. The effects of gravity load and shear reinforcement on the ductility of the flat plate system are presented.

Seismic Design Methodology of RC Bridge Columns based on Ductility (연성도를 고려한 철근콘크리트 교각의 내진설계방법에 관한 연구)

  • 이재훈;손혁수;김준범
    • Proceedings of the Korea Concrete Institute Conference
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    • pp.135-140
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    • 2002
  • Bridge columns in strong earthquake area are to be designed and constructed so that enough ductility should be guaranteed. Therefore, large amount of transverse reinforcement is required to confine core concrete of the bridge column by design specifications. In moderate seismicity regions, however, adopting the full ductility design concept sometimes results in construction problems due to reinforcement congestion. For the moderate seismicity regions, a design based on required ductility and required transverse reinforcement might be a reasonable approach. Ductility demand design or performance-based design might be an appropriate approach especially for regions of moderate seismic risk. The procedure and application of this design approach are presented in this paper.

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Responses of Equivalent SDOF System for System Ductility Demands Evaluation of Multistory Building Structures (건축구조물의 시스템 연성요구도 평가를 위한 대표응답의 활용)

  • 최원호;이동근
    • Proceedings of the Computational Structural Engineering Institute Conference
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    • pp.446-453
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    • 2001
  • System-level ductility is an essential parameter for seismic performance evaluation of multistory building structures. The ductility demands for single degree of freedom structures or individual structural members can be determined easily. However, there is no clearly established method to determine the ductility demands for structural systems. The system ductility demands are estimated in this study by the equivalent SDOF system methods and proposed method which used the representative responses obtained from the MDOF systems directly. And seismic performance of building structures is evaluated by the modified Capacity Spectrum Method using the representative responses, and the result was compared with those of the inelastic time history analysis.

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