• Title, Summary, Keyword: plastic hinge length

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Evaluation of Axial Strains of Reinforced Concrete Columns (철근콘크리트 기둥의 축방향 변형률 평가)

  • Lee, Jung-Yoon;Kim, Min-Ok;Kim, Hyung-Beom
    • Journal of the Korea Concrete Institute
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    • v.25 no.1
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    • pp.19-28
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    • 2013
  • The longitudinal axial strain in the plastic hinge region of reinforced concrete (RC) columns influences on the structural behavior of RC structures subjected to reversed cyclic loading. This strain decreases the effective compressive strength of concrete and increases the lateral displacements between stories by causing the elongation of member length. This paper investigated the effects of the axial force on the elongation of a RC member by using a sectional analysis of RC members. The analytical and experimental results indicated that the axial force decreased the axial strain in the plastic hinge region of RC columns. In this study, a model was proposed to predict the axial strain of RC columns. The proposed model considering the effects of axial force ratio consisted of three path types ; Path 1-loading region, Path 2-unloading region, and Path 3-reversing cyclic loading region. The axal strains predicted by the proposed model were compared with the test results of RC columns with various axial force ratios, and agreed reasonably with the observed longitudinal strains.

Comparisons of Seismic Behaviors of Columns in Concrete Moment Frames (기존 기둥 실험결과 비교를 통한 기둥성능 평가)

  • 박성일;한상환;이리형
    • Proceedings of the Korea Concrete Institute Conference
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    • pp.571-576
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    • 2001
  • The objective of this study is to assess seismic damage potential and evaluate structural performance of columns in concrete moment frames. For this purpose the results of 3 former studies are compared. Experimental variables considered in these studies are lap-splice of longitudinal reinforcement, axial load level, longitudinal reinforcement ratio, etc. The columns in 1st story of the building are considered in these studies since the columns in 1st story shall resist largest axial force during an earthquake. Based on test results strength, ductility capacities as well as plastic hinge length are compared and discussed.

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Semi-rigid Elasto-Plastic Post Buckling Analysis of Space Frame by Using the Explicit Arc-Length Method (명시적 호장법을 이용한 공간프레임의 반강접 탄소성 후좌굴 해석)

  • Lee, Kyoung-Soo;Han, Sang-Eul
    • Journal of Korean Society of Steel Construction
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    • v.23 no.5
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    • pp.535-546
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    • 2011
  • In this paper, semi-rigid elasto-plastic post-buckling analysis of a space frame was performed using various explicit arc-length methods. Various explicit arc-length methodsand a large-deformation and small-strain elasto-plastic 3D space frame element with semi-rigid connections and plastic hinges were developed. This element can be appliedto both explicit and implicit numerical algorithms. In this study, the Dynamic Relaxation method was adopted in the predictor and corrector processesto formulate an explicit arc-length algorithm. The developed "explicit-predictor" or "explicit-corrector" were used in the elasto-plastic post-buckling analysis. The Eulerian equations for a beam-column with finite rotation, which considers the bowing effects, were adopted for the elastic system and extended to theinelastic system with a plastic hinge concept. The derived tangent stiffness matrix was asymmetrical due to the finite rotation. The joint connection elements were introduced for semi-rigidity using a static condensation technique. Semi-rigid elasto-plastic post-buckling analyses were carried out to demonstrate the potential of the developed explicit arc-length method and advanced space frame element in terms of accuracy and efficiency.

Evaluation of ductility and response modification factor in moment-resisting steel frames with CFT columns

  • Hashemi, Seyed Sh.;Sadeghi, Kabir;Vaghefi, Mohammad;Shayan, Kaveh
    • Earthquakes and Structures
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    • v.12 no.6
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    • pp.643-652
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    • 2017
  • One of the methods to strengthen the structures against the seismic lateral loading is the employment of the composite columns. A concrete-filled tube (CFT) has the cumulative advantages of steel and concrete. Concrete-filled steel tube columns have been widely used in the moment-resisting frame (MRF) structures, located in both non-seismic zones and high-risk seismic zones. In this paper, the results of studies on two important seismic parameters of ductility and the response modification factor (RMF) of the MRFs with CFT columns are submitted. While the studies are carried out, the effects of span length-story height ratio, the strength of materials and seismic behavior of MRFs are considered. In this regard, the ductility, RMF and the strength of 36 models of the steel MRFs with CFTs are analyzed. The fiber plastic hinges numerical simulation and pushover analysis method are used in the calculations. Based on the obtained results, the RMFs suitable for the 5-, 10- and 15- story frames are proposed.

Effects of Lap Splice Details on Seismic Performance of RC Columns (RC기둥의 내진성능에 미치는 겹침 이음상세의 영향)

  • Kim, Chul-Goo;Park, Hong-Gun;Kim, Tae-Wan;Eom, Tae-Sung
    • Journal of the Earthquake Engineering Society of Korea
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    • v.20 no.6
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    • pp.351-360
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    • 2016
  • In regions of low-to-moderate seismicity, various types of lap splices are used for longitudinal reinforcement of columns at the plastic hinge zones. The seismic performance of such lap spliced columns, such as strength, deformation capacity, and energy dissipation, is affected by material strengths, longitudinal re-bar size, confinement of hoops, lap splice location, and lap splice length. In the present study, cyclic loading tests were performed for columns using three types of lap splices (bottom offset bar splice, top offset bar splice, and splice without offset bend). Lap splice length($40d_b$ and $50d_b$) was also considered as test parameters. Ties with 90-degree end hooks were provided in the lap splice length. The test results showed that strength, deformation capacity, and energy dissipation of columns significantly differed depending on the details and the length of lap splices. The bottom offset bar splice showed high ductility and energy dissipation but low strength; on the other hand, the top offset bar splice and the splice without offset bend showed high strength but moderate ductility and energy dissipation.

Nonlinear Dynamic Analysis of Space Steel Frames (공간 강뼈대 구조물의 비선헝 동적 해석)

  • Kim Seung-Eock;Cuong Ngo-Huu;Lee Dong-Ho
    • Journal of the Computational Structural Engineering Institute of Korea
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    • v.18 no.4
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    • pp.395-404
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    • 2005
  • This paper presents a reliable numerical procedure for nonlinear time-history analysis of space steel frames subjected to dynamic loads. Geometric nonlinearities of member (P-$\delta$) and frame (P-$\Delta$) are taken into account by the use of stability functions in framed stiffness matrix formulation. The gradual yielding along the member length and over the cross section is included by using a tangent modulus concept and a softening plastic hinge model based on the New-Orbison yield surface. A computer program utilizing the average acceleration method for the integration scheme is developed to numerically solve the equation of motion of framed structure formulated in an incremental form. The results of several numerical examples are compared with those derived from using beam element model of ABAQUS program to illustrate the accuracy and the computational efficiency of the proposed procedure.

Cyclic testing of weak-axis column-tree connections with formation of plastic hinge at beam splice

  • Oh, Keunyeong;Chen, Liuyi;Hong, Sungbin;Yang, Yang;Lee, Kangmin
    • Earthquakes and Structures
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    • v.8 no.5
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    • pp.1039-1054
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    • 2015
  • The purpose of this study was to evaluate the seismic performance of weak-axis column-tree type connections used in steel moment frames. These connections are composed of a shop-welded and fieldbolted steel structure and can improve welding quality. On this basis, column-tree type connections are widely used in steel moment resisting frames in Korea and Japan. In this study, splices designed with a semirigid concept regarding the seismic performance of column-tree connections were experimentally evaluated. The structures can absorb energy in an inelastic state rather than the elastic state of the structures by the capacity design method. For this reason, the plastic hinge might be located at the splice connection at the weak-axis column-tree connection by reducing the splice plate thickness. The main variable was the distance from the edge of the column flange to the beam splice. CTY series specimens having column-tree connections with splice length of 600 mm and 900 mm were designed, respectively. For comparison with two specimens with the main variable, a base specimen with a weak-axis column-tree connection was fabricated and tested. The test results of three full-scale test specimens showed that the CTY series specimens successfully developed ductile behavior without brittle fracture until 5% story drift ratio. Although the base specimen reached a 5% story drift ratio, brittle fracture was detected at the backing bar near the beam-to-column connection. Comparing the energy dissipation capacity for each specimen, the CTY series specimens dissipated more energy than the base specimen.

Measurement of Structural Properties of PLA Filament as a Supplier of 3D Printer (3D 프린터에 공급되는 PLA 필라멘트의 물성치 측정)

  • Choi, Won;Woo, Jae-Hyeong;Jeon, Jeong-bae;Yoon, Seong-soo
    • Journal of The Korean Society of Agricultural Engineers
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    • v.57 no.6
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    • pp.141-152
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    • 2015
  • Most of agricultural structures are consisted of complex components and exposed to various boundary conditions. There have been no ways to express those structures exactly for model experiment. As an alternative, 3D printer can produce any type of solid model. However, there are limited informations related to structural experiments using 3D printer. The object of this study gives the basic informations to structural engineers who try to use 3D printer for model experiment. When PLA was used as a supplier for 3D printer, the outcomes showed less heat deformation to compare with ABS. To test the material properties, two kinds of experiments (three-point flexibility test and compression test) were executed using universal testing machine. In three-point flexibility test, plastic hinge and its deformation were developed as observed in material such as steel. The behavior was in a linear elastic state, and elastic bending modulus and yield force were evaluated. In the compression test using unbraced columns with hinge-hinge boundary condition, the constant yield forces were observed regardless of different lengths in all columns with same section size, whereas the compressive elastic modulus was increased as the length of column was increased. The suggested results can be used for model experiments of various agricultural structures consisted of single material.

A Study on Strength Characteristics of Yieldable Steel Arch Supports (가축성 강재 지보의 강도특성에 관한 연구)

  • 김종우
    • Tunnel and Underground Space
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    • v.8 no.4
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    • pp.261-274
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    • 1998
  • The brief results of laboratory and field tests of yieldable steel arches are represented. The test supports were fabricated with three U-sectional beams which are 25.8 kg/m of Glocken profile. The structural analyses of semi-circular and arch supports were conducted to find out shape factor of U beam to be 1.35 and the location of 2nd plastic hinges. Load capacity of arch supports under crown loading were examined as a function of leg length. Yieldable characheristics of test supports were investigated with various bolting torque of connection part. Determination method of bolting torque were also studied. Finally, test supports were installed in-situ with torque of 21 kg .m, which showed a typical yielding procedure.

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Quasi-Static Tests for seismic performance of RC bridge piers (철근콘크리트 교각의 내진성능에 관한 준정적 실험)

  • 이강균;한기훈;정영수;이대형;황의승
    • Proceedings of the Korea Concrete Institute Conference
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    • pp.615-620
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    • 1998
  • The objective of this experimental study is to investigate the hysteretic behavior of reinforced concrete piers subjected to quasi-static cyclic loads, which have been used in large numbers for railway and urban transportation facilities. Important test parameters are hoop ratio, axial load, loading type, and the behaviors f members have been evaluated through limit states of crack occurrence, yielding and ultimate state of member, ductility and load-deflection loop can be secured by considering the influence of hoop reinforcement ratio and axial load, and that plastic hinge length and ductility ar determined by the combination of the quantities of hoop reinforcement and axial load.

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