• Title/Summary/Keyword: Constant-ductility

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Seismic Performance Evaluation of Reinforced Concrete Columns Under Constant and Varying Axial Forces (일정 및 변동 축력을 받는 철근콘크리트 기둥의 내진성능 평가)

  • Lee, Do Hyung
    • Journal of the Earthquake Engineering Society of Korea
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    • v.28 no.1
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    • pp.59-65
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    • 2024
  • This paper describes the seismic performance evaluation of reinforced concrete bridge columns under constant and varying axial forces. For this purpose, nine identical circular reinforced concrete columns were designed seismically by KIBSE (2021) and KCI (2021). A comparison of lateral forces with theoretical strength shows that the safety factor for columns under varying axial forces is less marginal than those under constant axial forces. In addition, columns under varying axial forces exhibit significant fluctuations in the hysteretic response due to continuously varying axial forces. This is particularly prominent when many varying axial force cycles within a specific lateral loading cycle increase. Moreover, the displacement ductility of columns under varying axial forces does not meet the code-specified required ductility in the range of varying axial forces. All varying axial forces affect columns' strength, stiffness, and displacement ductility. Therefore, axial force variation needs to be considered in the lateral strength evaluation of reinforced concrete bridge columns.

복합조직의 파괴거동과 파괴혁성에 관한 연구 I

  • ;;Kim, Kyu Seng
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.5 no.2
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    • pp.110-121
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    • 1981
  • In order to study on the fracture behavior and the fracture thoughness of combined structure, the specimens, structural steel (SM28C) and 6:4 brass are annealed for ductility and investigated for the befavior of fracture and the absorbed energy at the variation of the impact velocity. The results obtained by this study are as follows: (1)The maximum load increases with the impact velocity, but in the condition of constant impact velocity it decreases as the ductility increases. (2)The absorbed energy increases with the impact velocity, but in the condition of constant impact velocity it is constant as the ductility increases. (3)In the case of the combined structure of peralite and ferrite, the microcracks initiates and propagates mainly in the ferrite structure intergranular in accompany with the slip, and the slip concentration phenomena occur in the boundary of pearlite structure However, in case of the combined structure of .alpha. and ..betha. phase, the microcracks initiates and propagares mainly in the .alpha. phase intergranularly, and slip concentration phenomena not ocur in the boundary of .betha. phase.

Capacity Spectrum Method for Seismic Performance Evaluation of Multi-Story Building Based on the Story Drift (층간변위를 기반으로 한 다층구조물의 내전성능 평가를 위한 역량스펙트럼법의 개발)

  • Kim, Sun-Pil;Kim, Doo-Kie;Kwak, Hyo-Gyoung;Ko, Sung-Huck;Seo, Hyeong-Yeol
    • Proceedings of the Computational Structural Engineering Institute Conference
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    • 2007.04a
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    • pp.205-210
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    • 2007
  • The existing capacity spectrum method (CSM) is based on the displacement based approach for seismic performance and evaluation. Currently, in the domestic and overseas standard concerning seismic design, the CSM to obtain capacity spectrum from capacity curve and demand spectrum from elastic response spectrum is presented. In the multistory building, collapse is affected more by drift than by displacement, but the existing CSM does not work for story drift. Therefore, this paper proposes an improved CSM to estimate story drift of structures through seismic performance and evaluation. It uses the ductility factor in the A-T domain to obtain constant-ductility response spectrum from earthquake response of inelastic system using the drift and capacity curve from capacity analysis of structure.

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Comparative Evaluation of Nonlinear Seismic Responses of Bridge Structures Using Different Analysis Technique (해석방법에 따른 교량 구조물의 비선형지진응답 비교연구)

  • Kwon, Kyong-Il;Joe, Yang-Hee;Kim, Jae-Suk
    • Proceedings of the Earthquake Engineering Society of Korea Conference
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    • 2005.03a
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    • pp.396-404
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    • 2005
  • Nonlinear responses of structures may be obtained through three different methods. They are time-history analysis techniques, response spectrum method, and R-factor method. The nonlinear response spectrum method is frequently used in the practice, because the time history analysis method is time-consuming and complicated. There are two different approaches in obtaining the nonlinear response spectrum, which results in "constant displacement ductility spectra" and "constant damage spectra", respectively. The nonlinear response spectra of the various time-histories had been computed and the results were comparatively evaluated in this study. The study results showed that the existing constant displacement ductility spectra can induce unconservative design especially for the structures on soft soil base. This unconservatism can be removed by using the newly proposed constant damage spectra.

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Seismic Evaluation of concrete-Filled Steel Piers with Secondary Reinforcement (보조보강재가 있는 콘크리트 충전 강교각의 내진성능 평가)

  • 박병기
    • Proceedings of the Earthquake Engineering Society of Korea Conference
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    • 2000.04a
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    • pp.349-356
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    • 2000
  • Strenght and ductility are major factors in the aseismic design of a bridge pier. In spite of good performance in both steel piers have not been used widely due to high cost. But with the filled-in concrete the steel pier have advantages compare to the steel pier only such as improved strength ductility fast construction small section and reasonable cost. In this paper concrete-filled steel piers are tested using quasi-static cyclic lateral load with constant axial load to evaluate the performance. The secondary reinforcement devices such as bolts corner plate and turn buckle are used inside of the piers to improve the ductility with minimum additional cost. Test results shows filled-in concrete and secondary reinforcement devices increase the strength and the ductility of the steel pier.

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Seismic Ductility Assessment of RC Bridge Piers With Minor Earthquake Damage By the Quasi Static Test (유사정적실험에 의한 지진이력 철근콘크리트 교각의 내진 연성도 평가)

  • 이은희;정영수;박창규;김영섭
    • Proceedings of the Korea Concrete Institute Conference
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    • 2003.05a
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    • pp.505-511
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    • 2003
  • Experimental investigation was conducted into the flexure/shear-critical behavior of earthquake-damaged reinforced concrete columns with lap splicing of longitudinal reinforcement in the plastic hinge region. Six test specimens in the aspect ratio of 2,5 were made with test parameters: confinement ratios, lap splices, and retrofitting FRP materials. They were damaged under series of artificial earthquakes of which magnitude could be compatible in Korean peninsula. Directly after the pseudo-dynamic test, damaged columns were retested under inelastic reversal cyclic loading simultaneously under a constant axial load, P=$0.1f_{ck}A_g. Residual seismic performance of damaged columns was evaluated and compared to that of the corresponding original columns. Test results show that RC bridge piers with lap-spliced longitudinal steels in the plastic hinge region appeared to fail at low ductility. This was due to the debonding of the lap splice, which resulted from insufficient development of the longitudinal steels. The specimens externally wrapped with composite FRP straps in the potential plastic hinge region indicated significant improvement both in flexural strength and displacement ductility, and strain energy ductility.

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Experimental study on seismic behavior of frame structures composed of concrete encased columns with L-shaped steel section and steel beams

  • Zeng, Lei;Ren, Wenting;Zou, Zhengtao;Chen, Yiguang;Xie, Wei;Li, Xianjie
    • Earthquakes and Structures
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    • v.16 no.1
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    • pp.97-107
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    • 2019
  • The frame structures investigated in this paper is composed of Concrete encased columns with L-shaped steel section and steel beams. The seismic behavior of this structural system is studied through experimental and numerical studies. A 2-bay, 3-story and 1/3 scaled frame specimen is tested under constant axial loading and cyclic lateral loading applied on the column top. The load-displacement hysteretic loops, ductility, energy dissipation, stiffness and strength degradation are investigated. A typical failure mode is observed in the test, and the experimental results show that this type of framed structure exhibit a high strength with good ductility and energy dissipation capacity. Furthermore, finite element analysis software Perform-3D was conducted to simulate the behavior of the frame. The calculating results agreed with the test ones well. Further analysis is conducted to investigate the effects of parameters including concrete strength, column axial compressive force and steel ratio on the seismic performance indexes, such as the elastic stiffness, the maximum strength, the ductility coefficient, the strength and stiffness degradation, and the equivalent viscous damping ratio. It can be concluded that with the axial compression ratio increasing, the load carrying capacity and ductility decreased. The load carrying capacity and ductility increased when increasing the steel ratio. Increasing the concrete grade can improve the ultimate bearing capacity of the structure, but the ductility of structure decreases slightly.

Inelastic behavior of systems with flexible base

  • Fernandez-Sola, Luciano R.;Huerta-E catl, Juan E.
    • Earthquakes and Structures
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    • v.14 no.5
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    • pp.411-424
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    • 2018
  • This study explores the inelastic behavior of systems with flexible base. The use of a single degree of freedom system (ESDOF) with equivalent ductility to represent the response of flexible base systems is discussed. Two different equations to compute equivalent ductility are proposed, one which includes the contribution of rigid body components, and other based on the overstrength of the structure. In order to asses the accuracy of ESDOF approach with the proposed equations, the behavior of a 10-story regular building with reinforced concrete (RC) moment resisting frames is studied. Local and global ductility capacity and demands are used to study the modifications introduced by base flexibility. Three soil types are considered with shear wave velocities of 70, 100 and 250 m/s. Soil-foundation stiffness is included with a set of springs on the base (impedance functions). Capacity curves of the building are computed with pushover analysis. In addition, non linear time history analysis are used to asses the ductility demands. Results show that ductility capacity of the soil-structure system including rigid body components is reduced. Base flexibility does not modify neither yield and maximum base shear. Equivalent ductility estimated with the proposed equations is fits better the results of the numerical model than the one considering elastoplastic behavior. Modification of beams ductility demand due to base flexibility are not constant within the structure. Some elements experience reduced ductility demands while other elements experience increments when flexible base is considered. Soil structure interaction produces changes in the relation between yield strength reduction factor and structure ductility demand. These changes are dependent on the spectral shape and the period of the system with fixed and flexible base.

Effects of loading history on seismic performance of SRC T-shaped column, Part I: Loading along web

  • Wang, J.;Liu, Z.Q.;Xue, J.Y.;Hu, C.M.
    • Structural Engineering and Mechanics
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    • v.68 no.2
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    • pp.193-201
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    • 2018
  • This paper describes an experimental study on the seismic performance of steel reinforced concrete (SRC) T-shaped columns. The lateral loads were applied along the web of the column with different loading histories, such as monotonic loading, mixed loading of variable amplitude cyclic loading and monotonic loading, constant amplitude cyclic loading and variable amplitude cyclic loading. The failure modes, load-displacement curves, characteristic loads and displacements, ductility, strength and stiffness degradations and energy dissipation capacity of the column were analyzed. The effects of loading history on the seismic performance were focused on. The test results show that the specimens behaved differently in the aspects of the failure mode subject to different loading history, although all the failure modes can be summarized as flexural failure. The hysteretic loops of specimens are plump, and minimum values of the failure drift angles and ductility coefficients are 1/24 and 4.64, respectively, which reflect good seismic performance of SRC T-shaped column. With the increasing numbers of loading cycles, the column reveals lower bearing capacity and ductility. The strength and stiffness of the column with variable amplitude cyclic loading degrades more rapidly than that with constant amplitude cyclic loading, and the total cumulative dissipated energy of the former is less.

Structural response analysis in time and frequency domain considering both ductility and strain rate effects under uniform and multiple-support earthquake excitations

  • Liu, Guohuan;Lian, Jijian;Liang, Chao;Zhao, Mi
    • Earthquakes and Structures
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    • v.10 no.5
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    • pp.989-1012
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    • 2016
  • The structural dynamic behavior and yield strength considering both ductility and strain rate effects are analyzed in this article. For the single-degree-of-freedom (SDOF) system, the relationship between the relative velocity and the strain rate response is deduced and the strain rate spectrum is presented. The ductility factor can be incorporated into the strain rate spectrum conveniently based on the constant-ductility velocity response spectrum. With the application of strain rate spectrum, it is convenient to consider the ductility and strain rate effects in engineering practice. The modal combination method, i.e., square root of the sum of the squares (SRSS) method, is employed to calculate the maximum strain rate of the elastoplastic multiple-degree-of-freedom (MDOF) system under uniform excitation. Considering the spatially varying ground motions, a new response spectrum method is developed by incorporating the ductility factor and strain rate into the conventional response spectrum method. In order to further analyze the effects of strain rate and ductility on structural dynamic behavior and yield strength, the cantilever beam (one-dimensional) and the triangular element (two-dimensional) are taken as numerical examples to calculate their seismic responses in time domain. Numerical results show that the permanent displacements with and without considering the strain rate effect are significantly different from each other. It is not only necessary in theory but also significant in engineering practice to take the ductility and strain rate effects into consideration.