• Title/Summary/Keyword: seismic behavior

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Comparison of Lateral Pile Behavior under Static and Dynamic Loading by Centrifuge Tests (원심모형 실험을 이용한 지반-말뚝 상호작용의 정적 및 동적 거동 평가)

  • Yoo, Min-Taek;Kwon, Sun-Yong
    • Journal of the Korean Geotechnical Society
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    • v.34 no.7
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    • pp.51-58
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    • 2018
  • In this study a series of centrifuge tests were carried out in dry sand to analyze the comparison of lateral pile behavior for static loading and dynamic loading condition. In case of static loading condition, the lateral displacement was applied up to 50% of pile diameter by deflection control method. And the input sine wave of 0.1 g~0.4 g amplitude and 1 Hz frequency was applied at the base of the soil box using shaking table for dynamic loading condition. From comparison of experimental static p-y curve obtained from static loading tests with API p-y curves, API p-y curves can predict well within 20% error the ultimate subgrade reaction force of static loading condition. The ultimate subgrade reaction force of experimental dynamic p-y curve is 5 times larger than that of API p-y curves and experimental static p-y curves. Therefore, pseudo-static analysis applied to existing p-y curve for seismic design could greatly underestimate the soil resistance at non-linear domain and cause overly conservative design.

Dynamic Behavior of Offshore Waste Landfill Revetment with Geosynthethic-Soil Interface (토목섬유 접촉면을 포함한 해상 폐기물처분장 호안구조물의 동적 거동)

  • Kwak, Chang Won;Oh, Myoung Hak;Park, Inn Joon;Jang, Dong In
    • Journal of the Korean Geotechnical Society
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    • v.33 no.12
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    • pp.141-150
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    • 2017
  • Geosynthetics are generally utilized to restrain the leakage of leachate and other contaminants during the construction of offshore waste landfill. Therefore, geosynthetic-soil interface is formed inevitably. In this study, 2 dimensional numerical analysis is performed to assess the dynamic behaviour of the offshore waste landfill including geosynthetic-soil interface. Offshore waste landfill can be divided into rubble mound revetment and retaining wall types and analyzed on each type. Effective stress analysis is conducted to consider the variation of pore water pressure and axial force and shear displacement of the interface are compared based on the characteristics of seismic frequency. Consequently, retaining wall type demonstrates more stable behavior against liquefaction potential and favorable forces and shear displacement.

Analytical Study for Performance Evaluation of Studs for Steel Plate Concrete(SC) Walls subjected to Cyclic Loads (반복하중이 가해지는 강판 콘크리트(SC) 벽체에서 스터드의 성능평가를 위한 해석적 연구)

  • Lim, Jin-Sun;Jeong, Young-Do;Yi, Seong-Tae
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.19 no.4
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    • pp.35-42
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    • 2015
  • This study analytically reviewed the behavior of Steel Plate Concrete(SC) walls subjected to cyclic loads to investigate the effects of shape and arrangement spacing of studs on the behavior of SC walls. To perform it, 9 cases of finite element analyses considering the different shape and spacing of studs in SC wall were carried out. As the results, the skeleton curves were obtained from the load-displacement history curves and the ultimate and yielding forces were increased as the spacing of studs decrease. In addition, the strength of inclined studs are shown to be bigger compared to that of general studs. The damping ratios are increased as the decrease of strength ratio. Finally, as the decrease of stud spacings, the cumulative dissipated energy was increased and the seismic performance was improved.

Effects of Transverse Reinforcement on Flexural Strength and Ductility of High-Strength Concrete Columns (횡보강근에 따른 고강도 콘크리트 기둥의 휨강도와 연성)

  • 황선경;윤현도;정수영
    • Journal of the Korea Concrete Institute
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    • v.14 no.3
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    • pp.365-372
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    • 2002
  • This experimental investigation was conducted to examine the behavior of eight a third scale columns made of high-strength concrete(HSC). The columns were subjected to constant axial load corresponding to target value of 30 percent of the column axial load capacity and a cyclic horizontal load-inducing reversed bending moment. The variables studied in this research are the volumetric ratio of transverse reinforcement(Ps=1.58, 2.25 %), tie configuration(hoop-type, cross-type, diagonal-type) and tie yield strength(fy=5,600, 7,950 kgf/$\textrm{cm}^2$). Test results indicated that the flexural strength of all the columns did not exceed calculated flexural capacities based on the equivalent concrete stress block used in current design code. Columns with 42 percent higher amounts of transverse reinforcement than that required by seismic provisions of ACI 318-99 were shown ductile behavior. With axial load of 30 percent of the axial load capacity, the use of high-strength steel as transverse reinforcement may lead to equal or higher ductility than would be achieved with low-strength steel.

Strength of Exterior Flat Plate-Column Connections Subjected to Unbalanced Moment (불균형 휨모멘트를 받는 플랫 플레이트-기둥 외부접합부의 강도)

  • Choi, Kyoung-Kyu;Park, Hong-Gun
    • Journal of the Korea Concrete Institute
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    • v.15 no.3
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    • pp.470-481
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    • 2003
  • Exterior plate-column connection has an unsymmetrical critical section for eccentric shear of which perimeter is less than that of interior connection, and hence, around the connection, unbalanced moment and eccentric shear are developed by both gravity load and lateral loads. Therefore, exterior connection is susceptible to punching shear failure. Current design provision cannot accurately explain strength of existing experiments, partly due to the complexity in the behavior of exterior plate-column connection, or partly due to the theoretical deficiency of the strength analysis model adopted. In the present study, nonlinear finite element analyses were performed for exterior connections belonging to continuous flat plate. For each direction of lateral load, the behavior and strength of exterior plate-column connection were quite different. Based on the numerical result, strength prediction model for exterior connection was proposed for each direction of lateral load. Compared with existing experiments, the proposed method was verified.

An Experimental Study on the Flexural Behavior of Reinforced Concrete Columns Strengthened with Wire Rope and T-Shape Steel Plate units (와이어로프와 T형 플레이트에 의해 보강된 RC 기둥의 휨 거동에 대한 실험적 연구)

  • Sim, Jae-Il;Yang, Keun-Hyeok;Oh, Sung-Jin;Byun, Hang-Yong
    • Proceedings of the Korea Concrete Institute Conference
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    • 2008.04a
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    • pp.153-156
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    • 2008
  • The objective of the present study is to evaluate the flexural behavior of reinforced concrete columns externally strengthened with wire rope and T-shape steel plate units. Three strengened columns and a control unstrengthened column were tested under cyclic lateral load simultaneously subjected to a constant axial load. All columns had same section size, and the arrangement of longitudinal reinforcement and internal hoop. The spacing of wire rope range from 40 ${\sim}$ 80mm, which corresponds from 1.0 ${\sim}$ 0.5, respectively, times the minium amount of hoop specified in seismic design of ACI 318-05. Test results showed that the proposed unbonded-type strengthening procedure is very effective for improving the flexural ductility of reinforced concrete columns.

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Effects of Cover Thickness on Confining Transverse Reinforcement of RC Bridge Columns (철근콘크리트 교각 심부구속 횡방향철근량 산정식의 피복두께 영향)

  • Son, Hyeok-Soo;Lee, Jae-Hoon;Suh, Suk-Koo;Oh, Myung-Seok;Yoon, Cheol-Kyun
    • Proceedings of the Korea Concrete Institute Conference
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    • 2008.04a
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    • pp.81-84
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    • 2008
  • The equation, specified in current bridge design code, for calculating the confining transverse reinforcement amount of RC bridge columns has been made to provide additional load-carrying strength for concentrically loaded columns equal to or slightly greater than the strength lost when the cover concrete spalls off. However, this equation does not directly consider ductile behavior, which is an important factor for the seismic behavior of bridge columns. Consequently, if the section area is relatively small or if the section area ratio becomes excessively large due to the concrete cover thickness increased for durability, too large an amount of transverse reinforcement, which could deteriorate the constructability and economy of piers, will be required. This study intends to analyze what effects the concrete cover thickness has on the equation for determining the confining transverse reinforcement amount.

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Development of the similitude law considering the intensity-dependent variation of natural frequency of pile foundation system (말뚝 기초 고유진동수의 가속도 크기 의존성을 고려한 상사법칙 개발)

  • Choi, Jung-In;Yoo, Min-Teak;Kim, Sung-Yul;Kim, Myoung-Mo
    • Proceedings of the Korean Geotechical Society Conference
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    • 2009.09a
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    • pp.905-912
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    • 2009
  • 1-g shaking table test is conducted to evaluate the dynamic behavior of a soil-structure system under seismic loading condition. A consistent similitude law between the model and prototype is needed to predict the behavior of the prototype structure, quantitatively. The natural frequency of geomaterial decreases with the increase of shaking intensity because of the non-linear property of the geomaterial. This phenomenon affects the applicability of similitude laws in 1-g shaking table tests. In this study, a simple method is suggested to determine the frequency of the input motions in 1-g tests in order to enhance the applicability of similitude laws. Modified input frequency is calculated using the frequency ratio with consideration of the variation of the natural frequency according to the intensity of input ground acceleration. To verify the applicability of the suggested method, a series of 1-g shaking table tests were performed for three different sizes of model piles having an overburden mass on their heads by varying the acceleration and the frequency of input motion. The acceleration amplification ratio on the overburden mass, the lateral displacement at the pile head and the maximum bending moment along the pile depth were measured. The projected behaviors of the virtual prototype based on the measured values of the model tests, where the input frequencies were calculated by the new method, showed good consistency, verifying the applicability of the suggested method.

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Cyclic tests on RC joints retrofitted with pre-stressed steel strips and bonded steel plates

  • Yu, Yunlong;Yang, Yong;Xue, Yicong;Wang, Niannian;Liu, Yaping
    • Structural Engineering and Mechanics
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    • v.75 no.6
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    • pp.675-684
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    • 2020
  • An innovative retrofit method using pre-stressed steel strips and externally-bonded steel plates was presented in this paper. With the aim of exploring the seismic performance of the retrofitted RC interior joints, four 1/2-scale retrofitted joint specimens together with one control specimen were designed and subjected to constant axial compression and cyclic loading, with the main test parameters being the volume of steel strips and the existence of externally-bonded steel plates. The damage mechanism, force-displacement hysteretic response, force-displacement envelop curve, energy dissipation and displacement ductility ratio were analyzed to investigate the cyclic behavior of the retrofitted joints. The test results indicated that all the test specimens suffered a typical shear failure at the joint core, and the application of externally-bonded steel plates and that of pre-stressed steel strips could effectively increase the lateral capacity and deformability of the deficient RC interior joints, respectively. The best cyclic behavior could be found in the deficient RC interior joint retrofitted using both externally-bonded steel plates and pre-stressed steel strips due to the increased lateral capacity, displacement ductility and energy dissipation. Finally, based on the test results and the softened strut and tie model, a theoretical model for determining the shear capacity of the retrofitted specimens was proposed and validated.

Seismic Behavior of H shaped Beam to Square Column Connection with Outer Diaphragm Using Field Welding (외측 다이아프램을 사용한 현장 용접형 각형강관기둥-H형강보 접합부의 이력거동)

  • Seo, Seong Yeon;Jung, Jin Ahn;Choi, Sung Mo;Kim, Sung Young
    • Journal of Korean Society of Steel Construction
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    • v.17 no.4 s.77
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    • pp.459-467
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    • 2005
  • This study focuses on the development of a new method of H-shaped beam-to-square column connection with an outer diaphragm and a field welding. The specific type of beam-to-column connection with an external stiffener, using field welding, is proposed. The structural behavior of this connection was examined experimentally. Two loading type tests were conducted under the experimental parameters given as details. First described was the symmetrical loading test, which supported both ends or a beam simply and applied a load from the column to the pend (What does this mean?) to investigate a fundamental characteristic of this connection. Further described was the anti-symmetrical loading test, which carried out simple support of the column'stop end and the column base, and applied a load from both ends of a beam to investigate the structural performance of this connection. From the results, it is clear that the external- stiffener-type connection proposed in this paper is the reliable connection method.