• Title/Summary/Keyword: reinforced columns

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Experimental Study of Ductility and Strength Enhancement for RC Columns Retrofitted with Several Types of Aramid Reinforcements (아라미드계 섬유 보강을 통한 RC기둥의 연성과 강도 증진에 대한 실험 연구)

  • Lee, Gayoon;Lee, Dong-Young;Park, Minsoo;Lee, Kihak
    • Journal of the Earthquake Engineering Society of Korea
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    • v.27 no.4
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    • pp.171-180
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    • 2023
  • This study proposed a seismic reinforcement of RC columns with non-seismic details, a fiber reinforcement method of aramid sheets and MLCP (high elasticity aromatic polyester fiber material) with different characteristics, and 4 full-size column specimens and conducted experiments. The results show that a non-seismic specimen (RC-Orig) rapidly lost its load-bearing capacity after reaching the maximum load, and shear failure occurred. The RC column reinforced with three types of aramid did not show an apparent increase in strength compared to the unreinforced specimen but showed a ductile behavior supporting the load while receiving a lateral displacement at least 1.57 to 1.95 times higher than the unreinforced specimen. The fracture mode of the specimen, according to the application of lateral load, also changed from shear to ductile fracture through aramid-based reinforcement. In addition, when examining the energy dissipation ability of the reinforced specimens, a ductile behavior dissipating seismic energy performed 4 times greater and more stably than the existing specimens.

Prediction of the Maximum Strain of Circular Concrete Columns Confined with Fiber Composites (섬유에 의하여 구속된 원형 콘크리트 기둥의 최대변형률 예측)

  • Lee, Jung-Yoon;Jeong, Hoon-Sik
    • Journal of the Korea Concrete Institute
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    • v.15 no.5
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    • pp.726-736
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    • 2003
  • Concrete columns confined with high-strength fiber composites can enhance its strength as well as maximum strain. In recent years, several equations have been developed to predict the behavior of the concrete columns confined with fiber composites. While the developed equations can predict the compressive strength of the confined columns with reasonable agreement, these equations are not successful in predicting the observed maximum strain of the columns. In this paper, a total of 61 test results is analysed to propose an equation to predict both compressive strength and maximum strain of concrete cylinders. The proposed equation takes into account the effects of confining pressure and cylinder size. Furthermore, in order to verify the proposed stress-strain curve for concrete cylinders, six cylindrical specimens were tested. Comparisons between the observed and calculated stress-strain curves of the tested cylinders showed reasonable agreement.

Settlement Behavior of Soft Ground Reinforced by Stone Columns (쇄석말뚝으로 보강된 연약지반의 침하거동)

  • Shin, Bang-Woong;Bae, Woo-Seok
    • Journal of the Korean GEO-environmental Society
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    • v.1 no.1
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    • pp.27-33
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    • 2000
  • Stone columns is ground improvement method which is composed of compacted gravel or crushed stone inserted into the soft ground consisting of loose sand and clay by replacement method. Generally stone columns are constructed in silty clay, above 70% replacement rate for increasing the bearing capacity and shear strength. Low replacement stone columns method is limited below 30% at replacement rate-premising strength increase of clay ground is estimated efficiently. This study, laboratory model tests were conducted to investigate the consolidation drainage promotion and shear strength increase effect in soft ground with replacement rate by stone columns. The settlement reduction effect and settlement reduction coefficients increase with increasing the replacement rate in composite ground. The results of model tests indicate that consolidation promotion effect is proved. The increasing strength of composite ground was verified by vane shear tests.

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The Flexural Behavior of a Circular Concrete Filled Carbon Tube Columns under the Constant Axial Force with Reversed Cyclic Lateral Load (축하중과 반복 횡하중을 받는 콘크리트 충진 원형 탄소섬유 튜브 기둥의 휨거동특성)

  • Hong, Won-Kee;Kim, Hee-Cheul;Chung, Jin-Hun
    • Journal of the Earthquake Engineering Society of Korea
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    • v.8 no.3
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    • pp.13-22
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    • 2004
  • The purpose of this study is to investigate the flexural behavior of circular concrete filled carbon tube(CFCT) columns subjected to constant axial load with the cyclic lateral load. Six numbers of composite columns were tested. Two parameters, winding angle and thickness of tube, were chosen to evaluate the flexural capacity and behavior of CFCT columns. Selected two parameters were considered simultaneously in order to evaluate the flexural behavior of CFCT columns more precisely. Flexural strength, deformation capacity, ductility and energy dissipation capacity of CFCT columns were evaluated by calculating the area of load-displacement envelop curves and load-displacement hysteresis curves obtained from experiment. Also, the ductile capacity obtained from experiment were compared to that of reinforced masonry wall for the comparison of existing structural element.

Effects of Tie Details on Seismic Performance of RC Columns Subjected to Low Compression Loads (낮은 압축력을 받는 철근콘크리트 기둥의 내진성능에 대한 띠철근 상세의 영향)

  • Kim, Chul Goo;Park, Hong Gun;Eom, Tae Sung;Kim, Tae Wan
    • Journal of the Earthquake Engineering Society of Korea
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    • v.19 no.4
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    • pp.195-205
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    • 2015
  • Various non-seismic tie details are frequently used for one- and two-story small buildings because the seismic demand on their deformation capacities is not relatively significant. To evaluate the effects of the non-seismic tie details on the seismic performance of reinforced concrete columns, six square columns with a cross section of $400{\times}400mm$ and six rectangular columns with a cross section of $250{\times}640mm$ were tested. The anchorage details at both ends and spacing of tie hoops, along with the cross-sectional shape and the magnitude of axial load, were considered as the primary test parameters. Test results showed that square columns had higher stiffness and lower lateral deformation rather than rectangular columns. Both lap spliced tie and U-shaped tie provided comparable or improved seismic performance to $90^{\circ}$ hook tie in terms of maximum strength, ductility, and energy dissipation. The predicted curves with modeling parameters in ASCE41-13 were conservative for test results of lap spliced tie and U-shaped tie specimens since plastic behavior after flexural yielding could not be considered. For economical design, ASCE41-13 should be revised with various test results of tie details.

Residual capacity assessment of post-damaged RC columns exposed to high strain rate loading

  • Abedini, Masoud;Zhang, Chunwei
    • Steel and Composite Structures
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    • v.45 no.3
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    • pp.389-408
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    • 2022
  • Residual capacity is defined as the load carrying capacity of an RC column after undergoing severe damage. Evaluation of residual capacity of RC columns is necessary to avoid damage initiation in RC structures. The central aspect of the current research is to propose an empirical formula to estimate the residual capacity of RC columns after undergoing severe damage. This formula facilitates decision making of whether a replacement or a repair of the damaged column is adequate for further use. Available literature mainly focused on the simulation of explosion loads by using simplified pressure time histories to develop residual capacity of RC columns and rarely simulated the actual explosive. Therefore, there is a gap in the literature concerning general relation between blast damage of columns with different explosive loading conditions for a reliable and quick evaluation of column behavior subjected to blast loading. In this paper, the Arbitrary Lagrangian Eulerian (ALE) technique is implemented to simulate high fidelity blast pressure propagations. LS-DYNA software is utilized to solve the finite element (FE) model. The FE model is validated against the practical blast tests, and outcomes are in good agreement with test results. Multivariate linear regression (MLR) method is utilized to derive an analytical formula. The analytical formula predicts the residual capacity of RC columns as functions of structural element parameters. Based on intensive numerical simulation data, it is found that column depth, longitudinal reinforcement ratio, concrete strength and column width have significant effects on the residual axial load carrying capacity of reinforced concrete column under blast loads. Increasing column depth and longitudinal reinforcement ratio that provides better confinement to concrete are very effective in the residual capacity of RC column subjected to blast loads. Data obtained with this study can broaden the knowledge of structural response to blast and improve FE models to simulate the blast performance of concrete structures.

Seismic performance of RC columns retrofitted using high-strength steel strips under high axial compression ratios

  • Yang, Yong;Hao, Ning;Xue, Yicong;Feng, Shiqiang;Yu, Yunlong;Zhang, Shuchen
    • Structural Engineering and Mechanics
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    • v.84 no.3
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    • pp.345-360
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    • 2022
  • In this paper, the impact on seismic performance of an economical effective technique for retrofitting reinforced concrete (RC) columns using high-strength steel strips under high axial compression ratios was presented. The experimental program included a series of cyclic loading tests on one nonretrofitted control specimen and three retrofitted specimens. The effects of the axial compression ratio and spacing of the steel strips on the cyclic behavior of the specimens were studied. Based on the test results, the failure modes, hysteretic characteristics, strength and stiffness degradation, displacement ductility, and energy dissipation capacity of the specimens were analyzed in-depth. The analysis showed that the transverse confinement provided by the high-strength steel strips could effectively delay and restrain diagonal crack development and improve the failure mode, which was flexural-shear failure controlled by flexural failure with better ductility. The specimens retrofitted using high-strength steel strips showed more satisfactory seismic performance than the control specimen. The seismic performance and deformation capacity of the retrofitted RC columns increased with decreasing axial compression ratio and steel strip spacing. Based on the test results, a hysteretic model for RC columns that considers the transverse confinement of high-strength steel strips was then established. The hysteretic model showed good agreement with the experimental results, which verified the effectiveness of the proposed hysteretic model. Therefore, the aforementioned analysis can be used for the design of retrofitted RC columns.

Axial Loading Behaviors of Square Concrete-Filled Tubular Columns with Large Width-to-Thickness Ratio Retrofitted using Carbon Fiber Reinforced Polymer Sheets(CFRP Sheets) (탄소섬유쉬트(CFRP Sheets)로 보강된 폭두께비가 큰 콘크리트 충전 각형강관 기둥의 중심축하중거동)

  • Park, Jai Woo;Yoo, Jung Han
    • Journal of Korean Society of Steel Construction
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    • v.26 no.3
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    • pp.169-176
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    • 2014
  • This paper presents the experimental results of behavior of square CFT columns with large the width-ro thickness ratio strengthened with carbon fiber reinforced polymers (CFRP) sheets subjected to concentrated axial loading. The main parameters were b/t ratio and the number of CFRP layers and 6 specimens were fabricated. The values of b/t were ranged from 60 to 100. From the tests, Maximum increase of 16% was also achieved in axial-load capacity with three transverse layered CFRP applied on four sides of steel tubes. The load capacity decreased up to 41% comparing with nominal load capacity of unstrengthened CFT column. However, for CFRP strengthened CFT, the load capacity decreased up to 32%. Finally, from the load-strain relationships, the local buckling occurred before yield point of steel tubes. Also, from the load-strain relationships, it was observed that local buckling were delayed on CFT columns by CFRP sheets retrofitting.

An Experimental Study on Structural Performance of SFRC filled Built-up Square Columns (강섬유 콘크리트가 충전된 용접조립 각형강관 기둥의 구조성능 실험연구)

  • Kim, Sun Hee;Yom, Kong Soo;Choi, Sung Mo
    • Journal of Korean Society of Steel Construction
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    • v.27 no.1
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    • pp.13-22
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    • 2015
  • This study suggests mixing steel fibers in concrete to secure the toughness of the columns. Therefore, to evaluate the structural behavior of welded built-up square columns filled with steel fiber reinforced concrete, ten stub column specimens were fabricated for compressive loading test with variables of steel fiber mixing ratio and loading condition. It is deduced that the steel fibers continue to provide tensile strength even after the concrete cracks and thus improve the strength and behavior of the column when bending moment is applied to it. A small amount of steel fibers can improve compressive strength and bending strength and thus produce economically efficient results when employed in structural design.

Spalling Reduction Method of High Strength Reinforced Concrete Columns Using Fibers (섬유를 활용한 고강도 콘크리트기둥의 폭렬제어방안)

  • Yoo, Suk-Hyeong
    • Fire Science and Engineering
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    • v.23 no.4
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    • pp.7-12
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    • 2009
  • As the concrete strength increases the degree of damage caused by the spalling becomes more serious because of the permeability. It is reported that the polypropylene (PP) fiber has an important role in protecting concrete from spalling. However, the excessive usage of PP fiber would not useful in spalling control and would decrease the workability of ultra high strength concrete. The high-temperature behaviors of high-strength reinforced concrete columns with various dosage of PP fibers and three types of fire endurance fibers were observed this study. In results, the ratio of unstressed residual strength of columns, in case of concrete strength 60MPa, increases as the dosage of PP fiber increases from 0% to 0.2%, however, the effect of fiber dosage on residual strength of column barely changes above 0.2% and in case of concrete strength 120MPa, PVA fiber is the most suitable fire endurance fiber in accounting fire endurance performance and workability.