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Inrak Choi - One of the best experts on this subject based on the ideXlab platform.

  • eccentric axial load capacity of high strength steel concrete composite columns of various sectional shapes
    Journal of Structural Engineering-asce, 2014
    Co-Authors: Honggun Park, Kyungsoo Chung, Inrak Choi
    Abstract:

    AbstractTwo concrete-filled steel tube columns and four concrete-encased steel columns using high-strength steel (yield strength fys=913, 806, and 812 MPa) and high-strength concrete (compressive strength fc′=94, 113, 104, and 184 MPa) were tested to investigate the effect of various sectional shapes and configurations on the eccentric axial load carrying capacity. This study focused on maximizing the contribution of the high-strength steel, preventing early Crushing of the concrete (1) by using steel tubes or closely spaced ties for lateral confinement, (2) by using ultra high-strength (200 MPa) concrete with a high-Crushing Strain, and (3) by placing L-shaped steel sections at the corners of the cross section. The test results showed that the steel tube successfully reStrained early concrete Crushing and developed its full plastic stress; unlike expectation, early Crushing occurred in the ultra high-strength concrete column; and the concrete-encased L-section column had higher peak strength and flexural...

Honggun Park - One of the best experts on this subject based on the ideXlab platform.

  • eccentric axial load capacity of high strength steel concrete composite columns of various sectional shapes
    Journal of Structural Engineering-asce, 2014
    Co-Authors: Honggun Park, Kyungsoo Chung, Inrak Choi
    Abstract:

    AbstractTwo concrete-filled steel tube columns and four concrete-encased steel columns using high-strength steel (yield strength fys=913, 806, and 812 MPa) and high-strength concrete (compressive strength fc′=94, 113, 104, and 184 MPa) were tested to investigate the effect of various sectional shapes and configurations on the eccentric axial load carrying capacity. This study focused on maximizing the contribution of the high-strength steel, preventing early Crushing of the concrete (1) by using steel tubes or closely spaced ties for lateral confinement, (2) by using ultra high-strength (200 MPa) concrete with a high-Crushing Strain, and (3) by placing L-shaped steel sections at the corners of the cross section. The test results showed that the steel tube successfully reStrained early concrete Crushing and developed its full plastic stress; unlike expectation, early Crushing occurred in the ultra high-strength concrete column; and the concrete-encased L-section column had higher peak strength and flexural...

Alajarmeh, Omar Saleh Awad - One of the best experts on this subject based on the ideXlab platform.

  • Compressive behavior of hollow concrete columns reinforced with GFRP bars
    2020
    Co-Authors: Alajarmeh, Omar Saleh Awad
    Abstract:

    Hollow concrete columns (HCCs) reinforced with steel bars have been employed extensively for bridge piers, ground piles, and utility poles because they offer higher structural efficiency compared to solid concrete columns with the same concrete area. Many experimental studies have been conducted to investigate the behavior of HCCs under different loading conditions and have found that the structural performance of HCCs is critically affected by the inner-to-outer diameter, reinforcement ratio, volumetric ratio, and concrete compressive strength. The improper design of the HCCs led to brittle failure behavior due to either buckling of the longitudinal bars or concrete wall Crushing. Moreover, the corrosion of steel bars in HCCs is a critical issue due to their inner and outer exposed surfaces. Therefore, this research systematically investigated the fundamental behavior of HCCs reinforced with GFRP bars in compression to develop new, durable and structurally reliable construction systems. Firstly, HCCs with different inner-to-outer diameter (i/o) ratios was investigated by testing four concrete columns 250 mm in external diameter and reinforced longitudinally with six 15.9 mm diameter GFRP bars with different inner diameters (0, 40, 65, and 90 mm). One HCC reinforced with steel bars was also prepared and tested as a control sample. Based on the experimental results, increasing the i/o ratio up to 0.36 changed the failure behavior from brittle to ductile. GFRP-reinforced HCCs exhibited higher deformation capacity and confinement efficiency compared to the GFRP-reinforced SCC and steel-reinforced HCC. The optimal (i/o) ratio was found at 0.36 as it resulted in the highest confined strength and ductility for GFRP-reinforced HCC. Similarly, reinforcing with longitudinal GFRP bars enhanced the overall behavior of HCCs. The effect of varying the reinforcement ratio was investigated as the second study. To study this parameter, six HCCs reinforced longitudinally with GFRP bars with different reinforcement ratios (1.78%, 1.86%, 2.67%, 2.79%, 3.72%, and 4.00%) were prepared and tested. These reinforcement ratios were achieved by changing the bar diameter (12.7 mm, 15.9 mm, and 19.1 mm) and number of bars (4, 6, 8, and 9 bars). The test results show that the increase in the bar diameter and number enhanced the strength, ductility and confinement efficiency of HCCs. For columns with equal reinforcement ratios, using a higher number and smaller diameter of GFRP bars yielded 12% higher confinement efficiency than in the columns with a lesser number and larger diameter of GFRP bars. The capacity of the GFRP-reinforced HCC can be reliably predicted by considering the contribution of the concrete and up to 3000 ue in the longitudinal reinforcement. The Crushing Strain of the GFRP bars embedded in the HCCs was 52.1% of the ultimate tensile Strain, and was affected by the confinement provided by the lateral reinforcements and the compressive strength of concrete. The effect of spiral spacing and concrete compressive strength was investigated as the third study. Seven large-scale HCCs with (i/o) ratio of 0.36, and reinforced with six longitudinal GFRP bars were prepared and tested. Out of these seven columns, three had spiral spacing of 50 mm, 100 mm, and 150 mm, and one had no spirals to investigate the effect of this design parameter. The fc of the other three columns were varied from 21 to 44 MPa to investigate the effect of the concrete compressive strength. Test results show that reducing the spiral spacing resulted in increasing the design load capacity, ductility, and confined strength of the HCCs due to the high lateral confinement. Increasing fc, on the other hand, increased the axial load capacity and reduced the ductility and confinement efficiency due to the brittle behavior of the high concrete compressive strength. The analytical model was then developed considering the contribution of the GFRP bars and the confined concrete core, which accurately predicted the post-loading behavior of the HCCs. The experimental results from the three experimental studies demonstrated that the (i/o) ratio, p, pv , and fc affect the overall behavior of GFRP-reinforced HCCs. Therefore, a new design-oriented model considering the effects of these design parameters was developed in the fourth study to accurately and reliably describe the behavior of the GFRP-reinforced HCCs. The new design-oriented model was based on the plasticity theory of concrete and considered the critical design parameters to precisely model the compressive load–Strain behavior of GFRP-reinforced HCCs under monotonic and concentric loading. The results demonstrated that the proposed design-oriented model was accurate and yielding a very good representation of the axial compressive load behavior of GFRP-reinforced hollow concrete columns. From the results of this research, a detailed understanding on how the critical design parameters affect the structural performance of GFRP-reinforced HCCs was gained. Moreover, the results from this research will provide useful information in revealing the many benefits of this new structurally efficient and non-corrosive construction system, which support the work of the technical committees engaged in the development of design provisions for GFRP-reinforced concrete columns

Elghazouli A.y. - One of the best experts on this subject based on the ideXlab platform.

  • Stress–Strain response and practical design expressions for FRP-confined recycled tyre rubber concrete
    'Elsevier BV', 2019
    Co-Authors: Bompa D.v, Elghazouli A.y.
    Abstract:

    This paper presents an experimental programme on the response of fibre reinforced polymer (FRP) confined circular rubberised concrete (RuC) members in compression. After describing the constituent materials and testing arrangement, a detailed account of the complete stress–Strain response of FRP-confined high strength conventional concrete materials (CCM) and RuC in uniaxial compression is provided. The parameters directly investigated through experimental assessment are the rubber content, namely 30% and 60% by volume of both fine and coarse aggregates, and the number of confinement layers which varies from 0 to 4. Experimental observations indicate that the confined compressive strength typically increases in a largely proportional manner with the unconfined compressive strength, whilst the confined axial Strain at ultimate tends to increase with the rubber content. Confined-to-unconfined strength ratios above 9 and confined ultimate Strain-to-unconfined Crushing Strain ratios above 40, are obtained for concrete with 60% rubber and four layers of confinement. These values are higher by factors of about 3.2 and 4.5 in comparison to the conventional reference concrete, respectively. The test results and observations enable the development of a series of design expressions to estimate the stress–Strain response of circular RuC specimens passively confined with FRP sheets, with due account for the influence of rubber content. Validations performed against the material tests carried out in this paper, as well as those from previous studies on RuC and CCM with FRP confinement, indicate that the proposed expressions offer reliable predictions of the mechanical properties of FRP-confined members

Ay Elghazouli - One of the best experts on this subject based on the ideXlab platform.

  • Stress-Strain response and practical design expressions for FRP-confined recycled tyre rubber concrete
    'Elsevier BV', 2019
    Co-Authors: Dv Bompa, Ay Elghazouli
    Abstract:

    This paper presents an experimental programme on the response of fibre reinforced polymer (FRP) confined circular rubberised concrete (RuC) members in compression. After describing the constituent materials and testing arrangement, a detailed account of the complete stress–Strain response of FRP-confined high strength conventional concrete materials (CCM) and RuC in uniaxial compression is provided. The parameters directly investigated through experimental assessment are the rubber content, namely 30% and 60% by volume of both fine and coarse aggregates, and the number of confinement layers which varies from 0 to 4. Experimental observations indicate that the confined compressive strength typically increases in a largely proportional manner with the unconfined compressive strength, whilst the confined axial Strain at ultimate tends to increase with the rubber content. Confined-to-unconfined strength ratios above 9 and confined ultimate Strain-to-unconfined Crushing Strain ratios above 40, are obtained for concrete with 60% rubber and four layers of confinement. These values are higher by factors of about 3.2 and 4.5 in comparison to the conventional reference concrete, respectively. The test results and observations enable the development of a series of design expressions to estimate the stress–Strain response of circular RuC specimens passively confined with FRP sheets, with due account for the influence of rubber content. Validations performed against the material tests carried out in this paper, as well as those from previous studies on RuC and CCM with FRP confinement, indicate that the proposed expressions offer reliable predictions of the mechanical properties of FRP-confined members