Concrete Journal
Online ISSN : 2186-2753
Print ISSN : 0387-1061
ISSN-L : 0387-1061
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Volume 53, Issue 3
Displaying 1-13 of 13 articles from this issue
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TOPICS
  • Publication of “Guidelines and Commentary for Seismic Evaluation of Concrete Block Garden Walls” by Architectural Institute of Japan
    I. Igarashi
    2015 Volume 53 Issue 3 Pages 253-259
    Published: 2015
    Released on J-STAGE: March 01, 2016
    DOIhttps://doi.org/10.3151/coj.53.253
    JOURNAL FREE ACCESS
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    Building sites in Japan are often enclosed with concrete block garden walls (hereinafter, “block walls”). In the majority of cases, building certification for such block walls is not applied for, and many such structures fail to comply with applicable laws and regulations and the block wall design standard of the Architectural Institute of Japan. As each time a major earthquake occurs, numerous existing block walls collapse, causing casualties, urban passers-by are constantly exposed to potential danger. Further, block walls that collapse on the road side will also obstruct traffic such as the passage of emergency vehicles during earthquake disasters. In light of the above, the Architectural Institute of Japan formed a “Working Group for Seismic Evaluation and Improvement Guidelines for Block Walls, etc.”(2010-2012), and based on the studies performed by that group, published the “Guidelines and Commentary for Seismic Evaluation of Concrete Block Walls” in March 2014. This paper outlines these guidelines.
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  • External Seismic Retrofitting Using Reduced-Shrinkage High-Flow Concrete
    H. Takeuchi, S. Tokita, T. Sakamoto
    2015 Volume 53 Issue 3 Pages 260-267
    Published: 2015
    Released on J-STAGE: March 01, 2016
    DOIhttps://doi.org/10.3151/coj.53.260
    JOURNAL FREE ACCESS
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    The traditional external seismic retrofitting method consists in integrating indirect joints consisting of reinforcing steel frames fitted with studs and post-construction anchors by filling them with high-flow grout material. However, in the case of indirect joints with a large section, use of grout material is problematic because of the high likelihood of insufficient performance in terms of junction strength and seismic behavior, as well as high cost. This paper introduces the application of reduced-shrinkage high-flow concrete to indirect joints in actual external seismic retrofitting projects.
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  • Development of Polymer and Natural Gas Pressure Welded Joint Technology
    H. Ishizuka, S. Miyaguchi, M. Teshigawara
    2015 Volume 53 Issue 3 Pages 268-274
    Published: 2015
    Released on J-STAGE: March 01, 2016
    DOIhttps://doi.org/10.3151/coj.53.268
    JOURNAL FREE ACCESS
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    The method presented in this paper is a new gas pressure welding technology for rebar bonding in the fields of civil engineering and building construction. It uses natural gas, which has less of an environmental impact than the traditionally used acetylene gas, as well as a polymer reducing agent (PS ring) that prevents oxidation of the rebar surface, a major cause of bonding defects. This construction method has the merits of having a low environmental impact through the use of natural gas, and offering the high reliability of gas pressure welding combined with corrosion prevention through the use of a reducing agent.
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  • Flexural Crack Behaviors of Partially Pre-stressed High Strength Concrete Beams
    Y. Tsuji, C. Li, K. Suhara, C. Hashimoto
    2015 Volume 53 Issue 3 Pages 275-282
    Published: 2015
    Released on J-STAGE: March 01, 2016
    DOIhttps://doi.org/10.3151/coj.53.275
    JOURNAL FREE ACCESS
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    While the bending cracks properties of RC beams and PC beams have already been reported numerously in relation to the effective use of high-strength concrete, few studies have been conducted on the effect of increasing the strength of concrete on the bending cracks properties of PPC beams. This paper reports the experimental results obtained by a study examining primarily the bending crack width of PPC beams using high-strength concrete through comparison with PPC beams using ordinary concrete, with the amount of tension reinforcement and the quality of the PC grout as the main factors. Among the main findings are the fact that even when high strength concrete is used, the effect of PC grout strength is small, the fact that a bending crack dispersion effect was not necessarily obtained in PPC beams with small tensile reinforcement ratio, and the fact that although bending crack width could be reduced in PPC beams with small tensile reinforcement ratio, almost no such reduction could be achieved in PPC beams with large tensile reinforcement ratio.
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