Concrete Journal
Online ISSN : 2186-2753
Print ISSN : 0387-1061
ISSN-L : 0387-1061
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Volume 53, Issue 8
Displaying 1-13 of 13 articles from this issue
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  • Establishment and Content of ISO 16311 Maintenance and Repair of Concrete Structures —Part 3 Design of repairs and prevention and Part 4 Execution of repairs and prevention—
    H. Watanabe, T. Nishiwaki, T. Kage, K. Takewaka
    2015 Volume 53 Issue 8 Pages 673-678
    Published: 2015
    Released on J-STAGE: August 01, 2016
    DOIhttps://doi.org/10.3151/coj.53.673
    JOURNAL FREE ACCESS
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    Following preceding papers providing an overview of Part 1 and Part 2 of ISO 16311 Maintenance and Repair of Concrete Structures, this paper gives an overview of Part 3 and Part 4 of this standard, which cover the design and execution of repairs and prevention. The overview of Part 3 is presented with particular focus on the various considerations up to the specification of remedies, and the classification of repair remedy principles, while the overview of Part 4 focuses on preparations, applied methods, and quality control as regards the execution of repairs and prevention.
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  • Revision of the “Recommendations for Practice of Quality Control in Concrete Work” of the Architectural Institute of Japan
    H. Tanano
    2015 Volume 53 Issue 8 Pages 679-684
    Published: 2015
    Released on J-STAGE: August 01, 2016
    DOIhttps://doi.org/10.3151/coj.53.679
    JOURNAL FREE ACCESS
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    The “Recommendations for Practice of Quality Control in Concrete Work” of the Architectural Institute of Japan have been revised after sixteen years. This was done against the backdrop of rapid changes in the environment for concrete quality since the year 2000, including revisions of related laws and standards such as the Building Standards Act and the Industrial Standardization Law, and the revision of various related technical data such as JASS 5. Concrete is now classified according to type and quality into JIS A 5308 compliant products and Minister of Land, Infrastructure and Transport approved products, based on Article 37 of the Building Standards Act. Further, a method that combines the use of acceptance inspections and specimens for testing structural concrete strength is also specified. Other specified content includes methods for the selection of ready-mixed concrete plants when factors such as drying shrinkage and Young's modulus are part of the design specifications, and methods for verifying concrete performance. In addition to the above, this paper discusses the major revision points and content of these latest revised “Recommendations for Practice of Quality Control in Concrete Work”.
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  • Development of Semi-Submersible Remotely Operated Vehicle for Inspection of Pier Superstructures
    T. Tanaka
    2015 Volume 53 Issue 8 Pages 685-689
    Published: 2015
    Released on J-STAGE: August 01, 2016
    DOIhttps://doi.org/10.3151/coj.53.685
    JOURNAL FREE ACCESS
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    The general inspection of pier superstructure concrete is done by visual inspection of the appearance of the beams and superstructure underside by workers on boats. However, such work is often made difficult by sea conditions such as tides and waves, and facility access restrictions due to mooring and cargo handling operations. To enable the safe and efficient inspection of pier superstructures, the authors developed a test model of a semi-submersible remotely operated vehicle (ROV) equipped with upward facing cameras. The ROV is designed for superior usability with operational support features such as an inspection position information management function and tele-operation assistance features that allow vehicle positioning and motion measurement under pier superstructures, where direct use of GPS signals is not possible. This paper introduces the work done by the authors on this invention.
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  • Residual Prestress Examination Methods
    K. Niitani, H. Watase, K. Hida
    2015 Volume 53 Issue 8 Pages 690-697
    Published: 2015
    Released on J-STAGE: August 01, 2016
    DOIhttps://doi.org/10.3151/coj.53.690
    JOURNAL FREE ACCESS
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    Prestressed concrete is concrete whose load-carrying capacity and durability have been enhanced by introducing prestress in concrete to overcome concrete's inherent weakness in tension. For this reason, prestress is the most important factor in prestressed concrete structures, and grasping the prestressed state of existing prestressed structures is extremely important for the maintenance of such structures. A number of methods for the examination of residual prestress have been developed and their practical application is progressing. This paper introduces some representative examples of these methods.
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  • Experimental Study on Safety of Bridge Deck using UFC
    T. Ichinomiya, S. Tarutani, H. Kanaji, T. Kosaka
    2015 Volume 53 Issue 8 Pages 698-702
    Published: 2015
    Released on J-STAGE: August 01, 2016
    DOIhttps://doi.org/10.3151/coj.53.698
    JOURNAL FREE ACCESS
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    In recent years, the occurrence in steel deck welds of fatigue cracks caused by deformation arising from vehicle travel has become conspicuous, and costs required for maintenance such as inspection and repair are rising. In response to this situation, the authors developed waffle-type slabs that use ultra high strength fiber reinforced concrete (UFC) for high durability and light weight on a par with that of steel slabs. Thus far, stress verification by FEM analysis and verification of safety against fatigue through wheel load running tests have been conducted. In the present study, load testing was performed on test specimens after subjecting them to the wheel load running test, for the purpose of identifying the failure mode and verifying safety in terms of fracture strength. As a result, the failure mode was identified as flexural failure, and the specimens were confirmed to have load-bearing capacity 7.5 times the design wheel load.
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