Concrete Journal

The Guidelines for Design and Construction of Grouting for Prestressed Concrete Structures, established in 2005 by the Japan Prestressed Concrete Institute, have been revised for the first time in seven years. Among the major revisions are 1) the clarification of the necessary qualifications of engineers involved in PC grouting work, 2) the update of the materials used to the latest version, 3) the clarification of the positioning of full-scale tests, 4) the clarification of priorities regarding mixing, 5) the clarification of the period from after prestressing steel insertion to PC grout injection, 6) the reduction of the guaranteed material ages for the compressive strength test, and 7) changes to the frequency of routine control tests according to actual conditions.

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Not a few fire accidents in or on concrete structures such as tunnels, multipurpose ducts, and bridges, were reported, and various fire protection measures have being proposed. In many cases, the fires are caused by vehicles, and once damage is done, repairs take a long time and require significant expenses, posing a substantial burden on society. Rational fire-resistant design based on the fire behavior of concrete structures is required. The basic approaches to the fire resistance of concrete structures, the extent of damage upon occurrence of fires, and fire protection measures are described in this paper.

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The reinforced concrete rigid-frame viaducts of the Tokai Shinkansen experience significant vertical pile motion during train passage in some places and the presence of minor cracks in upper longitudinal beam haunches has been confirmed. While impact vibration and other tests have not detected problems in the base bearing capacity of these viaducts, the carbonation of concrete is progressing, raising concern as a potential cause of rebar corrosion. Against this backdrop, focusing on the vertical spring of the base of viaducts, the authors investigated a base reinforcement method for viaducts to improve the vertical spring of the base through the effective use of the vertical spring of the existing base, and carried out test construction and effect verification measurements. The authors confirmed improvement in the vertical spring of the base and reduction of vertical pile motion through viaduct base reinforcement, and developed specifications for viaduct base reinforcement.

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