High performance fiber reinforced cement composites with multiple fine cracks (HPFRCC) have been extensively investigated in research community. JSCE has published recommendations for design and construction applying this material for the first time in the world. HPFRCC is known as metal-like cement material, characterized by pseudo strain hardening behavior and restricting ability of crack opening displacement. Applying this material is expected to achieve superior structural elements in terms of mechanical and durability performance. This article describes overview of these recommendations.

View full abstract

In 2006 September, Japanese Indusatrial Standard of Method of Measurement for Temperature of Fresh Concrete, JIS A 1156 was established. This standard is composed by Scope, Normative references, Apparatus, Sampling, Measuring the temperature of the sample, Measuring report, Annex (informative). This paper describes the outlines of established JIS A 1156, recommendable measurement of freshly mixed concrete and technical subjects in the future.

View full abstract

Fresh concrete generally contains bleeding water (free water) which is considered to deteriorate the quality of reinforced concrete structures. Therefore, it is very important to clarify the behavior of free water in evaluating the behavior of bleeding and segregation, and the quality of reinforced concrete structures. Main purpose of the present study is to examine the behavior of free water in fresh concrete and in various kinds of dewatered concrete. In this report, the behavior of free water in bleeding and the dewatered mechanism are discussed, based on series of newly proposed visualization tests on the permeable form dewatering, press dewatering and vacuum processing methods as well as the bleeding.

View full abstract

Recently, the revision of seismic design codes effective after the Hyogo-ken Nanbu earthquake have increased the amount of shear reinforcement for civil structures. Especially railway structures consequently require a large amount of reinforcing bars, leading to a decrease in the productivity of arrangement of reinforcing bars and filling capacity of concrete. The authors have developed the new construction method using deformed reinforcing bars with increased diameter at the bat ends, T-headed deformed bars as shear reinforcement of concrete instead of conventional hooked bars. This method has been successfully applied to many actual structures like Box culverts and LNG tanks. However, there are two issues in order to apply T-headed bars to railway structures. Therefore, the authors carried out two types of experiments: static shear tests of 4 rectangular beams with high shear reinforcement ratio; and fatigue tests of 8 rectangular beams using T-headed bars as shear reinforcement. As a result, it was verified that Theaded bars function sufficiently as shear reinforcement of RC members under both conditions.

View full abstract

RC structures under service that were designed by old earthquake codes are considered to be lack of the out of plane shear resistance or the ductility for the level II strong earthquake. Those RC structure should be strengthened to be failed with flexure mode not shear mode. The plate anchored bars called “Post-Head-bar” have been developed to reinforce the RC underground structure with working from inside only and to increase the ratio of shear bearing capacity to flexure capacity and to be flexible and ductile structures. In this paper, the reverse cyclic shear loading tests, the flexure toughness tests as well as pulling tests for anchored behavior of Post-Head-bar have been conducted to clarify the shear resistance mechanism and to find out the evaluation methods to calculate the qualitative shear resistance performance.

View full abstract

[in Japanese]

View full abstract

[in Japanese]

View full abstract