Concrete encased steel (CES) structures represent a new composite structural system consisting solely of fiber reinforced concrete and an embedded steel frame, in which the reinforced concrete portion of the steel reinforced concrete structure is replaced with fiber reinforced concrete. In March 2022, the Architectural Institute of Japan (AIJ) published “AIJ Guidelines for Structural Design of Concrete Encased Steel (CES) Buildings Based on Performance Evaluation Concept (Draft)” for the purpose of promoting the use of CES structures and disseminating appropriate CES design and construction methods. This paper presents an overview of these Guidelines.

High durability is required of concrete structures to achieve long-term service life as important infrastructures. The high durable structures by excellent related technologies also contribute to establishing a sustainable society with carbon neutral in the view of the global trend. The authors have been working on the development of a simple technique for evaluating the moisture penetration resistance of cover concrete in actual structures and its practical applications. With the technique, the water penetration resistance of hardened concrete can be directly inspected by the clients during the construction periods, and if necessary, the construction method can be reviewed and improved to achieve the construction of highly durable structures. This technical report presents an outline and practical examples of the water intentional spray test, which is a simple visual evaluation technique by watering.

Steel fiber reinforced concrete, which is concrete in which short steel fibers have been mixed, has been the object of much researches and developments over the years because of its ability to greatly improve mechanical properties. Experiments were conducted to verify the structural performance of short-span RC beams using specified design strength of 30-60 N/mm² class concrete mixed with 0.0～1.0％ steel fibers by volume, with hook-shaped anchorage at both ends, and the concrete mix proportions for improving workability during placing were investigated. This paper presents an overview of these two investigations and their findings.

Technology development to improve the productivity of rebar arrangement inspection, a longstanding issue in the construction industry, is actively being pursued, centering on the PRISM project of the Ministry of Land, Infrastructure, Transport and Tourism and field trials. To the same end, the authors have developed a three-lens camera rebar placement system that can be operated easily and quickly to perform rebar placement measurement and create reports. This system is the first of its kind in Japan to have been adopted for phased verification. The system has also been adopted by and is being routinely used by Hanshin Expressway Company Limited for the Komae Area Open-Cut Tunnel and other sites. This paper describes the system’s configuration and functions, the results of the verification of individual rebar spacing of newly conducted rebar arrangement, and the current average spacing measurement and rebar diameter determination accuracy. Finally, it discusses the applicability of this system not only in the field of civil engineering but also the construction sector.