An expanded version of the “Seismic Performance Verification Guidelines for RC Underground Structures in Nuclear Power Plants” was published by the Japan Society of Civil Engineers in October 2021 for the purpose of advancing technology for the verification of the seismic performance of reinforced concrete underground structures. These guidelines systematically organize the latest knowledge on performance verification methods for underground structures, expanding on seismic response evaluation methods for structures in dense liquefied ground, raising the accuracy of the seismic performance verification method using 3D nonlinear analysis, and adding a new method for evaluating the effects of fault displacement. This paper outlines the expanded content of these guidelines.

The “Recommendations for Design, Construction and Maintenance of Post-installed Anchors in Concrete” established by the Japan Society of Civil Engineers in March 2014 were revised in February 2022 based on technological advances and accumulated knowledge. This paper describes the design, construction and maintenance of post-installed anchors, focusing on the basic concepts and key points of the revised recommendations.

In 2017, the authors applied the concrete with a specified strength of Fc300 N/mm² to an actual structure as the first third-party certified project of such kind in Japan. This kind of concrete with ultra-high-strength and high-performance was achieved by developing several related manufacturing technologies. Two types of silica fume and a developed admixture containing shrinkage-reducing agents were used to achieve flowability and strength. Multiple fibers were added to ensure fire resistance, and the mixing time was increased. Moreover, a two-stage curing scheme with high curing temperatures was applied. As the joint grout was required to have the same strength level, the heating curing using heating wires was developed. As for the structural characteristic of slender columns fabricated with such concrete, the bond of the main reinforcements at the ends was removed to alleviate the damage caused by large deformation during an earthquake, which retained the column’s ability to carry axial forces.

This study investigates whether the addition of lithium nitrite (LiNO₂) to cement-based adhesive used for post-installed anchors can fix anchors properly even at sub-zero temperatures. Anchor bars were fixed into concrete using this adhesive and cured in a thermo-hygrostat chamber at －5℃ to verify the bond strength. The LiNO₂ concentration of 14.3％ was found to give good performance in terms of compressive strength of the adhesive and bond strength of the anchor bars. Next, using adhesive containing LiNO₂, anchor bars were fixed outdoors in winter in Hokkaido, and anchor bar bond strength and shear strength tests were carried out. The anchor bars exhibited good bond strength and shear strength even when the adhesive was cured without warming in a cold environment with average temperatures of －10℃ and －5℃ to －7℃ on the day of anchor fixing and 7 days after anchor fixing, respectively.