The two suppression mechanisms for Cs leaching, which contain fly ash (FA), are refinement effect on capillary pores and adsorption effect that are dependent on the mix proportion of FA. If the leaching suppression by the adsorption effect is expected, FA should be mixed with the cement matrix at a replacement ratio of approximately 70 mass% and the Ca/Si ratio in the C-S-H phase should be adjusted to approximately ≤1.0 (0.6–1.0). Meanwhile, if the leaching suppression by the refinement effect on a capillary pore is expected, FA should be mixed at a substitution ratio of approximately 30 mass%.

In this study, the effect of the modification level in the flotation method, using LOI as an indicator, on the properties of fly ash and mortar was investigated. As the modification level increased, the BET specific surface area of fly ash decreased, while the specific surface area increased. The particle size distribution also became more concentrated around 10-15 μm. Furthermore, a higher modification level improved mortar flowability, significantly reduced the amount of admixture required to achieve the target air content, and suppressed drying shrinkage. The highest compressive strength was observed at a modification level of Class2 (LOI 2%).

This study investigates the impact of carbonation curing on the shrinkage and creep properties of low-carbon emission concrete using γ-2CaO·SiO₂, based on Portland blast-furnace slag cement type C. Results indicate that carbonation curing with γ-2CaO·SiO₂ e exhibited increased compressive strength and calcium carbonate content. Although shrinkage increases during carbonation curing, it stabilizes afterward. Furthermore, carbonation effectively reduces the creep coefficients regardless of γ-2CaO·SiO₂.

This paper examines mix-proportions and the physical properties on the preformed cellular concrete with water cement ratio of 0.26 to 0.30. Using response surface methodology, we investigated mix-proportions that yield target compressive strengths ranging from 9 to 36 MPa and target densities ranging from 1.27 to 1.71 g/cm³ at minimal cost. Tests of cellular concrete with reference to the mix-proportions revealed that the static elastic modulus was lower than estimated, accelerated carbonation was different from that of normal concrete, and drying shrinkage was smaller than that of conventional cellular concrete but still larger than that of normal concrete.

This paper investigates the characteristics of dynamic soil springs in 31 high-rise reinforced concrete (RC) buildings with pile foundation and proposes simple evaluation equations. Using an axisymmetric finite element method (FEM), the dynamic soil springs at the bottom and lateral sides were analytically separated, and the effects of various parameters on their stiffness were examined. Based on the analysis, simple evaluation equations are proposed to estimate the stiffness of embedded pile foundation soil springs using a limited number of parameters. The proposed method demonstrates an error margin of approximately ±20%, indicating its validity and practical applicability.

After the 2024 Noto peninsula earthquake, we investigated the damage of tombstones at 350 sites in the wide area of Noto region and the western Toyama Prefecture. The overturning rate of tombstones was significantly high in Wajima, Suzu, Noto, Anamizu, Shika and Nanao. The rate generally decreases with the fault distance. Correlation between the overturning rate and the surface geology was relatively high. We established the fragility curve of the tombstone from the comparison between the overturning rate and the ground motion records and we then estimated the ground motion intensity during the 2024 Noto peninsula earthquake.

Dynamic loading tests were conducted on 1300φ lead rubber bearings using E-Isolation. FEM analysis calculated lead temperature changes using force and deformation data from these tests. We demonstrated that the relationship between yield stress and strain rate depends on temperature, and this follows the Arrhenius law. The activation energy of lead was determined, and yield force was formulated against lead temperature and strain rate. The derived equation matched well with existing experimental formulas and simulated well the experimental data.

We investigated the change in horizontal performance over 30 years in a seismically isolated building using natural rubber bearings, rubber bearings extracted from the building, and monitoring specimens, and found the following.

1. The horizontal load-deformation relationship and its aging change of the rubber bearings extracted from the building and the monitoring specimens matched well, regardless of whether or not they were loaded.

2. The change in stiffness of monitoring specimens over time was greater than the heat aging characteristics.

3. It is important to control the accelerated temperature in heat aging tests.

The vibration isolation floor using an inertial mass device developed by the authors is a floating floor structure with a clear load-deformation relationship, which enables an accurate evaluation of the excitation force of the audience’s vertical motion. Based on data obtained by measuring the vibration of a live hall floor for one year, we analyzed the excitation force of a hall floor for 1,000 people. By adjusting the inertia mass ratio considering the frequency dependence of the excitation force, the vibration isolation floor with an inertia mass device can significantly reduce the reaction force compared to a conventional floating floor.

A simple form finding analysis method for membrane structures is presented in this paper. Firstly, differential equations are formulated for uniform stress surface and for physical membrane surface subjected to sufficiently large negative temperature load. It is shown that the two sets of equations are approximately equivalent in the vicinity of the equilibrium state. Then an algorithm is proposed for form finding of uniform stress surface by repetition of temperature load analysis using general purpose FEA software. The validity of the method is shown in the examples of saddle-shaped membrane, pneumatic membrane and membrane with boundary cables.

This paper proposes a gravity-driven CLT rocking system with hardware commonly used in conventional Japanese houses as an alternative to high-ductile hardware in CLT panel construction. The system ensures no damage during moderate seismic events and relies on rocking restoring forces to prevent collapse during maximum considered earthquakes. Shaking table tests on full-scale, single-story CLT buildings evaluated this design concept. Results showed specific seismic behaviors such as shear force surges and compliance with the Japanese Building Code. Furthermore, the influence of two-dimensional excitation, the connections with walls, wall arrangements with eccentricity, and exterior wall followability were evaluated.

Currently, research and development are underway to realize CLT (Cross Laminated Timber) composed of laminae with varying thicknesses. In this paper, strength and probabilistic models focusing on the bending performance of CLT were examined. First, the CLT was tested in bending to identify the point at which the initial load drop occurred. Next, the correlation coefficients for the Young's modulus, bending strength, and tensile strength of the laminae were determined through testing. Finally, Monte Carlo simulations were employed to create virtual CLT, estimating this initial load drop point. Based on these results, the validity of the calculation method is reported.

Screw reinforcements are useful for timber members under compression perpendicular to the grain. This paper presents experimental results and evaluates three capacity methods and an initial stiffness method.

Specimens with six or more screws showed a 2.7 times increase in capacity and a 2.6 times increase in stiffness compared to those without screws.

Both capacity and stiffness generally improved with the number and length of screws.

The capacity methods of the authors or the authors with Aloisio et al.’s buckling were found to be useful. The initial stiffness method worked well for Japanese cedar but was underestimated for larch specimens.

The built-up H-shaped steel member is fabricated from three steel plates: two flanges and one web. Different steel grades may be used for the flanges and the web to fulfill design requirements. This study focuses on built-up steel members with a large width-to-thickness ratio and different tensile strengths at the flanges and the web. To clarify their tensile strength and deformation capacity, full-scale tensile tests and numerical analyses were conducted. Furthermore, a design method for evaluating yield tensile stress and yield strain of built-up H-shaped steel members with different flange and web strengths was proposed.

Building up cold-formed steel members using self-drilling screws is a common method for enhancing their load-carrying capacity. In this paper, we investigate the maximum strength of axially compressed built-up members in both the elastic and elasto-plastic ranges. We conducted axial compression tests and compared the experimental results with predictions from the proposed design equations. Our findings indicate that the maximum strength of a built-up member can be evaluated by adopting the smaller of the elastic flexural buckling stress and the elastic distortional buckling stress as the elastic global buckling stress used to calculate the column slenderness factor.