關西電力公司

Existing spillway piers constructed more than 60 years ago in Japan are usually reinforced with round rebars and have very low rebar ratios; consequently, their seismic response may be strongly influenced by post-cracking bond–slip. However, the applicability of nonlinear analytical models to such piers has not yet been systematically clarified. In this study, practical modeling strategies for existing spillway piers were investigated by performing Incremental Dynamic Analysis (IDA) using both a beam model based on nonlinear moment–curvature (M-φ) relationships and a 3D finite element analysis that explicitly accounts for bond–slip between concrete and rebar. An actual spillway pier was analyzed at multiple seismic intensity levels, and the effects of bar diameter, rebar ratio, and bond condition were examined via 3D finite element analysis. The results showed that the beam model is useful for global screening but may misclassify the damage mode because it cannot explicitly represent bond–slip. By contrast, the 3D finite element analysis reproduced flexure-dominant damage patterns and quantified the influence of bond–slip on maximum displacement, residual displacement, rebar strain, tensile damage distribution, and compression damage distribution. These differences became more pronounced under stronger ground motions and for larger bar diameters and lower rebar ratios. The findings support a staged strategy for seismic performance evaluation that combines beam models for global screening with 3D finite element analysis for detailed member-level assessment.

Renewable-electricity-powered hydrogen supply chains require compact, efficient, and demand-responsive NH3 crackers. Here we develop a microwave-driven ammonia decomposition system based on an LTA-type zeolite catalyst loaded with 10 wt% Ru nanoparticles that directly converts electrical energy into chemical energy through localized catalyst heating. The system achieves an external energy conversion efficiency of 48%, based on the net microwave input power after subtracting the reflected power. Thermal simulations further reveal an internal energy conversion efficiency of 60%, based on the microwave energy absorbed by the catalyst, independent of microwave frequency, corresponding to a hydrogen production efficiency of 92% on a lower heating value (LHV) basis. The reactor maintains high reaction rates while keeping the reactor wall at only 450 °C, enabling the use of conventional stainless steels. Multiphysics simulations combined with in situ synchrotron total scattering reveal that the dielectric properties of the zeolite support promote efficient power-to-chemical energy conversion by localizing electromagnetic energy within the catalyst. Fast start-up, rapid shutdown, and stable operation under fluctuating power demonstrate a compact and demand-responsive platform for decentralized hydrogen production compatible with renewable electricity.

Abstract In Japan, the disastrous effects of the 2011 Tohoku Earthquake has affected seismic design. Furthermore, there is an increasing need for dynamic nonlinear analysis that can consider large strain levels in assessing the seismic resilience of essential structures such as nuclear power plants. However, the applicability of dynamic nonlinear analysis methods to rock masses has not yet been fully evaluated. Their applicability needs to be confirmed by dynamic phenomena, such as shaking table tests. Herein, as a preliminary step, quasi-static analyses of cyclic direct shear tests were conducted to validate the constitutive model. Soft rock samples with relatively few fractures were used as the testing material. In the tests, the load was applied in multiple steps by increasing the loading amplitude at each step, with a loading frequency of 0.1 Hz. The quasi-static analyses revealed that, although an existing constitutive model generally reproduced the shear load–displacement relationship obtained in the tests from small displacement levels to peak strength, discrepancies emerged beyond peak strength. Therefore, we focused on the post-failure history damping characteristics of the soft rocks and added a damping constant after rock failure to the existing constitutive model. Consequently, the accuracy of the values of the stress history beyond peak strength was improved by more than 10%, and the reproducibility of the shear load–displacement relationship improved. Therefore, the applicability of the improved constitutive model was confirmed for conditions of quasi-static cyclic loading of soft rock with few fractures, from small displacement levels to beyond peak strength.