In this study, rebound hammer test as non-destructive tests is modeled and incorporated into the visco-elasto-plastic suspension element method (VEPSEM). In addition, the distance which elements are constructed between nodals is changed in order to change the internal structure of the analytical model, the relationship between rebound number and compressive strength is investigated. As a result, it is shown that the analytical results of rebound number is correlated with the analytical result of compressive strength. This analytical relationship can be expressed the experimental relationship that the age of specimen and water cement ratio is changed.

This study proposes a method to simplify spatial correlation of ground-motion uncertainty in probabilistic seismic risk assessment for building portfolios. Portfolios were clustered using k-means, assuming perfect correlation within clusters and no correlation between clusters, allowing approximate representation without generating correlated normal random numbers. Seismic risk assessments for multiple portfolios in the Kanto region were compared with reference cases incorporating spatial correlation based on inter-building distances. The method produced comparable estimates, particularly when average intra-cluster distances were around 20 km. Combined with portfolio aggregation, it reduced computational cost while maintaining sufficient accuracy, indicating potential for application to larger portfolios.

Seismically isolated buildings are required to secure a safety margin against extreme ground motion. A possible countermeasure is to install a fail-safe mechanism in the seismic isolation layer. In this study, the fail-safe mechanism using bent steel plates is proposed, and the mechanical properties of the fail-safe mechanism are investigated by shear loading test and finite element analysis. Furthermore, the hysteresis model of the fail-safe mechanism is proposed, and the influence of hysteresis characteristics of the fail-safe mechanism on the seismic response of seismically isolated buildings is investigated by time history response analysis.

Damping elements exhibit temperature dependency. In this paper, it was demonstrated that the temperature dependency of damping elements including viscoelastic dampers, viscous dampers, oil dampers, steel dampers, high-damping rubber bearings, and lead rubber bearings can each be approximated by the Arrhenius equation. This enables the temperature dependency to be evaluated completely separately from other dynamic characteristics, and allows for comparison of temperature dependency among different damping elements using a single index.

This study proposes a suspension-type parallel link mechanism as a vertical seismic isolation system for buildings. Numerical analyses and shaking table experiments clarified its vertical dynamic characteristics. Results show the system reduces vertical acceleration responses when friction and damping are minimized, while maintaining stability under different loads. The parallel mechanism eliminates shear force transmission devices, offering advantages in cost and constructability. Verification through element and scaled model tests confirmed the analytical model’s validity and demonstrated the feasibility of applying this mechanism to three-dimensional seismic isolation.

The modal properties and the free vibration behavior accompanied with uplift motion are examined in vertical hybrid buildings with wooden upper part and RC lower part. Eigenvalue analysis is conducted to derive the uplifting modes. Using these modes, free vibration during an uplift excursion is simulated by modal analysis. In the hybrid buildings, it was clarified that the effective mass ratio for third- and fourth- modes and the base shear coefficients at the static equilibrium position become larger than those of a uniform structure, making it difficult to achieve the response reduction effect due to uplift.

This study proposes a simple prediction method to judge whether deck plates detachment and debris scattering occur in reinforced concrete slabs subjected to accidental falling-object impact during construction. The method targets a previously proposed anchorage system with a folded deck-plate edge embedded in concrete. Finite-element analysis of scaled impact tests showed that concrete and reinforcing bars dominated energy absorption, whereas the deck plate contributed only about 5%. A penetration-depth equation was derived from energy balance, and detachment was judged from the geometric relationship between penetration depth and deck-plate withdrawal. The method accurately predicted detachment without further experiments or numerical analysis.

This study investigates cast-in-place concrete piles constructed in Japan from the late Meiji to the early Showa period, with a particular focus on Pedestal Piles. The research aims to be clear their structural performance, including the strength of materials and their bearing capacity. The study involves examining the strength characteristics of rebar and concrete, analyzing the load–settlement behavior of these piles, and estimating their tip bearing capacity, in order to evaluate the load-bearing performance of pedestal piles.

This study presents an integrated method that combines deep-learning models and image-processing algorithms to detect cracks in RC member damage images while distinguishing crossings, discontinuities, and branches. Cracks are parameterized by a luminance-based polyline approximation; widths at approximation nodes are classified by a trained model, and lengths are measured from nodes. Damage images from full-scale RC partial-wall lateral-loading tests served for training and evaluation. The image-based lengths achieved an average ratio of 0.99 relative to manual measurements, and width classification accuracy was 0.88. Findings indicate crack segments with quantitative length and width attributes can be extracted.

This study proposes Pre-Twisted Steel Rib (PTSR) fabricated via cold twist-processing. Static loading tests and finite element analysis demonstrate that optimizing sectional parameters shifts plastic hinges away from member ends, expands yielding regions, and mitigates strain concentration. These mechanisms prevent premature cracking while enhancing plastic deformation capacity. The restoring force characteristics were clarified, and a theoretical model was proposed and validated through experimental and numerical verification. The PTSR configuration shows superior energy dissipation, providing a reliable solution for seismic-resistant structural systems.

It is necessary to mitigate damage concentration in specific stories against a large earthquake, and it is desirable to realize a global collapse mechanism. The author pursues a simple method to realize a global collapse mechanism. Specifically, a study is conducted on achieving a frame in which a global collapse mechanism is formed simultaneously with the elastic limit by introducing Beam-Joint-Plastic-Hinges. By realizing simultaneous yielding of all beams in a 2D frame, it is examined through time history response analysis whether uniform distribution of member damage can be expected.