Utilizing timber through sustainable forest management is an effective measure against climate change. However, in Japan, the rate of reforestation remains low, partly due to the stagnant prices of B-grade and C-grade timber. Creating new demand for these types of timber can be considered one effective strategy to promote reforestation. The authors propose a new liquefaction countermeasure method utilizing these timber materials and conducted needle penetration tests and 1G small-scale shaking table tests to understand qualitative trends in liquefaction mitigation. The results showed that although there was some variability, the penetration resistance increased with the installation of timber bundles, and the amount of increase was greater when the spacing between the timber bundles was smaller. Furthermore, the input acceleration at the onset of settlement of the structural model increased due to the installation of timber bundles, and this input acceleration was greater with smaller spacing between the bundles. It was also revealed that the settlement reduction effect of the ground with installed timber bundles exceeded the effect of increased density alone.

 The Bandal-type groyne is a traditional wooden hydraulic structure characterized by an impermeable upper section and a permeable lower section. It has long been used in South Asian countries, primarily for improving navigation channels, and in recent years it has attracted attention for its potential applications in riverbank protection and new landforms creation. However, a major drawback of this structure is its susceptibility to being washed away during floods, which has prompted the need for improvements in its design. This study examines modifications to the Bandal-type groyne and experimentally evaluates its hydraulic functions and adaptability. The results demonstrated that the improved groyne exhibited hydraulic characteristics similar to those of the original Bandal-type groyne. The hydraulic performance varied depending on the sheet conditions applied to the structure.Moreover, the adaptability of the structure was observed. Regardless of the presence or arrangement of sheets, the groyne adjusted its posture in response to surrounding bed deformation and maintained stability without being displaced by the flow. The inclination angles in different directions showed distinct tendencies depending on the sheet conditions, indicating that structural modifications influence not only hydraulic performance but also deformation behavior.These findings highlight the potential of the improved Bandal-type groyne as a sustainable river engineering measure that preserves the traditional functions of the original structure while enhancing resilience to flood conditions. The study contributes to the ongoing efforts to adapt traditional wooden river training techniques to contemporary river management needs, particularly in regions where locally available materials and low-cost construction methods are essential.

 In medium- and large-scale buildings and civil engineering structures, long-span members are required. However, because the length of timber is limited, longitudinal joints are necessary. The joint performance of beam using longitudinal drift pinned joints has not been sufficiently evaluated. This study aimed to clarify following two points: (1) whether existing formulas for yield moment and rotational stiffness can be applied to longitudinal drift pinned joints, and (2) how the ratio of main member thickness to drift pin diameter (l/d) influences the likelihood of brittle fracture. Specimens were prepared under four conditions by varying l/d and the arrangement of drift pins, and four-point bending tests were conducted for each specimen. The results demonstrated that the yield moment was approximately twice the calculated value, while the rotational stiffness also tended to be larger than the calculated value due to compressive stresses caused by the indentation of the cross section at the joint. When the compressive stress was considered, the estimated yield moment closely approximated the experimental results. It was also found that larger l/d increased the likelihood of brittle fracture. However, the arrangement of drift pins had a greater influence on the likelihood of brittle fracture than variations in l/d.

 Timber bridges constructed with Bongossi (Ekki) are prone to internal decay in Japan’s hot and humid climate, increasing the risk of collapse with age. Accordingly, this study targeted the Bongossi timber pedestrian “Midori Bridge,” which has been in service for about 30 years, and conducted field vibration tests to characterize its structural properties. The measured natural frequencies were used to estimate the current bending stiffness of the entire bridge, and the inferred stiffness reduction was compared with those of bridges that had previously been replaced to discuss the timing of replacement for Midori Bridge. Pedestrian vibration serviceability was also evaluated based on velocity responses during walking. The results show that the overall bending stiffness has decreased by approximately 60% relative to the as-built condition, indicating that the bridge is at a stage where replacement (or major rehabilitation) should be considered. In addition, under crowd-walking conditions, the response falls into the category “Extremely hard to walk,” indicating a marked deterioration in vibration serviceability.

 Cross-laminated timber (CLT) is a large-surface material. In recent years, by utilizing its property of reducing the influence of timber’s anisotropy, CLT has been utilized to civil engineering structures. CLT is manufactured by bonding layers of laminas together. However, cases of poor bonding have been reported between laminas and at finger joints. And the effects of poor bond are not well evaluated for mechanical characteristics of CLT. In this study, we apply a poor bonding condition and investigate the CLT's displacement and stress changes using numerical analysis. As a result, the displacement and stress of CLT with poor bond are increased overall. In particular, the value increased when there is poor bond at the finger joint and the outer lamina of the 5th layer.

 The presence and extent of damage to wooden civil engineering structures in the area damaged by the 2024 Noto Peninsula earthquake and the 2024 Oku-noto torrential rain were confirmed through interviews and field surveys. As a result, slope collapse and serious damage were observed in some areas, but most of the wooden structures maintained their original functions and no serious damage was observed. In addition, no damage was observed in the areas where wooden piles were used, although there was some damage such as ground subsidence.

 The Tsuru-no-mai Bridge, spanning the agricultural reservoir (Tsugaru Fujimi Lake) in Tsuruta Town, Aomori Prefecture, is a 300-meter-long wooden pedestrian bridge completed in 1994, constructed using Aomori cypress. The Tsuru-no-mai Bridge is a tourist attraction in Tsuruta Town, and an annual structural integrity survey is conducted to collect data necessary for its maintenance and management. Approximately 30 years after its construction, the Tsuru-no-mai Bridge underwent superstructure renovation work over a three-year period starting in fiscal year 2023. In fiscal year 2023, work was performed on the 100-meter section of the first span. In fiscal year 2024, work was performed on the 100-meter section of the second span and the small stage. In fiscal year 2024, a condition survey and strength tests were conducted on the bridge girders that were removed during the renovation work.