Fatigue cracks caused by vortex-induced vibration have been observed in slotted tubular joints of transmission steel tower members. However, no general method is currently available to evaluate cumulative fatigue damage ratios considering local wind environments and member properties. In this study, a fatigue evaluation method was developed using wind speed frequency distributions derived from a regional climate model and nominal stress range frequency distributions obtained through time-history response analysis. The validity of the method was confirmed by field stress measurements of steel tubular members and comparisons with actual fatigue crack cases. Furthermore, fatigue evaluations under various wind and member conditions revealed that slenderness ratio of a member with high cumulative fatigue damage ratio was limited to a specific range, and that the cumulative fatigue damage ratio was correlated with the diameterto-thickness ratio. In addition, it was shown that threshold values of slenderness ratio and diameter-to thickness ratio, such that the cumulative fatigue damage ratio exceeds 1.0, can be estimated based on factors such as tower locations and member support conditions.

 This study investigates simplified estimation methods for local stress (notch stress) for the fatigue assessment of fillet welds in out-of-plane gusset plate connections with partial penetration, focusing on both the weld toe and weld root. Existing fatigue test data were reviewed to examine whether notch stress enables a unified evaluation of crack initiation life at the weld toe and weld root and whether the crack initiation location can be inferred from the relative magnitude of notch stress. Simplified notch stress estimation methods were developed based on parameters derived from member geometry, weld geometry, and stress gradients. For the estimation of weld root notch stress, an additional method utilizing reference stress was also developed. Finite element analysis of a full-scale bridge model was conducted to verify the applicability of the proposed estimation methods to actual bridge structures. The results show that the notch stress range enables a unified evaluation of crack initiation life regardless of joint type and crack initiation location. The proposed notch stress estimation methods show a strong correlation with finite element analysis results and provide sufficient accuracy for practical applications, even when applied to a full-scale bridge model.

 In order to calculate the rate of cement hydration reaction during curing and estimate unconfined compressive strength of cement-treated clay using the volumetric ratio between cement hydration and soil void, thermogravimetry differential thermal analysis and powder X-ray diffraction analysis were conducted to quantify the amount of cement hydration products in the cement-treated clay, The conclusions are summarized as follows (1) The total mass fraction of cement hydration products in the cement-treated clay with the cement content of 10 % increases by 31.6 % at 91 days of curing. (2) The rate of cement hydration reaction in the cement-treated clay with the cement content of 10 % and 50 % were slightly slower than that of the cement paste, reaching 51% and 58 % at 91 days of curing, respectively. (3) An equation is proposed using the volumetric ratio between cement hydration and soil void to estimate the unconfined compressive strength for the cement-treated clay, which can be applicable to a wide range of strength from low strength (less than 1 MPa) to high strength (equivalent to 15 MPa).

 Seismic reinforcement of leaning-type retaining walls, which have suffered significant damage, such as overturning, in past earthquakes, is achieved using the soil-nail reinforcement method. It involves installing multiple soil nails. However, in current practice, only the resistance provided by the surrounding friction of the soil nails is considered towards their reinforcement effect. This is because the mechanism of resistance-force generation by the deformation of the soil nails corresponding to wall tilting and sliding remains unclear. Therefore, this study conducted a series of static-loading and shaking table tests using 1/10 scale models of leaning-type retaining walls before and after reinforcement, focusing on the deformation of the soil nails. The results revealed that bending moments occurred in the soil nails due to wall tilting, which served as resisting moments on the wall. Furthermore, a shaking table test using soil nails with large bending stiffness and an analytical study using Newmark’s method were performed to investigate the influence of the resisting moments on seismic displacement. Next, a seismic-displacement evaluation method was proposed based on elastic support-beam theory and Newmark’s method. Finally, a trial analysis using the proposed method was performed on damage cases of leaning-type retaining walls from the 1995 Hyogo ken-Nanbu earthquake to verify the effect of the resisting moments due to soil-nail deformation on seismic-reinforcement effectiveness.

 The authors have developed the “Vein-Type Ground Improvement Method, ” which aims to densify liquefiable ground and enhance its liquefaction resistance. This paper reports the results of a field trial conducted to examine the applicability of the method to Diluvial sand layers, for which no prior application had been made. For application to diluvial layers, lower injection ratios than those used for alluvial layers were assumed, and the injection ratio was adjusted by varying the spacing between injection points while keeping the injection volume at each point constant.

 The field trial confirmed that the application of this method to diluvial layers increased the N-value and the coefficient of earth pressure at rest (K₀), although the improvement was not as pronounced as that observed in alluvial layers. Nevertheless, the results demonstrated that even a relatively small improvement is sufficient to meet required performance levels, and that a rational design injection ratio can be established by understanding the relationships among injection ratio, effective injection ratio, and K₀ obtained from the trial.

 Tensile cracks are frequently observed in earthquake-induced embankment failures; however, the conventional Newmark method considers only shear failure. This study proposes a modified Newmark method that incorporates the effects of tensile cracks. Parametric analyses of 198 cases revealed that considering cracks increases the predicted maximum residual displacement. In some cases, displacements evaluated by the conventional method satisfied seismic performance limits, whereas those obtained using the proposed method exceeded them. These results indicate that the conventional method may underestimate seismic risk when tensile cracks develop.

 This study classified Green Infrastructure (GI) into stormwater management-oriented GI (SM GI) and ecosystem conservation-oriented GI (EC GI), and clarified the consensus-building process of GI-based Comprehensive Flood Control through public-private collaboration, with attention to areas inside and outside river zones, using the Mama River basin in suburban Tokyo as a case study. Three findings were identified: (1) although planning for SM GI temporarily stagnated due to conflicts over river improvement projects, the citizen-proposed Water-Defence Urban Concept (WDUC) promoted public-private collaboration for SM GI outside river zones; (2) consensus on EC GI within river zones was achieved through shared development concepts and continuous dialogue between public and private stakeholders; and (3) the WDUC, which subdivides residential areas into small catchments, contributed to flood risk dispersion and facilitated public-private collaboration related to GI and the principle of River Basin Disaster Resilience and Sustainability by All.

 This study focuses on the urban planning theories by Toshikata Sano, Toshiro Kasahara, and Shigeyoshi Fukuda, who were responsible for drafting and passing the old City Planning Law and Urban Building Law. The similarities and differences among the three men were clarified as follows. The three men were mainly identified the shortage of housing, the density of building and people, and the size of building lots as urban problems. The solutions to urban problems included establishing zoning districts, unifying blcks, plots, and housing standards, introducing local planning, and building appropriate facilities to address the problems, as well as drawing and designing tangible plans. In terms of finances, plans for mass production of housing at low cost and specific budgets were established and planned. Regarding transportation, the construction of new railroads and roads was considered in conjunction with the creation of residential areas. Comparing the three, Toshikata Sano differed from the other two in that he did not see urban expansion as an urban problem. Also, compared to the other two, Toshiro Kasahara considered urban planning based on the zoning system. Shigeyoshi Fukuda was trying to shape the city with an emphasis on transportation planning. The results of the analysis show that the three men differed in their perceptions of urban expansion and in the scale of their solutions. However, architect’s theories of urban planning primarily focused on the layout of urban facilities and sought to formulate concreate urban plans by comprehensively examining a variety of factors, such as housing issues, building codes, transportation, and finance.

 This study attempted to estimate the felling dates of four cypress wood piles, believed to be the remains of bridge piers buried in the right-bank riverbed of the Yahagi River in Yahagi-cho, Okazaki City, Aichi Prefecture, Japan. Yahagi Bridge is known as the longest bridge in Japan during the Edo period (1603–1868 CE) and believed to have been first constructed around 1601 CE (Keichō 6) according to historical documents and maps. However, some descriptions in chronicles or tales such as “Taiheiki” and “Heike Monogatari” suggest a bridge existed in the medieval period before the 16th century. Tree ring oxygen isotope dating revealed that three of the four piles were felled in the late Heian to Kamakura periods (late 12th to early 14th centuries), while the fourth may date back approximately 100 years earlier. These findings suggest that the medieval Yahagi Bridge, previously known only through tales and folklore, actually existed for at least a period around the 12th to 13th centuries.

 This study measured the time-series trends in economic damage caused by worker commuting disruptions, raw material procurement disruptions, and product shipment disruptions due to transportation disruptions during wind and flood disasters, using a production function approach. Focusing on the July 2018 torrential rains, it distinguishes itself by clarifying the time-series trends in economic damage by region and industry. This was achieved by considering the time-series trends in actual road and railway disruptions, as well as product inventory rates by region and industry. Furthermore, as a scenario analysis, it measured the difference in economic damage amounts under two hypothetical conditions: if the Higashi-Hiroshima Kure Expressway (which remained operational during the disaster) had failed, and if the Hiroshima Kure Road (which was disrupted during the disaster) had remained operational. This measured the effectiveness of disaster prevention investments in infrastructure.

 When the foundation of a gravity concrete dam contains weak layers dipping gently in the upstream–downstream direction, the stability of the dam against sliding can be significantly affected. To enhance the shear resistance of the foundation rock, part of the weak layers can be removed and replaced with shear keys. In this study, the influence of shear keys on the rock foundation was evaluated through wedge stability analysis and finite element stress–deformation analysis, and the appropriate scale and layout of the shear keys were determined. Furthermore, the dam behavior and rock response after impoundment were investigated through monitoring by such as reverse plumb lines, drilling core observations, and Computed Tomography scanning image analysis. The analyses revealed that installing shear keys reduced compressive stresses and relative displacements in the rock mass near the dam toe, thereby improving the local safety factor. Post-impoundment observations also confirmed that no signs of shear failure or deformation were detected in or around the weak layers.

 This study formalizes the technical judgments of experienced engineers in determining maintenance actions during road bridge inspections as a logical model based on the hypothetico-deductive method, and verifies its applicability. Semi-structured interviews were conducted with 14 skilled bridge inspectors, and their statements were segmented and categorized into four propositions: grounds, warrants, conclusions, and action policies. Furthermore, natural language processing was employed to statistically analyze semantic similarities among propositions and to evaluate the reasoning process both qualitatively and quantitatively. The results demonstrated that the technical judgments of experienced engineers can be explained by a hypothesis-based reasoning model, and empirically revealed that cognitive biases and differences in knowledge can impede logical reasoning. This study presents a novel theoretical framework that scientifically visualizes reasoning processes involving tacit knowledge, contributing to knowledge transfer and the advancement of AI-assisted inspection and diagnostic support systems.

 The use of eDNA has enabled the comprehensive understanding of Ayu dynamics at a watershed scale, which was previously challenging with conventional capture-based surveys. In this study, we analyzed the concentration and flux of eDNA to elucidate the spatiotemporal dynamics of Ayu in the Tama River system across its life cycle in 2017 (settlement, downstream migration, and spawning period) and 2018 (upstream migration and settlement period).

 Time-series analysis of the longitudinal eDNA distribution revealed fish dynamics that align well with the life history of Ayu, including upstream/downstream migration and spawning, and showed that their distribution fluctuates even during the settlement period. In addition, a comparison between the main river and its tributaries suggested that tributaries not only expand the habitat range of Ayu and increase its environmental capacity, but also function refuges during high-flow events. Furthermore, the timing of downstream migration in the tributaries was found to lag behind that of the main river, which may extend the overall spawning period and ultimately contribute to maintaining the Ayu population.

 The purposes of this paper are (i) to investigate the factors contributing to dual habitation and (ii) to examine whether there is a difference in the degree of pro-environmental behavior between people interested in dual habitation and those who are not. Using questionnaire data, this study employed ordered probit regression analysis and non-parametric statistical tests. We have obtained three interesting findings. First, older, married individuals with stable employment are more likely to consider or engage in dual habitation. Furthermore, people who value human relationships within their community and those with more nature experiences in childhood are also more inclined to consider or practice dual habitation. Second, people interested in dual habitation show more pro-environmental behavior regarding waste, energy/resources, and car usage than those who have never considered it. Third, while people practicing dual habitation have a high level of interest and awareness regarding environmental issues, their engagement in pro-environmental behavior is not necessarily higher.

 In this study, a work analysis of the maintenance and legal inspection of Johkasou was conducted, considering the required working time and the reduction of greenhouse gas (GHGs) emissions. Regarding the working time, the maintenance per unit took 41.3 minutes, with 11.6 units of an implementation ratio per day; the legal inspection per unit took 43.5 minutes, with 11.0 units of an implementation ratio per day. The analysis also suggested that the required time for the maintenance and the legal inspection was reduced to 81.9% and 75.0% by the improvements in the driving route and the digitization of the operations. It was suggested that increase in 11% of the number of the maintenance operators and to 51% of the number of inspectors was required to improve the implementation ratio of maintenance and legal inspections to 100% not just streamlining. The driving route analysis implied that the improvements in the route reduced GHGs emissions by 36.4%. For further reduction in the required time and GHGs emissions, it might be useful to switch multiple individual Johkasou into a community-type Johkasou in case of the replacement of the old Johkasou.