The wappen-type exposure test is an exposure testing method that utilizes small and lightweight steel specimens and has primarily been used for assessing the condition of weathering steel bridges. This study summarizes the results of wappen-type exposure tests conducted on 51 bridges nationwide, presenting fundamental information on the trends, characteristics, and errors of the data obtained. Furthermore, taking into account the unique features of the wappen-type exposure test, we propose a simpler yet more accurate evaluation method as well as a standardized testing procedure.

 In this study, microtremor measurements were carried out using four to six velocity sensors arranged in a linear pattern on the tank wall to estimate the natural frequencies of the SUS panel tank’s bulging. Peaks possibly corresponding to bulging associated with the first and higher-order modes (defined as the second and higher modes) were observed in the microtremor spectrum. The peak frequencies and the spatial distribution of the peak values at these peak frequencies were generally consistent with the natural frequencies and natural mode shapes obtained through the eigenvalue analysis using FEM. The natural frequencies obtained from the microtremor measurements showed a negative correlation with the water level in the tank. The coefficient of determination of the regression equation using the natural frequency as the objective variable and the water level as the explanatory variable was as high as 0.9 or more. These results show the validity of the natural frequency estimates obtained from microtremor measurements. Finally, it was demonstrated that the natural mode shape along the lateral direction can be approximated by a sine function, and a sensor arrangement for microtremor measurement suitable for estimating the natural mode shape and natural frequency was proposed.

 Stainless steel is a high-performance alloy with superior corrosion resistance. The long-term durability of steel bridges can be improved by applying stainless steel to I-girder ends, which are subject to significant corrosion. Firstly, the distribution and magnitude of residual stress caused by dissimilar metal welding and assembly processes are experimentally investigated. Secondly, the shear load test and finite element analysis clarify the shear strength properties of steel I-girders welded with SUS821L1 and SM490Y. The validation of the finite element model is compared with the experimental results. Finally, the ultimate strength of I-girders welded with dissimilar metals under shear load is evaluated by the ultimate shear strength curve proposed in previous studies.

 Flexible barriers composed of nets and wires have been increasingly implemented as countermeasure structures in steep torrents. However, current design methods insufficiently account for the geomorphic conditions, the dynamics collision behavior of debris flows, and the deformation capacity of flexible barriers. As a result, design loads tend to be overestimated, while the buffering effects of deformation are underestimated, making rational performance evaluation difficult. This study experimentally investigates the differences in load transmission mechanisms between flexible and rigid structures and propose a new load evaluation model to rationalize the design of flexible barriers. Dynamic impact experiments simulating debris flow collisions revealed the buffering effect due to large net deformation, the temporal dispersion of load distribution, and the key factors causing overestimation in conventional design methods. The proposed model incorporates structural characteristics neglected in current practices, and is expected to advance performance-based design of debris-flow countermeasures in steep torrents by achieving both safety and rationality.

 This study aims to establish a residual axial force evaluation method for corrosion-induced thinning patterns of high-strength bolts occurring in actual bridges. Experiments were conducted on the thinning of nuts and bolt heads of high-strength bolts using electrochemical reactions. The experimental results indicate that the range of corrosion-induced thinning in the nut and bolt head that significantly affects the reduction in bolt axial force is 4 mm in height from the respective washer. Based on this, a method for evaluating residual axial forces is proposed.

 This study aims to analyze the regional variations in sediment disaster risk associated with climate change. Using 20-km mesh rain data from the d4PDF ensemble and a Radial Basis Function Network (RBFN), we compared the disaster risks in the Chugoku region under past and future climate conditions, assuming a 4°C increase in global mean surface temperature. The results revealed distinct regional differences and diverse trends among subareas. Moreover, both the frequency and spatial extent of heavy rainfall events are projected to increase in the future, suggesting the necessity of periodically revising the conventional warning and evacuation rainfall thresholds, as well as strengthening intermunicipal coordination and large-scale risk management frameworks.

 As autonomous buses are introduced, there is insufficient knowledge about how to evaluate and select vehicle exteriors, such as the color and shape of these buses. We created image designs for six types of autonomous buses: [Neutral], [Cute], [Weak], [Fast], [Futuristic], and [Strong]. A survey involving 1,500 participants was conducted to measure the impact of autonomous bus exteriors on social acceptance. The results show that attitudes "I like" and intentions to ride for autonomous vehicles were rated highest for the [Fast] and [Weak] designs. Regarding attitudes toward AVs such as "feel happy" and AVs behavioral intentions of take care like "watch over, " the [Cute] design received the highest evaluations. Furthermore, when participants were prompted to imagine specific scenarios where autonomous buses disrupted traffic flow, such as during congestion, the [Weak] design elicited the lowest level of irritation.

 In this study, we conducted a web-based questionnaire survey of 1,249 residents and visitors in the wards of Tokyo (Shibuya, Minato, and Meguro wards) in January 2024 to help make policy decisions regarding the diffusion of electric scooter (hereinafter referred to as “ES”) sharing in urban areas. The results showed that experienced users of ES-sharing behaved more dangerously on bicycles, an existing mobility device, than inexperienced users. Among those who have used ES-sharing, those who do not have a driver’s license were found to engage in risky behaviors. It was also revealed that the alternative modes of transportation for ES were mainly walking, car, and public transportation. Furthermore, the analysis of how people perceive ES from the viewpoints of pedestrians, bicyclists, and car drivers showed that car drivers, especially those who are not good at bicycling, are negative toward ES, while those who are good at bicycling, which is considered to be relatively similar to ES, are positive.

 This study focuses on Wider Economic Impacts (WEIs), the indirect spillover benefits of transportation infrastructure development. We theoretically analyze the relationship between city scale and the optimal evaluation of WEIs using an urban economic model that incorporates agglomeration economies, congestion externalities, and land input for transportation infrastructure supply. The analysis demonstrates that in large cities with high land prices, the cost of land acquisition for transportation infrastructure increases, which raises supply costs and consequently leads to more severe traffic congestion. Accounting for this mechanism, we examine a second-best environment where transportation charges are constrained to a uniform national level. The results reveal that because the marginal external cost of residence is higher in larger cities, the ratio of WEIs to time-saving benefits is higher for smaller cities.

 Social acceptance of autonomous vehicles (AVs), which have been developed in recent years, is an important factor in the social implementation of AVs. However, the indicators used in the surveys of social acceptance that have been conducted are different, making it difficult to compare them. In this study, we developed a prototype indicator to measure the social acceptance of AV buses, conducted surveys in areas where AV buses are actually operated autonomously, and conducted a comparative analysis between areas, and proposed a standard indicator based on the results of the survey and analysis. The survey targeted residents and users of AV buses in three areas in Japan where AV buses are being operated on a trial basis. A hierarchical multiple regression analysis based on a behavioral change process model showed a coefficient of determination of around 0.5, indicating a certain degree of usefulness of the proposed standard indicator. We also proposed actual operations, such as targets and survey plans for surveys using the standard indicators, and data analysis methods, along with examples of actual operations and analysis of survey results.

 In the Yamate district of Naka Ward, Yokohama City, Kanagawa Prefecture, there are numerous stone retaining walls referred to as “Bluff retaining walls.” These retaining walls have played a pivotal role in supporting the district’s development since the Meiji period, when the area was a foreign settlement. They have functioned as residential foundations and road retaining walls, contributing to the district’s infrastructure and the lives of its inhabitants. Despite the recent rise in momentum to preserve and utilize these retaining walls as historical and cultural resources of the district, they are currently being altered or removed as part of development projects without their value being fully recognized.

 In this study, first, the overview and history of bluff retaining walls were organized based on a literature review. Subsequently, their actual conditions were grasped based on a comprehensive survey. Based on these survey results, the historical and cultural value of bluff retaining walls was examined, and methods for evaluating their value were proposed. It is hypothesized that these research findings will contribute to the preservation and utilization of Bluff retaining walls in the future.

 This study was conducted to clarify the effects of lithium nitrite as a quality-improving agent on the compressive strength, shrinkage, and steel corrosion resistance of concrete with a high replacement ratio of ground granulated blast furnace slag (GGBFS). A series of tests were carried out, including compressive strength tests, drying shrinkage tests, accelerated carbonation tests, steel corrosion tests, and chemical analyses. As the amount of lithium nitrite added increased, improvements were observed in compressive strength, suppression of drying shrinkage and carbonation, as well as enhanced corrosion resistance. Furthermore, the addition of lithium nitrite was found to increase the amount of ettringite and promote the formation of nitrate-type hydrocalumite, suggesting that differences in the formation of hydration products due to the addition of lithium nitrite contribute to strength enhancement and shrinkage suppression. Additionally, the applicability of lithium nitrite to concrete was examined, confirming that the required slump and air content could be secured without issue, and that improvements in strength and shrinkage performance were achieved.