Periodic monitoring of the rust condition is necessary for the maintenance of weathering steel bridges. In recent years, some studies have been conducted to simplify and quantify the rust condition rating method. In this study, a rating technique that combines the optical spectra in visible light and near-infrared of a weathering steel surface with a supervised learning classifier was proposed. First, the optical spectra of weathering steel surfaces in different rust conditions were measured every 1 cm square, and four wavelengths (wavelengths of 569 nm, 694 nm, 796 nm and 896 nm) were selected from the first derivative of the measured optical spectra as characteristic wavelengths for rating the rust condition. The first and second principal components were extracted by applying kernel principal component analysis to the reflection intensities at the characteristic wavelengths, and random forest classifier was constructed. As a result, accuracy was 90.7 %.

 This study intends to propose stochastic methods for real-time scour assessment of a railway bridge pier during swollen river water periods using microtremors from accelerometers deployed on top of it. When the natural frequencies of the pier are identified using ambient microtremors, there is a large variation in the identification due to uncertainty. This study, thus, proposes three scour-warning indicators derived from cumulative density function, marginal probability distribution, and logistic function modeled by Levy Flight Distribution at a normal condition. They are applied to the observed data at a swollen river water period, and it is demonstrated that the probability of scour progress is low. Furthermore, the validity of indicators using observations that pseudo-replicated acceleration waveform during scour progress is figured out considering changes in indicators.

 The newly developed multi-CFT column piers, equipped with shear dampers, have been experimentally proven to exhibit excellent seismic robustness against ground motions surpassing Level 2 earthquakes. Consequently, utilizing these multi-CFT column piers appropriately is expected to enhance the resilience of elevated-girder bridges during ultra mega earthquakes. To achieve this, it is crucial to develop a practical model capable of assessing the hysteretic behavior of CFT columns, including significant local buckling deformations, and incorporating it into the seismic analysis of the entire elevated-girder bridge system. However, the multi-CFT column pier model based on shell-solid elements encounters challenges in obtaining convergent solutions due to the complex interaction among multiple CFT columns. The objective of the present research is to propose a practical and numerically stable segment model that can be inserted into the lower part of each fiber-based CFT column model to accurately depict its local buckling behavior. This segment model comprises computationally stable elements such as nonlinear beam elements, elastic solid elements, and contact spring elements. Numerical calibration of the numerous internal parameters of the elements within the segment model is performed using an optimization technique. The aim is to ensure that the segment model effectively represents the cyclic in-plane local buckling behavior of a single CFT column segment, as calculated through shell-solid element model analysis. The accuracy and computational efficiency of the fiber-based multi-CFT column pier model, with segment models inserted at the local buckling section of the CFT columns, were extensively evaluated using results from one-directional cyclic loading tests and spiral loading tests conducted on 1/10 scale models of multi-CFT column piers.

 Numerical simulation of tsunami-induced sediment transport has been used for practical application that deals with understanding of whole phenomenon of sediment transport by the 3.11 tsunami, and projected earthquake along the Nankai Trough. However, challenges are remaining in developing a framework for logical assessment of the reliability of the numerical simulation. With reference to the method of V&V (Verification and Validation) guideline created by American Society of Mechanical Engineers, present study shows a new framework of V&V of the numerical simulation of sediment transport in a shallow sea due to the 3.11 tsunami. The main outcomes are as follows: 1) systematic review of phenomenon of interest, requirements for methods, and model parameters related to this study, 2) proposition of the framework for V&V and metrics for the simulation result. The issues remained as to how to assign uncertainty to the input data for numerical calculations and the observation data used for validation.

 Tipping weir whose structural form is the inclined sharp-crested weir has performance to realize easily the desired upstream water level corresponding to the discharge. In order to operate the weir efficiently and to make rational planning of its construction, it is necessary to develop the calculation method for discharge, upstream head and weir height of inclined sharp-crested weirs. In this pater, an attempt is made to give the explicit equation for each of the above three quantities as the mutual-dependence relation for free flow over inclined sharp-crested weirs. Functional relation between the critical depth to weir height ratio and the upstream head to weir height ratio was deduced on the basis of momentum theorem, then the relationship was determined using the experimental data by U. B. S. R. for various angles of weir plate incline and wide range of upstream head to weir height ratio. The derived equations for the three target quantities showed good agreement with experimental data for the range of upstream head to weir height ratio between about 0.3 and 14, almost full range of experiments by U. B. S. R.

 Kikkawa et al. proposed a formula for predicting overtopping flow over an upright seawall by applying the weir flow formula for steady flow. Goda et al. applied the formula to the estimation of overtopping rate over a seawall on a uniform slope This led to the Goda’s diagram for calculating the overtopping rate for irregular waves. Since then, Goda's Diagram has been used in actual seawall design in Japan for about half a century. The authors have clarified the characteristics of wave overtopping on seawalls against regular waves by numerical calculations using CADMAS-SURF and large-scale hydraulic experiments. This paper expands on that research by clarifying the characteristics of wave overtopping on upright, dissipating, and terrace-type seawalls for irregular waves. It is shown that the hydraulic characteristics of irregular waves and those of regular waves can be utilized in a complementary manner.

 This study proposes a method for estimating unsaturated soil hydraulic parameters based on measurement data from a portable mini disk infiltrometer, aiming to establish a technique for estimating the unsaturated soil hydraulic properties from the results of simplified field tests. As a result, while there were limitations in the range of field saturated hydraulic conductivities to which the proposed method can be applied, the validity of the proposed method was confirmed through comparisons with water retention tests and permeability tests. The proposed method is effective as a technique for estimating unsaturated soil hydraulic properties at multiple in situ points because it can estimate parameters related to the soil water characteristic curve that cannot be solely estimated from the test results using a portable mini disk infiltrometer.

 We examined the effect of the geological structure outside the tunnel excavation cross-section on the tunnel deformation of at its intersection. A literature review confirmed that tunnel deformation increases in locations with fault fracture zones and weak layers with numerous geological cracks. After analyzing tunnel construction records for the relevant ground, it was confirmed that the displacement of the invert excavation surface increases in areas where weak layers with gentle slopes were present. Additionally, rock tests revealed a correlation between an increased slaking index in rocks with numerous cracks and an augmented blistering effect. Furthermore, numerical analysis demonstrated that the location and displacement of the tunnel defamation are influenced by the degree of intersection with the weak layer. It became evident that, to prevent tunnel deformation, especially invert heaving, it is crucial to identify the weak layer containing numerous cracks and confirm its continuity.

 The "Excellent Eco-Commuting Business Sites Certification System" was established in 2009 to promote the spread of "eco-commuting, " a shift from driving to commuting in an environmentally friendly modes. The number of certified establishments has been on a leveling off since 2013. However, the number of certified establishments has been recovering even under the COVID-19 pandemic due to strategical promotional activities and the government's recent carbon neutrality policy.

 The aims of this study are 1) to describe the status of implementation of promotional strategies considering trends such as the COVID-19 pandemic and carbon neutrality and 2) to compare the efforts of certified establishments before and after the COVID-19 pandemic. As a result, it was found that the ratio of the implementation of staggered working hours, telecommuting, and subsidies for walking and bicycle commuting tended to increase. It is indicated that the self-restraint on leaving home after the COVID-19 pandemic led to a reconsidering of work styles and an diversification of commuting modes.

 It is not technically easy, because of a luck of standard specifications, manuals, and experiences, to design and maintain special bridges which accepts use of novel members and/or challengeable combination of several types of members in the same way as standard bridges. Therefore, new design concept considering appropriate maintenance scenario and maintenance plan in which structure properties of the bridges are strongly required. With this understanding, we have proposed the design process for special bridges. The proposed process consists of five steps, i.e., planning of the bridge, setting of damage control level, verifying structure performance, structural characteristics evaluation of the bridge, and maintenance planning. In this paper, basic way of thinking at each step is described through practice examples using special brides in Shin-Tomei expressway.

 In vehicle traffic surveys, methods are being proposed to replace the current visual surveys with AI traffic surveys. These AI traffic surveys are utilizing advanced image processing methods more than ever before, and against this background, new vehicle-count methods are being proposed. These methods analyze 4K videos taken by video cameras at survey points, and if these existing methods could be applied to existing CCTV images owned by road managers, it would become possible to conduct AI traffic surveys without the necessity of installing new cameras. However, many CCTV videos have a low resolution because they are intended for long-term monitoring, and in addition, there is a dullness due to image distortion or deterioration due to the long length of time since installation. Therefore, there is a high possibility that the accuracy may be insufficient for traffic volume observation using existing methods. In this research, focusing on the fact that features due to image distortion and dullness can be removed by blurring vehicle images detected from the entire image, a vehicle-type recognition method is proposed using only major features of the vehicles. In a demonstration experiment, we compared the classification accuracy before and after the introduction of the proposed method, and showed that it is possible to count small and large vehicles with higher accuracy than the existing method for SD and HD quality video images. As a result, we were able to confirm the effectiveness of the proposed method in AI traffic volume surveys.

 In the Tedorigawa river, we conducted analysis on relationships between invasion and spread process of alien species such as black locust (Robinia pseudoacacia), tree of heaven (Ailanthus altissima) and river channel morphology using from the past vegetation map National Census of River Environment (NCRE). Then we identified river channel morphology influencing spread of the alien wood were. After the analysis and identification, calculation condition of riverbed movable simulation and its times that could reproduce the river morphology were evaluated. In the results, we clarified that invasion and spread of alien species were caused not only along main river channel during normal water level but also secondary channel during in flood. To reproduce river morphology of the secondary channel, numerical simulation condition that is riverbed material was mixed substrate type, upper flow discharge condition was hourly discharge, spatial distribution of roughness using the vegetation map of NCRE were effective.