Curved steel box girder bridges are widely used in viaducts in urban areas, as well as highway junctions. Automatic welding robots cannot be applied to welding horizontal stiffeners to the web panel due to the girder curvature. Furthermore, the manufacturing costs of hand welding are very high. Elimination or reduction of the number of horizontal stiffeners without increasing the web thickness is desirable.

 In the present study, ultimate load carrying capacity test has been carried out and the failure process was verified in order to evaluate the mechanical effects of horizontal stiffeners on the ultimate load carrying capacity. From the experimental results, it was found that, even if the horizontal stiffeners are eliminated, the ultimate load carrying capacity decrease is much smaller than the decrease of the bending buckling strength of the web panel specified in the Japan Specifications For Highway Bridges. Furthermore, it was proved that the compression flange of box girders restrains bending buckling of the web panel so that even if the horizontal stiffeners are eliminated, the effect on the load-vertical displacement relationship is small and the decrease of the ultimate load carrying capacity is about 2%.

 Since the 1995 Hyogo-ken Nanbu Earthquake, rubber dampers have been increasingly adopted to improve seismic resistance. However, in recent years, a deterioration phenomenon in rubber dampers has been reported in which the vulcanization bonding area between the bottom of the rubber damper laminate and the bottom steel plate peels off. Although this delamination causes a significant reduction in load-bearing capacity, a method for measuring the accurate degree of delamination has not yet been established. In this study, numerical analyses were conducted to clarify the effect of the degree of delamination on the shear deformation shape of rubber dampers. As a result, it was found that the shear deformation shape is affected by the difference in the shape of the rubber damper warpage.

 In order to confirm the formation of protective rust on weathering steel bridges, it is necessary to properly evaluate the state of rust, and inspections are often conducted based on visual appearance evaluation. In recent years, quantification of appearance evaluation using deep learning has been promoted in order to appropriately judge the rust condition, but there are still problems in classification based on feature extraction in images. In this study, we investigated appearance evaluation of weathering steel bridges based on rust thickness using deep learning. Specifically, we focused on the rust thickness on the steel surface and attempted to evaluate the appearance derived from the proximity images. As a result, it was found that deep learning enabled appearance evaluation, suggesting that maintenance and management can be made more efficient.

 In recent years, there have been many examples of pedestrian bridges using GFRP as the main structural material because of its properties such as high strength, high corrosion resistance, and light weight. However, this material has not been applied to road and rail bridges in Japan. Because these bridges are heavier and have more severe design requirements than footbridges, it is unknown whether the material properties of GFRP can satisfy these requirements. It is also considered that thick FRP members will be required to satisfy the design requirements of the bridges. Based on this background, we tried to verify the forming of 40 mm thick GFRP by the hand layup method and evaluated the mechanical properties of GFRP. As a result, fundamental material properties for structural design were provided.

 In the design of structures subjected to moving loads, such as bridges, the influence line is indispensable. The same number of analyses as the number of nodes on the surface to which the load is possibly applied is required to obtain the influence line for finite element models. The Müller-Breslau principle, when used in finite element analysis, necessitates intricate model modification for introducing discontinuous displacements at the point of interest. To solve this problem, we proposed an influence line analysis method that can be effortlessly incorporated into standard finite element codes without necessitating model modifications. In this paper, we introduce a method for applying this technique to shell elements, which are commonly used in bridge finite element models.

 A countermeasure method is proposed for fatigue cracks that initiate from the weld root of U-rib to deck welded joints of orthotropic steel decks, which does not require traffic restrictions and does not increase the dead load. On the other hand, fatigue durability of general parts except for cross rib sections and ranges of peening treatment are still unclear. This paper attempts to solve those problems and verifies the durability of the fatigue countermeasure method. First, fatigue test methods that can reproduce fatigue cracks in the general parts of U-rib to deck welded joints of existing orthotropic steel decks was investigated. Next, based on the investigation results of fatigue test methods, the fatigue durability of general parts of the countermeasure was clarified by wheel running test, and the data necessary for determining the peening treatment areas were obtained. Finally, a proposal for improved countermeasures is presented.

 Seabed surfaces observed by echo sounding after dredging may be shallower than nautical depths in muddy areas with fluid mud layer and re-dredging may be needed. It will be more likely to occur since the frequency of ultrasounds rises by introducing “ICT dredging”. When we measure wet densities of fluid mud corresponding to nautical depths using density sensors, we can manage water depths more efficiently. But this measurement brings about extra works during construction.

 We studied how the thickness of sediment with a bulk density of 1,200 kg/m³ or less after dredging changed in response to the distribution of bulk densities of fluid mud before dredging through the field measurement. We established a simple evaluation method for nautical depths after dredging. It was shown that the bulk density of 1,200 kg/m³ can be predicted by bulk densities of fluid mud before dredging and multibeam sonar after dredging.

 This study covers the Honkawa River, a Class B river in the Honkawa River system that Hiroshima Prefecture designated as an urban river in July 2022 and established flood countermeasure plans in March 2023. We conducted a quantitative analysis to ascertain the influence and consequences of river development and flood control interventions, including sewerage enhancements, on designated small- and medium-sized rivers traversing urbanized regions within river basins.

 The primary conclusions of this study are as follows: 1) In basins with sewerage drainage areas, the runoff volume from these areas cannot freely discharge into the river, naturally restricting the runoff within the basin itself. 2) Basin interventions such as sewerage enhancements and paddy field dams exhibit limited efficacy on river dynamics, with sewerage enhancements potentially leading to increased river water levels. 3) For small- and medium-sized rivers, where the majority of basins are encompassed by sewerage drainage areas, failure to accurately ascertain actual runoff phenomena, such as the relationship between inland flooding and pump drainage, may result in discrepancies with real-world scenarios, potentially resulting in excessive river development.

 Since the Meiji era, rapid modernization (urbanization) has led to substantial coastal erosion. Concretely, the averaged annual loss of beach area in Japan is reported to be as much as 160 hectares. Besides, the value of precious beach space has been recognized and coastal conservation measures have been implemented throughout the country. Since around 1990, there have been reports on topographic changes in a particular coastal area, but the changes in the location of the shoreline over an extensive area of analysis have not been understood. In this study, the characteristics of shoreline location change in the Kansai region were analyzed for each coastline type in terms of comparison of topographic maps. As a result, the sandy beaches where coastal conservation measures have been implemented are advancing (accretion), while the natural beaches without such measures are retreating (erosion). Furthermore, although the potential of fluvial sediment supply from the land area is increasing and improving, the erosion rate of sandy beaches is not affected by this evolution, suggesting the need for continuous coastal conservation measures.

 Autonomous Underwater Vehicles (AUVs), capable of conducting unmanned underwater surveys, have been recognized as a promising technology for enhancing productivity in underwater environments. In this study, we introduced an AUV equipped with a Phase Measuring Bathymetric Sonar (PMBS) for investigating the sedimentation conditions in Lake Horai (Ure Dam), and evaluated its effectiveness from three aspects: Accuracy, Risk Avoidance, and Cost. The comparison of the averaged ground elevation data (mesh data with 1-meter interval) processed by the PMBS, and the Multibeam Echo Sounder (MBES) revealed no significant difference, indicating that the PMBS provides depth measurement accuracy comparable to the MBES. Furthermore, the sedimentation condition survey conducted using the AUV with PMBS not only facilitated the avoidance of inherent risks, such as researchers submerging into water, but also required half the number of survey personnel compared to the MBES survey. This resulted in approximately 50% reduction in labor related to equipment testing and depth measurement, as well as an estimated 60% reduction in associated labor costs.

 Volcanic sandy soil Shirasu filled ground whose particle is porous, crushable and liquefable had sometimes caused mudflow-type slope failure during earthquake under high water retention condition. In order to investigate the liquefable mechanism, the solid phase of porous soil particle compressibility and abrasivity were quantified by uniaxial compression test and cyclic shear test using small-sized test-piece shaped from Shirasu pumice stone. The solid specimens compression strength was 400-6200kPa, Young's modulus was 30-1100MPa, bulk modulus was 10-370MPa. These were too smaller value than concrete or original stone. Abrasion rate was 0.0027g/cm²/m/kPa. Assuming soil skeleton as face-centred cubic lattice whose particle size is mean diameter of Shirasu sand, the compressibility and mass-exchange due to abrasiveness significantly caused to increase void ratio. The B value was slightly incleased. Increasement of void ratio by abrasion during cyclic liading may be one of liquefable factors of Shirasu soil.

 In order to develop underground structure without rock mass collapse or slippage, it is important to construct a constitutive model that can accurately predict the strength and deformation characteristics of rock joint, which are weak areas of the rock mass. For this purpose, it is necessary to consider the geometry of the rock joint’s surface and their matching and adhesive conditions. Therefore, in this study, we conducted whether existing the elasto-plastic model of rock joint based on the critical state concept applied in the Cam-Clay model etc. can take into account differences in matching condition of rock joints, and demonstrated their applicability by analyzing shear tests in which only the initial matching differs. In addition, a new state variable was introduced into the model to take into account adhesion condition, and we conducted the analysis of shear tests with repeated shearing and holding to show that the model is capable of representing stress recovery associated with the development of adhesion.

 The transition of stress in the transition zone taking into account the self-weight in the slip line method based on the theory of plasticity has been clarified in the existing literature by deriving the characteristic equation. However, this problem remains unsolved due to the complexity of the mathematical treatment and finite difference methods are used to obtain the solution. Furthermore, many fundamental issues remain unsolved, such as boundary value problems and the geometry of slip lines.

 In this paper, these problems were solved by first the shape of the slip was formulated, the process of stress transition from the active zone to the passive zone was logically interpreted, and a new method was proposed for calculating the bearing capacity. In addition, a bearing capacity calculation formula was derived that can simultaneously take into account inclined loads, slope gradients, and seismic forces. Finally, the formula in this paper was compared with existing bearing capacity calculation formulas and its validity was confirmed.

 In this study, we investigated experimentally the relationship between the temperature and the refractive index at the mass ratio of water to glycerol to prepare the experimental equations (calibration curves) for the glycerol-method that can be used for measurements under different temperature conditions. From the obtained results, it was found that the refractive index of the aqueous glycerol mixture solution decreased with increasing the temperature, and the linear relationship between the two was observed regardless of the mass ratio of water to glycerol. Furthermore, it was shown that calibration curves under any temperature conditions could be prepared by entering the necessary data such as mass, temperature and refractive index.

 Two-way fixed effects (TWFE) model, which are frequently used for empirical analysis, suffers from biases in estimates under staggered adoption settings. We empirically assess the impacts of the Shinkansen and expressway developments on population, with explicitly considering the biases stemming from the staggered adoption. First, the degrees of the biases are confirmed using bacon decomposition. Next, we estimate several staggered difference in differences (DID) models as well as synthetic control method to investigate the effects of the Shinkansen and the expressway developments on population distribution. Third, we try to differentiate the impact of Shinkansen (expressway) from expressway (Shinkansen). The estimation results show that the positive treatment effect of the opening of both expressways and Shinkan-sen has been weakening over time, but the former still has a population-inducing effect even in recent years. On the other hand, the treatment effect of the opening of the Shinkansen on the population may have turned negative in recent years.

 In this study, concrete with a slump flow of about 45 cm was used to study mechanically-compacting flowable concrete to establish specific compaction methods according to the geometry of the structure and the reinforcement distribution conditions. The results of the compaction tests showed that the vibratory force of a bar vibrator had a more significant effect on the propagation of vibrations during compaction than when the mix was varied within the range where mechanically-compacting flowable concrete is practically feasible, indicating that the type and capacity of the bar vibrator should be taken into consideration when setting the compaction method. Through verification of the validity of the setting of the compaction method by actual construction experiments, a method was proposed to set the compaction method based on the relationship between the rod vibrator used, the construction conditions, the compaction time that allows filling, and the compaction interval, and to determine the degree of compaction by the flow gradient.

 A method for estimating stress and strain distribution generated over a long term in a cross-section due to volume changes such as drying shrinkage is proposed by an extended estimation method of chemical prestress and chemical prestrain of CPC (Chemically Prestressed Concrete) wall fences without symmetrical axis in cross section using a fiber model. These estimation strains are fairly good compared with the experimental results of two large-scale bridge deck specimens.

 It is shown that the long-term shrinkage behaviors of CPC wall fences are estimated by the proposed method of chemically prestress introduced using expansive concrete and tensile stress due to drying shrinkage are determined by correlations such as the placement of the non-restraint member and the restraint member. The restraint member is occurred a reaction tensile force and also can be occurred cracking by concentrated stress. In addition, a simple estimation method is also proposed.

 A corrosion protection management method was proposed using the corrosion rate of steel in concrete under cathodic protection as a control index. Experimental results using test specimens showed that the proposed method was able to control corrosion protection in the same way as the depolarization control method. The power consumption of the proposed method is smaller than that of the depolarization control method, and it is considered to be an economically effective control method.

 In order to evaluate the soundness of the granular base course by FWD for heavily trafficked asphalt pavement, the authors proposed a simple compressive strain prediction model using the base damage index (BDI) obtained directly from the FWD deflection curve which based on the relationship between BDI and the compressive strain on the surface of the granular base obtained from the multi-layered elastic analysis. In this study, we added data to improve the reliability of the compressive strain prediction model and its temperature-correct equation and examined about the relationship between compressive strain and various FWD based soundness evaluation indices of asphalt pavement shown in existing technical books. As the results, a soundness evaluation method for asphalt pavement by combining compressive strain with existing evaluation indices was proposed in this study.

 In response to Kyushu’s vulnerability to changes in typhoon characteristics due to global warming, this study applied a combination of self-organizing maps and cluster analysis to large-scale climate projection data to examine future changes in typhoon paths, intensity, frequency, and associated precipitation. The results showed that the absolute number of typhoons is projected to decrease overall. Additionally, while the occurrence of paths traversing north-south through Kyushu is expected to decline, paths crossing eastwest across the region are expected to increase. Furthermore, future changes in typhoon paths will vary depending on patterns of future sea surface temperature changes, and the latitude-dependent strengthening of typhoons will differ by path. Although precipitation associated with typhoons is generally expected to increase along all paths, the increase is particularly significant for typhoons taking north-south routes. The method was also devised using machine learning to capture the changing characteristics of precipitation from individual typhoons, enabling an analysis of future changes based on historical typhoon events.

 In recent years, a research field called “Decision Making under Deep Uncertainty” has been established, and there is a growing number of cases of applying its proposed methodologies to the planning and evaluation of climate change adaptation measures in water resources management and other sectors. This note provides an overview and application cases of one of such methodologies, that is, Robust Decision Making Framework. Authors argue that the use of methodologies provided in Decision Making under Deep Uncertainty should be considered, as appropriate, when planning or assessing climate change adaptation measures in Japan.

 Since 2020, the COVID-19 outbreak has prompted universities and national colleges of technology to start remote lectures by applying ICT technology. The remote lecture showed an advantage that a student can attend the class without taking trains and/or buses. In contrast, lack of communication with other students can lead to depression. Currently, lectures are held in classrooms, but to take advantage of remote lecture, lecture recordings are also provided with the students. This study is a learning analytics on students’ use of the class course recordings. In comparison between classes based on knowledge and/or calculation and based on exercise shows that the videos could be watched more frequently by the classes of knowledge and calculation. Additionally, more students watched the videos in the class in which homework is assigned every time. There could not be seen any tendency between the number of absences and watching time. No trend was also found between the grade and the watching time. The major purpose of the students to watch the videos was to prepare for the midterm and final examination. In general, the lecture videos were well utilized by the students.