Tokyo Gas has introduced the super-dense real-time monitoring earthquake system, SUPREME, composed of ultra high density seismographs for the purpose of prevention of secondary disasters at the time of earthquake. SUPREME collects seismic observation information promptly, identifies blocks to be stopped immediately, plays an important role to predict damage to the pressure gas conduit and supports supply stop judgment according to the degree of damage. In this study, the authors investigate the damage of low pressure gas pipelines in the Great East Japan Earthquake by classifying it according to the characteristics of damage by analyzing considering the influence of terrain and reviewing the composition of the damage prediction equations.

 In this study, to examine the effect of the mechanical properties of the expanded material on the performance of the multi-layered absorbing system, a scaled model of the absorbing system composed of sand, RC plate, and expanded material was designed and manufactured. Weight drop impact tests were performed by changing the type of expanded material, layer configuration, and input energy due to impact loading. The results showed that the larger the compressive strength of the expanded material, the larger the weight impact force and transmitted impact force, and the smaller the weight penetration and the degree of damage to the expanded material. Also, the shear stress acting on the RC plate increases as the compressive strength of the expanded material increases, and the tendency of punching shearing of the RC plate appears more strongly. It has been found that it has twice as much energy absorption performance as the input energy in design.

 For the painted steel structures exposed to highly corrosive environments, especially where under the air-borne sea salt deposition, most of the localized corrosion initiates from coating flaws and defects. These corrosion cases would often progress with the mutual interaction between adjacent defects, because of the occurrence of the electrical short circuit around the multiple coating defects due to the stagnated rainwater or dew. This study focused on those regions in steel structure where the rainwater accumulated, and wetdry cycles repeated caused by dew. The objective is to investigate the electrochemical properties of corrosion between adjacent coating defects during the initial stage. Therefore, the model specimens embedded with a plurality of electrodes were fabricated to simulate coating defects, and the time-dependent macrocell currents were monitored between the electrodes. Based on the test results, an estimation method of the corrosion current density was proposed by investigating the electrochemical properties of the three coating defects in the water stagnated environment. Additionally, for the cyclic wet-dry environment, it was clear that the corrosion occurred in small-area defect would be easier to progress than that of a large-area defect.

 Relaxation of high strength bolted joints causes large bolt pretension loss at an initial stage of relaxation. However, the detailed characteristics had not been clarified. In this study, relaxation tests targeting many types of high strength bolted joints were carried out. Then, we investigated characteristics of bolt pretension loss at an initial stage of relaxation by literature search. From these results, we discussed the initial value setting method for relaxation tests in high strength bolted joints.

 Anti-freezing salt is a factor of corrosion like airborne sea salt, but it has not been studied sufficiently if anti-freezing salt scattered from the road surface of a bridge without surrounding obstacles may adhere to its girders. This paper investigates the characteristics of the behavior in the atmosphere and adhesion to the bridge girders of anti-freezing salt particles using computational fluid dynamics. It was clarified that anti-freezing salt may adhere to the bridge girders without surrounding obstacles because of airflows formed by the interaction between the approaching flow and the bridge itself, depending on the approaching wind speed and size of a salt particle. The combination of a vertical plate installed to the upstream bridge railing and a horizontal one the downstream changed airflows around the bridge to reduce the adhesion amount of anti-freezing salt to the bridge girders very much.

 In order to mitigate resonance induced significant vibration of high-speed railway bridges under train passages, additional supports reinforcement that new supports are added into the span have been studied. However the reinforcement effect, bridge dynamic characteristics and the bending moment distribution also change significantly depending on the position and the supporting stiffness of additional supports. In this study, the numerical model was established and the structural parameters are updated according to the measured data of a target bridge, and the full-scale additional supports movement experiments performed on the actual bridge could verify the high evaluation accuracy of updated numerical model for the additional support reinforcement effects. In addition, parametric study using verified numerical model clarified that the additional supports with 2 m distances on both sides or 3 m distance on one side from the existing supports can provide sufficient reductions of the maximum displacement. And these reinforcement can satisfy the various constraints even if additional supports have the supporting stiffness less than half of the existing supports.

 Over the last decade, fatigue cracks have been observed at welded joints between U-ribs and deck plates in many orthotropic steel deck bridges in Japan. Among the cracks, this paper focuses on fatigue cracks that initiate from a weld root of rib-to-deck welded joints and propagate to a deck plate. This study examines the effect of countermeasure with overlaying Ultra-High Performance Fibre Reinforced cement-based Composites (UHPFRC) on steel decks with cracks from U-rib welds, and confirms the fatigue durability of this countermeasure method. Specifically, the suppressing effect on crack propagation and the fatigue durability of UHPFRC itself and the interface between UHPFRC and the deck plate were confirmed by a wheel running test and finite element analysis. As a result, it was clarified that this countermeasure has a positive effect to retard further crack propagation compared with a countermeasure with overlaying steel fiber reinforced concrete which is generally adopted. In addition, it was revealed that this countermeasure has enough fatigue durability.

 The structural model update based on actual measurement data has been recently discussed as the core technology for performance-based maintenance and quantitative evaluation of strengthening effects. In this study, the author proposes the dual sampling method combining the MCMC method and GA, for the purpose of updating the structural model and evaluating the reliability of strengthening considering the uncertainty of current performance. The proposed method was applied to the measurement data of maximum displacement for high-speed railway bridges for which additional supporting strengthening is being considered, and it was found that the dual sampling method can estimate the uncertainty of current performance, which cannot be evaluated with the MCMC method only. It was also confirmed that the uncertainty of current performance estimated by the dual sampling method significantly affects the required rigidity of additional supports within 1.5 m from existing supports.

 In order to improve the accuracy of estimating the cross-sectional rigidity of railway bridges, this study quantified the effect of non-structural members on the vibration characteristics of the main structure on the basis of actual bridge measurements and three-dimensional finite element analyses. A simple evaluation method of cross-sectional rigidity considering non structural members and expansion joints was proposed. The actual bridge measurement revealed that stress is generated also in non-structural members when the train passing, and the non-structural members near the expansion joint have almost no stress. The proposed method can easily evaluate the cross-sectional rigidity based on the assumption of Bernoulli-Euler theory, considering the effective coefficient quantified for each non-structural member type and the reduction of the effective coefficient due to expansion joint arrangement installed on the non-structural member, which is a highly versatile method in practical design.

 A cover anticorrosion method is expected to have the effect of suppressing inflow of environmental factors from outside, and is an anticorrosion method capable of improving corrosion environment. However, there are few studies on evaluation of corrosion environment in enclosed girder space. In this study, a sandwich panel was attached to a steel plate girder bridge which is constructed in coastal area of subtropical zone, and corrosion environment in internal space is evaluated by measurement and analysis. In addition to evaluation of environmental factors such as salinity, temperature, humidity, time of wet and exposure test, thermal fluid simulation was carried out for dew condensation phenomenon observed sporadically on deck plate in internal space. Furthermore, exposure tests were conducted at vicinity of the bridge, and the environmental improvement effect of cover anticorrosion method was confirmed by comparing with the environment inside and outside the girder.

 The Box-Cox transform is used for the analyses on weather risks having non-normal processes. For the lack of information on the parameter value in the Box-Cox transform, the data on the parameter values for a variety of weather factors need to be collected and compiled . In this study, a dataset of parameter values in the Box-Cox transform for daily maximum wind speeds is presented for the convenience of strong-wind risk estimations, in which the time histories of daily maximum wind speed observed at meteorological stations in 116 regions are used. The relationship between the parameter value and the topography of each region is discussed, and the parameter values are classified into 8 groups in accordance with the topographical features.