According to the current regulation regarding the railway train operation, when a wind speed exceeding the prescribed value is observed by the anemometer, the train shall reduce its speed below the predetermined operating speed or stop absolutely. However, in cases where the train is running at a speed slowed down in the strong wind section, the period during which the train is exposed to the strong wind becomes long, whereby there is a possibility that the train safety is endangered. Therefore, after assuming the stochastic wind speed model (a stochastic process), we calculate the probability that the stochastic process exceeds the critical wind speed of overturning while the train passes through the danger zone. Then, we decide the train operation speed at which the probability is minimized. For the stochastic process assumed, we compute an index (probability index) for discriminating the magnitude of the probability of exceeding the critical wind speed of overturning. Then, the probability of exceeding the critical wind speed of overturning became minimum at other time than the train was running at a speed slowed down (less than 25 km/h).

 The remaining function after a Level 2 earthquake has become important issue of road bridges design in Japan. Authors have proposed a seismic retrofit method that die-and-rod friction dampers are installed in bearing parts of existing bridges in the bridge axial rectangular direction. This method does not impair the soundness of bridges against Level 1 earthquake, and improves earthquake resistance against Level 2 earthquake. This paper describes the results of static and dynamic load tests on the damper. As a result of the experiment, it was confirmed that the damper exhibits performance such as having a rigid-plastic hysteretic characteristics even at dynamic load test exceeding the maximum speed of 100 cm / sec.

 Prevention of external pressure buckling is important for the design of embedded penstocks. Different behavior from exposed pipe is shown due to the constraint effect of infilled concrete and bedrock, and the Amstutz’s formula assuming infilled concrete and bedrock as rigid body has been used since the 1960’s. In order to respond to the demand for large pumped storage power plant and high head in the 1970s and thereafter, the strength of steel pipes has been increased, but the discussion of the necessary rigidity for infilled concrete and bedrock has not been made. Since degradation of hydraulic structure and situational change of external pressure due to aging are points to keep in mind, in this paper, nonlinear FEM parametric analyses are executed considering the material properties of surrounding materials and contact condition between the penstock outer surface and concrete. After verifying the FEM analysis model by comparing with the test results by Borot, the influence on the external buckling pressure is examined according to actual conditions.

 Friction type of high strength bolted joint treated with thick-type inorganic zinc-rich paint shows so large bolt axial force loss by relaxation that the bolt axial force often drops below the design axial force. One of the authors showed that safety and reliability of this type of joint can be improved by tightening the bolts under 15%-additional bolt axial force. However, the applicability of the proposed tightening method was verified with only the standard type specimens with 22mm main plate thickness. In addition, the proposed tightening method cannot be directly applied to the joints using torque-shear bolts. The purpose of this study is to evaluate the applicability of the proposed tightening method to the joints with thick main plates up to 75 mm and the joints using torque-shear bolts. In this study, bolt relaxation tests and slip tests were carried out with the specimens with thick plates. As a result, the characteristics of bolt axial force and slip coefficient of the joints were clarified. Based on the results, the applicability of the tightening method was verified for the joints with extremely thick plates. Furthermore, a new bolt-tightening method, in which the final tightening of the bolts is executed 24 hours after the temporary tightening, was proposed for the joints using torque-shear bolts.

 The atmospheric corrosion prediction model for maintenance of bridges based on weather monitoring and high-resolution weather simulation was investigated. First, a method combining a computational fluid dynamics model and a statistical procedure proposed by CRIEPI had a capability to estimate the amounts at locations of surveyed bridges and also wide-area distributions of the cumulative amount of airborne sea salt by considering the local topography. Second, a machine-learning approach to corrosion and meteorological data extracted several feature parameters. The generalized predictive model for atmospheric corrosion rate was built on the basis of Random Forest algorism. The accuracy of the prediction model was verified using data obtained from the exposure test at Choshi, and at the actual three bridges located in Choshi area. Based on this prediction model, the corrosion map with 1 km mesh spatial resolution was created by open source GIS software.

 The fatigue failure origin of non-load-carrying type cruciform fillet welded joint is usually a weld toe. However, when UIT (Ultrasonic Impact Treatment) is applied to the weld toe, weld root also become fatigue failure origin. Fatigue crack initiation and propagation behavior and fatigue life in case of root failure have not been sufficiently made clear yet. In this study, fatigue tests on non-load-carrying type cruciform fillet welded joint treated by UIT have been carried out, and the crack initiation and propagation behavior from the weld root have been indicated. In addition, the fatigue life in case of root failure was tried to be estimated by using effective notch stress conception and crack opening-closing behavior.

 Steel piers with grade SM570 high strength steel are normally proportioned in design under a requirement that their seismic responses remain in the elastic range. This is chiefly because the available data about the plastic behavior of SM570 steel is too scarce to be utilized in the damage-controlled seismic design. Recently, a series of cyclic loading tests were conducted to examine the elastic-plastic ultimate behavior of concrete-filled tubular SM 570 steel piers, referred to as SM570 CFT piers. Herein, an advanced analysis method originally presented by authors for normal CFT piers was modified and calibrated based on the cyclic loading test results on the SM570 CFT pier specimens and a newly conducted cyclic loading test results on SM570 steel. This is to provide an analytical tool to assess the hysteretic ultimate behavior of the SM570 CFT piers. The proposed analysis method precisely considers the local buckling of steel plates, nonlinear behavior of confined concrete, and interface action between the steel plate and in-filled concrete. Therefore, the proposed method can be used to predict the seismic ultimate of the SM570 CFT piers in terms of their force-displacement relations and local plastic strains.

 Since around 2000, a lot of fatigue cracks propagating into deck plate have been detected in existing orthotropic steel deck (OSD) bridges. The cause of the cracks is mainly due to out-of-plane bending of 12mm thickness deck plate. As an effective measure against those cracks, steel-fiber reinforced concrete (SFRC) overlays have been used for many existing damaged OSDs. It has been confirmed that they can drastically decrease the out-of-plane deformation of the deck plate and greatly reduce the local stress of the weld route portion where the cracks initiate. However, the effect of the SFRC overlay under the existence of deck crack inside the deck plate has not been clarified. In this paper, for the purpose of evaluating the retrofit performance under existing deck cracks, fatigue tests of the OSD specimens with pre-cracking inside the deck plates were carried out under SFRC overlay. Also, local stresses and stress intensity factors were analyzed by FEA, and effectiveness of SFRC overlay was assessed from the viewpoint of preventing the deck cracks from progressing.

 In the Hamaoka Nuclear Power Station, the tsunami protection wall was constructed along coastline around the site, following the tsunami disaster of the 2011 off the Pacific coast of Tohoku Earthquake on March 11, 2011. The tsunami protection wall, built between the dune embankment facing the sea and power station facilities, features underground walls as the foundation structure which embedded into the foundation ground consists of rock and relatively dense sand deposit.

 In this study, centrifugal model experiments were firstly performed to investigate the stability of the tsunami protection wall under the severe earthquake. Followings were found from the experiments. 1) Seismic response of the tsunami protection wall is affected by the existence of dune embankment. 2) Stability of the structure, in terms of the tsunami protection wall movement and the deformation of foundation structure, up to the maximum acceleration of 2,000 Gals input motion is verified. Then, non-linear FE analyses were performed to assess the validation of the code utilizing in the design process, and verified the reproductivities of the deformation of the foundation as well as the reaction force distribution of the ground against the wall foundation during the earthquake.

 A pressure fluctuation is generated when a high-speed train passing through a tunnel, and we need to take its load pressure into account in the structural design of tunnel lining. The maglev train of the Linear Chuo Shinkansen will travel at a speed of 500km/h and it is required to consider the abnormal loads caused by aerodynamic brake system function when an abnormality occurs. In this study pressure is measured when a train runs into and runs through the tunnel of the Yamanashi Test Line and numerical simulations of flow around maglev trains passing by each other are conducted to evaluate the maximum loads on a tunnel lining when the aerodynamic brake system is activated. The stress versus the maximum loads under operation trains conditions is examined by simulating the stress for a tunnel lining by FEM.

 To evaluate deterioration characteristics of re-painted steel structure is crucially meaningful for making maintenance plan to painted steel structure in the future. In order to clarify the effect of Sn-bearing steel on the deterioration characteristics of re-painted steel structure, its corrosion behavior at paint defect of paint film on the rusted surface having difference base texture and residual chlorine was investigated by exposure test and accelerated corrosion cycle test. Sn-bearing steel showed a similar corrosivity to conventional steel (SM490 steel) in case of the accelerated corrosion combined cycle test composed of long wetting time, while it showed superior corrosion resistance in case of the exposure test. It is found that the evaluation using test specimens repainted on its surface remaining old paint film is simulated their deterioration characteristics accurately rather than that of using test specimens painted on its rusted full surface. For more quantitative evaluation of deterioration characteristics of re-painted steel structure, accelerated corrosion test considering rust layer, residual chloride and wetting time at surface of steel is supposedly required.

 Constructed fifty years ago, the Chita 2nd bridge is the oldest weathering steel bridge in Japan. The corrosion properties and structural performance of the bridge were investigated herein to evaluate the degree of deterioration. The bridge was found to be in good condition, despite being exposed to high quantities of airborne salt. The corrosion environment characteristics around the bridge were studied to understand the reason for bridge’s sustainability. Furthermore, the remaining lifetime of the Chita 2nd bridge was estimated, considering both the corrosion properties and structural performance.

 Slip coefficient of friction type of high strength bolted connection is well know to depend on the condition of contact surfaces. However, slip displacement at slip resistance tests is not clarified. In this study, the friction type of high strength bolted connection specimens were made on steel plates, in which contact surfaces are to be rough without mill scale and have zinc-rich paint, then slip tests were carried out on these specimens. From these results, we discussed the slip displacement at slip resistance test of high strength bolted joints considering condition of contact surface.

 High strength hexagon bolts are widely used to bolted joints in steel bridges. It is known that their bolts vary widely of torque coefficients. However, characteristics of torque coefficients not clarified. In this paper, we have investigated the 4815 of torque coefficients on the basis of the mill sheet data and bolt-tightening tests data in order to clarify torque coefficients on high strength hexagon bolts of 22 mm diameter. We also have investigated the mechanical properties of their bolts.