Increasing sea surface temperatures (SST) caused by global warming might affect the recurrence wind speed by typhoon. Because the future spatial distribution of SST is uncertain, we proposed a method for uniformly increasing SST for use as the boundary condition of typhoon model. The output of statistical typhoon simulation with uniform increase of SST yielded the typhoon intensity, as did the model based on physical processes. Furthermore, estimation of the relation between the amount of SST increase and recurrence wind speed of typhoons was conducted using statistical typhoon simulation with uniformly increasing SST. Results show that 400-year recurrence wind speed will be less than the 100-year recurrence value in areas except Okinawa and northern Japan by the end of the 21st century.

 This paper examines a fatigue evaluation method for the cracks in the weld joints between a U-rib and a deck plate in orthotropic steel bridge decks. The crack initiates from the weld root and propagates into the deck plate or the weld bead. Fatigue tests and FE analyses were conducted in order to examine the local stresses available for fatigue assessment, and to propose a method to estimate them from some reference stresses around the weld joint. In addition, based on fatigue crack propagation analyses, a method to predict the crack propagation path was proposed.

 The objective is to propose the method to evaluate a fragility curve of an underground structure for multi damage modes, and first, fragility curves about flexural failure and shear failure are evaluated for a seawater pipe duct. Next a basic procedure to evaluate the fragility curve to combine the damage probability of both damage modes and evaluation cases are shown.

 When composite curves of two damage modes are compared, the 2063Gal which is Am of flexural failure is almost the same with the 2067Gal which is Am of shear failure which considered shear reinforcement, it is found that there is a possibility that two damage modes are generated simultaneously. Here, Am expresses a value of PGA where the damage probability becomes 50%. In addition, the damage probability of the structure obtained by the connection is larger than the value for each damage mode. Furthermore, it is thought that the risk for the individual damage mode becomes the underestimate.

 This study investigated opening and closing behavior of root gap and weld crack occurance in slit-welding under cyclic loading through welding tests and thermal elasto-plastic finite element analysis. Sectional observations after the welding test revealed that the crack occurance highly depends on the magnitude of root gap opening displacement and loading frequency in welding process, and also restraint intensity of slits. Then, through the simulation of welding under cyclic loading, it was clarified that root gap opening behavior during welding changes due to the restraint intensity of the slit, which correlates the tendency of the crack occurance under different restraint conditions. Based on the test and analysis results, a conditional expression for the weld crack occurrence consist of the initial root gap opening displacement, loading frequency and restraint intensity of slits was obtained, and its validity was verified by the experiments.

 A 5-span continuous steel girder bridge “Ookirihata Ohashi Bridge” was severely damaged by the 2016 Kumamoto earthquake. Some of concrete columns and pile foundations were significantly cracked and almost of rubber bearing supports were ruptured, which caused movement of the superstructure in the transversal direction, buckling of the steel girders and significant cracks to RC slab. This paper presents the decision-making process of the repair method based on a policy of “Recovery of load-bearing performance of the bridge system”. Some of ideas were derived through the process, namely recovery of the superstructure performance by adding a new girder without removing the buckled girder, and the design concept of the bearing supports with consideration of the reliability of load-bearing capacity of substructures after repair. These ideas and consideration for the design are also introduced in this paper.

 There are many examples about replacing the reinforced concrete slab with the precast concrete slab due to the slab deterioration in non-composite girders. However, a method of shear connector arrangement is not clear in the non-composite girder with the precast concrete slab. In this paper, when the precast concrete slab is employed for the simple and two-span continuous non-composite girders with the practical proportion, the shear connector arrangement which satisfies with the limit state of the serviceability and safety, is examined. In examining the shear connector responses, a non-linear rigid-body-spring model, which is useful for the analysis of the behavior of the composite girder with an imperfect interaction, is employed considering the effect of the temperature difference of the steel girder and concrete slab as well as the application history of the dead and live loads. As a result, it can be seen that an attention of the shear connector arrangement in the vicinity of the girder end is required to satisfy with the serviceability limit state.

 For a planning of the reconstruction of Aso-Ohashi bridge that was collapsed by the 2016 Kumamoto earthquake, a risk of the unexpected ground movement should be considered because an active fault exists near the bridge. It has been therefore essential study to mitigate the effect of the ground movement on performance (safety, serviceability and reparability) of the bridge at the process of a route planning as well as the structural design work.

 This paper presents several technical ideas to improve the structural redundancy and the structural resilience of the reconstructed bridge, namely Shin-Aso-Ohashi bridge which crosses the active fault. The Shin-Aso-Ohashi bridge was planned to equip with damage-controlled bearing supports so that the bridge would exhibit the predicted desirable damage and thus redundant response against the unexpected excessive fault displacement. A design concept of the damage-controlled structure is also introduced in this paper.

 In the steel bridge covered with the sandwich panel, the anticorrosive effect by the environmental improvement can be expected. However, there is no example of applying the sandwich panel to the weathering steel bridge, and the corrosion process of the weathering steel in the sealed condition has not been cleared. In this paper, test specimens of weathering steel were set on a plate girder bridge which was constructed in the seaside area of subtropical-zone and covered with a sandwich panel, and a change of corrosion condition and corrosion process was observed. The corrosion environment improvement effect by the sandwich panel was confirmed from the change of rust evaluation by RST method, amount of adhered salt, appearance, rust thickness and coating film thickness.

 Statistically supported assessments are required to evaluate the risk magnitude and to plan the strategies for the risk hedge, mitigation and transfer. This study focuses on the strong-wind risk and shows a convenient method to estimate the statistics of the daily maximum wind speeds. The Box-Cox transform is applied to the daily maximum wind speed data observed at the meteorological stations in 111 regions, and statistical analyses are conducted for those data where special attention is paid to the parameter value in the Box-Cox transform. From the results of the analyses, it builds simple models that input the parameter value in the Box-Cox transform and output the statistics of the daily maximum wind speed. The application range and the accuracy of these models are investigated.

 Several design methods have been proposed for bonding repair and reinforcement using carbon fiber reinforced polymer (CFRP). When the multi-layered CFRP bonding repair, the steps are provided at the ends of CFRP to improve the peeling load. In the previous paper, the design of step length was theoretically provided with the required length for transmission of sectional force at each step. However, this design might be result in excessive bond length. In this study, the authors proposed a new step design method for CFRP bonded steel plates under uniaxial load using the convergence of energy release rate at the step-end. It was shown that the proposed method provided a shorter CFRP length for multi-layered CFRP bonding repair compared with conventional design.