This paper describes the numerical procedure of solving liquefiable ground problems involving RC structures for unsaturated to saturated porous media and its verification and application based on a three-dimensional effective stress analysis method. The following conclusions are obtained from this study: (1) The developed procedure accurately reproduced the unsaturated seepage flow behavior, based on comparing laboratory test results with seepage flow analytical results; (2) The applicability of the procedure considering the material nonlinearity of both the soil and RC structure is verified, and an underground RC structure surrounded by unsaturated and saturated liquefiable ground is simulated. Moreover, the rational and acceptable seismic behavior of an underground RC structure is reproduced under a large-scale earthquake.

 Recently, machine learning (ML) has been actively applied to various problems in the civil engineering field. To further facilitate the use of ML in the civil engineering field, it is essential to have appropriate benchmark problems and training datasets with the characteristics of the civil engineering field. Nevertheless, such datasets have not yet been proposed sufficiently. In this study, using the finite element analysis, we propose fundamental datasets (no noise and no missing data) as benchmark problems for damage identification of bridge model, with four levels of difficulty. Then, we input the dataset into a total of 19 ML algorithms to assess the quality of the dataset using the coefficient of determination obtained from those algorithms. As a result of numerical experiments, the following points were found. For cases with a single damaged member, the best coefficient of determination for most of the members exceeded 0.5, resulting in suitable benchmarks with appropriate difficulty. For cases with two damaged members, the best coefficient of determination for almost half of the members was below 0.5, resulting in a challenging benchmark problem from the viewpoint of its high difficulties.

 Performance-based seismic assessment for water pipeline system has not been generalized in the several decade in Japan, Even though the performance-based approach is forced, it cannot be proceeded without the goal of performance. The seismic safety performance of Level 1, 2, 3 in the Japanese design code is developed based on reliability approach in which any appropriate goal of seismic design should be given in terms of the safety index for water supply authority, pipe suppliers and pipeline construction companies. Example study of the model network shows that the safety index of pipe joint should be 3.2~3.7 in order to obtain the performance level of 0.2~0.8 for water supply at the target demand.

 For the bridge abutment pile foundations with high parapet walls, when the surround ground lost resistance during earthquake due to the ground liquefaction, the bridge abutment foundations may suffer damage due to the large earth pressure and inertial force acting on the high parapet wall. In this study, the seismic retrofit effect of three liquefaction countermeasures for the bridge abutment pile foundations constructed on the thin liquefaction layer with high parapet wall was investigated using the dynamic centrifuge model experiments. For the liquefaction countermeasure with the steel pile wall constructed at the front side of the bridge abutment, the restraint effect of the displacement and rotation of the bridge abutment was limited. The maximum response of the bending moment and the earth pressure acting on the existing piles during dynamic testing was almost the same with that of the unretrofitted case. For the liquefaction countermeasure with the battered steel pile constructed at the two sides of bridge abutment, due to the ground flow-induced force increased by large acting area and the deformation mode of battered steel pile, the restraint effect of the bridge abutment rotation and its displacement was limited. However, for the liquefaction countermeasure with the steel pile wall constructed at the two sides of bridge abutment, due to the horizontal rigidity of abutment foundation increased by the steel pile wall, the restraint effect of the displacement and rotation of the bridge abutment was largely restricted.

 In this study, to improve the construction efficiency of seismic retrofitting for existing bridge pile foundation, the adding pile method with the face contact state between existing and additional footings was proposed, and its seismic retrofitting mechanism was verified using centrifuge experiment and frame numerical analysis. It was confirmed that the horizontal seismic force was transmitted from the existing pile foundation to the added pile foundation through the contact of the existing and added footings, and the horizontal seismic force acting on the existing pile foundation was largely reduced compared with the case without retrofitting. In addition, for the shear force was reduced, the bending moment of the existing pile foundation was also restrained.

 Damages to buried pipelines due to soil liquefaction have occurred in the past earthquake disasters. They often occurred near the boundary between liquefied and non-liquefied ground. In the 2011 off the Pacific coast of Tohoku Earthquake, a past study implied that the liquefied ground was greatly shaken and the strain was concentrated, which caused the pipe damage. In this study, the finite element method considering finite deformation is used to numerically analyze the sloshing behavior of the soil liquefied ground. After verifying the method by comparing it with solutions for fluids, a dynamic analysis is conducted for liquefied ground in Urayasu City. The localized strains caused by the sloshing are recognized, and the relationship between the location of the localized strains and the actual damage to the buried pipe is discussed.

 One of the factors that cause flow deformation with a time delay after an earthquake in gently sloping ground is the presence of pore water flowing into the sand layer directly below the impermeable layer from the lower layer. This is caused by the redistribution process of excess pore water pressure, which is increased by the excitation. Although the behavior of clean sand, in which shear deformation develops with volume expansion due to the inflow of pore water, has been experimentally investigated, few studies have focused on the effect of fines content. In this study, specimens with different fines content (F_c = 0, 10, 20, 30%) were prepared and subjected to undrained cyclic shear history after loading initial shear stress using a hollow torsion shear apparatus, followed by forced expansion shear test by pore water injection. As a result, it was found that the dilatancy characteristics of the specimens under porewater injection were affected by the fines content.

 In this decade, hazard maps have been developed and utilized for disaster prevention planning in communities. The values shown in the hazard maps are inherently uncertain. It is very important to reflect the probability information in the spatial resolution as well as the average value. In this study, given a probability distribution, we propose a new visualization method (Uniform uncertainty mapping) that adjusts the resolution according to the significant difference at neighboring points. We first introduce the theoretical framework of this method and discuss its performance by applying it to numerical problems. It is then applied to the problem of estimating 1D velocity structure in microtremor array exploration as an example of the inverse problem, and to the problem of displaying 2D ground amplification as an example of the seismic hazard map, respectively.

 The recent seismic design on box culverts significantly concerns the superposition of fault displacement and seismic shaking. We conducted the three-dimensional finite element analysis of the superposition by focusing on the weak axis of the box culvert and the direction of seismic motion. As a result, the damage distribution over the box culverts was quantitatively evaluated using the safety factor based on the yield strength curve newly developed in this study and was clearly dependent on the seismic direction. It was also confirmed that the response seismic intensity method for the superposition can be applied to the damage evaluation by comparing the damage distribution obtained from time history analysis using the same finite element model. Furthermore, the applicability of dynamic analysis was examined.

 The probability distributions have been comprehensively modeled for natural logarithm of the ratios of every pair of ground motion intensity measures (IM’s) defined from orthogonal horizontal components of seismic waveforms; modeled are maximum values of each component (NS, EW), geometric mean (GM), larger value (Larger), maximum value obtained by axial rotation (rot100). Basically, normal distribution was employed for ratios among “(NS, EW), ” “GM” and “Larger, ” and Gamma distribution was employed for ratios related to “rot100.” Accelerograms recorded by K-NET, velocity waveforms obtained by their time integration and response waveforms of SDOF with 5% damping were used for the analysis. The proposed models agree well with the histograms of ratios. Period-dependent characteristics of the ratios were also discussed. Distribution of the inverted ratio can be derived as axially symmetric distribution of the original ratio. In addition, the models related to median value obtained by axial rotation (rot50) were modified from the previous study (Nojima and Yokoyama, 2021). The proposed comprehensive models enable one to convert an arbitrary pair of various IM’s in a probabilistic manner using the exceeding level.

 Seismic fault displacement poses a significant threat to various types of civil structures. Location and amount of displacement have a high degree of uncertainty for carrying out the countermeasure of fault movement. Therefore, the current countermeasures are conducted in such a way that the possible surface displacement on the active faults crossing the buried pipeline is estimated using an empirical formula. By the way, if the fault displacement does not appear on the ground surface, the ground strain due to the fault dislocation may cause damage to the pipeline. This study aims to clarify the possible deformation of buried pipelines caused by fault dislocations based on the elasticity theory of dislocation and to provide a database for exploring fault countermeasures for buried pipelines.

 This paper presents a methodology for estimating a connectivity of road network considering the vulnerability of bridges under seismic and tsunami hazards. With the aid of a geographic information system and graph theory, the deterioration of the bridge network’s connectivity can be easily estimated based on seismic and tsunami hazard assessments, and structural fragility estimation. Both uncertainties associated with fault movement estimations, spatial distribution of hazard intensities and structural vulnerability, and damage correlation among bridges are considered when estimating the probabilistic connectivity in Monte Carlo simulation. In an illustrative example, the bridge network affected by the anticipated Nankai Trough earthquake is analysed. Computational results demonstrate that the connectivity depends highly on spatial distribution of hazard intensities and the correlation among damage states of bridges.

 In this paper, the applicability of failure criteria (thickness increment of RC member, relative displacement at compressive edge, deviation strain second invariant) for seismic safety evaluation of structure have been studied by comparing with results of loading experiments of full-scale RC members. Specimens are W1100mm×D1100mm×H3100mm RC columns. Experiment cases are as follows: Standard case (N-1), Post-installed shear reinforcements (P-1), Loading in diagonal direction (N-2-1), Effects of pre-cracks (N-2-2). N-1, N-2-1 and N-2-2 are shear-failure type, and P-1 is bending-failure type. As a result, relationships between values of failure criteria and damage states of specimens under each condition of experiments are obtained, and applicability of each failure criteria in current manuals is verified.

 There are many railway bridges with locking piers in urban areas, and measures to prevent excessive displacement of girders and collapse of bridges are required. However, these bridges may be difficult to apply with conventional countermeasures because the construction and installation space is narrow due to urban circumstances. Therefore, some of the authors have proposed a damping device with bridge collapse prevention function installable in narrow spaces. In this research, we propose a method for roughly designing the proposed device. Specifically, we organized the results of nonlinear response analysis of a single degree of freedom system and proposed a nomogram that can calculate the displacement of the girder and the response ductility factor of the pier in the specifications of the device.

 It is important to predict seismic damages of telecommunication conduits. We made a prediction model based on machine learning using the conduits inspection results and variables related to four earthquakes: the 1995 Southern Hyogo Prefecture Earthquake, the Mid Niigata prefecture Earthquake in 2004, the Niigataken Chuetsu-oki Earthquake in 2007, and the 2011 off the Pacific coast of Tohoku Earthquake. The model has sufficient classification performance for the test data, and is able to predict the damage for each earthquake. Though the performance of the model deteriorates against the 2016 Kumamoto Earthquake, the model is able to predict damaged conduits in high PGV area as vulnerable properly, and the performance can be improved if liquefaction and fault are considered.

 We proposed an evaluation method for the influence of earthquake monitoring system on emergency shutoff of city gas supply. Firstly, assuming random selection of locations of seismometers or incidental missing of observation, the effects of change in “k-out-of-n shutoff system” on shutoff probability were probabilistically modeled using hyper geometric distribution. Secondly, assuming planned selection of locations, increase, decrease or relocation of seismometers, relative importance of individual seismometer within a service block was evaluated on the basis of weighting factors calculated through the application of Ordinary Kriging for spatial interpolation of shaking intensity. Estimation variance with respect to spatial interpolation was also evaluated for a group of seismometers within a service block. We discussed the optimal allocation of seismometers under the restriction of the number of seismometers.

 In case where lifeline functions are degraded due to disaster, rapid and accurate dissemination of recovery projection is essentially important. In this study, aiming at improving the reliability of such information, we applied Kalman filter technique for sequential update of recovery projection of electric power outage. First, decreasing process of power outage is sequentially fitted by an exponential function. On the basis of state space model, the sequential updating process is formulated for the predicted distribution of the model parameter representing recovery pace. Then, Kalman filtering and Kalman prediction are performed, and three expected restoration curves are obtained based on the mean and the 95% confidence interval of the predicted distribution. In addition to two extreme curves assuming the worst and best pace are also shown. It is suggested that the possible range of recovery projection should be addressed by considering the uncertainty in recovery estimates.

 When soil liquefaction occurs, the stiffness of the soil skeleton is reduced, and the soil behaves like a fluid composite of soil particles and pore water. In this study, we formulate an expression for the phase transition of soil from solid to fluid, assuming a mechanical process similar to that of internal erosion, and derive the governing equations, including the conservation of momentum. It is confirmed that the proposed equations can be reduced to the Navier-Stokes equations under a hypothetical situation. Numerical analysis of the one-dimensional model and simulation of the centrifuge test results are performed using the proposed method. As a result, it is shown that the proposed method can analyze both solid and liquid phases without any inconsistency and can represent the natural phase transition.

 Although design earthquake motion is based on the previous disaster records and researches, the larger earthquake motion might happen. Collapse scenario design realizes resilient road bridges that will not lose the function or can be quickly recovered from the damage against larger earthquake motion. To implement the proposed design method, strength-stratifying rebar was developed. The previous study shows the effectiveness of strength-stratifying rebar on the computer analysis. In this research, we construct the RC column specimen with strength-stratifying rebar and analyze the effectiveness through the loading test. The result shows that strength-stratifying rebar enhances the pier strength as designed. However, the fact was found that in addition to the effects of bending strain in the plastic hinge region, elongation of axial rebar and residual elongation of pier needs to be considered for calculating the gap of strength-stratifying rebar’s anchor plate.

 Buried pipelines that intersect an active fault may be directly damaged by the movement of the fault. Since damage to buried pipes may have a significant impact on social activities, adequate countermeasures are desirable. This study conducted a distinct element method analysis to investigate the response of buried pipelines to lateral fault displacement. The distinct element method can handle the characteristics of the ground, which is a collection of granular materials, appropriately. An analytical model was set up with the intersection angle between the normal direction of the fault plane and the pipe axis set at 30 degrees. Two types of ground models, loose sand soil and dense sand soil, were analyzed with left-lateral and right-lateral fault displacements. From the results, it was confirmed that the numerical analysis using the distinct element method is useful for investigating the response of buried pipes subjected to lateral fault displacement.

 Nonlinear dynamic analysis method is proposed to calculate the seismic response of a railway bridge, in which the behavior of ground and the structure are expressed by a two-degree-of-freedom (2DOF) system. The push-over analyses with respect to the surface ground and the structure are first conducted respectively, and they are characterized by independent two single-degree-of-freedom (SDOF) systems. By coupling these two SDOF systems, it is possible to compose a 2DOF system that can conduct nonlinear dynamic analysis considering both soil and structural behaviors. The effectiveness of the proposed method was confirmed by applying it to a railroad bridge pier and comparing the results with those of a dynamic analysis using a detail space frame model. In addition, a method to improve the accuracy of the nonlinear response spectrum method was also investigated that enables simple evaluation of seismic response values of railroad structures, This method is effective as a method for calculating seismic response values for seismic design because the evaluation considers indispensable parameters with respect to the soil ground and the structure: natural period and strength.

 Masonry retaining walls are very fragile structures against earthquakes and a great number of damage cases have been reported. In order to mitigate such damage, it is necessary to understand the collapse mechanism of masonry walls during an earthquake and to evaluate stabilities and countermeasures. In recent years, several studies of the collapse mechanism have been conducted by numerical analyses. However, most of them used a simple shape model for representing masonry blocks. In order to develop three-dimensional DEM elements applicable to various arbitrary polyhedron shapes, the objective of this study is to investigate the fundamentals of the simple irregular polyhedral models that can represent the arbitrary shape by combining a number of hexahedral blocks. Then, we conducted drop experiments using wooden blocks with a convex shape and sliding tests for obtaining the friction coefficient. In order to validate the developed irregular polyhedral elements, we carried out the three-dimensional numerical simulations of the drop experiments. As a result, the block behaviors of experiments and numerical analyses show good agreement with each other.

 In the three dimensional nonlinear material FEM analysis of reinforced concrete members, the modeling method considering the effect of post-installation of Post installed head shear reinforcement bar (PHB) has been studied for distributed reinforcement, but not for discrete reinforcement. In this study, we proposed a modeling method of the effect of post-construction of PHB for discrete reinforcement and conducted a parameter study of the bond stress-slip relationship between concrete and reinforcements. The results showed that the effect of post-installation of PHB on the shear strength and cracking behavior could be qualitatively evaluated. In addition, the effect of post-installation of the PHB and the failure mode were analyzed by using the proposed modeling method in the three dimensional nonlinear material FEM analysis of a full-scale RC column member (more than 1 m thick) reinforced by PHB.

 A dynamic analysis employing the nonlinear single degree of freedom (SDOF) model is generally conducted in order to carry out a seismic design of railway bridge structures. A bi-linear type skeleton curve has been widely used to approximate the nonlinear behavior of the structure obtained from the pushover analysis. This backbone curve, however, does not necessarily express the true nonlinear behavior particularly if the damage level is small. In this study, the new skeleton curve employing the ellipse function was proposed to improve the precision of dynamic response in regions at around yielding. It was confirmed from non-linier analysis that the non-linier response estimated by the SDOF model with proposed curve showed good agreement with that from precise dynamic analysis.

 In the 2016 Kumamoto earthquake, strong seismic motions characteristic of inland crustal earthquakes and many cracks were generated on the ground surface along several fault zones. The water supply and sewer pipelines in Kumamoto were severely damaged by the earthquake, and although strong ground motions and liquefaction were the dominant causes of this damage, it is necessary to consider the effects of surface fault displacement observed in many areas. In this study, we extracted data from buried water supply pipelines in Mashiki and sewer pipelines in Kumamoto and Mashiki that were damaged by the Kumamoto earthquake, and analyzed the fragility characteristics of water treatment pipelines in relation to the surface fault displacement.

 In the 2011 Tohoku Japan Earthquake, liquefaction occurred in various areas of the eastern Japan. In the current liquefaction prediction, geotechnical survey data if employed, and it gives accurate results. However, it if difficult to apply this method to a wide area. Therefore, it if expected to establish a method which can easily evaluate the occurrence of liquefaction extensively. In this study, we aim to construct a liquefaction prediction model using support vector machine and random forests. Based on the results of the previous studies, the duration of seismic motion, which affects the occurrence of liquefaction, if newly added as an explanatory variable. In addition, the models are grouped according to the tendency of liquefaction occurrence based on the Japan Engineering Geomorphologic Classification Map.

 In a series of studies, the authors have developed metabolism columns capable of modifying theirs seismic performance while supporting axial forces. The Metabolism column structure has a double structure at the base of the column, with a replaceable part that is expected to absorb seismic energy as the outer shell, and a core part that supports the constant axial and shear forces inside the column.

 In this study, a new metabolism column with steel members as the replacable parts was proposed, and experimentally investigated its performance and the replaceability of the replaceable parts. As a result, it is found that the proposed structure has high seismic performance, and it is possible to metabolize the seismic performance of the structure by replacing the steel replaceable parts. In addition, it is confirmed that the proposed structure can improve the post-peak behavior after the buckling of the steel replacement parts because the core part can support the compressive axial force.

 The authors have proposed a new type “spread foundation” composed of micropiles and soilbags as a method of constructing a spread foundation on soft ground. By separating the piles and the footing, the response acceleration can be reduced, the pile-head joints can be omitted, and the diameter of the piles can be reduced. Moreover, the separation of the piles and the footing may reduce the damage of the footing and the piles and improve the recoverability against the vertical surface fault displacement. In this study, therefore, the displacement and cross-sectional forces of the proposed structure and the pile foundation under the vertical surface fault displacement were compared analytically. The analysis results showed that the bending moment of the footing and the response curvature of the piles can be suppressed significantly compared to the pile foundation, although the displacement at the track may be slightly larger in the proposed structure than in the pile foundation.

 From the revision of the Specifications for Highway Bridges in 2017, it was required to consider Level 2 earthquake ground motion for the Verification of the decks. In the calculation example corresponding to the Specifications for Highway Bridges, the verification result was shown when the deck bears 100% of the sectional force generated in the superstructure This design method may be significantly more unreasonable than the previous design method. In this study, partial FE analysis was performed using a solid element for the reinforced concrete deck and a shell element for the main girder. At the same time, a frame analysis using fiber elements was performed. Based on the analysis results, it was confirmed that the decks and the main girders were integrated to resist the lateral load. Then, the load sharing rate was evaluated.

 One of the ways of investigating the influences of soil liquefaction on the structural systems during a seismic event is by using a deterministic model based on finite element or finite difference analysis. However, a deterministic model does not consider the intrinsic spatial variability of a natural ground, which might have huge significance on the structural response. Little works have been done to assess the effects of spatial variability involving a liquefaction-induced lateral spreading phenomenon on the soil-structure interactions. In the present paper, a finite element analysis is carried out for the developed deterministic and stochastic models (considering spatial variability) to examine the differences arising from spatial variability in the backfill soil on the performance of a sheet-pile during seismic loading. The developed finite element model, with soil elements modeled using a strain space multiple mechanism model, was initially validated with the centrifuge model experiment to predict the accuracy of the deterministic model. A stochastic field using a discretized Gaussian distribution was considered for the realization of soil spatial variability through a relative density as a varying parameter. The results among the stochastic and deterministic models were in reasonable agreement, far away from the sheet-pile. On the other hand, closer to a sheet-pile, there were considerable differences in the generated excess pore water pressure among the two approaches, highlighting the importance of soil spatial variabilities involving soil-structure interactions for large deformation analysis. However, by adopting a lower and an upper bound for the deterministic analysis, such soil spatial variability effects can be reasonably considered during the seismic analysis, which resulted in close agreement for the mobilized sheet-pile head deformations.

 After an earthquake, quickly identifying damage on bridges is crucial to early recoveries. However, current method of structural health monitoring on bridges rely on cameras, cable networks, and manpower. These methods require high costs and also lead to slower recovery effort. In order to address these issues, a health monitoring model of a bridge bearing and a pier using neural networks and accelerometers were proposed. Such a model ensures real time evaluation of bearing and pier damage while using only the acceleration responses of a bridge. In order to evaluate the bearing damage, a neural network was proposed with acceleration responses of girder and pier top being the input while the output being bearing displacement. In order to evaluate the pier damage, first a neural network was proposed with acceleration responses of footing, girder and pier top being the input while the output being footing displacement. Then a neural network was proposed with displacement responses of footing, pier top and acceleration responses of girder being the input while the output being pier curvature. Several different combinations of seismic motions were considered as the learning data set. The results demonstrated that the neural network estimated the bearing displacement and the pier curvature with high precision.

 In the previous study, focusing on the self-organizing ability of the neural network, it was shown that it is possible to model the nonlinear historical restoring force characteristics without using existing mathematical models when the load-displacement relationship obtained by giving a regular wave that gradually increase and decrease as a forced displacement is used as the training data. Therefore, in this study, we performed dynamic analysis using more complicated and random artificial waves as acceleration data. It was confirmed that the same modeling is possible by using the load-displacement relationship obtained in this way as training data. We also examined a method that improves estimation accuracy by using 10 unlearned artificial waves and 12 designed seismic motions as verification waves and performing dynamic analysis via a trained neural network.

 Beyond Most Consider Earthquake is considered as one of the most important issues need to be considered for seismic resilience of bridge system. Resilience or Anti-Catastrophe is asked to be taken into account in the recent seismic design specification. Though there is less information or practical approach deliver those concepts. As one of the proposals, it has been found as with good performance to use a series damper CaSS in which a speed-dependent damper and a history-dependent damper are connected in series. Analytical studies to date have revealed that the functionally decentralized bridges using CaSS performed quite well in seismic performance, and seismic risk reduction. However, dynamic loading test experiments for practical use have been clarified. Verification by real time hybrid simulation is indispensable. In this study, the seismic performance of bridge install with CaSS, a Cylinder and Shear Panel Seriels Damper, was investigated by conducting real time hybrid simulation test.

 Application of high-damping seismic isolation rubber bearings to bridges in cold regions raises concerns about the effect of low temperature on the hysteresis characteristics of the rubber bearings and the resulting detrimental effect on the seismic performance of the isolated bridges. In the low temperature environment, the stiffness and damping of the high-damping rubber bearing increase significantly. And this is also accompanied with the influence of internal temperature change due to self-heating, resulting in complex historical restoring force characteristics varying with time. In this study, a series of substructure hybrid simulation tests were conducted to simulate the seismic response of a bridge structure, using a loading system that can test a high-damping rubber bearing specimen under low temperature conditions by using a thermostatic casing and air cooling system. The test results indicate that the maximum response displacement and acceleration of the bridge piers increase with decreasing temperature in the low-temperature environment compared with the room temperature environment, and the seismic action that acts on the piers is larger than that assumed in the design at the room temperature.

 The authors developed a mechanical type of seismic resistant steel pipe joint, which has “joint strength equivalent or superior to that of welded steel pipe” and can be connected easily and reliably without depending on the welding skill of workers, instead of welded steel pipe for water supply, and verified the tensile performance of the joint in the previous paper. In view of the fact that the method for verifying the seismic resistance of joint of the pipe attached to the bridge has not yet been established, in this study, the seismic performance of the joints at the pipeline attached to the bridge was reviewed, and a method for calculating the response value of the joints was proposed using the current standard (static calculation). In addition, dynamic analysis was conducted on various existing bridges where the joints are installed, using beam spring elements to model the bridge and the attached pipeline, and the validity of the method for calculating the static response values of the joints was confirmed. It was also confirmed that the developed seismic resistant steel pipe joints had seismic performance.

 Steel ring restrainer (SRR) with rectangular section is a new type of restrainer to prevent the unseating of bridge spans. In the present study, a parametric study on the influences of the geometric dimensions and steel grades on the static behavior of the SRR was conducted after the experimental and numerical investigations. In addition, empirical equations predicting the force-displacement relationship of the SRRs were derived. The results show that all of the geometric dimensions and steel grades affect the static behavior of the SRRs. Among them, the sectional area and steel grades have the most remarkable effect on the ultimate strength and tangent stiffness, while the radius of the curved part most significantly affects the ductility of the SRRs. Moreover, the empirical equations have good precision to assess the static curve of the SRRs.

 In this study, in order to simulate the occurrence and growth of ductile cracks in structural steels in the high stress triaxiality region, tensile tests were conducted on test pieces with notches, having different notch radii and notch angles. The test specimens were made of SBHS, a type of steel for high performance structures, as well as two types of conventional structural steels SM570 and SM490. By comparing the effects of different notch radii, notch angles, steel grades, and chemical compositions, mechanical properties, crack initiation, and its propagation up to fracture were clarified.

 In this study, a three-step, two-parameter ductile fracture model was employed to simulate crack growth of steel members. First, it was examined whether the method of correcting the damage initiation parameter for 1 mm meshing was applicable to unstiffened box section piers based on the results for 0.5 mm meshing proposed for T-type welded joints. Pushover analysis was also conducted to investigate the effect of mesh partitioning on non-fracture analysis under monotonic loading. In addition, fracture analysis was performed using values of parameters obtained from the pushover analysis and corresponding results were compared with experimental results.

 For bridges where the effects of liquefaction in the waterfront should be considered, the foundation is generally checked for the action of force by liquefaction. If the upper and lower connections of the bridge have a rigid structure, the permanent displacement of the foundation due to liquefaction may affect the seismic resistance of the bridge and its serviceability after an earthquake. In this study, the effect of permanent displacement of the foundation due to liquefaction was evaluated by combining the effective stress analysis of the ground-foundation and the dynamic analysis of the structure for the elevated bridge in the coastal area. First, the effective stress analysis by FLIP was performed to calculate the permanent displacement of the foundation. Next, using the three-dimensional frame structure model of the bridge, the permanent displacement of the foundation was forcibly input to the top of the foundation as an action following the seismic motion, and the bridge was checked for the required performance. In addition, the response due to live load (fluctuation action) was calculated for the bridge after the forced displacement input, and the serviceability after an earthquake was considered.

 This study proposes a method for simultaneously simulating strong ground motion distributions of horizontal two components (Fault-Normal and Fault-Parallel components) while preserving the correlated spatial variation structure in two components. First, singular value decomposition (SVD) analysis is applied to a cross variance matrix consisting of strong ground motion distributions of horizontal two components. The SVD analysis provides the modal forms representing spatial characteristics with strong correlation in two components and the principal component scores that characterize each strong ground motion distribution. Second, the principal component scores are replaced by vectors preserving the covariance structure of two components, continued by synthesizing vectors and modal forms to simultaneously simulate the strong ground motion distribution of two components. The study results show that both the method of Cholesky decomposition applied correlation coefficient between principal component scores of two components and the method of generating difference in principal component scores of two components by random simulation are able to simulate strong ground motion distributions that reproduce the correlation between horizontal two components.

 In order to simulate the real part of Fourier transform of acceleration time history, we developed a method to extract the non-stationary characteristic of the real part by smoothing the absolute value of the real part, which is named as a mean trend of the real part. The real part divided by this mean trend is named as the standardized real part. We investigate a stochastic characteristics of this standardized real part such as auto-correlative function with respect to the circular frequency and probability density function of the difference of standardized real part for several circular frequency intervals. Based on these functions we can conclude that the standardized real part has the fractal characteristic and it is possible to develop a method to simulate a sample standardized real part. Once we can estimate the mean trend of real part of observed acceleration time history we can obtain many samples of the real part from an observed acceleration time history by multiplying the mean trend to many simulated standardized real parts. Therefore we develop regression equations to model the mean trend of the real part as the function of the earthquake magnitude, the hypocenter distance, the hypocenter depth and the average shear wave velocity within 30m depth. If we can simulate a sample real part we can easily obtain the imaginary part provided the causality for acceleration time history, then a sample acceleration time history can be simulated by the inverse Fourier transform.

 In this study, in order to reflect the change of the hysteresis characteristic of the high damping rubber bearings to the seismic response, a pseudo-dynamic simulation system using experimental equipment capable of loading test at low temperature was developed. The pseudo-dynamic simulation system was developed by using open source UI-SIMCOR. To enhance the usability of the system, sub-program for static response analysis was also developed for the application of a versatile FEM software. As the results, it was possible to incorporate into the response analysis that the hysteresis loop of the bearing changed as the vibration progressed. And the nonlinear hysteresis characteristic of the pier bottom can be expressed.

 We analyzed the effect of source parameter settings on spatial characteristics of strong ground motion intensity depending on period and orthogonal directionality. The mode decomposition technique was applied to six hundred cases of absolute acceleration response distributions of fault normal and fault parallel components for various periods using strong ground motions simulated for a strike-slip fault. Modal decomposition results were modeled with source parameter settings using a random forest in machine learning. The dominant factor of spatial characteristics was evaluated based on explainable AI which are interpretation methods for machine learning models. Mode 1 represents the attenuation characteristics. Mode 2 and Mode 3 mostly represent the overall intensity level due to perturbated seismic moments, arrangement of asperities and location of hypocenter. The modal characteristics were found to differ by periods and components.

 A steel cable-stayed bridge, Kuwazuru Ohashi, located in a mountainous area was damaged during the 2016 Kumamoto earthquake. The bridge is characterized by having curved girders and unequal spans, and the damage was caused by these structural characteristics. In this study, in order to clarify the cause of the damage to Kuwazuru Ohashi, self-weight analyses and non-linear dynamic analyses were conducted with a straight girder model and an equal span model in addition to an unequal span curved girder model which is the damaged bridge. A series of analyses confirmed that the curved bridge girder was subjected to a force acting towards the outside of the curvature of the girder. Also, an equal span girder has the uplift force in the bearings under self-weight, and this uplift was magnified by the earthquake force. Unequal span girders tend to rotate under earthquake, and curved girders also exhibited a rotational behavior.

 A pendulum-type seismic isolation bearing called a Spherical Sliding Bearing (SSB) is the focus of this research. SSB offers some benefits as a seismic isolator, such as self-centering nature and independent period of the mass of the supporting structure. SSB is usually modeled as a bilinear model in nonlinear analyses; however, a frictional coefficient of SSB has a dependency on surface pressure, velocity and temperature. These factors should properly be modeled in the analyses to design SSB. In this study, a series of shaking table tests using a single SSB was simulated using the model that considered the pressure and velocity dependency on the frictional coefficient. As a result, it was found that the proposed model was able to simulate the experimental results with reasonable accuracy by considering the effects of the pressure and velocity dependency on the friction coefficient.

 In this paper, we investigated the bulging vibration characteristics of non-earthquake resistant FRP water tanks that were manufactured before the seismic design standard for tanks was established in 1980 and developed damping device against bulging vibration. We carried out vibration experiment using a non-earthquake resistant tank. The damping device was attached to corner of the tank, because bulging vibration cause damage particularly to there. As a result, it was found that by damping device, deformation of the tank’s panel was decreased. In addition, we confirmed damping effect, reducing repeated occurrence of large displacements and large accelerations to the tank by performing rainflow analysis.

 In this study, we aim to develop a column that exhibits a self-centering only during restoration process in order to achieve both self-centering mechanism and hysteretic damping. We used the metabolism column structure proposed in the past as a reference. The metabolism column structure consists of a permanent part that always supports the axial force and a changeable part that absorbs energy during an earthquake. Specifically, we proposed a new structure using concrete hinges as the permanent part, which has a self-centering mechanism, and verified its feasibility through numerical analysis. As a result of the numerical analysis, the energy absorption performance of the proposed structure during the earthquake was confirmed by the plasticization of the commutative part. In addition, earthquake response analysis was conducted to generate residual displacement of the proposed structure after the earthquake, and dynamic analysis was conducted to understand the response at the time of the removal of the replaceable part. As a result, the selfcentering mechanism of the permanent part was confirmed.

 In this study, the effect of omitting the existing caisson and its construction process to simplify the seismic response analysis by FEM is investigated for an improved and deepened gravity-type quay wall by sheet piles with anchor piles. In the omission of the construction process of the existing gravity-type quay wall, stress transfer to the seabed at the time of caisson installation cannot be evaluated, and the confining pressure of the seabed in front of the sheet pile after deepening improvement was evaluated as small. The influence of the omission of the construction process was not small since the overall displacement behavior of the deepened quay wall was evaluated as larger due to the smaller seabed resistance against the displacement of the sheet pile. In the case of omitting the modeling of the existing caisson, the locally large earth pressure on the sheet pile near the caisson bottom is no longer represented, and the bending deformation of the sheet pile was evaluated to be smaller.

 In current treatment of management system, the structural replacement including replacement of rebars is conducted when the corrosion is severe. However, it is not easy for column structure to replace corroded rebars because it requires the installation of timberings. In this paper, we aim to develop the metabolism RC column structure that can maintain the structural function under the corrosive condition by facilitating the replacement of rebars under axial force support. The proposal structure is made of two parts, exchangeable part and lasting part. The exchangeable part allows the corrosion of its longitudinal rebar. We replace exchangable part and attach new one when initiating crackings appear. The lasting part supports the axial load when the exchangeable part is replaced. We make four specimens, one is normal RC and other three specimens have the proposal structure. The controlled variables in the test are corrosion level and presence or absence of the bond between exchangeable part and lasting part. Replacement experiments and cyclic loading tests are conducted. Test results show that rebar replacement with axial force support is possible independent of corrosion level, and replacement with axial force support has no effect to the restoring force characteristics. The lack of the bond between exchangeable part and lasting part in replacement experiment changes crack characteristics. Shearing cracks open lager when the bond is lack, so it is preferable to ensure the strong bond considering the control of shearing cracks.

 When constructing civil structures, it is said that anti-catastrophe performance should be taken into account at the stage of structural planning. However, a structural planning for anti-catastrophe performance has not been established. Therefore, in this paper, we propose an anti-catastrophe performance structural planning for a continuous truss bridge. In the proposed method, firstly, we identify the most important elements of the bridge structure by the robustness index. Secondly, the mechanical skeleton, which is a set of components that have a large impact on the load-bearing mechanism, is selected for the structure lacking the identified most important elements by using graphic statics. Thirdly, the load-bearing capacity of the structure is then verified by comparing the stresses in the components of the key structure with the allowable stresses. If any member exceeds the allowable stress, we take measures in order to keep the stresses of all the members of the key structure within the allowable stress. This method clarifies the load carrying capacity of a continuous truss bridge under non-standard design situations and enables the structural planning for anti-catastrophe performance.