Based on the results of numerous geotechnical investigations, we have developed standard geotechnical information database that can efficiently and adequately represent the characteristics of surface earthquake motion. Specifically, using the results of many geotechnical surveys, we classify the ground by clustering using the natural period T_g and the strength of ground K_f^’ as indices, and extract ground information representative of these classifications. As a result, it was confirmed that the surface earthquake motions calculated using the ground information for the 50 sites selected in this study were in good agreement with the probability distribution of those motions calculated using all ground information in Japan. Furthermore, it was shown that the surface earthquake motion can be efficiently and adequately evaluated without constructing a new analysis model by effectively using the nationwide data of seismic response analysis of ground constructed in this study.

 There are various possible causes of the Aso Bridge failure, such as earthquake ground motion, slope failure, and ground displacement. Here, we evaluate the effect of primary and secondary soil failures near the Aso Ohashi Bridge, which is one of the most likely causes. Based on the topographic changes before and after the earthquake and measurement of vertical displacement by drone, 510 m² of soil per unit width (61,200 kN for 8 m width) is considered to have been transported downstream near the arch by the secondary and primary collapsed soils. It can be pointed out that the movement of these sediments may have caused the arch bridge to collapse.

 There are many railway bridges with rocking piers in urban areas. Preventing collapse of those bridges during earthquakes is an urgent concern. It is also important to improve the recovery performance by controlling the response displacement of the girders. However, to achieve both goals, it is necessary to install two different devices, damping devices and bridge collapse prevention devices, which is sometimes difficult due to limitations of space around the girders. Therefore, we developed a space-saving device with damping and bridge collapse prevention functions. We firstly confirmed the nonlinear characteristics by an elemental experiment. Then we verified the damping function, the bridge collapse prevention function, and the girder attachment part on an actual bridge by numerical simulations.

 Construction of a 3D frame model is effective as a method of analytically evaluating the entire structural system, and there are many examples of evaluating a specific group of structures. However, in design practice, it is necessary to consider the number of degrees of freedom of the model in order to evaluate the seismic interaction behavior of long bridges and viaducts. Therefore, we investigated a modeling method that can express the seismic interaction behavior of bridges and viaducts simply and appropriately. Specifically, based on the model of the design vibration unit used in seismic design, a simple frame model was constructed by connecting them, and the response was compared with the 3D frame model by frequency response function and response waveform. As a result, it was found that the frequency response function and response waveform can be roughly expressed even with a simple model in which columns and frames are aggregated into mass points, if the rotational behavior around the vertical axis at the bearing is expressed.

 Earthquakes frequently induce landslides and slope failures which trigger many communities to be isolated. In this study, we proposed an estimation methodology for detecting isolated communities in mountain regions using slope failure probabilities during earthquakes. This methodology was constructed of the Structural Equation Modeling and the Logistic Regression Analysis using the disaster prevention charts and the stability survey tables. The SMOTE (Synthetic Minority Over-sampling Technique) was introduced for estimating slope failure probability more accurately by increasing the failure data equivalent to the non-failure one. Furthermore, we evaluated the community isolation risk in Wakayama prefecture based on the proposed road network disruption probability. Finally, we revealed the detecting method for the economic slope failure countermeasure sites in one sample case.

 When designing a rubber bearing that has a structure in which rubber and steel plates are bonded together by adhesive, it is extremely important to prevent adhesive delamination from occurring before the rubber breaks. The road bridge bearing guidelines require that the 90° peel strength be 7 N/mm or greater. However, the actual internal stress state of rubber bearings under horizontal displacement has not yet been clarified, and differs from the stress state obtained from the 90° peel test. Therefore it seems that there are potential problem of not knowing the physical meanings of the limit values of the 90° peel test.

 In this paper, the internal stress state of four types of rubber bearings, a 90° peel strength test specimen, and a single lap shear test specimen were subjected to FEM analysis that took into account hyperelastic material parameters and adhesive layers. Better evaluation method of adhesive delamination was considered based on the results that internal stress state of each model was clarified and compared.

 In this study, the particle breakage behavior of a volcanic ash coarse-grained soil, which is easily broken by external forces, was determined by elemental mechanical tests (consolidation, drainage torsional shear test, and isotropic consolidation test) and a model embankment shaking disturbance test using a shaking table, in order to understand the particle breakage behavior by drainage torsional shear and isotropic consolidation and by the collapse of the model embankment by particle size tests. The results of various grain-size tests showed that the increase factors of the content of various grain-size fractions in the drainage torsional shear process and the slip surface of the model embankment after collapse in the elemental mechanical tests were qualitatively compared, and it was found that the increase factors of the content of various grain-size fractions in the drainage torsional shear process and the slip surface of the model embankment after collapse were large for medium sand fraction, fine sand fraction and fine grain fraction, especially the fine sand fraction showed high increase factors, showing the same tendency.

 The location where the bridge construction is planned has a shatter zone due to past fault activity. When an earthquake occurs due to fault activity, permanent displacement of the foundation ground due to fault displacement is predicted. Bridges are required to prevent serious damage in order to maintain their functions even when fault displacement occurs. In this study, we focused on a bridge planned at a place where a fault exists in the vicinity but the location is unclear. In addition to grasping the displacement followability to fault displacement by push-over analysis, nonlinear time history response analysis was performed using input seismic ground motion including fault displacement generated based on fault information. As a result, it was clarified that a bridge type with excellent displacement followability against fault displacement is not necessarily structurally advantageous against superimposed seismic motion.

 The 2011 off the Pacific coast of Tohoku Earthquake and the 2016 Kumamoto Earthquake caused liquefaction in reclaimed land, which led to damage such as settlement and inclination of many direct-foundation buildings. In this study, the mechanism of building damage due to liquefaction was numerically investigated by considering the spatial variability of soil properties inherent to the natural ground and limiting the study to one direct-foundation building without considering the influence of adjacent buildings. The analytical results have demonstrated that the influence of spatial variability of soil properties cannot be ignored in evaluating the settlement and inclination of a direct-foundation building due to liquefaction. The dissipation process of excess pore water pressure after shaking differs from point to point in the heterogeneous ground, which induces inclination damage to the building even when there is no tilt in the base or ground surface and the earthquake motion is positively and negatively symmetrical.

 Previous studies using model tests and analyses have revealed that the floatation of buried pipe was triggered by the buoyancy caused by liquefaction and floatation amount is caused by that the ground around the pipe moves to the bottom of the pipe. Despite advances in numerical analysis technology, there are limited methods to accurately evaluate the soil particles’ moving phenomenon. In addition, most of the existing model tests were conducted with horizontal excitation to the cross section of structure. In this study, horizontal excitation tests were conducted in both the pipe cross section and the pipe axis plane under the same underground conditions, in order to evaluate the effect of excitation direction on the floatation amount of buried pipes. When the pipe was not affected by near-surface sloshing, the floatation amount was 0.5 to 0.87 times smaller when the pipe was excited in the axial direction than when it was excited in the direction of cross section.

 Load eccentricity and inclination occur in shallow foundations via the combination of horizontal inertial force and vertical dead load during an earthquake. Although a decline in the ultimate bearing capacity under eccentric and inclined loads has been reported, the evaluation method used should be analyzed to determine whether it is applicable to cases involving earthquake loading. Moreover, the relationship between horizontal loading and vertical displacement has not been revealed; therefore, a quantitative evaluation method to determine the relationship must be developed and verified. In this study, we conduct a horizontal reciprocal loading test using a pier model of shallow foundation simulated based on the condition of earthquake loading. We considered a few methods for evaluating the ultimate bearing capacity and parameters which determine the relationship between horizontal loading and residual settlement.

 Various equations have been proposed to evaluate shear modulus as a function of pore ratio and effective confining pressure for seismic response analysis, but most of them have been applied only to sand and clay with uniform grain size. In this study, we attempted to evaluate the shear modulus of local soils with varying fine-grain content (0-75%), which are presumed to have been liquefied by the 2018 Sulawesi earthquake, by conducting bender element tests on specimens of local soils with high non-plastic fine-grain content, and calculating shear modulus. The shear modulus of soil with a wide range of fine-grain content was evaluated using the equivalent skeletal pore ratio, which considers that a part of the fine-grain content contributes to the skeletal structure of the coarse-grain content, instead of the normal pore ratio.

 The purpose of this study is to perform immediate damage detection of the instrumented structure during a large earthquake based on the machine learning of the linear response recordings due to the frequently observed small and medium earthquakes. Preparing a model of the structure that considers nonlinearity with trilinear model, both linear and nonlinear responses are calculated by giving input ground motions of different strength. Then, the autoencoder is trained with linear response records, and weights of the network are determined. By applying the autoencoder to several response recordings of different nonlinear levels considering large earthquakes, the value of the obtained reconstruction error as an anomaly index showed variation according to the damage level of the structure. It was found that immediate detection of structural damage caused by a large earthquake may be possible by using nonlinear response recordings.

 We propose a method for efficiently identifying observation points through ground motion’s spectral ratios using deep learning with convolutional neural networks (CNN). In this method, the observed acceleration spectrum is converted into a color spectrum associated with the amplitude. First, random waves were applied to multiple one-dimensional numerical model grounds, and the applicability of this method was examined using the acceleration Fourier spectrum of the ground surface response converted into a color spectrum. As a result, the model grounds were identified with an accuracy of 99% or more. Next, when using the H/V spectral ratios of seismic ground motions of less than 50 gal obtained at eight K-NET stations, the stations could be identified with an accuracy of 95% or more. The misclassified seismic motions had some characteristics such as long hypocentral distances. Furthermore, when the microtremor H/V spectrum ratio was input to the trained CNN, the accuracy was as low as about 50% on average with large dispersion.

 In this study, we attempted to evaluate the behavior of RC culverts with bends buried underground when one of the seismic joints is installed asymmetrically so that it is close to the bend and when the loading direction is changed. As a result, it was confirmed that when the seismic joints are asymmetrical, the damage to the RC culvert body is suppressed by concentrating the deformation on the seismic joint located close to the bend. In addition, it was confirmed that no significant damage occurred near the bend regardless of the loading direction, while the most severe damage was observed on the wall surface of the general section perpendicular to the loading direction.

 In earthquakes caused by active inland faults, fault displacement that appears on the ground surface and inertial force may affect to seismic behavior of structures at the same time. However, the seismic behavior of structures affected by inertial force and fault displacement is unexplained. In this study, shaking table test was conducted on a steel frame model subjected to inertial force and fault displacement were applied simultaneously to understand the behavior of the model under the simultaneous action of inertial force and fault displacement. As a result, it was clarified that the influence of fault displacement on the dynamic response of structures may not be negligible. Furthermore, a reproduction analysis of shaking table test was conducted, and validity of the analytical method that can consider to the effects of inertial force and fault displacement was clarified.

 The design values for soil strength used in the seismic diagnosis of existing railway embankments are determined based on laboratory soil tests of samples taken from them and density logging. The conventional design values cannot take into consideration the variability of the existing embankments such as the denseness caused by the cyclic loading of the train, so it is due to the sampling location that is away from the railway tracks. In this study, to advance the seismic diagnosis method, the design values considered the unsaturated strength of the materials and the shear wave velocity distribution obtained by the surface wave method were evaluated. As a result, it is possible to estimate the density distribution in the existing embankment by the surface wave method. In addition, the design value resistance improves considering the unsaturated strength characteristics of the embankment materials. It is possible to make a more rational seismic diagnosis.

 Cyclic loading tests on the reinforced concrete bridge pier models repaired after damage were conducted to evaluate the seismic performance of reinforced concrete bridge piers after repaired damaged due to earthquake. The bridge piers in this study do not satisfy current seismic performance. In this study, cyclic loading was conducted to damage the column bases of the model, at first. The damage level was set to a level at which the bridge functionality could be restored as soon as possible through repair. And, the model was repaired, in which injecting resin into the cracks and jacketing them with aramid fiber reinforced plastic sheet. Then, cyclic loading test was conducted again to evaluate the seismic performance of the repaired the model. From this study, the following results were obtained: (1) toughness is improved in the pier model repaired after the damaged; (2) energy absorption performance was also improved; (3) the horizontal load-carrying capacity of the pier model satisfied the seismic horizontal strength of specifications for road bridges;(4) at the damage levels given in this experiment, the current seismic performance could be maintained even with post-damage repairs.

 Since the number of deteriorated bridges has increased recently, there are concerns about severe damage to them by the strong earthquakes. In the present study, a series of shaking table tests was conducted in order to evaluate the seismic performance of existing bridges reinforced by EPS blocks. The test results showed that the residual settlement of backfills and the horizontal displacement of abutments were restrained significantly by the reinforcement. However, the increase in the horizontal displacement of the pier was confirmed due possibly to the earth pressure, which was acting on the abutment, propagated through EPS blocks.

 In the April 2016 Kumamoto earthquake, a moment magnitude 6.2 earthquake occurred in the Kumamoto region of Kumamoto Prefecture, Japan, and a moment magnitude 7.0 earthquake occurred shortly after about 16 hours later in the same region. In this study, we attempted to construct a damage discrimination model using aerial laser survey data as an efficient and safe method to assess the damage to buildings caused by the earthquake. Convolutional neural network (CNN), one of the algorithms of deep learning, was applied to the aerial laser survey data collected after the main shock, and the best model was investigated by changing the network configurations. As a result, a model with a correct response rate of over 90% was constructed.

 Structures located along the coastline, depending on the importance of the facility, it is necessary to ensure safety against tsunamis generated by a major earthquake. It is important to prevent structures from being damaged by the tsunami impact, which would make it difficult to restore the facility functions.

 The tsunami load includes both inertia and drag force, but inertia force has a large effect on the impact wave pressure, and the angle of impact and the side slope of the structure can have a large reduction effect.

 The authors have conducted a tsunami model experiment to confirm this reduction effect, and in this study, the experiment was reproduced and analyzed from the viewpoint of understanding the phenomenon and complementary validation. The phenomena are then discussed by comparing the results of the analysis and the experiment.

 In the 2016 Kumamoto earthquake, the bridge-pipeline-ground coupled systems had a great deal of substantial damage, and the damage mechanism of these coupled responses are required to be clarified. The characteristics of the coupled responses of the system were clarified when the strong motions equivalent to the main earthquake acted on a typical bridge-pipeline-ground coupled system located in Mashiki Town. The results revealed the following: 1) the response of the pipeline is suppressed at the center span of the bridge, but increases near the abutments and pier; 2) the generation of axial stress in the bridge axis direction due to different coupled vibrations between the abutment backfill, bridge girder, abutment and pier may contribute to the damage of the pipeline near the abutments; and 3) the response of the pipeline near the pier increases due to the relatively larger vibration of the bridge girders than that of the pier and pile foundation.

 Similarity evaluation of seismic waveforms is one of the most important aspects in earthquake engineering and seismology. Recently, Wasserstein metric has been proposed as a new index for similarity evaluation of seismic waveforms, and although Wasserstein metric has been shown to be effective in a certain field, there has been no researches on its application as an index for waveform similarity evaluation in earthquake engineering. In this study, we applied Wasserstein metric to semblance analysis and compared it with the conventional method using the mean square error. The conventional method required a global search with high computational cost such as grid search due to the problem of multimodality, but when Wasserstein metric is used as the criterion function, it is shown that there is a certain degree of convergence to the globally optimal solution even with only local search with low computational cost.

 In the design for level 2 earthquake, Specifications for Highway Bridges states that if the seismic response characteristics can be evaluated appropriately, it is possible to consider nonlinearity in multiple types of members, such as seismic isolation bridges. However, the specific requirements and verification methods for that purpose are not indicated. To clarify these points, it is necessary to clarify the effects of various uncertainties on seismic response of bridges. In this paper, by dynamic analysis of two patterns of structural systems using seismic isolation bearings or seismic control dampers, the effect of the post-yield stiffness of bearing part on the relationship between the uncertainty of member properties and the seismic response was investigated. As a result, it was shown that when the post-yield stiffness of the bearing part is smaller than that of the seismic isolation bearing, the reliability of the response evaluation tends to be lower than that of the isolated bridge.

 A single spherical sliding bearing is a seismic isolation bearing in which a slider slides on a concave sphere under the influence of friction, and its friction has a sizeable impact on the dynamic behavior of a structure. The spherical sliding bearing has a dependency on velocity, temperature, and surface pressure. In order to understand the dynamic behavior of a structure having single spherical sliding bearings, it is necessary to clarify the influence of different frictional coefficients of the sliding surface on the dynamic response, and frictional characteristics should be appropriately evaluated and incorporated into the dynamic analysis. In this study, shaking table tests were conducted using two different types of sliders with different frictional coefficients, low and medium frictions, and dynamic analyses were conducted considering the dependency of the frictional coefficients on each type of slider. As a result, it was confirmed that the acceleration and displacement responses were smaller for the low-frictional type than the medium one due to the effect of friction. The experimental results were simulated with relatively high accuracy by considering the velocity dependency.

 In the Kumamoto earthquake in April 2016, the heavy damage of truss bridges caused by ground deformation was not reported, although many other types of bridges were seriously damaged due to ground change. However, as a result of continuous analysis of the case that the ground slides near the abutment, it has been found that a small amount of ground deformation can cause severe damage to lower member of truss bridge.

 Thus in this study, we carried out elasto-plastic static analyses and seismic response analyses for Warren truss bridge at the time of ground deformation. At First, forced displacements in the compressive direction were applied to the lower members, and the damage and deformation of the truss bridge were investigated by elasto-plastic static analyses. Thereafter the seismic response analyses were carried out on the model with forced displacement as an initial imperfection, and it was confirmed how vulnerable Warren truss bridge was to seismic motion due to initial imperfection.

 During the Fukushima Prefecture earthquake that occurred in March 2022, a lot of damage to the middle beams of two-story RC viaduct was confirmed. Therefore, it is important to understand the changes in the structural properties of two-story RC viaduct when the middle beams are damaged. In addition, it is not clear how the damage to the middle beams of two-story RC viaduct affects the train mobility. The fact means that the quantitative relationship between the structural performance and the level of service provided to society is not clear. If such quantitative relationship is provided, the development of new structural technology and its implementation in society will be stimulated. Therefore, this study evaluates the seismic resistance to two-story RC viaduct after damage to the middle beam, and presents a verification process of the relationship between structural performance and level of service in order to quantitatively evaluate the train mobility of two-story RC viaduct after damage to the middle beam.

 A collapse scenario design method has been proposed to realize a road bridge that does not lose its functionality or can be restored quickly under overload conditions, and RC bridge piers with strength-stratifying rebars have been considered as a means to realize this method. As part of the study, dynamic analyses of 1, 200 cases of RC piers and strength-stratified piers with varying values of material and geotechnical properties based on the current standards were conducted to investigate their effects on the scenarios. As a result, it was confirmed that the current RC piers were designed to achieve the desired scenario of plasticization of the pier bases with more than 90% reliability against level 2 earthquake motion. On the other hand, for excess seismic motion, most of the piers not strength-stratified exceed the limit state 3, but the strength-stratified piers can be guided to a scenario that avoids collapse with more than 90% reliability.

 The behavior of embankment structures during an earthquake can be evaluated with high accuracy by grasping the vibration characteristics and the dynamic deformation characteristics of the constituent materials in detail. However, there are few seismic observation examples of embankment structures. Therefore, we examined the natural period and damping characteristics of the embankment structure during an actual earthquake, and the dynamic deformation characteristics of the constituent materials. In this study, the system identification based on the subspace method was carried out for the river embankment where seismic intensity of about 6 Upper was observed in the 2011 off the Pacific coast of Tohoku Earthquake. The dynamic deformation characteristics of the embankment material were estimated by evaluating the temporal changes in the natural period and damping characteristics of the embankment structure. The estimated results generally agreed with the dynamic deformation characteristics evaluated from the ground investigation.

 The damping characteristics shown in the Specifications for Highway Bridges and their explanations are specified based on past experimental results. The calculation results of damping characteristics using seismic observation records of actual bridges are not directly reflected. The attenuation characteristics of highway bridges are not sufficiently verified due to the lack of actual measurement records. Therefore, we thought it necessary to verify the set values of damping characteristics based on actual measurement records. In this study, using a highway bridge as a case study, we calculated the natural frequency and damping characteristics by system identification based on the subspace method using the records observed at multiple points in the entire bridge system. Furthermore, this study suggests the possibility of calculating the natural frequencies and damping characteristics of bridge components such as the ground and bearings by using system identification.

 A highway bridge has a complex behavior of the whole system. The challenge was to improve the seismic behavior observation system. This study aims to clarify the seismic behavior of the entire highway bridge system. In addition to installing MEMS-type acceleration sensors at multiple locations on the highway bridge, wireless communication suitable for observing the seismic behavior of multiple points is installed. We have developed a strong motion monitoring system that observes the complex behavior of the entire bridge system. By constructing a communication system and relay transmission suitable for handling a large number of sensors, the observation system enables near-real-time multi-point continuous observation of bridges that can collect a large number of observation records wirelessly outdoors. The records observed by the strong motion monitoring system were sufficient for waveform analysis. Furthermore, the system was able to capture the complex behavior of the entire bridge system.

 The seismic performance of a multiple steel pipes bridge pier integrated by pile foundation without a footing is evaluated both experimentally and analytically, and a design method using a “beam-spring” frame model with columns and pile foundations as an integrated structure is proposed. On the other hand, in the field of road bridge foundations, research has been conducted for some time to take into account the variation of geotechnical properties due to differences in soil types and geotechnical investigation methods in design methods.

 In this paper, the effects of geotechnical uncertainties on the design of a multiple steel pipes bridge pier integrated by pile foundation without a footing are evaluated and compared with those of conventional RC piers and steel piers. The results show that the influence of the ground variation is comparable to that of the conventional pier type.

 When evaluating the seismic performance of large-scale structures, real-time hybrid simulation (RTHS), which couples the experiment part and analysis part, is an effective testing method. Considering application RTHS to large-scale structures, analytical model becomes complicated and calculation task increases. It may affect the testing accuracy because the actuator displacement deviates the ideal response. This study aims to examine the effect of the large calculation task on the RTHS accuracy. The result shows that the accuracy of velocity and acceleration in the experimental part may decreases as the calculation task in analysis part increases. This trend is remarkable when the response velocity level in experiment part becomes larger. This may suggest that it is necessary to take care the velocity level for evaluating large-scale structures in RTHS.

 In the design of cut and cover tunnels, it is essential to consider the interaction between the structure and the ground. In this study, we investigated the impact of the stiffness ratio between a box structure and the surrounding ground on the seismic surface forces (shear, vertical, and their eccentricity) generated during an earthquake. To do so, we conducted shear soil tank experiments under the condition that the box structure was fully supported by the support layer. Our results revealed that the stiffness ratio of the box and the surrounding ground negligibly affect the shear force generated when the box is fully supported by the support layer; however, it significantly affects the eccentricity of the normal force. A larger relative box stiffness results in a larger eccentricity of the lower slab, while a smaller stiffness the earth pressure distribution on the sidewall changes to a shape in the direction that resists shear deformation.

 Predicting the position of surface faults is the first step in counter-measures for fault displacement. However, it is difficult to estimate the region of secondary faults that accompany the primary fault activity. In this paper, the occurrence region of the secondary faults was estimated based on the rock mass stress, which was evaluated by ground motion analysis using large-scale FEM. First, we formulated a method for setting the plane source in the kinematic ground motion analysis using FEM. The plane source enables us to evaluate the response near the earthquake source fault, which is important in the evaluation of secondary faults. Furthermore, a ground motion analysis for the 2014 Nagano-ken hokubu earthquake was conducted and the relationship between the surface fault and the stress and strength of the rock mass was analyzed. The results show that the local safety factor, defined as the ratio of stress to strength, can be used to estimate the region where secondary faults are likely to occur for each earthquake source model.

 In the 2016 Kumamoto earthquake, we experienced two large ground motions to infrastructure. Even if the structure has sufficient strength against a preceding seismic load, the residual seismic performance against a subsequent seismic load is unknown. In order to cope with multiple seismic loads, it is necessary to clarify the relationship between the load history due to preceding seismic loads and the residual seismic performance. In order to examine the residual seismic performance of single-column RC piers, the authors conducted cyclic loading tests corresponding to preceding seismic loads and reloading tests corresponding to subsequent seismic loads. The parameters were set to the first loading range with reference to the limit state of the specification for highway bridges.

 For railways, it took time to assess the damage level and subsequent recovery work after the 2018 Northern Osaka Earthquake and the 2021 and 2022 Fukushima Earthquakes. For this reason, performance evaluations from the viewpoint of the number of post-earthquake restoration duration of structures will become more and more important in the future. Therefore, in this paper, we systematically organized post-earthquake restoration duration from past earthquake damage cases, referring to as many literatures as possible. As a result, we found that there is a limit to the number of cases that can be obtained, so we evaluated it by accumulating kinds of works required for restoration work according to the type of structure and damage level. Finally, we compared the estimation results with the recovery duration of the damage cases, and confirmed that the estimation results are generally close to the actual situation.

 Regarding the ground amplification characteristics, vertical motions tend to be less attention as horizontal motions. This is because many structures have been designed mainly considering horizontal motion. However, it is expected that the number of situations in which vertical motions should be adequately considered will increase, since seismic records with large PGA have been measured in recent years. In this study, the strong motion records of the 2018 Hokkaido Eastern Iburi earthquake were focused on and the surface ground amplification characteristics of vertical motions was examined. By comparing the strong and weak ground motion records observed at KiK-net stations, it was shown that the surface ground amplification characteristics of vertical motions differ between the P wave group and the S wave group. In particular, it was found that this tendency appears significantly during strong earthquake.

 Since 1867 when Yamate and Uchikoshi district of Yokohama City was opened to the public as a detention facility for foreigners, bluff retaining walls have been used as a countermeasure against cliffs. However, in the residential areas of Yokohama City, the deterioration of stone materials has progressed, and heavy rains have caused the collapse of bluff retaining walls. In this study, we investigated the deformation of the bluff retaining wall in Yamate area and conducted a model shaking table test in preparation for future mega-earthquakes and heavy rains. As a result, it was clarified that steep retaining walls are very dangerous and that reinforcement measures using anchors are effective.

 Inexpensive and compact IoT sensors were installed on an actual bridge and monitored. The bridge is a two-span continuous girder bridge with RC slabs and five steel main girders, and has been in service for 18 years. The IoT sensor uses a Raspberry Pi, a single-board computer. It has a camera and a range finder and can be connected to a network using a USB dongle, a data communication terminal. It can be remotely controlled via the network. The IoT sensor can be operated by generating electricity from solar panels, so it can be installed and operated by human power without using heavy machinery and without installing a power supply. This paper describes a plan for long-term measurement of cracks on the underside of RC slabs and the residual displacement of laminated rubber bearings using the IoT sensor. This paper reports the photos and strain results obtained during the first month of installation.

 During an earthquake occurred at off coast Fukushima in March 16, 2022, damages have occurred especially in Soma port and north area of Matsukawaura. We observed aftershock motions at several sites in Soma city in order to evaluate site amplifications where damages have occurred. It is found that almost all the sites show peak frequencies around 0.6 Hz and that the damaged sites show large peak amplitudes. It is also found that peak amplitude values have good relations with S-wave impedance values of the uppermost surface layer.

 This study aims to improve the recovery performance of bridge columns after being damaged due to an earthquake and also proposes a PC column structure that reduces residual displacement by prestressing. This proposed column enables a quick repair of the damaged column by arranging a steel tube in the core of the cross section. The seismic performance and recovery performance of the proposed column were verified by conducting cyclic loading tests. The test results showed that the residual displacement was not reduced enough to improve the recovery performance. After the damage of the column due to cyclic loadings, almost no damage, such as fracture or buckling, was found in the steel tube, which means that the core of the cross-section can support the structure above. Therefore, the proposed structure can quickly be repaired after being damaged if the residual displacement can be reduced. The analysis using Takeda model simulated the experimental results reasonably well. However, there needs some improvement in the analysis for PC columns because the Takeda Model cannot consider the increase of axial force in prestressed tendon with the increase of the column deformation.

 Though in the past research, the effect of slip behavior by the difference in the displacement and the difference in the surface treatment is shown on the high strength bolt friction joint which is cyclic loaded by earthquakes, the effect by the difference in the loading velocity is not well understood. Therefore in this study, for the purpose of clarifying the effect, the monotonic and cyclic loading experiment was carried out under the same condition for test specimens; surface treatment as inorganic zinc-rich coating by setting loading velocity of 3 cases of 1 Hz, 0.05 Hz, 0.001 Hz as 1 cycle. As a result of the experiment, there was some degree of velocity dependence on slip load and slip coefficient, and when loading velocity was large, both slip load and slip and friction coefficient tended to increase. And, it was shown that the rate of decrease became small and the slip load converged in any case, when the loading over 10 cycles was continuously applied.