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Before the anticipated Nankai Trough earthquake, the effects of multiple cascading hazards on bridge performance and the associated functionalities of road networks must be assessed to develop recovery strategies. This paper presents a framework for assessing the probabilistic connectivity of road networks exposed to both ground motion and tsunami, considering the spatial correlations among hazard intensities. To evaluate the joint probabilities of bridge states (i.e., passable and impassable states) and the probabilistic connectivity of road networks, the total probability theorem was used to integrate spatially correlated seismic and tsunami hazard assessments into the fragility estimates that consider the cascading effects of ground motion and tsunami-induced damages to bridges. For illustrative purposes, the probabilistic connectivity of hypothetical road networks in Japan that could be affected by both ground motion and tsunami during the anticipated Nankai Trough earthquake was assessed using the proposed method. The results showed that seismic retrofitting of bridges located along the route where the probability of impassable states due to tsunami is very low can enhance the probabilistic connectivity of entire road networks. [ABSTRACT FROM AUTHOR]

Coordinating a wide range of organizations is crucial for disaster management. This paper reviews the coordinating mechanisms of disaster management in Japan, in particular focusing on the relationship between national and local governments. While local governments have the principal responsibility of managing disasters, they often have limited capacity and experience in disaster management. Furthermore, they are often overstretched with the various tasks of response and recovery. Supporting local governments from the outside and coordinating such support activities are essential in mitigating disaster damage. This paper examines (1) coordination mechanisms, and (2) actual coordinating efforts of response and recovery in recent disasters such as the Great East Japan Earthquake and Tsunami in 2011. It was found that Japan is evolving in coordinating mechanisms by learning from disasters. The national platform of coordination was established over 50 years ago. Similar platforms were established at the local level as well. Each national agency has established and strengthened the supporting teams of response and recovery efforts in affected areas. Local governments outside the affected areas also provide support to affected governments according to pre-agreement. [ABSTRACT FROM AUTHOR]

This paper describes the state of the art of structural steel reuse in Japan. A significant part of the material is taken from a document titled the Architectural Institute of Japan (AIJ) Recommendations for Sustainable Steel Building Construction (Draft) available only in the Japanese language. The motivations for and potential benefits of steel reuse are examined. The affinity between seismic design requirements and steel reuse is highlighted through a concept known as "damage-control" design. Some technologies for disassembly are introduced. The historical development and changes in Japanese structural steel are summarized, followed by a discussion on reusability of historical steel reclaimed from existing buildings. Reuse projects whose details are known to the authors are listed. The heart of the paper is a design procedure that specifies the structural engineer's role and involvement in planning, material procurement, and executing a steel reuse project. The discussion is concluded by six directions that should be pursued to make steel reuse a widely accepted reality in Japan. Among those directions are research needs to establish a procedure to quantify the remaining structural performance of reclaimed steel considering possible exposure to earthquakes, establish connections that allow for easy disassembly, and introduce modularized structural systems. High seismicity and the general practice to adopt full moment frames pose unique challenges for steel reuse in Japan. [ABSTRACT FROM AUTHOR]

The rapid growth of urban populations and the environmental concerns associated with this growth challenge city planners and developers to consider more sustainable building systems. In Japan, the recent change in the law governing building standards and introduction of cross-laminated timber (CLT) offer the prospect of a further extension of the height of timber buildings to the high-rise category. Because of that, many researchers have begun to research the possibility of hybridizing CLT with steel-framed structures to increase the performance of buildings utilizing CLT. This paper presents the test and numerical results of cyclic loading experiments performed upon CLT shear wall infilled hybrid steel frames with concealed metal plates and drift pin (DP) connections. For the failure modes of the tests, shear failure of CLT at around 1/50–1/30 rad were observed in almost all specimens, except the specimen with slender steel beams, which led the CLT to out-of-plane deformation. The load sharing effect between two components were also evaluated, showing that the steel and CLT infill worked closely together to resist the lateral load. After the experiments, a numerical model was developed using the nonlinear finite analysis software SNAP V7.0 to predict the results of the experiments. The model was developed based on the results of element tests conducted previously, was validated using the test results, and can potentially serve as the basis for an appropriate form of methodology with which to design future CLT-steel hybrid structures for service in seismically active regions. [ABSTRACT FROM AUTHOR]

The deployment of wireless sensor network (WSN) for continuous seismic monitoring system of cable-stayed bridge is presented in this paper. A newly developed WSN that is based on simultaneous high-speed concurrent transmission flooding technique was implemented on the Shin-Nakagawa Bridge, a 530-m single-plane, single-pylon, steel box girder, cable-stayed bridge in Ibaraki prefecture, eastern Japan. The structure is seismically isolated with laminated rubber bearings at the main pylon and piers. Some isolation bearings were partially damaged by the 2011 Great East Japan (Tohoku) earthquake. As a part of monitoring, a WSN with a total of 26 sensor nodes were installed at several locations on the piers, main pylon, girder, and ground. This paper describes the WSN system, the monitoring scheme and procedure, analysis of recorded seismic responses, and their use for structural assessment, especially the performance of isolation bearings during earthquakes. The monitoring system successfully recorded structural responses from 63 earthquakes in the 45 months monitoring period between August 2017 to December 2020, which include the responses from near-field and far-field earthquakes. The comparisons of recorded ground motions with existing nearby seismograph have shown the accuracy and reliability of the WSN. Modal parameters of the bridge were successfully determined from the seismic responses obtained from the WSN using multi-input multi-output time-domain system identifications. Characteristics of seismically isolated bridge responses, such as high-frequency filtering effect and decoupling effect of the girder responses, can be clearly observed from the records of the large earthquakes. [ABSTRACT FROM AUTHOR]

The uncertainty in walking and waiting transfer times at transit stops depends on the environmental conditions, vehicle schedule punctuality, and variations among individuals. Relying only on the mean values ignores such uncertainty and leads to improper transfer coordination. This paper provides a general framework to estimate the time distribution parameters of walking and waiting based on automatic-fare-collection data under the assumption that the distribution function is known. The proposed methodology contributes to the existing literature by providing a stochastic frontier model (SFM) that is adaptable to transit assignment models. The normal/exponential SFM is utilized to estimate distribution parameters based on the maximum-likelihood method. The methodology was applied to smart-card data from Japan to estimate the transfer walking- and waiting-time distributions between bus stops and rail stations. The results indicate a low disturbance in the observed data for walking time and that our assumptions regarding walking-time estimation were reliable. Furthermore, we quantified how the waiting time at a bus stop depends on variations in the service headway. These findings are expected to help in making more informed decisions to optimize transit schedules. [ABSTRACT FROM AUTHOR]

This paper presents a time-varying model-based method for estimating earthquake-induced displacement responses of building structures using limited acceleration data. First, a time-varying model which considers the variability of stiffness by a time-variant story local stiffness reduction factor and the variability of damping by formulating the Rayleigh damping model with a time-variant mass coefficient was developed. Then, a displacement estimation algorithm was derived on the basis of the state space representation of the time-varying model and the unscented Kalman filter. The effectiveness of the proposed method is numerically verified through nonlinear responses of a ten-story building model where the hysteretic restoring force is simulated by the Bouc–Wen model. In addition, numerical results indicated that a few sensors with low noise are more desirable for the measurement strategy. Finally, the applicability to realistic seismic monitoring of buildings was investigated through a 1∶3-scale 18-story steel frame test at the E-Defense shaking table facility, which tested collapse behavior and realistic damage of high-rise steel buildings constructed in the 1990s in Japan. [ABSTRACT FROM AUTHOR]

Compound flood disaster risks are increasing due to multiple river floods within a single storm event. Many studies targeted dependence structure based on multivariate extreme value theory; however, fewer studies focused on the sum of subset joint probabilities (SSJP), defined as the probability that any combination of rivers are flooded over the target area as an integral index of compound flooding risks. Modeling multivariate extremes at high dimensions faces two challenges: model complexity and sample size. In this study, as a classical asymptotic dependence model, the Hüsler–Reiss (HR) model was explored to resolve the former issue owing to its simplicity. From the multivariate HR model, any subset joint probability is explicitly obtained without numerical integration of angular measure, and dependence parameters are constructed from only pairwise parameters. The latter challenge was addressed using a large ensemble (50 members of 60-year simulation) of the database for policy decision-making for future climate change (d4PDF), which is consequently regarded as the annual maximum flow data of 3,000 years. This study analytically derived SSJP based on the HR model and tested its applicability using annual maximum flow data simulated from d4PDF for 20 rivers in Kyushu Island, Japan. The simulated SSJP based on the HR model and empirical SSJP were compared as the probability plot of the number of river basins where peak discharge exceeds the design level. As a result, under the constraint of HR that the partial correlation must range from −1 to 1, the estimated SSJP by the HR model was in agreement with the empirical SSJP. The case study presents promising results of the proposed HR model–based approach. [ABSTRACT FROM AUTHOR]

It is crucial for the Japanese government to establish a new energy mix plan since the previous plan was subject to review after the Fukushima nuclear accident in March 2011. The Japanese government proposed a new energy mix option in June 2015. However, the high degree of uncertainty will impair the robustness of energy mix options decided based on predictions. This paper uses robust decision making (RDM) to take uncertainty into account and determine robust energy mix options. An hourly electricity dispatch and power plant renewal simulation covering 2016–2035 in Japan is conducted to analyze the economic and environmental impacts of several energy mix options. The results show that the options with greater use of coal-fired and wind power plants have robustness against future uncertainties and that the current government plan is inefficient. [ABSTRACT FROM AUTHOR]

This paper presents a geographic information-based mixed integer linear programming model for a district heating system design. The model minimizes the annualized investment and operation costs of the system, with the key results showing the optimal distribution network structure and optimal capacity and dispatch of heat plants. A network topology of nodes and edges, providing accurate geographic representation of the district, is generated using a geographic information system and acts as a constraint. A case study is conducted for a district in Hirosaki city, located in the northernmost prefecture of mainland Japan. The results demonstrate the considerable economic benefits of integrating locally available woodchips in heat-only boilers instead of using city gas due to lower fuel costs. Low temperature operation reduces the fuel costs due to less network heat loss compared to medium temperature operation, but it is overcome by the cost of the larger pipe size and the pumping power. Implementation of the district heating system to the case area encourages sustainable development through economic favorability, decreased primary energy consumption, and considerable CO2 emissions reduction, compared to the current heat supply structure. [ABSTRACT FROM AUTHOR]

Distributed energy systems such as solar power photovoltaics (PV) and cogeneration systems (CGS) are expected to play a main role in future energy systems. However, consumers employ these distributed energy systems based on individual decisions rather than topdown installation planning, so even if the expansion of PVand other renewable energy sources is a national energy policy, it remains uncertain how and when PV installation targets will be realized. Furthermore, when consumers extensively deploy distributed energy systems, the power-expansion planning of utilities will be affected by changes in daily load patterns. In this paper, the authors develop a two-stage model focusing on interactions between the energy system adoption behavior of customers and power-expansion planning of a utility. In the first stage, the authors disaggregate Japan’s Kanto region into 38 areas and then develop an optimum energy system model including PVand CGS for consumers. In the second stage, the demand for electric power from the utility is transferred to the power-expansion planning model of the Tokyo Electric Power Company. The authors observe how well the results for PV penetration agree with the cost and the market projection scenarios given by governmental plans. The effects of subsidy scenarios for PVare also evaluated. The authors find that PV penetration will not meet installation targets unless additional PV promotion policies are implemented. The power-expansion model in Stage 2 shows how consumer behavior affects long-term expansion. These findings suggest the need for an integrated energy policy promoting a low-carbon society [ABSTRACT FROM AUTHOR]

Frequent catastrophic earthquakes have highlighted the significance of postearthquake recovery and reconstruction (PERR) planning, a dynamic and inclusive process which encourages the building of more resilient communities. This paper aims to provide some meaningful lessons for quake-prone countries through a review, comparison, and discussion of PERR planning success and failure factors in the 1994 Northridge earthquake in the United States, the 1995 Kobe earthquake in Japan, the 2003 Bam earthquake in Iran, and the 2008 Wenchuan earthquake in China. The authors then provide some guidance for PERR planning in key areas such as formulating predisaster planning, enabling participatory planning, capacity building for public involvement, schedule control, process coordination, developing catastrophe insurance, protecting vulnerable groups, and assessing plan quality. Further in-depth studies could be done to conduct broader crossnational comparisons on some important specific aspects, such as predisaster planning, participatory planning, and plan implementation. [ABSTRACT FROM AUTHOR]

The stability of slopes subjected to vertical embedded strip footing loads under static and seismic conditions was investigated. The pseudostatic method was considered to represent an earthquake load. Two-dimensional lower-bound finite-element limit analysis (LB-FELA) and the strength reduction method (SRM) were employed to investigate the stability and failure mechanisms of the slopes subjected to the footing loads. It was found that the factor of safety (FOS) started to decrease rapidly after a certain load (defined as a threshold load). The critical location of the footing on the slope (where the FOS was at a minimum) was examined. In addition, a series of numerical analyses were carried out to check the effect of edge distance on slope stability. Changes in the FOS were evaluated for a particular footing edge distance for varying slope angles. The effects of variation in the shear strength parameters and the location of the water table on the slope stability under footing loads were also examined. It was found that the effect of loading intensity on the FOS was significant for gentle slopes, with this effect decreasing for steeper slopes. The influence of footing width on the FOS, for a given slope angle and loading intensity, was also insignificant. The footing near the slip surface at the top of the slope was the most critical location. The effect of the water table on the FOS diminished as the loading intensity on the footing increased. To demonstrate the practical application of this study, we also examined the slope failure that occurred during the 2011 Tohoku, Japan, earthquake. [ABSTRACT FROM AUTHOR]

Yokohama Bay Bridge, with a total span length of 860 m, is the second longest span cable-stayed bridge in East Japan, and one of the most densely instrumented bridges in Japan. On March 11, 2011, the Great East Japan (Tohoku) Earthquake hit northeastern Japan with magnitude of 9.0, notably the largest earthquake in Japan's modern history. Intensity of the maximum scale 7 of Japan Meteorogical Agency's seismic intensity was recorded on the bridge site. This paper describes seismic response analyses of the bridge, system identification, performance evaluation of link-bearing connections (a seismic isolation system), and postearthquake field observation. Response analyses show that transverse vibration dominated the response of girder and tower, with a maximum girder displacement of 62 cm. The large transverse vibrations induced pounding between tower and girder on the tower-girder connections as shown by the periodic impulses on acceleration records. Meanwhile, longitudinal accelerations indicate that the link-bearing connections functioned properly during the earthquake. System identification reveals nonlinearity of the response as evidenced by variations in natural frequencies and mode shapes during large excitation. Despite these conditions, the bridge did not suffer any structural damages, since the ground motions experienced during the earthquake were less than the design and seismic retrofit ground motions. [ABSTRACT FROM AUTHOR]

Understanding the seismic resistance mechanisms and safety limits of cross-laminated timber (CLT) buildings and performing an accurate evaluation of their seismic performance is critical in earthquake-prone areas such as Japan, the US, and Italy to ensure that human lives are protected against major earthquakes. However, the knowledge from shaking table tests of full-scale CLT buildings is limited, and most tests' maximum interstory drift is less than 4%. As a first step toward collapse analysis, this study replicated a full-scale two-story shake table experiment with a maximum interstory drift of 8.77%. The analysis software was developed by the authors and modified to consider the restoring force and the P–δ effect to replicate seismic behavior at large deformation. The skeleton curve parameters were employed in the analysis model and then changed. The results that matched the experimental results well were searched comprehensively by performing data assimilation. As a result, both the overall behavior (story shear force–interstory drift relationship) and the detailed behavior (uplift displacement of CLT wall foot of the first story) were consistent with the experimental results, indicating that the proposed analytical method can replicate the seismic behavior of CLT buildings even at large deformation. [ABSTRACT FROM AUTHOR]

Urban health efficiency is influenced by both urban planning decisions and the functioning of the public health system. However, there is currently a lack of effective methods to simultaneously examine urban planning and public health when assessing urban health efficiency. This study proposes a two-stage network data envelopment analysis (DEA) model for evaluating urban health efficiency. The urban planning and public health sectors act as interconnected stages where the public facilities and living quality are mediating variables. The urban health efficiencies of 303 Japanese cities are examined using the proposed model, showing that most Japanese cities still have room for urban planning improvement with pure technical efficiency ranging between 0.7 and 0.9. At the same time, most public health sectors of Japanese cities reach pure technical efficiencies larger than 0.95 but are limited by the scale efficiency. Further analysis points out that public health sectors are in decreasing-return-to-scale, meaning that excessive urban scale adversely affects urban health efficiency. Furthermore, cities that joined the Alliance for Healthy Cities (AFHC) performed better on average, suggesting that information sharing and national and international networking can boost urban health. The study shows that the proposed two-stage network DEA model can be applied to analyze urban health efficiency and identify the impact of technology and urban scale in different stages. [ABSTRACT FROM AUTHOR]

To present a hybrid theory of disaster prevention actions and develop a common framework, this study theoretically and systematically reviewed recent research in Japan on actions from three perspectives: definition, multidisciplinarity, and multidimensionality. First, this research validated that the definition of actions on disaster prevention and reduction should be understood in three contexts: responsibility, willingness, and habituation; the diversity of terminology; and the type of measure. Second, the multidisciplinary nature of the approach affirmed that the motivations and approaches could be organized according to the axes of individual and social models and epistemic and design sciences. Third, per the multidimensional nature of theories explaining actions, the applied theories were organized based on the four perspectives: process, motivation, internal experience, and context. Furthermore, it was suggested that there are three critical perspectives: complicity in neoliberalism, invisibility of social inequalities, and bias in reporting desirable results (expert-serving bias). Taking an approach that emphasizes interdisciplinarity and multidimensionality, this study details the background of Japanese research used to employ a theoretical approach to understand individual cognition and demonstrates the need for research to understand the political, cultural, social, and economic environments that support disaster prevention behavior, noting that this is tied to the unique Japanese context of individual will and dependence on the government. This study is significant in that it provides a map for positioning one's research and pointing the way toward future collaboration in the direction showing definition, interdisciplinarity, and multidimensionality are important components in understanding disaster prevention behavior. This study reviewed three aspects of recent disaster research in Japan to better understand disaster prevention behavior: what it is and what areas and aspects of it are being studied. First, Japanese disaster prevention behavior can be understood in relation to "responsibility," "will," and "habit"; the diversity of behaviors; and the types of measures applied. Second, motivations and approaches could be amenable to organization along the axes of whether the coping subject is an individual or society and whether the science focuses on "what it is" or "what it can do." Third, explanations of disaster prevention behaviors were found to be viewable in relation to four perspectives: process, motivation, experience, and context. Three criticisms were also found: social inequalities are less visible, many results that are preferable to the researcher are reported, and there is a risk of becoming connected to particular political policies. This study found that although many theories that explain individuals' perceptions are used to explain their disaster prevention behavior, it is also important to understand the environment of the political, cultural, social, and economic aspects that surround the individual. [ABSTRACT FROM AUTHOR]

There is increasing interest in using cross-laminated timber (CLT) in buildings because of its high strength and stiffness. In Japan, structural design guidelines for CLT buildings were established in 2016 and construction of mid-rise buildings is increasing. Wide-panel walls can exceed widths of 10 m and integrate cut-outs for window and door openings. However, under lateral loads, corner cracks at the openings have been the most prevalent failure mechanism. To investigate the initiation and propagation of corner cracks, a series of bendings are undertaken on L- and T-shape specimens extracted from the CLT panels. In addition, three-point bending and shear tests are also carried out on beam sections extracted from the CLT panels. Three types of brittle failure were observed: bending failure of the beam or column, and rolling shear failure. [ABSTRACT FROM AUTHOR]

Rural areas support urban areas by preserving natural environments such as forests and agricultural food products. However, because of urbanization after the high-growth period, the ecological balance has deteriorated because of land development, abandonment of cultivation, automobile dependency, and similar factors. This study assessed an improved method of calculating the ecological footprint (EF) value, which assigns a rating for environmental balance in rural areas. Residents’ consumption is calculated based on the environmental load (cultivation, CO2 emission, and similar loads) that residents generate during daily life activities. A case study of Tsukuba city in Ibaraki Prefecture reveals a wide distribution of traditional settlements for which this system can determine the environmental balance. Analysis of the case study shows: (1) environmental productivity and consumption capacity differed greatly according to the advancement of urban development, and (2) only a few settlements, located in forested areas, are ecologically balanced. [ABSTRACT FROM AUTHOR]

The heavy rainfall that occurred in western Japan in July 2018 caused massive and widespread damage to social infrastructures and lifelines. Certain cases that can be used to specifically and quantitatively analyze the damage situation and the cause of the damaged bridge groups are valuable for overcoming structural and complex engineering problems. Such cases can be used to identify the causes of the failure and the analysis progress, and they will help improve the design elements and construction method of bridges in the future. They could also yield such measures as washing out of the bridge at the time of flood. In this study, we conducted a field survey of the washed out Misasa railway bridge, and we evaluated the conditions that caused the failure based on hydrological, hydraulic, and structural analyses at the time of the flood, based on a field survey of the affected bridge. These analyses will help obtain design elements for small and medium bridge structures and countermeasures in the future. We focus on the collapse issue of the 1st Misasa Railway Bridge, wherein the collapse trigger of structural stability can be evaluated through its collapse mechanism. The structural analysis reveals the flood hydrodynamic force on the bridge girder during the flood that caused the collapse. In particular, when the hydrodynamic force of the water flow acts on the bridge girder part, the flood hydrodynamic force that led to the collapse of the bridge is estimated from the engineering point of view of structural stability. Based on the failure processes and conditions revealed by the analyses, we identified design elements that can help increase the resistivity of bridge structures on small rivers against floods with effective methods. [ABSTRACT FROM AUTHOR]

Six full-scale specimens were tested to examine the cyclic-loading performance of steel moment connections between an I-section beam and I-section column. The specimens represented the current practice in Japan in materials, dimensions, detailing, and fabrication. Three of the specimens had the beam welded to the web of the column; the other three had the beam welded to the flange of the column. Some of the specimens had doubler plates welded to the column web. Regardless of the framing orientation, the specimens displayed similar strength and stiffness. All specimens met the performance requirement for special moment frames according to US seismic provisions except for one specimen, which had the beam welded to the column web, and which failed prematurely by fracture of the continuity plate. Yielding of the continuity plate was found to be an important factor that can lead to such failure. Therefore, by making the continuity plates stronger than the beam flanges, either by adopting a sufficiently strong steel or thicker plate, moment connections to the column web, fabricated according to the current Japanese practice, may behave very similarly to moment connections to the column flange. [ABSTRACT FROM AUTHOR]

Clinker ash is a byproduct obtained from coal-fired electrical generators. It is a type of recycled granular material with a complex particle shape and large surface roughness. Particle shape descriptors and surface fractal dimensions are effective parameters to quantify sand grain morphologies. A simple image analysis approach is employed to determine the aspect ratio, sphericity, roundness, and convexity of 12 types of clinker ash collected from thermal power plants distributed on the western island of Japan. Compared to the majority of sands with other mineralogical components, clinker ash particles have a smaller aspect ratio, sphericity, and roundness. Under similar test conditions, clinker ash exhibits higher shear resistance than natural sands at the critical state. Critical state friction angles tend to decrease with increasing aspect ratio, sphericity, roundness, and convexity. A decreased aspect ratio, roundness, and convexity enhance the slope and intercept of critical state lines in the void ratio and mean stress plane. The mean regularity, which is the average of four particle shape descriptors, is regarded as an effective index to characterize the shear strength of clinker ash at the critical state. The surface fractal dimension could also be decided from digital image analysis. The results also show that the critical state friction angle is well correlated with the surface fractal dimension for different types of clinker ash. The implication is that a rougher surface texture hinders the rotation, frustration, and interlocking of particles at the critical state, resulting in higher shear resistance. [ABSTRACT FROM AUTHOR]

The aging of bridges coupled with increased vehicular traffic requires timely and accurate inspections for elevated highway structures. Recent studies have leveraged the advent of drones and computer vision to automatically conduct quick, safe, and effective inspections for elevated highway structures. However, such studies rarely offer insight or recommendations for an end-to-end integrated system that streamlines data collection, analytics, and reporting. Toward this goal, we present an end-to-end robotic bridge inspection system consisting of five tightly coupled methods to: (1) create automatic data collection missions; (2) assure visual quality of such missions; (3) reconstruct three-dimensional (3D) models of elevated structures; (4) detect and localize surface distresses in 3D; and (5) generate reports complying with highway agencies' requirements. We validate each developed method and the whole system on two representative inspection projects. Results show that our system can objectively satisfy requirements for data collection and provide up to 85.3% average precision over five defect types. We finally share lessons learned while deploying our system to 30 bridge inspection projects in the US and Japan, particularly for documenting, communicating, and following-up with bridge inspectors' recommendations. [ABSTRACT FROM AUTHOR]

The Daikai Station subway structure in Japan completely collapsed during the Hyogoken-Nanbu earthquake that occurred on January 17, 1995. Based on the numerical results obtained by two-dimensional finite-element analysis, the structure is believed to have collapsed as a result of strong lateral vibration. However, because it deformed in an approximately symmetrical manner with respect to the shortened central columns, it might have experienced catastrophic collapse due to vertical impulse motion. To investigate the dynamic response behavior of the structure due to sudden upward loading, a three-dimensional elastoplastic transient response analysis was conducted considering an isolated upward pulselike displacement wave from the bedrock. The results of this study suggest that the central column of the structure reached axial compression failure due to the amplitude of the displacement wave increasing significantly at the lower end of the column. This method can numerically reproduce the collapsed state of the structure and the considerable settlement of the ground surface due to the occurrence of the high-intensity earthquake. [ABSTRACT FROM AUTHOR]

Tsunami waves are often very energetic and therefore pose a significant threat to coastal structures. However, most coastal defenses such as detached breakwaters are designed to protect against storm waves, with the consequence that tsunamis often lead to a catastrophic failure of these structures. This numerical study was inspired by the wave scenario, which occurred at Soma Port in Japan, during the 2011 Tohoku tsunami where a combination of tsunami-type waves and shorter period undular bores caused severe damage to a detached caisson breakwater. The objective herein is to analyze the role that undular bores play on breakwater stability in the case of a tsunami propagating over a gentle slope into shallow water. Two complementary wave models, one of Boussinesq type and the other of Reynolds-averaged Navier-Stokes (RANS) volume of fluid (VOF) type, are used to compute the propagation of a representative tsunami composed of multiple waves components and their impact on a detached breakwater. The presence of an undular bore is controlled by the balance between wave nonlinearity and dispersion. As the draw-down from the first wave reduces the water depth around the breakwater and leaves the structure almost completely exposed, only the second wave transforms into an undular bore. This causes wave breaking far offshore from the breakwater where a large amount of energy is dissipated ultimately resulting in much less-destructive wave impact at the structure. The undular bore influences the wave loading on the breakwater, though the bulk of the wave loads and the excessive bearing pressures were computed for the long-lasting overtopping process of the first wave. These findings facilitate the damage assessment of detached breakwaters as they relate some specific tsunami features to structural stability and failure mechanisms. The results also provide information regarding the applicability and usefulness of different numerical modeling approach for the analysis of the stability of detached breakwaters under tsunamis. For this particular case, even depth-integrated numerical models provide conclusive solutions. To the best of the authors' knowledge, this is the first numerical study addressing breakwater stability with respect to the impact of undular bores under tsunami conditions. [ABSTRACT FROM AUTHOR]

The buildup of sediment deposits in reservoirs is a long-standing problem with serious consequences on the reservoirs' functionality and the ecology of their river systems. In the last two decades, hydraulic dredging has been used as a more viable engineering solution to restore reservoirs' sustainability. This study proposes a novel ejector-pump dredging system (EPDS) that solely utilizes hydraulic dredging for removal and transport of the sediments deposited at the reservoir's bed. Unlike conventional dredging methods, air is injected into the header pipeline to create a turbulent three-phase flow regime that enhances the solids suspension and continuous flow in the system. Introducing air effectively reduces the critical value of the deposition velocity of the dredged solids and transports them in a slug flow regime. This technique minimizes the tendency of the sediment to settle, and therefore eliminates system plugging. A laboratory prototype of the proposed system has proven the efficacy of removal and transport of mixed-size sediments up to 150 mm. Field trials have further shown the feasibility of the proposed system. Removal of large sediments with productivity approaching 70 m3/h was made possible using the suction-type EPDS. The hopper-type EPDS enabled carrying the dredged material for up to 1,000 m without resorting to a booster pump. The developed system was successfully used as part of an integrated dredging management program carried out for the Oouchibaru, Saigo, and Yamasubaru dams in the Mimi River basin, Japan. The very low turbidity levels recorded during the sediment dredging and transport operations of EPDS are indicative of the eco-friendly performance of the system. [ABSTRACT FROM AUTHOR]

To promote the development of cross-laminated timber (CLT) structures, the Japanese Government Notifications on Structural Design of CLT Buildings (GN 611) was issued in 2016. In GN 611, three types of platform-framing CLT structures were classified in the simple calculation method of Route-1. Compared with a platform-framing structure, which has been clarified in GN 611, a balloon-framing structure is superior in shortening the construction period and reducing the number of CLT panels and metal connectors. To study the seismic properties of balloon-framing CLT structures and develop new structures for a CLT building, four full-scale, 3-story CLT structures were tested under quasi-static cyclic loading: Specimen 1 was a platform-framing structure with narrow wall panels; Specimen 2 was a balloon-framing structure with continuous wall panels; Specimen 3 a was platform-framing structure with wide wall panels; and Specimen 4 was a balloon-framing structure with continuous wall panels and glulam beams. In this study, experiments were conducted, and the seismic performance of the balloon- and platform-framing CLT structures were evaluated and compared. The test results indicated that the seismic properties of Specimens 1, 2, and 3 were similar and that the design method of Specimen 1, as specified in GN 611, was applicable for Specimens 2 and 3. Specimen 4 exhibited higher lateral load resistance than the other three specimens. The performance of Specimen 4 depended on the moment-resisting performance of the glulam beam and CLT wall joint. In this case, the moment-resisting performance obtained through the experiment was significantly higher than the predicted performance. [ABSTRACT FROM AUTHOR]

Measured force-displacement sensing data are analyzed to create nonlinear hysteretic models for elastic sliding bearings and steel dampers. These data were collected during full-scale experimental tests of a base-isolated structure at Japan's National Research Institute for Earth Science and Disaster Resilience (NIED) "E-Defense" Hyogo Earthquake Engineering Research Center in 2013 that employed historical and synthetic earthquake inputs. Several models are explored for each isolation-layer device, including Coulomb friction models for the elastic sliding bearings and Bouc-Wen hysteresis models for both devices. Parameters for each device model are estimated via constrained nonlinear optimization to minimize model prediction error using testing data. The resulting models are applied to data from other seismic tests to evaluate the models' ability to provide accurate force predictions. The model for the steel dampers demonstrates the capacity to be generalized across seismic excitations and devices, whereas the model for the elastic sliding bearing reproduces well its behavior during other seismic excitations but is limited to the device to which it was calibrated. The residual error between the model predictions and measurements does not contribute a significant degree of variance in the model parameter estimates. [ABSTRACT FROM AUTHOR]

Corrosion of steel reinforcement caused by airborne salt penetration into concrete cover is a very important reason for the deterioration of concrete structures exposed to an atmospheric marine environment. The current durability of coastal concrete bridges is an academic and engineering concern worldwide. In this study, three outdoor exposure experiments in the atmospheric marine environments, considering multiple environmental factors, were carried out spanning 4 years to investigate chloride adhesion and diffusion behaviors at the Amatori Bridge of Wakayama Prefecture in Japan. It was found that the distribution of accumulated chlorides on the concrete and steel surfaces is not only time dependent but also space dependent, which is related to the local weather conditions and geography. Note that the annual average wind speed around the bridge site is relatively low (approximately 3 m/s), which is a speed range rarely reported in the existing literature. The relationship between chlorides from airborne salt and chlorides that penetrate into concrete specimens is discussed quantitatively based on a specific tubular collection device (TCD) and the electrometric titration method. It was also observed that chloride deposition increases obviously during typhoons than during periods with no unfavoable weather event. In addition, two groups of mortar specimens were placed under and beside the bridge to explore the influence of seasonal rainfall distribution on the chloride diffusion behaviors in mortar specimens. The research results are expected to determine the priority for the maintenance and management of coastal bridges in Japan. [ABSTRACT FROM AUTHOR]

Corrosion of steel reinforcement due to chloride penetration is a major deterioration mechanism of reinforced concrete (RC) structures exposed to marine environments. In the present paper, a probabilistic model is presented to predict the chloride penetration profile in concrete and the risk of steel corrosion considering the time dependence of both the diffusion coefficient and the surface chloride concentration of concrete. Abundant field data from two projects in China and Japan are respectively collected. The consistency between these field data and the model prediction verified the reliability of this probabilistic model, based on which further parametric analyses were carried out to investigate the effects of different design variables on the probability of steel corrosion. [ABSTRACT FROM AUTHOR]

In March 2011, the Tohoku tsunami swept over the east coast of Japan killing more than 15,000 people and missing more than 2,500 people. The tsunami resulted in collapsing of more than 400,000 buildings and washing away of more than 250 coastal bridges. In this study, the collapse of Tsuyagawa bridge damaged by the Tohoku tsunami is numerically investigated using the applied element method (AEM) because of its advantages for simulating structural progressive collapse. The AEM is a discrete crack approach that allows the elements separation, fall, and collision with each other in a fully nonlinear dynamic scheme of computations. The analysis was demonstrated to efficiently simulate the bridge collapse, showing that the bridge collapsed at a water speed of 6.6 m=s initiated by flexural failure of its piers. The study of bridge strengthening showed that the collapse water speed could be increased by 22 and 29% compared to Tohoku tsunami if piers are strengthened by a 100-mm RC jacket and 20-mm thick steel jacket, respectively. [ABSTRACT FROM AUTHOR]

Nankai megathrust earthquakes are expected to occur with a return period of approximately 90-200 years along the fault of the Nankai Trough. Because they are interplate earthquakes, it is predicted that they will cause heavy liquefaction damage as a result of the long duration of their ground motion, especially around bay areas with soft deposits. In this study, a numerical analysis was performed for the ground in Osaka City with a hypothetical earthquake in the Nankai Trough region. In the numerical simulation of the dynamic behavior, a liquefaction analysis program was used. To quantify the degree of liquefaction at certain points, an index, named the liquefaction risk index (LRI), was defined and obtained by the weighted integration of the effective stress-decreasing ratio (ESDR) with respect to depth. Moreover, the LRI values were evaluated by data from the 1995 Hyogoken-Nanbu earthquake. It was found that the obtained LRI values were greater than 6.0 for the points at which heavy liquefaction damage had occurred. From the numerical results, the risk of liquefaction was evaluated with these LRI values. [ABSTRACT FROM AUTHOR]

Data for approximately 20,000 small marine vessels damaged by the 2011 Great East Japan tsunami, including information on motor types and tonnage, were collected and used to develop loss functions. The observed maximum tsunami heights from the field survey were used, and the maximum tsunami flow velocities from numerical simulation were obtained. Damage ratios were calculated, and loss functions were fit using linear regression analysis and log-normal distributions. The damage probability was significantly increased when the tsunami height was more than 2 m or when the flow velocity was more than . The results show that small vessels (weighing less than 5 t) with outboard motors were the most vulnerable. In addition, vessels at locations farther from the tsunami source had less damage because they were hit by smaller tsunamis with slower arrival times, which most likely gave them a chance to evacuate to deep sea. The results of this study, including the loss functions, will be useful for macroscale tsunami hazard and loss predictions involving small marine vessels. [ABSTRACT FROM AUTHOR]

Thin-walled partially concrete-filled steel tubular (PCFT) columns have come to be used as the piers of elevated-girder bridges widely in Japan because of their excellent seismic performance: strength, ductility, and energy dissipation capacity. To consider this excellent seismic performance in design, it is essential to provide an analysis method to assess the ultimate behavior of the thin-walled PCFT columns by considering the cyclic local buckling of the steel tube, the behavior of the confined infilled concrete with cracks, and the interface action between the steel tube and infilled concrete. Up to the present, the shell–solid element model analysis has been the only numerical method that can be used to consider these complicated behaviors of PCFT columns in a direct manner. However, the use of this model requires unrealistically long computation time and often encounters numerical difficulty to obtain convergent solutions when applied to large structural systems such as the elevated-girder bridge systems with the multiple thin-walled PCFT piers. The objective of the present research is to propose a practical three-dimensional fiber-based model with a failure segment that is computationally efficient, yet accurate enough to assess the ultimate behavior of PCFT columns. This model was calibrated by an optimization technique, only referring to the in-plane hysteretic behavior of each single PCFT column calculated by the shell–solid element model analysis. The calibrated model is applicable to the seismic analysis of large structural systems with multiple PCFT piers under arbitrary multidirectional seismic accelerations. The accuracy and numerical efficiency of the proposed fiber-based model in the analysis of PCFT columns were confirmed extensively by the comparison to the shell–solid element model analysis results and the results of tests, such as cyclic loading tests and shake table tests. [ABSTRACT FROM AUTHOR]

Ecosystem services (ESs) including provisioning, regulating, and cultural services for sustaining and fulfilling human well-being are formed based on various conditions, processes, and components of natural and artificial ecosystems. Spatial conservation planning for sustainable ecosystem development requires precise information on the local potential for providing hydrological ecosystem services in a watershed. The principal challenges in spatially conserving multiple ESs are that they are not independent of each other, and that the interactive relationships between them are in the forms of trade-offs and synergies. The rationality of spatial priority conservation on reconciling multiple ESs will be enhanced if the interactive relationships are recognized at the planning stage. Such a framework is developed by integrating a hydrology model into a systematic conservation model, and it is illustrated with data about multiple hydrological ESs in the Teshio watershed, with the aim of developing a priority conservation ranking map that reconciles competing and compromising interactive relationships among multiple services. The water yield, sediment, and organic nutrient retentions concentrated in eastern and some northern areas with higher precipitation, more forest lands, and steeper slope, but the inorganic nutrient retention concentrated in riverine and southwestern places with agricultural lands. The spatial priority conservation ranking map of an individual ES is closely related to its spatially distributed pattern. The spatial priority conservation areas for sediment and organic nutrient retentions are traded off against those for inorganic nutrient retention. There are obvious differences between the spatial priority conservation ranking maps of individual ESs and those of multiple services together. The spatial priority conservation areas for multiple ESs together simultaneously include southwestern, riverine, eastern, and some northern places of the study watershed, which can balance the conflicts existing between sediment and organic nutrient retentions and inorganic nutrient retention. The systematic priority conservation areas of hydrological ESs provide an effective tool for identifying trade-offs between environmental protection and agricultural economic development. The proposed framework in this study can be applicable to similarly structural prioritization problems of other watersheds, which can sustain ecosystem conservation and economic development. [ABSTRACT FROM AUTHOR]

Because diverse functional losses of the overall built environment (e.g., buildings, industrial facilities, and civil infrastructure) from a disaster event cause tremendous inconveniences to refugees, it is essential to implement swift recovery plans. However, in a postdisaster recovery situation, when resources and time are severely limited, there exist difficulties in implementing appropriate plans. These difficulties are attributable to a lack of comprehensive understanding of the overall recovery processes, caused by associated interdependency among the functions of a facility/infrastructure and the dynamic features of multiple recovery efforts. Thus, this research develops a system dynamics (SD) model to understand overall recovery efforts in the whole region from a holistic perspective. Based on an actual disaster case (the 2011 earthquake of Tohoku), this research conducts a case study to analyze the effectiveness of governmental plans. The simulation results show that governmental plans primarily aimed at recovering the daily lives of populations may not always be helpful for rapid restoration operations. The findings also suggest that considering the associated interdependency among built environment functions in recovery planning is key to supporting not only the rapid functional recovery of the facilities but also the improvement of poor restoration work environments. In this situation, the timely uses of preplanned and government-centered recovery programs (e.g., temporary housing and temporary debris movement) can be more effective with a comprehensive understanding of dynamic features in interdependent and multiple recovery efforts. Further, it is expected that these analytical capabilities have the potential to support recovery planners both in developing effective special recovery programs and in providing improved institutional strategies. Policy implications and lessons learned from a past recovery case can also be helpful in providing specific guidelines for future disaster recovery planning. [ABSTRACT FROM AUTHOR]