Kobe Earthquake Research Articles

Analysis of Factors Affecting the Seismic Performance of Widened Flange Connections in Mid-Flange H-Beams and Box Columns

Following the Northridge and Kobe earthquakes, research has increasingly focused on achieving high ductility in beam-to-column connections. This study investigates the seismic performance of connections featuring widened beam-end flanges in mid-flange H-beams and box columns, an area with limited prior research compared to I-section columns and narrow-flange H-beams. Detailed finite element modeling using ABAQUS 6.1.4 demonstrates that widened beam-end flanges significantly improve bending capacity and ductility by relocating the plastic hinge away from the connection, thereby enhancing seismic resilience. Key findings include the identification of optimal design parameters: flange length ranging from 0.55 to 0.75 times the beam flange width, beam flange cutting length between 0.36 and 0.39 times the beam depth, and flange cutting depth from 0.19 to 0.23 times the beam flange width. These parameters ensure effective plastic hinge development and improved structural performance. This study introduces a novel approach that emphasizes geometric optimization over material-based enhancements, offering a cost-effective and practical solution for improving seismic performance and extending previous research insights.

Development and Evaluation of a Game to Foster Sustainable Self-Help and Mutual Help Education for Disaster Prevention

This study explores the development and evaluation of a game aimed at fostering sustainable self-help and mutual help education for disaster prevention. The game, developed using Unity and Blender, addresses the critical need for effective disaster preparedness, emphasizing the importance of community cooperation, as evidenced by the Great Hanshin-Awaji Earthquake, in which most rescues were performed by neighbors. Additionally, it features realistic disaster scenarios, and the game’s design incorporates gamification and simulation elements to enhance learning and engagement. An experiment involving 20 participants aged 20–21 years was conducted to evaluate the game’s effectiveness. Participants played the game on desktop personal computers for at least 10 min, and their performance and awareness were measured through pre- and post-gameplay questionnaires. The results indicated no statistically significant improvement in the ability to cooperate with strangers, provide correct instructions, or overall consciousness of helping others. However, a slight increase in the average scores was observed. Participant feedback highlighted the game’s realistic approach and suggested improvements in operability and platform compatibility. The study concludes that while the game shows promise, further development and research are needed to enhance its educational impact and effectiveness in disaster preparedness.

Hot springs reflect the flooding of slab-derived water as a trigger of earthquakes

In subduction zones, water expelled from the subducting slab is believed to be involved in seismic activity. However, little is known about its quantity and flow processes. Here, we show that the Arima hot springs in western Japan contain high concentrations of water derived from the subducting Philippine Sea slab. A long-term record spanning over half a century reveals that the fraction of slab-derived water exhibited a temporary surge in the year preceding and/or subsequent years of the 1995 Kobe (Hyogo-ken Nanbu) earthquake. In total, an estimated 2.6–4.2 × 105 cubic meters of slab-derived water was introduced in conjunction with the earthquake. We infer that the earthquake was triggered by a flood-like release of water from the slab or by the bursting of clogged flow paths to the hypocenter. Our findings highlight the importance of hydrologically slab-connected hot springs for understanding ultradeep water cycles and their causal relationships with seismic phenomena.

Development of Geotechnical Seismic Isolation System in the Form of Vertical Barriers: Effectiveness and Perspective

This paper discusses the concept of geotechnical seismic isolation (GSI) systems, characterized by new principles of action, to reduce seismic loads on buildings. The advantages and disadvantages of GSIs and their environmental and economic reliability are analyzed. The aim of the study is to develop a geotechnical seismic isolation system in the form of vertical barriers, using a rubber–soil mixture (RSM). The novelty of the work lies in the definition of effective structural and technical solutions of vertical seismic barriers made of RSM, characterized by reliability in providing seismic isolation. The ground and superstructure interactions are modeled in PLAXIS 2D software from 2021, using the finite element method, using the accelerogram of the Kobe and Northridge earthquakes. The results confirm the positive impact of using an RSM as an effective GSI geometrical. The results show that the GSI system using an RSM reduces horizontal accelerations by 60%. Significant acceleration reductions of 40–60% are also observed when the thickness and depth of GSI seismic barriers are increased. The results of the study contribute to the substantiation of methodology and scientific and technical efficiency of geotechnical seismic isolation as an economically favorable design alternative to the traditional seismic isolation system.

Earthquake Engineering Technology and Its Application

Recent earthquakes, such as the Osaka–Kobe earthquake (1995) and the Wenchuan earthquake (2008), have challenged earthquake engineering and its application [...]

The Effect of Nonlinear Sloshing Response of Water on Seismic Behavior of Reinforced Concrete Elevated Water Tanks

In this study, the fluid-structure interactive behavior by using the Westergaard approach and the Smoothed Particle Hydrodynamics (SPH) method of a 1000 m3 reinforced concrete (RC) elevated water tank under different seismic activities i.e., Kocaeli, Van, Kahramanmaraş and Kobe earthquakes was investigated. In the SPH method, the resulting hydrodynamic pressures were applied to the interior of the wall of the structure as an external force which is made as mass additions to the tank walls in Westergaard approach. With the help of software developed, the load carrying system of the elevated water tank was modeled using the MATLAB Partial Differential Equation Toolbox (PDE) software, based on the finite element method, and its verification was made by comparing with ANSYS software model. Dynamic condensation method was used to perform time history analyses for the cited earthquakes. The time-dependent solutions of partial differential equations are solved with the help of ODE45 functions based on Runge-Kutta method, by arranging the equation of motion in state-space format. The cited tank was analyzed linearly under different seismic activities for empty, half-filled (50%) and full-filled (100%) cases and the obtained results were compared with each other. It has been concluded that considering nonlinear behavior of the fluid during the earthquake with the SPH method provided consistency with the real behavior of RC elevated water tanks and gave more realistic results than the traditional Westergaard approach.

Detection of atmospheric radon concentration anomalies and their potential for earthquake prediction using Random Forest analysis

Various anomalies occurring before earthquakes are currently being studied to predict seismic events, with one of them being the radioactive element radon (222Rn). Radon concentrations in the soil, water, and atmosphere fluctuate in response to crustal movement. Recent research has statistically detected anomalies by analyzing the fluctuations in radon concentrations before earthquakes and conducting quantitative evaluations of radon. However, the method used to determine the parameters in the analysis was problematic. Therefore, in this study, we compared observed atmospheric radon concentration data with predicted values based on typical annual patterns using Random Forest analysis. We conducted a more objective analysis by employing this method and statistically determining anomalies using thresholds. This analysis was conducted using atmospheric radon concentration observation data obtained at Kobe Pharmaceutical University (KPU) before the 1995 Kobe Earthquake, and ionization currents emitted when radon decays were obtained at Fukushima Medical University (FMU) before the 2011 Tohoku-oki Earthquake. Consequently, before the major earthquakes occurred at both locations, the difference between the predicted and observed values exceeded the standard deviation by a factor of three. These results indicate the potential of Random Forest analysis to identify anomalies in atmospheric radon concentrations before earthquakes occur.

Comparison of Seismic Performance of Adobe Structures Strengthened with Two Different Schemes

ABSTRACT This paper presents the results of an investigation of dynamic behaviours of strengthened adobe structures. These structures were strengthened using two different schemes which were inexpensive and simple to apply. The dynamic testing was carried out on a shaking table which applied the loading corresponding to the 1995 Kobe earthquake record sequentially in increments of 25%. The structural damage to a model was divided into different damage grades using a quantitative measure of vulnerability. Although some differences were observed in the stiffness of the models in their undamaged state, the stiffness of both of them became similar in the damaged state. The changes in the fundamental frequency of the structure corresponded to the changes in the stiffness. The difference in the base shear demand of both models did not exceed more than 15%. The hysteresis loops of the tested structures turned non-symmetric at a peak ground acceleration of nearly 1.10 g. The models exhibited higher lateral load capacities in one direction of loading as compared to the other direction. The ductility and energy dissipation were also higher in one direction of loading. The performance of the tested structures was categorised into four performance levels and the data of drift, ductility, damping and period corresponding to each level have been reported.

Numerical Evaluation of Pile Group Behavior Subject to Earthquake Loads

The seismic design of pile foundations mainly relies on analyzing the seismic response of layered, liquefiable locations. Two design scenarios are taken into consideration from the case histories; the first is how pile foundations react to the stresses and lateral displacements brought on by the lateral dispersion of liquefied soil. The second is how to piles reaction to seismic activity that occurs with the development of high pore water pressures. The PLAXIS 3D software is utilized in this research with a non-linear soil constitutive model (hypoplastic model) for both dry and saturated loose sandy soils under the impact of two earthquakes and the motion of different features to give a complete understanding of the dynamic piled foundation response. The findings from this study show that the site profile, pile diameter, pile length, and excitation of ground motion significantly affect the dynamic response of the layered liquefied site. So, in the saturated case, the increase in the piles length to (L/D = 55) in comparison to the original length (L/D = 35) decreased the peak acceleration at the raft foundation by about (24.4 and 41.9) % under the effect of Kobe and Upland earthquake motion, respectively, while in the dry case, the reduction in peak acceleration was about (22.8 and 40.9) % under the effect of Kobe and Upland earthquake motion, respectively.

Enhancing Disaster Resilience for Sustainable Urban Development: Public–Private Partnerships in Japan

A resilient building environment is crucial for securing sustainable development in urban areas, as the 2030 Agenda for Sustainable Development Goal 11 stresses. In developing countries in particular, the risk of disasters is increasing due to the poorly built environment caused by urbanization. However, building disaster resilience in vulnerable urban environments characterized by aging houses, limited public spaces, and complex land rights and tenancy issues poses a major challenge. This study aims to identify critical factors influencing effective disaster-resilient urban development by examining Japan’s experience, with a focus on approaches facilitating public–private partnerships. Driven by disasters like the 1995 Kobe Earthquake, Japan has promoted innovative strategies to improve urban resilience and mitigate disaster impacts. The Disaster Mitigation Zone Implementation Program represents a novel program designed to revitalize densely populated areas with aging wooden structures highly vulnerable to disasters. Through semi-structured interviews, a literature review, and an in-depth case study in Tokyo, this research analyzes the development and effectiveness of this targeted redevelopment approach. Findings underscore the pivotal role of policies promoting public–private collaboration, consensus-building mechanisms among stakeholders, flexibility in project formulation, and financial incentives via government subsidies. Engaging the private sector ensures project feasibility through urban development expertise, while simpler, smaller-scale projects attract greater private investment. Japan’s experience offers valuable insights into collaborative, context-sensitive strategies for enhancing urban disaster resilience through targeted redevelopment of high-risk areas.

Absolute Dating of Fault-Gouge Material Using Isothermal Thermoluminescence: An Example from the Nojima Fault Zone, SW Japan

Establishing the absolute age of palaeoearthquakes is of great significance for the assessment of the seismicity and seismic hazards of a region. As such, several different geochronological techniques to date earthquake-related material have been developed to provide answers on the time of past earthquakes. The present study is part of a wider palaeoseismic research project conducted in the Nojima Fault Zone (NFZ), where the 1995 Mw 6.9 Kobe (Japan) earthquake was triggered, to assess the suitability of the isothermal thermoluminescence (ITL) dating technique on fine-grained quartz and medium-grained feldspar and to provide a sequence of ages for fault-rock samples separated from a drilled core that was retrieved from a depth of ~506 m. Our analysis reveals that ITL can produce consistent dating results and can be considered a reliable luminescence technique for the absolute dating of fault-gouge material. The produced ITL ages signified the existence of repeated seismic events within the NFZ that took place through the late Pleistocene period, with gouge ages spanning from 78.6 ± 4.2 to 13.4 ± 1.4 ka; however, overestimation of the produced ITL dating results may be apparent. Nonetheless, even though some degree of overestimation is considered, ITL dating results denote the oldest possible age boundary of formation (or luminescence signal resetting) of the collected fault-gouge layers.

A questionnaire survey of storytelling experiences among people affected by the 1995 Great Hanshin-Awaji Earthquake in their late primary school years

A questionnaire survey of storytelling experiences among people affected by the 1995 Great Hanshin-Awaji Earthquake in their late primary school years

Comprehensive wood dwelling tests for Post‐and‐Beam and Shear‐Wall structures reflecting foundation boundaries

AbstractThis paper focuses on the ultimate state of three‐story wood dwellings with high aspect ratios, which are increasing in Japan's urban areas. Using shaking table test results from the 2019 full‐scale shaking table test, a comprehensive study is conducted on the accuracy of evaluating ultimate state through the story shear failure mode at the first story, the tension fracture mode at the wall base of the first story, and foundation sliding mode on the soil. Methods evaluating the dynamic response behaviors of the building systems are also investigated. In the test, the current Japanese seismic design guidelines were applied, and two Grade‐3 buildings were prepared. One adopted the Post‐and‐Beam structure (A‐building), and the other the Shear‐Wall structure (B‐building). A series of tests planned very different physical boundary conditions surrounding their reinforced concrete (RC) mat foundations. The sills, column bases and wall bases of the upper wood structures were anchored to the RC foundations by steel anchor bolts, according to the current Allowable Stress Design (ASD) requirements. In the first stage, A‐building equipped a Base‐Isolation system, while B‐building represented a generic foundation constructed on a 1.5 m‐height real soil ground by preparing a rigid soil box (Foundation‐Soil system). In the second stage of A‐building and B‐building, the foundation was firmly fixed (Fixed‐Foundation system), and shaking table motions were fully applied to the foundations. The entire test system was setup on the large shaking table facility at E‐Defense, and a series of tests were conducted using JMA‐Kobe motion and JR‐Takatori motion recorded in the 1995 Kobe earthquake as Maximum‐Considered‐Earthquake motions. Confirmed was the change in the structural mechanism due to the upper structural systems and the foundation boundaries. Regarding the upper wood structure performance in the Fixed‐Foundation system, a story shear failure mode was observed at the first story in A‐building, while a tension fracture mode at the base of the first story in B‐building. This difference of failure mode is difficult to determine with ASD. The maximum strength were more than four times higher than the ASD base shear force. Tension fracture capacity at the wall base was mainly enhanced by the presence of the steel anchor bolts. Regarding the foundation performance in Foundation‐Soil system of B‐building, a horizontal displacement up to 240 mm was observed between the foundation and soil when JMA‐Kobe 100% was applied. A response reduction effect was observed in the upper wood structure, similar to the Base‐Isolation system of A‐building. The initial friction and cyclic friction strength capacities between the foundation and soil were quantitatively evaluated considering the horizontal two‐directional sliding. The representative test results were converted to the corresponding SDOF systems based on the first mode response assessment. In the Fixed‐Foundation system, the dynamic response characteristics of the upper wood structures were properly represented using Ibarra‐Medina‐Krawinkler pinching model in the equivalent SDOF system.

Seismic collapse assessment of single-column bridge piers using the applied element method

Several single-column-bent bridges have collapsed in the past under earthquakes. Different factors associated with poor structural design and/or construction including inadequate and/or prematurely terminated longitudinal reinforcement (LR), insufficient concrete confinement, or insufficient transverse reinforcement (TR) were identified and reported. Different alternative designs or retrofitting solutions were also proposed and examined. One of the well-known samples of this bridge type was the elevated Hanshin Expressway Bridge (HEB), which collapsed in the 1995 Kobe earthquake. In that incident, 18 circular single-column piers (SCPs), monolithically connected to the deck, failed and collapsed. Here, the seismic progressive collapse behaviour of SCPs of the HEB was investigated using non-linear dynamic analyses of three-dimensional numerical models created by way of the applied element method (AEM). The results obtained agreed well with field observations after the earthquake. Two alternative design solutions for improving the seismic response of the original model were also considered and the efficiency of the solutions was assessed. Results showed that the AEM is capable of modelling the progressive collapse procedure for concrete bridges with sufficient accuracy. The results proved greater effects of the anchorage length of the LR as well as the space between the TR in the collapse behaviour of the pier.

Assessment of seismic slope stability of Rangamati Hill Tracts, Bangladesh

Slope stability is an essential aspect of geotechnical engineering. Unstable slopes or stable slopes influenced by external factors may result in a catastrophic disaster called a landslide. In seismically active areas with steep terrain, landslides commonly occur and are regarded as one of the most severe threats. Bangladesh has not suffered any destructive earthquakes in recent years but has a considerable risk of facing such earthquakes owing to its geological conditions. Although slope failures occurring in the Rangamati Hill Tracts of Bangladesh are mainly rainfall-induced, due to the seismic risk in Bangladesh, it is essential to assess earthquake-induced slope failure in vulnerable areas. In this study, the authors analyzed the seismic slope stability at three locations in the Rangamati Hill Tracts using pseudostatic approaches. The pseudostatic approach with the variation in seismic force based on the seismic coefficient was utilized to determine the critical conditions. Using Newmark’s rigid block method, the permanent displacements for various slope conditions were calculated for the Kobe earthquake. The analysis provided crucial insight into the state of the locations. One location has a low factor of safety (FS) value at a slope angle of 30° or greater, whereas the others have a risk of slope failure at a slope angle of 50° or greater. Newmark’s displacement analysis also showed that the slopes at location 3 have the highest displacement at a lower slope angle, with location 1 and location 2 showing relatively better results than location 3. Structural and bioengineered preventive measures are needed in this area to reduce the vulnerability of possible slope failure.

Post-earthquake fire performance of a steel moment-resisting frame

The effects of earthquakes and fires are typically analyzed separately in structural design. However, historical events highlight that fires following earthquake (FFE) can cause significantly more damage than an earthquake alone. The 1906 San Francisco earthquake exemplifies this, with fires destroying 80% of the city. Other major FFE events include Tokyo (1923), Kobe (1995), and Tohoku (2011) earthquakes. Earthquakes can damage infrastructure, leading to potential ignitions and structural fire performance deterioration. This paper focuses on the post-earthquake fire performance of a four-story five-bay steel frame using a probabilistic FFE framework to develop FFE fragility functions and consider uncertainties in the ground motions, compartmentation measures, fire development, and material properties. Damage to structural and non-structural components is considered. In this respect, the probabilistic FFE framework generates the fire scenarios based on seismic response. The seismic response is assessed through nonlinear time-history analyses. Then, post-earthquake fire ignitions in specific compartments are assessed based on the structural damage, determined by inter-storey drift ratio (IDR) and peak floor acceleration (PFA). Compartmentation and opening characteristics as well as the potential for fire spread are considered based on seismic damage in windows, doors, and partition walls following seismic fragility functions found in the literature. Finally, thermomechanical analyses are performed, and failure criteria based on displacement and displacement rate are applied to the beams and columns. The results of the probabilistic analyses were used to produce fragility functions to evaluate the probability of exceeding a limit state conditioned on an intensity measure in the context of FFE. A higher probability of exceeding the collapse limit state with shorter times to collapse was observed when the structure was subjected to higher values of spectral acceleration.

A milestone for liquefaction modelling: the instrumented vertical array of Port Island after the 1995 Kobe earthquake

A milestone for liquefaction modelling: the instrumented vertical array of Port Island after the 1995 Kobe earthquake

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Implementation Gaps Are Persistent Phenomena in Disaster Risk Management: A Perspective Developed After Discussions at IDRiM 2022

Outcomes of a project or a policy often differ from expectations. We call such discrepancies “implementation gaps”. Reasons for these gaps and for their persistence are worth serious study; such study should be a good entry point for developing an implementation science. We wrote a concept paper for a special session at IDRiM 2022; five discussants led a discussion of the paper and of challenges in developing an implementation science. The present paper represents our updated perspective after further reflection and the special session discussions. According to our perspective, the fundamental challenge in describing implementation gaps and then moving toward an adaptable and expansive implementation science is to account for the number and diversity of actors in implementation activities. Different actors have different roles, different capabilities, and powers; their knowledge about the situation is different, and their concerns and perspectives are also different. We begin by considering innovative approaches to describing and characterizing implementation gaps. We construct a model implementation story “a furniture nailing story,” based on real experience in Japan following lessons learned from the Great Hanshin-Awaji earthquake of 1995. We also offer a model implementation failure story “a snowstorm story.” In providing detail, attention to the diversity of actors is key; further analysis begins with a deeper characterization of actors and their relationships, influences, and interactions with each other. We proceed to discuss steps toward an implementation science. We consider three aspects of science: 1) description: characterizing gaps, classifying them, and making classifications useful; 2) designing and testing: finding models for implementation processes and seeing how they work; 3) prediction: anticipating and preparing for challenges and opportunities in implementation. Finally, we consider possibilities for learning from experiences in other fields and recommend modest attempts to develop new dialogues with “prospective neighboring disciplinary communities.”

Numerical Simulation of Pile Group Response in Slope Layered Soil under the Effect of Seismic Loading

This work investigates the effect of earthquakes on the stability of a collective pile subjected to seismic loads in the soil layer. Plaxis 3D 2020 finite element software modeled pile behavior in dry soils with sloping layers. The results showed a remarkable fluctuation between the earthquakes, where the three earthquakes (Halabja, El Centro, and Kobe) and the acceleration peak in the Kobe earthquake had a time of about 11 seconds. Different settlement results were shown, as different values were recorded for the three types of earthquakes. Settlement ratios were increased by increasing the seismic intensity; hence the maximum settlement was observed with the model under the effect of the Kobe earthquake (0.58 g), where subsidence values at the three tremors differed between the pile distribution pattern. The highest drop recorded by the results was 60 mm in a distribution pattern 2×3. In general, increasing the size of the cap leads to an additional drop due to the weight of the cap.