Search

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]

In China, conventional island shield buildings (CISBs), which are situated close to the nuclear islands of nuclear power plants, are class III seismic items. This is the most important level in the seismic fortification standard. Calculations to check resistance overturning under extremely safe seismic action should be carried out. Although strict seismic design has been carried out, many beyond-design-basis events, such as the 3/11 earthquake in Japan, have occurred in recent years. Under the action of such accidental loads, there is still the possibility that the important vertical bearing components of a CISB will be damaged or destroyed, which will lead to the progressive vertical collapse of the CISB structure, and ultimately threaten the safe operation of the nuclear power plant. Therefore, it is necessary to study the progressive collapse resistance mechanism of the CISB in order to further optimize and improve its design. In this paper, we take the CISB as a research object and consider the failure mechanism of its vertical progressive collapse synthetically, using SAP2000 finite element software to study the causation and strength of resistance force and internal force redistribution characteristics due to progressive collapse under different column removal conditions (long-side middle, short-side middle, internal, and corner columns) using the instantaneous unloading method. The results show that the residual structure is at risk of collapse under the corner and long-edge middle column removal conditions, and there is no risk of collapse under the short-edge middle and internal column conditions. The failure and collapse resistance of the corner column only has a beam mechanism, and the long-side middle column forms a catenary mechanism in the Y direction. The short-side middle column can resist collapse by the beam mechanism, while the internal column forms a bidirectional catenary mechanism in the X and Y directions. The axial force of the column in the residual structure is mainly redistributed to column members with adjacent spans to the failure column, and column members with separated spans are less affected. [ABSTRACT FROM AUTHOR]

Assessing the nonlinearity of a site plays a crucial role in earthquake engineering. For some building structures and lifeline projects that need safety assessment after earthquakes, the analysis of nonlinear degree of sites can help accurately revealing the amplification effect of sites and evaluating the damage degree of buildings which is convenient for subsequent reinforcement and demolition work. The quantitation of nonlinear threshold of sites is an important method to evaluate the degree of site nonlinearity. In this paper, a nonlinear characteristic index reflecting the degradation of shear modulus is proposed based on the instantaneous frequency of the site calculated by using the vector auto-regression moving average (VARMA) model. Then, seismic records of class I, II, III and IV sites specified as per code for seismic design of buildings in China are selected from the KiK-net network in Japan, and the threshold value of ground motion acceleration characterizing the nonlinear response of sites are provided. Finally, the variation of the nonlinear characteristic index (shear modulus degradation) vs. different (peak ground acceleration) PGA for four types of sites are presented. [ABSTRACT FROM AUTHOR]

Sand compaction piling is one of the commonly used countermeasures for earthquake liquefaction hazard of river dikes. This paper presents a case study of the performance of an instrumented dike in northeast Japan that was improved by sand compaction piles and subjected to the 2003 Northern Miyagi Earthquake, with the aim to better understand the effectiveness of this ground improvement method. Simulation has been carried out by means of a fully coupled numerical procedure which employs a sophisticated cyclic elastoplastic constitutive model and the updated Lagrangian algorithm. Comparisons between the field measurements and the computed responses, including the time histories of accelerations and pore-water pressures at different locations, show reasonably good agreement. Numerical simulation has also been made of the same dike but without ground improvement to identify the effects of sand compaction piles in altering the performance of the dike. The study demonstrates that the comprehensive numerical procedure is a promising tool for development of seismic performance-based design of earth structures. [ABSTRACT FROM AUTHOR]

Coupled building control has been shown to be an effective means of protection for flexible building structures. Numerous researchers have proposed various active, passive, and semiactive coupled building control strategies for both high-rise and low-rise buildings. Actual applications of coupled building control for low-rise buildings and high-rise buildings have been successfully implemented in Japan using passive and active control technology. Much of the research in the literature has focused on specific building pairs. To date, there have been no detailed studies of the effects of the building configuration and connector location on the overall system performance. This paper examines these effects and compares the efficacy of passive and active coupled building control for flexible adjacent buildings. [ABSTRACT FROM AUTHOR]

Seismic design guidelines for composite reinforced concrete and steel (RCS) buildings consisting of reinforced concrete columns and structural steel beams were proposed in Japan as a practical outcome of the U.S.–Japan Cooperative Earthquake Research Program on Composite and Hybrid Structures. A design method satisfying the most prevalent seismic provisions used in Japan, which are based on the working stress design method, is described. At the same time, an alternative method, which is suitable for use in the context of the capacity spectrum method, is also briefly introduced. This paper outlines the design guidelines, giving priority to an explanation of the design method for the working stress seismic provisions. In this method, the weak beam–strong column mechanism is used as the design basis for buildings under severe earthquake. Therefore, moment magnification factors for both columns and joint panels are provided to secure the mechanism. Design equations for the ultimate shear strength of joint panels and associated hysteresis models are also included in the guidelines, and can be applied to a total of twelve details of RCS beam–column joints, including both the through beam and the through column types. [ABSTRACT FROM AUTHOR]

As part of the U.S.-Japan Cooperative Research Program on Composite/Hybrid Structures (1992), investigations were carried out at the University of Nebraska-Lincoln and University of Illinois, to develop moment connection details and accompanying design provisions for connecting steel beams to circular concrete filled tube (CFT) columns. This paper provides an overview of the work carried out. Work at the University of Illinois consisted of evaluating the inelastic response of six possible connection details. Six large-scale connections were tested to failure using the quasi-static test method. Connections welded to the skin of the tube created large distortions of the tube wall, and were susceptible to weld, flange, or tube wall fracture. External diaphragm and continuous web details exhibited more favorable inelastic behavior, but the flexural strength of these connections began to deteriorate relatively early in the imposed deformation history. Continuing the flanges through the composite column showed adequate strength, however due to excessive slipping this connection did not dissipate significant inelastic dynamic energy. One of the details tested at the University of Illinois was passing the girder section through the CFT columns. This through beam detail provided the most effective detail to achieve the ideal rigid connection condition. Work at the University of Nebraska-Lincoln concentrated on comprehending the behavior of the through beam connection detail. The behavior of CFT columns under seismic loads was studied through testing six columns which were subjected to a constant axial load in addition to a cyclic lateral load. Failure modes for through beam connection detail were identified through testing seven, two-thirds scale connection specimens. These tests were used to comprehend the force transfer mechanisms between steel beams and CFT columns and develop design provisions that could estimate the capacity of the various elements of the through beam connection detail. [ABSTRACT FROM AUTHOR]

In the design of beam-to-column subassemblies in concrete-filled steel tubular column systems, a design formula established by the Architectural Institute of Japan (AIJ) is applied. However, in the current AIJ standard, the scope of the design formula is limited to ordinary material strengths; i.e. up to an unconfined compression strength of 36 MPa for concrete and tensile strength of 490 MPa for structural steel tubes. So, the effect of higher material strengths on subassembly behavior is studied in this investigation. The experimental results presented in this paper verified that the above-mentioned AIJ design formula is applicable up to an unconfined compression strength of 110 MPa for concrete and tensile strength of 809 MPa for structural steel tubes. An analytical model for the restoring force characteristics of the shear panel in the subassemblies was also proposed, and was found to reproduce the experimental results with good accuracy. [ABSTRACT FROM AUTHOR]

Site amplification factors (SAFs) of seismic ground motions are essential in evaluating and estimating seismic hazards. In our previous study, the authors proposed a simple and cost-effective method to estimate a SAF based on a deep neural network (DNN) model and microtremor horizontal-to-vertical spectral ratio (MHVR). Since the previous DNN model was based on the observed SAFs and MHVRs within a limited district in Japan, the applicability of the previous model to non-source regions with different site conditions was limited. This study explored the application of a transfer learning (TL) technique to adapt an existing (pre-trained) DNN model to new regions and a different database. The SAFs obtained through generalized spectral inversion technique (GIT) at the seismic observation stations (K-NET and KiK-net) in Japan were collated as the ground truth for site effects. MHVRs recorded at the stations in several districts of Japan were collected to construct a data set for the development of the TL model. Subsequently, a TL model was constructed, leveraging the neural network layers and their weights from the pre-trained model while incorporating additional neural network layers to enhance the performance. During the training process, a total data set of 112 sites was divided into training set, validation set, and external test set by 1:1:5. Utilizing a cross-validation strategy, the residuals between pSAFs (pseudo-SAFs) estimated by the TL model and the observed SAFs were analysed for the external test set containing 80 sites. The results showed that the TL model outperformed the pre-trained DNN model. The cross-validation results demonstrated that almost consistent prediction results were obtained regardless of any combination of 16 sites selected as the training set. Furthermore, by contrasting the influence of varying training set sizes on the performance of the TL model and comparing the TL model to a DNN model with an extended training set, the effectiveness of constructing the model with the limited number of data (16 sites) was ascertained. Finally, the effectiveness and limitations of the TL model were evaluated using MHVRs with peak frequencies falling outside the training set's range. [ABSTRACT FROM AUTHOR]

This paper verifies the feasibility of the proposed system identification methods by utilizing shaking table tests of a full-scale four-story steel building at E-Defense in Japan. The natural frequencies, damping ratios and modal shapes are evaluated by single-input-four-output ARX models. These modal parameters are prepared to identify the mass, damping and stiffness matrices when the objective structure is modelled as a four degrees of freedom (4DOF) linear shear building in each horizontal direction. The nonlinearity in stiffness is expressed as a Bouc-Wen hysteretic system when it is modelled as a 4DOF nonlinear shear building. The identified hysteretic curves of all stories are compared to the corresponding experimental results. The simple damage detection is implemented using single-input-single-output ARX models, which require only two measurements in each horizontal direction. The modal parameters are equivalent-linearly evaluated by the recursive Least Squares Method with a forgetting factor. When the structure is damaged, its natural frequencies decrease, and the corresponding damping ratios increase. The fluctuation of the identified modal properties is the indirect information for damage detection of the structure. Copyright © 2015 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Ground motion prediction is an important and complex research subject in earthquake engineering and traditional approaches based on statistical regression have much room for improvement in prediction accuracy. Utilizing the 67,164 ground motion records from KiK-net and K-Net for 777 shallow crustal earthquakes between 1997 and 2019 in Japan, this paper proposes a ground motion prediction model XGBoost-SC based on the machine learning algorithm of eXtreme Gradient Boosting (XGBoost) for Japan. Magnitude, focal depth, hypo-central distance, V s30 , site altitude, and focal mechanism were used as the feature parameters, and XGBoost, Random Forest, and Deep Neural Networks (DNN) algorithms were selected for model training while Bayesian optimization was used to search for optimized hyperparameters to improve the prediction accuracy. XGBoost algorithm was selected for further study based on the comparison of results from the three algorithms. Residual change with magnitude and hypo-central distance, the probability distribution of residuals, residual standard deviation (σ), residual mean squared error (MSE), and Pearson correlation coefficient (R) were used as the evaluation parameters, and a comparison study was performed against the ground motion prediction equation based on traditional approaches. Actual earthquake events were selected to compare the prediction results against the observation records. To further validate and explain the proposed model, SHapley Additive exPlanations (SHAP) analysis was performed to explain the impact of selected feature parameters on the proposed model. The results demonstrate that the proposed XGBoost-SC model has good prediction stability for all periods, and its residual errors are smaller than those of other models. Therefore, the proposed model can better reflect the ground motion attenuation for shallow crustal earthquakes in Japan and can serve as a better model for ground motion prediction in future aseismic design and earthquake disaster mitigation efforts. • A Ground Motion Prediction Model was proposed for shallow crustal earthquakes. • The proposed model was more precise than traditional approaches. • Explained the effect of feature parameters on the prediction results. [ABSTRACT FROM AUTHOR]

With the improvement of the world's largest seafloor observation network (S-net) and the increase in the quantity and quality of records, the ergodic assumptions can be further relaxed in the modeling of offshore ground motion models (GMMs). This allows accounting for systematic and repeatable source, site, and path effects to further understand the characteristics of offshore ground motion in the Japan Trench region. We developed an offshore ergodic backbone GMM for subduction earthquakes and classified the sites into four categories using horizontal–vertical response spectral ratio to investigate site amplification. The offshore ergodic GMM is applicable for subduction earthquake scenarios with moment magnitudes ranging from 4.0 to 7.4 and rupture distances ranging from 10 to 300 km. Comparing offshore ergodic GMMs with onshore GMMs for subduction earthquakes, we found that offshore GMMs were significantly different from onshore GMMs, especially in the long-period and unburied states. Then a new offshore non-ergodic GMM was developed based on the offshore ergodic GMM. The systematic and repeatable source and site effects were captured by the spatially varying coefficients represented by Gaussian processes, while the systematic and repeatable path effects were captured by cell-specific anelastic attenuation proposed by Dawood and Rodriguez-Marek (2013), calculated with the Cohen-Sutherland computer graphics algorithm. The non-ergodic GMM revealed systematic and repeatable source, site, and path effects that were not captured by the ergodic GMM. Moreover, the non-ergodic GMM showed reduced aleatory variability and epistemic uncertainty on ground motion estimation compared to ergodic GMM. The reduction of aleatory variability and epistemic uncertainty had a significant impact on probabilistic seismic hazard analysis. Quantifications of these results are contributed to conduct reasonable seismic design and seismic risk assessment for marine engineering in offshore regions vulnerable to strong subduction earthquakes. [ABSTRACT FROM AUTHOR]

• The influence of openings on the strength and stiffness of cross-laminated timber (CLT) walls was experimentally evaluated. • The reduction in stiffness for CLT walls due to openings is relatively greater than that in strength. • Panels with rectangular openings with different orientations had different failure direction and reduction factors. The high in-plane shear strengths of cross-laminated timber (CLT) make it a good candidate for use as shear walls in buildings in areas of high seismicity such as Japan. One important aspect of CLT walls, and one that is presently poorly understood, is the influence of openings on the in-plane shear carrying capacity. The main purpose of this paper is to experimentally evaluate the effect of openings on the in-plane strength and stiffness of CLT panels with openings. In this study, 24 CLT panels were tested using a diagonal compression test configuration. In particular, they were three identical replicates of eight CLT panels. One of these eight panels was a solid panel, while the other seven panels had openings with different sizes and aspect ratios. The results showed that the panels with openings with the same area but different aspect ratios had different failure directions and reduction factors for panel shear strength and stiffness. Panels with rectangular openings with different orientations relative to the panel's major and minor shear direction had different failure direction and reduction factors. In addition, the effect of openings on the reduction of initial stiffness for CLT panels was found to be greater than their effect on the reduction of shear strength. This paper's findings will help clarify the reduction in strength and stiffness of CLT panels with openings, which is an important aspect of the seismic design of buildings. [ABSTRACT FROM AUTHOR]

Conventional simplified analysis methods for seismic design of gravity-type quay wall are based on providing capacity to resist a design seismic force, but they do not provide information on the performance of a structure when the limit of the force-balance is exceeded. In order to overcome the limitation of conventional seismic design methods, a performance-based seismic coefficient (k hk) concept which can verify the performance of port structures exceeding the limit of force-balance was proposed in the technical standards and commentaries for port and harbour facilities in Japan, published in 2007. The k hk concept considers the deformation of the quay wall, the wall height, the effect of frequency characteristics and duration of the ground motions, and the natural period of the ground. This paper proposes a performance verification method for the gravity-type quay wall during earthquakes through dynamic centrifuge model tests. The centrifuge tests were used in the present study to validate the proposed k hk concept for evaluating the seismic performance of the quay wall under various conditions. The reliability of the k hk concept was evaluated for different wall heights, earthquake motions and the thickness of subsoil, which are the primary variables in the k hk equation. In addition, some improvements that should be considered in the future revision of the k hk equation are discussed in this research. • Performance-based seismic coefficient (k hk) concept for gravity-type quay walls is evaluated by dynamic centrifuge tests. • Important parameters for k hk equation arewall height, thickness of subsoil, and frequency content of earthquake motions. • A procedure to verify the k hk equation by comparing the measured and the allowable deformation of quay wall is suggested. • Some improvements that should be considered in the future revision of the k hk equation are discussed. [ABSTRACT FROM AUTHOR]

Modern seismic design and technologies have undergone tremendous developments. In modern design codes, building structures subjected to high earthquake loads are allowed to experience plastic deformations without collapsing, and the design is permitted up to the ultimate strength. According to comparative results in Japan, the number of humans injured due to earthquakes is higher than the number of deaths/missing. Likewise, the number of residential buildings that collapsed are less than the partially damaged buildings. This outcome implies that residential buildings designed based on the revised seismic standards have good earthquake resistances. It also infers that the human deaths/injury casualties were not a result of the collapsed the structure, but due to the strong vibrations originated from the earthquake, yielding in the collapse of non-structural elements such as ceilings and bookshelves. This paper presents a proposed design philosophy that attempts to implement the effect of earthquakes to non-fatal human casualties. [ABSTRACT FROM AUTHOR]

Abstract: In the afternoon of March 11, 2011, the eastern Japan was severely attacked by the 2011 off the Pacific coast of Tohoku earthquake (the Great East Japan earthquake). Nearly 30,000 people were killed or are still missing by that earthquake and the ensuing monster tsunami as of April 11, 2011. This paper reports some aspects of this devastating earthquake which hit an advanced country in seismic resistant design. It has been reported that long-period ground motions were induced in Tokyo, Nagoya and Osaka. The properties of these long-period ground motions are discussed from the viewpoint of critical excitation and the seismic behavior of two steel buildings of 40 and 60 stories subjected to the long-period ground motion recorded at Shinjuku, Tokyo is determined and discussed. This paper also reports the effectiveness of visco-elastic dampers like high-hardness rubber dampers in the reduction of responses of super high-rise buildings subjected to such long-period ground motions. The response reduction rate is investigated in detail in addition to the maximum response reduction. In December 2010 before this earthquake, simulated long-period ground motions for earthquake resistant design of high-rise buildings were provided in three large cities in Japan (Tokyo, Nagoya and Osaka) and nine areas were classified. Two 40-story steel buildings (slightly flexible and stiff) are subjected to these long-period ground motions in those nine areas for the detailed investigation of response characteristics of super high-rise buildings in various areas. [Copyright &y& Elsevier]

Presented in this paper is the original seismic design and the seismic performance retrofit study against large-scale earthquakes of the Akashi Kaikyo Bridge. The Akashi Kaikyo Bridge is the world's longest suspension bridge and was completed in 1998. In the original seismic design, an inland near-field earthquake with large magnitude was not considered for the seismic design force. Although the bridge encountered the Hyogo-ken Nanbu Earthquake in 1995, it was not seriously damaged since the earthquake occurred during its construction. Therefore, a seismic performance retrofit study against large-scale earthquakes has been started. In the seismic performance retrofit study, site-specific large-scale earthquakes including inland near-field earthquakes were defined based on the latest seismological information. As a result, it was found that target seismic performance was ensured by taking some minor countermeasures. [ABSTRACT FROM AUTHOR]

An Earthquake ML= 6.8 occurred on October 23, 2004 in Chuetsu area of Niigata County in Japan, which caused 40 people dead, more than 4500 people injured and 1000000 people homeless; nearly 140000 buildings were damaged or collapsed. The estated total loss of this earthquake was about 3000 billions Yen. In this paper, we investigate the Chuetsu earthquake damage from different aspects, including the seismic outline, seismicity, intensity distribution, wave feature, damage analyses, and economic losses. Finally, experiences and lessons from the earthquake damage are given. The content in this paper may be a reference for structural seismic design and code modification. [ABSTRACT FROM AUTHOR]

Many embankments have been constructed in Japan, but most have lacked seismic design, except for important embankments, such as earth dams. However, because embankments are often damaged by large earthquakes, seismic inspections have recently been carried out on existing embankments, and countermeasures have been taken to deal with unstable embankments. This paper describes the seismic inspection methods and countermeasures currently implemented in Japan for river dikes, tailings dams, and embanked residential lands. River dikes are dangerous when they subside and their crests become lower than the river water levels. Therefore, seismic inspections are being carried out using a simple static method to analyze the amount of subsidence against level 2 seismic motion. Countermeasures are being taken, such as compacting the ground under the vicinity of the toe of a dike. For tailings dams, dynamic analysis is performed for level 2 seismic motion, and seismic inspection is performed based on the amount of slip displacement. As countermeasures, solidification etc. have been implemented. There are 51,306 large residential areas embanked in hilly valleys in Japan. Soil investigations and stability analyses will be conducted in these areas as secondary screenings, and these areas are currently being prioritized for such screenings. It will likely be many years before the screenings and countermeasures are completed. • Most of the embankments are not seismically designed and are damaged during earthquakes. • Seismic inspection of embankments is necessary to prevent damage during earthquakes. • In Japan, inspections are being conducted on river dikes, tailings dams, residential areas. • Countermeasures are being taken at river dikes where settlement causes flooding. • Since there are 51,306 embanked residential areas, screening priorities are being determined. [ABSTRACT FROM AUTHOR]

In light of the significant damage observed after earthquakes in Japan and New Zealand, enhanced performing seismic force‐resisting systems and energy dissipation devices are increasingly being utilized in buildings. Numerical models are needed to estimate the seismic response of these systems for seismic design or assessment. While there have been studies on modeling uncertainty, selecting the model features most important to response can remain ambiguous, especially if the structure employs less well‐established lateral force‐resisting systems and components. Herein, a global sensitivity analysis was used to address modeling uncertainty in specimens with elastic spines and force‐limiting connections (FLCs) physically tested at full‐scale at the E‐Defense shake table in Japan. Modeling uncertainty was addressed for both model class and model parameter uncertainty by varying primary models to develop several secondary models according to pre‐established uncertainty groups. Numerical estimates of peak story drift ratio and floor acceleration were compared to the results from the experimental testing program using confidence intervals and root‐mean‐square error. Metrics such as the coefficient of variation, variance, linear Pearson correlation coefficient, and Sobol index were used to gain intuition about each model feature's contribution to the dispersion in estimates of the engineering demands. Peak floor acceleration was found to be more sensitive to modeling uncertainty compared to story drift ratio. Assumptions for the spine‐to‐frame connection significantly impacted estimates of peak floor accelerations, which could influence future design methods for spines and FLC in enhanced lateral‐force resisting systems. [ABSTRACT FROM AUTHOR]

This study proposes offshore ground motion models (GMMs) for Arias intensity and cumulative absolute velocity by using the seafloor ground motion database in the Japan Trench area. Whether the station is buried or not will have a great influence on the Arias intensity and cumulative absolute velocity. Compared with existing GMMs, as the magnitude increases, the energy accumulation effect of offshore GMMs is greater than that of onshore GMMs with similar magnitude and distance, and the attenuation rate is slower than other models. The proposed GMMs can be used for seismic hazard and risk analysis in the Japan Trench area. [ABSTRACT FROM AUTHOR]

Classification of local soil conditions is important for the interpretation of structural seismic damage, which also plays a vital role in site‐specific seismic hazard analyses. In this study, we propose to classify sites as an image recognition task using a deep convolutional neural network (DCNN)‐based technique. We design the input image as a combination of the topographic slope and the mean horizontal‐to‐vertical spectral ratio (HVSR) of earthquake recordings. A DCNN model with five convolutional layers is trained using 1649 sites in Japan. The recall rates for site classes C, D, and E using our DCNN classifier for Japanese sites are 82%, 70%, and 60%, respectively. When compared with existing site classification schemes relying on predefined standard HVSR curves, our proposed method achieves the highest total accuracy rate (between 73% and 75%). The generality and applicability of our trained classifier are further validated using sites in Europe with a total accuracy between 64% and 66%. The proposed data‐driven approach could be extended to other types of site amplification functions in the future. [ABSTRACT FROM AUTHOR]

Time-domain analyses of seismic waveforms have revealed diverse source complexity in large earthquakes (M w > 7). However, source characteristics of small earthquakes have been studied by assuming a simple rupture pattern on the frequency domain. This study utilizes high-quality seismic network data from Japan to systematically address the source complexities and radiated energies of M w 3–7 earthquakes on the time domain. We first determine the apparent moment-rate functions (AMRFs) of the earthquakes using the empirical Green's functions. Some of the AMRFs show multiple peaks, suggesting complex ruptures at multiple patches. We then estimate the radiated energies (ER) of 1736 events having more than ten reliable AMRFs. The scaled energy (eR = ER / M 0) does not strongly depend on the seismic moment (M 0), focal mechanisms, or depth. The median value of eR is 3.7 × 10−5, which is comparable to those of previous studies; however, eR varies by approximately one order of magnitude among earthquakes. We measure the source complexity based on the radiated energy enhancement factor (REEF). The values of REEF differ among earthquakes, implying diverse source complexity. The values of REEF do not show strong scale dependence for M w 3–7 earthquakes, suggesting that the source diversity of smaller earthquakes is similar to that of larger earthquakes at their representative spatial scales. Applying a simple spectral model (e.g. the ω 2-source model) to complex ruptures may produce substantial estimation errors in source parameters. [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]

Two external types of precast, prestressed concrete seismic retrofit methods were applied in two school buildings in Miyagi prefecture, which was strongly affected by the Tohoku earthquake of March 11, 2011. Following the earthquake, inspection showed no damage other than small cracks in the retrofitted buildings. The paper describes how the calculations were performed and the basic construction procedures. [ABSTRACT FROM AUTHOR]

The 2008 Iwate-Miyagi Nairiku earthquake (Mw 6.9, Mjma 7.2) occurred on 14 June 2008 in Japan. The amplification and asymmetric waveform of the vertical acceleration at the ground surface recorded by accelerometers at station IWTH25, situated 3 km from the source, were remarkable in two ways. First, the vertical acceleration was extremely large (PGA = 38.66 m/s² for the vertical component, PGA = 42.78 m/s² for the sum of the three components). Second, an unusual asymmetric waveform, which is too far above the zero acceleration axis, as well as large upward spikes were observed. Using a multi-degree-of-freedom (MDF) system consisting of a one-dimensional continuum subjected to vertical acceleration recorded at a depth of 260 m below ground level, the present paper clarifies numerically that these singular phenomena in the surface vertical acceleration records occurred as a result of the jumping and collision of a layer in vertical motion. We herein propose a new mechanism for such jumping and collision of ground layers. The unexpected extensive landslides that occurred in the area around the epicenter are believed to have been produced by such jumping under the influence of vertical acceleration. [ABSTRACT FROM AUTHOR]

This paper is concerned with the design of a robust, state-feedback, delay-dependent H∞ controller for an active vibration control of seismic-excited structural systems having actuator delay, norm bounded uncertainties, and L2 disturbances. The norm bounded uncertainties are assumed to exist in variations of structural stiffness and damping coefficients. Based on the selection of Lyapunov-Krasovskii functional, first a bounded real lemma (BRL) is obtained in terms of linear matrix inequalities (LMI5) such that the nominal, time-delay system is guaranteed to be globally asymptotically stable with minimum allowable disturbance attenuation level. Extending BRL, sufficient delay-dependent crite,ia are developed for a stabilizing H∞ controller synthesis involving a matrix inequality for which a nonlinear optimization algorithm with LMIs is proposed to get feasible solution to the problem. Moreover, for the case of existence of norm-bounded uncertainties, both the BRL and H∞ stabilization criteria are easily extended by employing a wellknown bounding technique. Then, a cone complementary algorithm is also utilized to solve the nonconvex optimization problem. By use of the proposed method, a suboptimal controller with maximum allowable delay bound, uncertainty bound and minimum allowable disturbance attenuation level can be easily obtained by solving the proposed convex optimization technique. A four-degree-of-freedom uncertain structural system subject to seismic excitations is used to illustrate the effectiveness of the approach through simulations. Simulation results, obtained by using real time-history data of Kobe and Kocaeli earthquakes show that the proposed controller is very effective in reducing vibration amplitudes of storeys and guarantees stability at maximum actuator delay and parametric uncertainty bound. [ABSTRACT FROM AUTHOR]

Abstract: In the current Japanese bridge design code, the seismic load of only one direction (1-dimension, 1-d) is considered. However, in fact, an actual seismic load has three components for N–S (north–south), E–W (east–west) and U–D (up–down) directions. The current paper presents a series of numerical results of steel box columns, which are used as piers of viaduct, under 3-d seismic load with 3 components. Two types of ground motion patterns of the main shock and the maximum aftershock measured in the Chuetsu Earthquake in 2004 are used as the seismic load. The results indicate that the severer deformation arises in the columns under 2-d (N–S and E–W components) or 3-d seismic load than the 1-d load by the main shock. However, under the aftershock, which contains ground motion of higher frequency, 1-d load gives larger displacement. [Copyright &y& Elsevier]

Abstract: During a severe earthquake, most moment-resisting steel framed structures are designed and detailed to resist the earthquake through a combination of strength and damage, where the damage occurs in specific, controlled locations in the beams. Contrary to prior opinion and practice, the Northridge and Kobe earthquakes of the mid 1990s showed that the ability of steel structures to deliver this behaviour is not a given, but is dependant on careful design and detailing, and on how the material behaves under the accumulation of damage. This paper focuses on the latter topic and develops a simple and powerful damage parameter to predict failure in the flange of a beam undergoing inelastic action under any loading history. This can be used to illustrate the influence of different loading regimes and to determine element failure in a finite element model. [Copyright &y& Elsevier]

Abstract: The nonlinear behavior of basemat uplift, which is an important point in seismic designs of nuclear power plants in Japan, has been investigated by arranging joint elements between the reactor building basemat and the soil on a three-dimensional (hereafter referred to as 3D) FEM model of the soil. However, the nonlinearity of the basemat uplift has been investigated separately from the nonlinearity of reactor buildings. These nonlinearities have yet to be taken into account simultaneously in past studies. In this paper, models of the building and the soil using 3D FEM elements with consideration to the nonlinearity of building materials as well as the nonlinearity of the basemat uplift were subjected. The behavior of the building''s elements were investigated by carrying out seismic response analyses for horizontal ground motions only, as well as for simultaneous horizontal and vertical ground motions using these models. As a result, it was found that there was little difference in the horizontal response of the building between the horizontal input motions only and the simultaneous horizontal and vertical input motions. The effects of the vertical ground motions on the basemat uplift behavior which is represented by the ground contact ratio were also slight. [Copyright &y& Elsevier]

Built-up box columns are more frequently used in earthquake-prone regions such as Japan and Iran. As the installation process of continuity plates and welding inspection are difficult, expensive, and time-consuming, this study was aimed at experimentally and numerically investigating continuity plate elimination from built-up box columns with regard to the seismic design specifications of special and intermediate moment resisting frames. Results of an experimental study of three full-scale rigid connections between I-beam and box-column subjected to cyclic loading were used for comparison and verification of numerical results. Experimental study showed that samples reached story drift angle of 0.06 radians before experiencing the permissible strength degradation. Therefore, the tested connections satisfied the criterion for special moment resisting frame (SMRF) in AISC. Based on observations of crack initiation and propagation in the experimental study, a rupture index (RI) was employed to investigate the effects of different complete joint penetration (CJP) groove welding methods used in the experimental study on connection ductility as well as to identify the regions prone to crack initiation and propagation. Both the numerical and experimental results showed the superiority of using back plate in CJP welding. [ABSTRACT FROM AUTHOR]

Presents a study which discussed the similarities and differences in steel moment frames for seismic design between the United States and Japan. Details on the effect of earthquake to the frames in Japan; Conclusions.

• A novel controlled-rocking concentrically braced frame (CR-CBF) system is developed. • Seismic performance of the (CR-CBF) system is evaluated by using incremental dynamic procedure (IDA). • The developed CR-CBF shows an efficient safety margin against collapse under different hazard intensities. • The new CR-CBF can be used as an alternative earthquake resisting system. Recent earthquakes in New Zealand and Japan showed that structures designed according to modern building codes might suffer significant damages with hefty financial and social losses. The primary reason lies in the seismic design approach, where most seismic force resisting systems (SFRS) were designed to prevent structures from collapse during strong earthquake shaking, without considering the damage and the usability of the structure after an earthquake. In this paper, a controlled rocking-concentrically braced frame (CR-CBF) is proposed. CR-CBF is a fused structural system that uses a combination of post-tensioned tendons (PTs) and energy dissipation devices (EDs) to create a controlled-rocking mechanism to minimize structural repair costs and down time after a strong earthquake. PTs are placed in the structure to provide the restoring forces and to minimize any residual deformation in the structure, while EDs are placed at the base of a structure to dissipate the earthquake energy. To ensure the CR-CBF can achieve high performance, two (CR-CBF) prototypes with different heights are designed using the novel equivalent energy design procedure (EEDP). The EEDP procedure allows designers to select different performance objectives at different shaking intensities. The results of nonlinear dynamic analyses of the CR-CBFs show that CR-CBFs have superior seismic performances as intended and can be efficiently designed using EEDP. Finally, the seismic performance of CR-CBF against collapse is assessed using incremental dynamic analysis (IDA) outlined in the FEMA-P695 methodology. The results show that the CR-CBFs designed by EEDP have sufficient safety against collapse, hence it can be used as an efficient seismic force resisting system. [ABSTRACT FROM AUTHOR]

The deterioration of existing reinforced concrete (RC) structures is regarded as a problem worldwide. In Japan especially, the deterioration of RC dam structures has become severe. Many such dams meet design standards that were in place at the time of construction but do not meet the current seismic design standards, and appropriate seismic retrofitting is required. If the dam pier, which is an important part of the dam related to water storage, is damaged by an earthquake, the gate cannot be opened or closed, and the amount of water stored cannot be controlled. Therefore, the seismic retrofitting of dam piers is a top priority. However, various construction restrictions exist for dam piers, such as only the cross-section on the downstream side can be reinforced, and not on the upstream side where water is stored. Thus, it is difficult to apply the same reinforcement method that is applied to the piers of general road bridges. Therefore, in this study, we confirm the effectiveness of the SRS method (seismic retrofitting using cement mortar for shotcrete), which is suitable for partial reinforcement. Specifically, the dam piers of four types of existing dams were modeled using the three-dimensional finite element method, and a seismic response analysis was performed by inputting two types of seismic waveforms having different characteristics. As a result, the reinforcement effect of this method was verified according to structural characteristics. Furthermore, the effect of the reinforcement range on the reinforcement effect was clarified. [ABSTRACT FROM AUTHOR]

Verifying the seismic performance of port structures when the force balance limit is exceeded is important for the performance-based seismic design of gravity-type quay walls. Over the last three decades, performance verification methods have been developed that consider the effects of the design earthquake motion, geotechnical conditions, and structural details on the deformation of a quay wall to accurately predict earthquake-induced damage. In this study, representative performance verification methods (i.e., simplified dynamic analysis methods extending from the Newmark sliding block method and performance-based seismic coefficients developed in Japan) were quantitatively assessed with actual cases of earthquake-damaged quay walls and the results of dynamic centrifuge tests previously conducted under various conditions (i.e., different wall heights, earthquake motions and the thickness of subsoil). The dynamic centrifuge test results suggested directions for improving the performance-based seismic coefficients of the representative methods, while their field applicability and reliability were confirmed according to the actual earthquake records. [ABSTRACT FROM AUTHOR]

Probabilistic seismic hazard analysis (PSHA) is carried out during the seismic design of structures, and a seismic load corresponding to a certain return period is calculated. In PSHA, there are cases where a renewal process is adopted for some large specific earthquakes. When the probability of the occurrence of an earthquake increases within a certain period, the seismic load based on PSHA also increases. Here, we study the temporal change of the seismic hazard and the influence of the epistemic uncertainty on the occurrence probability of a large earthquake around Japan. When calculating the occurrence probability of earthquakes around the Nankai Trough and the Sagami Trough, the occurrence history is not clearly known, hence, a large epistemic uncertainty arises about the parameters of the Brownian Passage Time (BPT) distribution, such as the average recurrence interval, and the aperiodicity parameter alpha. In order to consider such uncertainty, we employ the Monte Carlo method with a large number of input parameters to grasp the temporal change of the occurrence probability. In addition, the calculated occurrence probability is incorporated into the seismic hazard analysis. Here, we conduct a risk assessment for sample sites and discuss the notion that the influence of the epistemic uncertainty on seismic loads varies greatly from one region to another. [ABSTRACT FROM AUTHOR]

In light of the disastrous the 2011 Tohoku Pacific Earthquake, the government of Japan has conducted studies to revise the seismic design code, and elevated peak ground accelerations have been adopted. Consequently, revisions on existing design to comply with the updated code are required for public projects that are still undergoing. The design safety needs to be reassessed, and implementation of strengthening measures is required if deemed necessary. For liquefaction countermeasures, ground treatment techniques that could increase the density of soils are often the preferable alternatives. The treatment usually increases the in situ SPT-N or CPT-q values, which in turn would increase the resistance of soil against liquefaction. For many public infrastructures in Japan supported by bored piles embedded partly or entirely in sandy soils, reevaluation of design safety against soil liquefaction would be required. In an assessment of possible retrofitting countermeasures for an infrastructure foundation, ground treatment has been considered. In this case study, effect of ground treatment on response of piles in liquefiable soils was investigated with numerical analyses using FLAC. Results provide insights into this ground treatment effect and useful information for consideration in future design or decision making. [ABSTRACT FROM AUTHOR]

This report outlines the observations of an NZSEE team of practitioners and researchers who travelled to the Kumamoto Prefecture of Japan on a reconnaissance visit following the April 2016 earthquakes. The observations presented in this report are focussed on the performance of reinforced concrete (RC) buildings throughout Kumamoto Prefecture. It was found overall that modern RC buildings performed well, with patterns of damage which highlighted a philosophy of designing stiffer buildings with less of an emphasis on ductile behaviour. To explore this important difference in design practice, the Japanese Building Standard Law (BSL) is summarised and compared with standard New Zealand seismic design practices and evaluation methods. [ABSTRACT FROM AUTHOR]

SUMMARY We developed the 550-kV disconnectors that strengthened earthquake proofing by the addition of the damper unit and weight reduction of conductive part based on the damage of the 550-kV disconnectors by the Great East Japan earthquake (March 11, 2011) and inspected the earthquake proofing performance by shake table test. In shake table test, we performed the test by the artificial seismic wave that varied in phase characteristic in addition to the test by resonance method. And, in a high-level earthquake area, we analyzed it about the influence that a phase characteristic of the artificial seismic wave gave to stress to occur in disconnectors. As a result, it is thought that the stress to occur in disconnectors is decided by a primary natural frequency basically because a bending strain to occur to the disconnectors in the time when the resonance frequency ingredient becomes the big acceleration response value grows big. But, on a particular phase condition, it was confirmed that the bending strain to occur in disconnectors might grow big conspicuously. As for this, the possibility is thought about by influence of higher natural frequency doing superposition. [ABSTRACT FROM AUTHOR]

The article discusses the development and status of seismic design for high-rise buildings in Japan. Topics covered include a brief history showing the progression of seismic design of Japan's high-rise buildings, details relating to the wind-resistant design of high-rise buildings in Japan, and the structural technologies used in the high-rise buildings constructed in Japan as of April 2015 including the Toranomon Hills building, the Otemachi Tower, and ARK Hills Sengokuyama Mori Tower.

A simplified pseudo-static limit equilibrium approach is used to analyse a full-scale slope failure that occurred during the 1995 Kobe earthquake. The slope is 28 m high, having a gentle angle of 26·5°, and has a factor of safety as high as 2·43 in the absence of an earthquake. In addition to a factor of safety, the critical failure surface obtained from pseudo-static analysis is compared with that of the actual failure surface. Contradictory to some design codes that use only a horizontal seismic coefficient, this study finds that a rational analysis must take into consideration both horizontal and vertical seismic accelerations. The analysis including vertical acceleration may give a shallower or deeper failure surface than cases where vertical acceleration is ignored. An analysis combining horizontal and upward accelerations results in a deeper failure surface than when only downward or no vertical acceleration is considered. The effects of soil properties on the slope stability are also investigated. The study suggests that for near-fault earthquakes, slopes may be subjected to vertical (upward) seismic coefficient as large as 90% that of horizontal, larger than that specified in existing design codes. [ABSTRACT FROM AUTHOR]

Space structures are generally light and rich in redundancy. These two characteristics caused this assumption for a while that these structures are aseismic. However, some events like Kobe 1995 earthquake, Japan, showed that although the space structures are safer than ordinary structures, but are not aseismic. Alot of research based on the seismic behavior of the space structures are carried out since then [1, 2, 3 and 4], however few of the is lead to practical results. Sadeghi in 2004 have established some formula for assessing the equivalent static earthquake action on the double layer barrel vaults. In the current work, those formulae are considered in the design of six double layer barrel vaults with different rise to span ratios and support conditions. Then the seismic behavior of these double layer barrel vaults are compared with corresponding barrel vaults which are designed without considering the seismic actions. To do this, the finite element package of ANSYS is utilized. The results show that these formulae are practically useful and versatile and application of them on the barrel vaults improves the structures' seismic safety significantly. [ABSTRACT FROM AUTHOR]

The article presents a study on the capacity of beam-to-column connections in high-rise buildings in Japan to resist seismic pressure through the use of E-Defense shaking table test. Field-welded connection and shop-welded connection are the two types of connections adopted for the examination of seismic capacity of buildings. The test results indicate that some field-welded connections fractured from the bottom flange weld boundary due to the failure in the actual field welding where ensuring and inspection performance should have been done well. The shop-welded connections, on the otherhand, are able to endure many cycles of plastic rotation.

The article focuses on the development and application of the core-suspended isolation (CSI) system, the new seismic isolation system. It discusses the concept and function of the CSI system including its conceptual drawings, its mechanics, and implementation. It states that the goal of the development of CSI system is to achieve the highest level of earthquake resistance with a desirable form of architecture. It says that the CSI system is composed of a reinforced concrete core, and also has a double layer inclined rubber bearings. It mentions the first four-level building built with CSI system in Tokyo, Japan. Moreover, the CSI system is applicable to all buildings with different heights without losing its system effectiveness.