Chi-Chi Earthquake Research Articles

Seismic Response of Open Ground Story Reinforced Concrete Buildings, Considering with Soil-Structure Interaction

This study investigates the seismic behavior of open-ground story (OGS) reinforced concrete buildings with soil-structure interaction (SSI) using SAP2000. The study mainly focused on mid-rise (8-storey) and low-rise (4-storey) OGS buildings, incorporating different masonry infill materials such as brick, concrete blocks, and autoclaved aerated concrete (AAC) blocks. Selected ground motions from the Bhuj, El Centro, and Chi-Chi earthquakes were utilized to simulate varying seismic intensities and frequency content. Critical parameters such as top-story displacement and inter-story drift are analyzed to assess the structural safety and serviceability of RC buildings. The results demonstrate that both OGS coupled with SSI and masonry infill type significantly affect the displacement and drift, with mid-rise buildings showing more pronounced impacts. Furthermore, ground motion characteristics are critical in producing different response patterns. The study highlights the importance of considering SSI, infill materials, and ground motion characteristics in the design of OGS buildings to enhance earthquake resilience and reduce seismic damage.

Influence of velocity pulse directivity on seismic response of cross-fault bridges

Pulse-type ground motions have special destructive effects on structures, and directivity is one of the fundamental characteristics of velocity pulses. In this paper, the impact of the velocity pulse directivity of seismic motions on both sides of the fault on the seismic response of fault-crossing bridges was quantified using the original records from the Chi-Chi earthquake in Taiwan. First, an automatic baseline correction method was applied to restore the permanent ground displacement, and the direction corresponding to the strongest pulse energy on both sides of the fault was identified based on continuous wavelet transformation. On this basis, the variability of the peak intensity of ground motions on the hanging wall and footwall in different directions, as well as the differences in pulse characteristics between the strongest pulse component and the two initial horizontal components, were analysed. Finally, a typical 5 × 30 m continuous girder bridge was considered as the research object to reveal the influence of the velocity pulse directivity on the seismic response of key parts on both sides of the fault. The results showed that the variability in the peak ground-motion intensity on the hanging wall of the fault was higher than that on the footwall. The displacement variability was up to 863 %, velocity was 262 %, and acceleration was 124 %. The pulse characteristics of the strongest pulse component were stronger than those of the parallel and vertical fault components, and its acceleration, velocity, and displacement response spectra were larger. The amplification effects of the velocity pulse directivity on the transverse bending moment, longitudinal bending moment, and torque of the pier bottom reached 1.3, 1.1, and 1.6, respectively. However, the amplification effect of the velocity pulse directivity on the relative displacement of the pier top, displacement of the main beam, and displacement of the bearing was more than 1.6 times, which was more significant than the internal force of the pier bottom.

Statistical Analysis of Characteristic Parameters and Probability Distribution of Near-Fault Velocity Pulses—A Case Study on the 1999 Mw 7.6 Chi-Chi Earthquake

Abstract The 1999 Mw 7.6 Chi-Chi earthquake in the Taiwan region generated valuable ground motions, providing an opportunity for studying the characteristic parameters and distribution of near-fault velocity pulses. Using the finite-difference method, we built a source model, simulated the 1999 Mw 7.6 Chi-Chi earthquake ground motions, and obtained synthetic velocity waveforms consistent with the observed waveforms. On this basis, we analyzed the distribution of velocity pulses in the near-fault region and compared it with the pulse probability distribution (PPD) curve of the near-fault velocity pulse. We found that the complex rupture process of the Mw 7.6 Chi-Chi earthquake resulted in velocity pulses still being recorded in Miaoli and Xinzhu. In addition, we analyzed the relationship between pulse period, pulse peak, and fault distance. The pulse peak indicates a clear attenuation trend with increasing fault distance (Rrup) and no statistical relationship between the pulse period and Rrup. More velocity pulses in normal-fault components reveal the reverse fault of the Chi-Chi earthquake. Finally, structures with natural periods within the 1–7 s are more susceptible to resonance from near-fault velocity pulses, and it is necessary to take appropriate seismic measures. This study lays the foundation for a deeper understanding of the ground motion and pulse characteristics caused by earthquakes and contributes to sustained efforts in seismic hazard assessment.

Increase in short-term and long-term stress-associated mental illness after Jiji earthquake in Taiwan: A twenty-year longitudinal population-based cohort study (1999–2019)

BackgroundEarthquakes have caused profound physical and mental health impacts in human history. The Jiji earthquake, which had a magnitude of 7.6 on the Richter scale, occurred on 21 September 1999 in Taiwan. A close follow-up on the mental health status of affected adults after major natural disasters to construct the short-term and long-term risk and prevalence of stress-associated mental illnesses has not been performed by using the nationwide health databases. MethodsThis population-based cohort study included 468,804 adults affected by Jiji earthquake spanning from 2000 to 2019 who were matched at a 1:4 ratio with unaffected individuals based on age and sex (n = 1,875,216). Employing a subdistribution hazard regression analysis, we assessed the incidence of sleep, anxiety, and depressive disorders after Jiji earthquake. Corrections for multiple comparisons were carried out using the Benjamini–Hochberg procedure. ResultsAffected adults experienced an increased incidence of short-term (approximately twice) stress-associated psychiatric disorders. The risk of the post-traumatic stress disorder (PTSD) is significantly higher in the affected adults (40–64 years: aSHR: 92.0; ≥65 years: aSHR: 96.7, p < 0.0001). Middle-aged (aged 40–64 years) male adults presented with significantly more short-term (< one year) and long-term (up to 20 years) stress-related mental illnesses, i.e., insomnia, anxiety, and depressive disorders, than individuals in the control group. ConclusionsAn earthquake has significant short and long-term effects on sleep quality, anxiety, and depressive disorders in affected adults. Optimal short and long-term close monitoring is needed to deploy medical resources and socioeconomic support to relieve mental stress burdens.

An Empirical Spatiotemporal Input Model for Regional Seismic Ground Motions

The development of the economy and technology has attracted greater attention to regional seismic resistance, a key technology for which is the simulation of regional seismic ground motions. This study proposes a simple and highly operable method for the generation of regional seismic ground motions, which includes five steps. First, a seismic ground motion recorded at a seismic station is selected as the original ground motion. The original ground motion is then decomposed into eight sub-signals by wavelet packet transform (WPT). Next, the eight sub-signals are adjusted by the frequency attenuation model. The generated ground motion is then amplitude modulated by the peak ground acceleration (PGA) attenuation model. The frequency attenuation model and the PGA attenuation model are obtained by fitting seismic data from the 1999 Chi-Chi earthquake. Finally, the propagation of the ground motion is considered. The proposed method can provide a time history of seismic ground motions for any point in a region. To investigate the rationality and applicability of the proposed method, the characteristics of the generated seismic ground motions are compared with those of true seismic ground motions. The average error of the PGA of the generated ground motions and the true ground motions is 0.072[Formula: see text][Formula: see text]; thus, the proposed method is suitable for use in small-scale regions. Furthermore, 4-story and 15-story structures are used for structural response analysis. The story drift ratio error between the generated ground and true ground motions is found to be within an acceptable error range. The proposed method provides a new way to generate ground motions for regional seismic investigation.

Mode selection and combination rules of energy-based multimodal pushover method for simply supported beam bridges

The energy-based method (EBM) has been improved as Energy-based Multimodal Pushover Method (EMPM), and is introduced and verified to be effective and convenient for evaluate the seismic performance of the simply supported beam bridges. This paper mainly focuses on the research of vibration mode selection and combination rules of EMPM. Firstly, the longitudinal vibration modes of simply supported beam bridge are categorized into five cases based on mode shapes, and the case definition is emphasized. Then, corresponding to each case, the Pushover loading force are established, and the modal energy, modal displacement, and modal energy capability curve are proposed. After that, the energy-based demand curve and the corresponding energy coefficient for each case is recommended. Finally, only the mode with maximum mode participation factor (MPF) of each case is suggested to take part in the calculation of the seismic response with the proposed mode participation factor combination rule. Case studies of a practice bridge under Chi-Chi and El Centro earthquake waves are used to illustrate the effectiveness and accuracy of the proposed mode selection and combination rules. The study found that the EMPM with the proposed rules could effectively and rapidly assessing the seismic performance of the simply supported beam bridge, resulting in a 70 % decrease in time consumption compared with the Nonlinear Time History Analysis Method (NTHAM). Compared with the CQC and SRSS combination results, the proposed Mode Participation Factor (MPF) combination rule reduced the maximum relative deviation from 39.4 % to 21.09 % between EMPM and NTHAM for peak displacement. Further research showed that the proposed mode selection approach only uses modes with the highest MPF in each case, decreased the number of modes involved more than 50 % and the result accuracy remained almost identical.

Exploring building vibration dynamics in the wake of the Chi-Chi earthquake: implications for natural hazard preparedness

Exploring building vibration dynamics in the wake of the Chi-Chi earthquake: implications for natural hazard preparedness

Experimental research on dynamic responses and hydrodynamic pressures of deep-water bridge piers under seismic and wave actions

Earthquakes and extreme waves pose significant threats to the safety of offshore bridges, particularly in deep-water environments. The temporal sequence of earthquakes and waves and the specific type of earthquake are critical factors that contribute to the potential risks involved. This study aimed to fill a key knowledge gap by conducting a comprehensive series of physical tests on a deep-water bridge pier at a scale factor of 1:30. White noise tests, shaking table tests, wavemaker tests, and combined shaking table and wavemaker tests were carried out. Near-field pulsed earthquakes, far-field long-period earthquakes and earthquake-wave phase differences were examined in the tests. The test results indicate that the presence of water has a noticeable impact on the natural frequency, particularly the 2nd-order frequency, of bridge piers, which may significantly influence the dynamic responses of high bridge piers. The effects of water–pier interactions are further intensified by seismic actions such as the pulsed Loma Prieta and long-period Chi-Chi earthquakes. Moreover, the earthquake-induced hydrodynamic pressures on the upstream and downstream faces of the pier are nearly identical, whereas there is a notable difference when the pressures are caused by incident waves. The magnitude of the combined earthquake and wave responses in relation to the individual responses is influenced by the earthquake–wave phase differences, and the combined responses are less than the sum of the individual responses.

Analysis of the Occurrent Models of Potential Debris-Flow Sources in the Watershed of Ching-Shuei River

The areas around the Ching-Shuei River saw numerous landslides (2004–2017) after the Jiji earthquake, profoundly harming the watershed’s geological environment. The 33 catchment areas in the Ching-Shuei River watershed and five typhoon and rainstorm events, with a total of 165 occurrences and non-occurrences, were analyzed, and the training and validation were categorized into 70% training and 30% validation. A landslide disaster is deemed, for the purposes of this research, to have taken place if SPOT satellite images taken before and after an incident show a Normalized Difference Vegetation Index difference larger than 0.25, a slope of less than 30 degrees, and a number of connected grids greater than 10. The analysis was carried out using the instability index method analysis with Rogers regression analysis and artificial neural network. The accuracy rates of neural network, logit regression, and instability index analyses were, respectively, 93.3%, 80.6%, and 70.9%. The neural network’s area under the curve was 0.933, indicating excellent discrimination ability; that of the logit regression analysis was 0.794, which is considered good; and that of the instability index analysis was 0.635, or fair. This suggests that any of the three models are suitable for the danger assessment of large post-earthquake debris flows. The results of this study also provide a reference and evidence for specific sites’ potential susceptibility to debris flows.

Conditional generation of artificial earthquake waveforms based on adversarial networks

Earthquake waveforms are necessary for simulation, verification, and validation during the development of structural and earthquake engineering. However, due to the fact that the processes of earthquake preparation and generation are extremely complex and the human observations cover a relatively short period compared to large earthquake cycles, recorded earthquake waveforms are often limited and quite imbalanced. Consequently, the generation of artificial earthquake waveforms is meaningful and can produce useful earthquake data. In this study, a new method based on a generative approach is proposed by leveraging machine learning (ML) techniques. The generative models based on generative adversarial network (GAN) and conditional GAN (cGAN) are introduced, and the adversarial training between the generator and the discriminator is utilized to learn how to generate artificial earthquake waveforms. In addition, several criteria are exploited to terminate the adversarial training early in order to prevent modal collapse. Besides, different earthquake datasets and several earthquake features are used to verify the proposed method. The preliminary generation is carried out using the dataset recorded during the Chi-chi earthquake, and the generated samples show similar earthquake features to those extracted from the earthquake dataset. Subsequently, conditional generation is conducted using several sub-datasets recorded in different areas around Taiwan. The results demonstrate that the well-trained model can efficiently generate waveforms according to a pre-specified seismic intensity, with an overall accuracy of up to 90%. Although the model is reliable for Taiwan and in general to restricted subdomain of the probability distribution support, the proposed method shows its ability to produce new samples for a given class, even when the number of generated samples exceeds the number of training samples.

Numerical study of PPVC modular steel constructions (MSCs) with selected connection strategies under varied earthquake scenarios

Modular steel construction (MSC) represents an innovative approach in civil engineering. Yet, the complexities of its structural response to seismic forces are not fully understood, nor is the practicality concerning its connection systems. Traditional analytical models, often linear and elastic, fail to capture the MSC connection's nuanced, non-linear behaviour under seismic stress. This research embarks on a detailed numerical and parametric analysis of three MSC systems, introducing a novel stiffness coupling spring matrix approach to reflect the connection's behaviour more accurately in seismic conditions. The study analysis identifies MSC1 as demonstrating resilience, with intra and internal inter-module connections experiencing displacement up to 0.719 m and 0.685 m, respectively, under a 7.7Mw Chi-Chi earthquake. Conversely, MSC2, under a 6.7Mw Denali earthquake, highlights an urgent need for design optimisation, with connections displacement up to 0.714 m. MSC3 exhibits superior structural integrity and seismic resilience during a 5.3Mw Kocaeli earthquake, achieving a stiffness peak of 5499.1 N/m and registering minimal displacement of 0.184 m and 0.177 m in intra and internal inter-module connections. Further, a sensitivity analysis incorporating ±10% stiffness variations is crucial in seismic resilience. MSC1 and MSC2 display pronounced sensitivity, particularly MSC1's intra-connection with displacement fluctuations up to 0.789 m and a decrease to −8.273 m. This analysis underscores the imperative for enhanced stiffness in MSC3's external inter-module connections to withstand less severe seismic impact while necessitating increased stiffness for MSC1 and MSC's corner inter-module connections. Maintaining consistent stiffness in module-to-foundation connections is essential for models, notably on MSC1 and MSC2, highlighting the intricate challenge of engineering MSC systems for peak seismic performance.

Probability density evolution method based stochastic simulation of near-fault pulse-like ground motions

Quantifying the near-fault effect and establishing a reasonable model of near-fault pulse-like ground motions are particularly important for seismic design of structures in near-fault regions. Given the pronounced randomness associated with earthquakes, this study first proposes a novel stochastic model of near-fault pulse-like ground motions by combining the improved finite-fault model (IFFM) and the multivariate copula-based velocity-pulse model (CVPM). Further, a probability density evolution method (PDEM) based stochastic simulation method is developed, by which the model parameters can be determined in a unified probability space so as to ensure the consistency of two independent models. For illustrative purposes, the observed records collected from the 1999 Chi-Chi earthquake are used to generate new stochastic ground motions set. Two ground motions sets based on classical stochastic simulation methods are also presented for comparison. Numerical results show that the proposed method for stochastic simulation of near-fault pulse-like ground motions is reliable; the statistics of peak ground accelerations and spectral characteristics of simulated samples are consistent with station records. Besides, the proposed method accommodates the noteworthy randomness and proportion consistency of components associated with near-fault pulse-like ground motions, making it suitable for the stochastic response and reliability analysis of seismic structures in near-fault regions. This superiority is challenging to classical stochastic simulation methods that lack reasonable consideration of randomness and correlation associated with model parameters.

Rapid Crisis Response in Resilient Cities: Emergency Response to and Reconnaissance of Earthquake Disasters in Taiwan

The devastating Chichi earthquake in Taiwan in 1999 highlighted the importance of disaster prevention and relief operations. In response to the challenge of extreme events and compound disasters, the National Science and Technology Center for Disaster Reduction (NCDR) contributes to operations at the Central Emergency Operation Center (CEOC) of Taiwan by providing integrated information and timely suggestions, and it delivers a common operational picture to central and local governments through a decision support system. This study was undertaken to explore the emergency response towards the reconnaissance of earthquake disasters in Taiwan to illustrate how resilient cities ensure rapid crisis response with a focus on the NCDR disaster response decision support system. This study examines the decision support system used following the 2016 ML 6.6 Meinong earthquake. The results demonstrate that the first line of relief for the emergency response commander is data-driven decision-making.

Single-pulse-like and double-pulse-like characteristics of near-fault ground motions

An approach is proposed for quantitatively identifying the number of one-cycle pulses of ground motions. The one-cycle pulse signals are derived from the original velocity time series using the low-pass acausal fourth-order Butterworth filter and the zero-point method, and the adaptive cut-off frequency of the filter is determined by the number of extreme points in the extracted pulse signals. Then, according to the relative energy and the comprehensive evaluation index of the extracted pulse signals, ground motions are classified into four classes: nonpulse-like, single-pulse-like, double-pulse-like, and ambiguous. The statistical relationships between pulse characteristics and source parameters, including moment magnitudes, site conditions, and rupture distances, are discussed. In addition, the relationship between the first-arriving-pulse signal and the last-arriving-pulse signal in double-pulse-like ground motion is investigated. Finally, this approach analyzes the distribution of double-pulse-like and single-pulse-like ground motions recorded during the 1999 Chi-Chi earthquake.

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Trauma Clearance Concept of PTSD Help Disaster Victims Avoid from PTSD by volunteering

As we know that trauma means experience that cause intense physical and psychological stress reaction in a big disaster or unfortunate encounter . After disaster, the victims engage in volunteer will get more opportunities to take part in the society and interact with more people. Especially the victims will get a new valuable experience with delight. These experiences will cover-up and clear the trauma experience. Actually through inviting victims involved in volunteer , we can find they re-get the value of life and start a new life career. This article practically shares diverse experiences regarding a lot victims Tzu Chi domestic and international disaster relief activities which include 921 Taiwan Chi-Chi earthquake in 1999, Indian Ocean earthquake and tsunami in 2004, Sichuan (Wenchuan) earthquake of Mainland China in 2008, Morake typhoon of southern Taiwan in 2009, Typhoon Haiyan of Philippine in 2013. We accumulated some examples of victim volunteers how did they quit the invasion of PTSD through the involve of volunteering, Thousands of the victims get a lot of valuable and delightful experiences will invite the other victims to participate the volunteer. This positive action will gradually be spread by victims and set into impetus to the whole disaster area. Except the group type example of disaster victims’ volunteer, there is also the example that a lady who lost husband and two children. How she walked out from the biggest tragedy of her life through volunteering as the interpreter.

Longitudinal seismic displacement analysis of Quasi Seismic Isolation Bridge based on Energy-based Multimodal Pushover Method with and without collision

This paper aims to evaluate the longitudinal seismic displacement of the Quasi Seismic Isolation Bridge (QSIB) based on the Energy-based Multimodal Pushover Method (EMPM), including the pier-beam relative displacement and the collision effect. As a simplified seismic analysis method, the EMPM invokes the concept of energy balance into the modal pushover analysis to assess the nonlinear seismic behavior of Laminated Rubber Bearing (LRB) on bridges. In this method, the energy-based capability curve is obtained by the modal pushover analysis, while the energy-based demand curve is estimated under the ground motion record. The target performance criterion can be derived by intersecting the capability curve with the demand curve. The effect of several key factors in EMPM, such as the mode classification and selection, collision effect, energy coefficient and ductility factor, are studied by a case study of a prototype QSIB under ChiChi and El Centro earthquakes. The results of EMPM are compared with those from Nonlinear Time History Analysis (NTHA), to illustrate the effectiveness and accuracy of this method for evaluating the maximum seismic displacement, and the pier-beam relative displacement with and without collision. Results show that the EMPM is found to be able to estimate the longitudinal seismic displacement of the QSIB with and without collision, and can be used as an effective alternative for rapid assess the seismic performance of bridges. The results also indicate that LRB stiffness for modal analysis should be taken as the stiffness pre- or post-sliding when without or with the gap element. Collision effect enlarges the peak displacement and the maximum bias of EMPM.

Stochastic simulation of earthquake ground motions based on improved finite-fault model

In the seismic reliability analysis of engineering structures, it is often necessary to adopt stochastic ground motions as inputs. However, the current methods used to generate stochastic samples, such as the spectral representation method, the spectral transfer method, the dynamic source method, the physical source method, and the comprehensive method, etc., are not very convincing since they do not contain the complete information of seismic occurrence and propagation. In this study, an improved finite-fault model for stochastic simulation of ground motions is proposed. Compared to existing stochastic finite-fault model, the improved model considers the propagation law of phase spectrum, local site effect, and the impact of wave velocity on the arrival time of seismic waves. Besides, identification and statistics of model parameters are carried out based on ground motion records. Reasonable samples of stochastic ground motions are then obtained. In addition, parameter sensitivity analysis is conducted to determine critical random variables, which reduces the complexity of stochastic simulation. Simulation results are compared with recorded accelerograms from the 1999 Chi-Chi earthquake. It is shown that the improved stochastic finite-fault model is reliable, and the acceleration response spectra of simulated samples are consistent with those of station records collected at various site classes and the design spectra.

Seismic vulnerability analysis on an extra-large highway-railway dual-used arch bridge

The seismic vulnerability analysis is of great important for the design, operation and maintain. The selected extra-large highway and railway dual-used arch bridge contains high geometric nonlinearity and is one of the transportation junctions. Therefore, it is necessary to conduct seismic response analysis. The research results can provide reference for the seismic design and seismic response analysis of target bridge and similar typed bridges. Thus, it has high theoretical value for the design and promotion of similar bridges. This paper starts with a theoretical analysis, using the finite element software LS-DYNA to build a dynamic calculation model of the real bridge and carry out modal and time response analyses. The strength, vulnerable components and stability of the bridge under three-way seismic action at for different earthquake excitation waves (Wenchuan earthquake, Chichi earthquake, Kobe earthquake and El-Centro earthquake) are investigated. Through analysis and comparison of numerical calculations, the seismic performance of the target bridge was comprehensively evaluated.

Two-dimensional seismic simulation based on spectral element method and its application in high-speed railway track-bridge system

Seismic investigations of engineering structures under near-field ground motions typically utilize probabilistic earthquake methods. This study introduces a two-dimensional profile model developed for the spectral element method, taking the Chi-Chi earthquake as an exemplar. By integrating source parameters and station information, we use the SPECFEM2D code for seismic simulations. To demonstrate our method's practicality, we compare the PGA and spectrum of our simulated ground motions with actual seismic records. Further, we calculate the seismic response of the high-speed railway track and bridge system (HSRTBS) under two seismic excitations, assessing peak response errors across the track system, girder, support, and pier. The case study verifies that the simulated ground motions in this paper can be used in the seismic analysis of HSRTBS, providing seismic excitation for the seismic design of the structure and effectively complementing the scenario with limited seismic records. Moreover, the seismic simulation method used in this paper can reduce the number of elements and improve computational efficiency.