Seismic Intensity Parameters Research Articles

New classification of soils by seismic properties for the building code in Uzbekistan

ABSTRACT The accurate assessment of soil conditions is crucial for ensuring the seismic safety of buildings and structures. The existing classification of soils in the building code of Uzbekistan has several drawbacks that affect the accuracy of the input parameters of soil properties, the determination of the seismic intensity of the ground, and the underestimation of external environmental factors that affect seismic intensity. In response to these shortcomings, this paper presents the results of long-term engineering geological, macroseismic, and geophysical studies conducted to assess the influence of ground conditions on seismic intensity parameters. Based on the findings, a new classification of soils according to seismic properties is proposed. The classification system considers the unique characteristics of each soil type and provides a more accurate representation of their seismic properties. The proposed classification system is expected to provide valuable insights for seismic hazard assessment and earthquake-resistant design of structures.

Seismic responses analysis of monopile offshore wind turbines in clays considering the long-term cyclic degradation effect

In marine environment, the monopile offshore wind turbines (MOWTs) are subjected to long-term horizontal cyclic loads caused by wind, waves and currents, which will lead to the stiffness degradation and plastic cumulative deformation of clays. The decrease of clays bearing capacity caused by long-term cyclic degradation effect is a threat to the safe use of MOWTs in earthquake-prone countries (such as some countries in the circum-Pacific seismic belt). A three-dimensional finite element model is established to research the seismic response analysis of MOWT in clays considering the long-term cyclic degradation effect. The cumulative deformation of pile-soil system after long-term cycle are obtained by adopting the stiffness degradation of clays through the USDFLD subroutine. On this basis, the dynamic response analysis of MOWT system under the combined action of seismic and environmental loads is carried out. The influence of long-term horizontal cyclic load number, long-term horizontal cyclic load amplitude, seismic intensity, soil strength, environmental loads and cyclic degradation parameter on the dynamic response of MOWT is analyzed. In the seismic design of MOWTs, the effects of long-term degradation and random wind, waves and other environmental loads should be considered.

Energy-Based Prediction of the Peak and Cumulative Response of a Reinforced Concrete Building with Steel Damper Columns

A steel damper column is an energy-dissipating member that is suitable for reinforced concrete (RC) buildings and multistory housing. To assess the seismic performance of buildings with steel damper columns, the peak displacement of the whole building and the energy dissipation demand of the dampers must be evaluated. This article proposes an energy-based prediction procedure for the peak and cumulative response of an RC frame building with steel damper columns. The proposed procedure considers two energy-related seismic intensity parameters, namely the maximum momentary input energy and the total input energy. The peak displacement is predicted considering the energy balance during a half cycle of the structural response, using the maximum momentary input energy. The energy dissipation demand of the dampers is then predicted considering the energy balance during a whole response cycle using the total input energy. The local responses (e.g., peak drift, maximum plastic rotation of beams, maximum shear strain, and energy dissipation demand of dampers) are predicted using pushover analysis. Numerical analysis results for 8- and 16-story RC buildings show that the proposed prediction method achieves satisfactory accuracy.

A Bayesian Network Model for Rough Estimations of Casualties by Strong Earthquakes in Emergency Mode

<p>Rough estimations in emergency mode are now playing an important role in making key decisions for managing disasters including search and rescue. Most of the studies only paid attention to the earthquakes and ignored the presence of disaster chains and the hazard interactions in earthquakes. Bayesian Networks are ideal tools to explore the causal relationships between events, combine prior knowledge and observed data, and are integrated to solve uncertain problems. In such situations, we present improvements based on a Bayesian Network Model in approaches to estimations of casualties in earthquakes. According to the development of the earthquake disaster chain in literature, the proposed model extracts the key events of earthquakes, considers the hazard interactions, and constructs the Bayesian Networks based on a scenario-based method, to deal with the events in the earthquakes. In the model, lifeline system damages, fires, landslides, and debris flow have been integrated into the networks. The conditional probability tables are encoded by using the collected cases. Validations in the Netica allow the simulation of expected shaking intensity and estimation of the expected casualties by strong earthquakes in emergency mode. Compared to the literature, the method is closer to the fact in the rough estimations, providing important information for our response to earthquakes. Further, rough estimations are started when only seismic intensity or fewer earthquake source parameters are available.</p> <p> </p>

Hilbert-Huang Transform-Based Seismic Intensity Parameters for Performance-Based Design of RC-Framed Structures

This study aims to develop the optimal artificial neural networks (ANNs) capable of estimating the seismic damage of reinforced concrete (RC)-framed structures by considering several seismic intensity parameters based on the Hilbert–Huang Transform (HHT) analysis. The selected architecture of ANN is the multi-layer feedforward perceptron (MFP) network. The values of the HHT-based parameters were calculated for a set of seismic excitations, and a combination of five to twenty parameters was performed to develop input datasets. The output data were the structural damage expressed by the Park and Ang overall damage index (DIPA,global). The potential contribution of nine training algorithms to developing the most effective MFP was also investigated. The results confirm that the evolved MFP networks, utilizing the employed parameters, provide an accurate estimation of the target output of DIPA,global. As a result, the developed MFPs can constitute a reliable computational intelligence approach for determining the seismic damage induced on structures and, thus, a powerful tool for the scientific community for the performance-based design of buildings.

Google Street View as a Teaching Tool for Assessing Earthquake Building Damage

Abstract Damage to infrastructure is one of the most visible impacts that earthquakes have on our daily lives. For this reason, introductory undergraduate courses in seismology and related fields often cover earthquake damage in relation to seismic hazard and risk. This topic is commonly introduced by viewing examples of damage, either through static images or videos. Subsequent coursework frequently involves excursions to the field for in-person site inspections and relating the damage to seismic intensity and other parameters of strong ground motion. These field visits provide students with valuable opportunities to apply classroom knowledge to real-world settings. At the time of writing, the recent COVID-19 pandemic has forced many university classes to cancel field visits, depriving students of these experiences. In this EduQuakes article, I present a lesson plan that attempts to simulate a field visit for assessing earthquake damage in an online setting using the interactive online resource Google Street View to view an area before and after an earthquake. This format facilitates active and exploratory learning and encourages students to build the necessary skills required for further studies in more advanced geoscience courses. I include the lesson plan and a compilation of relevant resources in the supplemental material to this article.

New Ground Motion to Intensity Conversion Equations for China

In this study, we use the strong motion records and seismic intensity data from 11 moderate-to-strong earthquakes in the mainland of China since 2008 to develop new conversion equations between seismic intensity and peak ground motion parameters. Based on the analysis of the distribution of the dataset, the reversible conversion relationships between modified Mercalli intensity (MMI) and peak ground acceleration (PGA), peak ground velocity (PGV), and pseudo-spectral acceleration (PSA) at natural vibration periods of 0.3 s, 1.0 s, 2.0 s, and 3.0 s are obtained by using the orthogonal regression. The influence of moment magnitude, hypocentral distance, and hypocentral depth on the residuals of conversion equations is also explored. To account for and eliminate the trends in the residuals, we introduce a magnitude-distance-depth correction term and obtain the improved relationships. Furthermore, we compare the results of this study with previously published works and analyze the regional dependence of conversion equations. To quantify the regional variations, a regional correction factor for China, suitable for adjustment of global relationships, has also been estimated.

Seismic damage potential described by intensity parameters based on Hilbert-Huang Transform analysis and fundamental frequency of structures

This study aims to present new frequency-related seismic intensity parameters (SIPs) based on the Hilbert-Huang Transform (HHT) analysis. The proposed procedure is utilized for the processing of several seismic accelerograms. Thus, the entire evaluated Hilbert Spectrum (HS) of each considered seismic velocity time-history is investigated first, and then, a delimited area of the same HS around a specific frequency is explored, for the proposition of new SIPs. A first application of the suggested new parameters is to reveal the interrelation between them and the structural damage of a reinforced concrete frame structure. The index of Park and Ang describes the structural damage. The fundamental frequency of the structure is considered as the mentioned specific frequency. Two statistical methods, namely correlation analysis and multiple linear regression analysis, are used to identify the relationship between the considered SIPs and the corresponding structural damage. The results confirm that the new proposed HHT-based parameters are effective descriptors of the seismic damage potential and helpful tools for forecasting the seismic damages on buildings.

A Design Method for Viscous Dampers Connecting Adjacent Structures

This paper investigates the seismic design of fluid viscous dampers connecting adjacent structural systems. A simplified dampers design strategy is proposed, which relies on a linearized reduced order model of the coupled system. A stochastic linearization technique is adopted with the aim of extending the design method to nonlinear viscous dampers. The effectiveness of the design method and of the coupling strategy are assessed via numerical analysis of two adjacent buildings with shear-type behaviour connected by linear or nonlinear viscous dampers and subjected to Gaussian stochastic base acceleration. Different dampers locations are analysed. The accuracy of the reduced order model is assessed, by comparing the relevant response statistics to those provided by a refined multi degree of freedoms model. Finally, a parametric study is performed to assess the effectiveness of dissipative connection for different values of seismic intensity and dampers parameters (i.e., viscous coefficients and velocity exponents).

Research Status of Relationship between Seismic Instrument Intensity and Ground Motion Parameters

Seismic intensity can simply reflect the extent and distribution of earthquake’s impact and damage. A comprehensive and detailed assessment of intensity requires a long time and a lot of manpower and material resources. The ambiguity of the intensity assessment index and the subjectivity of the professionals often result in differences in assessment results. Seismic instrument intensity based on strong earthquake observation records can effectively avoid the above problems, and can quickly and objectively assess the impact and possible damage degree of the surface near the strong earthquake station. This paper summarizes the research progress of seismic instrument intensity and points out the development direction of seismic instrument intensity.

Seismic Vulnerability Analysis of High-Rise Composite Frame Concrete Tube Composite Structure

In order to study the possibility of structural failure of high-rise composite frame-concrete tube structure under different earthquake intensity, seismic vulnerability analysis of the structure is carried out based on IDA principle, and its seismic performance is evaluated. Taking 30-storey high-mixing structure as an example, eight seismic records are selected. After amplitude modulation, non-linear dynamic time history analysis is carried out. PGA, PGV and Sa are selected as seismic intensity parameters, and the maximum inter-storey displacement angle is selected as structural performance index. IDA curve clusters are obtained. Quantile curve method is used to analyze and analyze the results. It is concluded that PGA strength index is more effective. The seismic performance of this kind of structure is evaluated effectively, and then the vulnerability curve and vulnerability matrix are obtained. The analysis results show that the hybrid structure can meet the requirements of “three-level” seismic response and has good seismic performance under 8-degree frequent, basic and rare earthquakes.

Investigation of Stochastic Seismic Response and Index Correlation of an Arch Dam Using Endurance Time Analysis Method

The seismic dynamic response and correlation between various indicators of an arch dam under a series of stochastic earthquake excitation are analysed. Seismic response assessment of a concrete arch dam is conducted through nonlinear endurance time analysis (ETA) of a typical arch dam. The 289 m high Baihetan arch dam in Southwest China (as a case study) is subjected to a set of 10 three‐component endurance time acceleration histories (ETAHs) synthesised on the basis of the design site acceleration response spectrum to increasing peak ground acceleration (PGA). The effects of dam‐reservoir‐foundation interaction, radiation damping of infinite rock foundation, and nonlinearities of dam material and joint contact elements are considered. The indices to failure modes of damage propagation through the dam body and the deformation and joint opening beyond the limit states of the arch dam are identified. Dynamic responses, including deformation, joint opening, and damage distribution, are statistically analysed. The dispersion and correlation of indicators are analysed by employing the coefficient of variation and coefficient of correlation, respectively. The deterministic relationships between contraction joint opening, displacement, and damage volume ratio are obtained by using a multivariate fitting method. The results show that those failure indices have similar exponential trends, and seismic intensity parameters exert a significant influence on seismic response and damage under increasing PGA. The results of correlation and fragility analysis demonstrate that damage volume ratio and the sum of joint opening are consistent, which can provide a strong scientific basis for predicting earthquake damage.

Co-seismic displacement and waveforms of the 2018 Alaska earthquake from high-rate GPS PPP velocity estimation

For earthquake and tsunami early warning and emergency response, the parameters of earthquakes should be determined rapidly and correctly. The precise displacement time series can be obtained from high-rate GPS precise point positioning (PPP) during the earthquake, but require long convergence time. In this paper, the PPP velocity estimation (PPPVE) approach is applied to estimate the velocity waveforms and integrate to displacement waveforms in real-time scenarios. A case study of the 2018 Alaska earthquake is conducted from 1 Hz GPS data. The accuracy of velocity and displacement waveforms for 1 Hz GPS data is analyzed by comparing PPPVE-derived displacements with kinematic PPP solution. The results indicate that PPP and PPPVE are both capable of detecting seismic displacement waveforms with amplitude of 1 cm horizontally, while PPPVE can detect the displacement waveforms with much faster convergence speed. The mean convergence time of PPPVE for north, east and up components are 19, 22 and 31 s, respectively. The derived ground motion parameters estimate a magnitude of Mw = 7.97 ± 0.18, showing a great consistency and agreement with the seismometer magnitude. The preliminary relationship between the seismic intensity and ground motion parameters is established and evaluated for an auxiliary reference. Furthermore, the permanent displacement induced by the earthquake is obtained from real-time PPPVE approach. The benefits of PPPVE approach for GNSS seismology are demonstrated.

Novel Hilbert spectrum-based seismic intensity parameters interrelated with structural damage

The objective of this study is to propose new seismic intensity parameters based on the Hilbert spectrum and to associate them with the seismic damage potential. In recent years the assessment of even more seismic features derived from the seismic acceleration time-histories was associated with the structural damage. For a better insight into the complex seismic acceleration time-history, Hilbert-Huang Transform (HHT) analysis is utilized for its processing, and the Hilbert spectrum is obtained. New proposed seismic intensity parameters based on the Hilbert spectrum are derived. The aim is to achieve a significant estimation of the seismic damage potential on structures from the proposed new intensity parameters confirmed by statistical methods. Park-Ang overall structural damage index is used to describe the postseismic damage status of structures. Thus, a set of recorded seismic accelerograms from all over the word is applied on a reinforced concrete frame structure, and the Park-Ang indices through nonlinear dynamic analysis are provided and considered subsequently as reference numerical values. Conventional seismic parameters, with well-known seismic structural damage interrelation, are evaluated for the same set of excitations. Statistical procedures, namely correlation study and multilinear regression analysis, are applied on the set of the conventional parameters and the set of proposed new parameters separately, to confirm their interrelation with the seismic structural damage. The regression models are used for the evaluation of the structural damage indices for every set of parameters, respectively. The predicted numerical values of the structural damage indices evaluated from the two sets of seismic intensity parameters are inter-compared with the reference values. The numerical results confirm the ability of the proposed Hilbert spectrum based new seismic intensity parameters to approximate the postseismic structural damage with a smaller Standard Error of Estimation than this accomplished of the conventional ones.

WINSTON-BATAN: A SEISMOLOGICAL GROUND-MOTION ANALYSIS CODE

A thorough understanding of an earthquake is very important to provide a descriptive knowledge and in the same time as a prescriptive knowledge for the future development. In particular, it is essential for site selection and structural design development of nuclear reactor and other critical facilities. Ground motion acceleration time history is an important raw information to understand the earthquake and specific geological condition of where the data is recorded. This paper presented the development of strong-motion analysis code, called Winston-BATAN, which able to interpret ground motion time history. The analysis scope of the code including the ground motion parameters such as peak ground acceleration, several additional seismic intensity parameters, strong motion duration, its frequency content via Fast Fourier Transformation and response spectra analysis. Being developed based on an open source Python programming language, Winston-BATAN is flexible for exploratory study to exploit the ground motion time history and easily improve to accommodate additional features. This code able to read input from PEER NGA type file or a simple time and acceleration data type of ground motion. Analysis results of Winston-BATAN shows a very good agreement compare to the results from the standard tools Seismosignal® 2018 Software, in addition flexibility of this code, in particular, to explore the response spectra from the ground motion time history is demonstrated.

Prediction of seismic demand model for pulse-like ground motions using artificial neural networks

A probabilistic seismic demand model that relates ground motion intensity measures (IMs) to the structural demand measures is a useful tool for reliability analysis of structures. It is common to utilize the scalar seismic parameters or a vector of a few seismic parameters to reveal ground motion uncertainty. However, for the qualification of an IM for representing the ground motion uncertainty, a larger vector of greater seismic component is required. This study aims to use more parameters as vector IMs in the demand model to achieve better estimation of the ground motion uncertainty. In this study, three-layer feed forward neural network was used to predict the seismic demand model of the mid-rise reinforced concrete buildings for pulse-like ground motions. The results indicate that due to the complexity of the relationship between seismic response of structures and seismic intensity parameters, using artificial neural networks method is more suitable than numerical methods to show uncertainties.

On the treatment of uncertainty in seismic vulnerability and portfolio risk assessment

SummaryIn a related study developed by the authors, building fragility is represented by intensity‐specific distributions of damage exceedance probability of various damage states. The contribution of the latter has been demonstrated in the context of loss estimation of building portfolios, where it is shown that the proposed concept of conditional fragility functions provides the link between seismic intensity and the uncertainty in damage exceedance probabilities. In the present study, this methodology is extended to the definition of building vulnerability, whereby vulnerability functions are characterized by hazard‐consistent distributions of damage ratio per level of primary seismic intensity parameter—Sa(T1). The latter is further included in a loss assessment framework, in which the impact of variability and spatial correlation of damage ratio in the probabilistic evaluation of seismic loss is accounted for, using test‐bed portfolios of 2, 5, and 8‐story precode reinforced concrete buildings located in the district of Lisbon, Portugal. This methodology is evaluated in comparison with current state‐of‐the‐art methods of vulnerability and loss calculation, highlighting the discrepancies that can arise in loss estimates when the variability and spatial distributions of damage ratio, influenced by ground motion properties other than the considered primary intensity measure, are not taken into account.

Seismic vulnerability assessment of concrete shear wall buildings through fragility analysis

Seismic vulnerability assessment of shear wall buildings can be conducted through non-linear dynamic analysis, which requires detailed analytical modeling, the consideration of different earthquake intensity and structural performance measures. Reinforced concrete shear wall buildings were designed for Vancouver, representing a region of high seismicity in Canada, to assess seismic vulnerability of buildings constructed before and after the enactment of modern seismic design codes. The buildings either had a two-storey or a five-storey height, designed either using the 1965 or the 2010 National Building Code of Canada. Analytical models were generated for non-linear response time history analysis using computer software PRFORM-3D. Fiber-discretized sections were used for flexural response based on constitutive models for concrete and reinforcing steel. The nonlinear behavior in shear was modelled on the basis of sectional non-linear shear response. The shear wall models were validated against experimental data available in the literature before incremental dynamic analysis (IDA) was employed to generate fragility curves. Spectral acceleration at the fundamental period was used as seismic intensity parameter and inter-storey drift of the first floor was selected as the damage indicator. Performance limits considered include Immediate Occupancy, Life Safety and Collapse Prevention. The resulting fragility curves indicate that the life safety intent of the 2010 building designs has been met, while the same requirements could not be satisfied for the 1965 building designs.

A WAY OF SEISMIC MICROZONING BY THE ENGINEERING-GEOLOGICAL METHOD

The authors propose a way of seismic microzoning by the engineering-geological method with the use of a seismic soil conditions model and of a local classification of soils by their seismic properties. Applying the local classification makes it possible to determine the increment of seismic intensity and/or other parameters of seismic effects on a considered surface with the accuracy of the initial data used for the calculation of the seismic properties of considered soils. This is a significant difference from the traditional way of seismic microzoning by the engineering-geological method, according to which the seismic intensity on the surface of the soil massif is assigned with an accuracy of 1 point by the MSK-64 scale in accordance with the soil category by its seismic properties.

Structural damage estimation in mid‐rise reinforced concrete structure based on time–frequency analysis of seismic accelerograms

The aim of this study is to evaluate the intensity and damage potential of seismic accelerograms on structures combining a fuzzy inference system with a set of new seismic intensity parameters. The proposed seismic parameters stem from the energy content of seismic signals. More specifically, a time-window is utilised to define the strong motion duration of seismic excitations and the ensemble empirical mode decomposition is employed for a time–frequency analysis of the selected strong motion area. The maximum inter-storey drift ratio is selected as the seismic structural damage index. Strong interdependence between the proposed seismic intensity parameters and the selected damage index is reported. The membership functions of the fuzzy system are tuned by means of a genetic algorithm. The effectiveness of the proposed fuzzy model is tested on a reinforced concrete frame structure. The methodology should be repeated for every new examined structure and it can be applied to other building types with minor changes. Numerical results indicate total mean square error <0.25 for the maximum inter-storey drift ratio estimation and 91% correct classification rate to seismic categories, revealing the effectiveness of the fuzzy model to estimate numerically the structural damage.