Duration Of Ground Motion Research Articles

Effects of Ground Motion Duration on the Seismic Performance of a Two-Storey Balloon-Type CLT Building

The effects of long duration ground motions on the seismic performance of a newly constructed two-storey balloon-type cross-laminated timber (CLT) building located in Vancouver, Canada, was studied. A three-dimensional numerical model of the building was developed in OpenSees. The connection and shear wall models were validated with test data. Twenty-four pairs of long and short duration records with approximately the same amplitude, frequency content, and rate of energy build-up were used for nonlinear dynamic analyses. Fragility curves were developed based on the results of incremental dynamic analysis to assess the building’s collapse capacity. At design intensity level, ground motion duration was shown not to be a critical factor as the difference in inter-storey drift ratio between the two sets of records was negligible. However, due to the larger number of inelastic cycles, the long duration motions increased the median probability of collapse by 9% when compared with the short duration motions. Further research is required to evaluate the duration effects on taller and platform-type CLT buildings.

Combining Discrete Wavelet Transform and Strong Ground Motion Duration to Reduce Computational Costs in Dynamic Analysis of Structures

The dynamic time history analysis is the most accurate method for calculating the structure response relative to the vibrating load. The use of this method is time-consuming due to the long-duration earthquakes and is generally less commonly used. Wavelet trans-forms are one of the new methods for filtering waves. The duration of a strong ground motion is actually a concept that can be used to turn an earthquake with a long time into an earthquake with a shorter time. In this paper, two concepts of filtration using wavelet transform and the use of a duration of strong ground motion are used for the time history analysis of structures. For this purpose, the acceleration of the earthquake in 5 states was filtered by wavelet transform. In each stage, the high and low frequencies are separated, and the number of earthquake acceleration points is half-past. Then the beginning and the end of the main earthquake and the approximate waves obtained from the wavelet transform are removed using the concept of the duration of the strong ground motion. Finally, two two-dimensional and three-dimensional structures are analyzed using the main earthquake and the waves obtained by combining the two concepts of wavelet transform and the duration of strong ground motion. The results show that by reducing the number of acceleration points of the main earthquake record to more than 95%, the dynamic response error is less than 8%.

Use of Artificial Neural Networks to predict strong ground motion duration of interplate and inslab mexican Earthquakes for soft and firm soils

Artificial neural network models are developed to predict strong ground motion duration of sub- duction events for soft and firm soils. To train the artificial neural network a database with a total of 3153 seismic records with two horizontal components for interplate and inslab earthquakes is employed. The principal component method is used to carry out a dimensionality reduction of the input parameters to develop the artificial neural network models. The predicted values of the strong ground motion duration trained by the artificial neural network models are compared with those estimated with empirical expressions. In general, the strong ground motion duration predicted with the artificial neural networks follows the same tendency of that calculated with the empirical equa- tions, although in some cases, the strong ground motion duration predicted by using the artificial neural network models presents sudden changes in its behavior. For this reason, it is recommended to carry out several verifications of the trained artificial neural network models before using them for further engineering applications, for example the simulation of synthetic records or the evaluation of seismic damage indices.

Strong Motion Models for Duration and Arias Intensity for Strong Motion Records in Chile

Chile presents a high seismicity and very particular characteristics due to its subductive environment and high convergence rate of the interacting plates. In this paper, ground motion models (GMM) for Arias Intensity and strong ground motion duration are developed based on recently compiled Chilean earthquakes records. The Chilean derived GMM are later compared with global and subduction models. For the duration case, two definitions are considered: significant duration and bracketed duration. Care is taken to consider newly define rupture areas for the major earthquake in the catalog, which allows to redefine the distances to be used in the analysis. The strong motion records are processed using robust techniques and standardized procedures. The model parameters are selected using a Bayesian updating method. This allows to estimate the parameters as well as their corresponding uncertainties recognizing the variability of the coefficients and of the selected model. The derived ground motion predictive model associated is validated through a residual analysis and probability distributions, obtained from the adjustment method. Additionally, for the bracketed duration analysis, a classification method based on Support Vector Machine (SVM) is used, with the aim to incorporate the records with duration of zero seconds. The comparison of the resultant model with the existing ones allows to confirm the differences that the tectonic Chilean environment produces, characterized mainly by a high relative convergence rate between plates and interplate thrust earthquakes with high magnitudes.

Influence of ground motion duration on seismic performance of RC frame isolated by high damping rubber bearings

The high damping rubber bearing (HDRB) is an advanced seismic isolation component currently used in building structures with sound energy dissipation capacity. This study examines the effects of ground motion duration on the seismic performance of reinforced concrete frame isolated by HDRBs. The effect of ground motion duration is isolated from other effects due to ground motion amplitude and acceleration spectral shape by using 44 pairs of short-duration and long-duration spectrally equivalent ground motions. Nonlinear time-history analyses are conducted on a base-isolated building using HDRBs. The numerical analyses considered the calibrated parameters of the HDRB model based on experimental data. The stiffness degradation of the HDRBs due to Mullins’ effect under cyclic loading is accounted into the numerical model. The influence of ground motion duration is evaluated by comparing the seismic responses of the isolator components and the superstructure. The results indicate that the ground motion duration generates a significant influence on seismic responses. The influence varies as the ground motion intensity changes. The stiffness degradation of the HDRB becomes evident with the increase of the earthquake intensity, and the effect of such degradation on the structural responses is more significant when under long-duration ground motions.

Influence of ground motion characteristics (velocity pulse and duration) on the pile responses in liquefiable soil deposits

In this paper, three-dimensional finite-element analyses are conducted to study the effects of ground-motion duration and the presence of velocity pulse on the pile responses in liquefiable soils. The soil-pile system consisting of liquefiable granular deposits and rigid piles is modeled in OpenSeesPL. Four suites of ground motions, namely one pulse-like, one non-pulse-like, one long-duration, and one short-duration suite, are appropriately selected from worldwide earthquake events. Dynamic analyses are conducted for the soil-pile system under the excitations of four selected ground-motion suites. It is indicated that the pulse-containing ground motions bring in greater pile-bearing bending moments and shear forces as compared to the non-pulse-like suite, with the increase ratios of the mean peak bending-moments and shear-forces up to 27% and 34%, respectively. Furthermore, as compared to the short-duration suite, using the long-duration ground motions yields similar pile responses (bending moments and shear forces) but a substantial increase of the pile's permanent lateral displacements. The mean lateral displacements at pile head are 0.62 m and 0.17 m under the excitations of the long- and short-duration suites, respectively. In addition, correlation analyses indicate that peak ground velocity and Arias intensity can be regarded as effective intensity measures to evaluate the pile response (e.g., bending moment) and lateral displacement for a pile-reinforced liquefiable ground system. The results could provide useful insights for applying the pile-pinning approach in areas where pulse-like or long-duration ground motions are of the main concern.

Unravelling a 2300 year long sedimentary record of megathrust and intraslab earthquakes in proglacial Skilak Lake, south‐central Alaska

AbstractSeismic hazards in subduction settings typically arise from megathrust, intraslab and crustal earthquake sources. Despite the frequent occurrence of intraslab earthquakes in subduction zones and their potential threat to communities, their long‐term recurrence behaviour is barely studied. Sedimentary sequences in lakes may register ground shaking from different seismic sources. This study investigates two long sediment cores (13 m and 16 m) from Skilak Lake, a proglacial lake in south‐central Alaska, to evaluate whether different seismic sources leave a distinct imprint. The sedimentary record shows a continuously varved sediment sequence, occasionally interrupted by turbidites, slump deposits and tephra beds. Turbidites and slump deposits were objectively identified using a statistical outlier analysis on varve thickness. The earthquake origin of these deposits was ascertained by resemblance with deposits induced by instrumentally recorded earthquakes (for example, 1964 ce Mw 9.2 megathrust and 1954 ce Mw 6.4 intraslab earthquakes) and correlation with multiple coeval landslide deposits on sub‐bottom profiles. The Skilak Lake record chronicles 19 earthquakes with moderate to very high confidence level in the past 1350 years. The sedimentary evidence of instrumentally‐recorded intraslab and megathrust earthquakes within the past 70 years demonstrates that not only megathrust earthquakes, but also past intraslab events are recorded. Although reported seismic intensities at Skilak Lake are comparable for the 1964 ce megathrust and the 1954 ce intraslab earthquakes, the long duration and low frequency content of seismic ground motion during megathrust earthquakes facilitate the triggering of multiple, voluminous landslides and the generation of megaturbidites. In contrast, the shorter duration and higher frequency source spectrum of intraslab earthquakes may only induce surficial slope remobilization and the generation of thinner turbidites. This study demonstrates that the sedimentary record of Skilak Lake has the potential to decipher multiple seismic sources, which opens possibilities for a comprehensive seismic hazard analysis for south‐central Alaska.

Seismic fragility analysis of CFT frames with buckling-restrained braces and steel braces under long- and short-duration ground motions

This study presents the seismic behaviour and the effect of ground motion duration on the probabilistic seismic fragility for the concrete-filled steel tube (CFT) frames with buckling-restrained braces (BRB-CFTF) and conventional steel braces (SB-CFTF). The nine-storey BRB-CFTF and SB-CFTF prototype structures were designed based on the performance-based plastic design method. One scaled single-storey single-bay BRB-CFTF and one buckling-restrained brace (BRB) extracted from the prototype structure were cyclically tested and analyzed. Finite element (FE) models of the two braced frame structures were developed and validated by available test results. The results obtained from nonlinear dynamic analyses showed that the designed two structures achieved expected performance objectives in terms of the inter-storey drift and member energy-dissipating demand. The selection of engineering demand parameter (EDP) quantifying structural response and intensity measure (IM) representing ground motion hazard level was performed to determine optimal indicators for identifying duration effect prior to establishment of fragility curves. The results indicated that the overall damage index (ODI) as the EDP can clearly distinguish the influence of duration effect on structural cumulative damage. The optimal IM relative to ODI was believed to be the combined duration- and spectrum-related INP-D, because of desirable balance among the efficiency, sufficiency and scaling robustness. The BRB-CFTF and SB-CFTF structures were more vulnerable to all limit states under long-duration ground motions than those under short-duration ones at the same seismic hazard level, and the probability of exceedance for a given INP-D of the SB-CFTF was generally larger than that of the BRB-CFTF. The influence of ground motion duration on the cumulative damage for the BRB-CFTF and SB-CFTF structures is suggested to be considered in structural seismic design and analysis.

A Deep Learning-Based Integration Method for Hybrid Seismic Analysis of Building Structures: Numerical Validation

A hybrid seismic analysis computing the full nonlinear response of building structures is proposed and validated in this paper. Recurrent neural networks are trained to predict the nonlinear hysteretic response of isolation devices with deformation- and velocity-dependent behavior. Then, they are implemented in an explicit time integration method for time history analysis. A comprehensive framework is proposed to develop and test deep learning models considering the data framing, the network architecture, and the learning behavior. Hybrid seismic analyses of three base-isolated building models subjected to four ground motions with different properties were performed in order to check their efficiency. The small relative errors of computed results to those of the conventional analysis successfully validate the accuracy of the proposed analysis. Its computation time depends mainly on the ground motion duration and is considered negligible. The development of the machine learning model is more time-consuming but nonrepetitive since it can be saved and reused to analyze any new structure containing the same target components. The proposed hybrid seismic analysis overcomes the shortcomings of usual applications of machine learning in structural response prediction problems being limited to specific response quantity(s) of the same structure(s) used at the training process. By taking advantage of both mechanics-based and data-driven methods, results reveal that hybrid analysis is an efficient tool for building-response simulation.

Determining the Optimal Scalar Intensity Measure of Floor Communication Towers

Various structural types and ground motion characteristics lead to distinct intensity measures of structural seismic performance. For the lattice high-rise steel structure of communication towers, determining the intensity measures to adjust ground motion is critical. Additionally, a crucial problem is whether the ground motion intensity parameters of pulse-like ground motion and ordinary ground motion are consistent. In this study, a standard floor four-leg angle steeled communication tower was considered the study object, and 50 pulse-like ground motions and 50 ordinary ground motions were identified to form a pulse-like ground motion set and ordinary ground motion set, respectively. For comparative analyses, 15 ground motion parameters, including amplitude, spectrum, duration, and energy parameters, were selected. The results revealed that for the lattice towers, such as communication tower, under the action of pulse-like ground motion or ordinary ground motion, efficiency, practicability, and sufficiency should be considered. Furthermore, the most suitable intensity measure was the spectral acceleration corresponding to the natural period of the tower. This study provides a basis for selecting the ground motion for dynamic time history analysis of the lattice steel tower.

On the seismic performance evaluation of dam-foundation-reservoir system for the effect of frequency content and foundation flexibility

The present paper investigates the effect of earthquake frequency content and foundation flexibility on the performance of the Koyna dam-foundation-reservoir system. Ground motions that match the conditional mean spectrum (CMS) are adopted for the seismic analysis. The concrete damaged plasticity model is used to represent the dam's nonlinear behavior; however, the foundation is assumed to be linear elastic. To study the foundation flexibility effect on the seismic performance of the dam, three different cases which comprise different elastic modulus of the foundation are considered. The damage indices, based on the crack length and dissipation energy, are evaluated for the performance assessment of the dam-foundation-reservoir system. The ground motion parameters such as predominant period, mean period, and effective ground period are chosen in order to explore the earthquake frequency content effect on the performance of dam-foundation-reservoir system. Results indicate that foundation flexibility has a significant effect on the dam. Further, the frequency content has a substantial impact on the dam's seismic response compared to the intensity and duration of ground motion. It can be concluded that the mean period is a good indicator of the earthquake frequency content and has a strong correlation with the damage parameters.

A passive shape-memory-alloy–rubber-bearing seismic isolator for offshore platforms

A passive shape-memory-alloy–rubber-bearing isolator has been developed for seismic protection of offshore jacket platforms. Mathematical modelling of an offshore jacket platform subjected to earthquake ground motions was undertaken, after which a systematic study of the key parameters of the isolator was undertaken to investigate its efficiency and to improve its performance. Dynamic time history analyses were carried out for both isolated and non-isolated jacket platforms using scaled ground motions. These clearly indicated the effectiveness of the isolator in controlling the overall responses of the jacket platform. It was better at mitigating structural displacement than structural acceleration, and its performance was dependent on the duration of ground motion.

Effects of long duration earthquakes on the interaction of inertial and liquefaction-induced kinematic demands on pile-supported wharves

Nonlinear dynamic analyses were performed to evaluate the effects of ground motion duration on the dynamic response of a pile-supported wharf subjected to liquefaction-induced lateral ground deformations. The numerical model was first calibrated using recorded data from a well-instrumented centrifuge test, after which incremental dynamic analyses were conducted using a suite of spectrally matched motions with different durations. The nonlinear dynamic analyses were performed to evaluated three loading scenarios: combined effects of inertial loads from the wharf deck and kinematic loads from ground deformations, deck inertial loads only in the absence of liquefaction (with minimal kinematic loads), and kinematic loads only in the absence of deck mass inertia. The analysis results were evaluated to provide insights on the relative contribution of inertial and kinematic demands on the response of the wharf with respect to motion duration. It was found that the contribution of peak inertial and peak kinematic loads to the maximum total demand increases only slightly with motion duration and intensity. The response of the wharf was found to be primarily governed by kinematic demands when subjected to long-duration motions for the type of foundation analyzed in this study which is commonly used in the port industry.

Optimum design of tuned mass damper with pinched hysteresis under nonstationary stochastic seismic ground motion

The optimum design of a recent tuned mass damper with pinched hysteresis (TMD-PH) for seismic protection of structures is here investigated. The considered device consists of mixed NiTiNOL-steel wire ropes undergoing combined tension-flexure cycles. Previous studies demonstrated that concurrent interwire friction and phase transformation of the shape memory material exhibited by these composite wire ropes generate a peculiar pinched hysteretic behavior, which can be well described by means of a modified Bouc–Wen model. A stochastic-based optimum design methodology is here proposed for such TMD-PH, which is tailored to determine the best design parameters for the seismic protection of general structural systems. The seismic ground motion is modeled as a filtered nonstationary random process whereas the inherent pinched hysteresis of the device is dealt with via the stochastic linearization technique. The expressions of the linearization coefficients are obtained ad hoc and the optimum design of the TMD-PH is formulated as box-constrained single-objective optimization problem. Three objective function formulations are considered to reflect alternative design philosophies, namely, displacement-, acceleration- and energy-based design strategies. Unlike most literature studies addressing the optimum design of vibration absorbers via finite difference-based numerical schemes or non-gradient-based metaheuristic methods, the search for the optimal parameters of the TMD-PH is here performed by means of an iterative semi-analytical gradient-based numerical technique in which the derivatives for the covariance matrix of the system response are calculated analytically. A comprehensive numerical campaign is finally presented. First, a parametric study is carried out to evaluate the effects of the protected system characteristics and those of the seismic ground motion duration on the optimal parameters and performance of the device under consideration. The performance of the TMD-PH optimized according to the proposed methodology is also assessed in the context of a practical case study which makes use of synthetic and natural seismic ground motion records.

A study into the effect of different ground motion durations on the seismic pounding force by considering soil–structure interaction

A study into the effect of different ground motion durations on the seismic pounding force by considering soil–structure interaction

The 2017 Ischia Earthquake (Southern Italy): Source Mechanism and Rupture Model From the Inversion of a Near-Source Strong Motion Record

With the aim to investigate the rupture complexity and the radiated wave field of the 2017, Mw 3.9, Ischia earthquake, south-west of Naples (Italy), we used finite-fault modeling to invert the near-source (< 1-km epicentral distance) horizontal-component velocity records of the accelerometric station (IOCA) and searched for the best-fit kinematic rupture parameters. This analysis showed that the rupture nucleated at about 600 m west of IOCA and 1.1-km depth, along a 1 km, NW-SE striking fault (i.e., thrust with right-lateral component), with a rupture velocity of about 0.7 km/s. The retrieved rupture model coupled with multipath reverberations effects related to a thin, low-velocity near-surface volcanic sedimentary layer, well explains the observed long ground motion duration and the large amplitudes recorded all over the island. Finally, the apparent source time function (STF), obtained from inverse modeling using a theoretical Green’ function (GF), is validated by implementing an empirical GF (EGF) analysis.

Ground motion of the Ms7.0 Jiuzhaigou earthquake

Abstract Eighty-eight free-field strong ground motion observation datasets obtained by the National Strong Motion Observation Network System of China for the Jiuzhaigou Ms7.0 earthquake were used to study the characteristics of the strong ground motion and the site response. In this study, we calculated the VS30 of the near field station and compared the observed values of the horizontal peak acceleration and peak velocity with the CB2014 ground motion prediction models developed by Campbell et al. (2014). The results indicate that the observed values of the horizontal peak acceleration and peak velocity of the Jiuzhaigou earthquake are both smaller than the predicted values obtained from the ground motion prediction equations. By regressing the spatial variation curves of the D SR (5–95%) and D SR (5–75%) ground motion durations, and comparing them with Bommer’s (2009) ground motion duration prediction curve, it was found that the duration of the Jiuzhaigou earthquake was greater than that obtained from the global empirical prediction equation. The scope of the source duration corresponding to the D SR (5–75%) duration is 2.76–4.28 s, and the scope of the source duration corresponding to the D SR (5–95%) duration is 8.88–10.36 s, which are close to the peak time and completion time of the seismic moment release during the source rupture process. The linear elastic acceleration response spectra of 11 stations within 100 km of the fault were calculated for comparison with the design spectrum. It was concluded that the range of the predominant period of the response spectrum was 0.05–0.26 s, which is less than the natural vibration period of the local multistory building. However, the response spectrum value recorded by station 51JZZ is greater than the design spectrum of the 8° rare earthquake and the observation values of the nearby strong ground motion stations. Through analysis of the H/V spectrum ratio and the case of station 51JZZ, which is closest to the epicenter, this phenomenon was concluded to be related to the magnification effect of the near-surface soil layer and the nonlinear response of the site under the action of strong earthquakes.

An Analytical Method for Elastic Seismic Response of Structures Considering the Effect of Ground Motion Duration

The response to earthquake ground motion is composed of three basic elements, namely, amplitude, frequency, and duration. The seismic response of a structure is controlled by the particular combination of these three elements. The seismic response spectra reflect the earthquake ground motion’s frequency-domain features and provide the maximum response amplitude of a single-degree-of-freedom system to a given earthquake ground motion but do not consider the duration factor. However, the analysis of post-earthquake damage shows that the seismic response duration has a strong impact on the damage to structures. Therefore, it is necessary to develop a simple and practical analytical method to account for the seismic response duration. The present study was conducted based on the response spectra theory. We introduce an analytical method of elastic seismic response, which considers its duration by adding the time-domain dimension of earthquakes. The time-domain spectral matrix is used to solve the time-dependent seismic response through the vibration mode decomposition method. The time-domain vibration mode decomposition reaction spectrum not only takes into account the maximum seismic reaction of each vibration mode but also considers the seismic reaction of different vibration modes occurring at the same time, at each moment. The dynamic time duration of the structure’s seismic reaction is quantified by the time-domain seismic reaction spectrum to obtain a more accurate analysis method for the seismic reaction of the structure.

Probabilistic Seismic Hazard Analysis Based on Arias Intensity in the North–South Seismic Belt of China

ABSTRACT Arias intensity (IA), as an important seismic parameter, which contains the information of amplitude, frequencies, and duration of ground motion, plays a crucial role in characterizing seismic hazard such as earthquake-induced landslides. In this article, we conducted probabilistic seismic hazard analysis (PSHA) based on IA in China’s north–south seismic belt. We adopted the seismic sources and seismicity parameters used in the fifth generation of the Seismic Ground Motion Parameter Zoning Map of China, and two ground-motion model of IA. The results show that the values of IA are greater than 0.11 m/s in most regions of the north–south seismic belt. The provincial capital cities and most prefecture-level cities in the seismic zone are located in the region with IA-values greater than 0.32 m/s. The values of IA are above 0.54 m/s in the region around the main fault zone. This means that the north–south seismic belt is prone to extremely high-seismic hazard, particularly earthquake-induced landslides. Therefore, it is important to strengthen the evaluation and prevention of earthquake-induced landslides in this area. As we have found significant differences in the values of IA calculated from different ground-motion model, it is necessary to study the ground-motion model of IA for the western geological environment of China. In addition, the PSHA based on IA gives more consideration to the influence of large earthquakes than that based on peak ground acceleration. Therefore, IA plays an important role in seismic design of major engineering projects. The results of this article are of great scientific significance for understanding the seismic hazard of the north–south seismic belt.

Hazard-consistent seismic losses and collapse capacities for light-frame wood buildings in California and Cascadia

We evaluate the seismic performance of modern seismically designed wood light-frame (WLF) buildings, considering regional seismic hazard characteristics that influence ground motion duration and frequency content and, thus, seismic risk. Results show that WLF building response correlates strongly with ground motion spectral shape but weakly with duration. Due to the flatter spectral shape of ground motions from subduction events, WLF buildings at sites affected by these earthquakes may experience double the economic losses for a given intensity of shaking, and collapse capacities may be reduced by up to 50%, compared to those at sites affected by crustal earthquakes. These differences could motivate significant increases in design values at sites affected by subduction earthquakes to achieve the uniform risk targets of the American Society of Civil Engineers (ASCE) 7 standard.