• Earthquakes and Structures
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• v.9 no.5
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• pp.1091-1114
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• 2015

The adequacy of a number of advanced earthquake Intensity Measures (IMs) to predict the structural damage of earthquake resistant 3D R/C buildings is investigated in the present paper. To achieve this purpose three symmetric in plan and three asymmetric 5-storey R/C buildings are analyzed by nonlinear time history analysis using 74 bidirectional earthquake records. The two horizontal accelerograms of each ground motion are applied along the structural axes of the buildings and the structural damage is expressed in terms of the maximum and average interstorey drift as well as the overall structural damage index. For each individual pair of accelerograms the values of the aforementioned seismic damage measures are determined. Then, they are correlated with several strong motion scalar IMs that take into account both earthquake and structural characteristics. The research identified certain IMs which exhibit strong correlation with the seismic damage measures of the studied buildings. However, the degree of correlation between IMs and the seismic damage depends on the damage measure adopted. Furthermore, it is confirmed that the widely used spectral acceleration at the fundamental period of the structure is a relatively good IM for medium rise R/C buildings that possess small structural eccentricity.

• Earthquakes and Structures
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• v.13 no.3
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• pp.221-230
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• 2017

One of the important phases of probabilistic performance-based methodology is establishing appropriate probabilistic seismic demand models (PSDMs). These demand models relate ground motion intensity measures (IMs) to demand measures (DMs). The objective of this paper is selection of the optimal IMs in probabilistic seismic demand analysis (PSDA) of the RC high-rise buildings. In selection process features such as: efficiency, practically, proficiency and sufficiency are considered. RC high-rise buildings with core wall structural system are selected as a case study building class with the three characteristic heights: 20-storey, 30-storey and 40-storey. In order to determine the most optimal IMs, 720 nonlinear time-history analyses are conducted for 60 ground motion records with a wide range of magnitudes and distances to source, and for various soil types, thus taking into account uncertainties during ground motion selection. The non-linear 3D models of the case study buildings are constructed. A detailed regression analysis and statistical processing of results are performed and appropriate PSDMs for the RC high-rise building are derived. Analyzing a large number of results it are adopted conclusions on the optimality of individual ground motion IMs for the RC high-rise building.

• Earthquakes and Structures
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• v.21 no.6
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• pp.563-576
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• 2021

The rocking foundation is effective for reducing structural seismic demand and avoiding overdesign of the foundation. It is crucial to evaluate the performance of rocking foundations because they cause plastic hinging in the soil. In this study, to derive optimized ground motion intensity measures (IMs) for rocking foundations, the efficiency of IMs correlated with engineering demand parameters (EDPs) was estimated through the coefficient determination using a physical modeling database for rocking shallow foundations. Foundation deformations, the structural horizontal drift ratio, and contribution in drift from foundation rotation and sliding were selected as crucial EDPs for the evaluation of rocking foundation systems. Among 15 different IMs, the peak ground velocity exhibited the most efficient parameters correlated with the EDPs, and it was discovered to be an efficient ground motion IM for predicting the seismic performance of rocking foundations. For vector regression, which uses two IMs to present the EDPs, the IMs indicating time features improved the efficiency of the regression curves, but the correlation was poor when these are used independently. Moreover, the ratio of the column-hinging base shear coefficient to the rocking base shear coefficient showed obvious trends for the accurate assessment of the seismic performance of rocking foundation-structure systems.

• Earthquakes and Structures
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• v.8 no.5
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• pp.957-976
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• 2015

Recently, two energy-based response parameters, i.e., the absolute and the relative elastic input energy equivalent velocity, have been receiving a lot of research attention. Several studies, in fact, have demonstrated the potential of these intensity measures in the prediction of the seismic structural response. Although some ground motion prediction equations have been developed for these parameters, they only provide marginal distributions without information about the joint occurrence of the spectral values at different periods. In order to build new prediction models for the two equivalent velocities, a large set of ground motion records is used to calculate the correlation coefficients between the response spectral values corresponding to different periods and components of the ground motion. Then, functional forms adopted in models from the literature are calibrated to fit the obtained data. A new functional form is proposed to improve the predictions of the considered models from the literature. The components of the ground motion considered in this study are the two horizontal ones only. Potential uses of the proposed equations in addition to the prediction of the correlation coefficients of the equivalent velocity spectral values are shown, such as the prediction of derived intensity measures and the development of conditional mean spectra.

• Structural Engineering and Mechanics
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• v.81 no.2
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• pp.219-230
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• 2022

Due to the large number of railway bridges along China's high-speed railway (HSR) lines, which cover a wide area with many lines crossing the seismic zone, the possibility of a HSR train running over a bridge when an earthquake occurs is relatively high. Since the safety performance of the train will be threatened, it is necessary to study the safety of trains running over HSR bridges during earthquakes. However, ground motion (GM) is highly random and selecting the appropriate ground-motion intensity measures (IMs) for train running safety analysis is not trivial. To deal this problem, a model of a coupled train-bridge system under seismic excitation was established and 104 GM samples were selected to evaluate the correlation between 16 different IMs and train running safety over HSR bridges during earthquakes. The results show that spectral velocity (SvT₁) and displacement (SdT₁) at the fundamental period of the structure have good correlation with train running safety for medium-and long-period HSR bridges, and velocity spectrum intensity (VSI) and Housner intensity (HI) have good correlation for a wide range of structural periods. Overall, VSI and HI are the optimal IMs for safety analysis of trains running over HSR bridges during earthquakes. Finally, based on VSI and HI, the IM thresholds of an HSR bridge at different speed were analyzed.

• Steel and Composite Structures
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• v.19 no.3
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• pp.697-711
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• 2015

It is well known the importance of considering hysteretic energy demands for the seismic assessment and design of structures. In such a way that it is necessary to establish new parameters of the earthquake ground motion potential able to predict energy demands in structures. In this paper, several alternative vector-valued ground motion intensity measures (IMs) are used to estimate hysteretic energy demands in steel framed buildings under long duration narrow-band ground motions. The vectors are based on the spectral acceleration at first mode of the structure Sa($T_1$) as first component. As the second component, IMs related to peak, integral and spectral shape parameters are selected. The aim of the study is to provide new parameters or vector-valued ground motion intensities with the capacity of predicting energy demands in structures. It is concluded that spectral-shape-based vector-valued IMs have the best relation with hysteretic energy demands in steel frames subjected to narrow-band earthquake ground motions.

• Nuclear Engineering and Technology
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• v.53 no.12
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• pp.4179-4188
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• 2021

This study identifies efficient earthquake intensity measures (IMs) for seismic performances and fragility evaluations of the reactor containment building (RCB) in the advanced power reactor 1400 (APR1400) nuclear power plant (NPP). The computational model of RCB is constructed using the beam-truss model (BTM) for nonlinear analyses. A total of 90 ground motion records and 20 different IMs are employed for numerical analyses. A series of nonlinear time-history analyses are performed to monitor maximum floor displacements and accelerations of RCB. Then, probabilistic seismic demand models of RCB are developed for each IM. Statistical parameters including coefficient of determination (R²), dispersion (i.e. standard deviation), practicality, and proficiency are calculated to recognize strongly correlated IMs with the seismic performance of the NPP structure. The numerical results show that the optimal IMs are spectral acceleration, spectral velocity, spectral displacement at the fundamental period, acceleration spectrum intensity, effective peak acceleration, peak ground acceleration, A95, and sustained maximum acceleration. Moreover, weakly related IMs to the seismic performance of RCB are peak ground displacement, root-mean-square of displacement, specific energy density, root-mean-square of velocity, peak ground velocity, Housner intensity, velocity spectrum intensity, and sustained maximum velocity. Finally, a set of fragility curves of RCB are developed for optimal IMs.

• Earthquakes and Structures
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• v.15 no.6
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• pp.629-637
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• 2018

In recent years, selection of strong ground motion records by means of intensity measures representing the spectral shape of the earthquake excitation has been studied by many researchers. These studies indicate the adequacy of this record selection approach in reduction of the scattering of seismic responses. In present study, this method has been studied more in depth to reveal the sufficiency of the spectral shape in predicting structural seismic responses such as the plastic deformation and the dissipated hysteresis energy which are associated with cumulative properties of the selected records. For this purpose, after selecting the records based on the spectral shape, the correlation of some seismic responses and strong ground motion duration of earthquake records are explored. Findings indicate strong correlation of some structural responses with the significant duration of the records. This fact implies that the spectral shape could not reflect all characteristics of the strong ground motion and emphasizes the importance of additional criteria along with the spectral shape in the record selection.

• Journal of the Earthquake Engineering Society of Korea
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• v.7 no.6
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• pp.35-47
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• 2003

Seismic ground motion can vary significantly over distances comparable to the length of a majority of highway bridges on multiple supports. This paper presents results of fragility analysis of two actual highway bridges under ground motion with spatial variation. Ground motion time histories are artificially generated with different amplitudes, phases, as well as frequency contents at different support locations. Monte Carlo simulation is performed to study dynamic responses of the bridges under these ground motions. The effect of spatial variation on the seismic response is systematically examined and the resulting fragility curves are compared with those under identical support ground motion. This study shows that ductility demands for the bridge columns can be underestimated if the bridge is analyzed using identical support ground motions rather than differential support ground motions. Fragility curves are developed as functions of different measures of ground motion intensity including peak ground acceleration(PGA), peak ground velocity(PGV), spectral acceleration(SA), spectral velocity(SV) and spectral intensity(SI). This study represents a first attempt to develop fragility curves under spatially varying ground motion and provides information useful for improvement of the current seismic design codes so as to account for the effects of spatial variation in the seismic design of long-span bridges.

• Structural Engineering and Mechanics
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• v.86 no.1
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• pp.85-92
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• 2023

This article examines the seismic vulnerability of soil nail wall structures. Detailed information regarding finite element modeling has been provided. The fragility function evaluates the relationship between ground motion intensities and the probability of surpassing a specific level of damage. The use of incremental dynamic analysis (IDA) has been applied to the soil nail wall against low to severe ground motions. In the nonlinear dynamic analysis of the soil nail wall, a set of twenty seismic ground motions with varying PGA ranges are used. The numerical results demonstrate that the soil-nailed wall reaction is extremely sensitive to earthquake ground vibrations under different intensity measures (IM). In addition, the analytical fragility curve is provided for various intensity values.