• Geomechanics and Engineering
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• v.31 no.3
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• pp.319-328
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• 2022

Ensuring the integrity of a country's infrastructure is necessary to protect surrounding communities in case of disaster. Embankment dam systems across the US are an essential component of infrastructure, referred to as lifeline structures. Embankment dams are crucial to the survival of life and if these structures were to fail, it is imperative that states be prepared. Southern California is particularly concerned with the stability of embankment dams due to the frequent seismic activity that occurs in the state. The purpose of this study was to create a numerical model of an existing embankment dam simulated under seismic loads using previously recorded data. The embankment dam that was studied in Los Angeles, California was outfitted with accelerometers provided by the California Strong Motion Instrumentation Program that have recorded strong motion data for decades and was processed by the Center for Engineering Strong Motion Data to be used in future engineering applications. The accelerometer data was then used to verify the numerical model that was created using finite element modeling software RS2. The results from this study showed Puddingstone Dam's simulated response was consistent with that experienced during previous earthquakes and therefore validated the predicted behavior from the numerical model. The study also identified areas of weakness and instability on the dam that posed the greatest risk for its failure. Following this study, the numerical model can now be used to predict the dam's response to future earthquakes, develop plans for its remediation, and for emergency response in case of disaster.

• Earthquakes and Structures
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• v.9 no.4
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• pp.875-891
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• 2015

Earthquake can occur anywhere in the world and it is essential to design important members in special structures based on maximum possible forces that can be produced in them under severe earthquake. In addition, since the earthquake is an accidental phenomena and there are no similar earthquakes, therefore the possibility of strong earthquakes should be taken into account in earthquake-resistant design of important structures. Based on this viewpoint, finding the critical acceleration which maximizes internal forces is an essential factor in structural design. This paper proposes critical excitation method to compute the critical acceleration in design of important members in special structures. These critical accelerations are computed so that the columns' internal shear force at the base of the structure at each time step is maximized under constraints on ground motion. Among computed critical accelerations (of each time step), the one which produces maximum internal shear force is selected. A numerical example presents to show the efficiency of critical excitation method in determining the maximum internal shear force and base moment under variety of constraints. The results show that these method can be used to compute the resonant earthquake which have large enough effective duration of earthquake strong motion (between 12.86 sec to 13.38 sec) and produce the internal shear force and base moment for specific column greater than the same value for selected earthquakes in constructing the critical excitation (for different cases about 2.78 to 1.29 times the San Fernando earthquake). Therefore, a group of them can be utilized in developing the response spectrum for design of special structures.

• Earthquakes and Structures
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• v.3 no.3_4
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• pp.365-381
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• 2012

Recent earthquakes have damaged some bridges located on the Pacific Coast of Mexico; these bridges have been retrofitted or rebuilt. Based on the fact that the Pacific Coast is a highly active seismic zone where most of the strong earthquakes in the country occur, one fertile and important area of research is the study of the vulnerability of both new and existent bridges located in this area that can be subjected to strong earthquakes. This work is focused on estimating the contribution of some parameters identified to have major influence on the seismic vulnerability of reinforced concrete bridges. Ten models of typical reinforced concrete (RC) bridges, and two existing bridges located close to the Pacific Coast of Mexico are considered. The group of structures selected for the study is based on two span bridges, two pier heights and two substructure types. The bridges were designed according to recent codes in Mexico. For the vulnerability study, the capacity of the structure was evaluated based on the FEMA recommendations. On the other hand, the demand was evaluated using a group of more than one hundred accelerograms recorded close to the subduction zone of Mexico. The results show that the two existent bridges analyzed show similar trends of behavior of the group of bridge models studied. In spite of the contribution that traditional variables (height and substructure type) had to the bridge seismic response, the bridge length was also found to be one of the parameters that most contributed to the seismic vulnerability of these RC medium-length bridges.

• Journal of the Korean Society of Hazard Mitigation
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• v.8 no.6
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• pp.73-79
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• 2008

Economic growth, industrialization and urbanization have made society more vulnerable than ever to seismic hazard in Korea. Although Korea has not experienced severe damage due to earthquakes during the last few decades, there is little doubt of the potential for large earthquakes in Korea as documented in the historical literature. As we see no immediate promise of short-term earthquake prediction with current science and technology, earthquake early warning systems attract more and more attention as a practical measure to mitigate damage from earthquakes. Earthquake early warning systems provide a few seconds to tens of seconds of warning time before the onset of strong ground shaking. To achieve rapid earthquake location, we propose to take full advantage of information from existing seismic networks; by using P wave arrival times at two nearest stations from the earthquake hypocenter and also information that P waves have not yet arrived at other stations. Ten earthquakes in the Korean peninsula and its vicinity are selected for the feasibility study. We observed that location results are not reliable when earthquakes occur outside of the seismic network. Earthquakes inside the seismic network, however, can be located very rapidly for the purpose of earthquake early warning. Seoul metropolitan area may secure $10{\sim}50$ seconds of warning time before any strong shaking starts for certain events. Carefully orchestrated actions during the given warning time should be able to reduce hazard and mitigate damages due to potentially disastrous earthquakes.

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 2003.03a
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• pp.77-84
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• 2003

For stochastic strong ground motion simulation, frequency-dependent Q model (= $Q_{o}$ $f^{η}$) were evaluated for major geographical blocks according to the epicentral distance ranges by using a lateral Q tomography technique. The inversed Q results were used to qualitatively identify seismic albedos of each Q blocks and were compared with the previous Q studies. In addition, a functional Q model calibrated to the low frequency spectra of local earthquakes were suggested especially for use in analysing large and distant regional earthquake events.s.

• Earthquakes and Structures
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• v.4 no.3
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• pp.325-339
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• 2013

A number of structural and modal parameters are derived from the strong motion records of an instrumented G + 9 storeyed RC building during Bhuj earthquake, 26 Jan. 2001 in India. Some of the extracted parameters are peak floor accelerations, storey drift and modal characteristics. Modal parameters of the building are also compared with the values obtained from ambient vibration survey of the instrumented building after the occurrence of earthquake. These parameters are further used for calibrating the accuracy of fixed-base Finite Element (FE) models considering structural and non-structural elements. Some conclusions are drawn based on theoretical and experimental results obtained from strong motion records and time history analysis of FE models. An important outcome of the study is that strong motion peak acceleration profile in two horizontal directions is close to FE model in which masonry infill walls are modeled.

• Steel and Composite Structures
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• v.34 no.5
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• pp.625-641
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• 2020

The realistic modeling of the beam-column semi-rigid connection in steel frames attracted the attention of many researchers in the past for the seismic analysis of semi-rigid frames. Comparatively less studies have been made to investigate the behavior of steel frames with semi-rigid connections under different types of earthquake. Herein, the seismic behavior of semi-rigid steel frames is investigated under both far and near-field earthquakes. The semi-rigid connection is modeled by the multilinear plastic link element consisting of rotational springs. The kinematic hysteresis model is used to define the dynamic behavior of the rotational spring, describing the nonlinearity of the semi-rigid connection as defined in SAP2000. The nonlinear time history analysis (NTHA) is performed to obtain response time histories of the frame under scaled earthquakes at three PGA levels denoting the low, medium and high-level earthquakes. The other important parameters varied are the stiffness and strength parameters of the connections, defining the degree of semi-rigidity. For studying the behavior of the semi-rigid frame, a large number of seismic demand parameters are considered. The benchmark for comparison is taken as those of the corresponding rigid frame. Two different frames, namely, a five-story frame and a ten-story frame are considered as the numerical examples. It is shown that semi-rigid frames prove to be effective and beneficial in resisting the seismic forces for near-field earthquakes (PGA ≈ 0.2g), especially in reducing the base shear to a considerable extent for the moderate level of earthquake. Further, the semi-rigid frame with a relatively weaker beam and less connection stiffness may withstand a moderately strong earthquake without having much damage in the beams.

• Earthquakes and Structures
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• v.8 no.6
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• pp.1363-1386
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• 2015

The October 23 2011 Van Earthquake is studied from an earthquake engineering point of view. Strong ground motion processing was performed to investigate features of the earthquake source, forward directivity effects during the rupture process as well as local site effects. Strong motion characteristics were investigated in terms of peak ground motion and spectral acceleration values. Directiviy effects were discussed in detail via elastic response spectra and wide band spectograms to see the high frequency energy distributions. Source parameters and slip distribution results of the earthquake which had been proposed by different researchers were summarized. Influence of the source parameters on structural response were shown by comparing elastic response spectra of Muradiye synthetic records which were performed by broadband strong motion simulations of the earthquake. It has been emphasized that characteristics of the earthquake rupture dynamics and their effects on structural design might be investigated from a multidisciplinary point of view. Seismotectonic calculations (e.g., slip pattern, rupture velocity) may be extended relating different engineering parameters (e.g., interstorey drifts, spectral accelerations) across different disciplines while using code based seismic design approaches. Current state of the art building codes still far from fully reflecting earthquake source related parameters into design rules. Some of those deficiencies and recent efforts to overcome these problems were also mentioned. Next generation ground motion prediction equations (GMPEs) may be incorporated with certain site categories for site effects. Likewise in the 2011 Van Earthquake, Reverse/Oblique earthquakes indicate that GMPEs need to be feasible to a wider range of magnitudes and distances in engineering practice. Due to the reverse faulting with large slip and dip angles, vertical displacements along with directivity and fault normal effects might significantly affect the engineering structures. Main reason of excessive damage in the town of Erciş can be attributed to these factors. Such effects should be considered in advance through the establishment of vertical design spectra and effects might be incorporated in the available GMPEs.

• 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.

• Structural Monitoring and Maintenance
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• v.7 no.4
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• pp.367-392
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• 2020

The specific characteristics of near-field earthquake records can lead to different dynamic responses of bridges compared to far-field records. However, the effect of near-field strong ground motion has often been neglected in the seismic performance assessment of the bridges. Furthermore, damage to horizontally curved multi-frame RC box-girder bridges in the past earthquakes has intensified the potential of seismic vulnerability of these structures due to their distinctive dynamic behavior. Based on the nonlinear time history analyses in OpenSEES, this article, assesses the effects of near-field versus far-field earthquakes on the seismic performance of horizontally curved multi-frame RC box-girder bridges by accounting the vertical component of the earthquake records. Analytical seismic fragility curves have been derived thru considering uncertainties in the earthquake records, material and geometric properties of bridges. The findings indicate that near-field effects reasonably increase the seismic vulnerability in this bridge sub-class. The results pave the way for future regional risk assessments regarding the importance of either including or excluding near-field effects on the seismic performance of horizontally curved bridges.