• Multiscale and Multiphysics Mechanics
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• v.1 no.2
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• pp.143-156
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• 2016

Reinforced concrete (RC) structures require advanced analysis techniques for better estimation of their seismic responses, especially in the case of exhibiting complex three-dimensional coupling of torsional and flexural behaviors. This study focuses on validating a numerical approach for evaluating the seismic response of a three-dimensional unsymmetrical RC structure through the participation in the SMART 2013 international benchmark program. The benchmark program provides material properties, detailed drawings of the RC structure, and input ground motions for the seismic response evaluation. In this study, nonlinear constitutive models of concrete and rebar were formed and local tests were conducted to verify the constitutive models in finite element analysis. Elastic calibration of the finite element model of the SMART 2013 RC structure was performed by comparing numerical and experimental results in modal and linear time history analyses. Using the calibrated model, nonlinear earthquake analysis and seismic fragility analysis were performed to estimate the behavior and vulnerability of the RC structure with various ground motions.

• Earthquakes and Structures
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• v.24 no.2
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• pp.141-153
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• 2023

The presented paper considers infill masonry walls' influence on the seismic reliability of precast concrete frames. The recent Bojnord earthquake on May 13th, 2017 in Iran (MW 5.4) illustrated that the infill masonry walls play a crucial role in the damage extent and life safety issues of inhabitants in the precast concrete buildings. The incremental dynamic analysis (IDA) approach was used to determine the fragility curves of the represented damaged precast frame. Then, by integrating site hazard and structural fragilities, the seismic reliability of the represented precast frame was evaluated in different damage limit states. Additionally, the static pushover analysis (SPA) approach was used to assess the seismic performance assessment of the precast frame. Bare and infilled frames were modeled as 2D frames employing the OpenSees software platform. The multi-strut macro-model method was employed for infill masonry simulation. Also, a relatively efficient and straightforward nonlinear model was used to simulate the nonlinear behavior of the precast beam-column joint. The outputs show that consideration of the masonry infilled wall effect in all spans of the structural frame leads to a decrease in the possibility of exceedance of specified damage limit states in the structures. In addition, variation of hazard curves for buildings with and without consideration of infilled walls leads to a decrease in the reliability of the building's frames with masonry infilled walls. Furthermore, the lack of infill walls in the first story significantly affects the precast concrete frame's seismic reliability and performance.

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 1999.04a
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• pp.223-230
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• 1999

The seismic damage assessment to the postulated earthquake is attempted for the buildings in the model district of Seoul City. The capacity spectrum method is employed in which the vulnerability functions are expressed as functions of the spectral displacement. the database of the building stock is constructed and managed using Geographic Information System software. The model district is selected to represent the typical structural and residential characteristics of Seoul City The structural properties were collected from the design documents. The field inspections were carried out to find out the current status of the building. They are classified into 11 structural types. The fragility curves in HazUS are employed, The ground motions from the postulated earthquakes are simulated using the Boor's methods, The surface soil in the district is classified into 3 profiles using the depth as the parameter. The one-dimensional wave propagation method is used to calculate he filtered ground motion through surface soil layer. The average spectrum of this sample time histories is used as the demand curves. The calculated results are expressed in maps using GIS software ArcView 3.0a

• Nuclear Engineering and Technology
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• v.53 no.7
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• pp.2396-2406
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• 2021

The Pacific Earthquake Engineering Research (PEER) Center has been developing a performance-based earthquake engineering (PBEE) methodology, which is based on explicit determination of performance, e.g., monetary losses, in a probabilistic manner where uncertainties in earthquake ground motion, structural response, damage estimation, and losses are explicitly considered. To carry out the PEER PBEE procedure for a component of the nuclear power plant (NPP) such as the cable tray system, hazard curve and spectra were defined for two hazard levels of the ground motions, namely, operation basis earthquake, and safe shutdown earthquake. Accordingly, two sets of spectral compatible ground motions were selected for dynamic analysis of the cable tray system. In general, the PBEE analysis of the cable tray in NPP was introduced where the resulting floor motions from the time history analysis (THA) of the NPP structure should be used as the input motion to the cable tray. However, for simplicity, a finite element model of the cable tray was developed for THA under the effect of the selected ground motions. Based on the structural analysis results, fragility curves were generated in terms of specific engineering demand parameters. Loss analysis was performed considering monetary losses corresponding to the predefined damage states. Then, overall losses were evaluated for different damage groups using the PEER PBEE methodology.

• Nuclear Engineering and Technology
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• v.54 no.4
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• pp.1382-1393
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• 2022

This paper investigates the seismic behavior of an electrical cabinet considering the influence of equipment-anchor-interaction (EAI) that is generally not taken into consideration in a decoupled analysis. The hysteresis behavior of an anchor bolt in concrete was thereby considered to highlight this interaction effect. To this end, the experimental behavior of an anchor bolt under reversed cyclic loading was taken from the recently developed literature, and a numerical model for the anchor hysteresis was developed using the component approach. The hysteresis properties were then used to calibrate the multi-linear link element that is implemented as a boundary condition for the cabinet incorporating the EAI. To highlight this EAI further, the nonlinear time history analysis was performed for a cabinet considering the hysteresis behavior comparative to a fixed boundary condition. Additionally, the influence on the seismic fragility was evaluated for the operational and structural condition of the cabinet. The numerical analysis considering the anchor hysteresis manifests that the in-cabinet response spectra (ICRS) are significantly amplified with the corresponding reduction in the seismic capacity of 25% and 15% for an operational and structural safety condition under the selected protocols. Considering the fixed boundary condition over a realistic hysteresis behavior of the anchor bolt is more likely to overestimate the seismic capacity of the cabinet in a seismic qualification procedure.

• Earthquakes and Structures
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• v.14 no.3
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• pp.249-259
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• 2018

This paper aims to assess the seismic risk of a plane moment-resisting frames (MRFs) consisting of concrete-filled double skin steel tube (CFDST) columns and I-section steel beams. Firstly, three typical limit performance levels of CFDST structures are determined in accordance with the cyclic tests of seven CFDST joint specimens with 1/2-scaled and the limits stipulated in FEMA 356. Then, finite element (FE) models of the test specimens are built by considering with material degradation, nonlinear behavior of beam-column connections and panel zones. The mechanical behavior of the concrete material are modeled in compression stressed condition in trip-direction based on unified strength theory, and such numerical model were verified by tests. Besides, numerical models on 3, 6 and 9-story CFDST frames are established. Furthermore, the seismic responses of these models to earthquake excitations are investigated using nonlinear time-history analyses (NTHA), and the limits capacities are determined from incremental dynamic analyses (IDA). In addition, fragility curves are developed for these models associated with 10%/50yr and 2%/50yr events as defined in SAC project for the region on Los Angeles in the Unite State. Lastly, the annual probabilities of each limits and the collapse probabilities in 50 years for these models are calculated and compared. Such results provide risk information for the CFDST-MRFs based on the probabilistic risk assessment method.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.29 no.1
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• pp.1-11
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• 2017

Seismic risk analysis was performed based on the total stress and effective stress of caisson type quay wall and pier type quay wall. In order to consider the effective stress effect, the pore pressure of the ground was distributed, using Byrne(1991) simple formula to estimate parameter and applied to the finn model. Through the results of seismic risk analysis according to the total stress and effective stress analysis method, the necessity of effective stress analysis in the seismic design of the quay wall installed on the soft ground was confirmed.

• Journal of the Earthquake Engineering Society of Korea
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• v.8 no.3
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• pp.43-52
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• 2004

This paper describes a method of evaluating seismic system performance of highway transportation network in California. The basic element that plays a crucial role in this study is the fragility information of highway bridges in Caltrans' (California Department of Transportation) freeway network. The bridge fragility information is expressed as a function of the ground motion intensity, such as peak ground acceleration (PGA) or peak ground velocity (PGV). Network damage was evaluated under the 1994 Northridge earthquake and scenario earthquakes. A probabilistic model was developed to determine the effect of repair of bridge damage on the improvement of the network performance as days passed after the event. As an example, the system performance degradation measured in terms of an index, “Drivers Delay”, is calculated for the Los Angeles area transportation system, and losses due to Drivers Delay with and without retrofit were estimated.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.37 no.2
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• pp.133-141
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• 2024

Considering fluid-structure-soil interactions, a finite-element model for a liquid-storage tank is presented and the nonlinear earthquake response analysis is formulated. The tank structure is modeled considering shell elements with geometric and material nonlinearities. The fluid is represented by acoustic elements and combined with the structure using interface elements. To consider the soil-structure interactions, the near- and far-field regions of soil are modeled with solid elements and perfectly matched discrete layers, respectively. This approach is applied to the seismic fragility analysis of a 200,000 kL liquid-storage tank. The fragility curve is observed to be influenced by the amplification and filtering of rock outcrop motions at the site when the soil-structure interactions are considered.

• Steel and Composite Structures
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• v.19 no.1
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• pp.237-262
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• 2015

In this study, we try to compare different intensity measures for evaluating nonlinear response of bridge structure. This paper presents seismic analytic fragility of a three-span concrete girder highway bridge. A complete detail of bridge modeling parameters and also its verification has been presented. Fragility function considers the relationship of intensities of the ground motion and probability of exceeding certain state of damage. Incremental dynamic analysis (IDA) has been subjected to the bridge from medium to strong ground motions. A suite of 20 earthquake ground motions with different range of PGAs are used in nonlinear dynamic analysis of the bridge. Complete sensitive analyses have been done on the response of bridge and also efficiency and practically of them are studied to obtain a proficient intensity measure for these types of structure by considering its sensitivity to the period of the bridge. Three dimensional finite element (FE) model of the bridge is developed and analyzed. The numerical results show that the bridge response is very sensitive to the earthquake ground motions when PGA and Sa (Ti, 5%) are used as intensity measure (IM) and also indicated that the failure probability of the bridge system is dominated by the bridge piers.