• Structural Engineering and Mechanics
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• v.28 no.5
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• pp.571-585
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• 2008

The purpose of this study is to investigate the linear earthquake behavior of the frame structures including subsoil with different stiffening members and to compare the results of each frame considered. These comparisons are made separately for displacement, bending moments and axial forces for frames with different storey and bay numbers for the time history and the modal analyses. The results of both methods are also compared. The results of the frames with subsoil are also compared with the results of the frames without subsoil. It is concluded that all stiffening members considered in this study decrease the lateral displacement of the frame and the bending moment of the columns and increase the axial force in the columns and that configuration of the bracing members come out to be an important parameter in braced frames since the frames with the same type of bracing give different results depending on configuration. It is also concluded that, in general, the absolute maximum displacements of the frames modeled with subsoil are larger than those of the frames modeled without subsoil.

• Earthquakes and Structures
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• v.15 no.1
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• pp.45-65
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• 2018

Over the last three decades, Performance-based Earthquake Engineering (PBEE) has been mainly developed for high seismicity regions. Although information is abundant for PBEE throughout the world, the application of PBEE to lower-seismicity regions, such as those where the magnitude of the maximum considered earthquake (MCE) is less than 6.5, is not always straightforward because some portions of PBEE may not be appropriate for such regions due to geological differences between high- and low-seismicity regions. This paper presents a brief review of state-of-art PBEE methodologies and introduces the seismic hazard of lower-seismicity regions, including those of the Korean Peninsula, with their unique characteristics. With this seismic hazard, representative low-rise RC MRF structures and high-rise RC wall residential structures are evaluated using PBEE. Also, the range of the forces and deformations of the representative building structures under the design earthquake (DE) and the MCE of South Korea are presented. These reviews are used to propose some ideas to improve the practice of state-of-art PBEE in lower-seismicity regions.

• Transactions of the Korean Society of Pressure Vessels and Piping
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• v.18 no.1
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• pp.19-25
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• 2022

Nuclear Power Plants (NPP) should be designed to have sufficient safety margins and to ensure seismic safety against earthquake that may occur during the plant life time. After the 9.12 Gyeongju earthquake accident, the structural integrity of nuclear power plants due to the beyond design basis earthquake is one of key safety issues. Accordingly, it is necessary to conduct structural integrity evaluations for domestic NPPs under beyond design basis earthquake. In this study, the Level 3 LBB (Leak Before Break) evaluation was performed by considering the beyond design basis earthquake for the surge line of a OPR1000 plant of which design basis earthquake was set to be 0.2g. The beyond design basis earthquake corresponding to peak ground acceleration 0.4g at the maximum stress point of the surge line was considered. It was confirmed that the moment behaviors of the hot leg and pressurized surge nozzle were lower than the maximum allowable loading in moment-rotation curve. It was also confirmed that the LBB margin could be secured by comparing the LBB margin through the Level 2 method. It was judged that the margin was secured by reducing the load generated through the compliance of the pipe.

• Steel and Composite Structures
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• v.25 no.1
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• pp.1-17
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• 2017

Seismic performance of hybrid steel frames defined as mixture of rigid and semi-rigid connections is investigated in this paper. Three frames with 10, 15 and 20 stories are designed with fully rigid connections and then with 4 patterns for semi-rigid connection placement, some of beam to column rigid connections would turn to semi-rigid. Each semi-rigid connection is considered with 4 different moment capacities and all rigid and semi-rigid frames consisting of 51 models are subjected to 5 selected earthquake records for nonlinear analysis. Maximum story drifts, roof acceleration and base shear are extracted for those 5 earthquake records and average values are obtained for each case. Based on numerical results for the proposed hybrid frames, story drifts remain in allowable range and the reductions in the maximum roof acceleration of 22, 29 and 25% and maximum base shear of 33, 31 and 54% occur in those 10, 15 and 20-story frames, respectively.

• Structural Engineering and Mechanics
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• v.72 no.4
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• pp.443-454
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• 2019

In order to reduce the residual drift of a structure in structural engineering field, a combined structural system (dual) consisting of steel buckling-restrained braced frame (BRBF) along with shear wall is proposed. In this paper, BRBFs are used with special reinforced concrete shear walls as combined systems. Some prototype models of the proposed combined systems as well as steel BRBF-only systems (without walls) are designed according to the code recommendations. Then, the nonlinear model of the systems is prepared using fiber elements for the reinforced concrete wall and appropriate elements for the BRBs. Seismic responses of the combined systems subjected to ground motions at maximum considered earthquake level are investigated and compared to those obtained from BRBFs. Results showed that the maximum residual inter-story drift from the combined systems is, on average, less than half of the corresponding value of the BRBFs. In this research, mean of absolute values of the maximum inter-story drift ratio demand obtained from combined systems is less than the 3% limitation, while this criterion has not been fulfilled by BRBF systems.

• Earthquakes and Structures
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• v.2 no.3
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• pp.279-295
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• 2011

This paper develops a probabilistic methodology for the seismic reliability analysis of structures with random properties. The earthquake loading is assumed to be described in terms of response spectra. The proposed methodology takes advantage of the response spectra and thus does not require explicit dynamic analysis of the actual structure. Uncertainties in the structural properties (e.g. member cross-sections, modulus of elasticity, member strengths, mass and damping) as well as in the seismic load (due to uncertainty associated with the earthquake load specification) are considered. The structural reliability is estimated by determining the failure probability or the reliability index associated with a performance function that defines safe and unsafe domains. The structural failure is estimated using a performance function that evaluates whether the maximum displacement has been exceeded. Numerical illustrations of reliability analysis of elastic and elastic-plastic single-story frame structures are presented first. The extension of the proposed method to elastic multi-degree-of-freedom uncertain structures is also studied and a solved example is provided.

• Structural Engineering and Mechanics
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• v.20 no.3
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• pp.347-362
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• 2005

The input energy to a base-isolated (BI) building during an earthquake is considered and formulated in the frequency domain. The frequency-domain approach for input energy computation has some notable advantages over the conventional time-domain approach. Sensitivities of the input energy to the BI building are derived with respect to uncertain parameters in the base-isolation system. It is demonstrated that the input energy can be of a compact form via the frequency integration of the product between the input component (Fourier amplitude spectrum of acceleration) and the structural model component (so-called energy transfer function). With the help of this compact form, it is shown that the formulation of earthquake input energy in the frequency domain is essential for deriving the sensitivities of the input energy to the BI building with respect to uncertain parameters. The sensitivity expressions provide us with information on the most unfavorable combination of the uncertain parameters which leads to the maximum energy input.

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 2005.03a
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• pp.177-184
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• 2005

Even in moderate to low seismic regions like Korean peninsular where wind loading usually governs the structural design of a tall building, the probable structural impact of the design basis earthquake or the maximum credible earthquake on the selected structural system should be considered at least in finalizing the design. In this study, by using response spectrum analysis and time history analysis method, seismic performance evaluation was conducted for wind-designed concentrically braced steel highrise buildings. Input ensemble was normalized to be compatible with expected peak ground acceleration. The analysis results showed that wind-designed concentrically braced steel highrise buildings possess significantly increased elastic seismic capacity due to the system overstrength resulting from the wind-serviceability criterion and the width-to-thickness ratio limits on steel members. The time history analysis tended to significantly underestimated the seismic response as compared to response spectrum analysis. Further detailed studies regarding selection and scaling scheme of input ground motions is needed.

• Journal of the Korea institute for structural maintenance and inspection
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• v.11 no.3
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• pp.185-191
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• 2007

For the seismic performance enhancement of residential flat plate structure and for the selection of earthquake records, the possibility of base isolation is evaluated and the time history results are reviewed. By evaluating a base isolated stiffness, a target period, and an envelope curve analysis, seismic performance of structure, which has strong rotational mode, is evaluated. For the propriety evaluation of earthquake records usage and scaling method, time history analysis is done with variables such as DBE(design base earthquake) level, MCE(maximum considerable earthquake) level, and 1.4DBE level. From the analysis results, following conclusions can be made; the earthquake records, which are used in base isolation analysis, should be selected by similar soil type which the structure is considered, and should be intensity scaled in a range of mean ${\pm}$ standard deviation of code based design response spectrum.

• Earthquakes and Structures
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• v.23 no.1
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• pp.23-34
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• 2022

This paper presents experimental studies on reinforced concrete moment resisting frames that have engineered cementitious composite (ECC) in plastic hinge length (PHL) of beam/column members and beam-column joints. A two-story frame structure reduced by a 1:3 scale was further tested through a shake-table (seismic simulator) using multiple levels of simulated earthquake motions. One model conformed to all the ACI-318 requirements for IMRF, whereas the second model used lower-strength concrete in the beam/column members outside PHL. The acceleration time history of the 1994 Northridge earthquake was selected and scaled to multiple levels for shake-table testing. This study reports the observed damage mechanism, lateral strength-displacement capacity curve, and the computed response parameters for each model. The tests verified that nonlinearity remained confined to beam/column ends, i.e., member joint interface. Calculated response modification factors were 11.6 and 9.6 for the code-conforming and concrete strength deficient models. Results show that the RC-ECC frame's performance in design-based and maximum considered earthquakes; without exceeding maximum permissible drift under design-base earthquake motions and not triggering any unstable mode of damage/failure under maximum considered earthquakes. This research also indicates that the introduction of ECC in PHL of the beam/column members' detailing may be relaxed for the IMRF structures.