• Earthquakes and Structures
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• v.8 no.6
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• pp.1481-1497
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• 2015

Vertical earthquake ground motion may magnify vertical dynamic responses of structures, and thus cause serious damage to bridges. As main support structures, piers and bearings play an important role in vertical seismic response analysis of girder bridges. In this study, the pier and bearing are simplified as a vertical series spring system without mass. Then, based on the assumption of small displacement, the equation of motion governing the simply-supported straight girder bridge under vertical ground motion is established including effects of vertical deformation of support structures. Considering boundary conditions, the differential quadrature method (DQM) is applied to discretize the above equation of motion into a MDOF (multi-degree-of-freedom) system. Then seismic responses of this MDOF system are calculated by a step-by-step integration method. Effects of support structures on vertical dynamic responses of girder bridges are studied under different vertical strong earthquake motions. Results indicate that support structures may remarkably increase or decrease vertical seismic responses of girder bridges. So it is of great importance to consider effects of support structures in structural seismic design of girder bridges in near-fault region. Finally, optimization of support structures to resist vertical strong earthquake motions is discussed.

• Journal of the Earthquake Engineering Society of Korea
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• v.19 no.3
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• pp.133-143
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• 2015

It is very important to assure the seismic performance of equipment as well as building structures in seismic design of nuclear power plant(NPP). Seismically isolated structures may be reviewed mainly on the horizontal seismic responses. Considering the equipment installed in the NPP, the vertical earthquake responses of the structure also should be reviewed. This study has investigated the vertical seismic demand of seismically isolated structure by lead rubber bearings(LRBs). For the numerical evaluation of seismic demand of the base isolated NPP, the Korean standard nuclear power plant (APR1400) is modeled as 4 different models, which are supported by LRBs to have 4 different horizontal target periods. Two real earthquake records and artificially generated input motions have been used as inputs for earthquake analyses. For the study, the vertical floor response spectra(FRS) were generated at the major points of the structure. As a results, the vertical seismic responses of horizontally isolated structure have largely increased due to flexibility of elastomeric isolator. The vertical stiffness of the bearings are more carefully considered in the seismic design of the base-isolated NPPs which have the various equipment inside.

• Journal of the Earthquake Engineering Society of Korea
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• v.20 no.5
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• pp.319-329
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• 2016

The Eradi Quake System (EQS) is a seismic isolation bearing system designed to minimize forces and displacements experienced by structures subjected to ground motion. The EQS dissipates seismic energy through friction of Poly Tetra Fluoro Ethylene (PTFE) disk pad. In general, a force-displacement relationship of EQS has post yield stiffness hardening during large inelastic displacement. In this study, seismic responses of seismically isolated nuclear power plant (NPP) subjected to design basis earthquake (DBE) and beyond design basis earthquakes (150% DBE and 167% DBE) are compared considering the post yield stiffness hardening effect of EQS. From the results, it can be observed that if the post-yield stiffness hardening effect of EQS is increased, the displacement response of EQS is reduced, and the acceleration and shear responses of containment structures of NPP is increased.

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 2003.03a
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• pp.422-429
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• 2003

A comparative study was performed for a suspension bridge to grasp the possible differences in seismic responses evaluated by several analytical methods. The items mainly investigated are the linear vs. nonlinear response the response spectrum method vs. the linear dynamic analysis method and the damping ratio and it's implementation into analysis procedures. According to the numerical example, it is found that the seismic responses are considerably affected by the damping-related parameters even though slight differences are shown depending on the response quantities md the exciting directions. On the other hand, it is also confirmed that the seismic responses are less affected by the analysis method-related parameters such as the response spectrum method vs. the linear dynamic analysis method, and the linear and nonlinear analysis method. The response spectrum method is expected to give conservative results for the examined bridge, provided that the design response spectrum in the Korean Highway Design Specification is modified according to the proper damping ratio.

• Structural Engineering and Mechanics
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• v.88 no.3
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• pp.251-262
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• 2023

This paper presents a method for assessing the dynamic responses of gravity-based structures (GBS) under various seismic loads, with a focus on fluid-structure-ground interactions. Models of GBSs and their surrounding environments were developed, incorporating interaction effects among the structure, seawater, and seabed. Dynamic responses of the GBS subjected to three seismic loads-Chi-Chi, Northridge01, and Northridge02-were calculated, with consideration of both horizontal and vertical accelerations, as well as displacements. Parametric studies indicated that the primary factors affecting the dynamic responses of GBS were seismic loads characterized by significant input forces and accelerations. The frictional force on the ground had minimal impact on the horizontal and vertical displacements of the GBS. Weight emerged as a critical factor in anchoring the GBS to the ground and minimizing vertical accelerations and displacements.

• Journal of the Earthquake Engineering Society of Korea
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• v.5 no.6
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• pp.65-76
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• 2001

Determination of ductility demand and prediction of nonlinear seismic responses of a structure under the earthquake ground motions have become a very important subject for evaluation of seismic performance in the performance based seismic design. In this study, the system ductility demand and nonlinear seismic responses of the steel moment framed structures by the nonlinear time history analysis are estimated and compared with those obtained from the capacity spectrum method suggested in ATC-40 and proposed method that is an improvement on the capacity spectrum method using the equivalent responses derived directly from a multi degree of freedom system. the adequacy and validity of the proposed method is verified by comparing the results evaluated by the method proposed in this study and the results obtained from method suggested in ATC-40 to the nonlinear seismic responses of the example structures from the nonlinear time history analysis.

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 2000.10a
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• pp.167-175
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• 2000

Seismic analyses of structures can`t be performed without considering the effect of soil-structure interaction and seismic responses of a structure taking into account the stiffnesses of a foundation-soil system show a significant difference from those with a rigid base. However, current seismic analyses of apartment building structures were carried out assuming a rigid base and ignoring the characteristics of a foundation and the properties of the underlying soil. In this study, seismic analyses of apartment buildings of a particular wall-slab structural type were carried out comparing seismic response spectra of a flexible base with those of a rigid base and UBC-97. Wall-slab type low-rise or mid-height apartment buildings built on the deep soil layer showed a rigid body motion with the reduced seismic responses due to the base isolation effect, indicating that it is too safe but uneconomical to utilize the design spectra of UBC-97 for the seismic analysis of a wall-slab type apartment buildings due to the too conservative design.

• Transactions of the Korean Society of Pressure Vessels and Piping
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• v.14 no.2
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• pp.11-15
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• 2018

A development plan for seismic capacity verification procedures of nuclear components based on the elastic-plastic strain (EPS) features is explained in this paper. The EPS methodology is more realistic to assess seismic responses of components to extreme seismic events beyond the safe shutdown earthquake (SSE) than current practices with the criteria of stress limits. The EPS based approach to analyze the seismic capacity of components can reduce over-conservatism in the current stress-based criteria and can incorporate the seismic responses of components deformed in plastic behavior by the motion of extreme earthquake.

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 1997.04a
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• pp.265-272
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• 1997

This paper presents the result of an international cooperative research on the post-correlation analysis of forced vibration tests and the prediction of earthquake responses of a large-scale seismic test structure. Through the post-correlation analysis, the properties of the soil layers are revised so that the best correlation in the responses may be obtained compared with the measured force vibration test data. Utilizing the revised soil properties as the initial linear values, the seismic responses are predicted for an earthquake using the equivalent linearlization technique based on the specified strain dependent characteristics of the shear moduli and damping ratios. It has been found that the predicted responses by the equivalent nonlinear procedure are in excellent agreement with the observed responses, which those using the initial properties are fairly off from the measured results.

• 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.