• Journal of the Korean Geotechnical Society
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• v.33 no.12
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• pp.45-58
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• 2017

As many seismic codes for various facilities are changed into a performance based design code, demand for a reliable nonlinear response-history analysis (RHA) arises. However, the equivalent linear analysis has been used as a standard approach since 1970 in the field of site response analysis. So, the reliability of nonlinear RHA should be provided to be adopted in replace of equivalent linear analysis. In this paper, the reliability of nonlinear RHA is reviewed for a layered soil layer using Loma Prieta earthquake records in 1989. For this purpose, the appropriate way for selecting nonlinear soil models and the effect of base boundary condition for 3D analysis are evaluated. As a result, there is no significant differences between equivalent linear and nonlinear RHA. In case of 3D analysis, absorbing boundary condition should be applied at base to prevent rocking motion of the whole model.

• Structural Engineering and Mechanics
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• v.70 no.2
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• pp.143-152
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• 2019

In this study, stochastic responses of a cable-stayed bridge subjected to the spatially varying earthquake ground motion are investigated for variable local soil cases and wave velocities. Quincy Bay-view cable-stayed bridge built on the Mississippi River in Illinois, USA selected as a numerical example. The bridge is composed of two H-shaped concrete towers, double plane fan type cables and a composite concrete-steel girder deck. The spatial variability of the ground motion is considered with the coherency function, which is represented by the components of incoherence, wave-passage and site-response effects. The incoherence effect is investigated by considering Harichandran and Vanmarcke model, the site-response effect is outlined by using hard, medium and soft soil types, and the wave-passage effect is taken into account by using 1000, 600 and 200 m/s wave velocities for the hard, medium and soft soils, respectively. Mean of maximum response values obtained from the analyses are compared with those of the specific cases of the ground motion model. It is concluded that the obtained results from the bridge model increase as the differences between local soil conditions cases of the bridge supports change from firm to soft. Moreover, the variation of the wave velocity has important effects on the responses of the deck and towers as compared with those of the travelling constant wave velocity case. In addition, the variability of the ground motions should be considered in the analysis of long span cable-stayed bridges to obtain more accurate results in calculating the bridge responses.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.29 no.3
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• pp.261-268
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• 2016

Tuned Liquid Dampers(TLD) are energy dissipation devices that have been proposed to control the dynamics response of structure. The TLD has been shown to effectively control the wind response of structures. However, controlling responses of structures with TLD under seismic loads are not fully investigated. The objective of this study is to evaluate the seismic performance of single degree of freedom(SDF) with TLDs having various tuning and mass raitos. For this purpose, analytical studies are conducted. Different soil conditions are considered in this study. As a result, performance of TLD, appeared diffrently depending on the natural period, damping ratio of the structure. Also TLD tuning ratio appeared differently.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.28 no.1C
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• pp.31-40
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• 2008

This study presents the assessment of pseudostatic approach for obtaining the internal response of Single Column/Shaft subjected to earthquake loading. In numerical procedure, various lateral load transfer characteristics (p-y curve and Bi-linear curve) were used to model the nonlinear behavior of soil reactions including soil-pile interaction. The analysis using nonlinear soil model could estimate the seismic performance of soil-pile system, despite its relative simplicity. It was found that lateral behavior of single column/shaft obtained from the response displacement method was larger than those by seismic intensity method. To investigate the effects of soil-pile rigidity and pile head condition on the internal pile response, parametric studies were carried out for various soil models. The results from numerical analysis showed that lateral deflection was decreased with fixed condition of pile head and decreasing the soil-pile rigidity. The seismic analysis using Bi-linear model of JRA could reasonably predict the lateral behavior of Single Column/Shaft.

• Journal of the Earthquake Engineering Society of Korea
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• v.19 no.6
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• pp.273-282
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• 2015

In this study, shaking table test has been carried out for the dual frame passive control system for seismic performance verification of the proposed system. The proposed system was separated into two independent frameworks that are strength resistant core and frame structure by connecting to the damper. Moreover, the seismic performance improvement of the proposed system has been verified by comparing and analyzing the experimental results of the proposed system with an existing core system. As a result of the shaking table test, acceleration and displacement responses of dual-frame vibration control system are decreased than those of the existing strength resistant type core system. In the case of the core system, while the damage was concentrated on the column of first floor, the damage of the dual system was dispersed in each layer. The damage also was concentrated on the damper, almost no damage occurs to the structural members. It has been emphasized that installed dampers in the proposed dual system reduce the input energy of whole structure by absorbing seismic input energy, which leads overall system damage to be reduced.

• Journal of the Earthquake Engineering Society of Korea
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• v.12 no.4
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• pp.35-44
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• 2008

A self-centering energy-dissipative(SCED) bracing system has recently been developed as a new seismic force resistant bracing system. The advantage of the SCED brace system is that, unlike other comparable advanced bracing systems that dissipate energy such as the buckling restrained brace(BRB) system, it has a self-centering capability that reduces or eliminates residual building deformations after major seismic events. In order to investigate the effects of torsion on the SCED brace and BRB systems, nonlinear time history analyses were used to compare the responses of 3D model structures with three different amounts of frame eccentricity. The results of the analysis showed that the interstory drifts of SCED braced frames are more uniform than those of BRB frames, without regard to irregularity. The residual drift and residual rotation responses tended to decrease as irregularity increased. For medium-rise structures, the drift concentration factors(DCFs) for SCED systems were lower than those for BRB frames. This means that SCED-braced frames deform in a more uniform manner with respect to building height. The effect of the torsional irregularity on the magnitude of the DCFs was small.

• Journal of the Earthquake Engineering Society of Korea
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• v.14 no.4
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• pp.37-48
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• 2010

The seismic control effect of reinforced concrete structures with low energy dissipating capacity due to stiffness degradation is investigated through nonlinear time history analysis. The primary structure is idealized as a SDOF system of modified Takeda hysteresis rule and an elasto-perfectly-plastic nonlinear spring is added to represent a hysteretic damping device. Based on statistics of the numerical analysis, equivalent linearization techniques are evaluated, and empirical equations for response prediction are proposed. As a result, estimation of the ductility demand with proposed empirical equations is more desirable than the equivalent linearization techniques. The optimal yield strengths based on empirical equations are significantly different from the optimal yield strength of elasto-perfectly-plastic systems. Also, the results indicate that the reduction effect of the ductility demand is more remarkable for smaller natural periods.

• Journal of Korean Society of Steel Construction
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• v.9 no.4 s.33
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• pp.625-635
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• 1997

The base isolation technique and its benefits in reducing the transmitted earthquake energy into a structure have gained increasing recognition during the last two decades. Unfortunately, the current available design procedures, especially for base-isolated bridges, seem inadequate and too restrictive. As a result, practical design procedure still relies upon a series of deterministic time history analyses. In this study, the evaluation of the possibility of the normal mode method to predict the nonlinear seismic responses of base isolated bridges has been performed. The applicability has been examined through the numerical approach with isolator's elastic or plastic states of the base isolated bridges. Numerical results show that the 1st. mode period and the various responses are varied with the state but are conversed. And, the result show that the normal mode method is applicable to predict the seismic responses and to design the babe isolated bridge. Various analysis method to bridges with bilinearized hysteresis isolator and various pier heights are evalulated.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.11 no.5
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• pp.1805-1813
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• 2010

This paper presented regarding an parametric study to investigate seismic capacity evaluation of semi-rigid steel frame infilled with composit panel. In order to propose the optimum retrofit of the steel frame, we analysed the various pattern of retrofitted steel frame subjected to weak/medium earthquake. Steel frame with composit panel was analysed by Time history analyses analysis. The model were analysed using the suites of ground motion developed by NEHRP project on steel moment resisting frame. These earthquakes consist of 20 horizontal ground acceleration record each, i.e., a 10%, 50% probability of accidence in a 50 year period. We considered the semi-rigid connection which are commonly used in field, and modeled the nonlinear connection element (GAP) between panel and frame. It was shown that how is the steel frame with composit panel effected. We also examined the response of retrofitted frame.

• Structural Engineering and Mechanics
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• v.76 no.6
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• pp.751-763
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• 2020

Available records of recent earthquakes show that near-field earthquakes have different characteristics than far-field earthquakes. In general, most of these unique characteristics of near-fault records can be attributed to their forward directivity. This phenomenon causes the records of ground motion normal to the fault to entail pulses with long periods in the velocity time history. The energy of the earthquake is almost accumulated in these pulses causing large displacements and, accordingly, severe damages in the building. Damage to structures caused by past earthquakes raises the need to assess the chance of future earthquake damage. There are a variety of methods to evaluate building seismic vulnerabilities with different computational cost and accuracy. In the meantime, fragility curves, which defines the possibility of structural damage as a function of ground motion characteristics and design parameters, are more common. These curves express the percentage of probability that the structural response will exceed the allowable performance limit at different seismic intensities. This study aims to obtain the fragility curve for low- and mid-rise structures of reinforced concrete moment frames by incremental dynamic analysis (IDA). These frames were exposed to an ensemble of 18 ground motions (nine records near-faults and nine records far-faults). Finally, after the analysis, their fragility curves are obtained using the limit states provided by HAZUS-MH 2.1. The result shows the near-fault earthquakes can drastically influence the fragility curves of the 6-story building while it has a minimal impact on those of the 3-story building.