• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2004.11a
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• pp.662-665
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• 2004

In this paper, based on shaking table test results on a seismically isolated bridge model, an inelastic numerical model is refined by using Bouc-Wen model representing the hysteretic behavior of isolators. Seismic responses of isolated bridges are numerically investigated varying with relative stiffness ratios, which is a ratio of the effective stiffness of isolator to the lateral stiffness of bridge pier. From the results, it is found that an adequate range of relative stiffness ratio could be defined for seismic design of isolated bridges without considering the flexibility of piers.

• Steel and Composite Structures
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• v.31 no.1
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• pp.85-98
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• 2019

Nonlinear seismic performances of code designed Perforated Steel Plate Shear Walls (P-SPSW) were studied. Three multi-storey (4-, 8-, and 12-storey) P-SPSWs were designed according to Canadian seismic provisions and their performance was evaluated using time history analysis for ground motions compatible with Vancouver response spectrum. The selected code designed P-SPSWs exhibited excellent seismic performance with high ductility and strength. The current code equation was found to provide a good estimation of the shear strength of the perforated infill plate, especially when the infill plate is yielded. The applicability of the strip model, originally proposed for solid infill plate, was also evaluated for P-SPSW and two different strip models were studied. It was observed that the strip model with strip widths equal to center to center diagonal distance between each perforation line could reasonably predict the inelastic behavior of unstiffened P-SPSWs. The strip model slightly underestimated the initial stiffness; however, the ultimate strength was predicted well. Furthermore, applicability of simple shear-flexure beam model for determination of fundamental periods of P-SPSWs was studied.

• Earthquakes and Structures
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• v.27 no.4
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• pp.317-329
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• 2024

Recent earthquakes have demonstrated that even when the beams and columns in a reinforced concrete frame remain intact, the integrity of the whole structure is undermined if the joint where these members connect fails. A good seismic performance of reinforced concrete frames depends on their ability to absorb seismic energy through inelastic deformations and to avoid a sudden development of collapse mechanism in event of a strong earthquake shaking. The primary objective of this investigation is to move the plastic hinge away from the beam-column joint region and hence reducing the damage to the joint region. In this research, the seismic performance of exterior beam-column joints with four types of confinement in joint region and inclined bars from column to beam is investigated experimentally. Control specimens without inclined bars and four types of confinement Square Hoop, Square Spiral, Circular Hoop and Circular Spiral were tested along with inclined bars were tested. Seismic performance was determined via load-deflection response, ductility, stiffness, energy dissipation, strain of beam reinforcement and crack pattern. Out of the four specimens with inclined bars, seismic performance of joint with Square Spiral confinement gave the best performance in terms of all parameters.

• Structural Engineering and Mechanics
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• v.68 no.2
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• pp.159-170
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• 2018

This paper aims to develop response modification factors for stiffness degrading structures by incorporating soil-structure interaction effects. A comprehensive parametric study is conducted to investigate the effects of key SSI parameters, natural period of vibration, ductility demand and hysteretic behavior on the response modification factor of soil-structure systems. The nonlinear dynamic response of 6300 soil-structure systems are studied under two ensembles of accelograms including 20 recorded and 7 synthetic ground motions. It is concluded that neglecting the stiffness degradation of structures can results in up to 22% underestimation of inelastic strength demands in soil-structure systems, leading to an unexpected high level of ductility demand in the structures located on soft soil. Nonlinear regression analyses are then performed to derive a simplified expression for estimating ductility-dependent response modification factors for stiffness degrading soil-structure systems. The adequacy of the proposed expression is investigated through sensitivity analyses on nonlinear soil-structure systems under seven synthetic spectrum compatible earthquake ground motions. A good agreement is observed between the results of the predicted and the target ductility demands, demonstrating the adequacy of the expression proposed in this study to estimate the inelastic demands of SSI systems with stiffness degrading structures. It is observed that the maximum differences between the target and average target ductility demands was 15%, which is considered acceptable for practical design purposes.

• Proceedings of the Korea Concrete Institute Conference
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• 1998.10a
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• pp.535-540
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• 1998

Nowadays, the pushover analysis technique is becoming a very useful tool for the prediction of inelastic behavior of structures in the seismic evaluation of existing buildings in the worldwide. However, the reliability of this analysis method has not been fully checked by the test results. The objective of this study is to verify the correlation between the experimental and analytical response of a high-rise nonseismic reinforced concrete frame using DRAIN-2DX program and the test results performed previously. This study concludes that the overall responses such as story-shear versus story-drift can be predicted with quite high reliability while the local deformations such as plastic rotations in the ends of critical members can not be described reasonably.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.27 no.4
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• pp.255-263
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• 2014

In this paper, seismic fragility analysis of lightning arrester is performed using capacity spectrum method(CSM). Since seismic fragility analysis of structure with many structural members is required to calculate many inelastic responses for several tens or hundreds of ground motions, simple method such as CSM is more appropriate than response history analysis(RHA). In general, accuracy of seismic response evaluated by CSM is less than that by RHA. In order to increase accuracy of CSM, equivalent SDOF method and performance point calculation technique are applied to CSM. Seismic fragility method proposed by Shinozuka et al. is used. In order to evaluate site effect of ground motions on seismic fragility, 60 different site classification earthquakes are selected as input ground motions. From the seismic fragility curves of lightning arrester evaluated by CSM and RHA, it can be observed that the seismic fragility curves evaluated by CSM are very similar to those by RHA. Also, it can be observed that main seismic failure mode of lightning arrest is bushing breakage.

• Proceedings of the Korea Concrete Institute Conference
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• 2003.05a
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• pp.949-954
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• 2003

In this paper, simplified modeling approach describing the hysteretic behavior of reinforced concrete columns is discussed. The inelastic response of a reinforced concrete column or pier subjected to cyclic deformation reversals or earthquake ground motion is evaluated by use of lumped hysteretic representation. For this purpose, the hystertic model under axial force variation is developed and implemented into a nonlinear finite element analysis program. The analytical predictions obtained with the new formulation are compared with test results and reveal accuracy and applicability in terms of strength and stiffness. In addition, comparison between results with and without axial force variation stresses the importance of the proposed approach.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2003.04a
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• pp.211-218
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• 2003

Most structures are expected to deform beyond the limit of linearly elastic behavior when subjected to strong ground motion. Seismic evaluation of structure requires an estimation of the structural performance in terms of displacement demand imposed by earthquakes on the structure. Nonlinear response history analysis(NRHA) is the most rigorous procedure to compute seismic performance among various inelastic analysis methods. But nonlinear analysis procedures necessitate more practical and reliable tools for predicting seismic behavior of structures. This paper presents a nonlinear direct spectrum method(NDSM) to evaluate seismic performance of structures, without iterative computations, given by the structural initial elastic period and yield strength from the pushover analysis, especially for MDF(multi degree of freedom) system. The purpose of this paper is to investigate the accuracy and reliability of this method from a point of view of various earthquakes and structure parameters.

• Magazine of the Korea Concrete Institute
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• v.11 no.1
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• pp.267-277
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• 1999

The pushover analysis technique is now attracting the world-wide interest for the prediction of elastic and inelastic behavior of structures in the seismic evaluation of existing buildings. However, the reliability of this analysis technique has not been fully checked by the test results in the case of structures with nonseismic details. The objective of this study is to verify the correlation between the experimental and analytical responses of a 1:12 scale 10-story reinforced concrete frame with non-seismic details by using DRAIN-2DX program and the test results performed previously. It is concluded from this comparison that the overall responses such as the relations between story shear versus interstory drift and the local deformations such as plastic rotations can be predicted with quite high reliability.

• Journal of the Earthquake Engineering Society of Korea
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• v.10 no.5 s.51
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• pp.11-23
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• 2006

This paper evaluates the seismic response of multi-span prestressed concrete girder bridges typically found in the New Madrid Seismic Zone region of the central United States. Using detailed nonlinear analytical models and synthetic ground motion records for Memphis, TN, nonlinear response history analyses are performed for two levels of ground motion: 10% probability of exceedance (PE) in 50 years, and 2% probability of exceedance (PE) in 50 years. The results show that the bridge performance is very good fur the 10% PE in 50 years ground motion level. However, the performance for the 2% PE in 50 years ground motion is not so good because it results in highly inelastic behavior of the bridge. Impact between decks results in large ductility demands on the columns, and failure of the bearings that support the girders. It is found that making the superstructure continuous, which is commonly performed for reducing dead load moments and maintenance requirements, results in significant improvement in the seismic response of prestressed concrete girder bridges.