• Journal of the Computational Structural Engineering Institute of Korea
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• v.35 no.1
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• pp.29-34
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• 2022

In this paper, the floor acceleration for the seismic design of non-structural elements was evaluated using the core shape as a planar variable. Linear time history analysis using 20 models with 5 different planes and 4 different floors on each plane depending on the change in the shape (position and specific gravity) of the core in the square biaxially symmetric plane was performed. The analysis confirmed that the torsional amplification of the floor acceleration was up to 1.7 times in the plane subjected to eccentricity depending on the position of the core, and the effect of torsion was the greatest in the middle floor of the structure. In a plane where only the specific gravity of the core was changed without eccentricity, when the period was less than 0.4694 s, the maximum floor acceleration decreased in the lower floors and increased in the upper floors as the period increased. Conversely, when the period was 0.4694 s or more, it was confirmed that the floor acceleration increased in the lower part and decreased in the upper part as the period increased.

• Journal of Korea Society of Digital Industry and Information Management
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• v.11 no.1
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• pp.9-18
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• 2015

Numerical analysis of PSC box bridge bearings for high speed KTX train vehicles has been carried out as a virtual simulation for Ubiquitous Technology. Improved numerical models of bridge, vehicle and interaction between bridge and train are considered, where bending and torsional modes are provided, whereas the exist UIC code is applied by the simplified HL loading. Dynamic and static analysed results are compared to get Dynamic Amplification Factors (D. A. F.) for maximum deflections and bending stresses up to running speed of 500 km/h. Equation from the regression analysis for the D. A. F. is presented. Sliding distance of the bearings for various KTX running speeds is compared with maximum and accumulated distances by the dynamic behaviors of PSC box bridge. Dynamic and static simulated sliding distances of the bearings according to the KTX running speed are proved as a major parameter in spite of the specifications of AASHTO and EN1337-2 focused on the distance by temperature variations.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.15 no.3
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• pp.421-432
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• 2002

In this study the modal characteristics and responses of an asymmetric structure with added viscoelastic dampers were investigated for design parameters such as eccentricity of stiffness and added dampers, the loss factor of the damping materials used. For modal characteristics, variation of the quantities such as natural frequencies, modal damping ratios, modal participation factors, and dynamic amplification factors were observed, and displacements at flexible and stiff edges, and at center of mass were obtained. Based on the results, the problem of the optimum damper distribution to minimize the torsional effects was addressed, and the proposed method for optimum damper distribution was applied to a multi-story structure to verify the applicability Finally the effect of viscous and viscoelastic dampers were compared by varying the loss factor of the viscoelastic material.

• Smart Structures and Systems
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• v.20 no.6
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• pp.641-656
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• 2017

The effects of vertical component of earthquakes on torsional amplification due to mass eccentricity in seismic responses of base-isolated structures subjected to near-field ground motions are studied in this paper. 3-, 6- and 9-story superstructures and aspect ratios of 1, 2 and 3 have been modeled as steel special moment frames mounted on Triple Concave Friction Pendulum (TCFP) bearings considering different period and damping ratios. Three-dimensional linear superstructures resting on nonlinear isolators are subjected to both 2 and 3 component near-field ground motions. Effects of mass eccentricity and vertical component of 25 near-field earthquakes on the seismic responses including maximum isolator displacement and base shear as well as peak superstructure acceleration are studied. The results indicate that the effect of vertical component on the responses of asymmetric structures, especially on the base shear is significant. Therefore, it can be claimed that in the absence of the vertical component, mass eccentricity has a little effect on the base shear increase. Additionally, the impact of this component on acceleration is remarkable so the roof acceleration of a nine-story structure has been increased 1.67 times, compared to the case that the structure is subjected to only horizontal components of earthquakes.

• Journal of Korean Association for Spatial Structures
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• v.21 no.1
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• pp.105-112
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• 2021

In this paper, the dynamic response was analyzed by performing linear dynamic analysis using historic earthquake loads on twisted-shaped structures and fixed structure among free-form high-rise structures with atypical elevation shape following prior studies. In addition, the dynamic characteristics of the analysis models according to the plane rotation angle of the twisted structure were compared and analyzed. As a result of the analysis, as the plane rotation angle of the twisted structure increased, the interlayer deformation rate increased in the high-rise part of 50th floors or more. The story shear force and the story absolute acceleration were similar in the entire structure. In the case of the story shear force, the response of the twisted shape model was rather reduced in the middle part. As a result of analyzing the dynamic response, the vulnerable layer where the response amplification of the twisted structure occurs was found to be 31st story.

• Earthquakes and Structures
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• v.11 no.5
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• pp.741-777
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• 2016

A simplified approach of assessing torsionally balanced (TB) and torsionally unbalanced (TU) low-medium rise buildings of up to 30 m in height is presented in this paper for regions of low-to-moderate seismicity. The Generalised Force Method of Analysis for TB buildings which is illustrated in the early part of the paper involves calculation of the deflection profile of the building in a 2D analysis in order that a capacity diagram can be constructed to intercept with the acceleration-displacement response spectrum diagram representing seismic actions. This approach of calculation on the planar model of a building which involves applying lateral forces to the building (waiving away the need of a dynamic analysis and yet obtaining similar results) has been adapted for determining the deflection behaviour of a TU building in the later part of the paper. Another key original contribution to knowledge is taking into account the strong dependence of the torsional response behaviour of the building on the periodic properties of the applied excitations in relation to the natural periods of vibration of the building. Many of the trends presented are not reflected in provisions of major codes of practices for the seismic design of buildings. The deflection behaviour of the building in response to displacement controlled (DC) excitations is in stark contrast to behaviour in acceleration controlled (AC), or velocity controlled (VC), conditions, and is much easier to generalise. Although DC conditions are rare with buildings not exceeding 30 m in height displacement estimates based on such conditions can be taken as upper bound estimates in order that a conservative prediction of the displacement profile at the edge of a TU building can be obtained conveniently by the use of a constant amplification factor to scale results from planar analysis.