• Proceedings of the Korean Geotechical Society Conference
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• 2004.03b
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• pp.245-252
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• 2004

When some enormous earthquake hazards broke out in the neighboring Japan and Taiwan, many Korean earthquake engineers thought that seismic guidelines must be adjusted safely and economically to consider the moderate earthquake characteristics. In the present aseismic guideline for liquefaction potential assessment, a simplified method using SPT-N value and a detail method based on the dynamic lab-tests were introduced. However, it is said that these methods based on the equivalent stress concept to simplify an irregular earthquake are not reliable to simulate the kaleidoscopical characteristics of earthquake loading correctly. Especially, even though various data from the dynamic lab-test can be obtained, only two data, a maximum cyclic load and a number of cycle at an initial liquefaction are used to determine the soil resistance strength in the detailed method. In this study, a new assessment of liquefaction potential is proposed and verified. In the proposed assessment, various data from dynamic lab-tests are used to determine the unique soil resistance characteristic and a site specific analysis is introduced to analyze the irregular earthquake time history itself. Also, it is found that the proposed assessment is reasonable because it is devised to reflect the changeable soil behavior under dynamic loadings resulted from the generation and development of excess pore water pressure.

• Coupled systems mechanics
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• v.6 no.3
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• pp.229-249
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• 2017

A new technique to mitigate irregular buildings with soil structure interaction (SSI) effect subjected to critical seismic waves is presented. The L-shape in plan irregular building for various reasons was selected, subjected to seismic a load which is a big problem for structural design especially without separation gap. The L-shape in plan building with different dimensions was chosen to study, with different rectangularity ratios and various soil kinds, to show the effect of the irregular building on the seismic response. A 3D building subjected to critical earthquake was analyzed by structural analysis program (SAP2000) fixed and with SSI (three types of soils were analyzed, soft, medium and hard soils) to find their effect on top displacement, base shear, and base torsion. The straining actions were appointed and the treatment of the effect of irregular shape under critical earthquake was made by using tuned mass damper (TMD) with different configurations with SSI and without. The study improve the success of using TMDs to mitigate the effect of critical earthquake on irregular building for both cases of study as fixed base and raft foundation (SSI) with different TMDs parameters and configurations. Torsion occurs when the L-shape in plan building subjected to earthquake which may be caused harmful damage. TMDs parameters which give the most effective efficiency in the earthquake duration must be defined, that will mitigate these effects. The parameters of TMDs were studied with structure for different rectangularity ratios and soil types, with different TMD configurations. Nonlinear time history analysis is carried out by SAP2000 with El Centro earthquake wave. The numerical results of the parametric study help in understanding the seismic behavior of L-shape in plan building with TMDs mitigation system.

• Earthquakes and Structures
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• v.5 no.6
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• pp.753-779
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• 2013

One of the most important issues in progressive collapse mechanism of the buildings is evaluation of the collapse distribution in presence of the earthquake loads. Here, collapse propagation is investigated by tracking down the location and type of the collapsed beam and column elements, from the first element to the entire buildings. 6-story reinforced concrete ordinary moment resisting frame buildings with one directional mass eccentricity of 0%, 5%, 15% and 25% are studied to investigate differences among the progressive collapse mechanism of the regular and irregular buildings. According to the results of the nonlinear time history analyses, there are some patterns to predict progressive collapse scenarios in beam and column elements of the similar regular and irregular buildings. Results also show that collapse distribution patterns are approximately independent of the earthquake records.

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 1998.04a
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• pp.58-65
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• 1998

A purpose of this research is to develope the calculation methods of design input seismic loads, Where, calculation methods are ; (1) Considering different recurrence period of earthquakes which was proposed by ATC 14. (2) Using earthquake records which was modified Korean codes. Responce spectra that was adopted by codes has an estimated recurrence interval of 500 years, with approximately a 90 percent probability of not being exceeded in 50 years. But If we considered the life-time of existing buildings in some cases, response spectra be modified with return period of earthquakes. If we be design highrise and irregular buildings, dynamic analysis method that use time history records should be used. But in Korea, time history records of earthquakes was very few. Therefore to use foreign countries's earthquake record, it is need to select of records considered Korean coeds. As a results, this study propose a calculation method of seismic design input loads that considered return period of earthquakes and also propose using method of earthquakes.

• Proceedings of the Korea Concrete Institute Conference
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• 2005.05a
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• pp.219-222
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• 2005

Many RC building structures of multiple uses constructed in Korea have the irregularities of torsion and soft story at bottom stories. A typical irregular building was selected as prototype and shaking table tests were performed to investigate the seismic performance of this building. The objective of this study is to evaluate the correlation between the experimental and analytical responses of this irregular building structure subjected to the earthquake excitation by using OpenSees(Open System for Earthquake Engineering Simulation). The results of analyses simulate well the behavior of the building having torsional irregularity and weak stories.

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 2005.03a
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• pp.169-176
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• 2005

Many RC building structures of multiple uses constructed in Korea have the irregularities of torsion and soft story at bottom stories. A typical irregular building was selected as prototype and shaking table tests were performed to investigate the seismic performance of this building. The objective of this study is to evaluate the correlation between the experimental and analytical responses of this irregular building structure subjected to the earthquake excitation by using OpenSees(Open System for Earthquake Engineering Simulation). The results of analyses simulate well the effect of axial forces on the shear force of column and axial deformation. However, some discrepancy between analytical and experimental results in the distribution of shear forces and overturning deformation were observed.

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 2000.10a
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• pp.322-329
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• 2000

Current seismic design codes for building structures are based on the methods which can provide enough capacity to satisfy objected performance level and exactly evaluate the seismic performance of buildings. Pushover analysis of fast becoming an accepted method for the seismic evaluation of building structures. The popularity of this approximate, nonlinear static analysis method is due to its conceptual simplicity and ability to graphically describe a capacity and demand of structure. However, some of the shortcomings of the pushover analysis, especially for longer period and irregular buildings, is the inability of method to identify failure mechanisms due to effects of higher modes. In this paper proposed lateral load pattern which includes the contribution of higher modes of vibration for irregular building structure and compared to seismic response obtained by time history.

• Earthquakes and Structures
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• v.8 no.1
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• pp.185-204
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• 2015

This study investigates the impact of the earthquake incident angle on the structural demand and the influence of ground motion selection and scaling methods on seismic directionality effects. The structural demand produced by Non-Linear Time-History Analyses (NLTHA) varies with the seismic input incidence angle. The seismic directionality effects are evaluated by subjecting four three-dimensional reinforced concrete structures to different scaled and un-scaled records oriented along nine incidence angles, whose values range between 0 and 180 degrees, with an increment of 22.5 degrees. The results show that NLTHAs performed applying the ground motion records along the principal axes underestimate the structural demand prediction, especially when plan-irregular structures are analyzed. The ground motion records generate the highest demand when applied along the lowest strength structural direction and a high energy content of the records increases the structural demand corresponding to this direction. The seismic directionality impact on structural demand is particularly important for irregular buildings subjected to un-scaled accelerograms. However, the orientation effects are much lower if spectrum-compatible combinations of scaled records are used. In both cases, irregular structures should be analyzed first with pushover analyses in order to identify the weaker structural directions and then with NLTHAs for different incidence angles.

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 2005.03a
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• pp.153-160
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• 2005

A new nonlinear static analysis method, Effective Modal Pushover Analysis (EMPA) which can evaluate earthquake responses such as story drift and plastic rotation of plastic hinges addressing higher mode effects was developed. Unlike existing nonlinear static procedure based on properties of fundamental vibration mode, the EMPA performs nonlinear static analysis using multiple effective modes constructed by direct combination of natural vibration modes. Therefore higher mode effects can be efficiently considered. In the present study, procedures of the EPMA evaluating inelastic earthquake responese were established and the results were verified by nonlinear time history analysis. The EMPA can be applied to seismic evaluation of high-rise buildings and irregular buildings where higher mode effects become conspicuous.

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 2001.09a
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• pp.208-215
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• 2001

The vertical irregularities occurred in the structure may lessen the overall seismic capacity of the structure. Seismic capacity evaluation guidelines (e.g. FEMA 175, ATC-14) propose the criterion for the vertical irregularities of mass, stiffness and strength respectively. But, the criterion seems groundless and leads us to make a true/false decision only. This study is to draw a reasonable basis on which multi-level grading is possible based fur the evaluation of existing buildings. Time history analysis for 3-,5-, and 10-story steel frame structures has been performed using several earthquake data. ANN (Artificial Neural Network) is introduced to find the relative contribution factor of the irregularities along the irregular position. Also, the application system fur the seismic capacity evaluation can be established using the trained ANN.