• Journal of the Earthquake Engineering Society of Korea
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• v.13 no.5
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• pp.51-60
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• 2009

To secure the structural safety of structures and members against earthquakes, the plastic deformation capacity demand of members should be accurately predicted. In the present study, a method for the evaluation of the plastic deformations of members for moment frames was developed. To facilitate the practical use of the proposed method in equivalent seismic design, the plastic deformations of members were evaluated based on the results of elastic analysis, without using nonlinear analysis. The plastic deformation demands of members were formulated as functions of story drift demand, redistributed moment and member stiffness. Story drift demand and moment redistribution were directly determined from elastic analysis. The proposed method was applied to an 8 story-2 bay moment frame, and the predicted plastic deformations were verified using nonlinear analysis. The results showed that the proposed method could be used to accurately predict the member plastic rotations with simple calculations. The proposed method can be applied both to the earthquake design of new structures and to the performance evaluation of existing structures.

• Structural Engineering and Mechanics
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• v.66 no.2
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• pp.217-227
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• 2018

In the last decades, valuable results have been reported regarding conventional passive, active, semi-active, and hybrid structural control systems on two-dimensional and a few three-dimensional shear buildings. In this research, using a three-dimensional finite element model of high-rise concrete structures, designed by performance based plastic design method, it was attempted to construct a relatively close to reality model of concrete structures equipped with Tuned Mass Damper (TMD) by considering the effect of soil-structure interaction (SSI), torsion effect, hysteresis behavior and cracking effect of concrete. In contrast to previous studies which have focused mainly on linearly designed structures, in this study, using performance-based plastic design (PBPD) design approach, nonlinear behavior of the structures was considered from the beginning of the design stage. Inelastic time history analysis on a detailed model of twenty-story concrete structure was performed under a far-field ground motion record set. The seismic responses of the structure by considering SSI effect are studied by eight main objective functions that are related to the performance of the structure, containing: lateral displacement, acceleration, inter-story drift, plastic energy dissipation, shear force, number of plastic hinges, local plastic energy and rotation of plastic hinges. The tuning problem of TMD based on tuned mass spectra is set by considering five of the eight previously described functions. Results reveal that the structural damage distribution range is retracted and inter-story drift distribution in height of the structure is more uniform. It is strongly suggested to consider the effect of SSI in structural design and analysis.

• Journal of the Earthquake Engineering Society of Korea
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• v.14 no.5
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• pp.41-51
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• 2010

For safe seismic evaluation and design, it is necessary to predict the plastic deformation demands of members. In the present study, a quick and reasonable method for the evaluation of member plastic deformations of dual systems was developed on the basis of results of elastic analysis, without using nonlinear analysis. Plastic deformations of beams, columns, and walls are functions of member stiffness, story drift ratio, and moment redistribution determined from elastic analysis. For dual systems with rigid connections between walls and beams, an increase in the plastic deformations of beams due to the rocking effect was considered. The proposed method was applied to 8-story dual systems and the predicted plastic deformations were compared with the results of nonlinear analysis. The results showed that the proposed method accurately predicted the member plastic deformations with simple calculations, but that for the accurate evaluation of member plastic deformations, the inelastic story drift ratio must also be predicted with accuracy. The proposed method can be applied to both the performance-based seismic design of new structures and the seismic evaluation of existing structures.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2008.04a
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• pp.483-489
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• 2008

Masonry infill walls are frequently used as interior partitions and exterior walls in low- or middlerise RC buildings In the structural design and assessment of structural behaviors of buildings, the infill walls are usually treated as non-structural elements and they are ignored in analytical models. In this study, seismic behaviors of RC frame with/without masonry infill walls were investigated. To this end, the infill walls were modeled as equivalent diagonal struts. Based on analytical results, it has been shown that masonry infill walls can increase the global strength and stiffness of a structure. Accordingly, inter-story drift ratio will be decreased but seismic forces applied to the structure were increased than design seismic load because natural period of the structure was decreased. It is also seen from the analytical results that the inelastic deformation of RC frame with soft story is concentrated on the first story columns and thus, partial damage may have possibility of collapse of system.

• Korean Journal of Construction Engineering and Management
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• v.4 no.4 s.16
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• pp.137-144
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• 2003

Recently, the interest in a complex building increases rapidly in Korea. High-rise complex is not simply the combination of a residential apartment and a business office as previous but a building with the object of the convenience of the residents familiar with city-life style through adapting the high class life style and new residential culture to the business space, and the efficiency in using the limited building site in the town. This study presents an exploratory analysis focusing the structural system with the help of the extensive survey of the construction site in Korea, and aims a guideline for the structural design and construction of high rise complex. Through the survey, change and development in the design and the construction can be seen as the height and size of the complex grow. It is almost indispensable to design a structural system against lateral forces like earthquake or wind, which is usually measured by story drift ratio or story displacement. Improvement of the structural materials and their usages is also included for the efficiency of the structural system. Useful slab-beam system contributing to the decrease of the story height is still a concern.

• Journal of the Earthquake Engineering Society of Korea
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• v.20 no.7_spc
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• pp.553-560
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• 2016

After an earthquake occurred in the Gyeongju, 2016, many low-story buildings have been questioned in terms of the seismic performance since mostly they have been exempted from the seismic design requirement since 1988. In this study, a 3-story moment resisting frame (MRF) building was analyzed and evaluated the seismic performance. Due to the insufficient seismic performance required for the seismic performance levels, three different seismic retrofit schemes were proposed and their seismic performances were re-evaluated. While steel brace and open shear wall retrofit systems mainly focused on the strength retrofit, the VES damper retrofit system is mainly to enhance the energy dissipation capacity of the system and resultes in the increased ductility. The original building and 3 retrofitted buildings were evaluated using the nonlinear static and nonlinear dynamic analyses and suggestions were proposed. Through the analysis of nonlinear time history and push-over using MIDAS/Gen program, damages of the building in terms of top story and average story drift and effect of reinforcement were analyzed.

• Structural Engineering and Mechanics
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• v.30 no.4
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• pp.445-466
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• 2008

This paper presents a novel structural damage detection method with a new damage index based on the statistical moments of dynamic responses of a structure under a random excitation. After a brief introduction to statistical moment theory, the principle of the new method is put forward in terms of a single-degree-of-freedom (SDOF) system. The sensitivity of statistical moment to structural damage is discussed for various types of structural responses and different orders of statistical moment. The formulae for statistical moment-based damage detection are derived. The effect of measurement noise on damage detection is ascertained. The new damage index and the proposed statistical moment-based damage detection method are then extended to multi-degree-of-freedom (MDOF) systems with resort to the leastsquares method. As numerical studies, the proposed method is applied to both single and multi-story shear buildings. Numerical results show that the fourth-order statistical moment of story drifts is a more sensitive indicator to structural stiffness reduction than the natural frequencies, the second order moment of story drift, and the fourth-order moments of velocity and acceleration responses of the shear building. The fourth-order statistical moment of story drifts can be used to accurately identify both location and severity of structural stiffness reduction of the shear building. Furthermore, a significant advantage of the proposed damage detection method lies in that it is insensitive to measurement noise.

• Journal of the Korea institute for structural maintenance and inspection
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• v.14 no.2
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• pp.82-88
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• 2010

The purpose of this research is a seismic capacity evaluation and strengthening of existing railway station buildings, which were constructed before the seismic design code activated. The seismic capacity of 2nd story RC station building is evaluated by using nonlinear time-history analysis. Analysis results are checked by story drift ratio and story shear, which are described in design code. As a result, the story shears are exceeding the base shear of the design code, the appropriate seismic strengthening methods are needed. To improve the seismic capacity, metallic dampers are used. Evaluation parameters are metallic damper shape and damper installation methods. Dampers are installed in four places in X and Y directions of station buildings. By reviewing of time-history analysis results, the metallic damper, which is installed inverted K-brace type, shows a better seismic performance than other damper shape and installation methods.

• Journal of Korean Association for Spatial Structures
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• v.22 no.1
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• pp.33-40
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• 2022

When the center of stiffness and the center of mass of the structure differ under the seismic load, torsion is caused by eccentricity. In this study, an analysis model was modeled in which the positions of the core and the plane rotation axis of a 60-story torsional atypical structure with a plane rotation angle of 1 degree per floor were different. The structural behavior of the analysis model was analyzed, and the earthquake response behavior of the structure was analyzed based on the time history analysis results. As a result, as the eccentricity of the structure increased, the eccentricity response was amplified in the high-rise part, and the bending and torsional behavior responses were complex in the low-order vibration mode. As a result of the analysis, the maximum displacement and story drift ratio increased due to the torsional behavior. The maximum story shear force and the story absolute maximum acceleration showed similarities for each analysis model according to the shape of the vibration mode of the analysis model.

• Earthquakes and Structures
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• v.23 no.2
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• pp.197-206
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• 2022

Recently, steel-timber hybrid buildings have become prevalent worldwide because several advantages of both steel and timber structures are maintained in the hybrid system. In Taiwan, seismic design specification related to steel-timber hybrid buildings remains void. In this study, the ductility capacity of steel-timber hybrid buildings in Taiwanese seismic design specification is first proposed and evaluated using nonlinear incremental dynamic analysis (IDA). Three non-linear structural models, 12-story, 8-story, and 6-story steel-timer hybrid buildings were constructed using OpenSees. In each model, Douglas-fir was adopted to assemble the upper 4 stories as a timber structure while a conventional steel moment-resisting frame was designated in the lower part of the model. FEMA P-695 methodology was employed to perform IDAs considering 44 earthquakes to assess if the ductility capacity of steel-timber hybrid building is appropriate. The analytical results indicate that the current ductility capacity of steel moment-resisting frames can be directly applied to steel-timber hybrid buildings if the drift ratio of each story under the seismic design force for buildings in Taiwan is less than 0.3%. As a result, engineers are able to design a steel-timber hybrid building straightforwardly by following current design specification. Otherwise, the ductility capacity of steel-timber hybrid buildings must be modified which depends on further studies in the future.