• Earthquakes and Structures
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• v.18 no.5
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• pp.599-607
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• 2020

This paper deals with the experimental investigation on the behavior of RCS beam-column exterior joints. Two full-scale specimens of joints between reinforced concrete columns and steel beams are tested under cyclic loading. The objective of the test is to study the effect of steel fiber reinforced concrete (SFRC) on the seismic behavior of RCS joints. The load bearing capacity, story drift capacity, ductility, energy dissipation, and stiffness degradation of specimens are evaluated. The experimental results point out that the FRC joint is increased 20% of load carrying capacity and 30% of energy dissipation capacity in comparison with the RC joint. Besides, the FRC joint shown lower damage and better ductility than RC joint.

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 2002.09a
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• pp.266-273
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• 2002

Pushover analysis is frequently used for evaluation of seismic performance and determination of seismic demand of a building structure in the current structural engineering practice field. However, pushover analysis has a advantage for estimation of seismic demands, which cannot account for the contributions of higher modes to response or for a redistribution of inertia forces because of structural yielding and the associated changes in the vibration properties of the structures. Recently, Chopra and Coel(2001) derived uncoupled inelastic dynamic equation of motion with several assumptions in the pushover analysis. By using this approach, pushover analysis for each mode is carried out and modal pushover analysis method, which can consider higher mode effects of the building, was suggested. The principle objective of this study is to introduced the modal pushover analysis by Chopra et al.(2001) and investigated the applicability and validity of this method for the steel moment frames subjected to various earthquake ground motions.

• Journal of Korean Society of Steel Construction
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• v.25 no.1
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• pp.81-92
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• 2013

The objective of conventional seismic design is to ensure an acceptable safety level while avoiding catastrophic failures of structures and loss of life. Over the last many years, a large amount of research has been devoted into developing effective earthquake resistant systems in order to raise the seismic performance level of structures. The purpose of this study is to propose a new damping system, which realize not only increasing seismic performance but also easy repairing after an earthquake. The proposed damping system is slit in the bottom of wall with damping devices installed in the slit horizontally aiming to dissipate energy during earthquakes. Cyclic loading tests were conducted to investigate hysteretic behavior and energy dissipation capacity. Test results show that the proposed systems exhibit a stable hysteretic response and the energy dissipation in this system is concentrated on the damping devices.

• Journal of Korean Society of Steel Construction
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• v.18 no.5
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• pp.585-596
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• 2006

This study focuses on the seismic behavior of 3-, 9-, and 20-story steel moment resisting frame (MRF) structures designed in accordance with the 2000 International Building Code using different Response Modification factors (R factors), i.e., 8, 9, 10, 11, and 12. For a detailed case study, 30 different structures were evaluated for 20 ground motions representing the hazard level, which is equal to a 2% probability in 50 years (2% in 50 years). The results showed that the current R factors provide conservative designs for the 3- and 9-story buildings for the Collapse Prevention performance objective. the 20-story buildings, which were designed without using the minimum requirement of spectral acceleration CS prescribed in IBC 2000, did not satisfy the seismic performance for Collapse Prevention performance.

• Structural Engineering and Mechanics
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• v.77 no.1
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• pp.115-135
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• 2021

This paper focuses on examining the effects of span arrangements on displacement responses of plan-symmetric RC frame buildings designed using the direct displacement-based design (DDBD) method by employing non-linear analyses and the skew seismic attack. In order to show the desired performance of DDBD design approach, the force-based design approach is also used to examine the seismic performance of the selected structures. To realize this objective, 8-story buildings with different plans are selected. In addition, the dynamic behavior of the structures is evaluated by selecting 3, 7, and 12-story buildings. In order to perform non-linear analyses, OpenSees software is used for modeling buildings. Results of an experimental model are used to validate the analytical model implemented in OpenSees. The results of non-linear static and non-linear dynamic analyses indicate that changing span arrangements does not affect estimating the responses of structures designed using the DDBD approach, and the results are more or less the same. Next, in order to apply the earthquake in non-principle directions, DDBD structures, designed for one-way performance, are designed again for two-way performance. Time history analyses are performed under a set of artificial acceleration pairs, applied to structures at different angles. It is found that the mean maximum responses of earthquakes at all angles have very good agreement with the design-acceptable limits, while the response of buildings along the height direction has a relatively acceptable and uniform distribution. Meanwhile, changes in the span arrangements did not have a significant effect on displacement responses.

• Earthquakes and Structures
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• v.25 no.6
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• pp.399-415
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• 2023

In this study, we investigate the use of a negative stiffness tuned inerter damper system to improve the performance of a base-isolated structure. The negative stiffness tuned inerter damper system consists of a tuned inerter damper connected in parallel with a negative stiffness element. To find the optimal parameters for the base-isolated structure with negative stiffness tuned inerter damper system, we develop an optimization method based on performance criteria. The objective of the optimization is to minimize the superstructure acceleration response ratio, while ensuring that the base displacement response ratio remains below a specified target value. We evaluate the proposed method by conducting numerical analyses on an eight-story building. The structure is modeled using both a simplified 3-degree-of-freedom system and a more detailed story-by-story shear-beam model. Lastly, a comparative analysis using time history analysis is performed to compare the performance of the base-isolated structure with negative stiffness tuned inerter damper system with that of the base-isolated structure and base-isolated structure with tuned inerter damper systems. The results obtained from the comparative analysis show that the negative stiffness tuned inerter damper system outperforms the tuned inerter damper system in reducing the dynamic seismic response of the base-isolated structure. Overall, this study demonstrates that the negative stiffness tuned inerter damper system can effectively enhance the performance of base-isolated structures, providing improved seismic response reduction compared to other systems.

• Journal of the Earthquake Engineering Society of Korea
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• v.11 no.6
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• pp.1-14
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• 2007

Optimal design method of nonlinear damping system for seismic response control of adjacent structures is studied in this paper. The objective functions of the optimal design are defined by structural response and total amount of the dampers. In order to obtain a solution minimizing two mutually conflicting objective functions simultaneously, multi-objective optimization technique based on genetic algorithm is adopted. In addition, stochastic linearization method is embedded into the multi-objective framework to efficiently estimate the seismic responses of the adjacent structures interconnected by nonlinear hysteretic dampers without performing nonlinear time-history analyses. As a numerical example to demonstrate the effectiveness of the proposed technique, 20-story and 10-story buildings are considered and MR dampers of which hysteretic behaviors vary with the magnitude of the input voltage are considered as nonlinear hysteretic damper interconnecting two adjacent buildings. The proposed approach can provide the optimal number and capacities of the MR dampers, which turned out to be more economical than the uniform distribution system while maintaining similar control performance. The proposed damper system is verified to show more stable performance in terms of the pounding probability between two adjacent buildings. The applicability of the proposed method to the design problem for optimally placing semi-active control system is examined as well.

• Journal of the Korea Concrete Institute
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• v.16 no.5 s.83
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• pp.687-696
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• 2004

It has been known that practically unavoidable lap splices of longitudinal reinforcement in the plastic hinge region have a bad effect on the seismic performance of reinforced concrete bridge columns. Lap splices were usually located in the plastic hinge region of most bridge columns designed before the implementation of the new seismic design provisions of 1992 Korea Bridge Design specification. The objective of this research is to evaluate the seismic performance of full-sized reinforced concrete bridge piers with lap splice of longitudinal reinforcement in the plastic hinge region, and to develop an appropriate lateral confinement concept of RC bridge columns with lap-spliced longitudinal steels in low or moderate seismicity region. Eight test specimens in the aspect ratio of 4.0 were made with three types of lap splicing, two levels of confinement steel ratios and two types of tie configurations. It was confirmed from the Quasi-Static test that displacement ductility ratios were significantly reduced for nonseismic test columns with lap spliced longitudinal steels but were satisfied the seismic requirement for limited ductile design specimens. As a conclusion, pertinent lateral confinement content was proposed for the seismic. performance of RC bridge piers with $50\%$ lap-spliced longitudinal reinforcing steels in low or moderate seismicity region.

• Journal of Korean Association for Spatial Structures
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• v.11 no.2
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• pp.89-99
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• 2011

In this study, a smart base isolation system has been proposed to reduce dynamic responses of a spacial structure subjected to seismic excitation. MR dampers and low damping elastomeric bearings were used to compose a smart base isolation system and its vibration control performance has been investigated compared to that of the optimally designed lead-rubber bearing (LRB) isolation system. Control performance of smart base isolation system depends on control algorithm. Fuzzy controller was used in this study to effectively control the spacial structure having a smart base isolation system. Dynamic responses of the spacial structure with isolation system is conflict with base drifts and thus these two responses are selected as objective functions to apply multi-objective genetic algorithm to optimization of fuzzy controller. Based on numerical simulation results, it has been shown that the smart base isolation system proposed in this study can drastically reduce base drifts and seismic responses of the example spacial structure in comparison with the optimally designed LRB isolation system.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.1
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• pp.219-224
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• 2016

The vibration control performance of a semi-active damper connected to adjacent buildings subjected to seismic loads was investigated. The MR damper was used as a semi-active control device. A fuzzy logic control algorithm was used for effective control of the adjacent buildings connected to the MR damper. In the buildings control coupled with a MR damper, the response reduction of one building results in an increase in the response in another building. Because of these conflict characteristics, multi-objective optimization is required. Therefore, a fuzzy logic control algorithm for the control of a MR damper was optimized using a multi-objective genetic algorithm. Based on numerical analyses, the semi-active fuzzy control of MR damper for adjacent coupled buildings can provide good control performance.