• Journal of the Earthquake Engineering Society of Korea
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• v.7 no.3
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• pp.47-55
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• 2003

This study proposed a convenient seismic design procedure for buckling-restrained braced frames based on the equivalent energy concept. The design process begins with the computation of input energy from response spectrum. Then the elastic energy and plastic energy are computed based on the equal energy concept. The computed plastic energy is distributed to each story along energy distribution ratio and the cross-sectional area of each brace is computed so that all the plastic energy is dissipated by the brace. The proposed procedure was applied to the design of three-, six-, and twenty-story steel frames with buckling-restrained braces, and artificial earthquake records were used for verification of the proposed method. According to analysis results, top story displacements of the low-rise structure satisfies the given target displacement however that of the twenty-story structure was much smaller than the given target displacement.

• Smart Structures and Systems
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• v.20 no.1
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• pp.53-60
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• 2017

Reinforced concrete shear wall is one of the most common structural forms for high-rise buildings, and seismic energy dissipation techniques, which are effective means to control structural vibration response, are being increasingly used in engineering. Reinforced concrete-mild steel damper stiffness-tandem energy dissipation coupling beams are a new technology being gradually adopted by more construction projects since being proposed. Research on this technology is somewhat deficient, and this paper investigates design principles and methods for two types of mild steel dampers commonly used for energy dissipation coupling beams. Based on the conception design of R.C. shear wall structure and mechanics principle, the basic design theories and analytic expressions for the related optimization parameters of dampers at elastic stage, yield stage, and limit state are derived. The outcomes provide technical support and reference for application and promotion of reinforced concrete-mild steel damper stiffness-tandem energy dissipation coupling beam in engineering practice.

• Nuclear Engineering and Technology
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• v.52 no.8
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• pp.1834-1846
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• 2020

The SMART (System-integrated Modular Advanced ReacTor) is an integral-type small modular reactor developed by KAERI (Korea Atomic Energy Research Institute). This paper discusses the development of a dynamic equivalent model of the SMART control rod drive mechanism that can be efficiently utilized for complicated analysis during the design of the SMART. A semi-empirical approach is used to develop the equivalent model; that is, the equivalent model is defined analytically and verified empirically. Two types of tests, dynamic characteristics tests and seismic loading tests, are conducted for the development and verification of the dynamic equivalent model, respectively. Acceleration response spectra from the seismic analysis based on the developed equivalent model show good agreement with those from the seismic loading tests.

• Wind and Structures
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• v.31 no.2
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• pp.153-164
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• 2020

In the design of buildings, lateral loading is one of the most important factors considered by structural designers. The concept of performance-based design (PBD) is well developed for seismic load. Whereas, wind design is mainly based on elastic analysis for both serviceability and strength. For tall buildings subject to extreme wind load, inelastic behavior and application of the concept of PBD bear consideration. For seismic design, current practice primarily presumes inelastic behavior of the structure and that energy is dissipated by plastic deformation. However, due to analysis complexity and computational cost, calculations used to predict inelastic behavior are often performed using elastic analysis and a response modification factor (R). Inelastic analysis is optionally performed to check the accuracy of the design. In this paper, a framework for application of an R factor for wind design is proposed. Theoretical background on the application and implementation is provided. Moreover, seismic and wind fatigue issues are explained for the purpose of quantifying the modification factor R for wind design.

• Earthquakes and Structures
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• v.4 no.1
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• pp.85-108
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• 2013

The research presented in this paper deals with the seismic protection of existing frame structures by means of passive energy dissipation. A displacement-based procedure to design dissipative bracings for the seismic protection of frame structures is proposed and some applications are discussed. The procedure is based on the displacement based design using the capacity spectrum method, no dynamic non linear analyses are needed. Two performance objective have been considered developing the procedure: protect the structure against structural damage or collapse and avoid non-structural damage as well as excessive base shear. The compliance is obtained dimensioning dissipative braces to limit global displacements and interstorey drifts. Reference is made to BRB braces, but the procedure can easily be extended to any typology of dissipative brace. The procedure has been validated through a comparison with nonlinear dynamic response of two 2D r.c. frames, one bare and one infilled. Finally a real application, on an existing 3D building where dissipative braces available on market are used, is discussed.

• Structural Engineering and Mechanics
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• v.88 no.5
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• pp.463-480
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• 2023

The buckling-restrained braced frames with eccentric configurations (BRBF-Es) exhibit stable cyclic behavior and possess a high energy absorption capacity. Additionally, they offer architectural advantages for incorporating openings, much like Eccentrically Braced Frames (EBFs). However, studies have indicated that significant residual drifts occur in this system when subjected to earthquakes at the Maximum Considered Earthquake (MCE) hazard level. Consequently, in order to mitigate these residual drifts, it is recommended to employ self-centering systems alongside the BRBF-E system. In our current research, we propose the utilization of the Direct Displacement-Based Seismic Design method to determine the design base shear for a hybrid system that combines BRBF with an eccentric configuration and a self-centering frame. Furthermore, we present a methodology for designing the individual components of this composite system. To assess the effectiveness of this design approach, we designed 3-, 6-, and 9-story buildings equipped with the BRBF-E-SCF system and developed finite element models. These models were subjected to two sets of ground motions representing the Maximum Considered Earthquake (MCE) and Design Basis Earthquake (DBE) seismic hazard levels. The results of our study reveal that although the combined system requires a higher amount of steel material compared to the BRBF-E system, it substantially reduces residual drift. Furthermore, the combined system demonstrates satisfactory performance in terms of story drift and ductility demand.

• Structural Engineering and Mechanics
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• v.62 no.3
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• pp.281-289
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• 2017

Damping value has considerable influence on the dynamic and seismic behaviors of bridges. However, currently the constant damping ratios that are prescribed by most bridge seismic design codes can't truly represent the complicated damping character of actual structures. In this paper, a cyclic loading experiment was conducted to study the effect of stress amplitude on material damping of concrete to present an analyzing model of the material damping of concrete. Furthermore, based on the fundamental damping of structure measured under ambient vibration, combined with the presented stress-dependent material damping concrete, the seismic response of a bridge pier was calculated. Comparison between the calculated and experiment results verified the validity of the presented damping model. Finally, a modified design and analysis method for bridge was proposed based on stress-dependent damping theory, and a continuous rigid frame bridge was selected as the example to calculate the actual damping values and the dynamic response of the bridge under different earthquake intensities. The calculation results indicated that using the constant damping given by the Chinese seismic design code of bridges would overestimate the energy dissipation capacity of the bridge.

• International Journal of High-Rise Buildings
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• v.3 no.2
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• pp.121-145
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• 2014

The story shear force distributions of most seismic design codes generally reflect the influences of higher vibration modes based on the elastic deformations of structures. However, as the seismic design allows for the plastic behavior of a structure, the story shear force distribution shall be effective after it is yielded due to earthquake excitation. Hence this study conducted numerical analyses on the story shear force distributions of most seismic design codes to find out the characteristics of how a structure is damaged between stories. Analysis results show that the more forces are distributed onto high stories, the lower its concentration is and the more energy is absorbed. From the results, this study proposes the optimum story shear force distribution and its calculation formula that make the damages uniformly distributed onto whole stories. Consequently, the story damage distribution from the optimum calculation formula was considerably more stable than existing seismic design codes.

• Journal of the Earthquake Engineering Society of Korea
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• v.7 no.6
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• pp.25-34
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• 2003

Recently, performance-based analysis/design methods such as the capacity spectrum method and the direct displacement-based design method were developed. In these methods, estimation of energy dissipation capacity of RC structures depends on empirical equations which are not sufficiently accurate, On the other hand, in a recent study, a simplified method for evaluating energy dissipation capacity was developed. In the present study, based on the evaluation method, a new seismic design method for flexure-dominated RC walls was developed. In determination of earthquake load, the proposed design method can address variations of energy dissipation capacity with design parameters such as dimensions and shapes of cross-sections, axial force, and reinforcement ratio and arrangement, The proposed design method was compared with the current performance-based design methods. The applicability of the proposed method was discussed.

• Nuclear Engineering and Technology
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• v.51 no.6
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• pp.1658-1668
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• 2019

Nuclear power generates a large portion of the energy used today and plays an important role in energy development. To ensure safe nuclear power generation, it is essential to conduct an accurate analysis of reactor structural integrity. Accordingly, in this study, a methodology for obtaining accurate structural responses to the combined seismic and reactor coolant loads existing prior to the shutdown of a nuclear reactor is proposed. By applying the proposed analysis method to the reactor vessel internals, it is possible to derive the seismic responses considering the influence of the hydraulic loads present during operation for the first time. The validity of the proposed methodology is confirmed in this research by using the finite element method to conduct seismic and hydraulic load analyses of the advanced APR1400 1400 MWe power reactor, one of the commercial reactors. The structural responses to the combined applied loads are obtained using displacement-based and stress-based superposition methods. The safety of the subject nuclear reactor is then confirmed by analyzing the design margin according to the American Society for Mechanical Engineers (ASME) evaluation criteria, demonstrating the promise of the proposed analysis method.