• Earthquakes and Structures
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• v.9 no.6
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• pp.1133-1152
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• 2015

A frequency-domain method is developed for evaluating the earthquake input energy to two building structures connected by viscous dampers. It is shown that the earthquake input energies to respective building structures and viscous connecting dampers can be defined as works done by the boundary forces between the subsystems on their corresponding displacements. It is demonstrated that the proposed energy transfer function is very useful for clear understanding of dependence of energy consumption ratios in respective buildings and connecting viscous dampers on their properties. It can be shown that the area of the energy transfer function for the total system is constant regardless of natural period and damping ratio because the constant Fourier amplitude of the input acceleration, relating directly the area of the energy transfer function to the input energy, indicates the Dirac delta function and only an initial velocity (kinetic energy) is given in this case. Owing to the constant area property of the energy transfer functions, the total input energy to the overall system including both buildings and connecting viscous dampers is approximately constant regardless of the quantity of connecting viscous dampers. This property leads to an advantageous feature that, if the energy consumption in the connecting viscous dampers increases, the input energies to the buildings can be reduced drastically. For the worst case analysis, critical excitation problems with respect to the impulse interval for double impulse (simplification of pulse-type impulsive ground motion) and multiple impulses (simplification of long-duration ground motion) are considered and their solutions are provided.

• Journal of the Earthquake Engineering Society of Korea
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• v.13 no.3
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• pp.39-50
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• 2009

In this paper, a method for reducing seismic responses of adjacent buildings is studied that involves connecting two buildings with energy-dissipating devices, such as MR dampers. For the vibration control of the adjacent buildings, a fuzzy control technique with semi-active MR dampers is proposed. A fuzzy controller, which can appropriately modulate the damping forces by controlling the input voltage in real time, is designed according to the proposed method. To verify the validity of the proposed method, numerical simulations are performed. In the numerical simulations, historical earthquake records with diverse frequency contents and different peak values are used. For the purpose of comparison, an uncontrolled system, a passive control system and a semi-active fuzzy control system are considered. The comparative results prove the effectiveness of the proposed control technique, i.e. the numerical results show that the fuzzy controlled semi-active MR dampers can effectively reduce the earthquake responses of the adjacent structures.

• Journal of Korean Association for Spatial Structures
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• v.7 no.1 s.23
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• pp.45-53
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• 2007

Recently, high-rise base isolated building structures with shear keys are often constructed in Japan which frequently occurs earthquakes. High-rise buildings are less damaged because those buildings have longer natural period than md or low rise buildings. The shear key is device that prevents the base isolators operating by the wind loads not by the earthquake loads. In case of big base shear force acts on the shear keys by earthquake, this device is broken and base isolator is operated. Therefore, seismic intensities play a role in acting on the shear keys. If wind loads are hither than the earthquake loads, the shear keys designed by wind loads are not operated in earthquakes. So, the requirements of shear keys in high-rise base isolated building structures must be examined in Korea with moderate seismic legions. In this study shear keys are applied with 5 and 15 stories base isolated building structures and investigated their dynamic responses to original and 1/2 scale downed El Centre NS(1940) ground motions. The results show that the yield shear forces of the shear keys affect significantly the dynamic behavior of base isolated building structures

• Journal of the Earthquake Engineering Society of Korea
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• v.25 no.3
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• pp.111-119
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• 2021

A shear wall is a structural member designed to effectively resist in-plane lateral forces, such as strong winds and earthquakes. Due to its efficiency and stability, shear walls are often installed in residential buildings and essential facilities such as nuclear power plants. In this research, to predict the results of the shaking table test of the three-story shear wall RC structure hosted by the Korea Atomic Energy Research Institute, three types of numerical modeling techniques are proposed: Preliminary, Calibrated 1, and Calibrated 2 models, in order of improvement. For the proposed models, an earthquake of the 2016 Gyeongju, South Korea (peak ground acceleration of 0.28 g) and its amplified earthquake (peak ground acceleration of 0.50 g) are input. The response spectra of the measuring points are obtained by numerical analysis. Good agreement is observed in the comparisons between the experiment results and the simulation conducted on the finally adopted numerical model, Calibrated 2. In the process of improving the model, this paper investigates the influences of the mode shape, material properties, and boundary conditions on the structure's seismic behavior.

• Journal of the Earthquake Engineering Society of Korea
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• v.27 no.2
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• pp.77-82
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• 2023

The structural analysis module is an essential part of any integrated structural system. Diverse integrated systems today require, from the analysis module, efficient real-time responses to real-time input such as earthquake signals, extreme weather-related forces, and man-made accidents. An integrated system may also be for the entire life span of a civil structure conceived during the initial conception, developed throughout various design stages, effectively used in construction, and utilized during usage and maintenance. All these integrated systems' essential part is the structural analysis module, which must be automated and computationally efficient so that responses may be almost immediate. The finite element method is often used for structural analysis, and for automation, many effective finite element meshes must be automatically generated for a given analysis. A computationally efficient finite element mesh generation scheme based on the r-h method of mesh refinement using strain deviations from the values at the Gauss points as error estimates from the previous mesh is described. Shape factors are used to sort out overly distorted elements. A standard cantilever beam analyzed by four-node plane stress elements is used as an example to show the effectiveness of the automated algorithm for a time-domain dynamic analysis. Although recent developments in computer hardware and software have made many new applications in integrated structural systems possible, structural analysis still needs to be executed efficiently in real-time. The algorithm applies to diverse integrated systems, including nonlinear analyses and general dynamic problems in earthquake engineering.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• v.1
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• pp.47-52
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• 2006

Recent warnings indicate that there is a potential risk of massive earthquake in Japan within 30 years. These earthquakes could produce large-scale tsunamis. Tsunamis are very powerful and can be traveled thousands of miles and caused damage in many countries. Consideration of the effect of tsunami to the moored ship is very important because it brings the loss of life and vast property damage. In this paper, the numerical simulation procedure to analyze the motions of a moored ship due to the observed waves of tsunami, Tokachi-off earthquake tsunami profile in northern Pacific coasts of Japan on September 26 in 2003. And the effects on the motions and mooring loads are investigated by numerical simulation. Numerical simulations consist of hydrodynamic analyses in a frequency domain and ship motion analyses in a time domain as the motions of moored ships are examined. As the process begins, the hydrodynamic and waveexciting forces for moored ships must be calculated. Ship motions and mooring forces can then be calculated by solving the equations of motion. In order to investigate the safety evaluation on the motions of moored ship by tsunami attack, we applied a numerical simulation procedure to a 135,000m3 LNG carrier moored at an offshore sea berth.

• Journal of the Korean Geotechnical Society
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• v.37 no.12
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• pp.89-105
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• 2021

In this paper, feasibility study was carried out to evaluate necessity of seismic design of earth retaining structures in a deep excavation. Dynamic behavior of retaining system was analyzed using FLAC, a finite difference analysis program. It was shown that maximum bending moments of retaining walls and axial forces of supports were increased up to 98% and 87% during earthquake, respectively, compared to final excavation step, which indicates that dynamic earth pressure has a large effect on a retaining system. The stability of retaining system designed according to current design specifications was evaluated using structural forces obtained by numerical analysis, and effect of earthquake loading on structural design was analyzed.

• Earthquakes and Structures
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• v.20 no.1
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• pp.1-12
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• 2021

The occurrence of progressive collapse induced by the removal of the vertical load-bearing element in the structure, because of fire or earthquake, has been a significant challenge between structural engineers. Progressive collapse is defined as the complete failure or failure of a part of the structure, initiating with a local rupture in a part of the building and can threaten the stability of the structure. In the current study, the behavior of the structures equipped with a cylindrical friction damper, when the vertical load-bearing elements are eliminated, is considered in two cases: 1-The load-bearing element is removed under the gravity load, and 2-The load-bearing element is removed due to the earthquake lateral forces. In order to obtain a generalized result in the seismic case, 22 pair motions presented in FEMA p 695 are applied to the structures. The study has been conducted using the vertical push down analysis for the case (1), and the nonlinear time-history analysis for the second case using OpenSEES software for 5,10, and 15-story steel frames. Results indicate that, in the first case, the load coefficient, and accordingly the strength of the structure equipped with cylindrical friction dampers are increased considerably. Furthermore, the results from the second case demonstrate that the displacements, and consequently the forces imposed to the structure in the buildings equipped with the cylindrical friction damper substantially was reduced. An optimum slip load is defined in the friction dampers, which permits the damper to start its frictional damping from this threshold load. Therefore, the optimum slip load of the damper is calculated and discussed for both cases.

• Magazine of the Korea Concrete Institute
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• v.4 no.1
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• pp.135-145
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• 1992

With the increasing tendency to construct high rise reinforced concrete building~i, it is required to use high strength materIals, smaller member sections, and larger reinforcing bars, I t is generally recognized that under severe seismic loads beam column jomts may become more critical structural components than other structural elements. In a ductile momentresistmg reinforced concrete frame, the connection of bearncolumn must be capable of resistll1g the large lateral forces caused by seismic actions, The purpose of this experimental study is to evaluate and ll1vestigate the earthquake resistant perform ance of beam-colurrm subassemblies constructed with high-strength concrete cast by the concrete of com¬pressive strength of 700kg / cm2 subjected to reversed cyclic loadings. New approaches for moving the plastic hinging zone away from the column face and preventing the di¬agonal crack in the joint region are adopted to advance the earthquake-resistant performance of beam-column subassemblies using high-strengh concrete under severe earthquake-type loading. Exper¬imental results indicate that the modified new details which are introduced by intermediate reinforcement in the beam over a specific beam length adjacent to the joint are able to attain the stable hysteretic behavior and the enhancement of earthquake-resistant performance. Keywords: high strength concrete: beam-column Joints; seirnic loads(reversed cyclic loading) : earth¬quake-resistant performance; plastic hinge zone: diagonal crack: intermediate reinforce¬ment ; closed strirrup: hysteretic behavior: enhancement .

• Journal of the Earthquake Engineering Society of Korea
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• v.2 no.4
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• pp.63-72
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• 1998

This study is to develop a technique for micro-vibration analysis and control of concrete slabs to fulfil the vibration criteria for working environments. The proposed technique is for determining the unknown forces from accelerance of two concerned points and the micro-vibration analysis and control of concrete slabs are then validated by numerical model and structural tests. And it is recommended that the natural frequency of structures for micro-vibration control design should be above 25 Hz~30 Hz, and 1.5 times forcing frequency in case of 3~5% structural damping ratio of concrete structures.