• 한국지진공학회논문집
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• 제23권3호
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• pp.159-167
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• 2019

2016 Gyeongju and 2017 Pohang earthquakes led Koreans to acknowledge that the Korean peninsula is not an earthquake-free zone anymore. Among various buildings crucial to after-shock recovery, general hospital buildings, especially existing old ones, are very significant so seismic retrofitting of those must be an important issue. Self-centering energy dissipative(SCED) brace is one of retrofitting methods, which consists of tendon with restoring force and friction device capable of dissipating seismic energy. The strength of the SCED brace is that the tendon forces a structure to go back to the original position, which means residual drift can be negligible. The residual drift is a very important parameter to determine usableness of general hospitals after shock. To the contrary, buckling-restrained braces(BRB) are also a very effective way to retrofit because they can resist both compressive and tensile, but residual drift may exist when the steel core yields. On this background, the seismic retrofitting effect of general hospitals reinforced with SCED braces was investigated and compared to that of the BRD in this study. As a result, although the floor acceleration cannot be reduced, the story drift and residual drift, and the shear demand of walls significantly decreased. Consequently, seismic retrofitting by SCED braces are very effective for domestic low-rise general hospitals.

• Steel and Composite Structures
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• 제27권5호
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• pp.623-632
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• 2018

Performance-Based Plastic Design (PBPD) method has been recently developed to evaluate the behavior of structures in different performance levels. The PBPD method utilizes a base shear force and a lateral load pattern that are estimated based on energy and yielding mechanism concepts. Using of current lateral force pattern results in weak structural members in upper stories of a structure so that the values of the story drift in these stories are larger than the target drift, particularly in high-rise buildings. Therefore, such distribution requires modifications to overcome this drawback. This paper proposes a modified lateral load pattern for steel Eccentrically Braced Frames (EBFs) based on parametric study. In order to achieve the modified load pattern, a group of 26 EBFs has been analyzed under a set of 20 earthquake ground motions. Additionally, results of nonlinear dynamic analyses of EBFs have been post-processed by nonlinear regression analysis in order to derive the new load pattern. To prove the efficiency of present study, three EBFs as examples were designed by modified pattern and current PBPD distribution. Inelastic dynamic analyses results showed that the story drifts using modified lateral load pattern were well within the target values in comparison with current pattern in PBPD, particularly where the effect of the height is significant. The modified load pattern reduces the possibility of underdesigning in upper levels and overdesigning in lower levels of the frames.

• 한국공간구조학회논문집
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• 제17권4호
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• pp.115-122
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• 2017

In this study, performance based seismic design was performed on the shear wall structural system and the beam-column system as a variable general rebar and seismic rebar, and comparing the capacity of the two models of each system. From nonlinear analyses, the capacity of the shear wall structural system applying seismic rebar has shown a stable behavior after the maximum strength, but there is little difference. Furthermore, both models showed similar capacity between story drift and story shear force and capacity of members. These results are attributed to the fact that the seismic rebar, which is highly ductile under the seismic load applied to the target structure, does not render sufficient capacity.

• Steel and Composite Structures
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• 제22권5호
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• pp.1055-1071
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• 2016

The paper presents an innovative steel moment frame with the replaceable reinforced concrete wall panel (SRW) structural system, in which the replaceable concrete wall can play a role to increase the overall lateral stiffness of the frame system. Two full scale specimens composed of the steel frames and the replaceable reinforced concrete wall panels were tested under the cyclic horizontal load. The failure mode, load-displacement response, deformability, and the energy dissipation capacity of SRW specimens were investigated. Test results show that the two-stage failure mode is characterized by the sequential failure process of the replaceable RC wall panel and the steel moment frame. It can be found that the replaceable RC wall panels damage at the lateral drift ratio greater than 0.5%. After the replacement of a new RC wall panel, the new specimen maintained the similar capacity of resisting lateral load as the previous one. The decrease of the bearing capacity was presented between the two stages because of the connection failure on the top of the replaceable RC wall panel. With the increase of the lateral drift, the percentage of the lateral force and the overturning moment resisted by the wall panel decreased for the reason of the reduction of its lateral stiffness. After the failure of the wall panel, the steel moment frame shared almost all the lateral force and the overturning moment.

• 대한조선학회지
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• 제20권1호
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• pp.47-58
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• 1983

A study is made, in the framework of linear potential theory, to investigate the hydrodynamic characteristics of two-dimensional wave-energy absorbers as like the Salter's duck and an oscillating cam with Lewis-form section, which undergo uncoupled heaving and rolling motions in an incident linear gravity wave in deep water. Wave energy is supposed to be extracted by a linearly damped generator with an spring. Some well-known formulae in ship hydrodynamics such as Haskind-Newman relation and Bessho-Newman relation are utilized in forms of Kochin functions to derived expressions for efficiency, breaking effect and drift force of the absorber. Maximum ideal efficiency of 100% can be arrived at an prescribed tuning frequency. Coupling effect is also examined to assess the detrimental effect of sway on efficiency. From numerical calculations for both types of two-dimensional devices it may be concluded that a wave-energy absorber functions at the same time as a wave breaker and that the drift force acting on the device becomes smaller when it absorbs wave energy than as it oscillates freely. Finally the study is extended to an infinite array system, equivalent to a body in a canal, to show that all incident wave energy can be absorbed regardless of the absorber's size, only if the optimum space and the optimum condition of control are realized.

• 한국항해항만학회지
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• 제27권1호
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• pp.55-61
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• 2003

계류된 선박의 시뮬레이션을 위해 조종방정식을 사용하였고, 파 중의 선박에 가해지는 파강제력은 3차원 특이점 분포법에서 얻어진 주파수 전달함수로부터 시간영역해석법을 적용하였다. 운동을 유발하는 입사파의 주기와 동일한 선형 파강제력과 성분파 주파수의 차이에 기인하는 장주기 표류력을 외력항에 고려하였다. 규칙파와 불규칙 중에서의 선박의 거동을 비교하여 계류 중 선박에 발생할 수 있는 SLEW MOTION에 불규칙파 및 비선형 파강제력이 미치는 영향을 고찰하였다.

• Journal of Power Electronics
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• 제15권2호
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• pp.419-430
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• 2015

Flux estimation is a significant foundation of high-performance control for DC-excited synchronous motor. For almost all flux estimators, such as the flux estimator based on phase locked loop (PLL), DC drift causes fluctuations in flux magnitude. Furthermore, significant dynamic error may be introduced at transient conditions. To overcome these problems, this paper proposes an improved flux estimator for the PLL-based algorithm. Filters based on the generalized integrator are used to avoid flux fluctuation problems caused by the DC drift at the back electromotive force. Programmable low-pass filters are employed to improve the dynamic performance of the flux estimator, and the cutoff frequency of the filter is determined by the dynamic factor. The algorithm is verified by a 960V/1.6MW industrial prototype. Simulation and experimental results show that the proposed estimator can estimate the flux more accurately than the PLL-based algorithm in a cycloconverter-fed DC-excited synchronous machine vector control system.

• Earthquakes and Structures
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• 제18권6호
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• pp.667-675
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• 2020

The current study compares the effect of structure-soil-structure interaction (SSSI) on the dynamic responses of adjacent buildings and isolated structures including soil-structure interaction (SSI) with the responses of fixed-base structures. Structural responses such as the relative acceleration, displacement, drift and shear force were considered under earthquake ground motion excitation. For this purpose, 5-, 10- and 15-story structures with 2-bay moment resisting frames resting on shallow foundations were modeled as a group of buildings in soft soil media. Viscous lateral boundaries and interface elements were applied to the soil model to simulate semi-infinite soil media, frictional contact and probable slip under seismic excitation. The direct method was employed for fully nonlinear time-history dynamic analysis in OpenSees using 3D finite element soil-structure models with different building positions. The results showed that the responses of the grouped structures were strongly influenced by the adjacent structures. The responses were as much as 4 times greater for drift and 2.3 times greater for shear force than the responses of fixed-base models.

• 수산해양기술연구
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• 제58권4호
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• pp.299-309
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• 2022

Among the fishing vessels operating in the coastal waters, jigging fishing vessels were considered representative vessels engaged only by wind, sea, tide, and external force. Then, a fishing vessel with a length of shorter than 10 m from July 1, 2018 to August 5, 2019 was studied to obtain a drift prediction model by multiple regression analysis. In the correlation analysis between variables for leeway of speed and direction, the speed and direction of tidal seem to be the most affected in coastal waters. Therefore, it should be considered an explanatory variable when conducting drift tests. As a result of multiple regression analysis on the predicted equations of leeway speed and direction due to the external force on the drift of the fishing vessel, p < 0.000 was considered significant in the F-test, but the coefficient of determination was 55.2% and 37.8%. The effect on the predicted leeway speed was in the order of the tidal speed and current speed. In addition, the impact on the predicted leeway direction was in the order of the tidal speed and current speed. ŷ(m/s) = - 0.0011(x1) + 0.9206(x2) + 0.0001(x3) + 0.0002(x4) + 0.0050(x5) + 0.0529(x6) + 0.2457 ŷ(degree) = 0.6672(x1) + 93.1699(x2) + 0.0585(x3) - 0.0244(x4) - 1.2217(x5) + 4.6378(x6) - 0.0837

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 2006년도 정기 학술대회 논문집
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• pp.421-426
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• 2006

To examine the behaviors of traditional wooden structural frame in Korea in direction of beam, an experimental study was performed. The interior frame of Daewoongjeon of Bongjeongsa was selected as a model, which has two short exterior columns and one high inside column. The experimental frame has 1/2 scale and lateral forces are applied at high inside column by using drift control. The vertical gravity loads are applied on the frame. From the results of experiment it was shown that the stiffness and lateral capacity of the frame was increased when vertical loads are applied and the force-drift relationship in positive load direction was not same as in negative load direction. And push-over analysis are performed by using macro model in which the rotational and shear springs which were derived from the another experiments of subassemblies were used. The numerical analysis with macro model showed a good correspondence with the experiment within 2% story drift.