• Earthquakes and Structures
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• 제4권1호
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• pp.11-39
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• 2013

Since slender structures such as utility poles, radio masts, and chimneys, are essentially statically determinate structures, they often collapse during earthquakes. Although vibration control is the most logical method for improving the earthquake resistance of such structures, there are many practical problems with its implementation due to their very long natural vibration period. This paper proposes a new vibration control device to effectively prevent the collapse of slender structures subjected to strong earthquakes. The device consists of a pendulum, an elastic restraint and a lever, and is designed such that when it is attached to a slender structure, the second vibration mode of the structure corresponds to the first vibration mode of the same structure without the device attached. This is highly effective in causing the transverse motions of the device and the structure to oppose each other and so reduce the overall transverse vibration during an earthquake. In the present paper, the effectiveness of the vibration control device is first evaluated based on laboratory experiments and numerical studies. An example of applying the device to a tall chimney is then simulated. A new dynamic analytical method for slender structures with abrupt rigidity variations is then proposed.

• 대한토목학회논문집
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• 제6권1호
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• pp.35-41
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• 1986

본 논문에서는 점탄성지반의 지반-구조물 시스템을 해석하는 복합모형기법이 연구되었다. 복합모형은 지반-구조물 시스템을 구조물과 구조물주위의 반구형태의 지반으로 구성된 내부영역과 반구바깥부분의 외부영역으로 나누어 해석하는 방법으로서, 내부영역은 유한요소로 모형화하고 외부영역은 주파수 종속 임피던스로 나타낸다. 점탄성지반에 대한 외부영역 임피던스는 탄성지반에 대하여 구한 임피던스함수에 Hysteretic damping항을 더해주는 방법을 사용하였으며, 이에 대한 검증은 점탄성지반의 강체원형판에 대한 임피던스를 이론적인 값과 비교함으로써 수행되었다. 예제해석은 대형굴뚝에 대하여 수행되었으며, 해석결과를 자주 사용되는 다른 방법에 의한 결과와 비교 검토하였다.

• 국제초고층학회논문집
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• 제4권1호
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• pp.9-25
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• 2015

Field measurements of various structures have been conducted for many purposes. Measurement data obtained by field measurement is very useful to determine vibration characteristics including dynamic characteristics such as the damping ratio, natural frequency, and mode shape of a structure. In addition, results of field measurements and modal identification can be used for modal updating of FEM analysis, for checking the efficiency of damping devices and so on. This paper shows some examples of field measurements and modal identification for structural health monitoring. As the first example, changes of dynamic characteristics of a 15-story office building in four construction stages from the foundation stage to completion are described. The dynamic characteristics of each construction stage were modeled as accurately as possible by FEM, and the stiffness of the main structural frame was evaluated and the FEM results were compared with measurements performed on non-load-bearing elements. Simple FEM modal updating was also applied. As the next example, full-scale measurements were also carried out on a high-rise chimney, and the efficiency of the tuned mass damper was investigated by using two kinds of modal identification techniques. Good correspondence was shown with vibration characteristics obtained by the 2DOF-RD technique and the Frequency Domain Decomposition method. As the last example, the wind-induced response using RTK-GPS and the feasibility of hybrid use of FEM analysis and RTK-GPS for confirming the integrity of structures during strong typhoons were shown. The member stresses obtained by hybrid use of FEM analysis and RTK-GPS were close to the member stresses measured by strain gauges.