• 한국소음진동공학회논문집
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• 제26권4호
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• pp.436-442
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• 2016

This paper presents the torsional vibration isolation performance evaluation of a centrifugal pendulum absorbers (CPAs) that has a continuously varying resonance frequencies proportional to engine firing (excitation) order. CPAs are commonly used to suppress torsional vibrations in rotating machinery and internal combustion engines. In this study, they are employed on the current spring type torsional damper inside a torque converter of automotive vehicle. To evaluate the effectiveness of designed resonance tuning order, the torsional vibration transmissibility based on torque measurements with respect to different engine firing orders is experimentally measured with a lower-inertia dynamometer. The torsional vibration transmissibility with respect to different frequencies with engine order of 2 is also evaluated. It has been demonstrated that the significant vibration reduction over operational frequency range of interest can be achieved by attaching simple pendulums. Future research direction includes the study on theoretical analysis, improved design of pendulum etc.

• International Journal of Concrete Structures and Materials
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• 제11권1호
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• pp.45-58
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• 2017

Recent investigations have pointed out that current code provisions specifying that the stiffness of reinforced concrete elements is strength independent, and therefore can be estimated prior to any strength assignment, is incorrect. A strength allocation strategy, suitable for preliminary structural design of medium height wall-frame dual systems, is presented for allocating strength in such buildings and estimating the dependable rigidities. The design process may be implemented by either the approximate continuous approach or the stiffness matrix method. It is based on the concept of the inelastic equivalent single-degree-of-freedom system which, the last few years, has been used to implement the performance based seismic design. The aforesaid strategy may also be used to determine structural configurations of minimum rotation distortion. It is shown that when the location of the modal centre of rigidity, as described in author's recent papers, is within a close distance from the mass axis the torsional response is mitigated. The methodology is illustrated in ten story building configurations, whose torsional response is examined under the ground motion of Kobe 1995, component KJM000.

• 한국강구조학회 논문집
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• 제29권5호
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• pp.369-376
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• 2017

본 논문은 ASCE 7-10를 적용한 비틀림 비정형 철골 모멘트 골조의 설계 및 평가를 수행한 동반연구(I 내진설계)의 후속 연구이다. 본 연구에서는 철골 모멘트 골조의 비틀림 비정형 발생 여부와 ASCE 7-10 설계 요구조건의 적용 여부에 따라 내진성능평가를 수행하였다. 그 결과, ASCE 7-10의 비정형 내진설계 요구조건을 적용한 철골 모멘트 골조의 경우 붕괴확률이 매우 낮고 상당히 보수적인 설계 결과를 나타냈으며, 본 연구에서는 비틀림 비정형 구조물의 합리적인 설계를 위해 개선된 설계 방법을 제시하였다. 제안된 방법으로 설계된 비틀림 비정형 철골 모멘트 골조의 붕괴확률은 기존의 방법으로 설계된 구조물의 붕괴확률을 보다 크지만 ASCE 7-10의 붕괴확률 요구 조건을 만족하였다.

• 한국지진공학회논문집
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• 제17권5호
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• pp.237-243
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• 2013

In the Korean Building Code (KBC), the Design Eccentricity involves the torsional amplification factor (TAF), and the inherent and accidental eccentricities. When a structure of less than 6-stories and assigned to seismic design category C or D is designed using equivalent static analysis method, both KBC-2006 and KBC-2009 use the TAF but apply different calculation methods for the of design eccentricity. The design eccentricity in KBC-2006 is calculated by multiplying the sum of inherent eccentricity and accidental eccentricity at each level by a TAF but that in KBC-2009 is calculated by multiplying only the accidental eccentricity by a TAF. In this paper, the damage indices of a building with planar structural irregularity designed by different design eccentricities are compared and the relationship between the earthquake damage and design eccentricity of the building is evaluated. On the basis of this study, the increment of design eccentricity results in the decrement of final eccentricity and global damage index of structure. It is observed that design eccentricity in KBC-2006 reduces the vulnerability of torsional irregular building compared to design eccentricity in KBC-2009.

• 한국전산구조공학회논문집
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• 제15권1호
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• pp.117-126
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• 2002

본 논문에서는 횡비틀림좌굴을 고려하는 2차 소성힌지해석법을 이용하여 3차원 강뼈대구조물의 설계기법을 개발하였다. 본 해석은 구조시스템 및 개별부재의 재료적 기하학적 비선형 거동을 고려한다. 더욱이, 종래의 2차 소성힌지해석에서 횡비틀림좌굴효과에 의한 휨강도 감소효과를 고려하지 못한 문제를 해결하였다. 강뼈대구조물의 잔류응력과 휨에 의한 비선형성 및 기하학적 불완전성에 의한 점진적인 소성화효과를 고려하는 효율적인 방법을 기술하였다. 횡비틀림좌굴효과를 고려하기 위하여 비지지장 및 단면 형상으로 구성되는 침강도 감소모델을 사용하였다. 개발된 2차 소성힌지해석법을 LRFD 설계방법과 비교함으로서 검증하였다. 예제해석을 통하여 횡비틀림좌굴효과는 2차 소성힌지해석법에 고려해야 할 중요한 요소임을 알 수 있었다. 본 해석은 실제 설계에 활용할 수 있는 효율적이고 신뢰성 있는 방법이다.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2006년도 추계학술대회논문집
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• pp.776-785
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• 2006

Ship builder's requirement for a higher power output rating has lead to the development of super large two stroke low speed diesel engines. Usually a large-sized bore ranging from 8-14 cylinders, this engine group is capable of delivering power output of more than 100,000 bhp at maximum continuous rating. Other positive aspects of this engine type include higher thermal efficiency, reliability, durability and mobility. This all playa vital role in meeting the propulsion requirement of vessels, specifically for large container ships, of which speed is a primary concern to become more competitive. Consequently, this also resulted in the modification of engine parameters and new component designs to meet the consequential higher mean effective pressure and higher maximum combustion pressure. Even though the fundamental excitation mechanism unchanged, torsional vibration stresses in the propulsion shafting are subsequently perceived to be higher. As such, one important viewpoint in the initial engine design is the resulting vibration characteristic expected to prevail on the propulsion shafting system(PSS). This paper investigated the torsional vibration characteristics of these super large engines. For the two node torsional vibration with a nodal point on the crankshaft, a tuning damper is necessary to reduce the torsional stresses on the crankshaft. Hence, the tuning torsional vibration damper design and compatibility to the shafting system was similarly reviewed and analyzed.

• 한국강구조학회 논문집
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• 제29권5호
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• pp.361-368
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• 2017

지진하중 하에서 구조물의 강성중심과 질량중심이 차이가 날 경우에 편심이 발생하여 비틀림을 유발한다. ASCE 7-10에서는 이를 비틀림 비정형으로 규정하고 있으며, 비틀림 비정형 구조물의 내진설계를 위한 요구사항들을 제시하고 있다. 본 연구에서는 편심이 다른 3층, 9층 철골 모멘트 골조의 3차원 시간이력해석 결과를 기반으로 비틀림 비정형 철골조에 적용되는 내진설계기준의 요구조건에 대한 영향을 평가하였다. 그 결과, 편심이 증가할수록 적절히 설계된 구조물의 성능이 우수하며 소성힌지의 분포가 정형 구조물과 유사한 것으로 나타냈다.

• Structural Engineering and Mechanics
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• 제67권6호
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• pp.671-682
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• 2018

The effect of earthquake induced torsion, due to mass eccentricities, is investigated with the objective of providing practical design guidelines for minimizing the torsional response of building structures. Current code provisions recommend performing three dimensional static or dynamic analyses, which involve shifting the centers of the floor masses from their nominal positions to what is called an accidental eccentricity. This procedure however may significantly increase the design cost of multistory buildings, due to the numerous possible spatial combinations of mass eccentricities and it is doubtful whether such a cost would be justifiable. This paper addresses this issue on a theoretical basis and investigates the torsional response of asymmetric multistory buildings in relation to their behavior when all floor masses lie on the same vertical line. This approach provides an insight on the overall seismic response of buildings and reveals how the torsional response of a structure is influenced by an arbitrary spatial combination of mass eccentricities. It also provides practical guidelines of how a structural configuration may be designed to sustain minor torsion, which is the main objective of any practicing engineer. A parametric study is presented on 9-story common building types having a mixed-type lateral load resisting system (frames, walls, coupled wall bents) and representative heightwise variations of accidental eccentricities.

• 한국소음진동공학회논문집
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• 제15권4호
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• pp.499-505
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• 2005

In this paper, a new type of pi+ezoelectric stepping motor is designed, manufactured and tested. This motor is composed of piezoelectric torsional actuator and a pair of one-way clutch bearings. The torsional actuator consists of 16-polygonal tube of piezoceramic that can produce an angular displacement associated with shear mode. One-way clutch bearing converts oscillation of torsional actuator into a continuous stepping rotation. The proposed stepping motor does not require any conversion mechanism for stepping motion like any other motors. In the design process, the shear resonance mode of piezoelectric actuator is analyzed by using a commercial finite element analysis program, and the performance of the fabricated torsional actuator is measured. $0.124^{\circ}$ of maximum angular displacement is measured in square wave excitation on the actuator only. The stepping motor is manufactured by assembling a pair of one-way clutch bearings and the torsional actuator. The maximum rotation speed of 72rpm and the blocking torque of 3.136 mNm are measured at 3540 Hz and 100V/mm. Once the proposed piezoelectric stepping motor is miniaturized, it can be used for many compact and precise moving applications.

• 대한조선학회 특별논문집
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• 대한조선학회 2008년도 특별논문집
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• pp.54-61
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• 2008

With the development of computer program in calculation for torsional vibration of ship's propulsion shafting it has become possible to calculate all order's vibratory amplitude, vibratory torque, vibratory stress and synthesis value at all concerned revolutions by way of solving the vibratory equation directly. Though this kind of propulsion shafting vibration calculation method makes it possible to get generalized and precise result of calculation, the unexpected critical crankshaft torsional vibration has still appeared in maneuvering range of the engine. A close investigation has been carried out to find out the cause for the 2-node propulsion shafting torsional vibration of the crankshaft that exceeded the limitation value near the MCR 104rpm on the sea trial of the recently delivered 6000TEU class container vessel from HHIC. In conclusion, as the latest super-output engine with heavy crankshaft and propeller mass seems to be liable to 2-node torsional vibration of crankshaft, it is recommend that, in the design stage of propulsion shafting, its torsional vibration condition must be more carefully checked.