• 한국방재학회:학술대회논문집
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• 한국방재학회 2010년도 정기 학술발표대회
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• pp.83.2-83.2
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• 2010

Stepped I-beams having increased moment of inertia at one end(singly stepped beam) or both ends(doubly stepped beams) can often be seen in construction of bridges due to material economy and easy fabrication of the section. This paper presents the results of the parametric study of lateral torsional buckling of monosymmetric stepped I-beams with constant depth subjected to equal and opposite end moments applied at the end of the beam. Design recommendations were made based on the finite element results of the models having different combinations of monosymmetric ratio, stepped length ratio, flange thickness ratio and flange width ratio,. The proposed approximation is acceptable based on the parameters given having mostly conservative results. The proposed equation can be further used to extend the study to different loading conditions.

• Wind and Structures
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• 제1권1호
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• pp.77-109
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• 1998

An evaluation and comparison of seven of the world's major building codes and standards is conducted in this study, with specific discussion of their estimations of the alongwind, acrosswind, and torsional response, where applicable, for a given building. The codes and standards highlighted by this study are those of the United States, Japan, Australia, the United Kingdom, Canada, China and Europe. In addition, the responses predicted by using the measured power spectra of the alongwind, acrosswind and torsional responses for several building shapes tested in a wind tunnel are presented and a comparison between the response predicted by wind tunnel data and that estimated by some of the standards is conducted. This study serves not only as a comparison of the response estimates by international codes and standards, but also introduces a new set of wind tunnel data for validation of wind tunnel-based empirical expressions.

• 복합신소재구조학회 논문집
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• 제6권1호
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• pp.30-37
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• 2015

The need to consider torsion in the design of members of a structure has recently been increasing; therefore, many studies on torsion have been carried out. Recent research was focused on the torsional performance of concrete according to the reinforcing materials used. Of particular interest, are torsion studies of beams made of SFRC(steel fiber reinforced concrete), and there has been increasing use of SFRC at construction sites. In contrast, research on the composite PVA-ECC (polyvinyl alcohol-engineered cementitious composite) has only covered its mechanical performance, though it exhibits excellent tensile-strain performance (better than SFRC). Therefore, research on the torsion of concrete beams retrofitted using PVA-ECC is lacking. In this study, the behavior characteristics and performance of reinforced-concrete beams retrofitted by PVA-ECC was investigated experimentally. The experimental results show that the resistance to torsional cracking is increased by PVA-ECC. In addition, the strain on the rebar of the specimen was found to be reduced.

• Journal of Advanced Marine Engineering and Technology
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• 제10권3호
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• pp.94-106
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• 1986

Since the oil shock of '70s the engine makers have developed new types of diesel engine with low fuel consumption. There is an obvious tendency towards the use of poorer quality fuels, such as the residual oil from chemical processes of refinery. The shaft driving generators is also widely adopted on behalf of the auxiliary diesel engines, which are driving on the expensive diesel oil and have high fuel oil consumption rates, and some mania propulsion diesel engines are equipped with reduction gear systems to get better propulsive efficiency by slower propeller revolutions. The propulsion shafting system equipped with the shaft driving generator or the geared diesel engine shafting system has flexible couplings, and it requires extensive investigations of the torsional vibration and torque fluctuation in order to ensure the acceptable operation range in service. The characteristics of misfiring must be especially examined for the high viscosity fuels to be used. Both torsional vibration and fluctuating torque resulted from misfiring, should be examined for thier effects on the flexible coupling and propulsion shafting system. This paper is to investigate and solve the above mentioned problems which must be predicted on the design-stage of marine propulsion shafting system. A computer program is developed to calculate the indicated diagram, fluctating torque and torsional vibration for both normal and misfiring conditions.

• 한국산업융합학회 논문집
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• 제15권1호
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• pp.13-19
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• 2012

Due to a low stiffness of cranktrain and a failure experience from a history within short development time, a viscous torsional vibration damper was applied in order to reduce the torsional vibration and keep the high reliability for the durability of cranktrain system in the direct injection diesel engine. As an improvement of the crankshaft stiffness by increasing the diameter of main and pin journal, a rubber type damper could be considered. In this study, the control factors of rubber damper, the moment of inertia ring, stiffness of damper and damping coefficient of ring, were investigated by DFSS method through the analysis work and the measurement in the real engine condition.

• Wind and Structures
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• 제2권4호
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• pp.267-284
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• 1999

Multiple tuned mass dampers are proposed to suppress the vertical and torsional buffeting and to increase the aerodynamic stability of long-span bridges. Each damper has vertical and torsional frequencies, which are tuned to the corresponding frequencies of the structural modes to suppress the resonant effects. These proposed dampers maintain the advantage of traditional multiple mass dampers, but have the added capability of simultaneously controlling vertical and torsional buffeting responses. The aerodynamic coupling is incorporated into the formulations, allowing this model to effectively increase the critical speed of a bridge for either single-degree-of-freedom flutter or coupled flutter. The reduction of dynamic response and the increase of the critical speed through the attachment of the proposed dampers to the bridge are also discussed. Through a parametric analysis, the characteristics of the multiple tuned mass dampers are studied and the design parameters - including mass, damping, frequency bandwidth, and total number of dampers - are proposed. The results indicate that the proposed dampers effectively suppress the vertical and the torsional buffeting and increase the structural stability. Moreover, these tuned mass dampers, designed within the recommended parameters, are not only more effective but also more robust than a single TMD against wind-induced vibration.

• Computers and Concrete
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• 제9권6호
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• pp.469-486
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• 2012

This paper presents Neuro-Fuzzy (NF) based empirical modelling of torsional strength of RC beams for the first time in literature. The proposed model is based on fuzzy rules. The experimental database used for NF modelling is collected from the literature consisting of 76 RC beam tests. The input variables in the developed rule based on NF model are cross-sectional area of beams, dimensions of closed stirrups, spacing of stirrups, cross-sectional area of one-leg of closed stirrup, yield strength of stirrup and longitudinal reinforcement, steel ratio of stirrups, steel ratio of longitudinal reinforcement and concrete compressive strength. According to the selected variables, the formulated NFs were trained by using 60 of the 76 sample beams. Then, the method was tested with the other 16 sample beams. The accuracy rates were found to be about 96% for total set. The performance of accuracy of proposed NF model is furthermore compared with existing design codes by using the same database and found to be by far more accurate. The use of NF provided an alternative way for estimating the torsional strength of RC beams. The outcomes of this study are quite satisfactory which may serve NF approach to be widely used in further applications in the field of reinforced concrete structures.

• 한국지능시스템학회:학술대회논문집
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• 한국지능시스템학회 2008년도 춘계학술대회 학술발표회 논문집
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• pp.205-208
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• 2008

이 논문은 파이프의 결함을 진단하기 위해서 파이프에 유도 비틀림파를 가진하고 수신하는 개선된 방법을 제시한다. 기존에 니켈 스트립을 파이프에 부착하고 잔류자계를 이용한 Mode 선택 가진 방법에서 나타난 잔류자계의 정량화 문제점, 다른 모드가 동시에 가진되는 문제점 등을 해결하기 위해서 새로운 형태의 Crossed Coils센서를 제안한다. 제안된 센서를 통해 모드 선택이 가능함을 확인하였고, 차후 모드분석을 통하여 Torsional Mode의 최적 가진 조건을 찾을 수 있음을 보인다.

• 한국정밀공학회지
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• 제26권12호
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• pp.94-101
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• 2009

In diesel engines, it is inevitable that the torsional vibration is produced by the fluctuation of engine torque. Therefore, it is necessary to establish preventive measures to diminish the torsional vibration. The sleeve spring type damper is one of the preventive measures for reducing the torsional vibration. In this study, 2-roll bending process was proposed to manufacture sleeve spring; The program to calculate the initial radius including springback effect was developed and the FEA method to analyze elasto-plastic problem was verified through analysis of 90 degree bending process. The elasto-plastic analysis of 2-roll bending process was carried out by the FEA method verified to set a new criterion, and the new process design parameter(contact angle) in the 2-roll bending process was proposed.

• 한국지능시스템학회논문지
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• 제18권6호
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• pp.856-862
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• 2008

이 논문은 파이프의 결함을 진단하기 위해서 파이프에 유도 비틀림파를 가진하고 수신하는 개선된 방법을 제시한다 기존에 니켈 스트립을 파이프에 부착하고 잔류자계를 이용한 Mode 선택 가진 방법에서 나타난 잔류자계의 정량화 문제점, 다른 모드가 동시에 가진되는 문제점 등을 해결하기 위해서 새로운 형태의 Crossed Coils센서를 제안한다. 제안된 센서를 통해 모드 선택이 가능함을 확인하였고, 차후 모드분석을 통하여 Torsional Mode의 최적 가진 조건을 찾을 수 있음을 보인다.