• KSCE Journal of Civil and Environmental Engineering Research
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• v.28 no.4A
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• pp.537-548
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• 2008

Recently, the prestressed unbonded concrete structures are increasingly being built. The mechanical behavior of prestressed concrete beams with unbonded tendon is different from that of normal bonded PSC beams in that the increment of tendon stress was derived by whole member behavior. The purpose of the present paper is therefore to evaluate the flexural behavior and to propose the equation of ultimate tendon stress by performing static flexural test according to span/depth, concrete compression strength, reinforcement ratio and the effect of existing bonded tendon. From experimental results, for cracking, yielding and ultimate load, the effect of reinforcement ratio was more effective than concrete compression strength, and the beams having high strength concrete had a good performance than having low concrete, but there was no difference between high strength and low strength. And as L/dp was larger, test beams had a long region of ductility. This means that unbonded tendon has a large contribution after reinforcement yielding. Especially, the equation of ACI-318 was not match with test results and had no correlations. After analysis of test results, the equation of ultimate unbonded tendon stress without slip was proposed, and the proposed equation was well matched with test results. So the proposed equation in this paper will be a effective basis for the evaluation of unbonded tendons without slip, analysis and design.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.26 no.2A
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• pp.261-271
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• 2006

Many uncertainties affecting to the structural behavior of prestressed concrete (PSC) bridges reinforced with the un bonded external tendons are analyzed on the basis of the analytical method introduced in the companion paper. Many design parameters, which must be considered in design procedure, such as friction slip at the deviators, number of deviators, time-dependent deformations of concrete, relaxation of tendon and influence of loading history in PSC bridges are reviewed, and a lot of valuable results are obtained through this parametric study. In advance, the structural responses according to the external tendon profiles are analyzed to grasp if an optimum tendon profile depends on the applied loading type, and the obtained results show that the most stable structural response is revealed when the locations of deviators are coincident with the loading points.

• Transactions of the Korean Society of Automotive Engineers
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• v.3 no.4
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• pp.19-29
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• 1995

This paper discusses the stick-slip phenomenon of the driveline system of a vehicle in consideration of friction. Friction is operated on the between of flywheel and clutch disk. The expressions for obtaining the results have been derived from the equation of motion of a three degree of freedom frictional torsion vibration system which is made up driving part(engine, flywheel), driven part(clutch, transmission) and dynamic load part(vehicle body) by applying forth-order Rungekutta method. It was found that the great affect parameters of the stick-slip or stick motion were surface pressure force between flywheel and clutch disk, time decay parameter of surface pressure force and 1st torsional spring constant of clutch disk when driveline system had been affected by friction force. The results of this study can be used as basic design data of the clutch system for the ride quality improvement of a car.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.26 no.2A
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• pp.247-260
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• 2006

In this paper, an analytical method which can describe the structural behavior of prestressed concrete (PSC) bridges reinforced with the unbonded external tendon is developed. Since the unbonded external tendon is directly installed to the deviators while maintaining a straight configuration, it has a different deformation field from that of concrete and accompanies the secondary effect caused by the change of the primary eccentricity between concrete and external tendon. In advance, the friction slip at the deviators is also taken into consideration on the basis of the force equilibrium between the friction force and the driving force. Through correlation studies between experimental data and analytical results, it is verified that the proposed numerical model can effectively predict the structural behavior of PSC beam bridges with comparative precision.

• Journal of the Korean Recycled Construction Resources Institute
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• v.6 no.1
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• pp.66-71
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• 2018

In general, when an existing pier is enlarged and reinforced using a small diameter pile, bonded anchor with deformed reinforcing bars is used to maintain the integrity of the joint. However, in the case of bonded anchors, the performance depends largely on the type of joint material. Nevertheless, unlike mechanical anchors, there is no standard method for designing appropriate design methods and proper performance evaluation. Therefore, in this study, the performance of the anchoring anchor was evaluated by performing a model experiment using the reinforcing bars and anchor reinforcing bars. Experimental results show that the structural performance of the unbonded specimen is the best, and the failure mode is the punching shear failure. The deflection of the end of the member is smaller than that of the unconnected member, The deflection of the connected member is larger than the deflection of the small connected member. As the load increases, the possibility of slippage of the anchor steel or fold connection rebar is high.