• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.14 no.9 s.90
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• pp.779-784
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• 2004

This paper numerically analyzes the dynamic characteristics of a spindle system supported by two identical journal bearingsconsidering bearing span that has dynamic load due to its mass unbalance. The Reynolds equation is transformed to solve a herringbone grooved journal bearing. The Reynolds equations are solved using FEM in order to calculate the pressure distribution in a fluid film. Reaction forces and friction torque are obtained by integrating the pressure and shear stress along the fluid film, respectively. Dynamic behaviors, such as whirl radius or angular displacement of a rotor, are determined by solving its nonlinear equations of motion with the Runge-Kutta method. This research shows that the same bearing spans of upper and lower journal bearings produce the minimum runout and friction torque of a spindle system.

• Proceedings of the KSR Conference
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• 2004.10a
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• pp.781-787
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• 2004

Where the track is continuously welded over a bridge, the longitudinal force is interacted between the track and the sub-structure. Due to this respect, the expansion joint is used to decrease this force. But the expansion joint has several problems related to passenger comfort and maintenance etc. In this study, it is analysed about how the stability of the track is affected as the span length becomes longer in case of 2-span continuos bridge. It is found that there is no problem of an stability unless the span length is longer than 90m when the elastic shoe is used. And several parametric studies were also implemented.

• Proceedings of the Korea Concrete Institute Conference
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• 1998.10b
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• pp.680-685
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• 1998

Prestressed concrete I-girders were used in the bridge applications in the early 1950s. During the last four decades, the most widely used girder length of bridges have been below 30meters. The main objective of this study is to develope the alternative section for long span bridge which exceed 40 meters. The developed Bulb-Tee girder has a wide bottom flange to enhance the compressive strength and to allow placement of a large number of strands in the bottom flange. New bulb-tee shaped PSC girder sections are proposed in this paper. Splicing the technique for long span bridge girder to reduce the self weight is also proposed.

• Structural Engineering and Mechanics
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• v.12 no.3
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• pp.313-328
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• 2001

A multi-span bridge has the peak value of resultant girder moment or membrane stress at the interior support. In this paper, the spline finite strip method (FSM) is modified to obtain the more appropriate solution at the interior support where the peak values of solution exist. The modification has been achieved by expressing the shape function with non-periodic B-splines which have multiple knots at the boundary. The modified B-splines have the useful feature for interpolating the curve with sudden change in curvature. Moreover, the modified spline FSM is very efficient in analyzing multi-span box girder bridges, since a bridge can be modeled by an assembly of strips extended along the entire bridge length. Numerical examples of the bridge analysis have been performed to verify the efficiency and accuracy of the new spline FSM.

• Computers and Concrete
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• v.7 no.1
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• pp.1-16
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• 2010

A simplified method, developed from the softened strut-and-tie model, for determining the mid-span deflection of deep beams at ultimate state is proposed. The mid-span deflection and shear strength predictions of the proposed model are compared with the experimental data collected from 70 simply supported reinforced concrete deep beams, loaded with concentrated loads located at a distance a from an end reaction. The comparison shows that the proposed model can accurately predict the mid-span deflection and shear strength of deep beams with different shear span-to-depth ratios, different concrete strengths, and different horizontal and vertical hoops.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.10 no.3
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• pp.348-357
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• 1998

The flow characteristics inside U-bend tube of the laminated plate heat exchanger were numerically investigated. The behavior of fluid flow, and the variations of the faulty area and friction factor are examined according to the distance between the span and the wall and the diameter of the round attacked to the end of span. The results show that the diameter(d) of the round attached to the span is mainly associated with the smooth circulation of fluid flow rather than the size of faulty area and the friction factor. As the distance($\ell$) between the span and the wall decreases, the faulty area decreases, however the friction factor dramatically increases. It is also found that one can obtain a good result in the view of the flow characteristics and pressure drop at d=7.5mm and $\ell$=30.5mm.

• Wind and Structures
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• v.3 no.1
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• pp.41-58
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• 2000

According to research currently developed by several authors (including the present ones) a multimode approach to the aeroelastic instability can be appropriate for suspension bridges with very long span and so with close natural frequencies. Extending that research, this paper deals in particular with: i) the role of along-wind modes, underlined also by means of the flutter mode representation; ii) the effects of a variation of the mean wind speed along the span. A characterisation of the response in the time domain by means of an energetic approach is also discussed.

• Journal of the Korean Society of Marine Environment & Safety
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• v.2 no.1
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• pp.77-82
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• 1996

Subsea pipelines are exposed to several potential risks of damage due to wave, soil instability and other hazards. Structural failure of the steel pipelines will result in serious consequences such as release of transported hydrocarbons, pollution to the ocean environment and heavy costs due to repair. This paper examines the safety of subsea pipelines with free span which is one of high potential damages. The variation of an allowable length of static free span is examined for different boundary conditions and is given in a curve which is useful for the dsign of the subsea pipeline with a free span.

• International Journal of Ocean Engineering and Technology Speciallssue:Selected Papers
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• v.3 no.1
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• pp.49-55
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• 2000

Improvement was made on the free span analysis of the offshore pipelines. The effect of axial force (both tension and compressive force) can be explicitly applied to the current design code. The closed form solutions of beam-column equation were derived for the typical boundary conditions. The solutions can be used to find the natural frequencies of the span using the energy balance concept. The results can be applied to the current design code and will result more realistic calculation of free span lengths of offshore pipelines.

• Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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• 2002.10a
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• pp.29-33
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• 2002

A procedure of free span and fatigue analysis of offshore pipelines was made per DNV-RP-F105, 2002. The new method includes the axial force and deflection load in pipelines. The screening criteria were used to calculate the allowable span lengths. The screening criteria allow small amplitudes of vortex-induced vibration due to wave and current loading. However, the induced pipe stress is very small and usually below the limit stress of a typical S-N curve. A simplified method was established to calculate the fatigue damage due to long-term current distribution. The long-term current statistics was assumed with a 3-parameter Weibull distribution. The fatigue damage was estimated for the span lengths obtained from the screening criteria for various conditions. Sample calculations show the effect of axial force for various boundary conditions.