• Journal of KSNVE
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• v.7 no.4
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• pp.631-636
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• 1997

A method to estimate the radiatio power to the surrounding formation due to axial vibration of the pipe in a fluid-filled borehole has been developed, by using the propagation modes of stress wave in an infinitely-long and uniform drilling borehole surrounded by a radially-infinite homogeneous formation. Also, the equivalent damping coefficient for the axial vibration of the pipe has been derived. As an example, results for a real drilling borehole has been presented. The analysis of the elastic motion of the infinite formation which has cylidrical cavity is simplified with the geometric axisymmetry and the low-frequency assumption so that the analytic solution is obtained.

• Journal of Welding and Joining
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• v.21 no.6
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• pp.40-45
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• 2003

Steel members have advantages of resisting torsion and axial compression. In design, residual stresses at the welded joint of T-shape steel pipes are one of the most important points to be considered. In this paper, characteristics of residual stresses of welded joints are clarified by carrying out 3D non-steady heat conduction analysis and 3D thermal elastic-plastic FE-analysis. According to the results, the production mechanism of residual stresses at the welded joint of T-shape steel pipe is clarified. In this paper, circumferential stresses depended on thermal histories but axial and radial stresses were more dependent on geometrical shape than thermal histories. Residual stresses in the axial direction on the lower part of pipe member were tensile, controlled by geometrical shape. However, in case of middle part, residual stresses in all the directions were controlled by thermal histories.

• Computers and Concrete
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• v.21 no.5
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• pp.569-582
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• 2018

In this study, nonlinear vibration and stability of a polymeric pipe reinforced by single-walled carbon naotubes (SWCNTs) conveying fluid-nanoparticles mixture flow is investigated. The Characteristics of the equivalent composite are determined using Mori-Tanaka model considering agglomeration effects. The surrounding elastic medium is simulated by orthotropic visco-Pasternak medium. Employing nonlinear strains-displacements, stress-strain energy method the governing equations were derived using Hamilton's principal. Differential quadrature method (DQM) is used for obtaining the frequency and critical fluid velocity. The influence of volume percent of SWCNTs, agglomeration, geometrical parameters of pipe, viscoelastic foundation and fluid velocity are shown on the frequency and critical fluid velocity of pipe. Results showed the increasing volume percent of SWCNTs leads to higher frequency and critical fluid velocity.

• Journal of the Society of Naval Architects of Korea
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• v.40 no.2
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• pp.63-68
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• 2003

With the trend of large-sized ship in Korea, recently several hundreds of thousands of U-bolts for a year have been used as a pipe fastener In this paper, we have evaluated the strength for present U-bolt structure by pipe supporting conditions(deck, ceiling and wall mounting type) For this purpose, the equivalent and bending stresses have been calculated by linear elastic analysis using the finite element program ABAQUS. At the same time, a variety of load conditions such as design pressure, weight effect and acceleration are also considered.

• Journal of the Korean Society of Environmental Restoration Technology
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• v.5 no.5
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• pp.11-21
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• 2002

A series of model tests is performed to evaluate the relationship between soil and a buried pipe in soil undergoing lateral movement. As the result of the model tests, a wedge zone and plastic flow zones could be observed in front of the pipe. And also an arc failure of cylindrical cavity could be observed at both upper and lower zones. Failure shapes in both cohesionless and cohesive soils are nearly same, which was investigated failure angle of $45^{\circ}+{\phi}/2$. In the cohesionless soil, the higher relative density produces the larger arc of cylindrical cavity. On the basis of failure mode observed from model tests, the lateral earth pressure acting on a buried pipe in soil undergoing lateral movement could be applying the cylindrical cavity extension mode. The deformation behavior of soils was typically appeared in three divisions, which are elastic zones, plastic zones and pressure behavior zones.

• Journal of Bio-Environment Control
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• v.7 no.3
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• pp.181-190
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• 1998

An elastic analysis under wind load was performed for the double layered plastic greenhouse model developed particularly for minimizing damages under typhoons at Cheju Citrus Research institute in Seagipo city. General EVA film was used for the inner covering and the developed special film which would break the wind pressure down was used for the outer covering. The wind tunnel test showed this special film reduced the wind speed up to 86 to 98% under well controlled situation. Based on the elastic analysis performed in the study, the behavior of the greenhouse was changed significantly due to the boundary conditions. Not like other researchers before we applied dead load of the concrete support to the ground pipe and fixed support boundary conditions at the 4 corner pipes. The analysis shows that the greenhouse was lifted and pulled the pipe out of the ground due to the sucking wind pressure. The behavior of the greenhouse was quite similar to that one real greenhouse failure. Therefore, not only we need to find the realistic boundary conditions for the supports, but also need to find how to rest the pipe supports on the ground without economic loss.

• Transactions of the Korean Society of Pressure Vessels and Piping
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• v.17 no.2
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• pp.119-125
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• 2021

Subsea pipelines are widely used to transport hydrocarbons from ultra-deep seawater to facilities on the coast. A sandwich pipe is a pipe-in-pipe system in which the annulus between the two concentric steel pipes is filled with polymer cores and fillers for insulation and structural reinforcement. Sandwich pipeline is always exposed to complex loading such as bending moment, bulking, internal and external pressures caused by installation, operation and environmental factors. This research provides insights into the structural integrity of sandwich pipeline exposed to complex loading conditions using a linear matching method (LMM). The finite element model of the sandwich pipeline has been generated from previous research, and the model validation is performed by comparing the results of the linear analysis between the two models. The temperature dependent material properties are used to simulate the behavior of real pipeline, and the elastic-perfectly plastic (EPP) model has been taken into account for the material non-linearity. Numerical results provide comprehensive insights into the structural response of the sandwich pipeline under monotonic and cyclic loading and provide notable points about the evaluation of the plastic collapse limit and the elastic shakedown limit of the sandwich pipeline.

• Steel and Composite Structures
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• v.49 no.2
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• pp.143-159
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• 2023

Recently, the design of scaffolding systems has garnered considerable attention due to the increasing number of scaffold collapses. These incidents arise from the underestimation of imposed loads and the site-specific conditions that restrict the application of lateral restraints in scaffold assemblies. The present study is committed to augmenting the buckling resistance of vertical support members, obviating the need for supplementary lateral restraints. To achieve this objective, experimental and computational analyses were performed to assess the axial load buckling capacity of steel props, composed of two hollow steel pipes that slide into each other for a certain length. Three full-scale steel props with various geometric properties were tested to construct and validate the analytical models. The total unsupported length of the steel props is 6 m, while three pins were installed to tighten the outer and inner pipes in the distance they overlapped. Finite Element (FE) modeling is carried out for the three steel props, and the developed models were verified using the experimental results. Also, theoretical analysis is utilized to verify the FE analysis. Using the FE-verified models, a parametric study is conducted to evaluate the effect of different inserted pipe lengths on the steel props' axial load capacity and lateral displacement. Based on the results, the typical failure mode for the studied steel props is global elastic buckling. Also, the prop's elastic buckling strength is sensitive to the inserted length of the smaller pipe. A threshold of minimum inserted length is one-third of the total length, after which the buckling strength increases. The present study offers a prop with enhanced buckling resistance and introduces an equation for calculating an equivalent effective length factor (k), which can be seamlessly incorporated into Euler's buckling equation, thereby facilitating the determination of the buckling capacity of the enhanced props and providing a pragmatic engineering solution.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1995.10a
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• pp.550-554
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• 1995

The present paper deals with the dynamic stability and vibration suppression of a cantilevered flexible pipe with a concetrated mass under an internal fluid flow. The equations of motion are derived by energy expressions using Hamilton's pronciple, and some analytical results using Galerkin's method are presented. Finally, the vibration suppression technique by means of an internal fluid flow is demonstrated experimentally.

• Journal of KSNVE
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• v.8 no.1
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• pp.171-179
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• 1998

The present paper deals with the dynamic stability and vibration suppression of a cantilevered flexible pipe having a tip mass under an internal flowing fluid. The equations of motion are derived by energy expressions using extended Hamilton's principle, and some analytical results using Galerkin's method are presented. Finally, the vibration suppression technique by means of an internal fluid flow is demonstrated experimentally.