• Journal of the Korea institute for structural maintenance and inspection
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• v.25 no.1
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• pp.16-24
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• 2021

This experimental study was conducted to evaluate the in-plane and out-of-plane seismic performances of an unreinforced masonry walls (URMs) strengthened with prestressed steel-bar truss systems developed in the present investigation. The truss systems were installed on both faces of the walls. All the wall specimens were subjected to lateral in-plane or out-of-plane cyclic loads at the fixed gravity stress of 0.25 MPa. The seismic performance of the strengthened specimens was compared to that measured in the counterpart URM. When compared with the lateral load-displacement curve of the URM, the strengthened walls exhibited the following improvements: 190% for initial stiffness, 180% for peak strength, 610% for accumulated energy dissipation capacity, and 510% for equivalent damping ratio under the in-plane state; the corresponding improvements under the out-of-plane state were 230% for initial stiffness, 190% for peak strength, 240% for accumulated energy dissipation capacity, and 120% for equivalent damping ratio, respectively. These results indicate that the developed technique is very promising in enhancing the overall seismic performance of URM.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2006.04a
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• pp.891-897
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• 2006

The volume control method which utilize a pressure node added into a finite shell element can overcome the drawbacks of conventional load control method and displacement control method. In this study, an improved volume control method is introduced for effective analysis of path-dependant behaviors of RC structures subjected to cyclic loading. RC shell structures including RC hollow columns are anlayized by discretizing the structures with layered shell elements and by applying in-plane two dimensional constitutive equations for concrete layers and reinforcement layers of the shell elements. The so-called path dependant volume control method is verified by comparing analysis results with other data including experimental results.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2003.10a
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• pp.585-590
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• 2003

To overcome the drawbacks of conventional load control method and displacement control method, the so-called volume control method was developed by utilizing a pressure node added into a finite shell element. In this study, an improved volume control method which can analyze path-dependant behaviors of RC shell structures subjected to cyclic loading effectively is developed. RC shell structures are discretized with layered shell elements and in-plane two dimensional constitutive equations for concrete and reinforcements are implemented for each layer of the shell elements. Validity of the so-called path dependant volume control method is also verified by comparing analysis results with other data including experimental results.

• Steel and Composite Structures
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• v.23 no.5
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• pp.571-583
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• 2017

A kind of accordion-web RBS connection, "Tubular Web RBS (TW-RBS)" connection is proposed in this research. TW-RBS is made by replacing a part of web with a tube at the desirable location of the beam plastic hinge. This paper presents first a numerical study under cyclic load using ABAQUS finite element software. A test specimen is used for calibration and comparison of numerical results. Obtained results indicated that TW-RBS would reduce contribution of the beam web to the whole moment strength and creates a ductile fuse far from components of the beam-to-column connection. Besides, TW-RBS connection can increase story drift capacity up to 9% in the case of shallow beams which is much more than those stipulated by the current seismic codes. Furthermore, the tubular web like corrugated sheet can improve both the out-of-plane stiffness of the beam longitudinal axis and the flange stability condition due to the smaller width to thickness ratio of the beam flange in the plastic hinge region. Thus, the tubular web in the plastic hinge region improves lateral-torsional buckling stability of the beam as just local buckling of the beam flange at the center of the reduced section was observed during the tests. Also change of direction of strain in arc shape of the tubular web section is smaller than the accordion webs with sharp corners therefore the tubular web provides a better condition in terms of low-cycle fatigue than other accordion web with sharp corners.

• Journal of Advanced Marine Engineering and Technology
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• v.29 no.8
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• pp.862-869
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• 2005

A study on convective cooling characteristics has been done in the channels with heat pipes and associated Plane fins Analysis with FLUENT V5.0 lies its Purpose on the possible enhancement of heat transfer capability between an existing three in-line arrayed heatpipes and an extending four in-line arrayed heatpipes with increasing channel width. Numerical analysis is limited to the laminar flow in an isolated flow channel by employing cyclic boundary conditions for calculation purposes. Friction factors for three and four in-line arrayed heatpipes are compared with experimental results. In addition, temperature behavior at the plate fin for the three in-line arrayed heatpipes is compared with experiment. Friction factors and overall channel heat transfer coefficients (and/or Nusselt numbers) are presented as a function of Reynolds number. An increase of number of heatpipes and channel width reults in a decrease of the friction factor and doesn't not result in an increase of heat transfer performance. However. considering the 25$\%$ increase of heat load accompanies with maximum 8$^{\circ}C$ rise of average temperature of heat pipes, the four in-line array with the increase of channel width of heat pipe heat sink can be considered appropriate.

• Journal of the Korea institute for structural maintenance and inspection
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• v.25 no.1
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• pp.112-119
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• 2021

The failure mode of piping systems due to seismic loads is the low-cycle fatigue failure with ratcheting, and it was found that the element in which nonlinear behavior is concentrated and damage occurs is the elbow. In this study, to quantitatively express the failure criteria for a pipe elbow of SCH40 3-inch carbon steel under low-cycle fatigue, the limit state was defined as leakage, and the in-plane cyclic loading test was conducted. For the carbon steel pipe elbow, which is the vulnerable part to seismic load of piping systems, the damage index was represented using the moment-deformation angle relationship, and it was compared and analyzed with the damage index calculated using the force-displacement relationship. An attempt was made to quantitatively express the limit state of the carbon steel pipe elbow involving leakage using the damage index, which was based on the dissipated energy caused by repeated external forces.

• Journal of the Korea Concrete Institute
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• v.19 no.3
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• pp.341-350
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• 2007

The volume control method which utilize a pressure node added into a finite shell element can overcome the drawbacks of conventional load control method and displacement control method. In this study, an improved volume control method is introduced for effective analysis of path-dependent behaviors of RC columns subjected to lateral cyclic loading or reversed cyclic loading along with compressive loading. RC shell structures and RC hollow columns are analyzed by discretizing the structures with layered shell elements and by applying in-plane two dimensional constitutive equations for concrete layers and reinforcement layers of the shell elements. The so-called path dependent volume control method as a finite element analysis technique is verified by comparing analysis results with other data including experimental results. The validity and applicability of the modeling technique is also confirmed by the comparison.

• Nuclear Engineering and Technology
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• v.51 no.2
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• pp.561-572
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• 2019

In the design criterion for the nuclear power plant piping system, the limit state of the piping against an earthquake is assumed to be plastic collapse. The failure of a common piping system, however, means the leakage caused by the cracks. Therefore, for the seismic fragility analysis of a nuclear power plant, a method capable of quantitatively expressing the failure of an actual piping system is required. In this study, it was conducted to propose a quantitative failure criterion for piping system, which is required for the seismic fragility analysis of nuclear power plants against critical accidents. The in-plane cyclic loading test was conducted to propose a quantitative failure criterion for steel pipe elbows in the nuclear power plant piping system. Nonlinear analysis was conducted using a finite element model, and the results were compared with the test results to verify the effectiveness of the finite element model. The collapse load point derived from the experiment and analysis results and the damage index based on the stress-strain relationship were defined as failure criteria, and seismic fragility analysis was conducted for the piping system of the BNL (Brookhaven National Laboratory) - NRC (Nuclear Regulatory Commission) benchmark model.

• Tribology and Lubricants
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• v.1 no.1
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• pp.46-58
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• 1985

The basic mechanism of lubrication between the piston ring and the cylinder wall is developed theoretically under the assumption of a reciprocating and dynamically loaded slider-bearing pair of parabolic form and smooth plane. A numerical computation for the prediction in cyclic variations of film thickness, net lubricant flow and frictional behaviour is attempted, and the influenec on the performance characteristics due to the ring height, ring face radius of curvature and the degree of offset, is also examined. The computational procedures develeped for a single ring system are extended and applied further to the complex problem of a ring pack system. It is well known that the ring pressure which is the total load on a ring, can be obtained from either an experimental measurement or a gas flow analysis. In this work, the latter of a gas low analysis method was used to calculate the pressures. It is remarked that the work done was focused on the role of flow continuity and lubricant starvation within the ring pack lubrication.

• Structural Engineering and Mechanics
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• v.51 no.3
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• pp.413-431
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• 2014

By carrying out the experiment of eight pieces of brick masonry walls with pilaster strengthened by Glass fiber reinforced polymer (GFRP) and one piece of normal masonry wall with pilaster under low reversed cyclic loading, the failure characteristic of every wall is explained; Seismic performances such as hysteresis, stiffness and its degeneration, deformation, energy consumption and influence of some measures including strengthening means, reinforcement area proportion between GFRP and wall surface, "through-wall" anchor on reinforcement effects are studied. The test results showed that strengthening modes have little influence on stiffness, stiffness degeneration and deformation of the wall, but it is another thing for energy consumption of the wall; The ultimate load, deformation and energy consumption of the walls reinforced by glass fiber sheets was increased remarkably, rigidity and its degeneration was slower; Seismic performance of the wall which considers strengthening means, reinforcement area proportion between GFRP and wall surface, "through-wall" anchor at the same time is better than under the other conditions.