• Structural Engineering and Mechanics
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• v.88 no.6
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• pp.599-608
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• 2023

The present study is focused on instigation of the nonlinear mechanical behavior of reinforced concrete beams considering different types of FRP bars through nonlinear finite element simulations. To explore the impact of the FRP reinforcement type and geometry on the nonlinear mechanical behavior of reinforced beam, intensive parametric studies are carried out and discussed. Twenty models were carried out based on the finite element software (ABAQUS). The concrete damage plasticity model was considered. Four types of fiber polymer bars, CFRP, GFRP, AFRP and BFRP as longitudinal reinforcement for concrete beam were used. The validation of numerical results was confirmed by experimental as well as numerical results, then the parametric study was conducted to evaluate the effect of change in different parameters, such as bar diameter size, type of FRP bars and shear span length. All results were analyzed and discussed through, load-deflection diagram. The results showed that the use of FRP bars in rebar concrete beam improves the beam stiffness and enhance the ultimate load capacity. The load capacity enhanced in the range of (20.44-244.47%) when using different types of FRP bars. The load-carrying capacity of beams reinforced with CFRP is the highest one, beams reinforced with AFRP is higher than that reinforced with BFRP but beams reinforced with GFRP recorded the lowest load of capacity compered with other beams reinforced with FRP Bars.

• Journal of KIISE:Software and Applications
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• v.36 no.6
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• pp.443-450
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• 2009

In an earlier development phase, the simulation technique is one of the key analysis methods for checking the correctness of system's functional requirements. In general, simulation is manually or randomly performed by executing state machine diagrams according to the requirement scenarios. Therefore, simulation is one of the most effort-consuming tasks. In this paper, an automatic simulation technique of state machine diagrams is provided according to the scenarios of the sequence diagrams. It is not easy to generate detailed simulation traces from sequence diagrams due to different abstraction levels between sequence diagrams and state machine diagrams. In order to adjust for different abstraction levels, state machine diagrams and sequence diagrams are transformed into LTS models and compositional analysis and transition reduction are performed. After checking behavior conformance between them, detailed simulation traces for the state machine diagrams are generated. These simulation traces are used not only for performing automatic simulation but also for assisting analyzers to reach a specific system state in order to guide further efficient simulation.

• Computational Structural Engineering
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• v.10 no.3
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• pp.167-174
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• 1997

Engineers must be aware of possible sources of chaotic behavior. They may render conventional design predictions untrustworthy and potentially unsafe because of the sensitivity to initial conditions. Dynamic responses of a spherical shell subjected to impulsive loading which act on the center are analyzed using the finite element method. The chaotic responses are identified by the standard methods, such as displacement-time histories, Poincare maps, and phase diagrams. The responses are chaotic, but, not so sensitive to the initial conditions, and the characteristics of responses are not changed with time, in contrast to the case of the responses of beam. The Poincare points scattered in the limited area represent that the responses are chaotic, but do not show the geometric structures. The snap-through phenomena of the shell to the side of the direction of the load or of the opposite direction, is analysed by using the energy diagram.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.32 no.6
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• pp.519-525
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• 2008

For this study, SM45C steel rods using generally for power transmission shafts and machine components was selected and welded by butt-GMAW method. And then it was studied about estimation of fatigue strength and the region of infinite life by Haigh diagram using Goodman's equation. Fatigue strength in weld zone presents highly in order of the boundary between deposited metal zone and heat affected zone, deposited metal zone, heat affected zone. This result agrees with distribution of hardness in weld zone. Fatigue strength in base metal zone presents highly compared with weld zone in low cycles between $10^4$ cycles and $10^6$cycles, but it presents the lowest fatigue strength on the order of heat affected zone in the vicinity of $10^6$cycles. It is the result that the first high compressive residual stress distributed by drawing process of the steel rods is released and the base metal is softened by alternating stresses. The region of infinite life by Haigh diagram presents highly in order of the boundary between deposited metal zone and heat affected zone, deposited metal zone, heat affected zone. From this results, it is demanded that the stress for safety design of machine components using SM45C butt-welded steel rods must be selected in the region of the lowest infinite life of heat affected zone.

• Structural Engineering and Mechanics
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• v.72 no.6
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• pp.675-687
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• 2019

As the bridges are an integral part of the transportation network, their function as one of the most important vital arteries during an earthquake is fundamental. In a design point of view, the bridges piers, and in particular the wall piers, are considered as effective structural elements in the seismic response of bridge structures due to their cantilever performance. Owing to reduced seismic load during design procedure, the response of these structural components should be ductile. This ductile behavior has a direct and decisive correlation to the development of plastic hinge region at the base of the wall pier. Several international seismic design codes and guidelines have suggested special detailing to assure ductile response in this region. In this paper, the parameters which affect the length of plastic hinge region in the reinforced concrete bridge with wall piers were examined and the sensitivity of these parameters was evaluated on the length of the plastic hinge region. Sensitivity analysis was accomplished by independently variable parameters with one standard deviation away from their means. For this aim, the Monte Carlo simulation, tornado diagram analysis, and first order second moment method were used to determine the uncertainties associated with analysis parameters. The results showed that, among the considered design variables, the aspect ratio of the pier wall (length to width ratio) and axial load level were the most important design parameters in the plastic hinge region, while the yield strength of transverse reinforcements had the least effect on determining the length of this region.

• The KIPS Transactions:PartD
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• v.11D no.3
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• pp.649-658
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• 2004

An object-oriented system is organized by a set of interacting objects and the system behavior is represented by the cooperating interaction bet ween objects. The characteristics of object-oriented software. such as inheritance and polymorphism, increase the difficulty of the object-oriented software testing. At running time of a program, one call from a member function can bind to other member functions because of the dynamic characteristics such as concurrence, dynamic binding and interaction. Therefore, there need the research about considering the characteristics of object-oriented software and concurrently testing the interaction between objects. In this paper, we propose the techniques as follows. First, we construct a flattened state chart diagram by considering the inheritance and polymorphism. Next, we model the system with CPN(Colored Petri Net) that usually is applying the system modeling and simulation. Last, we propose a test case generation techniques for testing the interaction between objects in object-oriented software by applying a Design/CPN tool.

• Nuclear Engineering and Technology
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• v.47 no.6
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• pp.712-718
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• 2015

Cast duplex stainless steels are susceptible to thermal aging during long-term service at temperatures ranging from $280^{\circ}C$ to $450^{\circ}C$. To analyze the effect of thermal aging on leak-before-break (LBB) behavior, three-dimensional finite element analysis models were built for circumferentially cracked pipes. Based on the elasticeplastic fracture mechanics theory, the detectable leakage crack length calculation and J-integral stability assessment diagram approach were carried out under different bending moments. The LBB curves and LBB assessment diagrams for unaged and thermally aged pipes were constructed. The results show that the detectable leakage crack length for thermally aged pipes increases with increasing bending moments, whereas the critical crack length decreases. The ligament instability line and critical crack length line for thermally aged pipes move downward and to the left, respectively, and unsafe LBB assessment results will be produced if thermal aging is not considered. If the applied bending moment is increased, the degree of safety decreases in the LBB assessment.

• Korean Journal of Health Education and Promotion
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• v.35 no.5
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• pp.1-16
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• 2018

Objectives: This study aimed to examine systems behavior of urban walking by analyzing a dynamic structure in Seoul, South Korea. Methods: As a systems thinking approach to urban walking and health promotion, we developed a Casual Loop Diagram based on literature review and expert consultation. The reviewed literature included: 1) qualitative studies that explores the experiences of urban walkers in Seoul; 2) a systematic review study on the built environmental factors related to walking; 3) policy research reports related to urban walking in Seoul. Results: The feedback structure for urban walking was related to the three urban environments (safety & walking environment, socioeconomic environment, and public transportation environment), and was characterized by a trade-off consisting of eight reinforcing loops and four balancing loops. Conclusions: The policies for a walkable city require multi-sectoral cooperation in order to change the causal loop structure related to the decline of walking. Therefore, it is necessary to establish legal and institutional conditions so that multi-sectoral and multidisciplinary approaches are possible.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 1999.06a
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• pp.215-219
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• 1999

One of the innovative physical methods that provide insight into the basic processes which determine friction and wear behavior of coated machine tools is acoustic emission (AE). In this study, an investigation of the relation between AE and friction signal produced during repeated sliding test is presented. The material of test specimens is CrN coated 0.2% plain carbon steel with 1 Um thickness. The obtained results demonstrate that AE signal is very related with friction, and AE signal is more sensitive than friction when CrN coated film come off the substrate.

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 2002.03a
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• pp.135-142
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• 2002

This paper introduces the technologies related to seismic resistance assessment of nuclear power plant structures by seismic fragility analysis(SFA). The inelastic energy absorption factor is considered in SFA to represent the effects due to the nonlinear behavior of structures and has a significant effect on the seismic fragility that is a probability of failure of structures by earthquake. Several practical methods to evaluate the inelastic energy absorption capacity of structures are investigated. The capacities determined by those methods are compared with each other. And an improved method that uses the inelastic demand capacity diagram is presented. Conclusively, some comments on each method for practical application are made.