• Steel and Composite Structures
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• v.7 no.1
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• pp.35-52
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• 2007

The cold formed light-gauge profiled steel sheeting can offer considerable shear resistance acting in the steel building frame. This paper conducted the full-scale test on the shear behavior of stressed skin diaphragm using profiled sheeting connected by the self-tapping screws. A three-dimensional finite element model that simulates the stressed skin diaphragm was developed. The sheet was modeled using thin element model while the supporting members were simulated using beam elements. Fasteners were represented in the numerical model as equivalent springs. A joint test program was conducted to characterize the properties of these springs and results were reported in this study. Finite element model of the full-scale test was analyzed by use of the ANSYS package, considering nonlinearity caused by the large deflection and slip of fasteners. The experimental data was compared with the results acquired by the EUR formulas and finite element analysis.

• Geomechanics and Engineering
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• v.15 no.3
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• pp.899-910
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• 2018

Terrace deposits are often encountered in portal areas and tunnels with low overburden. They are challenging to excavate considering their great mechanical and spatial heterogeneity and a very high stiffness contrast within the ground. Terrace deposits are difficult to characterize, considering that samples for laboratory testing are almost unfeasible to obtain, and laboratory tests may not be representative due to scale effects. This paper presents the approach taken for their characterization during the design stage and their posterior validation performed during construction. Lessons learned from several tunnels excavated on terrace deposits on the Bogota-Villavicencio road (central-east Colombia), suggest that based on numerical simulations, laboratory testing and tunnel system behaviour monitoring, an observational approach allows engineers to optimize the excavation and support methods for the encountered ground conditions, resulting in a more economic and safe construction.

• Journal of the Korean Society for Nondestructive Testing
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• v.25 no.6
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• pp.431-438
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• 2005

Bubble behaviors in a circular tube have been analyzed numerically and experimentally by a three-dimensional tomography method, Initially, a multiplicative algebraic reconstruction technique (MART) which showed better results for previous studies of numerical simulations has been performed to confirm the accuracy of the three-dimensional reconstruction for the two-phase flow using a computer-synthesized phantom, Then, bubble behaviors have been investigated experimentally by the three-dimensional MART method using real projected data captured simultaneously by a laser and three CCD cameras for three angles of view, Also, the transient reconstructions have been attempted to analyze the real-time oxygen-bubble movements in water by the interval of 1/30 second.

• Journal of the Korean Society for Nondestructive Testing
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• v.25 no.3
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• pp.222-227
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• 2005

An efficient technique fur the calculation of guided wave dispersion curves in composite pipes is presented. The technique uses a forward-calculating variational calculus approach rather than the guess and iterate process required when using the more traditional partial wave superposition technique. The formulation of each method is outlined and compared. The forward-calculating formulation is used to develop finite element software for dispersion curve calculation. Finally, the technique is used to calculate dispersion curves for several structures, including an isotropic bar, two multi-layer composite bars, and a composite pipe.

• 한국전산유체공학회:학술대회논문집
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• 2008.03b
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• pp.201-204
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• 2008

Vortex and swirl occurring in a pump suction intake sump normally reduce the performance and disturb the safe operation of the circulation water pump in thermal power plants. This paper presents a case study of one particular intake sump design via a CFD analysis and a hydraulic model testing. The physical experiments and numerical analysis were performed under two flow and three level variation conditions. The vortex patterns around the pump suction pipe have been predicted by a commercial CFD code with the k-${\varepsilon}$ model. The model tests were conducted on a 1/10 model for a practical intake sump. The location, number and general pattern of the free surface vortex and submerged vortex predicted by CFD simulation were found to be a good agreement with those observed in the model testing.

• International Journal of Fluid Machinery and Systems
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• v.7 no.3
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• pp.101-109
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• 2014

Sediment erosion is one of the key challenges in hydraulic turbines from a design and maintenance perspective in Himalayas. The present study focuses on choosing the best design in terms of blade angle distribution of a Francis turbine runner which has least erosion effect without influencing the efficiency and the structural integrity. A fully coupled Fluid-Structure-Interaction (FSI) analysis was performed through a multi-field solver, which showed that the maximum stress induced in the optimized design for better sediment handling, is less than that induced in the reference design. Some numerical validation techniques have been shown for both CFD and FSI analysis.

• Journal of the Korean Society for Nondestructive Testing
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• v.29 no.3
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• pp.242-247
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• 2009

The ability of time reversal techniques to focus ultrasonic beams on the source location is important in many aspects of ultrasonic nondestructive evaluation. In this paper, we investigate the time reversal beam focusing of ultrasonic array sensors on a defect in layered media. Numerical modeling is performed using the commercially available software which employs a time domain finite difference method. Two different time reversal approaches are considered - the through transmission and the pulse-echo. Linear array sensors composed of N elements of line sources are used for signal reception/excitation, time reversal, and reemission in time reversal processes associated with the scattering source of a side-drilled hole located in the second layer of two layer structure. The simulation results demonstrate the time reversal focusing even with multiple reflections from the interface of layered structure. We examine the focusing resolution that is related to the propagation distance, the size of array sensor and the wavelength.

• Proceedings of the KIEE Conference
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• 2001.04a
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• pp.126-128
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• 2001

In this paper, Magnetic Flux Leakage(MFL) method is used to detect surface defect in ferromagnetic plate. Surface defects are created on the SM 45C ferromagnetic plate and magnetizing equipment is composed to perform MFL nondestructive testing. The length and width of defect is twice the thickness of ferromagnetic plate, and defects with different depths are made artificially for the experiment. Also, NdFeB magnet in magnetizing equipment is used to make magnetic flux. This paper shows that it is possibile to detect 10% defect and to analyze numerically for any defect using MFL method.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2001.10a
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• pp.135-140
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• 2001

The radar method is becoming one of the major nondestructive testing (NDT) techniques for concrete structures. Numerical modeling of electromagnetic wave is needed to analyze radar measurement results and to study the influence of measurement parameters on the radar measurements. Finite difference-time domain (FD-TD) method is used to simulate electromagnetic wave propagation through concrete specimens. In the experiments, three concrete specimens are made with the dimensions of 100 cm (length) x 100 cm (wideth) x 14 cm (depth). Three specimens had a Dl6 steel bar at 8, 10, 12 cm depth.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2001.10a
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• pp.245-252
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• 2001

The ultimate strength testing of a two-story, single-bay, and sway allowed space steel frame was performed. Considering a majority of large-scale frame tests in the past, only two-dimensional frames were experimentally studied. Therefore, three-dimensional experiment is needed to extend the knowledge of this field. The steel frame subjected to non-proportional vertical and horizontal load was tested. The load-displacement curve of the test frame is provided. The experiment results are useful for verification of the three-dimensional numerical analysis. The results obtained from 3D non-linear analysis using ABAQUS were compared with experimental data.