• Journal of Welding and Joining
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• v.29 no.4
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• pp.41-47
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• 2011

GMA welding process is a production process to improve productivity for the provision of higher welding quality of material. These includes numerous process variables that could affect welding quality, productivity and cost savings. Recently, the welding part of construction equipment had frequent failure of major components in the welding part of each subsidiary material due to shock which is very poor according to the welding part. Therefore, the implementation of sound welding procedure is the most decisive factor for the reliability of construction machinery. The data generated through experiments conducted in this study has validated its effectiveness for the optimization of bead geometry and process variables is presented. The criteria to control the process parameters, to achieve a good bead geometry. This study has developed mathematical models and algorithms to predict or control the bead geometry in GMA fillet welding process.

• Magazine of the Korean Society of Agricultural Engineers
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• v.36 no.1
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• pp.83-94
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• 1994

The first part of this study dealt with the determination of soil parameters for Lade's double work-hardening model using the raw data obtained from cubical and cylinderal triaxial tests At present, it should be investigated which test can simulated satisfactorily the behavior of soft clayey foundation. In this regard, plate bearing test on the 2-dimentional model foundation(218cm long, 40cm wide, 19&m high) was performed, and finite element analysis carried out to abtain the behavior of the foundation. Settlement, lateral displacement, displacement vector and mode of failure were measured and these values were compared with numerical values in order to validate the numerical program developed by authors. The FEM technique was based on Christain-Boehmer's method, in which the displacement is obtained at each nodal point while stress and pore water pressure at each element.In this research, Biot's equation, which explains was elahorately the phisical meaning of consolidation, was selected, as a governing equation, coupled with Lade's double surface work-hardening constitutive model.

• Journal of Ocean Engineering and Technology
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• v.17 no.3 s.52
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• pp.46-51
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• 2003

Acoustic emission (AE) signals, emanated during local failure of aluminum alloys, have been the subject of numerous investigations. It is well known that the characteristics of AE are strongly influenced by the previous thermal and mechanical treatment of the sample. Possible sources of AE during deformation have been suggested as the avalanche motion of dislocations, fracture of brittle particles, and debonding of these particles from the alloy matrix. The goal of the present study is to determine if AE occurring as the result of fatigue crack propagation could be evaluated by the joint time-frequency analysis method, short time Fourier transform (STFT), and Wigner-Ville distribution (WVD). The time-frequency analysis methods can be used to analyze non-stationary AE more effectively than conventional techniques. STFT is more effective than WVD in analyzing AE signals. Noise and frequency characteristics of crack openings and closures could be separated using STFT. The influence of various fatigue parameters on the frequency characteristics of AE signals was investigated.

• Journal of Korean Association for Spatial Structures
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• v.6 no.4 s.22
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• pp.35-44
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• 2006

The form-resistant Systems like a dome and shell are used more widely than post-beam structure system in large space structure. Single layer latticed dome system, one of the form-resistant system, has great merits in manufacturing and constructing but the failure mechanism is not clarified yet. The purpose of this paper is to find out the buckling characteristics of single-layer latticed domes with square network by using the experimental method. Major test parameters are the stiffness of lattice member and space of square lattice. The specimens are applied uniform loading of snow type.

• Journal of the Korean Society of Safety
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• v.14 no.1
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• pp.129-140
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• 1999

This study presents test results of RC beams strengthened by steel plates, carbon fiber sheets(CFS) and aramid fiber sheets(AFS) for increasing flexural and shear resistance. The test was performed with different parameters including the type of strengthening materials, flexural-strengthening methods and shear-strengthening methods. In case of flexural test, RC beams are initially loaded to 70% of the ultimate flexural capacity and in case of shear test loaded to 60 or 80 percent of the ultimate shear capacity and subsequently reinforced with steel plates, CFS and AFS. Experimental data on strength, steel strain, deflection, and mode of failure of the reinforced beams were obtained, and comparisons between the different shear reinforced schemes and the non-strengthened control beams were made. The test results showed that damaged RC beams strengthened by steel plates, CFS and AFS have more improved the flexural and shear capacity. For the beams with external reinforcement by steel plates, aramid fiber sheets and carbon fiber sheets increases in ultimate strength of 4 to 21, 17 to 43 and 26 to 36 percent were respectively achieved. Initial load had small effect on strength after reinforcement, but an important influence on deflection. One sheet reinforced was stronger than two sheets reinforced but less deflected than two sheets reinforced.

• Journal of the Korea Institute of Military Science and Technology
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• v.14 no.3
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• pp.405-413
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• 2011

Defense Systems Test Center in ADD supports increasingly various missile test requirements such as higher altitude event, multi target operation and low-altitude, high velocity target tracking. In this paper, we have proposed the development of instrumentation radar tracking status simulator based on virtual reality. This simulator can predict the tracking status and risk of failure using several modeling algorithms. It consists of target model, radar model, environment model and several algorithms includes the multipath interference effects. Simulation results show that the predict tracking status and signal are similar to the test results of the live flight test. This simulator predicts and analyze all of the status and critical parameters such as the optimal site location, servo response, optimal flight trajectory, LOS(Line of Sight). This simulator provides the mission plan with a powerful M&S tool to rehearse and analyze instrumentation tracking radar measurement plan for live flight test at DSTC(Defense Systems Test Center).

• Steel and Composite Structures
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• v.18 no.5
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• pp.1177-1195
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• 2015

Six specimens are tested to investigate the cyclic behavior of beam-to-column abnormal joints in steel moment-resisting frames, which are designed according to the principle of strong-member and weak-panel zone. Key parameters include the axial compression ratio of column and the section depth ratio of beams. Experimental results indicate that four types of failure patterns occurred during the loading process. The $P-{\Delta}$ hysteretic loops are stable and plentiful, but have different changing tendency at the positive and negative direction in the later of loading process due to mechanical behaviors of specimens. The ultimate strength tends to increase with the decrease of the section depth ratio of beams, but it is not apparent relationship to the axial compression ratio of column, which is less than 0.5. The top panel zone has good deformation capacity and the shear rotation can reach to 0.04 rad. The top panel zone and the bottom panel zone don't work as a whole. Based on the experimental results, the equation for shear strength of the abnormal joint panel zone is established by considering the restriction of the bottom panel zone to the top panel zone, which is suitable for the abnormal joint of H-shaped or box column and beams with different depths.

• Computers and Concrete
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• v.15 no.3
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• pp.411-436
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• 2015

In this work, a comprehensive approach to model the structural behaviour of Reinforced Concrete (RC) beams subjected to reinforcement corrosion is proposed. The coupled environmental - mechanical damage model developed by some of the authors is enhanced for considering the main effects of corrosion on concrete, on composite interaction between reinforcement bars and concrete and on steel reinforcement. This approach is adopted for reproducing a set of experimental tests on RC beams with different corrosion degrees. After the simulation of the sound beams, the main parameters involved in the relationships characterizing the effects of corrosion are calibrated and tested, referring to one degraded beam. Then, in order to validate the proposed approach and to assess its ability to predict the structural response of deteriorated elements, several corroded beams are analyzed. The numerical results show a good agreement with the experimental ones: in particular, the proposed model properly predicts the structural response in terms of both failure mode and load-deflection curves, with increasing corrosion level.

• Steel and Composite Structures
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• v.20 no.6
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• pp.1305-1322
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• 2016

This paper presents the results of experimental and numerical model analyses on partially encased composite columns under concentric loads. The main objective of this study is to evaluate the influence of replacing the conventional longitudinal and transverse steel bars by welded wire mesh on the structural behavior of these members under concentric loads. To achieve these goals experimental tests on four specimens of partially encased composite columns submitted to axial loading were performed and the results were promising in terms of replacing the traditional reinforcement by steel meshes. In addition, a numerical FE model was developed using the software DIANA$^{(R)}$ with FX+. The experimental results were used to validate the numerical model. Satisfactory agreement between experimental and numerical results was observed in both capacity and deformability of the composite columns. Despite of the simplifying assumptions of perfect bond between steel and concrete, the numerical model adequately represented the columns behavior. A finite element parametric study was performed and parameters including thickness of the steel profile and the concrete and steel strengths were evaluated. The parametrical study results found no significant changes in the partially encased columns behavior due to variations of the steel profile thickness or yield strength. However, significant changes in the post peak behavior were observed when using high strength concrete and these results suggest a change in the failure mode.

• Structural Engineering and Mechanics
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• v.36 no.4
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• pp.513-527
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• 2010

This paper presents a three-dimensional finite element method based structural analysis model for structural analysis of reinforced concrete high-rise buildings during construction. The model considered the time-dependency of the structural configuration and material properties as well as the effect of the construction rate and shoring stiffness. Uniaxial compression tests of young concrete within 28 days of age were conducted to establish the time-dependent compressive stress-strain relationship of concrete, which was then used as input parameters to the structural analysis model. In-situ tests of a RC high-rise building were conducted, the results of which were used for model verification. Good agreement between the test results and model predictions was achieved. At the end, a parametric study was conducted using the verified model. The results indicated that the floor position and construction rate had significant effect on the shore load, whereas the influence of the shore removal timing and shore stiffness have much smaller. It was also found that the floors are more prone to cracking during construction than is ultimate bending failure.