• Earthquakes and Structures
• /
• v.23 no.2
• /
• pp.183-196
• /
• 2022

Reduced beam section (RBS) moment connections used in special moment resisting frames are currently limited to beam sections that are not larger than nominal depths of 920 mm, weight of 447 kg/m and flange thickness of 44 mm. Due to the higher demand for structural components with jumbo sections, which can potentially be applied in the transfer girders in long-span building structures, the newly available steel heavy members are promising. To address this issue, advanced numerical models are developed to fully evaluate the distribution of stresses and concentrations of plastic strains for such jumbo RBS connections. This paper first presents a brief overview of an experimental study on four specimens with large beam and column sections. Then, a numerical model that includes initial imperfections, residual stresses, geometric nonlinearity, and explicitly modeled welds is presented. The model is used to further explore the behavior of the test specimens, including distribution of stresses, distribution of plastic strains, stress triaxiality and potential for fracture. The results reveal that the stresses are highly non-uniform across the beam flange and, similarly, the plastic strains concentrate at the extreme fiber of the bottom flange. However, neither of these phenomena, which are primarily a function of beam flange thickness, is reflected in current design procedures.

• Journal of the Korean Society for Railway
• /
• v.16 no.1
• /
• pp.14-19
• /
• 2013

Because excessive interior noise when riding a high-speed train leads to annoyances, fatigue and stress for passengers, interior noise reduction methods should be considered. In particular, a high-speed train operated in various operation environments, and in South Korea, these include open fields and tunnels. Therefore, a specific study about changes in interior noise characteristics according to different environments is necessary. For this reason, the interior noise characteristics on a KTX train and on the KTX-Sancheon train were analyzed from noise measurements using microphones in this paper. Vibrations on the axles, bogies and floor were also measured, are these area are structural paths for interior noise. From this research, the interior noise characteristics according to the driving speed were deduced and the effects on interior noise by driving environments such as open fields and tunnels were investigated. Furthermore, the effect on interior noise by axles, bogies and floor vibrations were analyzed from a transfer function analysis.

• Journal of Ocean Engineering and Technology
• /
• v.33 no.5
• /
• pp.435-446
• /
• 2019

Because offshore structures are affected by various environmental loads, the risk of damage is high. As a result of ever-changing ocean environmental loads, damage to offshore structures is expected to differ from year to year. However, in previous studies, it was assumed that a relatively short period of load acts repeatedly during the design life of a structure. In this study, the residual life of an offshore wind turbine support structure was evaluated in consideration of the timing uncertainty of the ocean environmental load. Sampling points for the wind velocity, wave height, and wave period were generated using a central composites design, and a transfer function was constructed from the numerical analysis results. A simulation was performed using the joint probability model of ocean environmental loads. The stress time history was calculated by entering the load samples generated by the simulation into the transfer function. The damage to the structure was calculated using the rain-flow counting method, Goodman equation, Miner's rule, and S-N curve. The results confirmed that the wind speed generated at a specific time could not represent the wind speed that could occur during the design life of the structure.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.34 no.9
• /
• pp.1185-1191
• /
• 2010

Aged aircraft have several cracks as a results of long-term service, and these cracks affect the safety and decrease the rate of operation of the aircraft. To solve these problems, crack propagation analysis should be performed to determine the service life at fatigue critical location(FCL). It is, however, almost impossible to obtain the stress spectrum, which is crucial for crack propagation analysis of the FCLs of wing structure of aged aircraft. In this study, to analyze the fatigue crack propagation behavior at the FCL of an aged aircraft, first finite element analysis is performed for a 3D geometry model of the aircraft wing structure, which is obtained using CATIA based on the paper drawings. Then, the transfer function and stress-spectrum of the FCL are derived using the load factor data and the FEA results. Finally, the crack propagation rates of the FCL are evaluated using the commercial software, NASGRO 6.0.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2005.05a
• /
• pp.925-934
• /
• 2005

The dynamic response due to the unbalance and crack and the quasi-static response due to gravity are analytically derived based on the complex transfer matrix. The additional slope is expressed as function of the bending moment at crack position based on the fracture mechanics concept, and inversely the bending moment is expressed as function of the additional slope at the crack position. At each angle step during the shaft revolution, the additional slope and bending moment are calculated by an iterative method. The transient behavior is considered by introducing Fourier series expansion concept for the additional slope. Simulation is carried out for a simple rotor similar to those available in the literature and comparison of the basic crack behavior is shown. Using the additional slope, the cracked rotor behavior is explained with the crack depth increased: the magnitude of the additional slope increases and the closed crack duration during a revolution decreases as the crack depth increases. The direction of unbalance is also shown as a factor to affect the crack breathing. Whirl orbits are shown near the sub-critical speed ranges of the rotor.

• Proceedings of the KIEE Conference
• /
• 2001.07b
• /
• pp.1319-1321
• /
• 2001

The purpose of this study is to manufacture and test a thermoelectric generator which converts unused energy from close-at-hand sources, such as garbage incineration heat and industrial exhaust, to electricity. A manufacturing process and the properties of a thermoelectric generator are discussed before simulation the thermal stress and thermal properties of a thermoelectric module located between an aluminum tube and alumina plate. We can design the thermoelectric modules having the good properties of thermoelectric generation. Resistivity of thermoelectric module for thermoelectric generation consisting of 62 cells was $0.15{\sim}0.4{\Omega}$. The maximum power of thermoelectric generator using thermoelectric generation modules can be defined as temperature function, and in this case. It can be analogized the lineal relation between current and voltage characteristics as function of temperature. The thermoelectric generator using 32 thermoelectric modules was assembled with 32 directly connected modules that they constrained for two kinds of heat transfer tube with key joints.

• Transactions of the Korean Society for Noise and Vibration Engineering
• /
• v.15 no.10 s.103
• /
• pp.1137-1147
• /
• 2005

The dynamic response due to the unbalance and crack and the quasi-static response due to gravity are analytically derived based on the complex transfer matrix. The additional slope is expressed as function of the bending moment at crack position based on the fracture mechanics concept, and inversely the bending moment is expressed as function of the additional slope at the crack Position. At each angle step during the shaft revolution, the additional slope and bending moment are calculated by an iterativemethod. The transient behavior is considered by introducing Fourier series expansion concept for the additional slope. Simulation is carried out for a simple rotor similar to those available in the literature and comparison of the basic crack behavior is shown. Using the additional slope, the cracked rotor behavior is explained with the crack depth increased: the magnitude of the additional slope increases and the closed crack duration during a revolution decreases as the crack depth increases. The direction of unbalance is also shown as a factor to affect the crack breathing. Whirl orbits are shown near the sub-critical speed ranges of the rotor.

• Proceedings of the Korea Concrete Institute Conference
• /
• 2001.05a
• /
• pp.903-908
• /
• 2001

This paper deals with the estimation of the maximum flexural crack widths using minimum crack spacing for reinforced concrete members. The proposed method utilizes the conventional crack and bond-slip theories as well as bonding transfer length and effects of creep and shrinkage between the reinforcement and concrete. An analytical equation for the estimation of the maximum flexural crack width is formulated as a function of mean bond stress. The validity, accuracy and efficiency of the proposed method are established by comparing the analytical results with the experimental data and the major code specifications (e.g., ACI, CEB-FIP Model code, Eurocode 2, etc.). The analytical results of analysis presented in this paper indicate that the proposed method can be effectively estimated the maximum flexural crack width of the reinforced concrete members.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.26 no.11
• /
• pp.2466-2473
• /
• 2002

In twin roll strip casting process, the design of casting roll is the most important equipment for producing strip. Analyses of heat transfer and deformation for the casting roll are carried out by using the finite element program, ANSYS. Both the elastic deformation and the elasto-plastic deformation under a thermal load are considered in the analysis. Optimization to minimize the volume of roll is performed under the various thermal loads such as the heat flux and the roll speed. Design variables are defined by diameters and positions of the cooling hole in the roll , Although the thermal load remarkably varies, the design variables and objective function are found to be consistent.

• Proceedings of the Korean Nuclear Society Conference
• /
• 1996.05b
• /
• pp.227-232
• /
• 1996

The one-third calibrating relation by steady solution can cause large error when applied to an unsteady flow with large amplitude waves. Extended calibrating method, which can treat the normal convective contribution, is developed. The normal mass convective term is included into the 2-D mass transport equation by means of rms value and random function. The unknown shear rate is numerically determined by solving the 2-D mass transport equation inversely. This recovery method which predicts the unknown shear rate is constructed. It is found that it works very well without distortion. The inclusion of the normal convective term has a negligible effect on the mass transfer coefficient.