• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.18 no.1
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• pp.39-46
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• 1982

The author has developed the computer program in order to calculate the optimum alignment condition of marine propulsion shafting by linear programming method. The input of program was calculated by the matrix method of three-moment. He compared the calculated values with the experimental values measured by the strain gage on the model shaft, and the values of calculation on actual propulsion shafting with those of Det norske Veritas. The computer program of optimum alignment has been applied to the actual shaft. The results obtained are as follows: 1. To obtain the reaction of supporting points in the straight line necessary to the optimum alignment and the reaction influence number, after the computer program had been developed and then adapted, the result of experimental values and calculated values agreed with each other and the values of the actual shaft were also approximately similar to the values of other program. 2. In this paper, the measuring method on model shaft by strain gage can be effectively used at the time of adjusting alignment condition of actual shaft. 3. The supporting bearing should be considerably readjusted to the vertical direction in order to satisfy some limited condition.

• Steel and Composite Structures
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• v.22 no.1
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• pp.113-139
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• 2016

The nonlinear seismic responses of steel buildings with perimeter moment resisting frames (PMRF) and interior gravity frames (IGF) are estimated, modeling the interior connections first as perfectly pinned (PPC), and then as partially restrained (PRC). Two 3D steel building models, twenty strong motions and three levels of the PRC rigidity, which are represented by the Richard Model and the Beam Line Theory, are considered. The RUAUMOKO Computer Program is used for the required time history nonlinear dynamic analysis. The responses can be significantly reduced when interior connections are considered as PRC, confirming what observed in experimental investigations. The reduction significantly varies with the strong motion, story, model, structural deformation, response parameter, and location of the structural element. The reduction is larger for global than for local response parameters; average reductions larger than 30% are observed for shears and displacements while they are about 20% for bending moments. The reduction is much larger for medium- than for low-rise buildings indicating a considerable influence of the structural complexity. It can be concluded that, the effect of the dissipated energy at PRC should not be neglected. Even for connections with relative small stiffness, which are usually idealized as PPC, the reduction can be significant. Thus, PRC can be used at IGF of steel buildings with PMRF to get more economical construction, to reduce the seismic response and to make steel building more seismic load tolerant. Much more research is needed to consider other aspects of the problem to reach more general conclusions.

• Geomechanics and Engineering
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• v.29 no.4
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• pp.471-486
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• 2022

The effect of segmental joints is one of main importance for the segmental lining design when tunnels are excavated by a mechanized process. In this paper, segmental tunnel linings are analyzed by two numerical methods, namely the Beam-Spring Method (BSM) and the Solid-Interface Method (SIM). For this purpose, the Tehran Subway Line 6 Tunnel is considered to be the reference case. Comprehensive 2D numerical simulations are performed considering the soil's calibrated plastic hardening model (PH). Also, an advanced 3D numerical model was used to obtain the stress relaxation value. The SIM numerical model is conducted to calculate the average rotational stiffness of the longitudinal joints considering the joints bending moment distribution and joints openings. Then, based on the BSM, a sensitivity analysis was performed to investigate the influence of the ground rigidity, depth to diameter ratios, slippage between the segment and ground, segment thickness, number of segments and pattern of joints. The findings indicate that when the longitudinal joints are flexible, the soil-segment interaction effect is significant. The joint rotational stiffness effect becomes remarkable with increasing the segment thickness, segment number, and tunnel depth. The pattern of longitudinal joints, in addition to the joint stiffness ratio and number of segments, also depends on the placement of longitudinal joints of the key segment in the tunnel crown (similar to patterns B and B').

• Geomechanics and Engineering
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• v.35 no.5
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• pp.525-538
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• 2023

The development of a city is closely linked to the construction and operation of its subway system. However, constructing a new subway tunnel under an existing station is an extremely complex task, and the deformation characteristics and mechanical behavior of the new subway tunnel during the excavation process can greatly impact the normal operation of the existing station. Although the previous studies about the case of underpass engineering have been carried out, there is limited research on the condition of a newly-built subway tunnel that closely undercrossing an existing station with zero distance between them. Therefore, this study analyzes the deformation law and mechanical behavior characteristics of the preliminary lining of the underpass tunnel during the excavation process based on the real engineering case of Chengdu Metro Line 8. This study also makes an in-depth comparison of the influence of different excavation methods on this issue. Finally, the accuracy of numerical simulation is verified by comparing it with on-site result. The results indicate that the maximum bending moment mainly occurs at the floor slab of the preliminary lining, while that of the ceiling is small. The stress state at the ceiling position is less affected by the construction process of the pilot tunnel. Compared to the all-in-one excavation method, although the process of partial excavation method is more complicated, the deformation of preliminary lining caused by it is basically less than the upper limit value of the standard, while that of the all-in-one excavation method is beyond standard requirements.

• Journal of the Korea institute for structural maintenance and inspection
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• v.11 no.1
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• pp.141-152
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• 2007

Considering uncertainties of random input data, it is more reasonable to use probabilistic method than the conventional deterministic method for the design of structures or for the assessment of the responses of structures, which are designed as safe even under extreme loads. Therefore, to assess the quantitative effects of the constructed cable stayed bridge by the input random variables, a sensitivity analysis is studied. Using perturbation method, an analysis program is developed for the iterative probabilistic finite element analyses and sensitivity analyses of the cable stayed bridge, except the initial shape analysis. Monte-Carlo Simulations were used for the verification of the developed program. The results of sensitivity analysis shows the governing effects of external loads. Because the results also provide the sensitive effects of the stiffness of members and the magnitudes of prestressing force of cables, the developed

• The Journal of the Acoustical Society of Korea
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• v.41 no.4
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• pp.435-445
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• 2022

In this study, the reverberation of a bistatic sonar operated in southeastern coast in the East Sea in July 2020 was analyzed. The reverberation sensor data were collected through an LFM sound source towed by a research vessel and a horizontal line array receiver 1 km to 5 km away from it. The reverberation sensor data was analyzed by various methods including geo-plot after signal processing. Through this, it was confirmed that the angle reflected from the sound source through the scatterer to the receiver has a dominant influence on the distribution of the reverberation sound, and the probability distribution characteristics of bistatic sonar reverberation varies for each beam. In addition, parametric factors of K distribution and Rayleigh distribution were estimated from the sample through moment method estimation. Using the Kolmogorov-Smirnov test at the confidence level of 0.05, the distribution probability of the data was analyzed. As a result, it could be observed that the reverberation follows a Rayleigh probability distribution, and it could be estimated that this was the effect of a low reverberation to noise ratio.

• Korean Security Journal
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• no.28
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• pp.103-130
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• 2011

This study is the research of enterprise security for raising the profitability and stability of Korean companies in global business environment and strategic cooperation of business. As the scientific technology gets complicated as day goes by and new competitors appear regardless the border in the modern business environment, the situation happens frequently which the huge company hands over their market to the new one armed with the innovative thinking overnight. To survive such new environment, the answer is the change of paradigm regarding business management method at the new point of view. With the low level of security risk management of Korean companies which stick to old habit, the security management which helps the companies secure profits is not affordable. The global village where the population of 7 billions live in 21st century is facing up to the rapid ecological adaptation. The rapid change of climatic environment creates the hundreds of thousands of sufferers in a moment, and we have been watching the millions of livestock are buried alive due to new contagious disease everyday. Such change encourages the humans in global village to change the basic way of living. The business ecosystem which is the basic root for economic life cannot be an exception. To survive the business environment of 21st century, the security risk management at management level is required and the reporting line of companies should be established newly for raising business competing power through security risk management. The companies should bear in mind that they can be disappeared into our old memories overnight if they are not sensitive to the changing environment. Out of new risks for the modern companies, the field especially Korean companies are dealing easily is the security risk. Not like past, the security risk which's size is much more massive and its propagation velocity is very fast is the one of important business risks which the management should take care. Out of security risks which influence on the modern companies significantly, the brand of companies, protection of their reputation, continuity of production and operation and keeping customer's trust are prior to the others. This study offered the suggestion regarding enterprise security and the strategic cooperation of business to deal with such security risk effectively.