• Structural Engineering and Mechanics
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• v.57 no.4
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• pp.587-602
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• 2016

In structural reliability analysis, the response surface method is widely adopted because of its numerical efficiency. It should be understood that the response function must approximate the actual limit state function accurately in the main region influencing failure probability where it is evaluated. However, the size of main region influencing failure probability was not defined clearly in current response surface methods. In this study, the concept of sub-region of interest is constructed, and an improved response surface method is proposed based on the sub-region of interest. The sub-region of interest can clearly define the size of main region influencing failure probability, so that the accuracy of the evaluation of failure probability is increased. Some examples are introduced to demonstrate the efficiency and the accuracy of the proposed method for both numerical and implicit limit state functions.

• Journal of Auto-vehicle Safety Association
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• v.8 no.2
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• pp.24-29
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• 2016

A small-sized turbocharger is generally used in downsizing engine for various vehicles. When a centrifugal compressor, which is one of the crucial units of the turbocharger, is downsized, the compressor has much more possibilities of being damaged because of its high rotating speed, causing insecure structural soundness. Thus, it is of essential to study on the improvement of the structural soundness of a small-sized turbocharger. In this study, numerical analysis on the various blade geometries and mass flow rate of the compressor was performed using the commercial software ANSYS CFX. In addition, the evaluation on the structural soundness of a compressor impeller for respective cases was conducted using ANSYS Mechanical. As a result, it was shown that the compressor had higher efficiency with increasingly secured structural soundness.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2012.05a
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• pp.631-632
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• 2012

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2012.10a
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• pp.297-298
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• 2012

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 2003.03a
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• pp.294-301
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• 2003

The energy concept has been applied to the reported experimental results of six different structural steel connections to investigate the characteristics of system-dependent energy curve and energy absorption efficiency. For this the concept o( static and kinematic energy absorption efficiency has been defined. The present paper closes with the implication of the necessity of further investigation to extend the energy concept to reach the engineering practice.

• Structural Engineering and Mechanics
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• v.32 no.4
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• pp.489-500
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• 2009

The aim of this paper is to compare wavelet, kurtosis and pseudofractal based techniques for structural health monitoring in the presence of measurement noise. A detailed comparison and assessment of these techniques have been carried out in this paper through numerical experiments for the calibration of damage extent of a simply supported beam with an open crack serving as an illustrative example. The numerical experiments are deemed critical due to limited amount of experimental data available in the field of singularity based detection of damage. A continuous detectibility map has been proposed for comparing various techniques qualitatively. Efficiency surfaces have been constructed for wavelet, kurtosis and pseudofractal based calibration of damage extent as a function of damage location and measurement noise level. Levels of noise have been identified for each technique where a sudden drop of calibration efficiency is observed marking the onset of damage masking regime by measurement noise.

• Journal of Ocean Engineering and Technology
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• v.25 no.2
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• pp.101-107
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• 2011

In view of the importance of material reduction because of the jump in oil and steel prices, structural design studies for lifting lugs were performed. Hundreds of thousands of such lifting lug structures are needed every year for ship construction. A direct design study was reviewed using the developed design system to increase the design efficiency and provide a way of directly inserting a designer's decisions into the design system process. In order to understand the design efficiency and convenience of a lug structure, parametric studies for prototype lug shapes were performed using the developed design system. From these design studies, various patterns of design parameters for the lug structure according to changes in the main plate length were examined. Based on these parametric study results, design guides were developed for more efficiently suggesting structural data for enormous lug structures. Additionally, a more detailed structural analysis through local strength evaluations will be performed to verify the efficiency of the optimum structural design for a lug structure.

• Structural Engineering and Mechanics
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• v.19 no.3
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• pp.321-336
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• 2005

The structural feasibility of a variety of non-conventional sludge digesters, in the form of thin shells of revolution constructed in concrete, has formed the subject of investigation of a recent programme of research at the University of Cape Town. Such forms are usually known in the literature as "egg-shaped", and the advantages of these over conventional digesters of the wide-cylindrical type are now well-recognised: superior mixing efficiency, less accumulation of deposits at the bottom, easier removal of bottom deposits and surface crust, reduced heat losses, and so forth. With the aim of exploring the structural feasibility of various non-conventional forms for concrete sludge digesters, and making available usable analytical data and practical guidelines for the design of such thin shell structures, a number of theoretical studies have recently been undertaken, and these have covered conical assemblies, spherical assemblies and parabolic ogival configurations. The purpose of the present paper is to bring together the different analytical approaches employed in each of these studies, summarise the main findings in each case, draw comparisons among the various studied configurations with regard to structural efficiency and functional suitability, and make appropriate conclusions and recommendations.

• Korean Journal of Construction Engineering and Management
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• v.4 no.4 s.16
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• pp.137-144
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• 2003

Recently, the interest in a complex building increases rapidly in Korea. High-rise complex is not simply the combination of a residential apartment and a business office as previous but a building with the object of the convenience of the residents familiar with city-life style through adapting the high class life style and new residential culture to the business space, and the efficiency in using the limited building site in the town. This study presents an exploratory analysis focusing the structural system with the help of the extensive survey of the construction site in Korea, and aims a guideline for the structural design and construction of high rise complex. Through the survey, change and development in the design and the construction can be seen as the height and size of the complex grow. It is almost indispensable to design a structural system against lateral forces like earthquake or wind, which is usually measured by story drift ratio or story displacement. Improvement of the structural materials and their usages is also included for the efficiency of the structural system. Useful slab-beam system contributing to the decrease of the story height is still a concern.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2000.04b
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• pp.177-186
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• 2000

An improved multi-level（IML) optimization algorithm using automatic differentiation (AD) for multi-objective optimum design of framed structures is proposed in this paper. In order to optimize the steel frames under seismic load, two main objective functions need to be considered for minimizing the structural weight and maximizing the strain energy. For the efficiency of the proposed algorithm, multi-level optimization techniques using decomposition method that separately utilizes both system-level and element-level optimizations and an artificial constraint deletion technique are incorporated in the algorithm. And also to save the numerical efforts, an efficient reanalysis technique through approximated structural responses such as moments, frequencies, and strain energy with respect to intermediate variables is proposed in the paper. Sensitivity analysis of dynamic structural response is executed by AD that is a powerful technique for computing complex or implicit derivatives accurately and efficiently with minimal human effort. The efficiency and robustness of the IML algorithm, compared with a plain multi-level (PML) algorithm, is successfully demonstrated in the numerical examples.