• KSCE Journal of Civil and Environmental Engineering Research
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• v.31 no.4A
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• pp.323-329
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• 2011

Most current design codes of concrete structures adopt the partial safety factor format to assure the proper safety margin or reliability against various limit states as a practical design tool. The safety factors, load and resistance factors and so on, are determined based on the theory of structural reliability, which takes into account the statistical uncertainties of both loads and resistances. The establishment of statistical models for load and resistance should be preceded the application of reliability theory. In this paper, especially the influence of the statistical variations of resistance models, which are described in terms of strength of concrete, strength of reinforcements and sectional dimensions and so on, are examined and the probabilistic models for resistance of reinforced concrete members were developed. The statistical data were collected on local tests and experiments in Korea and the Monte Carlo simulation (MCS) technique was used. The results of this paper may be useful and valuable in calibration of design code in this country.

• Journal of the Korea Concrete Institute
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• v.14 no.6
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• pp.900-909
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• 2002

Fibers play a role to increase the tensile strength and cracking resistance of concrete structures. The post cracking behavior must be clarified to predict cracking resistance of fiber reinforced concrete. The purpose of this study is to develop a realistic analysis method for the post cracking behavior of synthetic fiber reinforced concrete members. For this purpose, the cracked section is assumed to behave as a rigid body and the pullout behavior of single fiber is employed. A probabilistic approach is used to calculate effective number of fibers across crack faces. The existing theory is compared with test data and shows good agreement. The proposed theory can be efficiently used to describe the load-deflection behavior, moment-curvature relation, load-crack width relation of synthetic fiber reinforced concrete beams.

• Earthquakes and Structures
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• v.14 no.3
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• pp.249-259
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• 2018

This paper aims to assess the seismic risk of a plane moment-resisting frames (MRFs) consisting of concrete-filled double skin steel tube (CFDST) columns and I-section steel beams. Firstly, three typical limit performance levels of CFDST structures are determined in accordance with the cyclic tests of seven CFDST joint specimens with 1/2-scaled and the limits stipulated in FEMA 356. Then, finite element (FE) models of the test specimens are built by considering with material degradation, nonlinear behavior of beam-column connections and panel zones. The mechanical behavior of the concrete material are modeled in compression stressed condition in trip-direction based on unified strength theory, and such numerical model were verified by tests. Besides, numerical models on 3, 6 and 9-story CFDST frames are established. Furthermore, the seismic responses of these models to earthquake excitations are investigated using nonlinear time-history analyses (NTHA), and the limits capacities are determined from incremental dynamic analyses (IDA). In addition, fragility curves are developed for these models associated with 10%/50yr and 2%/50yr events as defined in SAC project for the region on Los Angeles in the Unite State. Lastly, the annual probabilities of each limits and the collapse probabilities in 50 years for these models are calculated and compared. Such results provide risk information for the CFDST-MRFs based on the probabilistic risk assessment method.

• Journal of Korea Water Resources Association
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• v.46 no.8
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• pp.795-805
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• 2013

Drought is one of the severe natural disasters and it can profoundly affect our society and ecosystem. Also, it is a very important variable for water resources planning and management. Therefore, the drought is analyzed in this study to understand the drought distribution and trend. The Standard Precipitation Index (SPI) is estimated using precipitation data obtained from 55 rain gauge stations in South Korea and the SPI based drought variables such as drought duration and drought severity were defined. Drought occurrence and joint probabilistic analysis for SPI based drought variables were performed with run theory and copula functions. And then the return period and spatial distribution of droughts on the South Korea was estimated. As the results, we have shown that Gongju and Chungju in Chungcheong-do and Wonju, Inje, Jeongseon, Taebeak in Gangwon-do have vulnerability to droughts.

• International Journal of Control, Automation, and Systems
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• v.3 no.4
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• pp.509-523
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• 2005

We are developing a novel framework, PRIDE (PRediction In Dynamic Environments), to perform moving object prediction (MOP) for autonomous ground vehicles. The underlying concept is based upon a multi-resolutional, hierarchical approach which incorporates multiple prediction algorithms into a single, unifying framework. The lower levels of the framework utilize estimation-theoretic short-term predictions while the upper levels utilize a probabilistic prediction approach based on situation recognition with an underlying cost model. The estimation-theoretic short-term prediction is via an extended Kalman filter-based algorithm using sensor data to predict the future location of moving objects with an associated confidence measure. The proposed estimation-theoretic approach does not incorporate a priori knowledge such as road networks and traffic signage and assumes uninfluenced constant trajectory and is thus suited for short-term prediction in both on-road and off-road driving. In this article, we analyze the complementary role played by vehicle kinematic models in such short-term prediction of moving objects. In particular, the importance of vehicle process models and their effect on predicting the positions and orientations of moving objects for autonomous ground vehicle navigation are examined. We present results using field data obtained from different autonomous ground vehicles operating in outdoor environments.

• Journal of KIISE:Computer Systems and Theory
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• v.34 no.10
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• pp.502-510
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• 2007

Private Matching is a problem of computing the intersection of private datasets of two parties. One could envision the usage of private matching for Insurance fraud detection system, Do-not-fly list, medical databases, and many other applications. In 2004, Freedman et at. [1] introduced a probabilistic solution for this problem, and they extended it to malicious adversary model and multi-party computation. In this paper, we propose a new deterministic protocol for private matching with perfect correctness. We apply this technique to adversary models, achieving more reliable and higher speed computation.

• Korean Journal of Construction Engineering and Management
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• v.4 no.4 s.16
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• pp.201-211
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• 2003

Considering about construction projects characteristics, there Is an existing uncertainty which causes inaccuracy or invalidity under decision making situation. Therefore, cost risk analysis of numerous construction projects are Inclined to depend on expert's experiences and subjective judgements. In Korean domestic construction works, however, there is no reasonable method or process for applying subjective elements. Only probabilistic analysis using objective calculation are being used now. This research suggests a cost risk analysis method to analyze quantitatively Cost Impact by risk, and it appraises expert's subjective elements for the purpose of enhancing validity of cost estimation. Moreover, a new cost risk analysis method is introduced for providing convenient user interface in practical business.

• Journal of Electrical Engineering and Technology
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• v.8 no.6
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• pp.1615-1625
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• 2013

Modelling and simulating the wind power intermittent behaviour are the basis of the planning and scheduling studies concerning wind power integration. The wind power outputs are evidently correlated in space and time and bring challenges in characterizing their behaviour. This paper provides a methodology to model and simulate the clustered wind power considering its spatio-temporal correlations using the theory of copula. The sampling approach captures the complex spatio-temporal connections among the wind farms by employing a conditional density function calculated using multidimensional copula function. The empirical study of real wind power measurement shows how the wind power outputs are correlated and how these correlations affect the overall uncertainty of clustered wind power output. The case study validates the simulation technique by comparing the simulated results with the real measurements.

• Structural Engineering and Mechanics
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• v.62 no.3
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• pp.365-372
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• 2017

Reliability analysis is a probabilistic approach to determine a safety level of a system. Reliability is defined as a probability of a system (or a structure, in structural engineering) to functionally perform under given conditions. In the 1960s, Basler defined the reliability index as a measure to elucidate the safety level of the system, which until today is a commonly used parameter. However, the reliability index has been formulated based on the pivotal assumption which assumed that the considered limit state function is normally distributed. Nevertheless, it is not guaranteed that the limit state function of systems follow as normal distributions; therefore, there is a need to define a new reliability index for no-normal distributions. The main contribution of this paper is to define a sophisticated reliability index for limit state functions which their distributions are non-normal. To do so, the new definition of reliability index is introduced for non-normal limit state functions according to the probability functions which are calculated based on the convolution theory. Eventually, as the state of the art, this paper introduces a simplified method to calculate the reliability index for non-normal distributions. The simplified method is developed to generate non-normal limit state in terms of normal distributions using series of Gaussian functions.

• Smart Structures and Systems
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• v.16 no.2
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• pp.367-382
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• 2015

This paper aims to conduct the reliability-based assessment of the welded joint in the orthotropic steel bridge deck by use of a mesh-insensitive structural stress (MISS) method, which is an effective numerical procedure to determine the reliable stress distribution adjacent to the weld toe. Both the solid element model and the shell element model are first established to investigate the sensitivity of the element size and the element type in calculating the structural stress under different loading scenarios. In order to achieve realistic condition assessment of the welded joint, the probabilistic approach based on the structural reliability theory is adopted to derive the reliability index and the failure probability by taking into account the uncertainties inherent in the material properties and load conditions. The limit state function is formulated in terms of the structural resistance of the material and the load effect which is described by the structural stress obtained by the MISS method. The reliability index is computed by use of the first-order reliability method (FORM), and compared with a target reliability index to facilitate the safety assessment. The results achieved from this study reveal that the calculation of the structural stress using the MISS method is insensitive to the element size and the element type, and the obtained structural stress results serve as a reliable basis for structural reliability analysis.