• Journal of the Korean GEO-environmental Society
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• v.13 no.11
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• pp.43-50
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• 2012

In this research, the value of consolidation index was investigated. The range of the investigated standard deviation was analyzed and the deviation based settlement was calculated. Also, the compression index, which is the effect of the uncertainty in the ground was analyzed using the flimsy ground construction method. The settlement behavior in each embankment compaction stage was analyzed by applying the precompression load method, drainage expediting method, and displacement method through numerical analysis. In addition to the above, the settlement behavior was studied by analyzing the Piled Raft method which is stable for long term settlement. As a result, the final settlement amount based on average analysis results was that the settlement based on each of the average interpretation value, mean value of the maximum and minimum value and average compression index was different. The result of the comparison shows the difference in variation coefficient by the difference in time. Amongst them, the Piled Raft method shows the most consistent variation coefficient regardless of time and it also was least affected by the compression index of uncertainty.

• Journal of the Korea Concrete Institute
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• v.26 no.3
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• pp.343-350
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• 2014

A probabilistic construction stage analysis using the Monte Carlo Simulation was performed to address the effects of uncertainty regarding the material properties, environmental factors, and applied forces. In the previous research, creep and shrinkage were assumed to be completely independent random variables. However, because of the common influencing factors in the material models for the creep and shrinkage estimation, strong correlation between creep and shrinkage can be presumed. In this paper, an Monte Carlo Simulation using CEB-FIB creep and shrinkage equations were performed to actually evaluate the correlation coefficient between two phenomena, and then another Monte Carlo Simulation to evaluate the statistical properties of axial strain affected by partially correlated random variables including the material properties, environmental factors, and applied forces. The results of Monte Carlo Simulation were compared with measured strains of a column on a first story in a 58-story building. Comparison indicated that the variation due to the uncertainty related with the material properties were most severe. And measured strains was within the range of mean+standard deviation.

• Journal of the Korean Geotechnical Society
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• v.33 no.4
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• pp.17-24
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• 2017

Shear wave velocity (or shear modulus) of rock filled zone of CFRD is very important factor in the evaluation of performance of CFRD under the load such as earthquake. A shear wave velocity profile can be determined by surface wave method but this profile has been uncertainty caused by spatial variation of material property in rock filled zone. This uncertainty in shear wave velocity profile could be evaluated by the reliability based analysis which uses a coefficient of variation of material property to consider uncertainty caused by spatial variation of material property. In this paper, the possible 600 shear wave velocity profiles in rock filled zone of CFRD were generated using the method based on harmonic wavelet transform and 8 shear wave velocity profiles by HWAW method in the field, and the coefficients of variation of shear wave velocity with depth were evaluated for the rock filled zone of CFRD in Korea.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.17 no.4
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• pp.443-449
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• 2004

Methods for mixing variable types of steel fibers have been developed recently to suppress outbreak of crack or to control the width of crack and improve the load resistible capacity at the same time. On the other hand, uncertainty by complex nature of destruction dynamics of steel fiber reinforced concrete(SFRC) is included. In this study, analysis of reliance considering uncertainty of SFRC beam is done. For this, intensity limit state model was proposed. Moreover, characteristic values about almost every kinds of probability variables were collected and presented according to home and foreign references. Process of improving uncertainty from the result of experiments by Bayseian updating method is also proposed on the purpose of offering better statistical characteristic values with more data in the new future. Fatigue fracture probability equation is proposed and needed statistical characteristic values were presented to analyze fatigue reliance

• Journal of the Korean Society of Safety
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• v.34 no.5
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• pp.87-94
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• 2019

This study deals with the reliability analysis approach of the temporary structure that can consider the uncertainty in rotational stiffness at the joints of the members, for which the semi-rigid connections are modelled as rotational spring and its coefficient is treated as a random variable following uniform distribution. In addition, this study introduces a computational procedure of the effective length coefficient for more accurate buckling load according to connection conditions of the supporting members attached to the joint. From the results of this study, it can be seen that the failure probability of the joint-hinge model (Case 1) presented in the design standard is higher than that of the practical model (Case 5) considering the rotational stiffness at the joints. This implies that the design standard leads to a conservative design of the temporary structure. The results also confirmed that the failure probability of the vertical member, i.e., the most critical member, can be further reduced when the base connection is provided with a fixed end. The comparative results between FORM, SORM and MCS further demonstrated that FORM can have a high level of numerical efficiency while ensuring the accuracy of the solution, compared with SORM and MCS. Based on these results, the proposed approach can be used as an accurate and efficient reliability analysis method of the three dimensional temporary structure.

• Journal of the Korean Geosynthetics Society
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• v.18 no.4
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• pp.205-214
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• 2019

Load and resistance factor design of mound breakwater against circular failure was developed in this study. To achieve the goal, uncertainties of parameters of soils, mound, and concrete cap were determined. Eight design cases of domestic mound breakwaters were collected and analyzed. Monte Carlo Simulation was implemented to determine the most critical slip surfaces of the design cases. Using the results of Monte Carlo Simulation, First-Order Reliability Method (FORM) was used to perform reliability analyses. Optimal load and resistance factors were calculated using the reliability analysis results and final load and resistance factors were proposed based on the calculated optimal factors.

• Journal of Korean Society of Steel Construction
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• v.11 no.1 s.38
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• pp.43-54
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• 1999

The divergence connection between steel circular tubes is widely used in such structures as factory facilities, steel circular hollow section truss, and off-shore tower. Steel circular hollow section (SCHS) have close section, and it makes their per-unit production expense higher than open sectioned products like L-shape, H-shape steels, but the sectional resistance of SCHS against vertical compression and torsion is very high. Despite the structural merits of SCHS, however, many engineers dislike to use them in their design because of uncertainty regarding the stress distribution and deformation behavior at their connections. Therefore, this thesis dealt with X-type connections, the most common forms of connection, and studied their load-deformation relationship. It observed how to show the load-deformation relationship at steel circular tube connections according to the diameter-thickness ratio (D/T) of the chord and diameter of branch-diameter of chord ratio (d/D) and suggested prediction yield load using by ring analysis method.

• Journal of Korean Society on Water Environment
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• v.26 no.1
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• pp.168-176
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• 2010

This study proposes the improvement of the present Total Maximum Daily Load (TMDL) management system of MOE (Ministry of Environment). The margin of safety (MOS) is calculated by a method using standard error and a method using variability and uncertainty. The allocation of pollutant loads are calculated using three methods, equal load reduction method, equal percent removal method and method using equity standards. This study applied the improved TMDL management system to the Anyangcheon watershed. Since MOS varies from 12% to 44% due to the high variability of measured and simulated data, it must not be ignored in the TMDL. The method using equity standards is the most proper in this application since the others produced unrealistic allocations. Area, runoff, water use quantity, population and budget are considered for equity standards. This study shows that this allocation method can be also applicable for the administrative units as well as the sub-watersheds. Finally, Hydrologic Simulation Program-FORTRAN (HSPF) with the allocated pollutant load was used to confirm whether it satisfy the water quality standard or not. This study will be helpful to improve the MOS and allocation system TMDL in the future.

• Korean Journal of Environmental Agriculture
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• v.31 no.1
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• pp.16-23
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• 2012

BACKGROUND: To improve the Daechung reservoir water quality, a quantitative estimation of the delivery load from upper watershed need to be conducted prior to others. To do so, an intensive monitoring is necessary because of the complexity and uncertainty of the delivery load from uppper watershed. However, intensive monitoring need to invest much time, cost, and effort. So, many researcher have developed an equation to estimate the delivery loads. But, relatively little research has been conducted on the applicability of pre-developed equation using other sites. Therefore, the objective of this study was to evaluate application of the equation for BOD, T-N and T-P delivery load. METHODS AND RESULTS: To verify the applicability of the equation, the following equation was used; Delivery loads(kg/day)=generated pollutant loads${\times}(1-{\alpha}){\times}$(daily outflow/${\beta})^{\gamma}$. The equations could be calculated the daily delivery loads of streams without any data of water quality, only with the data of daily runoff of study sites. The equations were applied to Youngdogcheon, Chogangcheon, Bocheongcheon, Sookcheon to examine its applicability using monitoring data. The results showed that the estimated delivery loads were in a good agreement with the observed data and indicated reasonable applicability of the equations. CONCLUSION(s): Overall, the equations were satisfactory in estimation of delivery loads at upper watershed of the Daechung reservoir. Therefore, the equations could be contributed to better water quality management in the Daechung reservoir.

• Journal of the Korean Geotechnical Society
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• v.30 no.8
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• pp.25-37
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• 2014

In load and resistance factor design (LRFD) method, resistance factors are typically calibrated using resistance bias factors obtained from either only the data within ${\pm}2{\sigma}$ or the data except the tail values of an assumed probability distribution to increase the reliability of the database. However, the data selection approach has a shortcoming that any low-quality data inadvertently included in the database may not be removed. In this study, a data quality evaluation method, developed based on the quality of static load test results, the engineering characteristics of in-situ soil, and the dimension of aggregate piers, is proposed for use in constructing database. For the evaluation of the method, a total 65 static load test results collected from various literatures, including static load test reports, were analyzed. Depending on the quality of the database, the comparison between bias factors, coefficients of variation, and resistance factors showed that uncertainty in estimating bias factors can be reduced by using the proposed data quality evaluation method when constructing database.