• Proceedings of the Korean Geotechical Society Conference
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• 2002.03a
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• pp.313-320
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• 2002

In accordance with the need of developing a methodology for the sludge reduction, this study investigates the effect of sonication on the dewaterability of the sewage sludge. The investigation involves laboratory experiments of the sewage sludge from Yongin Waste Treatment Plant. The Laboratory tests were conducted under a broad range of conditions including energy levels of ultrasonic waves, time for the treatment, pH, and effect of polymers. The results of the study show that sonication enhances the dewaterability significantly The degree of enhancement varies with sonication power, treatment time, the amount of sludge treated. The effect of sonication on the temperature and pH of the test specimens seems not to be significant. The polymer can be useful to enhance the effectiveness of ultrasound treatment.

• Journal of the Korean Society of Safety
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• v.22 no.1 s.79
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• pp.54-60
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• 2007

This paper describes typical design and construction practice for in-situ ground reinforcement technique using improved steel pipe pressure grouting. A case history is presented to illustrate the benefit gained by application of the technique. This technique was applied to cut slopes developed in the construction of auxiliary spillway of 00 dam. Applicable conditions, method of survey, slope stability analysis and construction are given in this parer. As for the construction method, a procedure is given and the main points are the control of construction work. As a result of the pull-out test, it is shown that seel pipe nailing is particularly useful for stabilizing rock slope.

• Proceedings of the Korean Society of Coastal and Ocean Engineers Conference
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• 1993.07a
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• pp.122-123
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• 1993

Bangkok Bar Channel is a unique approach channel to Bangkok(on Toi)Harbor that is the representative river port constructed along the river mouth of Chao Praya River. Various facilities are scattered along the both sides of the river between the river mouth and the bridge located about 50km upward. The construction of the channel began in 1951 and was completed in 1954. (omitted)

• Journal of the Korean Society of Safety
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• v.19 no.1
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• pp.94-101
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• 2004

In this study, composite laminated conical shells with ring stiffeners are analyzed. A versatile 4-node shell element which is useful for the analysis of conical shell structures is used. An improved flat shell element is established by the combined use of the addition of non-conforming displacement modes and the substitute shear strain fields. The proposed element has six degrees of freedom per node and permits an easy connection to other types(beam element) of Optimum location and optimum section properties of ring stiffeners are obtained. It is shown that the thickness of conical shell is reduced about 20% by optimum ring stiffeners.

• Journal of the Korean Society of Safety
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• v.26 no.4
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• pp.80-86
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• 2011

Structural optimization algorithm of steel box girder bridges using improved higher-order approximate reanalysis technique is proposed in this paper. The proposed approximation method is a generalization of the convex approximation method. The order of the approximate reanalysis for each function is analytically adjusted in the optimization process. This self-adjusted capability makes the approximate structural analysis values conservative enough to maintain the optimum design point of the approximate problem. The efficiency of proposed optimazation algorithm, compared with conventional algorithm, is successfully demonstrated in the steel box girder bridges. The efficiency and robustness of proposed algorithm is also demonstrated in practical steel box girder bridges.

• Journal of the Korean Society of Safety
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• v.23 no.6
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• pp.122-130
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• 2008

The cracking behavior of prestressed concrete members is important for the rational evaluation of PCC pipes. However, the test data on the cracking behavior of PCC pipes are very limited. The purpose of the present study is to investigate the cracking behavior of PCC pipes under different settlement conditions. In this paper, experimental test on the full scale model of PCC pipe was conducted and observed in order to study cracking load in PCC pipes. Based test and FEM analysis results, this paper also presents the cracking load prediction in PCC pipe. Based on the numerical analysis results performed in this research, the cracking behaviors of PCC pipe with the variation of the settlement conditions were evaluated.

• Journal of Korean Society of Water and Wastewater
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• v.19 no.3
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• pp.312-317
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• 2005

The 15 month pilot study was performed to investigate the effect of pretreatment by monochloramine ($NH_2Cl$) on the performance of RO membranes made of cellulose acetate (CA) and polyamide (PA). Both RO membranes experienced severe biological fouling without any pretreatment during the treatment of highly organic surface water in Florida, USA. Feed monochloramination at 5 mg/L significantly minimized productivity loss by effective control of biofouling. The CA membrane did not show any structural damages by monochloramine, while the PA membrane suffered from a gradual loss of membrane integrity by chlorine oxidation, which was characterized as an increase in productivity and a decrease in selectivity. The degradation of PA membrane increased with increasing monochloramine dose.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2005.11a
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• pp.301-305
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• 2005

This paper introduces a novel technique to detect and isolate the failures of multiple actuators connected to a system. Failure of actuator considered in this study could be any type of erroneous input that is different from commanded one. The interaction matrix technique allows the development of input-output equations that are only influenced by one target input. These input-output equations serve as an effective toot to monitor the integrity of each actuator regardless of the status of the other actuators. The method is capable of real-time actuator failure detection and isolation under any type of input excitation. The laboratory experiment using 8-bay NASA truss structure verifies the feasibility of the proposed method.

• Journal of the Korean Society for Nondestructive Testing
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• v.27 no.6
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• pp.483-500
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• 2007

Emerging sensor-based structural health monitoring (SHM) technology can play an important role in inspecting and securing the safety of aging civil infrastructure, a worldwide problem. However, implementation of SHM in civil infrastructure faces a significant challenge due to the lack of suitable sensors and reliable methods for interpreting sensor data. This paper reviews recent efforts and advances made in addressing this challenge, with example sensor hardware and software developed in the author's research center. It is proposed to integrate real-time continuous monitoring using on structure sensors for global structural integrity evaluation with targeted NDE inspection for local damage assessment.

• Journal of the Korean Society of Industry Convergence
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• v.12 no.4
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• pp.187-192
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• 2009

This study is performing a seismic analysis on the steel frames structure with dampers and analyzing the dynamic behavior in order to examine their efficiency and study the optimum dampers position to the seismic design steel structure. To improve the ability against an earthquake, this study performed the time history analysis. Controling an earthquake is the way to minimize the damage of the steel structure by dissipating input energy generated by an earthquake.