• Proceedings of the Korean Institute of Building Construction Conference
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• 2011.05a
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• pp.187-189
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• 2011

Standard production unit system has been used as accumulated standard for the cost estimation of public construction projects. However, it is difficult to estimate reasonable cost due to adaptation of a uniform standard and reflect changes in the technology. The purpose of this study is to provide basic data for improvement of standard production unit system through the identifying problems and analysing its influence on enactment and/or revision work of standard production unit system.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2013.05a
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• pp.139-141
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• 2013

Construction industry has been participated in the effort for the reduction of environmental pollution such as introduction of green building certification, enactment of environment related regulation. However these efforts are focused on the design and maintenance phases of entire life cycle, construction phase that can occur intensive environmental impact in a short period is insufficient. Therefore this study aim to derive environmental management factors in construction phase and assess them using reliability analysis and factor analysis. As a results, the 20 factors was classified into 4 superordinate such as 'plan and supervision', 'environmental factor management', 'licensing management', 'surrounding environment management'.Based on result of this study, further study should be developed the checklist for effective environmental management in construction phase.

• Journal of Applied Reliability
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• v.17 no.4
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• pp.273-279
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• 2017

Purpose: Recently, Issues on security for vehicles are getting increased all around the world. Especially, hood panel needs to be thinner for the protection of pedestrians. But thinner panel makes durability get worse. So, it is needed to satisfy both of them. Methods: Durability effectiveness will be studied because properties and assembly allowance of over-slam bumper mostly affects durability of hood panel. Overlap of over-slam bumper can be made in production line and it can affect durability of spot welding in hood inner panel. Daguchi method is used to catch the condition in which load gets smaller and location, hardness and quantity of overlap are selected to be factors. Durability effectiveness is analyzed with the factors. Result: the mechanism that affects on spot welding is identified. The test was conducted in both open/close and driving condition and the relation between both conditions is analyzed. Conclusion: The test contributed to durability of hood panel with optimization of over-slam bumper.

• International conference on construction engineering and project management
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• 2009.05a
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• pp.847-855
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• 2009

While many studies on feasibility analysis for housing projects have been released, the main focus was on economic feasibility and factors related to developers were not clearly identified enough to be used in practice. In order to establish a feasibility analysis model for apartment development projects requested by developers in Korea, 31 driving factors behind projects' success were identified under seven different categories. Criterions of the each factor were also developed, and weight of each factor was assigned by applying the Analytical Hierarchy Process(AHP). Finally, based on the Monte Carlo simulation, the feasibility analysis model was established, providing probability distribution of project's grade. The model was applied to 12 housing projects to verify its reliability, and found that the model properly filtered projects that are unlikely to be profitable, indicating reasonable reliability of the model. The model can be a useful tool for contractors, especially with less experience in analyzing project development feasibility.

• Proceedings of the KWS Conference
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• 2002.10a
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• pp.266-272
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• 2002

This study reviews the factors controlling the weld metal cracking and shows the difference from those of HAZ cracking. It further reviews the recent progresses made in consumable design for improving the crack resistance in the high strength weld metal. Previously the controlling factors for weld metal cracking were regarded as weld metal strength, diffusible hydrogen and weld metal height. However an overall review presented in this article shows that the cold crack resistance can be improve significantly through the microstructural control and that an increase in tensile strength is not necessarily related to a decrease in the resistance to cold cracking.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.5 no.1
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• pp.43-53
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• 1985

This study proposes a reliability based design criteria for the steel bridge (H-beam, plate-girder and composite-beam), which is most common type of steel bridge, and also proposes the theoretical bases of nominal safety factors as well as load and rasistance factors based on the reliability theory. Major 2nd moment reliability analysis and design theories including both Cornell's MFOSM (Mean First Order 2nd Moment) Methods and Lind-Hasofer's AFOSM(Advanced First Order 2nd Moment) Methods are summarized and compared, and it has been found that Lind-Hasofer's approximate and an approximate Log-normal type reliability formula are well suited for the proposed reliability study. A target reliability index (${\beta}_0=3.5$) is selected as an optimal value considering our practice based on the calibration with the safety pravisions of the current steel bridge design code. Galambo's theory is used for the derivation of the algorithm for the evaluation of uncertainties associated with resistences by LRFD Format and SGST Format, whereas the magnitude of the uncertainties associated with load effects are chosen primarily by considering our level of practice. It may be concluded that the proposed LRFD reliability based design provisions for the steel highway bridge give more rational design than the current standard code for steel highway bridge.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.2 no.3
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• pp.87-99
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• 1982

This study proposes a reliability based design criteria for the R.C. superstructures of highway bridges. Uncertainties associated with the resistance of T or rectangular sections are investigated, and a set of appropriate uncertainties associated with the bridge dead and traffic live loads are proposed by reflecting our level of practice. Major 2nd moment reliability analysis and design theories including both Cornell's MFOSM(Mean First Order 2nd Moment) Methods and Lind-Hasofer's AFOSM(Advanced First Order 2nd Moment) Methods are summarized and compared, and it has been found that Ellingwood's algorithm and an approximate log-normal type reliability formula are well suited for the proposed reliability study. A target reliability index (${\beta}_0=3.5$) is selected as an optimal value considering our practice based on the calibration with the current R.C. bridge design safety provisions. A set of load and resistance factors is derived by the proposed uncertainties and the methods corresponding to the target reliability. Furthermore, a set of nominal safety factors and allowable stresses are proposed for the current W.S.D. design provisions. It may be asserted that the proposed L.R.F.D. reliability based design criteria for the R.C. highway bridges may have to be incorporated into the current R.C. bridge design codes as a design provision corresponding to the U.S.D. provisions of the current R.C. design code.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.42 no.3
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• pp.299-309
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• 2022

This paper presents a new class of the vehicular live load factor for a reliability-based bridge design code. The significance of the current vehicular live load factor of 1.8 is investigated based on the return period of the vehicular live load and the design life of a bridge. It is shown that the current vehicular live load factor corresponds to a return period of 6.7 million years for a 100-year design life, which seems to be unrealistic in an engineering sense, and that the target reliability of 3.72 is set to too high without any reasoning for the gravitational load-governed limit state compared with that of the other limit states. In case the same return period as the design wind velocity or the ground acceleration is employed for the vehicular live load, the corresponding vehicular live load factor becomes around 1.15, and the target reliability index for the return period may be selected as 2.0 or 2.5 depending on the governing load effect. The complete sets of the load-resistance factors for the proposed target reliability indices are evaluated through optimization.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.9 no.2
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• pp.37-43
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• 2009

Reliability should be assured to support the stable ubiquitous sensor network services in wireless sensor networks. Data transmission reliability is the most important one in the reliability factors in USN. When we consider the wireless communication environment of sensor networks, data transmission reliability requires the performance improvement. For this, this paper introduces the method that can handle the reliability and the performance together. The proposed scheme uses the self relay signal between sensor nodes to deliver the ACK and the next data is scheduled to be sent on acceptance of this self relay signal. For the evaluation of the performance improvement, the analysis and the simulation have been done.

• Structural Engineering and Mechanics
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• v.49 no.2
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• pp.203-223
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• 2014

The extensive use of prestressed reinforced concrete (PSC) highway bridges in marine environment drastically increases the sensitivity to both fatigue-and corrosion-induced damage of their critical structural components during their service lives. Within this scenario, an integrated method that is capable of evaluating the fatigue reliability, identifying a condition-based maintenance, and predicting the remaining service life of its critical components is therefore needed. To accomplish this goal, a procedure for fatigue reliability prediction of PSC highway bridges is proposed in the present study. Vehicle-bridge coupling vibration analysis is performed for obtaining the equivalent moment ranges of critical section of bridges under typical fatigue truck models. Three-dimensional nonlinear mathematical models of fatigue trucks are simplified as an eleven-degree-of-freedom system. Road surface roughness is simulated as zero-mean stationary Gaussian random processes using the trigonometric series method. The time-dependent stress-concentration factors of reinforcing bars and prestressing tendons are accounted for more accurate stress ranges determination. The limit state functions are constructed according to the Miner's linear damage rule, the time-dependent S-N curves of prestressing tendons and the site-specific stress cycle prediction. The effectiveness of the methodology framework is demonstrated to a T-type simple supported multi-girder bridge for fatigue reliability evaluation.