• Korean Journal of Construction Engineering and Management
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• v.5 no.6 s.22
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• pp.170-178
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• 2004

Public construction companies have strictly followed a rule that they should not work in the wet area such as structural frame for a certain period during the winter season. It is usually known that the non-working period during the winter causes increase of the project duration, and the project cost escalation. Also, it makes negative effects on national economy because it reduces workers income. Therefore, the site work for the structural frame should be performed even during the whiter season. But the site work for the structural frame during that period cannot proceeds in the same way as during other periods, and requires a different method for estimating project duration. Through an analysis of time scheduling mechanism, actual working days are obtained for 1 cycle of typical floors in the structural frame during these periods, and non-working days of 5 years average are calculated based on calendar day using data of 5 years weather forecasts for that season. This study proposes an optimized way of estimating project duration for 1 cycle of typical floors in the structural frame during these periods. This estimating method uses the combined actual working days and non-working days of 5 years' average, and the estimated results are confirmed by being compared with field data. This study is expected to be used in estimating the construction duration of the structural frame during the winter season.

• International conference on construction engineering and project management
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• 2015.10a
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• pp.248-251
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• 2015

High injury and fatality rates remain a serious problem in the construction industry. Many construction injuries and fatalities can be prevented if workers can recognize potential hazards and take actions in time. Many efforts have been devoted in improving workers' ability of hazard recognition through various safety training and education methods. However, a reliable approach for evaluating this ability is missing. Previous studies in the field of human behavior and phycology indicate that the visual focus of attention (VFOA) is a good indicator of worker's actual focus. Towards this direction, this study introduces an automated approach for estimating the VFOA of equipment operators using a head orientation-based VFOA estimation method. The proposed method is validated in a virtual reality scenario using an immersive head mounted display. Results show that the proposed method can effectively estimate the VFOA of test subjects in different test scenarios. The findings in this study broaden the knowledge of detecting the visual focus and distraction of construction workers, and envision the future work in improving work's ability of hazard recognition.

• Korean Journal of Construction Engineering and Management
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• v.19 no.3
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• pp.3-10
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• 2018

In recent years, mechanized construction has become commonplace due to increases in the scale and complexity of construction, and construction machinery is a major factor in successful construction. However, even though the proportion of construction machinery is increasing, analysis of the work capacity of construction machinery is inadequate. In addition, since the standards for all construction machines are currently not defined in quantity-per-unit, the construction period is arbitrarily applied according to the operator at the time of the construction plan. As a result, the construction period of the actual construction is insufficient, and rushed work or construction delays occur. Therefore, in this study, in order to calculate the construction period of the piling work of the pile driver used in the PRD method more accurately than the existing method, the formula for calculating the time required for the piling work of the pile driver was established by collecting piling time data from the daily task reports through the field survey. If the precise construction period of piling work is estimated based on the results of this study, it will be possible to prevent the rushed work and construction delays that occur due to the short construction period.

• Korean Journal of Construction Engineering and Management
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• v.12 no.6
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• pp.42-53
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• 2011

This study is to present a method of compiling consistently accurate construction cost estimates in minimum of time. There are two kind of applications for estimating system based on quantity-per-unit and the daily work-crew. The former system is still applied 45% as a estimating method to construction job site by the second half of 2010. However, it is necessary for quantity-per-unit to complement the defect of standard integrating specification and improve the integrating method to the various construction conditions. The later system is intended to represent a standard or basic core which can be adopted in many type of construction estimating used across the wide variety of construction in advanced countries. In this study daily work-crew based on productivity is applied to the representative B.O.Q Item in road project. These results are compared to productivity of Japan and U.S.A estimated under the similar circumstances.

• Computers and Concrete
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• v.32 no.3
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• pp.263-286
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• 2023

Experimenting with concrete to determine its compressive and tensile strengths is a laborious and time-consuming operation that requires a lot of attention to detail. Researchers from all around the world have spent the better part of the last several decades attempting to use machine learning algorithms to make accurate predictions about the technical qualities of various kinds of concrete. The research that is currently available on estimating the strength of concrete draws attention to the applicability and precision of the various machine learning techniques. This article provides a summary of the research that has previously been conducted on estimating the strength of concrete by making use of a variety of different machine learning methods. In this work, a classification of the existing body of research literature is presented, with the classification being based on the machine learning technique used by the researchers. The present review work will open the horizon for the researchers working on the machine learning based prediction of the compressive strength of concrete by providing the recommendations and benefits and drawbacks associated with each model as determining the compressive strength of concrete practically is a laborious and time-consuming task.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.27 no.5
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• pp.750-757
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• 2003

In order to determine creep stress intensity limit of high-temperature components, the usefulness of the creep work and time equation, defined as W$\_$c/t$\^$p/ = B(where W$\_$c/ = $\sigma$$\varepsilon$ is the total creep work done during creep, and p and B are constants), was investigated using the experimental data. For this Purpose, the creep tests for generating 1.0% strain for commercial type i16 stainless steel were conducted with different stresses; 160 MPa, 150 MPa, 145 MPa, 140 MPa and 135 MPa at 593$^{\circ}C$. The plots of log W$\_$c/ - log t showed a good linear relation up to 10$\^$5/ hr, and the results of the creep work-time relation for p, B and stress intensity values showed good agreement to those of isochronous stress-strain curves (ISSC) presented in ASME BPV NH. The relation can be simply obtained with only several short-term 1% strain data without ISSC which can be obtained by long-term creep data. Particularly, this relation is useful in estimating stress intensity limit for new and emerging class of high-temperature creeping materials.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.33 no.2
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• pp.791-800
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• 2013

Needs for developing a better way of cost estimating process for public construction projects have been widely recognized. Those needs are mainly from the early phases of the project through the construction life cycle due to the its importance to the control process. In contrast to the traditional estimating method based on unit-price references, this research utilized this following process. The first step is analyzing the real cost data from actual cost activities (2000~2010) about the statement of P.S.C(Prestressed Concrete) Box Girder Bridge. The collected data was broken into four categories based on technical construction methods such as I.L.M(Incremental Launching Method), M.S.S(Movable Scaffolding System), F.S.M(Full Staging Method), and F.C.M(Free Cantilever Method). The second, actual design documents including the actual cost estimating documents, drawings and specifications were carefully reviewed to cluster the cost itemized statement from four categories. It was also attempted to seek the proper breakdown of standard works that are responsible for more than 95 percentage in each categories in terms of its cost. The third, this research comes up the index for standard unit materials and unit price of standard work and develops the approximate estimating model applying for the specification(length and breadth of bridges) per square area that the user takes as well as suggests the practical application plan within the original time alloted.

• Journal of electromagnetic engineering and science
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• v.18 no.2
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• pp.94-100
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• 2018

Partial discharges (PDs) are electrical sparks that occur inside insulation between two conducting electrodes and can lead to the disastrous failure of insulation systems. To determine the location of a PD, a distributed array of UHF PD sensors is used to detect the electromagnetic (EM) signals emitted from the PD source, and the localization of the PD source can be estimated using the time difference of arrival (TDOA) between EM signals captured by the UHF PD sensor array. There are four popular methods to estimate the TDOA-the first peak method, the cross-correlation method, the energy criterion method, and the average time window threshold method. In this work, we numerically investigate the influence of noise on estimating the TDOA for the four different methods. Numerical results show that the energy criterion method is more robust against noise than other methods.

• The Transactions of the Korean Institute of Power Electronics
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• v.25 no.4
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• pp.303-310
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• 2020

Estimating the accurate internal state of lithium ion batteries to increase their safety and efficiency is crucial. Various algorithms are used to estimate the internal state of a lithium ion battery, such as the extended Kalman filter and sliding mode observer. A state-space model is essential in using algorithms to estimate the internal state of a battery. Two principal methods are used to express the state-space model, namely, continuous time and discrete time. In this work, the extended Kalman filter is employed to estimate the internal state of a battery. Moreover, this work presents and analyzes the estimation performance of algorithms consisting of a continuous time state-space model and a discrete time state-space model through static and dynamic profiles.

• Journal of Family Resource Management and Policy Review
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• v.6 no.1
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• pp.35-51
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• 2002

This study is the basic step of including the economical value of household labor into the existing GDP. Therefore this study analyzes statistical data; $\mathbb{\ulcorner}$Economical Active Population Survey$\mathbb{\lrcorner}$, $\mathbb{\ulcorner}$Time Used Survey$\mathbb{\lrcorner}$, $\mathbb{\ulcorner}$Basic Wage Structural Survey$\mathbb{\lrcorner}$, and $\mathbb{\ulcorner}$City Household Survey$\mathbb{\lrcorner}$ for that step and will help people to reconsider the importance of the economical value household work. Economical Active Population Survey classifies housework as economically nonoproductive activity Time Use Survey does not have an clear classification for action. Basic Wage Structural Survey must give subdividable information on wage. City Household Survey should include more details and more data of household durables.