• Korean Journal of Construction Engineering and Management
• /
• v.19 no.5
• /
• pp.3-9
• /
• 2018

Although Life Cycle Cost (LCC) must be evaluated by experts, sometimes it may not allow a sufficient time for even the experienced LCC expert to make rational decisions. Therefore, it often ends with relatively comparing the final numbers. We have broken down 110 technical proposals that are actually bade and accepted for large construction projects, and then have analyzed the uncertainty of Maintenance and Energy (M&E) cost during building life cycle, which turns out be the most volatile factor in uncertainty of LCC. Also we suggest "Value Engineering Index (VEI)" - the reduced M&E cost that is normalized by the reduced first cost. It is analyzed that the most uncertain factors of the M&E cost include repair and replacement term differing from each project, duplicated repair and replacement, non-standard repair items, and site-specific energy cost. Eventually we propose a VEI population with a mean of 1.38 and a standard deviation of 1.19, which is obtained by individually and exclusively applying the uncertain factors of the M&E cost to the 35 standard sample of technical proposals. The LCC evaluators may be able to use the VEI population as the benchmark to select the technical proposal with the most reasonable LCC among many others in two suggested manners; the one is to deterministically calculate the probability of single VEIs, and the other is to stochastically calculate the probability of the VEIs where uncertainty is quantified.

• Korean Journal of Construction Engineering and Management
• /
• v.21 no.4
• /
• pp.82-89
• /
• 2020

Article 64 of the Enforcement Decree of the National Contract Act The requirement of the pre-amendment statute related to the adjustment of the contract price was 5% or more of the price fluctuation rate from the date of the contract. However, the meeting requirement was changed from 5% or more to 3% or more from the date of signing of the Presidential Decree No. 19035 to 2005. 9. 8. The method of adjusting the contract amount was also changed to determine the contractor's desired adjustment method at the time of contract. Alleviating these requirements and revising the empowerment of contract partners is intended to prevent difficulties in achieving smooth objectives by applying to public construction contractors without unfairly benefiting or unfavorable to contract partners. Even if the standards are relaxed and the rights are secured as described above, if the existing provisions for the adjustment of price fluctuation are applied, unlike the original purpose of the government system, the Korea Bank's price economic statistics classification method and the contract construction classification criteria applied in public construction work Due to the inconsistency, it can be seen that the amount of adjustment for price fluctuation by construction type is excessive and underestimated. Therefore, the purpose of this study is to analyze problems through cases and to make appropriate construction cost adjustment through improvement measures.

• Geotechnical Engineering
• /
• v.5 no.4
• /
• pp.5-16
• /
• 1989

This paper statistically analyses the freezing soil by frost group and frost depth in Korea with data from soil testing in the Korea National Housing Corporation, the climate data provided by the Central Weather Office and the data on the frost depth from the National Construction Laboratory Institute. In this paper, freezing variable are analysed such as percentage finer than 0.02 m by weight, plasticity index, freezing index, water contents of soil and frost depth etc‥‥ The result of the analysis is as follows. 1) The frost depth of Korea depends on the properties of soil rather thank the characte fistic of area. 2) The distribution map of design freezing index in 57 cities is drawn up with the maxi- mum freezing index, during past 14 years, calculated by the average of the air temperature observed four times(03 : 00.09 00, 15 : 00, 21 : 00) a day. 3) By correcting the OLS line estimated from the relationship between freezing index and frost depth, a method of utlizing the line with the upper confidence limit of 99.9% int-distribution as predicted maximum frost depth is newly introduced.

• Proceedings of the Korea Water Resources Association Conference
• /
• 2020.06a
• /
• pp.233-233
• /
• 2020

최근 우리나라의 2030년 10GW의 농촌 태양광 보급목표 달성을 위해 전국적으로 분포하고 있는 저수지 및 댐 등의 공유 수면을 활용한 수상태양광 설치가 적극 검토되고 있다. 수상태양광 사업의 증가와 함께 수상태양광 설치 및 운영이 환경적 측면에서 논쟁이 대두되고 있으나 수상태양광 발전시설이 호소 수생태계에 미치는 영향을 판단할 수 있는 장기적인 조사나 과학적 연구가 부족한 실정이다. 본 연구에서는 저수지에 설치되어 있는 수상태양광 발전시설에 의한 수생태계에 미치는 영향을 파악하기 위해 수상태양광이 운영되고 있는 2개소의 저수지를 대상으로 식물플랑크톤, 동물플랑크톤, 저서성 대형무척추동물, 어류 군집조사를 2개년(2017~2018년) 동안 실시하여 각각의 종풍부도 및 종다양도 지수를 분석하였다. 1차년도에는 수상태양광 패널 설치지역 및 패널로부터 200~250m로 이격거리를 유지하면서 총 6지점을 조사하였으며, 2차년도에는 수상태양광 패널 하부(영향권) 3지점과 패널로부터 약 250m 이격된 2지점(비영향권)을 대상으로 총 6회의 조사를 수행하였다. 식물성플랑크톤, 동물성플랑크톤, 저서 대형무척추동물, 어류 군집에 대한 종풍부도와 종다양성에 대한 분석결과, 종풍부도 및 종다양도는 발전시설 영향권 지역과 비영향권 지역간에 통계학적으로 유의미한 차이는 없는 것으로 나타났다. 종풍부도는 수상태양광 패널로부터 이격거리가 멀어질수록(열린수역으로 향할수록) 감소하는 수치를 보이다가 저수지 수변부에 가까워지면 높아지는 경향을 나타났다. 종다양도 역시 종풍부도 결과와 유사하게 수상태양광 패널 지역으로부터 이격거리가 증가함에 따라(열린수역으로 향할수록) 지수가 감소하다가 저수지 수변부에 가까울수록 높아지는 결과를 보였다. 이러한 결과는 동식물성 플랑크톤과 저서생물 및 어류 군집의 종풍부도, 종다양도가 수상태양광의 영향권과 비영향권간에 큰 차이를 없음을 나타내고 있으며, 일부 분류군의 경우 열린 수면보다 수상태양광 설비에 의한 반 폐쇄수역에서 종풍부도와 종다양도가 오히려 높게 나타났다. 그러나 본 연구결과는 설치된 수상태양광 패널이 전체 수면의 5% 미만에 해당하는 소규모 시설이므로 본 연구결과를 일반화해서 해석하기에는 한계가 있다. 넓은 수면적에 설치되어 있는 대규모 시설 및 20년 이상 장기간 운영되는 수상태양광 발전시설을 대상으로 지속적인 모니터링 및 누적된 환경영향 평가가 필요할 것으로 판단된다.

• Journal of Korea Water Resources Association
• /
• v.52 no.8
• /
• pp.545-554
• /
• 2019

The most drought assessments are based on a drought index, which depends on univariate variables such as precipitation and soil moisture. However, there is a limitation in representing the drought conditions with single variables due to their complexity. It has been acknowledged that a multivariate drought index can more effectively describe the complex drought state. In this context, this study propose a Copula-based drought index that can jointly consider precipitation and soil moisture. Unlike precipitation data, long-term soil moisture data is not readily available so that this study utilized a Gaussian Mixture Non-Homogeneous Hidden Markov chain Model (GM-NHMM) model to simulate the soil moisture using the observed precipitation and temperature ranging from 1973 to 2014. The GM-NHMM model showed a better performance in terms of reproducing key statistics of soil moisture, compared to a multiple regression model. Finally, a bivariate frequency analysis was performed for the drought duration and severity, and it was confirmed that the recent droughts over Jeollabuk-do in 2015 have a 20-year return period.

• Korean Journal of Construction Engineering and Management
• /
• v.13 no.4
• /
• pp.100-109
• /
• 2012

Large road construction projects are typically partitioned into sections that are then contracted individually to contractors. Each section requires using similar heavy equipment including excavators, dump trucks and pavers, which constitute the highest cost. Normally the equipment is not shared between them, as each contractor wishes to have their equipment readily available. However, such practices result in very low utilization of these equipment. The goal of this research is to develop a programmatic resource sharing system in which contractors can share equipment depending on the changing needs of a multi-sectioned road project. This paper introduces the results of a survey performed to investigate how contractors currently manage the supply and demand of equipment and the equipment that are practical for sharing across a project. More importantly, the paper describes a set of metrics (DPR, nDPR, SDI) needed to quantify the amount of supply/demand variance occurring in each section. The metrics were used on an actual road construction project, and the results show that each section suffers from an imbalance between its monthly planned and actual utilization of equipment. The results also indicate that the sharing of the equipment can lead to potentially large savings as equipment requirements can be met within a project as to short leasing from outside vendors.

• Journal of Korean Tunnelling and Underground Space Association
• /
• v.19 no.4
• /
• pp.611-634
• /
• 2017

In rapid urbanization, demand for utility tunnel increases more, and tunnel boring machine (TBM) has been used widely. Prediction of TBM penetration rate is important for proper estimation of construction period and cost. Although there are several methods, such as NTNU model and CSM model that require many input parameters, fundamental understanding on correlations between rock properties and TBM penetration rate is critical. In this study, we explored the brittleness indices of hard rocks according to various definitions, and the correlations between the brittleness indices and the TBM penentration rates.

• The Journal of The Korea Institute of Intelligent Transport Systems
• /
• v.22 no.5
• /
• pp.163-181
• /
• 2023

Improving the detection performance of facilities corresponding to the sensors of autonomous vehicles helps driving safety. In the road and transportation field, research is being conducted to improve the detection performance of sensors by road infrastructure or facilities. As part of this on the development of autonomous driving support infrastructure, the shape of traffic cones and drums to ensure sufficient LiDAR detection performance even rainy conditions and maintain the line-of-sight guidance function in construction zones improvement effect. The principle was to increase reflection performance and ensure no significant difference in shape from existing facilities. Traffic cones were manufactured in square pyramid shapes instead of cones, and drums were manufactured in hexagonal and octagonal pillar shapes instead of cylinders. LiDAR detection data for the facility was confirmed on a clear day and with 20 mm/h and 40 mm/h rainfall. The detection performance of the square pyramid-shaped traffic cone and octagonal column-shaped drum was to the existing facility. On the other hand, deviations occurred due to repeated measurements, and significance could not be confirmed through statistical analysis. By reflecting these results, future studies will seek a form in which data can be obtained uniformly despite the diversity of measurement environments.

• Journal of Cadastre & Land InformatiX
• /
• v.51 no.2
• /
• pp.125-139
• /
• 2021

Continuous subway line expansion over the years in Seoul metropolitan area has contributed to improved accessibility to public transport. Since public transport accessibility has a significant impact on housing decisions, quantitative analysis of correlation between housing prices and public transport accessibility is regarded as one of the most important factors for planning better housing policies. This study defines the reduction of traveling time resulted from the construction of new metro stations despite them not being the closest stations as 'Network Expansion Effect', and seeks to understand how the Network Expansion Effect impacts on housing prices. The study analyzes monthly rent data converted from upfront lump sum deposit, so called Jeonse in Korea, from 2012 to 2018, through 'A Modified Repeat Sales Model.' As a result, the effect of 'Network Expansion' on rental prices in Seoul has stronger during the period of 2017 to 2018 than the base period of 2012 to 2014, which suggests the 'Network Expansion' has a meaningful effect on rent. In addition, in comparison between the most and the least affected group of apartments by 'Network Expansion Effect', the most affected group has more price increase than the least affected group. These findings also indicate that different levels of 'Network Expansion Effect' have various influences on the value of residential real estate properties.

• Journal of the Korean GEO-environmental Society
• /
• v.17 no.12
• /
• pp.35-43
• /
• 2016

With the development of construction technology, constructions of dam and levee (dike) as well as the environmental problems are becoming issues. Recently, many countries have tried to develop and used CSG (Cemented Sand and Gravel), which needs fewer requirements than others in aggregates, constructability and ground condition during the dam construction. Mixing up with small amount of cement, CSG is able to increase the strength and proceed accelerated construction without artificial gradation adjustment of riverbed aggregate and crushed rock on construction site. Thus, CSG can minimize environmental damage resulted from quarries mining and reduce cost of construction. Unlike heat of hydration condition that regular concrete usually met, CSG exposes to repeated dry-wet and freezing and thawing environment. Thus, consider the importance of structure of dam or levee, intensive study on the durability of CSG is needed. In this study, freezing and thawing experiment was carried out to evaluate the durability of CSG. In results, the durability factor of CSG is 30~40 or >40 when the amount of cement is $0.4{\sim}0.6kN/m^3$ or $0.8{\sim}1.0kN/m^3$, respectively. The unconfined compressive strength is reduced to 30~50% or 40~70% when the amount of cement is $0.4{\sim}0.6kN/m^3$ or $0.8{\sim}1.0kN/m^3$, respectively. Taken together, the strength and durability of CSG is reliable when the amount of cement is over $0.8kN/m^3$.