• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.30 no.2A
• /
• pp.161-168
• /
• 2010

The bonded tendon was adopted to the reactor building of some operating nuclear power plants in Korea and the assessment of the effective prestress force on the bonded tendon is being issued as an important pending problem for continuous operation beyond their design life. The sensitivity analysis of various parameters was carried out to evaluate the effective prestress force using the system identification technique and the optimal parameters were determined for SI technique in this study. The 1/5 scaled post-tensioned concrete beams with the bonded tendon type were manufactured and in order to investigate the relationship of the natural frequency and the displacement to the effective prestress force, impact test, SIMO sine sweep test and bending test using the optical fiber sensor and the compact displacement transducer were carried out. As a result of tests, both the natural frequency and the displacement show the good relationship with the effective prestress force and both parameters are available for the SI technique to estimate the effective prestress force.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.26 no.6D
• /
• pp.975-983
• /
• 2006

This study analyzed bidding data for construction projects ordered by the Public Procurement Service under the lowest bidding system since 2001 by using statistical technique in terms of construction types, company sizes, bidding prices. This study brings out construction company's bidding practices and problems caused by the current lowest bidding system and suggests the way to mitigate the problems and to improve the lowest bidding system. The analysis shows the problem of winning a bid in abnormally low price under the lowest bidding system, feared at the start, was realized. As bidding practice has polarized with low and high price, the analysis shows that the lowest bid system's market has a high possibility to be distorted by construction companies' bid strategies. To complement the lowest bidding system's problem, the analysis shows that introduction of the bidding system using particulars where bidders estimate construction quantities and unit prices by themselves is needed.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.29 no.3A
• /
• pp.227-234
• /
• 2009

Recently, a knee brace is usually installed in connection between cross-beam and main-girder of steel box-girder bridges. The knee brace is installed as a structural stiffener and mainly aims to relieve stress at joints and to prevent main-girder from lateral deformation. However, research on the knee brace is insufficient to obviously evaluate the necessity. The stiffened effect of knee brace is determined by using finite element analyses. Stress distribution, stress level of members and deflection of the cross-beam are evaluated by parametric FE analysis for the installation of knee brace and the depth ratio of cross-beam/steel box girder. It is seen from comparison of numerical analysis results that the knee brace installed in cross-beam of steel boxgirders bridges is not efficient as a structural stiffener with respect to stress relief and stiffened effect.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.29 no.4A
• /
• pp.395-405
• /
• 2009

The purpose of this study was to investigate the performance of precast segmental PSC bridge columns with precast concrete footings. The proposed system can reduce work at a construction site and makes construction periods shorter. The precast concrete footings is intended to support precast segmental PSC bridge columns and provides an alternative to current cast-inplace systems, particularly for areas where reduced construction time is desired. Shortened construction time, in turn, leads to important safety and economic advantages when traffic disruption or rerouting is necessary. A model of precast segmental PSC bridge columns was tested under a constant axial load and a cyclically reversed horizontal load. In the companion paper, the experimental and analytical study for the performance assessment of precast segmental PSC bridge columns with precast concrete footings is performed.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.26 no.4B
• /
• pp.433-437
• /
• 2006

Recently, mathematical modeling for the activated sludge process is important to design and control of wastewater treatment plant. Nevertheless, there is a lack of information regarding the pathway of substrate utilization between external and internal substrates in biological nutrient removal (BNR). In this research, a new activated sludge model (step growth model) is proposed and compare with ASM No.3. This model structure is consist of five processes; aerobic storage, growth on external substrate and stored intercellular storage compounds (ISCs), endogenous respiration and aerobic respiration of ISCs. The predicted results by the step growth model were more good accordance with the results of oxygen utilization rate (OUR) and TCOD experiment than that of the ASM No.3.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.30 no.6D
• /
• pp.605-613
• /
• 2010

In this study, Impact factors are represented and barrier height of compact car road of safety barrier is suggested through the investigation of applying problems of existed standard of general car road. For this, traffic accidents analysis is performed and based on the analysis, impact vehicle weight, impact Angle, crash velocity, and barrier height are investigated. For the decision of impact angle, analysis is carried out by comparison of RISER and 2-lines expressway accidents data. Through this, higher-impact angle is suggested. Vehicle weight data of sub-compact car, small vehicle, medium and large vehicle, SUV, small truck is surveyed and analyzed. Based on the accident accumulation rate, regression analysis of vehicle weight impact and impact velocity is performed. Also, based on the cumulative rate of vehicle weight on expressways near Seoul, barrier height of compact car road is calculated. It is noted that the results of this study will be contributed to the decision of barrier type.

• Korean Journal of Construction Engineering and Management
• /
• v.24 no.2
• /
• pp.79-87
• /
• 2023

Given that most government contracts are based on a fiscal year, long-term continuing construction contracts require appropriate provisions as significant amounts of budget is supposed to be invested for several years. This study drew problems and improvements of the long-term continuing construction contracts by analyzing the contents of FGI and list of construction order. We found that a number of problems, such as the mismatch between laws and enforcement decrees, difference in calculating overheads due to the extension of construction period, many construction orders that are hard to see as budget efficiency and over investment in the final annual contract, were tangled up in the process. To solve the problems mentioned, we suggested several improvements as follows: (1) effect of total construction period and total amount should be guaranteed by a law, (2) it is suggested that the scope of long-term continuing construction contract is determined by a law, and (3) it should be clear about the calculation of overheads concerned with the extension of construction period as well as the estimation of construction period to prevent over investment in the final contract.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.35 no.6
• /
• pp.1405-1412
• /
• 2015

In Korea, public infrastructure projects employ "long term continuation (LTC) contracts," which require budgets to be reevaluated and re-appropriated annually throughout the multi-year life of the project. However, such contracts also make it susceptible to frequently changing government policies, in which budgets required for existing projects are allocated to new projects and thus does not provide a consistent stream of capital to multi-year projects. Each year, the KEC needs to attain government funds for construction of its multiple highway construction sites. Because it is difficult to know the amount that may be actually appropriated to KEC in a given year, it is in turn difficult to anticipate and provide sufficient funds necessary for construction to run smoothly and continuously. The lack of a good logic for appropriation has resulted in projects having a skewed distribution of capital. To get better budget appropriations from the central government, the KEC first needs a systemized approach that rationalizes the annual construction capital optimally required for its individual sites. The goal of this research was to devise a way that allows the KEC to determine and calculate the optimal construction costs that would be required for its individual construction sites on an annual basis. Both the optimal progress rate and the essential work types were assessed through a workshop with 24 professionals (KEC employees and contractors) who had extensive experience in KEC projects and also were currently working in these projects.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.34 no.3
• /
• pp.1007-1015
• /
• 2014

The importance of construction waste reusing and recycling is becoming increasingly large because the demolition industry is in current trend to pursue for sustainable growth. As the considering situation of the domestic housing construction and existing house, a scale of demolition industry is expected to be increased continuously. But the related cost regulations that are used in tendering in the demolition industry are insufficient, also the computer system for estimating the demolition costs have not been developed yet. Therefore, in this study suggests man-hours of 21EA items which are utilized to estimate demolition cost and work rate of $1.0m^3$ breaker which is used mostly in domestic demolition industry after analyzing a case study for deconstruction works. The computer system is developed for the estimating demolition cost easily, which are including five modules such as a project information, a unit cost management, a standard unit cost table, a bill of quantity, and a reporting system. This computer system is possible to apply for estimating cost of both mechanical demolition and blasting demolition. The biggest advantage of this system is to estimate cost to utilize standard WBS which is linked with standard unit table and each DB. This can help unskilled users use easily for it.

• Korean Journal of Construction Engineering and Management
• /
• v.11 no.1
• /
• pp.142-150
• /
• 2010

The purpose of this study is to analyze maintenance costs and estimation of elemental costs for educational buildings. The adapted research method selected four school buildings in seoul region as BTL projects. On the basis of the selected case, the study suggested a model to establish a system for each parts and estimate analyzed construction costs and maintenance costs according to that system. According to the analysis, the study proposed a partial construction costs analysis table and maintenance costs table and analyzed proper construction costs and maintenances costs. The results of this study are as follows 1) The average ratio followed by calculation of partial construction costs of the four school buildings are as followings. The total construction costs is analysed 6,666million won and each part of average rations is structure 47.15%, exterior of building 8.34%, interior of building 23.37%, electricity & fire fighting facility 5.74%, water supply & healthy facility 4.27%, heating & water supply facility 5.25%, landscape 1.36%, civil engineering works 4.51%. 2)The average ratio followed by analysis of partial maintenance costs of the four school buildings are as followings. The total maintenance costs is analysed 4,309 million won and each part of average ratio is exterior of building 11.02%, interior of building 41.81%, electricity & fire fighting facility 14.81%, water supply & healthy facility 11.22%, heating & water supply facility 12.76%, landscape 5.75%, civil engineering works 2.63%.