Mobile QR Code QR CODE : Journal of the Korean Society of Civil Engineers

KSCE JOURNAL OF CIVIL AND
ENVIRONMENTAL ENGINEERING RESEARCH

The Journal of the Korean Society of Civil Engineers (KSCE) is a bimonthly journal, founded in December 1981, for the publication of peer-reviewed papers devoted to research and development for a wide range of civil engineering fields.

• Editors-in-Chief: Cheol Woo Park

강합성 교량의 콘크리트 바닥판 해체 및 재시공이 용이한 분리식 볼트접합 전단연결재에 관한 실험적 연구 An Experimental Study of Demountable Bolted Shear Connectors for the Easy Dismantling and Reconstruction of Concrete Slabs of Steel-Concrete Composite Bridges

https://doi.org/10.12652/Ksce.2022.42.6.0751

정대성(Jung, Dae Sung) ; 박세현(Park, Se-Hyun) ; 김태형(Kim, Tae Hyeong) ; 김철영(Kim, Chul Young)

Welded head studs are mainly used as shear connectors to bond steel girders and concrete slabs in steel-concrete composite bridges. For welded shear connectors, environmental problems include noise and scattering dust which are generated during the removal of damaged or aged slabs. Therefore, it is necessary to develop demountable shear connectors that can easily replace aged concrete slabs for efficient maintenance and thus for better management of environmental problems and life cycle costs. The buried nut method is commonly studied in relation to bolted shear connectors, but this method is not used in civil structures such as bridges due to low rigidity, low shear resistance, and increased initial slip. In this study, in order to mitigate these problems, a demountable bolted shear connector is proposed in which the buried nut is integrated into the stud column and has a tapered shape at the bottom of an enlarged column shank. To verify the performance of the proposed demountable stud bolts in terms of static shear strength and slip displacement, a horizontal shear test was conducted, with the performance outcomes compared to those of conventional welded studs. It was confirmed that the proposed demountable bolted shear connector is capable of excellent shear performance and that it satisfies the slip displacement and ductility design criteria, meaning that it is feasible as a replacement for existing welding studs.

산업환경시설의 설계하중과 내진성능목표 개선안 Improvement in Design Load and Seismic Performance Objective for Industrial and Environmental Facilities

https://doi.org/10.12652/Ksce.2022.42.6.0763

김익현(Kim, Ickhyun) ; 홍기증(Hong, Kee-Jeung) ; 김정한(Kim, Jung Han) ; 이진호(Lee, Jin Ho) ; 조성국(Cho, Sunggook) ; 이진형(Lee, Jin-Hyeong)

Industrial and environmental facilities, which are national growth engine, must sustain their structural safety and maintain theirprocess to continue production activities under various load conditions including natural hazards. In this study, by improving existingdesign codes which aim to secure the structural safety only, new structural and seismic design codes are proposed to secure both thestructural safety and the operability of facilities. In the proposed structural design code, a variety of loads to reflect the characteristicsof industrial and environmental facilities are considered and load combinations for the ultimate strength design and the allowable stressdesign of structures are suggested. Considering the importance of a unit industrial facility and that of a unit process, the seismic designclass, design earthquake, and seismic performance level of a unit component are determined to achieve the dual seismic performanceobjectives for securing both the structural safety and the operability. Also, the proposed design code are applied to an example of anenvironmental facility in order to examine its applicability.

관통부의 철근 절단으로 인한 주변 철근의 응력분포 특성 Stress Distribution Characteristics of Surrounding Reinforcing Bars due to Reinforcing Bar Cutting in Penetration

https://doi.org/10.12652/Ksce.2022.42.6.0775

정철헌(Chung, Chul-Hun) ; 문일환(Moon, Il Hwan) ; 이정휘(Lee, Jungwhee) ; 송재철(Song, Jae Cheol)

In the plant structures including nuclear power plants, penetrations are frequently installed in walls and slabs to reinforce facilitiesduring operation, and reinforcing bars are sometimes cut off during concrete coring. Since these penetrations are not considered at thedesign or construction stage, cutting of reinforcing bar during opening installation is actually damage to the structure, structuralintegrity evaluation considering the stress transition range or effective width around the new penetration is necessary. In this study,various nonlinear analyses and static loading experiments are performed to evaluate the effect of reinforcing bar cutting that occurswhen a penetration is newly installed in the shear wall of wall-type building of operating nuclear power plant. In addition, the decreasein wall stiffness due to the installed new penetration and cutting of reinforcing bars is evaluated and the stress and strain distributionsof rebars around penetration are also measured.

저온 상변화 물질 함침 경량골재를 이용한 나노 개질 융설 콘크리트 개발 Development of Nanomodified Snow-Melting Concrete Using Low-Temperature Phase-Change Material Impregnated Lightweight Aggregate

https://doi.org/10.12652/Ksce.2022.42.6.0787

경주현(Kyoung, Joo-Hyun) ; 김선미(Kim, Sean-Mi) ; 허종완(Hu, Jong-Wan)

In winter, the excessive use of deicing salt deteriorates concrete pavement durability. To reduce the amount of deicing salt used, phase-changematerials (PCMs) potentially offer an alternative way to melt snow through their latent heat storage characteristics. In this research, thermalenergy storage concrete was developed by using PCM-impregnated expanded clay as 50 % replacement to normal aggregate by volume. Inaddition, to improve the thermal efficiency of PCM lightweight aggregate (PCM-LWA)-incorporated concrete, multi-walled carbon nanotubes(MWCNTs) were incorporated in proportions of 0.10 %, 0.15 %, and 0.20 % by binder weight. Compressive strength testing and programmedthermal cycling were performed to evaluate the mechanical and thermal responses of the PCM-LWA concrete. Results showed a significantstrength reduction of 54 % due to the PCM-LWA; however, the thermal performance of the PCM-LWA concrete was greatly improved withthe addition of MWCNTs. Thermal test results showed that 0.10 % MWCNT-incorporated concrete had high thermal fatigue resistance as wellas uniform heat flow, whereas specimens with 0.15 % and 0.20 % MWCNT content had a reduced thermal response due to supercooling whenthe ambient temperature was varied between -5 °C and 10 °C.

잔류유량 기반 복원력 지수를 통한 빗물펌프장 자동운영 성능 검토 A Study of the Automatic Operation Performance of a Pump Station using Resilience Considering Residual Flows

https://doi.org/10.12652/Ksce.2022.42.6.0793

김영남(Kim, Young Nam) ; 이의훈(Lee, Eui Hoon)

Non-structural improvements to urban drainage systems are necessary to overcome the elevated levels of urban flood damage. Thisstudy proposed a type of automatic pump/gate operation technology for urban pump stations that takes reservoir inflows and riverwater levels into account and its performance is compared with the current operation using the concept of residual flow-based resilience. The proposed automatic operation relies on three pump operations and two gate operations. The water depth at the monitoring nodewas used for the pump operation, and the monitoring node was selected in consideration of the first overflow node and the maximumoverflow node. The target area is the Daegu Bisan urban pump station, and the rainfall data consisted of probability rainfall sets withdurations of 30 minutes, 60 minutes, 90 minutes and 120 minutes, and frequencies of 30, 50, and 70 years. As a result of the applicationof the proposed operation, differences in the resilience between the automatic operation and the current operation were at least 5.20E-05with a maximum of 8.07E-04. The longer the duration is, the greater the difference in the resilience.

라오스 남능강 유역 다중 저수지 시스템의 최적 수력발전 운영규정 곡선 개발 Development of Multi-Reservoir System Operation Rule Curves for Hydropower Maximization in the Nam Ngum River Basin of Lao PDR

https://doi.org/10.12652/Ksce.2022.42.6.0803

이현재(Lee, Hyun-Jae) ; 장웅철(Jang, Woong-Chul) ; 이일주(Lee, Il-Ju) ; 이진희(Lee, Jin-Hee)

The Lao government is continuously developing hydro-power dams in addition to the existing eight power plants in the Nam Ngum River basin and is expanding the power capacity of the existing power plants to meet the expected increase in electricity demand. Accordingly, the Lao government has requested an update on the existing reservoir operating rule curve in order to run the power plants efficiently. To this end, this study reviewed the current independent operating system as well as the joint operating system inorder to maximize the annual power generation produced by a power plant by using CSUDP, general-purpose dynamic programming (DP) software. The appropriate operating regulation curve forms (URC/LRC, MRC) were extracted from the DP results, and theannual power generations were simulated by inputting them as the basic operating data of the reservoir operation set of the HEC-ResSim program. By synthesizing the amount of the annual power generation simulated, the existing operation regulationcurve, the operational performance, and the opinion of the field operator, the optimal reservoir operation regulation curves that maximize the annual power generation of the target power plant were developed. Results revealed that a system operating inconjunction with the reservoir produces about 2.5 % more power generation than an independent reservoir due to the synergistic effect of the connection.

수리실험을 이용한 발전소의 순환수 취수부 흡입수조의 와류저감에 관한 연구 On Vortex Reduction Characteristics of Pump Sump Circulating Water Intake Basin of Power Plant Using Hydraulic Experiment

https://doi.org/10.12652/Ksce.2022.42.6.0815

엄중현(Eom, Junghyun) ; 이두한(Lee, Du Han) ; 김형수(Kim, Hung Soo)

Among the main facilities of the power plant, the circulating water used for cooling the power generation system is supplied through the Circulation Water Intake Basin (CWIB). The vortexes of various types generated in the Pump Sump (PS) of CWIB adversely affectthe Circulation Water Pump (CWP) and pipelines. In particular, the free surface vortex accompanied by air intake brings about vibration, noise, cavitation etc. and these are the causes of degradation of CWP performance, damage to pipelines. Then powergeneration is interrupted by the causes. Therefore, it is necessary to investigate the hydraulic characteristics of CWIB through the hydraulic model experiment and apply an appropriate Anti Vortex Device (AVD) that can control the vortex to enable smoothoperation of the power plant. In general, free surface vortex is controlled by Curtain Wall (CW) and the submerged vortex is by the antivortex device of the curtain wall. The detailed specifications are described in the American National Standard for Pump Intake Design. In this study, the circulating water intake part of the Tripoli West 4×350 MW power plant in Libya was targeted, the actual operating conditions were applied, and the vortex reduction effect of the anti vortex device generated in the suction tank among the circulating water intake part was analyzed through a hydraulic model experiment. In addition, a floor splitter was basically applied to control the submerged vortex, and a new type of column curtain wall was additionally applied to control the vortex generated on the free surfaceto confirm the effect. As a result of analyzing the hydraulic characteristics by additionally applying the newly developed Column Curtain Wall (CCW) to the existing curtain wall, we have found that the vortex was controlled by forming a uniform flow. In addition,the vortex angle generated in the circulating water pump pipeline was 5° or less, which is the design standard of ANSI/HI 9.8,confirming the stability of the flow.

선압축 보강마이크로파일의 하중분담 특성을 고려한 건물 보강효과에 대한 연구 Reinforcing Effect of Buildings Considering Load Distribution Characteristics of a Pre-compressed Micropile

https://doi.org/10.12652/Ksce.2022.42.6.0825

이광훈(Lee, Kwang Hoon) ; 박용찬(Park, Yong Chan) ; 문성진(Moon, Sung Jin) ; 유광호(You, Kwang Ho)

Micropiles can be used to support additional load in extended building structures. However, their use brings about a risk of exceeding the bearing capacity of existing piles. In this study, pre-compression was applied to distribute the load of an existing building to micropiles, and an indoor loading test was performed to confirm the structural applicability of a wedge-type anchorage device designed to improve its capacity. According to the test results, the maximum strain of the anchorage device was 0.63 times that of the yield strain, and the amount of slip generated at the time of anchorage was 0.11 mm, satisfying structural standards. In addition, using MIDAS GTS, a geotechnical finite element analysis software, the effect of the size of the pre-compression, the thickness of the soil layer, and the groundconditions around the tip on the reaction force of the existing piles and micropiles were analyzed. From the numerical analysis, as the size of the pre-compression load increased, the reaction force of the existing pile decreased, resulting in a reduction rate of up to 36 %. In addition, as the soil layer increased by 5 m, the reduction rate decreased by 4 %, and when the ground condition at the tip of the micropile was weathered rock, the reduction rate increased by 14 % compared with that of weathered soil.

지능형철도선형계획 프로그램(ei-Rail) 기반의 단선철도 복선화 계획 기술개발 Development of Planning Method for Double-Tracking of Single Track Railroad based on the Intelligent Rail Alignment Planning Program (ei-Rail)

https://doi.org/10.12652/Ksce.2022.42.6.0837

김정현(Kim, Jeong Hyun)

The “Intelligent Railroad Alignment Design Program (ei-Rail) developed in 2013 has been adopted in the planning and the evaluation/validation of design results of oversea railroad construction projects. Target countries of Korean railroad industries requiresthe operating speed increase with alignment improvement and the double tracking of prevailing single track railroads as well as new railroad construction. This study is to develop an additional module for double tracking project of prevailing single track railroads in the ei-Rail. The developed method is based on the geometrics of prevailing railroad, and the definition of planned project determines the project cost based on the unit cost by work type, and provides the draft design of double track. The module was validated with aoversea case. It is then expected for oversea railroad double tracking project more efficiently in planning and the evaluation of design results.

빅데이터를 활용한 AI 기반 우선점검 대상현장 선정 모델 AI-based Construction Site Prioritization for Safety Inspection Using Big Data

https://doi.org/10.12652/Ksce.2022.42.6.0843

황윤호(Hwang, Yun-Ho) ; 지석호(Chi, Seokho) ; 이현승(Lee, Hyeon-Seung) ; 정현준(Jung, Hyunjun)

Despite continuous safety management, the death rate of construction workers is not decreasing every year. Accordingly, various studies are in progress to prevent construction site accidents. In this paper, we developed an AI-based priority inspection target selection model that preferentially selects sites are expected to cause construction accidents among construction sites with construction costs of less than 5 billion won (KRW). In particular, Random Forest (90.48 % of accident prediction AUC-ROC) showed the best performanceamong applied AI algorithms (Classification analysis). The main factors causing construction accidents were construction costs, total number of construction days and the number of construction performance evaluations. In this study an ROI (return of investment) of about 917.7 % can be predicted over 8 years as a result of better efficiency of manual inspections human resource and a preemptive response to construction accidents.

엔지니어링 노임단가 산출기준 개선방안과 적정 노임단가 추정 Improvement in Calculating Engineer Standard Wage Rate and Its Appropriate Level Computation

https://doi.org/10.12652/Ksce.2022.42.6.0853

이재열(Lee, Jae Yul) ; 이해경(Lee, Hae Kyung)

The purpose of this study is to suggest an improvement plan for the calculation method of the engineer standard wage rate (ESWR) and to compute a reasonable ESWR. To this end, an adequacy review of theESWR calculation criteria was conducted along with an extensive engineering industry survey. The survey results were analyzed using an effective response sample of 748 companies out of 1,000 survey samples extracted by stratifying the 5,879 survey population. The main results were as follows. ①When calculating theengineering service fee, the prime contractor’s engineer wage is suitable for the ESWR. The ESWR can be estimated by the formula ‘average wage÷[1-proportion of subcontract orders×(1-subcontract rate)].’ ② The field survey showed that the number of monthlyworking days was 20.35?20.54 days at 99 % confidence interval, which was significantly different from the current standard (22 days). In addition, as a result of a legal review of the ESWR criteria, it was found that the number of working days should be calculated in accordance with the Labor Standards Act after 2022. ③ Applying government guidelines, the time difference between the wage surveyand the ESWR application can be corrected by the past ESWR increase rate for a specific period. ④ Using modeling based on the analysis above, the current ESWR was 13.5?14.5 % lower than the appropriate level. A lower ESWR was driven by the non-reflection of subcontract structure (4.1 %), overestimation of monthly work days (6.8?7.8 %), and application of past wage (2.6 %). The proposed model is expected to be widely used in policy making, as it can provide a useful framework for calculating the standard wage rate insimilar industries as well as calculating appropriate engineering fees.

4D 시뮬레이션을 위한 3D 모델 및 공정 정보의 연계 간소화 기법 연구 A Study on a Technique for Simplifying the Connection of a 3D Model and Schedule Information for 4D Simulation

https://doi.org/10.12652/Ksce.2022.42.6.0861

박상미(Park, Sang Mi) ; 이재희(Lee, Jae Hee) ; 윤형석(Yoon, Hyeong Seok) ; 황재영(Hwang, Jae Yoeng) ; 강효정(Kang, Hyo Jeong) ; 강인석(Kang, Leen Seok)

A key use of applying building information modeling (BIM) to the construction stage of a project is to help identify construction obstacles and to visualize construction status according to the progress of the construction schedule. When employing 4D simulationfor this purpose, start and finish dates for each activity and a 3D model of the activity must be prepared. In this work, in order to simplify the configuration of a 4D model, minimum attribute information of the BIM model produced in the design stage was used to constructa system that generated activity information in the construction stage using a clustering algorithm. Its usefulness as actual schedule management information was then analyzed.

주택연금 중도해지자의 재가입 소요기간 결정요인 분석 Determinants of Re-Subscription Period of Early Termination Subscribers of Reverse Mortgage

https://doi.org/10.12652/Ksce.2022.42.6.0869

류기윤(Ryou, Ki Yun) ; 최열(Choi, Yeol)

This study aims to analyze the factors affecting the re-subscription period upon initial termination of the reverse mortgage subscription. The study utilized the Korea Housing Finance Corporation’s database to extract the information regarding re-subscribers of the reverse mortgage from July 2007 to June 2021. The ordered logit model was employed and found that a set of user (subscriber) characteristics are influential towards the re-subscription period. Among the individual characteristics, changes in age group, marital status from married to single-living, maintaining single-living, and the initial subscription period were found statistically significant, highlighting that the increase in the initial subscription period decreased the re-subscription period. Among the housing (home equity) characteristics, changes in housing price and ownership type (single and partial ownership) were statistically significant, indicating that the change in ownership type decreases the re-subscription period. Lastly, the variables related to loan terms were found significant,revealing that changes in payout method and schedule were both increasing factors of the re-subscription period. Based on the findings,necessary policy implications can be considered to secure the returning subscribers of the reverse mortgage effectively.

철도시설 부지 입체적 활용 및 제도적 지원의 필요성 - 경부선 철도 입체화 사업을 대상으로 - Multi-dimensional Utilization of a Railway Facility Site and the Need for Institutional Support: The Multi-dimensional Project of the Gyeongbu Line

https://doi.org/10.12652/Ksce.2022.42.6.0879

신은호(Shin, Eun ho) ; 김종구(Kim, Jong gu) ; 강윤원(Kang, Youn won) ; 금윤전(Keum, Yun geon) ; 권영수(Kwon, Young soo)

Of increasing global popularity is the multi-dimensional use and development of cities to address land use and urban issues caused byhigh urban density and challenging topography. In Korea, the city of Busan has a large proportion of mountainous areas, and theGyeongbu Line that runs through the city’s center has been interrupting this urban area for over 117 years. Because a lack of usable landis hindering the development of the city, introducing a multi-dimensional approach to urban development is seen as important. Accordingly, the Gyeongbu Line underground project is attempting to solve the problem of disconnection of Busan’s city center andincrease the amount of usable land for varied multi-dimensional use. In this study, by conducting a preference survey among those wholive near the underground project sites of the Gyeongbu Line stations in Busan, the planned use of each available land arearesultingfrom the multi-dimensional development of railroadsand railway stations was investigated. However, in order to further the results ofthe survey, legal and institutional support is needed. There are limits to the multi-dimensional use of land, such as the lack ofinterconnection between individual laws and the lack of specific guidelines for multi-dimensional development.

해외철도사업의 민간투자 위험 요인 분석에 관한 연구 A Study on Analysis of Risks Related to Overseas Railroad Private?Public Partnership Projects

https://doi.org/10.12652/Ksce.2022.42.6.0887

조현미(Cho, Hyunmi) ; 김시곤(Kim, Sigon)

Due to various reasons (normally financial constraints in developing countries), it becomes common to change of the business model from state-run projects to Private Investment Projects (Public Private Partnership) in the global railway businesses. However, due tothe nature of railroads compared with other types of infrastructure such as roads and others, railway business require considerable construction cost and O&M cost through the business development, construction, and operation and management stages. Therefore,private investment railway projects, especially in developing countries, can be problematic in terms of the potential for uncertainty when return on investment cannot be guaranteed. In order to strengthen the competitiveness of domestic companies when enteringoverseas railroad PPP projects, this study proposes PPP-related risks and their countermeasures by reviewing global railroad trends and identifying Korea’s weakness in managing international railroad projects.