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There has been an increase in the deterioration of buildings and infrastructure in dense urban regions, and several defects in the structures are being exposed. To ensure the effective diagnosis of building conditions, vision-based automatic damage recognition techniques have been developed. However, conventional image processing techniques have some limitations in real-world situations owing to their manual feature extraction approach. To overcome these limitations, a convolutional neural network-based image recognition technique was adopted in this study, and a convolution-based concrete multi-damage recognition neural network (CMDnet) was developed. The image datasets consisted of 1981 types of concrete surface damages, including surface cracks, rebar exposure and delamination, as well as intact. Furthermore, it was experimentally demonstrated that the proposed model could accurately classify the damage types. The results obtained in this study reveal that the proposed model can recognize the different damage types from digital images of the surfaces of concrete structures. The trained CMDnet demonstrated a damage-detection accuracy of 98.9%. Moreover, the proposed model could be applied in automatic damage detection networks to achieve superior performance with regard to concrete surface damage detection and recognition, as well as accelerating efficient damage identification during the diagnosis of deteriorating structures used in civil engineering applications.
Hyun Kyu Shin; Yong Han Ahn; Sang Hyo Lee; Ha Young Kim. Automatic Concrete Damage Recognition Using Multi-Level Attention Convolutional Neural Network. Materials 2020, 13, 5549 .
AMA StyleHyun Kyu Shin, Yong Han Ahn, Sang Hyo Lee, Ha Young Kim. Automatic Concrete Damage Recognition Using Multi-Level Attention Convolutional Neural Network. Materials. 2020; 13 (23):5549.
Chicago/Turabian StyleHyun Kyu Shin; Yong Han Ahn; Sang Hyo Lee; Ha Young Kim. 2020. "Automatic Concrete Damage Recognition Using Multi-Level Attention Convolutional Neural Network." Materials 13, no. 23: 5549.
Defects in residential building façades affect the structural integrity of buildings and degrade external appearances. Defects in a building façade are typically managed using manpower during maintenance. This approach is time-consuming, yields subjective results, and can lead to accidents or casualties. To address this, we propose a building façade monitoring system that utilizes an object detection method based on deep learning to efficiently manage defects by minimizing the involvement of manpower. The dataset used for training a deep-learning-based network contains actual residential building façade images. Various building designs in these raw images make it difficult to detect defects because of their various types and complex backgrounds. We employed the faster regions with convolutional neural network (Faster R-CNN) structure for more accurate defect detection in such environments, achieving an average precision (intersection over union (IoU) = 0.5) of 62.7% for all types of trained defects. As it is difficult to detect defects in a training environment, it is necessary to improve the performance of the network. However, the object detection network employed in this study yields an excellent performance in complex real-world images, indicating the possibility of developing a system that would detect defects in more types of building façades.
Kisu Lee; Goopyo Hong; Lee Sael; Sanghyo Lee; Ha Kim. MultiDefectNet: Multi-Class Defect Detection of Building Façade Based on Deep Convolutional Neural Network. Sustainability 2020, 12, 9785 .
AMA StyleKisu Lee, Goopyo Hong, Lee Sael, Sanghyo Lee, Ha Kim. MultiDefectNet: Multi-Class Defect Detection of Building Façade Based on Deep Convolutional Neural Network. Sustainability. 2020; 12 (22):9785.
Chicago/Turabian StyleKisu Lee; Goopyo Hong; Lee Sael; Sanghyo Lee; Ha Kim. 2020. "MultiDefectNet: Multi-Class Defect Detection of Building Façade Based on Deep Convolutional Neural Network." Sustainability 12, no. 22: 9785.
This study systematically analyzes various defect patterns that occur during the warranty period of residential buildings using the loss distribution approach (LDA). This paper examines 16,108 defects from 133 residential buildings where defect disputes occurred between 2008 and 2018 in South Korea. The analysis results showed that the defect losses were relatively high in reinforcement concrete (RC) work (3/5/10 years), waterproof work (5 years), and finish work (2 years). It is shown that RC work has a high frequency of defects, such as cracks in concrete in public spaces affected by external factors. In addition, it was analyzed that the type of defect needed high repair cost because the area where the defect—such as incorrect installation and missing task—occurred, needed construction again. According to the level of frequency and severity, losses were divided within four zones to provide detailed strategies (by period). This will effectively contribute to minimizing unnecessary losses from defects as quantifying the losses of defects.
Byeol Kim; Yonghan Ahn; Sanghyo Lee. LDA-Based Model for Defect Management in Residential Buildings. Sustainability 2019, 11, 7201 .
AMA StyleByeol Kim, Yonghan Ahn, Sanghyo Lee. LDA-Based Model for Defect Management in Residential Buildings. Sustainability. 2019; 11 (24):7201.
Chicago/Turabian StyleByeol Kim; Yonghan Ahn; Sanghyo Lee. 2019. "LDA-Based Model for Defect Management in Residential Buildings." Sustainability 11, no. 24: 7201.
The latest IT technology integration movements, such as building information modeling (BIM), have engendered changes in the technology and participatory organizations in the construction industry, which have resulted in process innovations and productivity gains. BIM lays the foundation for using a variety of new information that is not applicable to traditional construction methods. Construction companies are applying such information to various analyses, simulations, and learning and education projects to stimulate innovation. In Korea, however, since BIM was introduced in 2008, it has been used in various ways across diverse fields, but its contribution remains minimal. This is due to the inadequate competence level of BIM managers, who emerge from a system incapable of adequately educating BIM managers. In other words, the curriculum has not been able to impart the BIM skills necessary to accommodate the requirements of the industry. Only the most basic BIM modeling course is offered, and even such a course is dependent on external instructors. This creates a gap with the existing construction engineering educational curriculum. This study proposes a BIM-based construction engineering educational curriculum that has not been attempted before to overcome these limitations and generate a BIM workforce to cater to the industry.
Sanghyo Lee; Joosung Lee; Yonghan Ahn. Sustainable BIM-Based Construction Engineering Education Curriculum for Practice-Oriented Training. Sustainability 2019, 11, 6120 .
AMA StyleSanghyo Lee, Joosung Lee, Yonghan Ahn. Sustainable BIM-Based Construction Engineering Education Curriculum for Practice-Oriented Training. Sustainability. 2019; 11 (21):6120.
Chicago/Turabian StyleSanghyo Lee; Joosung Lee; Yonghan Ahn. 2019. "Sustainable BIM-Based Construction Engineering Education Curriculum for Practice-Oriented Training." Sustainability 11, no. 21: 6120.
Construction companies recognize diversification as a strategy for ensuring financial sustainability. Hence, the aim of this study was to analyze the dynamic relationship between business diversification and business performance of construction companies using the vector error correction model. The expected default frequency, diversification index, domestic construction order, international construction order, gross Domestic Product, Korea composite stock price index, and interest rate were defined as analytical variables. To derive implications for diversification strategies, construction companies were classified into two groups according to the diversification level, and analyzed from the first quarter of 2001 to the fourth quarter of 2017. The results confirm that the dynamic relationship between the diversification strategy and business performance depends on the diversification level of the company. For changes in the markets entered for diversification, construction companies showed different ways of executing the diversification strategy depending on the group; this was partially because of differences in internal and external capabilities of companies, and each company responded differently to market changes. To ensure financial sustainability of a construction company through effective diversification, various conditions must be considered before deciding what impact the diversification strategy could have on the business performance of the company.
Manchun Han; Sanghyo Lee; Jaejun Kim. Effectiveness of Diversification Strategies for Ensuring Financial Sustainability of Construction Companies in the Republic of Korea. Sustainability 2019, 11, 3076 .
AMA StyleManchun Han, Sanghyo Lee, Jaejun Kim. Effectiveness of Diversification Strategies for Ensuring Financial Sustainability of Construction Companies in the Republic of Korea. Sustainability. 2019; 11 (11):3076.
Chicago/Turabian StyleManchun Han; Sanghyo Lee; Jaejun Kim. 2019. "Effectiveness of Diversification Strategies for Ensuring Financial Sustainability of Construction Companies in the Republic of Korea." Sustainability 11, no. 11: 3076.
To realize sustainable construction, planning for future maintenance costs is essential. In the case of multi-family housing, various maintenance issues can be expected to appear starting 10 years after completion. Therefore, preventive maintenance must be implemented in a systematic manner to cope with the problems caused by the natural aging of multi-family dwellings and to maintain a sustainable level of quality for the properties. In this study, maintenance costs were investigated for 224 multi-family housing units aged 20 years or older in Seoul, South Korea. Using Monte Carlo simulation in conjunction with expert interviews, a probabilistic maintenance cost analysis was conducted to analyze and estimate the variability in maintenance costs. The findings of the study propose that the use of probabilistic maintenance cost analysis can be developed into a useful planning tool for determining reasonable future maintenance costs in sustainable construction.
Moonsun Park; Nahyun Kwon; Joosung Lee; Sanghyo Lee; Yonghan Ahn. Probabilistic Maintenance Cost Analysis for Aged Multi-Family Housing. Sustainability 2019, 11, 1843 .
AMA StyleMoonsun Park, Nahyun Kwon, Joosung Lee, Sanghyo Lee, Yonghan Ahn. Probabilistic Maintenance Cost Analysis for Aged Multi-Family Housing. Sustainability. 2019; 11 (7):1843.
Chicago/Turabian StyleMoonsun Park; Nahyun Kwon; Joosung Lee; Sanghyo Lee; Yonghan Ahn. 2019. "Probabilistic Maintenance Cost Analysis for Aged Multi-Family Housing." Sustainability 11, no. 7: 1843.
Over recent decades, it has become essential to establish preventive long-term maintenance plans for public housing developments. Also, deterministic maintenance strategies have been increasingly replaced by those based on reliability and risk, which are probabilistic. Efforts to obtain optimized long-term maintenance plans have included management of service life and prediction of service lifetime. Accordingly, the present research develops a system for various finishing works of public housing and analyzes the service life pattern of each component using a probabilistic approach. For the analysis, this research analyzed 46,201 South Korean public housing maintenance records from the last 21 years and determined the maintenance frequency distribution. The purpose of the research is to suggest efficient long-term maintenance plans using the analyzed results of service life patterns. Results from the analysis showed that each component has a different service life pattern that can be applied to establish the service lifetime and decision making for floating maintenance. Since the interaction between finishing works is affected due to various components and parameters, the results are useful to reduce the uncertainty and risk of deterministic maintenance plans. The meaning of this research is to analyze the service life pattern using a probabilistic approach and recommend how to establish an efficient maintenance system.
Soyeon Park; Yonghan Ahn; Sanghyo Lee. Analyzing the Finishing Works Service Life Pattern of Public Housing in South Korea by Probabilistic Approach. Sustainability 2018, 10, 4469 .
AMA StyleSoyeon Park, Yonghan Ahn, Sanghyo Lee. Analyzing the Finishing Works Service Life Pattern of Public Housing in South Korea by Probabilistic Approach. Sustainability. 2018; 10 (12):4469.
Chicago/Turabian StyleSoyeon Park; Yonghan Ahn; Sanghyo Lee. 2018. "Analyzing the Finishing Works Service Life Pattern of Public Housing in South Korea by Probabilistic Approach." Sustainability 10, no. 12: 4469.
This study investigated defect risks in residential buildings using the Loss Distribution Approach (LDA), a method of identifying and quantifying operational risks in economic terms. Analysis was performed on 7554 defects in 48 residential buildings where defect disputes occurred between 2008 and 2017. Defects were classified into eight types: affected functionality, broken items, corrosion, detachment, incorrect installation, missing task, surface appearance, and water problems. Work types were classified into seven groups: reinforced concrete (RC), masonry, finish, mechanical, electrical, and plumbing (MEP), door and windows, furniture, and miscellaneous. Using a risk matrix from these categories, the frequency distribution and severity distribution for each matrix cell was used to calculate loss distributions; these were combined to find the total loss distribution. The defect risks centered on RC and MEP. For RC, broken items and water leaks due to cracks or damage represented the most severe defects. For MEP, severe defects occurred owing to malfunctions in products and installation problems. Loss distributions can be used to create scenarios and corresponding response plans; thus, when a defect dispute occurs, the cost can be assessed. Furthermore, residential buildings’ loss distributions for each cell can be used to evaluate the types of work where defects occur and to verify relevant subcontractor’s abilities.
Sanghoon Lee; Sanghyo Lee; Jaejun Kim. Evaluating the Impact of Defect Risks in Residential Buildings at the Occupancy Phase. Sustainability 2018, 10, 4466 .
AMA StyleSanghoon Lee, Sanghyo Lee, Jaejun Kim. Evaluating the Impact of Defect Risks in Residential Buildings at the Occupancy Phase. Sustainability. 2018; 10 (12):4466.
Chicago/Turabian StyleSanghoon Lee; Sanghyo Lee; Jaejun Kim. 2018. "Evaluating the Impact of Defect Risks in Residential Buildings at the Occupancy Phase." Sustainability 10, no. 12: 4466.
Existing structural safety diagnosis methods are time-consuming due to personnel-oriented measurement methods and have a limitation that it is difficult to obtain consistent research results. In order to overcome these limitations, this study proposes a structural safety diagnosis method using laser scanning and BIM. In spite of the various studies related to laser scanning and BIM, it is difficult to find a study that verifies the effect of shortening the service period and cost reduction in terms of project management. Therefore, in this study, case analysis of structural safety diagnosis of large-scale civil infrastructure was conducted. In the structural safety diagnosis, the laser scanning data and the BIM model were compared and analyzed to determine the degree of deformation of pipe rack (e.g., truss, column). Laser scanning data reflects the deformation state of large-scale civil infrastructure. On the other hand, the BIM model was constructed by reflecting the state before the transformation with reference to the laser scanning data. Finally, proposed method of structural safety diagnosis saved four months. In terms of manpower saving, 125 man-month was saved. The research findings can provide a quantitative basis for the introduction of laser scanning and BIM technology in the structural safety diagnosis of aging large-scale civil infrastructures. However, the limitations of this study have not been analyzed economically by considering the investment cost (e.g., hardware, software, training, etc.) of laser scanning and BIM technology and the cost saving effect of technology introduction.
Namhyuk Ham; Sang-Hyo Lee. Empirical Study on Structural Safety Diagnosis of Large-Scale Civil Infrastructure Using Laser Scanning and BIM. Sustainability 2018, 10, 4024 .
AMA StyleNamhyuk Ham, Sang-Hyo Lee. Empirical Study on Structural Safety Diagnosis of Large-Scale Civil Infrastructure Using Laser Scanning and BIM. Sustainability. 2018; 10 (11):4024.
Chicago/Turabian StyleNamhyuk Ham; Sang-Hyo Lee. 2018. "Empirical Study on Structural Safety Diagnosis of Large-Scale Civil Infrastructure Using Laser Scanning and BIM." Sustainability 10, no. 11: 4024.
Establishing an effective long-term maintenance plan is essential to ensure the sustainability of a building. Among the various components of a building, the mechanical, electrical, and plumbing (MEP) components are complexly affected by various parameters, such as quality and user pattern, with respect to the service life. Besides, these components are replaced at different points in time, which becomes one of the main risks when establishing a maintenance plan for the building. Therefore, it is very important to consider the uncertainty in calculating the service lives of MEP components in a systematic and reasonable way. This study aims to systemize the MEP components of residential buildings and analyze their service life patterns using a probabilistic approach for long-term maintenance planning. The analysis was performed on 54,318 maintenance cases from 1998 to 2017 at 65 twenty-five-year-old rental apartment buildings in South Korea. Before performing the analysis, a service life matrix was established by classifying the MEP components into 12 types and setting the service life time at 6–25 years. Then, the service life distribution was derived for each MEP component. The probabilistic approach can provide information for rational maintenance decision-making regarding each MEP component as well as basic service life settings. Since the performance of the MEP components deteriorates due to various reasons, de facto uncertainty exists in the service life of each component; thus, the probabilistic approach can serve as an important decision-making method. If probabilistic methods are developed by acquiring the cost data in addition to the frequency of maintenance activity used in this study, a more effective long-term maintenance plan can be established.
Sanghyo Lee; Yonghan Ahn. Analyzing the Long-Term Service Life of MEP Using the Probabilistic Approach in Residential Buildings. Sustainability 2018, 10, 3803 .
AMA StyleSanghyo Lee, Yonghan Ahn. Analyzing the Long-Term Service Life of MEP Using the Probabilistic Approach in Residential Buildings. Sustainability. 2018; 10 (10):3803.
Chicago/Turabian StyleSanghyo Lee; Yonghan Ahn. 2018. "Analyzing the Long-Term Service Life of MEP Using the Probabilistic Approach in Residential Buildings." Sustainability 10, no. 10: 3803.
With the goal of reducing greenhouse gas (GHG) emissions by 26.9% below business-as-usual by 2020, the construction industry is recognized as an environmentally harmful industry because of the large quantity of consumption and waste with which it is associated, and the industry has therefore been requested to become more environmentally friendly. Concrete, a common construction material, is known to emit large amounts of environmentally hazardous waste during the processes related to its production, construction, maintenance, and demolition. To aid the concrete industry’s efforts to reduce its GHG emissions, this study developed a software program that can assess GHG emissions incurred over the life cycle of a concrete product, and a case study was conducted to determine the impact of the proposed concrete assessment program on a construction project.
TaeHyoung Kim; Sanghyo Lee; Chang U. Chae; Hyoungjae Jang; Kanghee Lee. Development of the CO2 Emission Evaluation Tool for the Life Cycle Assessment of Concrete. Sustainability 2017, 9, 2116 .
AMA StyleTaeHyoung Kim, Sanghyo Lee, Chang U. Chae, Hyoungjae Jang, Kanghee Lee. Development of the CO2 Emission Evaluation Tool for the Life Cycle Assessment of Concrete. Sustainability. 2017; 9 (11):2116.
Chicago/Turabian StyleTaeHyoung Kim; Sanghyo Lee; Chang U. Chae; Hyoungjae Jang; Kanghee Lee. 2017. "Development of the CO2 Emission Evaluation Tool for the Life Cycle Assessment of Concrete." Sustainability 9, no. 11: 2116.
This study proposes an Energy Service Company (ESCO) business model to which Certified Emission Reduction (CER) is applied mainly for guaranteed savings. To verify the effectiveness of this ESCO business model, option theory is used. Notably, along with call and put options, which are appropriate for profit structure evaluation of existing guaranteed savings contract, an up and knock-out option was used to analyze the option of securing profit from CER. Based on this analysis, the values of the guarantee acquired by an energy user from the change in the amount of energy savings and the values of an ESCO’s right to profit from energy savings and CER, were calculated. Through these valuations, the profit sharing ratio between energy users and the ESCO was estimated. When the model proposed in this paper was applied to a project case, the profit sharing ratio was 16.37%. The model proposed in this paper is useful for motivating ESCOs to save more energy during operating periods by effectively using profit from CER. Additionally, this model will contribute to the expansion of ESCO market and the effectiveness of energy performance projects in Korea.
Hyein Yi; Sanghyo Lee; Jaejun Kim. An ESCO Business Model Using CER for Buildings’ Energy Retrofit. Sustainability 2017, 9, 591 .
AMA StyleHyein Yi, Sanghyo Lee, Jaejun Kim. An ESCO Business Model Using CER for Buildings’ Energy Retrofit. Sustainability. 2017; 9 (4):591.
Chicago/Turabian StyleHyein Yi; Sanghyo Lee; Jaejun Kim. 2017. "An ESCO Business Model Using CER for Buildings’ Energy Retrofit." Sustainability 9, no. 4: 591.
After the global financial crisis of 2008, the need for risk management arose because it was necessary to minimize the losses in construction management (CM) firms. This was caused by a decreased amount of orders in the Korean CM market, which intensified order competition between companies. However, research results revealed that risks were not being systematically managed owing to the absence of risk management systems. Thus, it was concluded that it was necessary to develop standard operating systems and implement risk management systems in order to manage risks effectively. Therefore, the purpose of this study was to develop a construction risk management system (CRMS) for systematically managing risks. For this purpose, the field operation managers of CM firms were interviewed and surveyed in order to define risk factors. Upon this, a risk assessment priority analysis was performed. Finally, a risk management system that comprised seven modules and 20 sub-modules and was capable of responding systematically to risks was proposed. Furthermore, the effectiveness of this system was verified through on-site inspection. This system allows early response to risks, accountability verification and immediate response to legal disputes with clients by managing risk records.
Kyungmo Park; Sanghyo Lee; Yonghan Ahn. Construction Management Risk System (CMRS) for Construction Management (CM) Firms. Future Internet 2017, 9, 5 .
AMA StyleKyungmo Park, Sanghyo Lee, Yonghan Ahn. Construction Management Risk System (CMRS) for Construction Management (CM) Firms. Future Internet. 2017; 9 (1):5.
Chicago/Turabian StyleKyungmo Park; Sanghyo Lee; Yonghan Ahn. 2017. "Construction Management Risk System (CMRS) for Construction Management (CM) Firms." Future Internet 9, no. 1: 5.
In this paper, we intend to identify the characteristics of occurrence of unsold new housing stocks and draw the implications for the housing business strategy that can effectively cope with the market risk under the Korean housing market. As a result of the analysis, most of the theoretical causality of occurrence of unsold new housing stocks under the three-dimensional Korean housing market was found to correspond to the empirical analysis result. In addition, the chonsei market that produces the characteristic movement of Korean housing market had a significant relation with occurrence of unsold new housing stocks. Because of these results, it is thought that the proposed housing business strategy can effectively cope with the housing market risk. It is thought that we need to additionally examine the financial validity of the proposed housing business model by calculating the cash flow and grope for policy support measures to materialize it on the basis of the analysis result of this paper.
Younghoon Lee; Sanghyo Lee; Jaejun Kim. Analysis of the Dynamic Relationship between Fluctuations in the Korean Housing Market and the Occurrence of Unsold New Housing Stocks. Sustainability 2017, 9, 107 .
AMA StyleYounghoon Lee, Sanghyo Lee, Jaejun Kim. Analysis of the Dynamic Relationship between Fluctuations in the Korean Housing Market and the Occurrence of Unsold New Housing Stocks. Sustainability. 2017; 9 (1):107.
Chicago/Turabian StyleYounghoon Lee; Sanghyo Lee; Jaejun Kim. 2017. "Analysis of the Dynamic Relationship between Fluctuations in the Korean Housing Market and the Occurrence of Unsold New Housing Stocks." Sustainability 9, no. 1: 107.
This study investigated empirically whether multinational business diversification by Korean construction firms contributes to their financial sustainability using the vector error correction model. In this study, the current ratio and the debt ratio were used as proxy variables for financial sustainability. International construction orders and domestic construction orders were used as proxy variables for multinational business diversification for the analysis. Of the models used for analysis in this study, Model A used the current ratio and international and domestic construction orders, and Model B used the debt ratio and international and domestic construction orders. The time-series data utilized consisted of the quarterly data from Q1 of 2001 to Q4 of 2015. The results of the analysis imply that an increase in international construction orders undermines the financial viability of construction firms because of a decrease in the current ratio and an increase in the debt ratio. The results also show that the scrutinized analysis of profitability was insufficient because overseas project orders were not pursued based on a long-term business strategy but on short-term turnover. Therefore, Korean construction firms should recognize the overseas construction market as an independent market, not an alternative to the domestic market, and establish a long-term business strategy to enter overseas markets effectively to secure financial sustainability.
Sanghyo Lee; Yonghan Ahn; Sungwoo Shin. The Impact of Multinational Business Diversification on the Financial Sustainability of Construction Firms in Korea. Sustainability 2016, 8, 997 .
AMA StyleSanghyo Lee, Yonghan Ahn, Sungwoo Shin. The Impact of Multinational Business Diversification on the Financial Sustainability of Construction Firms in Korea. Sustainability. 2016; 8 (10):997.
Chicago/Turabian StyleSanghyo Lee; Yonghan Ahn; Sungwoo Shin. 2016. "The Impact of Multinational Business Diversification on the Financial Sustainability of Construction Firms in Korea." Sustainability 8, no. 10: 997.