Choi, Kunhee, Bae, Junseo, Yin, Yangtian, and Lee, Hyun Woo. (2014). ACT²: Time–Cost Tradeoffs from Alternative Contracting Methods. Journal of Management in Engineering, 37(1).
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Abstract
Incentive/disincentive (I/D) and cost-plus-time (A+B) are two of the most widely used alternative contracting methods (ACMs) for accelerating the construction of highway infrastructure improvement projects. However, little is known about the effects of trade-offs in terms of project schedule and cost performance. This study addresses this problem by creating and testing a stochastic decision support model called accelerated alternative contracting cost-time trade-off (ACT2). This model was developed by a second-order polynomial regression analysis and validated by the predicted error sum of square statistic and paired comparison tests. The results of a descriptive trend analysis based on a rich set of high-confidence project data show that I/D is effective at reducing project duration but results in higher cost compared to pure A+B and conventional methods. This cost-time trade-off effect was confirmed by the ACT2 model, which determines the level of cost-time trade-off for different ACMs. This study will help state transportation agencies promote more effective application of ACMs by providing data-driven performance benchmarking results when evaluating competing acceleration strategies and techniques.
Keywords
Errors (statistics), Project management, Benefit cost ratios, Regression analysis, Construction costs, Infrastructure construction, Contracts and subcontracts, Construction methods
Min, Yohan, Lee, Hyun Woo, & Hurvitz, Philip M. (2023). Clean Energy Justice: Different Adoption Characteristics of Underserved Communities in Rooftop Solar and Electric Vehicle Chargers in Seattle. Energy Research & Social Science, 96.
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Abstract
Concerns over global climate change have led to energy transition to clean energy systems with the development of various clean energy policies. However, social equity issues have emerged in association with the rapid transition of energy systems related to distributed energy resources (DERs), evidenced by disparities in clean energy access. While most existing studies have focused on several variables impacting the adoption of DERs, there is a dearth of studies concerning distributional and recognition justice specifically aimed at investigating: (1) which DER adoption variable is the most important among several variables identified in the literature; and (2) how adoption patterns vary by technologies and communities. The objective of the present study is to answer the two questions by examining the geographic distribution of rooftop solar and electric vehicle (EV) chargers and the related community attributes. Also, the study involves identifying latent variables by addressing inter-correlations among several adoption determinants. The results show that rooftop solar and EV charger adoptions in Seattle present disparities associated with geographic locations and community attributes. In particular, housing variables are the main indicators for rooftop solar adoption and even stronger in communities with low adoption rates. EV charger adoptions are strongly associated with economic variables. Furthermore, spatial inequality of rooftop solar adoption is higher than that of EV charger adoption. The study suggests housing-related support may increase the adoption of both technologies, particularly in communities with low adoption rates. Considering that the installations of rooftop solar and EV chargers were concentrated in particular communities, the study results imply that policies aimed at increasing the adoption of DERs should be tailored to local community characteristics.
Min, Yohan; Lee, Hyun Woo. (2023). Characterization of Vulnerable Communities in Terms of the Benefits and Burdens of the Energy Transition in Pacific Northwest Cities. Journal of Cleaner Production.
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Abstract
Energy transition to renewable sources has occurred along with the development of various clean energy policies aimed at decarbonization and electrification. However, the transition can inadvertently lead to social inequity resulting in increasing burdens on vulnerable communities. Although many studies have tried to define and identify vulnerable communities, there has been no study specifically aimed at characterizing vulnerable communities in terms of the benefits and burdens of such energy transition. In response, the objective of this study is to characterize vulnerable communities by examining rooftop solar adoption and energy expenditure using spatial and mixed-effect models. Rooftop solar adoption operationalizes energy resilience and benefits, and energy expenditure operationalizes energy dependence and burdens of the transition. The study also investigates the link between rooftop solar adoption and energy expenditure by considering city-level variability in three Pacific Northwest cities. The results show that Bellevue has 50.4% less rooftop solar adoption than Portland, while Portland has 16.1% or $223 more energy expenditure than Seattle. On average, an increase in annual energy expenditure of $431 is associated with 29% increase in rooftop solar adoption, specifically Bellevue, Seattle, and Portland by 21.4%, 39.1%, and 26.2%, respectively, but not vice versa. Furthermore, the group of communities more vulnerable in housing attributes has 15.2% less rooftop solar adoption than the group of more vulnerable communities in socioeconomic attributes. In addition, the city centers, commercial areas, or mid-rise and high-rise zones are found to have lower rooftop solar adoption and energy expenditure than other areas. The results suggest that policymakers should consider between-city variability when identifying vulnerable communities. Policies should also be tailored to local communities based on their attributes as communities with similar attributes tend to cluster together. Furthermore, policymakers should focus more on housing and built environment attributes to promote resilient communities.
Ho, Chung; Lee, Hyun Woo; Gambatese, John A. (2020). Application of Prevention Through Design (PTD) to Improve the Safety of Solar Installations on Small Buildings. Safety Science, 125.
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Abstract
As a viable, clean and renewable energy resource, solar energy has gained a significant interest in the US residential sector. Most solar systems are installed on rooftops to take advantage of available space and reduce land use. However, this installation environment also exposes workers to unique safety hazards related to existing roof conditions such as slippery roofing materials, irregular roof layouts, and steep roof slopes. Although Prevention through Design (ND) has been widely considered as an effective way to address safety issues during the design phase, little to no studies have applied ND to improve safety in solar energy installations. To fill this knowledge gap, this research aimed to investigate how, during the design phase, to address the safety concerns of solar workers when installing solar energy systems on residential buildings. Through a series of interviews, four case studies, and a seminar, seven solar ND attributes were identified: roofing materials, roof slopes, roof accessories, panel layouts, fall protection systems, lifting methods and electrical systems. Based on the attributes, a ND protocol was developed that can serve as guidance for implementing ND in solar installations. This paper presents the research activities and findings, and feedback gained from solar contractors through a seminar on the study. The study is expected to contribute to reducing safety hazards by implementing ND, help improve safety performance in solar installations on small residential buildings and support the promotion of safety in sustainable construction.
Keywords
Roofing Materials; Renewable Energy Sources; Sustainable Construction; Solar Energy; Clean Energy; Construction Safety; Prevention Through Design; Small Buildings; Solar Installations; Buildings (structures); Construction Industry; Hazards; Occupational Safety; Roofs; Safety; Solar Power; Sustainable Development; Steep Roof Slopes; Design Phase; Solar Energy Installations; Solar Workers; Installing Solar Energy Systems; Residential Buildings; Seven Solar Ptd Attributes; Roof Accessories; Ptd Protocol; Solar Contractors; Safety Performance; Viable Energy Resource; Clean Energy Resource; Renewable Energy Resource; Us Residential Sector; Solar Systems; Installation Environment; Unique Safety Hazards; Roof Conditions; Slippery Roofing Materials; Irregular Roof Layouts; Issues; Accident Prevention; Protocol; Energy Sources; Residential Areas; Land Use; Prevention; Design; Falls; Occupational Hazards; Contractors; Residential Energy; Protection Systems; Renewable Energy; Buildings; Roofing; Layouts
Nnaji, Chukwuma; Karakhan, Ali A.; Gambatese, John; Lee, Hyun Woo. (2020). Case Study to Evaluate Work-Zone Safety Technologies in Highway Construction. Practice Periodical On Structural Design And Construction, 25(3).
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Abstract
The construction industry is known for its conservative approach toward adopting new, emerging technologies. This conservative approach for adopting technology is caused by multiple factors including the lack of adequate resources to guide construction practitioners in the process of evaluating whether a construction firm should adopt a certain technology or not. Previous studies have already proposed rigorous protocols for evaluating work-zone technologies, but the implementation of such protocols is still unclear to many construction practitioners. The objective of this study is to provide a case study example of how evaluation protocols can be used in practice to determine whether a firm should adopt a certain work-zone technology. The case study focused on assessing the usefulness of commercially available work-zone intrusion alert technologies (WZIATs). The results of the evaluation revealed that some WZIATs could be more attractive to construction organizations and agencies in terms of providing louder alarms, being more mobile, and allowing a higher transmission range. The case study example discussed in this study is expected to provide invaluable practical information to practitioners in the construction industry interested in evaluating and adopting emerging technologies.
Keywords
Construction Industry; Mobile Radio; Occupational Safety; Road Building; Road Safety; Highway Construction; Conservative Approach; Construction Practitioners; Construction Firm; Rigorous Protocols; Work-zone Technology; Case Study Example; Evaluation Protocols; Commercially Available Work-zone Intrusion Alert Technologies; Construction Organizations; Evaluate Work-zone Safety Technologies; Speed; Signs; Work Zone; Safety Technology; Intrusion Alert; Evaluation Protocol
Rodriguez, Barbara X.; Huang, Monica; Lee, Hyun Woo; Simonen, Kathrina; Ditto, Jim. (2020). Mechanical, Electrical, Plumbing and Tenant Improvements over the Building Lifetime: Estimating Material Quantities and Embodied Carbon for Climate Change Mitigation. Energy And Buildings, 226.
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Abstract
The building industry is expanding its ability to mitigate the environmental impacts of buildings through the application of life cycle assessment (LCA). Most building LCA studies focus on core and shell (C&S) and rarely assess mechanical, electrical, and plumbing (MEP) and tenant improvements (TI). However, C&S typologies in the commercial sector pose particular challenges to achieving net zero carbon due to the numerous renovations these building undergo through during their service life. MEP and TI are installed multiple times over the lifetime of commercial buildings leading to cumulative environmental impact caused by increasing material quantities and embodied carbon (EC). This study aimed to establish a preliminary range of material quantities and embodied carbon impacts for MEP and TI components, focusing on commercial office buildings in the Pacific Northwest. The first research stage involved quantifying material quantities while a second stage aimed to calculate Embodied Carbon Coefficients (ECC) and LCA impacts using different data sources. The embodied carbon estimates ranged from 40 to 75 kg CO(2)e/m(2) for MEP and 45-135 kg CO(2)e/m(2) for TI. However, with recurring instalments during a life span of 60 years the impacts become comparable to known impacts of core and shell systems. (C) 2020 Elsevier B.V. All rights reserved.
Keywords
Embodied Carbon; Life Cycle Assessment; Tenant Improvement; Mechanical; Electrical And Plumbing
Choi, Kunhee; Bae, Junseo; Yin, Yangtian; Lee, Hyun Woo. (2021). Act(2): Time Cost Tradeoffs from Alternative Contracting Methods. Journal Of Management In Engineering, 37(1).
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Abstract
Incentive/disincentive (I/D) and cost-plus-time (A+B) are two of the most widely used alternative contracting methods (ACMs) for accelerating the construction of highway infrastructure improvement projects. However, little is known about the effects of trade-offs in terms of project schedule and cost performance. This study addresses this problem by creating and testing a stochastic decision support model called accelerated alternative contracting cost-time trade-off (ACT(2)). This model was developed by a second-order polynomial regression analysis and validated by the predicted error sum of square statistic and paired comparison tests. The results of a descriptive trend analysis based on a rich set of high-confidence project data show that I/D is effective at reducing project duration but results in higher cost compared to pure A+B and conventional methods. This cost-time trade-off effect was confirmed by the ACT(2) model, which determines the level of cost-time trade-off for different ACMs. This study will help state transportation agencies promote more effective application of ACMs by providing data-driven performance benchmarking results when evaluating competing acceleration strategies and techniques. (C) 2020 American Society of Civil Engineers.
Keywords
Highway; Construction; Model; Alternative Contracting Methods; Cost-plus-time; A Plus B; Incentive; Infrastructure Trend; Time-cost Trade-off
Soltaninejad, Mostafa; Fardhosseini, Mohammad Sadra; Kim, Yong Woo. (2021). Safety Climate and Productivity Improvement of Construction Workplaces Through the 6S System: Mixed-Method Analysis of 5S and Safety Integration. International Journal Of Occupational Safety & Ergonomics, 28(3), 1811-1821.
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Abstract
The purpose of this study is to develop a framework for integrating essential safety practices (visualization, job safety analysis and plan-do-check-act) into 5S steps and validate it. First, 18 interviews with a snowball sample of construction workers, safety representatives, supervisors and site and project managers were conducted. A grounded theory method was utilized to code the interview data. The results revealed that the studied construction companies implement a systematic safety-based methodology to minimize construction work injuries. Second, to validate the proposed framework, a pre-test and post-test study was applied. The case and control groups (26 participants) answered a 6S questionnaire before the 6S system and 1 month after implementation. The results revealed that safety climate and productivity significantly increased for the case group but reduced for the control group during time.
Keywords
5s Method; 6s System; Grounded Theory; Lean Construction; Productivity; Safety Climate; Health; Management; Leadership; Culture; Impact
Su, Shu; Li, Xiaodong; Zhu, Chen; Lu, Yujie; Lee, Hyun Woo. (2021). Dynamic Life Cycle Assessment: A Review of Research for Temporal Variations in Life Cycle Assessment Studies. Environmental Engineering Science, 38(11), 1013 – 1026.
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Abstract
Life cycle assessment (LCA) is a comprehensive and important environmental management tool around the world. However, lacking temporal information has been a major challenge. In the past decade, dynamic LCA (DLCA), which incorporates temporal variations into assessment, has been an emerging research topic with increasing publications. A timely comprehensive review is needed to present current progress and discuss future directions. This article reviews 144 DLCA articles quantitatively and qualitatively. A bibliometric approach is adopted to conduct co-occurrence analysis and cluster analysis of DLCA studies. The research progress, approaches, and limitations of three temporal variation types (i.e., dynamic life cycle inventory, dynamic characterization factors, and dynamic weighting factors) in DLCA studies are systematically analyzed and discussed. It is concluded that: (1) dynamic inventory analysis is usually conducted by collecting time-differentiated data at each time step. Field monitoring, simulation, scenario analysis, and prediction based on historical data are common approaches. (2) Dynamic characterization studies primarily focus on two impact categories: global warming and toxicity. More studies are in need. (3) Various methods and indicators (i.e., dynamic pollution damage cost, temporal environmental policy targets, and discount rates) are used to solve the dynamic weighting issue, and they have specific limitations. Finally, three interesting topics are discussed: comparison between dynamic and static results, the large data amount issue, and the trend of tools development. This review offers a holistic view on temporal variations in DLCA studies and provides reference and directions for future dynamic studies.
Keywords
Literature Reviews; Cluster Analysis (statistics); Global Warming; Environmental Management; Discount Prices; Emission Inventories; Dynamic Characterization; Dynamic Inventory Analysis; Dynamic Weighting; Environmental Impact; Life Cycle Assessment; Temporal Variation; Cluster Analysis; Life Cycle; 'current; Dynamic Inventory Analyse; Dynamic Lca; Environmental Management Tool; Inventory Analysis; Research Topics; Temporal Information; Dependent Climate Impact; Greenhouse-gas Emission; Biogenic Carbon; Assessment Framework; Fresh-water; Electricity-generation; Energy Efficiency; Wheat Production; Embodied Energy; Time
Shakouri, Mahmoud; Lee, Hyun Woo. (2016). Mean-Variance Portfolio Analysis Data For Optimizing Community-Based Photovoltaic Investment. Data In Brief, 6, 840 – 842.
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Abstract
The amount of electricity generated by Photovoltaic (PV) systems is affected by factors such as shading, building orientation and roof slope. To increase electricity generation and reduce volatility in generation of PV systems, a portfolio of PV systems can be made which takes advantages of the potential synergy among neighboring buildings. This paper contains data supporting the research article entitled: PACPIM: new decision-support model of optimized portfolio analysis for community-based photovoltaic investment [1]. We present a set of data relating to physical properties of 24 houses in Oregon, USA, along with simulated hourly electricity data for the installed PV systems. The developed Matlab code to construct optimized portfolios is also provided in Supplementary materials. The application of these files can be generalized to variety of communities interested in investing on PV systems. (C) 2016 The Authors. Published by Elsevier Inc.
Keywords
Community Solar; Photovoltaic System; Portfolio Theory; Energy Optimization; Electricity Volatility