Zhang, Su; Bogus, Susan M.; Lippitt, Christopher D.; Migliaccio, Giovanni C. (2017). Estimating Location-Adjustment Factors for Conceptual Cost Estimating Based on Nighttime Light Satellite Imagery. Journal Of Construction Engineering And Management, 143(1).
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Abstract
A fundamental process in construction cost estimation is the appropriate adjustment of costs to reflect project location. Unfortunately, location adjustment factors are not available for all locations. To overcome this lack of data, cost estimators in the United States often use adjustment factors from adjacent locations, referred to as the nearest neighbor (NN) method. However, these adjacent locations may not have similar economic conditions, which limit the accuracy of the NN method. This research proposes a new method of using nighttime light satellite imagery (NLSI) to estimate location adjustment factors where they do not exist. The NLSI method for estimating location adjustment factors was evaluated against an established cost index database, and results show that NLSI can be used to effectively estimate location adjustment factors. When compared with NN and other alternative proximity-based location adjustment methods, the proposed NLSI method leads to a 25-40% reduction of the median absolute error. This work contributes to the body of knowledge by introducing a more accurate method for estimating location adjustment factors which can improve cost estimates for construction projects where location adjustment factors do not currently exist. (C) 2016 American Society of Civil Engineers.
Keywords
Construction Industry; Costing; Industrial Economics; Project Management; Remote Sensing; Location-adjustment Factors; Nighttime Light Satellite Imagery; Construction Cost Estimation; Project Location; United States; Economic Conditions; Nlsi Method; Cost Index Database; Median Absolute Error Reduction; Construction Projects; Nearest Neighbor Method; Urbanization Dynamics; Proxy; Construction Costs; Estimation; Construction Management; Pricing; Cost And Schedule
Sprague, Tyler S. (2018). Jack Christiansen’s Cylindrical Concrete Shells. Journal Of The International Association For Shell And Spatial Structures, 59(2), 131 – 140.
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Abstract
This article examines the early thin shell concrete designs of the structural engineer Jack Christiansen (1927-2017), a 2016 recipient of the Eduardo Torroja Medal. With no proper training in shell behavior, Christiansen started his career designing cylindrical concrete shells based on the 1952 American Society of Civil Engineers (ASCE) Manual 31. This manual, and its approach to solving indeterminate behavior, both directed Christiansen's early design and provided a framework for significant creative work outside its bounds. His designs of long, spanning shells and short, arching shells (between 1954 and 1958) were adapted to a variety of architectural spaces, utilizing emerging structural methods like prestressing. These designs constitute the first era of Christiansen's career, and set the stage for more varied shell geometries to come.
Keywords
Historic Structures; Concrete Shells; Cylindrical Shells; Modernism; Indeterminate Analysis Methods
Park, Kyungmo; Lee, Hyun Woo; Choi, Kunhee; Lee, Seung-hyun. (2019). Project Risk Factors Facing Construction Management Firms. International Journal Of Civil Engineering, 17(3), 305 – 321.
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Abstract
Very little is known about the project risk factors that affect construction management (CM) firms, which often struggle due to a lack of effective risk management practices. This study investigates the risk factors critical to project execution in CM firms and ranks them using the analytic hierarchy process (AHP) and failure mode and effects analysis (FMEA) methods. Interviews with executives at the top 15 Korean CM firms are carried out to identify major risk factors in the CM sector, and a survey is used to develop priority ranking. We find that payment delays and project delays are the two most critical risk factors affecting CM firms because of (1) lack of communication between headquarters and field offices, (2) shift of responsibility from headquarters to a field office, (3) absence of regular monitoring of project progress, and (4) ex-post management practices. The findings presented in this study should assist CM firms in establishing more robust risk management practices, thereby improving firms' profitability, project performance, and customer satisfaction.
Keywords
Analytic Hierarchy Process; Customer Satisfaction; Factor Analysis; Risk Assessment; Risk Management; Analytic Hierarchy Process (ahp); Construction Management; Construction Management Firms; Failure Mode And Effects Analysis; Korea; Management Practices; Risk Factors; Risk Management Practices; Industry
Kim, Taehoon; Kim, Yong-Woo; Cho, Hunhee. (2020). Dynamic Production Scheduling Model Under Due Date Uncertainty in Precast Concrete Construction. Journal Of Cleaner Production, 257.
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Abstract
Precast concrete structures (PCs) are widely used in the construction industry to reduce project delivery times and improve quality. On-time delivery of PCs is critical for successful project completion because the processes involving precast concrete are the critical paths in most cases. However, existing models for scheduling PC production are not adequate for use in dynamic environments where construction projects have uncertain construction schedules because of various reasons such as poor labor productivity, inadequate equipment, and poor weather. This research proposes a dynamic model for PC production scheduling by adopting a discrete-time simulation method to respond to due date changes in real time and by using a new dispatching rule that considers the uncertainty of the due dates to minimize tardiness. The model is validated by simulation experiments based on various scenarios with different levels of tightness and due date uncertainty. The results of this research will contribute to construction project productivity with a reliable and economic precast concrete supply chain. (C) 2020 Elsevier Ltd. All rights reserved.
Keywords
Multiple Production; Demand Variability; Supply Chain; Shop; Management; Minimize; Lines; Precast Concrete Production; Dynamic Simulation; Uncertainty; Production Scheduling; Dispatching Rule
Besser, Lilah M.; Lovasi, Gina S.; Michael, Yvonne L.; Garg, Parveen; Hirsch, Jana A.; Siscovick, David; Hurvitz, Phil; Biggs, Mary L.; Galvin, James E.; Bartz, Traci M.; Longstreth, W. T. (2021). Associations between Neighborhood Greenspace and Brain Imaging Measures in Non-Demented Older Adults: The Cardiovascular Health Study. Social Psychiatry And Psychiatric Epidemiology, 56(9), 1575 – 1585.
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Abstract
Purpose Greater neighborhood greenspace has been associated with brain health, including better cognition and lower odds of Alzheimer's disease in older adults. We investigated associations between neighborhood greenspace and brain-based magnetic resonance imaging (MRI) measures and potential effect modification by sex or apolipoprotein E genotype (APOE), a risk factor for Alzheimer's disease. Methods We obtained a sample of non-demented participants 65 years or older (n = 1125) from the longitudinal, population-based Cardiovascular Health Study (CHS). Greenspace data were derived from the National Land Cover Dataset. Adjusted multivariable linear regression estimated associations between neighborhood greenspace five years prior to the MRI and left and right hippocampal volume and 10-point grades of ventricular size and burden of white matter hyperintensity. Interaction terms tested effect modification by APOE genotype and sex. CHS data (1989-1999) were obtained/analyzed in 2020. Results Participants were on average 79 years old [standard deviation (SD) = 4], 58% were female, and 11% were non-white race. Mean neighborhood greenspace was 38% (SD = 28%). Greater proportion of greenspace in the neighborhood five years before MRI was borderline associated with lower ventricle grade (estimate: - 0.30; 95% confidence interval: - 0.61, 0.00). We observed no associations between greenspace and the other MRI outcome measures and no evidence of effect modification by APOE genotype and sex. Conclusion This study suggests a possible association between greater greenspace and less ventricular enlargement, a measure reflecting global brain atrophy. If confirmed in other longitudinal cohort studies, interventions and policies to improve community greenspaces may help to maintain brain health in older age.
Keywords
Mild Cognitive Impairment; Ventricular Enlargement; Residential Greenness; Hippocampal Atrophy; Volume; Disease; Environment; Progression; Symptoms; Dementia; Neighborhood; Green Space; Mri; Brain Volume; Hippocampal; White Matter
Chen, Cindy X.; Pierobon, Francesca; Jones, Susan; Maples, Ian; Gong, Yingchun; Ganguly, Indroneil. (2022). Comparative Life Cycle Assessment of Mass Timber and Concrete Residential Buildings: A Case Study in China. Sustainability, 14(1).
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Abstract
As the population continues to grow in China's urban settings, the building sector contributes to increasing levels of greenhouse gas (GHG) emissions. Concrete and steel are the two most common construction materials used in China and account for 60% of the carbon emissions among all building components. Mass timber is recognized as an alternative building material to concrete and steel, characterized by better environmental performance and unique structural features. Nonetheless, research associated with mass timber buildings is still lacking in China. Quantifying the emission mitigation potentials of using mass timber in new buildings can help accelerate associated policy development and provide valuable references for developing more sustainable constructions in China. This study used a life cycle assessment (LCA) approach to compare the environmental impacts of a baseline concrete building and a functionally equivalent timber building that uses cross-laminated timber as the primary material. A cradle-to-gate LCA model was developed based on onsite interviews and surveys collected in China, existing publications, and geography-specific life cycle inventory data. The results show that the timber building achieved a 25% reduction in global warming potential compared to its concrete counterpart. The environmental performance of timber buildings can be further improved through local sourcing, enhanced logistics, and manufacturing optimizations.
Keywords
Mass Timber; Embodied Carbon; Climate Change; Carbon Reduction; Building Footprint; Built Environment; Forest Products; Life Cycle Analysis; Environmental Impacts; Wood Laminates; Geography; Concrete; Flooring; Manufacturing; Global Warming; Concrete Construction; Construction Materials; Emissions Trading; Greenhouse Gases; Residential Areas; Energy Consumption; Life Cycle Assessment; Greenhouse Effect; Life Cycles; Construction Industry; Logistics; Floor Coverings; Urbanization; Timber; Urban Environments; Building Components; Emissions; Residential Buildings; Carbon Footprint; Urban Areas; Environmental Impact; Building Construction; Case Studies; Wood Products; Mitigation; Buildings; Timber (structural); United States--us; China
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