Bender, W.; Waytuck, D.; Wang, S.; Reed, D. A. (2018). In Situ Measurement of Wind Pressure Loadings on Pedestal Style Rooftop Photovoltaic Panels. Engineering Structures, 163, 281 – 293.
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Abstract
The installation of rooftop photovoltaic (PV) arrays is increasing throughout the US. Until recently, pedestal type PV framing systems for rooftops were basically designed using procedures from the ASCE7-10 Components and Cladding Standard for rooftop equipment. The 2011 Japanese Standard Load design guide on structures for photovoltaic arrays was useful in characterizing the pressure coefficients on rooftops, but the Standard employs different wind speed and importance factors, making its use in the US quite limited, Even the updated 2017 version is written for a different audience. Because rooftop pressure loadings are high due to flow separation, SEAOC and other organizations contracted boundary layer wind tunnel tests of panels attached to rooftops to ascertain if the ASCE7-10 equipment loadings were appropriate. The investigations resulted in new standards for pedestal-style arrays that appear in Chapter 29 of ASCE7-16. However, the new standards are limited to simple geometries and orientations, and the dynamics of the simply-supported thin PV plates do not appear to be considered. Questions regarding the ability of the boundary tunnels to simulate accurately the turbulence at the scale required for the attached panels have been raised. In response, very limited full-scale investigations in large-scale tunnels and in situ have been undertaken to calibrate the tunnel results. The results of this paper represent one of these calibration investigations. Specifically, in situ full-scale net wind pressure loadings on a rooftop PV array in a pedestal-style framing system located on the three story Hogue Technology Building of Central Washington University (CWU) in Ellensburg, Washington were measured. The CWU campus has a rural setting in a region with steady winds: Ellensburg is located in the Kittitas Breezeway portion of the Northwest wind power region. Indeed, the Wild Horse Wind and Solar Farm is located on the outskirts of town. The data described here were collected from April through August 2014. The measured net pressure coefficient time series were similar to those for rooftop pressure loadings for low-rise buildings described in the literature such as the Wind Engineering Research Field Laboratory at Texas Tech University (Ham and Bienkiewicz, 1998 [1]; Levitan and Mehta, 1992 [2]). The analysis of the net pressure time series data included an examination of the minimum, maximum, mean, and RMS values. Preliminary results suggest that the range of the values is larger than assumed in the ASCE7 Standard, and that the magnitude of the loadings vary considerably spatially over the multiple panel array. The pressure loading measurements are ongoing.
Keywords
Building Integrated Photovoltaics; Buildings (structures); Calibration; Design Engineering; Pressure Measurement; Roofs; Solar Cell Arrays; Standards; Time Series; Turbulence; Wind Tunnels; Japanese Standard Load Design Guide; Wind Pressure Loading Measurements; Asce7-10 Components-cladding Standard; Tunnel Calibration; Texas Tech University; Kittitas Breezeway Portion; Wild Horse Wind And Solar Farm; Ellensburg; Central Washington University; Hogue Technology Building; Boundary Layer Wind Tunnel Test; Flow Separation; Multiple Panel Array; Wind Engineering Research Field Laboratory; Net Pressure Coefficient Time Series; Northwest Wind Power Region; Pedestal-style Framing System; Pv Plates; Rooftop Equipment; Pedestal Style Rooftop Photovoltaic Panels; Solar-arrays; Loads; Simulation; Wind Engineering; Photovoltaic Modules; Solar Energy; Full-scale Measurements; Wind Loadings; Photovoltaic Cells; Roofing; Wind Power; Structural Engineering; Boundary Layers; Cladding; Wind Tunnel Testing; Solar Cells; In Situ Measurement; Framing; Photovoltaics; Engineering Research; Wind Measurement; Pressure; Panels; Wind Pressure; Design Standards; Fluid Dynamics; Low Rise Buildings; Colleges & Universities; Wind Speed; United States--us
Lee, Wonil; Migliaccio, Giovanni C. (2018). Temporal Effect of Construction Workforce Physical Strain on Diminishing Marginal Productivity at the Task Level. Journal Of Construction Engineering And Management, 144(9).
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Abstract
Physiological status and environmental stressors are known to influence workforce performance at the individual worker level. A previous study, which conducted a cross-sectional comparison in repetitive material-handling construction activities, suggested that a U-shaped relationship existed between physical strain and productivity at the group level. This research revisits those findings to further investigate the U-curve relationship between physical strain and productivity at the group level and validate the concept of diminishing marginal productivity. Heart rates were measured as an indicator of subjects' physical strain, whereas task productivity was estimated by work sampling. Eighty person-hour data were converted into panel data sets by dividing each subject's 4-h experimental data into 5-min intervals. These data sets were subsequently used to evaluate the effects of time on physical strain and productivity with 5-min lags. The study found a U-curve relationship between physical strain and task-level productivity at the group level while controlling for individual characteristics. The U-shape relationship was constant in the low-performance and high-performance groups, although the degrees of the polynomials differed. Productive workers will remain more productive than low-productive workers with increased physical strain.
Keywords
Construction Industry; Industrial Psychology; Labour Resources; Occupational Health; Polynomials; Productivity; Physiological Status; Environmental Stressors; U-shaped Relationship; Productive Workers; Polynomials Degree; Diminishing Marginal Productivity; Construction Workforce Physical Strain; Labor Productivity; Scientific Management; Shift Work; Performance; Model; Taylorism; Burnout; Design; Impact; Safety; Construction Productivity; Labor And Personal Issue; Work Physiology; Physical Strain
Abdirad, Hamid; Dossick, Carrie S. (2019). Normative and Descriptive Models for COBie Implementation: Discrepancies and Limitations. Engineering, Construction And Architectural Management, 26(8), 1820 – 1836.
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Abstract
Purpose The purpose of this paper is to inquire into the reasons why Construction Operation Building Information Exchange (COBie) has not become mainstream across the construction industry despite the significant attempts to promote it. Design/methodology/approach This paper framed and compared the normative model of COBie to a descriptive model of COBie. The normative model was based on the assumptions and planned procedures outlined in the COBie documentation. The descriptive model was developed through a case study of COBie implementation, with ethnographic observations, interviews and artifact analysis as the data collection methods and thematic analysis as the data analysis method. Findings The comparative analysis of the normative and descriptive models showed that the underlying normative assumptions of COBie can be challenged in its implementation. In the case study, implementing COBie disrupted the conventional practice of few participating firms as the data requirements and the expected sequences and timelines of tasks were not aligned with the industry norms for exchanging data. Furthermore, the normative model of COBie could not account for the unanticipated variability in the internal routines of firms for submittal production. Practical implications - COBie, as an instruction-based model, may not provide enough flexibility for some firms to adapt to its requirements such that COBie tasks become integrated with their existing workflows. COBie tasks may become additional efforts, and at times, conflict with the industry norms and firms' routines, and therefore, disrupt the efficiency goals. Originality/value This paper provides empirical evidence to clarify why implementing COBie has not been as efficient for all industry players as expected.
Keywords
Construction Industry; Information Dissemination; Information Systems; Cobie; Hand Over; Information And Communication Technologies; Information Exchanges; Operations; Facilities Management; Bim; Construction; Case Study; Information Exchange; Information And Communication Technology (ict) Applications; Project Hand Over
Huang, Ruizhu; Moudon, Anne, V; Zhou, Chuan; Saelens, Brian E. (2019). Higher Residential and Employment Densities Are Associated with More Objectively Measured Walking in the Home Neighborhood. Journal Of Transport & Health, 12, 142 – 151.
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Abstract
Introduction: Understanding where people walk and how the built environment influences walking is a priority in active living research. Most previous studies were limited by self-reported data on walking. In the present study, walking bouts were determined by integrating one week of accelerometry, GPS, and a travel log data among 675 adult participants in the baseline sample of the Travel Assessment and Community study at Seattle, Washington in the United State. Methods: Home neighborhood was defined as being within 0.5 mile of each participants' residence (a 10-min walk), with home neighborhood walking defined as walking bout lines with at least one GPS point within the home neighborhood. Home neighborhood walkability was constructed with seven built environment variables derived from spatially continuous objective values (SmartMaps). Collinearity among neighborhood environment variables was analyzed and variables that were strongly correlated with residential density were excluded in the regression analysis to avoid erroneous estimates. A Zero Inflated Negative Binomial (ZINB) served to estimate associations between home neighborhood environment characteristics and home neighborhood walking frequency. Results: The study found that more than half of participants' walking bouts occurred in their own home neighborhood. Higher residential density and job density were the two neighborhood walkability measures related to higher likelihood and more time walking in the home neighborhood, highest tertile residential density (22.4-62.6 unit/ha) (coefficient= 1.43; 95% CI 1.00-2.05) and highest tertile job density (12.4-272.3 jobs/acre) (coefficient= 1.62; 1.10-2.37). Conclusions: The large proportion of walking that takes place in the home neighborhood highlights the importance of continuing to examine the impact of the home neighborhood environment on walking. Potential interventions to increase walking behavior may benefit from increasing residential and employment density within residential areas.
Keywords
Body-mass Index; Built Environment; Physical-activity; Land Uses; Epidemiology; Selection; Location; Obesity; Travel Assessment And Community; Smartmaps; Neighborhood Environment; Physical Activity; Walking
Nkyekyer, Esi W.; Dannenberg, Andrew L. (2019). Use and Effectiveness of Health Impact Assessment in the Energy and Natural Resources Sector in the United States, 2007 – 2016. Impact Assessment & Project Appraisal, 37(1), 17 – 32.
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Abstract
Decisions made in the energy and natural resources sector can affect public health. This report reviews the characteristics and assesses the effectiveness of health impact assessments (HIAs) conducted in this sector. A total of 30 HIAs conducted in 14 states in the United States were identified using a targeted literature search. Five HIAs illustrative of the different source and sub-sector categories, and with identifiable impacts on decision-making processes were selected for review. An existing conceptual framework (Wismar) was used to assess the effectiveness of the five selected HIAs on decision-making related to non-renewable energy, renewable energy, mining, and energy conservation. The 30 HIAs were performed for a variety of projects and assessed health impacts ranging from metabolic disorders to community livability. Eight of the 30 reports were incorporated into environmental impact assessments. All five selected HIAs were generally effective and raised awareness of the health effects of the projects being assessed; four were directly effective and led to changes in final project decisions. Their variable effectiveness may be related to the extent of community engagement and consideration of equity issues, differences in the details and quality of monitoring and evaluation plans devised as part of the HIA process, and whether the outcomes of monitoring and evaluation are reported.
Keywords
Health Impact Assessment; Health Equity; Natural Resources; Environmental Impact Analysis; Power Resources; U.s. States; Energy Conservation; United States; Decision-making Effectiveness; Energy And Natural Resources; Wismar Framework; Horizon Oil-spill; Wind Turbine Noise; Quality-of-life; Environmental-health; Gas Development; Mental-health; Exposure; Vicinity; Hazards; Sleep; Environmental Assessment; Public Health; Metabolic Disorders; Renewable Energy; Monitoring; Decision Making; Evaluation; Environmental Impact; Community Involvement; Environmental Impact Assessment; Renewable Resources; Decisions; Impact Analysis; Mining; United States--us
Abramson, Daniel B. (2020). Ancient and Current Resilience in the Chengdu Plain: Agropolitan Development Re-‘Revisited’. Urban Studies (sage Publications, Ltd.), 57(7), 1372 – 1397.
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Abstract
The Dujiangyan irrigation system, China's largest, is one of the world's most important examples of sustainable agropolitan development, maintained by a relatively decentralised system of governance that minimises bureaucratic oversight and depends on significant local autonomy at many scales down to the household. At its historic core in the Chengdu Plain, the system has supported over 2000 years of near-continuously stable urban culture, as well as some of the world's highest sustained long-term per-hectare productivity and diversity of grain and other crops, especially considering its high population density, forest cover, general biodiversity and flood management success. During the past decade, rapid urban expansion has turned the Chengdu Plain from a net grain exporter into a grain importer, and has radically transformed its productive functioning and distinctive scattered settlement pattern, reorganising much of the landscape into larger, corporately-managed farms, and more concentrated and infrastructure-intensive settlements of non-farming as well as farming households. Community-scale case studies of spatial-morphological and household socio-economic variants on the regional trend help to articulate what is at stake. Neither market-driven 'laissez-faire' rural development nor local state-driven spatial settlement consolidation and corporatisation of production seem to correlate well with important factors of resilience: landscape heterogeneity; crop diversity and food production; permaculture; and flexibility in household independence and choice of livelihood. Management of the irrigation system should be linked to community-based agricultural landscape preservation and productive dwelling, as sources of adaptive capacity crucial to the social-ecological resilience of the city-region, the nation and perhaps all humanity.
Keywords
Urbanization; Economies Of Agglomeration; Agricultural Ecology; Sustainability; Urban Planning; Land Use; China; Agglomeration/urbanisation; Agroecosystems; Environment/sustainability; History/heritage/memory; Redevelopment/regeneration; Cultivated Land; Countryside; Expansion; State; Rise; Modernization; Conservation; Integration; Earthquake; Agglomeration; Urbanisation; Environment; History; Heritage; Memory; Redevelopment; Regeneration; Population Density; Production; Farming; Agriculture; Decentralization; Autonomy; Food Production; Households; Landscape; Resilience; Rural Development; Food; Farms; Regional Development; Productivity; Economic Development; Case Studies; Agricultural Production; Biodiversity; Sustainable Development; Governance; Preservation; Crops; Flood Management; Irrigation; Permaculture; Radicalism; Socioeconomic Factors; Grain; Flexibility; Heterogeneity; Variants; Urban Areas; Irrigation Systems; Rural Communities; Bureaucracy; Landscape Preservation; Agricultural Land; Flood Control; Density; Infrastructure; Urban Sprawl; Livelihood; Farm Management; Rural Areas; Urban Farming; Settlement Patterns; Agribusiness; Market Economies
Hess, Chris; Colburn, Gregg; Crowder, Kyle; Allen, Ryan. (2020). Racial Disparity in Exposure to Housing Cost Burden in the United States: 1980-2017. Housing Studies.
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Abstract
This article uses the Panel Study of Income Dynamics to analyse Black-White differences in housing cost burden exposure among renter households in the USA from 1980 to 2017, expanding understanding of this phenomenon in two respects. Specifically, we document how much this racial disparity changed among renters over almost four decades and identify how much factors associated with income or housing costs explain Black-White inequality in exposure to housing cost burden. For White households, the net contribution of household, neighbourhood and metropolitan covariates accounts for much of the change in the probability of housing cost burden over time. For Black households, however, the probability of experiencing housing cost burden continued to rise throughout the period of this study, even after controlling for household, neighbourhood and metropolitan covariates. This suggests that unobserved variables like racial discrimination, social networks or employment quality might explain the increasing disparity in cost burden among for Black and White households in the USA.
Keywords
Cost Burden; Housing Cost; Racial Inequality; Income Inequality; Rent Burden; Affordability; Neighborhoods; Segregation; Dynamics; Hardship; Prices; Market; Poor
Martins, Antonio Miguel; Serra, Ana Paula; Martins, Francisco Vitorino; Stevenson, Simon. (2020). House Price Dynamics and Bank Herding: European Empirical Evidence. Journal Of Real Estate Research, 42(3), 365 – 396.
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Abstract
This paper examines house price dynamics, bank herding behavior, and the linkages between them. The analysis presented indicates that prior to the financial crisis, non-fundamental factors played a significant role in several European countries, including the United Kingdom, Spain, Denmark, Sweden, and Ireland. We also provide evidence indicative of herding behavior in the residential mortgage loan market. Finally, Granger causality tests show that non-fundamentally justified price dynamics contributed to the herding displayed by lenders and that this behavior was a response by banks as a group to common information on residential property assets.
Keywords
Bubbles; Market; Behavior; Fundamentals; Constraints; Policy; Model; House Prices; Mortgages; Price Bubble; Herding Behavior
Wasserman, Ben A.; Paccard, Antoine; Apgar, Travis M.; Des Roches, Simone; Barrett, Rowan D. H.; Hendry, Andrew P.; Palkovacs, Eric P. (2020). Ecosystem Size Shapes Antipredator Trait Evolution in Estuarine Threespine Stickleback. Oikos, 129(12), 1795 – 1806.
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Abstract
Ecosystem size is known to influence both community structure and ecosystem processes. Less is known about the evolutionary consequences of ecosystem size. A few studies have shown that ecosystem size shapes the evolution of trophic diversity by shaping habitat heterogeneity, but the effects of ecosystem size on antipredator trait evolution have not been explored. Ecosystem size may impact antipredator trait evolution by shaping predator presence (larger ecosystems have longer food chains) and habitat complexity (larger ecosystems may have more diverse habitat structure). We tested these effects using threespine stickleback from bar-built estuaries along the Central Coast of California. These stickleback populations are polymorphic forEctodysplasin-A(Eda), a gene that controls bony lateral plates used as antipredator defense. We inferredEdagenotypes from lateral plate phenotypes and show that the frequency of the complete (C) allele, which is associated with greater number of lateral plates, increases as a function of ecosystem size. Predator presence and habitat complexity are both correlated to ecosystem size. The strongest proximate predictor ofEdaallele frequencies was the presence of predatory fishes (steelhead trout and sculpin). Counter to expectations, habitat complexity did not have a strong modifying effect onEdaallele frequencies. Our results point to the importance of ecosystem size for determining predator presence as being the primary pathway to evolutionary effects. Ecosystem size has received much attention in ecology. Our work shows that it may be an important determinant of adaptive evolution in wild populations.
Keywords
Food-chain Length; Gasterosteus-aculeatus; Adaptive Radiation; Lateral Plates; Ecological Opportunity; Natural-selection; Armor; Fish; Predation; Area; Antipredator Traits; Bar-built Estuaries; Ecosystem Size; Ectodysplasin Agene; Gasterosteus Aculeatus
Costa, Ana; Sass, Victoria; Kennedy, Ian; Roy, Roshni; Walter, Rebecca J.; Acolin, Arthur; Crowder, Kyle; Hess, Chris; Ramiller, Alex; Chasins, Sarah. (2021). Toward a Cross-Platform Framework: Assessing the Comprehensiveness of Online Rental Listings. Cityscape, 23(2), 327 – 339.
Abstract
Research on rental housing markets in the United States has traditionally relied on national or local housing surveys. Those sources lack temporal and spatial specificity, limiting their use for tracking short-term changes in local markets. As rental housing ads have transitioned to digital spaces, a growing body of literature has utilized web scraping to analyze listing practices and variations in rental market dynamics. Those studies have primarily relied on one platform, Craigslist, as a source of data. Despite Craigslist's popularity, the authors contend that rental listings from various websites, rather than from individual ones, provide a more comprehensive picture. Using a mixed-methods approach to study listings across various platforms in five metropolitan areas, this article demonstrates considerable variation in both the types of rental units advertised and the features provided across those platforms. The article begins with an account of the birth and consolidation of online rental platforms and emergent characteristics of several selected websites, including the criteria for posting, search parameters, search results priority, and first-page search results. Visualizations are used to compare features such as the 40th percentile of rent, rent distribution, and bedroom size based on scraped data from six online platforms (Padmapper, Forrent.com , Trulia, Zillow, Craigslist, and GoSection8), 2020 Fair Market Rents, and 2019 American Community Survey data. The analyses indicate that online listing platforms target different audiences and offer distinct information on units within those market segments, resulting in markedly different estimates of local rental costs and unit size distribution depending on the platform.