Showing papers in "Frontiers in Built Environment in 2021"
TL;DR: In this article, the authors examined existing life cycle assessments of wooden buildings and found that the average reported values of embodied greenhouse gas emissions of wooden building are one-third to half of the embodied emissions reported from buildings in general.
Abstract: Buildings play a vital role in reaching the targets stated by the Intergovernmental Panel on Climate Change to limit global warming to 1.5 degrees. Increasing the use of wood in construction is a proposed upcoming strategy to reduce the embodied greenhouse gas emissions of buildings. This study examines existing life cycle assessments of wooden buildings. The aim is to investigate embodied greenhouse gas emission results reported, as well as methodological approaches applied in existing literature. The study applies the protocol for Systematic Literature Reviews and finds 79 relevant papers. From the final sample, the study analyses 226 different scenarios in-depth in terms of embodied emissions, life cycle assessment method, life cycle inventory modelling and biogenic carbon approach. The analysis shows that the average reported values of embodied greenhouse gas emissions of wooden buildings are one-third to half of the embodied emissions reported from buildings in general. Additionally, from the analysis of the final sample we find that the majority of wooden building life cycle assessments apply similar methods and often leave out biogenic carbon from the assessment or simply do not declare it. This implies that the focus on variability in the different methods applied in wooden building life cycle assessments needs to be increased to establish the relationship between methodological choices and embodied emissions of wooden buildings. Further, transparency and conformity in biogenic carbon accounting in life cycle assessments is essential to enhance comparability between life cycle assessment studies and to avoid distortions in embodied GHG emission results.
18 citations
TL;DR: In this article, a comprehensive review on nonlinear building structures with and without passive dampers subjected to earthquake loading is presented, and the significance of the dynamic pushover analysis is discussed from the viewpoint of analysis of limit states under earthquake ground motions of magnitude larger than the code-specified level.
Abstract: The optimal and smart design of nonlinear building structures with and without passive dampers subjected to earthquake loading is of great concern in the structural design of building structures. The research started around 1980 and many investigations have been conducted. A comprehensive review on this subject is made in this article. After the description of essential features of the optimal design problem of nonlinear building structures under earthquake ground motions, analysis types of optimization problems are explained and the significance of the dynamic pushover analysis is discussed from the viewpoint of analysis of limit states under earthquake ground motions of magnitude larger than the code-specified level. Then, the categorization by the response of frames and dampers was made. In this categorization, several subjects are discussed first: (i) Optimal design of bare nonlinear building frames under seismic loading, (ii) Optimal design of nonlinear dampers for elastic building frames under seismic loading, (iii) Optimal design of linear dampers for nonlinear building frames under seismic loading, (iv) Optimal design of nonlinear building frames with specified nonlinear dampers under seismic loading, (v) Optimal design of nonlinear dampers for specified nonlinear building frames under seismic loading, (vi) Simultaneous optimization of elastic-plastic building structures and passive dampers. Finally, the classification of researches in view of solution strategies is conducted for providing another viewpoint.
16 citations
TL;DR: In this article, a first-principles model, airborne transmission via outdoor route (ATOR), was developed to simulate airborne pathogen generation, natural decay, outdoor dispersion, apartment entry, and inhalation exposure of susceptible persons in neighboring apartments.
Abstract: The coronaviruses have inflicted health and societal crises in recent decades. Both SARS CoV-1 and 2 are suspected to spread through outdoor routes in high-density cities, infecting residents in apartments on separate floors or in different buildings in many superspreading events, often in the absence of close personal contact. The viability of such mode of transmission is disputed in the research literature, and there is little evidence on the dose–response relationship at the apartment level. This paper describes a study to examine the viability of outdoor airborne transmission between neighboring apartments in high density cities. A first-principles model, airborne transmission via outdoor route (ATOR), was developed to simulate airborne pathogen generation, natural decay, outdoor dispersion, apartment entry, and inhalation exposure of susceptible persons in neighboring apartments. The model was partially evaluated using a smoke tracer experiment in a mock-up high-density city site and cross-checking using the computational fluid dynamics (CFD) models. The ATOR model was used to retrospectively investigate the relationship between viral exposure and disease infection at an apartment level in two superspreading events in Hong Kong: the SARS outbreak in Amoy Gardens and the COVID-19 outbreak in Luk Chuen House. Logistic regression results suggested that the predicted viral exposure was positively correlated with the probability of disease infection at apartment level for both events. Infection risks associated with the outdoor route transmission of SARS can be reduced to <10%, if the quanta emission rate from the primary patient is below 30 q/h. Compared with the indoor route transmission, the outdoor route can better explain patterns of disease infection. A viral plume can spread upward and downward, driven by buoyancy forces, while also dispersing under natural wind. Fan-assistant natural ventilation in residential buildings may increase infection risks. Findings have implication for public health response to current and future pandemics and the ATOR model can serve as planning and design tool to identify the risk of airborne disease transmission in high-density cities.
15 citations
TL;DR: In this paper, MgO-FeO3-SiO2 fayalitic slag (FS) was used as the sole solid precursor (as an aggregate and binder) in alkali-activated mortars.
Abstract: Vast amounts of water-cooled non-ferrous slags are generated yearly, and significant amounts are unutilized or dumped in landfills. To address this issue, in this study, MgO-FeOx-SiO2 fayalitic slag (FS) was used as the sole solid precursor (as an aggregate and binder) in alkali-activated mortars. The performance of the mortar samples was analyzed in terms of workability, density, compressive strength, and ultrasonic pulse velocity. The microstructural properties and binder composition of the samples were studied using a scanning electron microscope (SEM) coupled with energy dispersive X-ray spectroscopy (EDS). Experimental results revealed that mortar samples made with FS aggregates performed better, achieving a 28-day compressive strength of 21 MPa compared to mortars produced with standard sand aggregates, which gained compressive strengths of 9 MPa. Further optimization of the particle size distribution of FS aggregate-based mortar samples using particle packing technology improved the workability, densified the mortar and yielded a mechanical performance of up to 40 MPa. FS aggregates have better interfacial bonding with the binder gel compared to standard sand, and the FS aggregates participate in the hardening reactions, consequently affecting the final binder phase composition, which consists of a Na2O-Fe2O3-SiO2 gel with lower quantities of CaO, MgO and Al2O3. Therefore, the alkali-activated mortars produced based on the optimization of fully recycled industrial residues can provide a pathway for the sole utilization of metallurgical by-products, which can have a wide range of structural applications.
15 citations
TL;DR: In this article, the authors proposed a crowdsensing-oriented vibration acquisition and identification method based on time-frequency characteristics and deep transfer learning, which can distinguish the responses during an earthquake event from vibration under serviceability conditions.
Abstract: The cost of dedicated sensors has hampered the collection of the high-quality seismic response data required for real-time health monitoring and damage assessment. The emergence of crowdsensing technology, where a large number of mobile devices collectively share data and extract information of common interest, may help remove such obstacles and mitigate the seismic hazard. The present study proposes a crowdsensing-oriented vibration acquisition and identification method based on time–frequency characteristics and deep transfer learning. It can distinguish the responses during an earthquake event from vibration under serviceability conditions. The core classification process is performed using a combination of wavelet transforms and deep transfer networks. The latter were pre-trained using finite element models calibrated with the monitored seismic responses of the structures. The validation study confirmed the superior identification accuracy of the proposed method.
14 citations
TL;DR: A review of UHPFRC applications in the country is proposed in this article, where 10 bridge case studies are presented, including five strengthening of existing structures and five new designs.
Abstract: Ultra-High-Performance Fibre Reinforced Cementitious Composite (UHPFRC) provides solutions to enhance existing structures and design innovative new structures. Structural UHPFRC offers 3-5 times higher compressive and tensile strengths than ordinary concrete. Due to its strain-hardening behavior and dense matrix, structures made of UHPFRC remain crack-free and waterproof, guaranteeing durability. UHPFRC has been used particularly in Switzerland with more than 280 applications since 2003. A review of UHPFRC applications in the country is proposed in this paper. Ten bridge case studies are presented, including five strengthening of existing structures and five new designs. These structures were chosen to assess the multiple benefits that UHPFRC provides compared to traditional reinforced-concrete structures. Besides structural efficiency, several construction criteria are considered, such as construction costs, material durability, environmental impacts, and construction time. Structural rehabilitation made with UHPFRC leads to cost-effective interventions, and this material also helps to preserve heritage structures. Due to its specific mechanical properties, UHPFRC enables new structures with distinctive aesthetic designs with reduced construction time. The crucial contribution of research to the first case studies is also highlighted. This link between Swiss universities and the construction industry has quickly transitioned UHPFRC Technology from academic studies to real-world applications. Nowadays, the UHPFRC Technology is maturing and applications are common in the country.
14 citations
TL;DR: In this paper, a qualitative analysis of the COVID-19 complaints data gathered by OSHA from construction jobsites is presented, which provides insights into the safety and health trends on construction sites, lay the foundation for future work of academicians and practitioners to address the concerns faced by construction workers and serve as lessons learned for the industry in the case of any future pandemic.
Abstract: The coronavirus outbreak has created a global health crisis that has disrupted all industries, including the construction industry. Following the onset of the pandemic, construction workers faced and continue to face unprecedented safety and health challenges. Therefore, construction employers established new safety precautions to protect the health and safety of the workforce and minimize the spread of the virus. The new precautions followed the advice and guidelines offered by different health and safety agencies like the Occupational Safety and Health Administration (OSHA), Centers of Disease Control and Prevention (CDC), and the Associated General Contractors of America (AGC). With construction projects resuming operations, it becomes important to analyze the coronavirus-related health and safety concerns of construction workforce and understand how the new safety procedures can assist on jobsites. Existing studies mostly focused on interviews and surveys with construction companies to understand the impact on project performance and supply chains. However, no study has yet to analyze the U.S. construction workforce. This paper fills the gap by providing a qualitative descriptive analysis of the COVID-19 complaints data gathered by OSHA from construction jobsites. Information gathered by OSHA includes the jobsite location, the North American Industry Classification System (NAICS) of the construction company, the type of the complaint (i.e., formal or non-formal), and a thorough description of the complaint. N-grams were employed to analyze the complaints, detect trends, and compile a list of the most frequent concerns reported by the workforce. The analysis of the complaints data identifies safety practices that were most violated, highlights major safety and health concerns for construction workers, and pinpoints geographical areas that have seen a surge in complaints. The study also synthesized the existing research corpus and compiled a list of 100 best practices that construction employers can adopt to mitigate the concerns of the workforce. The findings of this study provide insights into the safety and health trends on construction sites, lay the foundation for future work of academicians and practitioners to address the concerns faced by construction workers, and serve as lessons learned for the industry in the case of any future pandemic.
13 citations
TL;DR: Walkability is a core urban design element due to being advantageous on to three fronts: health, livability, and sustainability as mentioned in this paper, however, there is no unified universal standardized walkability theory and there is a lack of emphasis on air quality and thermal stress in the design for walkability.
Abstract: Urban sprawl and increasing population density in urban centers create the challenge to finding ways of sustainable transportation solutions that preserve the convenience of residents while reducing emissions. Therefore, walkability is a core urban design element due being advantageous on to three fronts: health, livability, and sustainability. Adopting walkability as urban solution relieves conceptual and practical tensions between the individualistic interests manifested in the desire to own and use private cars, and the need to reduce transportation-based consumption This review advocates that long-term health benefits from walking and physical activity are the premier incentive to repurpose our cities to be more sustainable and more walking friendly, and spark behavioral change into reducing car dependency for all daily transportations. The review inspects physical elements of the built environment that make the walking trip feasible and desirable, such as connectivity, accessibility, and closeness of destination points, presence of greenness and parks, commercial retail, and proximity to transit hubs and stations. Hence, this review explores a few popular walkability evaluation indices and frameworks that employ subjective, objective and/or distinctive methods within variant environmental, cultural, and national context. There is a need for rigorous evaluation tools of walkability for policy makers and designers, yet there is no unified universal standardized walkability theory. Furthermore, there is a lack of emphasis on air quality and thermal stress in the design for walkability, despite the being a major factor in in taking the decision to walk and the possibility of nullifying any health benefits from walking. Research opportunities in the field of walkability can leverage location tracking from smart devices and identify the interaction pattens of pedestrians with other transportation modes, especially for those with fundamental movement challenges such as wheelchair users.
13 citations
TL;DR: In this paper, the performance of Recycled Ultra High Durability Concrete (R-UHDC) is evaluated using different fractions of recycled aggregate obtained from crushed UHDC, as a substitute of the natural aggregate.
Abstract: The purpose of the work reported in this paper is to assess the performance of Recycled Ultra High Durability Concrete (R-UHDC), produced using different fractions of recycled aggregate obtained from crushed Ultra High Durability Concrete (UHDC), as a substitute of the natural aggregate. Four different Recycled Ultra High Durability Concrete mixes (R-UHDC) were designed and manufactured with a reference mix based on natural aggregate and three mixes with the natural aggregate replaced using recycled UHDC according to two percentage replacement values (50% and 100%). The effect of environmental degradation of the recycled parent concrete was also addressed, using recycled aggregates subjected to accelerated carbonation (replacement percentage equal to 50%) The work has been conducted in the framework of the activities of the Horizon 2020 ReSHEALience Project in Ultra High Durability Concrete. One key objective of the project was to formulate the concept and experimentally validate the performance of Ultra High Durability Concrete for structures and infrastructures exposed to extremely aggressive scenarios. The ReSHEALience consortium has defined UHDC as a “strain-hardening (fibre reinforced) cementitious material with functionalizing micro- and nano-scale constituents especially added to deliver high durability in the cracked state under extremely aggressive exposure conditions”. In this context, the research was conducted to investigate the potential of recycling the produced and validated UHDCs, and employing them as a partial or even total replacement of natural sand in the production of a new UHDC. This supports the cradle-to-cradle approach in life cycle engineering applications. The research confirmed the effective regeneration of new UHDC based on recycled aggregate obtained from crushed UHDC, attaining the required rheological characteristics, mechanical properties (compressive, flexural strength and toughness) and durability performance (chloride penetration resistance, chloride migration, water capillary suction and resistivity). This work is intended as the first step towards the sustainability assessment of the end of life of UHDC materials and structures and the potential of recycled-UHDC for new and retrofitting structural applications.
12 citations
TL;DR: In this paper, an inductive framework using a Grounded Theory Methodology (GTM) was developed to highlight digital transformation in construction as a process where the implementation of digital technologies creates transformation effects which trigger strategic considerations for putting in place the enablers that facilitate transformation effects and for suppressing the barriers to it.
Abstract: There is increasing implementation of digital technologies in construction. However, the transformation effects encompassing digital technology implementation is yet to be fully comprehended within the context of construction. Therefore, this study was aimed to provide a holistic understanding of digital transformation in construction. The study drew on extant literature by studying 36 journal publications published between 2016 when digital transformation emerged in construction from the Information Systems (IS) field and 2020. This led to the development of an inductive framework using a Grounded Theory Methodology (GTM) to highlight digital transformation in construction as a process where the implementation of digital technologies creates transformation effects which trigger strategic considerations for putting in place the enablers that facilitate transformation effects and for suppressing the barriers to it. Building on the framework, this study described and presented the strategic considerations for facilitating specific enablers and those for suppressing specific barriers as digital transformation guideline in construction. This study demonstrated how the implementation of digital technologies has increased the understanding of and provided the basis for digital transformation in construction.
11 citations
TL;DR: In this paper, the authors investigated the main barriers faced by a large Brazilian construction company in their efforts to thoroughly implement BIM and found that BIM has improved the information management of the design itself and its interface with construction phase.
Abstract: Purpose: The research goal was to investigate the main barriers faced by a large Brazilian construction company in their efforts to thoroughly implement BIM. This study focused on the analysis of understanding the barriers to BIM adoption and the usage of 3D/4D dimensions on the development of an infrastructure project. Research methodology: The research methodology was exploratory and qualitative carried out through a single case study approach made upon bibliographical research, company document analysis, project document analysis, interviews, informal conversations, and observations. The research methodology was developed in six months (from June to December 2019) divided in three main phases: Phase 1: definition and design, Phase 2: preparation and collection, and Phase 3: data analysis and conclusion. Data collection was developed using a semi structured research protocol with two different semi structured questionnaires: The first questionnaire aimed at collecting data regarding to BIM implementation in the company’s organizational context. The second one focused on the understanding of BIM adoption in the project and on the investigation of the main barriers related to the usage of 3D and 4D modeling in the project studied. Findings: Regarding to BIM implementation in the company, despite the company studied is a construction company in the infrastructure sector, BIM was considered more efficiently in the design phase and flawed in the construction phase. Findings shown that BIM has improved the information management of the design itself and its interface with construction phase. In relation to the usage of BIM in the project, it was noticed a more collaborative work environment due to the effectiveness of communication between the design and construction teams in the job site. In respect to the usage of 3D/4D modeling in the project studied, the difficulties to extract information from the 3D model has disable the usage of 4D modeling during construction phase. Therefore, the difficulties reported were identified as an opportunity to map deficiencies in the BIM model in order to define parameters for the new projects proposals and to automate the process of receiving the model and checking for inconsistencies or lack of information.
TL;DR: In this paper, the authors estimated the GDP in a 1/12-degree grid scale for the period of 1850-2100 in 10-year intervals, through downscaling of historical GDP data for 1850−2010 and SSP future scenario data for 2010−2100.
Abstract: Historical and future spatially explicit population and gross domestic product (GDP) data are essential for the analysis of future climate risks. Unlike population projections that are generally available, GDP projections—particularly for scenarios compatible with shared socioeconomic pathways (SSPs)—are limited. Therefore, we estimated the GDP in a 1/12-degree grid scale for the period of 1850–2100 in 10-year intervals. The estimation is done through downscaling of historical GDP data for 1850–2010 and SSP future scenario data for 2010–2100. In the downscaling, we first modeled the spatial and economic interactions among cities and projected different future urban growth patterns according to the SSPs. Subsequently, the projected patterns and other auxiliary geographic data were used to estimate the gridded GDP distributions. Finally, the GDP projections were visualized via three-dimensional mapping to enhance the clarity for multiple stakeholders. Our results suggest that the spatial pattern of urban and peri-urban GDP depends considerably on the SSPs; e.g., the GDP of the existing major cities grew rapidly under SSP1, slowly grew under SSP3, and dispersed growth under SSP5.
TL;DR: In this article, the authors present a review of AR applications in civil infrastructure, focusing on research studies in the latest five years (2016-2020) and their milestone developments, and discuss the challenges of AR implementation and recommends future applications.
Abstract: The 4th industrial revolution started in 2016 and referred to a new phase in the Industrial Revolution. One of the most significant technological evolvement during the 4th industrial revolution is Augmented Reality (AR) technology. AR superimposes interactional virtual objects/images to real environments. Because of the interaction and see-through characteristics, AR is better applied to engineering than Virtual Reality (VR). The application of AR in civil infrastructure can avoid artificial mistakes, improve efficiency, and saves budget. This paper reviews AR applications in civil infrastructure, focusing on research studies in the latest five years (2016-2020) and their milestone developments. More than half of the AR research and implementation studies have focused on the last five years' construction domain. Researchers deploy AR technologies in onsite construction to assist in discrepancy checking, collaborative communication, and safety checking. AR also uses building information models (BIM) to produce detailed 3D structural information for visualization. Additionally, AR has been studied for structural health monitoring (SHM), routine and damage detection, energy performance assessment, crack inspection, excavation, and underground utility maintenance. Finally, AR has also been applied for architecture design, city plan, and disaster prediction as an essential part of smart city service. This paper discusses the challenges of AR implementation in civil infrastructure and recommends future applications.
TL;DR: Puglisi et al. as mentioned in this paper found that 55% of the workers perform their activity in an isolated room of the home environment, 43% in a shared room (e.g., kitchen, living room), and 2% in an outdoor space, with the majority of workers (57%) performing activity without other people in the environment.
Abstract: Noisiness in the working environment was largely proved to have effects on the working activity and performance. To limit the spreading of the COVID-19 pandemic in the first wave between March and May 2020, Italian workers had massively started performing remote working. Insights on the subjective perception of noise annoyance under the remote working settings were thus necessary. Workers from a university and from several large and small Italian companies, resulting in 1,934 participants overall, answered to a questionnaire on the perception of noise annoyance in the remote working environment. A total of 57% of the responding workers stated to be sensitive to noise. The questionnaire was delivered online;data were recorded anonymously and then aggregated for statistical analyses. Results show that 55% of the workers perform their activity in an isolated room of the home environment, 43% in a shared room (e.g., kitchen, living room), and 2% in an outdoor space, with the majority of workers (57%) performing activity without other people in the environment. Among the noise sources investigated, 25% of workers recognize the noise generated by people (e.g., talking, moving, calling, listening to music) as the main source of disturbance. The negative consequences of noise annoyance during the remote working hours are mainly related to a loss of concentration and to a difficulty in relaxing. Furthermore, workers reported to get easily irritated by noise generated from the neighborhoods or from the housemates as it tends to distract from finishing a task. © Copyright © 2021 Puglisi, Di Blasio, Shtrepi and Astolfi.
TL;DR: In this article, the authors present an approach which integrates Earth observation and climate data with three-dimensional urban models to determine optimal tree placement (per m2) within proposed urban developments to enable more effective localised UHI mitigation.
Abstract: Urban areas are expected to triple by 2030 in order to accommodate 60% of the global population. Anthropogenic landscape modifications expand coverage of impervious surfaces inducing the urban heat island effect; a critical 21st century challenge associated with increased economic expenditure, energy consumption and adverse health impacts. Yet omission of UHI measures from global climate models and metropolitan planning methodologies precludes effective sustainable development governance. We present an approach which integrates Earth observation and climate data with three-dimensional urban models to determine optimal tree placement (per m2) within proposed urban developments to enable more effective localised UHI mitigation. Such data-driven planning decisions will enhance the future sustainability of our cities to align with current global urban development agendas.
TL;DR: In this paper, the effect of size classification and milling treatments on the reactivity of a siliceous fly ash was compared using the R3 heat release test method and consumption of portlandite in blended cements.
Abstract: Upcycling and reclaiming of low quality or stored coal combustion fly ashes enables to tap into a voluminous resource of supplementary cementitious materials for low-carbon blended cements. Low reactivity fly ashes are usually either too crystalline or too coarse. Beneficiation treatments for coarse fly ashes comprise size classification or milling processes to extract or produce fine size fractions of higher pozzolanic reactivity. This paper compares the effect of size classification and milling treatments on the reactivity of a siliceous fly ash. The chemical reactivity is assessed using the R3 heat release test method and consumption of portlandite in blended cements. Both test results are used to calculate the degree of reaction of the fly ashes over time in blended cement. The results demonstrate a strong effect of particle size on fly ash reactivity and degree of reaction. It is shown that increasing the inherent reactivity of fly ashes is an effective way of both accelerating compressive strength gain and enhancing late age strength.
TL;DR: In this article, the authors implemented a mobile monitoring methodology to determine the spatiotemporal distribution of particulate matter (PM) and black carbon (BC) throughout Philadelphia, Pennsylvania and use hot spot analysis and heatmaps to determine times and locations where pollutant concentrations are highest.
Abstract: Urban air pollution poses a major threat to human health. Understanding where and when urban air pollutant concentrations peak is essential for effective air quality management and sustainable urban development. To this end, we implement a mobile monitoring methodology to determine the spatiotemporal distribution of particulate matter (PM) and black carbon (BC) throughout Philadelphia, Pennsylvania and use hot spot analysis and heatmaps to determine times and locations where pollutant concentrations are highest. Over the course of 12 days between June 27 and July 29, 2019, we measured air pollution concentrations continuously across two 150-mile (241.4 km) long routes. Average daily mean concentrations were 11.55 ± 5.34 µg/m3 (PM1), 13.48 ± 5.59 µg/m3 (PM2.5), 16.13 ± 5.80 µg/m3 (PM10), and 1.56 ± 0.39 µgC/m3 (BC). We find that finer PM size fractions (PM2.5) constitute approximately 84% of PM10 and that BC comprises 11.6% of observed PM2.5. Air pollution hotspots across three size fractions of PM (PM1, PM2.5, and PM10) and BC had similar distributions throughout Philadelphia, but were most prevalent in the North Delaware, River Wards, and North planning districts. A plurality of detected hotspots found throughout the data collection period (30.19%) occurred between the hours of 8:00 AM – 9:00 AM.
TL;DR: In this paper, the authors reveal differences between risk areas for spreading airborne contaminants in office buildings in northern Europe, including Denmark, Norway and Sweden, and the differences in the spread depends on different ventilation designs used in different countries.
Abstract: Most new office buildings in Nordic countries are equipped with balanced mechanical ventilation systems. The purpose of ventilation in office buildings is to provide thermal control by supplying cold or warm air for adequate indoor air quality. However, the role of ventilation in preventing virus transmission and maintaining a sufficient fresh air supply to obtain a low virus level through dilution is not currently well defined. Ventilation in office buildings is expected to contribute to preventing the spread of contaminants and provide comfort for occupants. The study reveals differences between risk areas for spreading airborne contaminants in office buildings in northern Europe, including Denmark, Norway and Sweden. The differences in the spread depends on different ventilation designs used in different countries.
TL;DR: In this article, the authors present a high-level overview of where the AEC industry is headed and establish eleven propositions for a resilient, post-COVID-19 future, for practitioners working in the design and construction industry.
Abstract: The coronavirus outbreak has challenged and continues to challenge every aspect of the supply chain within the AEC industry, forcing stakeholders to cope with increasing uncertainties and continuous change. The notion of resilience is especially salient now. While the need for the AEC industry to focus on resilience has been highlighted in recent articles, there is a need for a comprehensive discussion on what resilience means for the AEC industry and how companies can create built-in resilience. This paper takes the form of a high-level overview of where the industry is headed and aims to establish eleven propositions for a resilient, post-COVID-19 future, for practitioners working in the design and construction industry. Moreover, this paper proposes a ‘decentralization of workforce and integration of data’ model in which the established propositions are manifested to support a resilient AEC industry.
TL;DR: In this paper, the authors analyzed the transport of contaminants released by an infected person in a theater hall with an overhead air supply system and calculated the infection risks for occupants at various distances from the infected person.
Abstract: Severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) is spreading globally, and its high transmission speed and mortality rate are severely interfering with people's normal lives and the economy. Governments are now reopening their economies; however, the opening of theaters has been delayed, owing to their (often) crowded audiences and potentially higher infection risk. To determine whether it is safe to reopen theaters, in this study, the transport of contaminants released by an infected person in a theater hall with an overhead air supply system is analyzed numerically. The infection risks are calculated for occupants at various distances from the infected person in different directions and with/without wearing masks based on a revised Wells-Riley model, and under different supply air states and locations of the infected person. The results show that, first, the probabilities of infection in return air with filtration and all-fresh-air operations are decreased by 39.8% and 55.6%, respectively, as compared when the return air is not filtered. Second, the probabilities of infection for audiences sitting nine seats away from the infected person on the right, right-back, and back sides are 84.9%–92.3%, 37.3%–74.0%, and 36.3%–72.0% lower, respectively, than those for audiences sitting one-seat away from the infected person. In addition, sitting in separate rows can reduce the maximum probability by 7.4%-68.3%. Third, the probability of infection can be reduced by 93.7% after all the audiences wear masks with efficiencies of 75%. Fourth, the probability of infection can be controlled under a relatively safe range even though the quanta emission rate is 30 or 50 quanta/h, and even with two infected people in unfavorable seats. Thus, theaters can be safely reopened under return air filtration or all fresh air operations, and when audiences are sitting in separate seats and wearing masks.
TL;DR: In this article, the authors proposed and developed a new image encoding technique based on Time-series Segmentation (TS) to transform acceleration (A), velocity (V), and displacement (D) ground motion records into a three-channel AVD image with a pre-defined size of width × height.
Abstract: Traditional methods for seismic damage evaluation require manual extractions of intensity measures (IMs) to properly represent the record-to-record variation of ground motions. Contemporary methods such as Convolutional Neural Networks (CNNs) for time series classification and seismic damage evaluation face a challenge in training due to a huge task of ground-motion image encoding. Presently, no consensus has been reached on the understanding of the most suitable encoding technique and image size (width × height × channel) for CNN-based seismic damage evaluation. In this study, we propose and develop a new image encoding technique based on Time-series Segmentation (TS) to transform acceleration (A), velocity (V), and displacement (D) ground motion records into a three-channel AVD image of the ground motion event with a pre-defined size of width × height. The proposed TS technique is compared with two time-series image encoding techniques, namely Recurrence Plot (RP) and Wavelet Transform (WT). The CNN trained through the TS technique is also compared with the IM-based machine learning approach. The CNN-based feature extraction has comparable classification performance to the IM-based approach. WT 1000×100 results in the highest 79.5% accuracy in classification while TS 100×100 with a classification accuracy of 76.8% is most computationally efficient. Both the WT 1000×100 and TS 100×100 three-channel AVD image encoding methods are promising for future studies of CNN-based seismic damage evaluation.
TL;DR: In this paper, a large-scale crowdsourced data were collected from online ridesharing forums (i e, Uber Drivers) since the emergence of the novel coronavirus (COVID-19) pandemic, and different natural language processing and text-mining techniques were used to preprocess the data and classify risk perception, risk-taking, or risk-averting behaviors associated with rides-sharing during a major disease outbreak.
Abstract: The outbreak and emergence of the novel coronavirus (COVID-19) pandemic affected every aspect of human activity, especially the transportation sector Many cities adopted unprecedented lockdown strategies that resulted in significant nonessential mobility restrictions;hence, transportation network companies (TNCs) have experienced major shifts in their operation Millions of people alone in the USA have filed for unemployment in the early stage of the COVID-19 outbreak, many belonging to self-employed groups such as Uber/Lyft drivers Due to unprecedented scenarios, both drivers and passengers experienced overwhelming challenges that might elongate the recovery process The goal of this study is to understand the risk, response, and challenges associated with ridesharing (TNCs, drivers, and passengers) during the COVID-19 pandemic situation As such, large-scale crowdsourced data were collected from online ridesharing forums (i e , Uber Drivers) since the emergence of COVID-19 (January 25–May 10, 2020) Word bigrams, word frequency heatmaps, and topic models are among the different natural language processing and text-mining techniques used to preprocess the data and classify risk perception, risk-taking, or risk-averting behaviors associated with ridesharing during a major disease outbreak Results indicate higher levels of concern about economic disruption, availability of stimulus checks, new employment opportunities, hospitalization, pandemic, personal hygiene, and staying at home In addition, unprecedented challenges due to unemployment and the risk and uncertainties in the required personal protective actions against spreading the disease due to sharing are among the major interactions The proposed text-based data analytics of the ridesharing risk communication dynamics during this pandemic will help to identify unobserved factors inadvertently affecting the TNCs as well as the users (drivers and passengers) and identify more efficient strategies and alternatives for the forthcoming “new normal” of the current pandemic and the ones in the future The study will also guide us toward understanding how efficiently online social interaction outlets can be designed and implemented more effectively during a major crisis and how to leverage such platforms for providing guidelines during emergencies to minimize transmission of disease due to shared travel © Copyright © 2021 Mojumder, Ahmed and Sadri
TL;DR: In this paper, a causal loop diagram (CLD) was used to assess critical failure factors negating the micro-transfer of knowledge and technologies from smart campuses to smart cities in developing countries.
Abstract: The contribution of smart campuses to smart cities’ development and vice versa has been elucidated in extant literature. The micro-transfer of smart technologies and probable procurement and contracting models remain critical for such contributions to take place. This study used a systems thinking approach to establish the interrelationships existing between smart campus technologies which can be scaled towards the development of smart cities and assess the critical failure factors negating the micro-transfer of these technologies to smart city development initiatives in developing countries. To achieve its objective, the study adopted a phenomenological research design wherein qualitative data was elicited from a purposively selected sample of seven interviewees in South African Universities. The next phase of the analysis involved a thematic approach for the production of a causal loop diagram (CLD) reflecting the interrelationships between the abovementioned facets and the associated impact on the transference of knowledge and technologies from smart campuses to smart cities. This CLD was subsequently validated by a cohort of five experts. Findings from the validation phase were incorporated in an improved CLD which provided different archetypes for engendering successful transference. This study holds salient implications for universities, cities and other stakeholders seeking to engage in a quadruple helix innovative arrangement for smart campus/city development. This study concluded that smart campuses could act as living labs for future smartness of cities globally. Government funding and willingness to produce smart cities from campuses is a fundamental feature of creating smart infrastructure in cities.
TL;DR: A generalized lambda surrogate model recently developed by some of the authors is proposed to surrogate the hybrid model response, and Sobol' sensitivity indices are computed for substructure quantity of interest response quantiles.
Abstract: Hybrid simulation is an experimental method used to investigate the dynamic response of a reference prototype structure by decomposing it to physically-tested and numerically-simulated substructures. The latter substructures interact with each other in a real-time feedback loop and their coupling forms the hybrid model. In this study, we extend our previous work on metamodel-based sensitivity analysis of deterministic hybrid models to the practically more relevant case of stochastic hybrid models. The aim is to cover a more realistic situation where the physical substructure response is not deterministic, as nominally identical specimens are, in practice, never actually identical. A generalized lambda surrogate model recently developed by some of the authors is proposed to surrogate the hybrid model response, and Sobol' sensitivity indices are computed for substructure quantity of interest response quantiles. Normally, several repetitions of every single sample of the inputs parameters would be required to replicate the response of a stochastic hybrid model. In this regard, a great advantage of the proposed framework is that the generalized lambda surrogate model does not require repeated evaluations of the same sample. The effectiveness of the proposed hybrid simulation global sensitivity analysis framework is demonstrated using an experiment.
TL;DR: In this paper, the authors investigated the influence of different subgrade types on the track behavior and evaluated the effectiveness of using geogrids, wedge-shaped engineered backfill and zone with reduced sleeper spacing in improving the performance of critical zone.
Abstract: The critical zones are the discontinuities along a railway line that are highly susceptible to differential settlement, due to an abrupt variation in the support conditions over a short span. Consequently, these zones require frequent maintenance to ensure adequate levels of passenger safety and comfort. A proper understanding of the behavior of railway tracks at critical zones is imperative to enhance their performance and reduce the frequency of costly maintenance operations. This paper investigates the dynamic behavior of the critical zone along a bridge-open track transition under moving train loads using two-dimensional finite element approach. The influence of different subgrade types on the track behavior is studied. The effectiveness of using geogrids, wedge-shaped engineered backfill and zone with reduced sleeper spacing in improving the performance of the critical zone is evaluated. The numerical model is successfully validated against the field data reported in the literature. The results indicate that the subgrade soil significantly influences the track response on the softer side of the critical zone. The difference in vertical displacement between the stiffer and the softer side of a track transition decreases significantly with an increase in the strength and stiffness of the subgrade soil. The subgrade layer also influences the contribution of the granular layers (ballast and subballast) to the overall track response. As the subgrade becomes stiffer and stronger, the contribution of the granular layers to the overall track displacement increases. The mitigation techniques that improve the stiffness or strength of granular layers may prove more effective for critical zones with stiff subgrade than critical zones with soft subgrade. Among all the mitigation techniques investigated, the wedge-shaped engineered backfill significantly improved the performance of the critical zone by gradually increasing the track stiffness.
TL;DR: In this article, the authors present a mini-review study of active botanical bio-filtration (ABB) systems and indoor air quality in real-world environments, where the air is circulated through the plant root zone as well as the growing medium for maximum phytoremediation effect.
Abstract: The implementation of sustainable solutions for maintaining indoor air quality has become a particular concern to the building community. Research on green technologies for indoor air has highlighted the potential of active botanical biofiltration (ABB) systems, where the air is circulated through the plant root zone as well as the growing medium for maximum phytoremediation effect. ABB has been found beneficial for pollutant removal along with the potential for increasing humidity and air cooling. Assessment in laboratory condition revealed the removal efficiency of ABB systems ranged from 54% to 85% for total suspended particulate matters where gaseous pollutants such as formaldehyde and toluene removal efficiencies were 90% and over 33%, respectively, in a real environment. Moreover, the aesthetic value of ABB acts as an added benefit for positive mental effects. However, very limited data is available to date that demonstrates the pollutant removal efficiency of ABB systems in realistic indoor environments, and the mechanisms behind this emerging technology are still poorly understood. The purpose of this mini-review study is to present a quantitative assessment of the recent advancement of ABB systems and indoor air quality. Finally, the limitations of ABB systems and research gaps are highlighted for future improvement.
TL;DR: In this article, the authors analyzed the impacts of COVID-19 on the U.S. air transportation network between March and August 2020 and found that despite dramatic reductions in flight and passenger volumes, the network remained robust and resilient against perturbation.
Abstract: This paper analyzes the impacts of COVID-19 on the U.S. air transportation network between March and August 2020. Despite dramatic reductions in flight and passenger volumes, the network remained robust and resilient against perturbation. While 24% percent of airports closed, the reduction in network efficiency was only 5.1%, which meant airlines continued to serve most destinations. A deeper analysis of airport closures reveals that 1) small peripheral airports were the most likely to be closed; 2) the Coronavirus Aid, Relief, and Economic Security (CARES) Act was a statistically important predictor of closure; 3) socio-economic and epidemiological factors characterizing the airport’s region such as income, income inequality, political leaning, and the number of observed COVID cases were not predictive of airport closure. Finally, we show that high network robustness has a downside; although emissions by the U.S. air traffic in 2020 fell by 37.4% compared to 2019, mostly due to the drop in the number of flights, emissions per passenger doubled in the period April-August 2020, and increased eightfold in the week of April 5-11, which points to inefficient use of resources.
TL;DR: In this paper, a 3D finite element (3D FEM) approach is presented to simulate the long-term behavior of railway tracks at transition zones, considering both plastic deformation of the ballast layer using a high-cycle strain accumulation model and the nonlinearity of the dynamic vehicle-track interaction that results from the evolution of the deformed states of the track itself.
Abstract: Transition zones between embankments and bridges or tunnels are examples of critical assets of the railway infrastructure. These locations often exhibit higher degradations rates, mostly due to the development of differential settlements, which amplify the dynamic train-track interaction, thus further accelerating the development of settlements and deteriorating track components and vehicles. Despite the technical and scientific interest in predicting the long-term behavior of transition zones, few studies have been able to develop a robust approach that could accurately simulate this complex structural response. To address this topic, this work presents a three-dimensional finite element (3D FEM) approach to simulate the long-term behavior of railway tracks at transition zones. The approach considers both plastic deformation of the ballast layer using a high-cycle strain accumulation model and the non-linearity of the dynamic vehicle-track interaction that results from the evolution of the deformed states of the track itself. The results shed some light into the behavior of transition zones and evidence the complex long-term response of this structures and its interdependency with the transient response of the train-track interaction. Aspects that are critical when assessing the performance of these systems are analyzed in detail, which might be of relevance for researchers and practitioners in the design, construction, and maintenance processes.
TL;DR: In this article, a selection of these interventions is presented, which analyzes the effectiveness of various retrofitting solutions, with a specific attention to the force transfer mechanisms between existing structures and strengthening systems.
Abstract: In 2012, the North of Italy was hit by a seismic sequence charactyerized by two main events occurred on May 20 and 29 with MW = 6.1 and 6.0, respectively. Those earthquakes were particularly severe towards precast Reinforced Concrete (RC) structures not designed for seismic resistance. In the past years, the authors implemented a database collecting damage data and typological information on the industrial buildings struck by the Emilia earthquakes. That database was used to develop empirical fragility curves, which highlighted the considerable vulnerability of precast buildings conceived in accordance with pre-seismic code provisions. More recently, the interventions of seismic retrofitting on the same buildings, funded by the Emilia-Romagna region and designed by engineers which were directly hired by the companies, were examined in detail and critically revisited. A selection of these interventions is presented in this paper, which analyzes the effectiveness of the various retrofitting solutions, with a specific attention to the force transfer mechanisms between existing structures and strengthening systems. The interventions are divided between column strengthening (based, for example, on RC or steel jacketing) and interventions aimed at providing the building with a suitable earthquake resistant system (based, for example, on either the use of the existing cladding panels or the implementation of new bracing systems). Graphical representations of the analyzed solutions with the relevant construction details are provided.