Repair of Second-Generation Recycled Fine Aggregate of Waste Concrete from Freeze-Thaw Environment by Carbonation Treatment

The reuse of waste recycled concrete from harsh environments has become a research hotspot in the field of construction.This study investigated the repair effect of carbonation treatment on second-generation recycled fine aggregate(SRFA)obtained from recycled fine aggregate concrete(RFAC)subjected to freeze-thaw(FT)cycles.Before and after carbonation,the properties of SRFA were evaluated.Carbonated second-generation recycled fine aggregate(CSRFA)at five substitution rates(0%,25%,50%,75%,100%)to replace SRFA was used to prepare carbonated second-generation recycled fine aggregate concrete(CSRFAC).The water absorption,porosity and mechanical properties of CSRFAC were tested,and its frost-resisting durability was evaluated.The results showed after carbonation treatment,the physical properties of SRFA was improved and met the requirements of II aggregate.The micro-hardness of the interfacial transition zone and attached mortar in CSRFA was 50.5%and 31.2%higher than that in SRFA,respectively.With the increase of CSRFA replacement rate,the water absorption and porosity of CSRFAC gradually decreased,and the mechanical properties and frost resistance of CSRFAC were gradually improved.Carbonation treatment effectively repairs the damage of SRFA caused by FT cycles and improves its application potential.

DIFFUSION OF INNOVATION IN SUSTAINABLE BUILDING PRACTICES AND THE ROLE OF STAKEHOLDERS

The stakeholder network in a building project can influence the process of adopting sustainable building practice.Complexity of construction projects calls for integrated modes of collaboration,while the excess inertia among stakeholders resulted in sluggish adoption of sustainable design and technologies.This study examined buildings that both had and had not adopted Leadership in Energy and Environmental Design and/or ENERGY STAR in the New York metropolitan area,built,or went through major renovation between 1998 and 2013.Secondary datasets from multiple sources,including a private building database company,US Green Building Council,and the US Environmental Protection Agency,were combined based on building address and used for analysis.Stakeholders involved in those projects were retrospectively identified to understand the diffusion of innovation.The analysis included a total of 205 projects and 273 organizations.Findings suggest that having an architect who had worked on ENERGY STAR project(s)increased the likelihood of adopting ENERGY STAR.However,stakeholders’previous work collaboration was not associated with the adoption of sustainable programs.The method of utilizing multiple secondary datasets was tested to contribute to the methodology of building research by enabling the accumulation of knowledge.

Quasi-plane-hypothesis of strain coordination for RC beams seismically strengthened with externally-bonded or near-surface mounted fiber reinforced plastic

The application of fiber reinforced plastic（FRP）,including carbon FRP and glass FRP,for structural repair and strengthening has grown due to their numerous advantages over conventional materials such as externally bonded reinforcement（EBR） and near-surface mounted（NSM） strengthening techniques.This paper summarizes the results from 21 reinforced concrete beams strengthened with different methods,including externally-bonded and near-surface mounted FRP,to study the strain coordination of the FRP and steel rebar of the RC beam.Since there is relative slipping between the RC beam and the FRP,the strain of the FRP and steel rebar of the RC beam satisfy the quasi-plane-hypothesis;that is,the strain of the longitudinal fiber that parallels the neutral axis of the plated beam within the scope of the effective height（h 0） of the cross section is in direct proportion to the distance from the fiber to the neutral axis.The strain of the FRP and steel rebar satisfies the equation：ε FRP =βε steel,and the value of β is equal to 1.1-1.3 according to the test results.

Study on Vector Magnetic Properties of Magnetic Materials Using Hybrid Hysteresis Model

This paper presents a method to study the vector magnetic properties of magnetic materials under alternating and rotational magnetic field using 2-D vector hybrid hysteresis model.Combining Preisach model and Stoner-Wohlfarth(S-W)model,the vector hybrid hysteresis model is established for magnetic materials.The alternating and rotational hysteresis properties are calculated under different excitation frequency,respectively.And the computed results are compared with the experimental measurement ones.It is shown that the vector model can simulate the alternating and rotational magnetic properties effectively under low magnetization fields and low excitation frequency.

Experimental Study on Measurement of Carbonation Depth of Concrete

Based on the test results, the differences of the carbonized depth of concrete measured by phenolphthalein indicator and rainbow indicator were discussed, the effects of the water to cement ratio of concrete, the carbonized age and the relative humidity of environment on the carbonized depth of concrete and the depth of half-carbonized zone corresponding to green zone measured by rainbow indicator were also analyzed. It is proved that the depth measured by phenolphthalein indicator is always smaller than that measured by rainbow indicator, and the half-carbonized zone can only be measured by rainbow indicator. The carbonized and half-carbonized depths of concrete are influenced by the carbonation age, the water to cement ratio of concrete and the relative humidity of environment. It is suggested that the phenolphthalein indicator can be used to measure the carbonized depth of concrete when the strength grade of concrete is below C45, otherwise, the rainbow indicator should be utilized.

Probabilistic Response and Short-Term Extreme Load Estimation of Offshore Monopile Wind Turbine Towers by Probability Density Evolution Method

A new analysis framework based on probability density evolution method(PDEM)and its Chebyshev collocation solution are introduced to predict the dynamic response and short-term extreme load of offshore wind turbine(OWT)towers subjected to random sea state.With regard to the stochastic responses,random function method is employed to generate samples of sea elevation,the probability density evolution equation(PDEE)is solved to calculate time-variant probability density functions of structural responses.For the probabilistic load estimation,a FAST model of NREL 5MW offshore turbine is established to obtain samples of bending moment at the tower base.The equivalent extreme event theory is used to construct a virtual stochastic process(VSP)to assess the short-term extreme load.The results indicate that the proposed approach can predict time-variant probability density functions of the structural responses,and shows good agreement with Monte Carlo simulations.Additionally,the predicted short-term extreme load can capture the fluctuation at the tail of the extreme value distribution,thus is more rational than results from the typical distribution models.Overall,the proposed method shows good adaptation,precision and efficiency for the dynamic response analysis and load estimation of OWT towers.

A Numerical Study on the Extinguishing Performances of High-Pressure Water Mist on Power-Transformer Fires for Different Flow Rates and Particle Velocities

In order to study the extinguishing performance of high-pressure-water-mist-based systems on the fires originating from power transformers the PyroSim software is used.Different particle velocities and flow rates are considered.The evolution laws of temperature around transformer,flue gas concentration and upper layer temperature of flue gas are analyzed under different boundary conditions.It is shown that the higher the particle velocity is,the lower the smoke concentration is,the better the cooling effect on the upper layer temperature of flue gas layer is,the larger the flow rate is and the better the cooling effect is.

Analysis on distribution law of the abutment pressure of the integrated coal beside the road-in packing for gob-side entry retaining in fully-mechanized caving face

The three-dimensional damage constitutive relationship of coal is established and distribution law of the abutment pressure of the integrated coal beside the road-in packing for gob-side entry retaining in fully-mechanized caving face under the effect of given deformation of the main roof is analyzed by the damage mechanics theory. And the relationship between distribution of the abutment pressure and thickness of coal seam is explored. The presented result is of great theoretical significance and practical value to the study on stability control of the surrounding rock of road-in packing for gob-side entry retaining in fully-mechanized caving face.

Use of Innovative Contracting Methods by Dots - Project Managers Speak

Alternative contracting techniques have been frequently used in highway construction in the United State and have played an important role in the effort to improve construction project performance. However, it is still unknown whether which project factors have significant influence on project performance. It is essential to learn from the experiences and opinions of construction project managers who had executed innovative or alternative contracts in order to improve and refine the usage of alternative contracting methods. Innovative contracting methods have been used by state Departments of Transportation for many years, so there is now sufficient data to measure the effectiveness of these innovations. Working under a grant from the Florida Department of Transportation （FDOT）, the research team used the experiences and opinions of construction field engineers who had executed innovative contracts on FDOT projects to measure the effectiveness of these systems. To that end, interviews were conducted with FDOT and consultant personnel from across Florida. All interviewed were project managers who had overseen at least one project using an innovative contracting method. Discussions brought enthusiastic responses from those interviewed, both for and against certain innovations. This paper will focus on the experiences and opinions of those experienced construction field engineers dealing with well-known innovations, as well as newer innovations such as ＂Detour Rental＂ and ＂Damage Recovery＂.

DECISION-MAKING FRAMEWORK FOR SELECTION AND DESIGN OF SHADING DEVICES BASED ON DAYLIGHTING

This research looked to improve the daylighting performance of a shading device as a window component.The paper describes the development of the decision-making framework(DMF)for the selection and design of shading devices based on daylighting.The DMF presents the process of analysis of the shading devices’daylighting performance in the selection of existing shading devices and in the design of new shading devices.The research determined the shading device daylighting performance measures(such as illuminance and daylight autonomy)as well as the variables that influence daylight performance.Interactions among the variables and the effects of these interactions on the shading device daylighting performance were explained and quantified in the DMF.The DMF also included ways of present-ing the results of testing the shading devices and the process of making the decision.A case study for three blind systems was performed to determine if the DMF provides a concept for the analysis of the daylighting performance of shading devices and for making decisions about the design/selection of the shading device.Computer simulation was used to calculate the illuminance levels and the daylight autonomies(DAs)as a result of the application of these blinds.The values of the DAs are compared for three blind systems to select the most appropriate sys-tem to be applied on a proposed building.The DMF based on daylighting can help building designers to select the most suitable shading device based on its daylighting performance,and can help shading device manufacturers in designing new shading devices with improved daylighting performance.FIGURE 2.Simplified DMF diagram.

FINDING EVIDENCE OF GREEN LEASING IN UNITED STATES GOVERNMENT-LEASED PROPERTIES

Although the term“green leasing”is not yet well defined,its primary purpose is clear.With an aim to create a collaborative environment through legal provisions between a building owner and a tenant,green leasing may ultimately help resolve the energy paradox in tenanted properties.Issues surrounding split-incentives are driven by a mismatch between owners’capital expenditures on improving building energy efficiency and an uncertainty of tenant or occupant behavior that might affect a building’s energy consumption.Though some countries have started to develop guidelines promoting the adoption of green leasing,especially in government buildings and commercial real estate,implementation has not been overly successful globally.This study has two focuses,the first of which is to compare green leasing guidelines from various countries and to suggest six comprehensive categories of green leasing components:management relationships,information sharing,certificates,legal stipulations,financial factors,and operation.The second core area of research places government-tenanted properties’lease agreement contracts.The goal is to find any evidence in a legal condition between a building owner and a tenant,in this case federal government,to improve building energy efficiency with less environmental impact in the United States.The findings of the study indicated 41 out of 400 leases had green clauses.Three out of six categories proposed in this study were found in the U.S.government-tenanted properties,while the other three types were not shown.The findings of this study also suggest categories of green leasing clauses can contribute to defining green leasing and provide empirical evidence of green leasing in government-tenanted properties.Ultimately,this study produces arguments for possible reasoning behind the employment of some green lease categories but the lack of use of others,specifically in the U.S.office market and government-tenanted buildings.

Degree of Integrated Water Resources Management Implementation in Context of Climate Change in a Watershed:Case of Oueme Basin,Benin(West Africa)

This study is based on the hypothesis that the implementation of Integrated Water Resources Management(IWRM)tools in the Oueme watershed has not led to a systematic improvement in the degree of IWRM implementation in the Oueme Valley in Benin.Methodologically,data were collected through a semi-structured survey of stakeholder families in the study area using snowball sampling.The tool used was the form developed by the United Nations to collect data to assess the level of IWRM implementation.The four(4)assessment criteria,each covering a key component of IWRM,are the enabling environment,institutions and participation,management tools and financing.The results obtained per criteria according to the stepwise methodology adopted reveal on average a degree of implementation of 40 on a scale of 0 to 100 in the Oueme basin.This value varies according to the geographical area and the factors considered.This study,which is a decision-making tool,provides a guide for governments to monitor the progress of integrated water resources management in their territory.

ANALYSIS OF THE DESIGN PROCESS OF GREEN CHILDREN’S HOSPITALS:Focus on Process Modeling and Lessons Learned

Healthcare facilities are among the most complicated facilities to plan,design,construct and operate.A new breed of hospitals is considering the impact of the built environment on healthcare worker productivity and patient recovery in their design,construction,and operation.A crucial subset of healthcare facilities are children’s hospitals where the consequences of poor building system design and performance have the potential to seriously impact young lives with compromised health.Green facilities are not always pursued:they are perceived as difficult to build and costing more than equivalent conventional hospitals.This study explored the design process of the Children’s Hospital of Pittsburgh of the University of Pittsburgh Medical Center(UPMC)and Penn State’s Hershey Medical Center Children’s Hospital to understand the critical steps and processes for green children’s hospital design.Producing a series of process maps that identify the key characteristics in the complex design requirements of a green children’s hospital,this paper reveals the importance of design process to design quality.More broadly,this research will help future project teams meet the complex design requirements of green children’s hospitals.

An Approach for Human Posture Recognition Based on the Fusion PSE-CNN-BiGRU Model

This study proposes a pose estimation-convolutional neural network-bidirectional gated recurrent unit(PSECNN-BiGRU)fusion model for human posture recognition to address low accuracy issues in abnormal posture recognition due to the loss of some feature information and the deterioration of comprehensive performance in model detection in complex home environments.Firstly,the deep convolutional network is integrated with the Mediapipe framework to extract high-precision,multi-dimensional information from the key points of the human skeleton,thereby obtaining a human posture feature set.Thereafter,a double-layer BiGRU algorithm is utilized to extract multi-layer,bidirectional temporal features from the human posture feature set,and a CNN network with an exponential linear unit(ELU)activation function is adopted to perform deep convolution of the feature map to extract the spatial feature of the human posture.Furthermore,a squeeze and excitation networks(SENet)module is introduced to adaptively learn the importance weights of each channel,enhancing the network’s focus on important features.Finally,comparative experiments are performed on available datasets,including the public human activity recognition using smartphone dataset(UCIHAR),the public human activity recognition 70 plus dataset(HAR70PLUS),and the independently developed home abnormal behavior recognition dataset(HABRD)created by the authors’team.The results show that the average accuracy of the proposed PSE-CNN-BiGRU fusion model for human posture recognition is 99.56%,89.42%,and 98.90%,respectively,which are 5.24%,5.83%,and 3.19%higher than the average accuracy of the five models proposed in the comparative literature,including CNN,GRU,and others.The F1-score for abnormal posture recognition reaches 98.84%(heartache),97.18%(fall),99.6%(bellyache),and 98.27%(climbing)on the self-builtHABRDdataset,thus verifying the effectiveness,generalization,and robustness of the proposed model in enhancing human posture recognition.

Energy consumption simulations of rural residential buildings considering differences in energy use behavior among family members

The“average occupant”methodology is widely used in energy consumption simulations of residential buildings;however,it fails to consider the differences in energy use behavior among family members.Based on a field survey on the Central Shaanxi Plain,to identify the energy use behavior patterns of typical families,a stochastic energy use behavior model considering differences in energy use behavior among family members was proposed,to improve the accuracy of energy consumption simulations of residential buildings.The results indicated that the surveyed rural families could be classified into the following four types depending on specific energy use behavior patterns:families of one elderly couple,families of one middle-aged couple,families of one elderly couple and one child,and families of one couple and one child.Moreover,on typical summer days,the results of daily building energy consumption simulation obtained by the“average occupant”methodology were 25.39%and 28%lower than the simulation results obtained by the model proposed in this study for families of one elderly couple and families of one middle-aged couple,and 13.05%and 23.05%higher for families of one elderly couple and one child,and families of one couple and one child.On typical winter days,for the four types of families,the results of daily building energy consumption simulation obtained by the“average occupant”methodology were 21.69%,10.84%,1.21%,and 8.39%lower than the simulation results obtained by the model proposed in this study,respectively.

Optimal regulation of flexible loads in rural residential buildings considering mobile batteries:A case study in Shaanxi Province

While the grid-connected capacity of rural household photovoltaics is increasing rapidly,achieving dynamic supply-demand matching despite fluctuations in solar energy is challenging.With the rapid development of rural electrification,battery-powered technologies,such as electric vehicles and electric agricultural machinery,are becoming increasingly popular in rural areas.In this context,utilizing idle mobile batteries to assist in energy storage for rural residential buildings offers a new way to solve the problem of dynamic supply-demand matching.In this study,a field survey was conducted on several typical fruit-growing villages in the Central Shaanxi Plain in Shaanxi Province of China.Typical rural households were selected to calculate the electricity loads of the residential buildings,with due consideration to the intervention of mobile batteries.Under the premise of installing 3 kW household photovoltaic systems in rural households,an economical efficiency-oriented model was built for the optimal regulation of flexible loads.The results were compared in the context of two patterns of electricity consumption,i.e.,unidirectional charging of mobile batteries from buildings and bidirectional charging and discharging between mobile batteries and buildings.The bidirectional pattern significantly increased the photovoltaic consumption of typical rural households on various typical days.Specifically,during both scenarios of not implementing time-of-use and implementing time-of-use,the typical day of the winter slack farming season exhibited the best photovoltaic consumption effect among all types of typical days.Additionally,the bidirectional pattern also result in a significant increase in the annual electricity sales revenues for typical rural households.

Research on Evacuation Path Planning Based on Improved Sparrow Search Algorithm

Reducing casualties and property losses through effective evacuation route planning has been a key focus for researchers in recent years.As part of this effort,an enhanced sparrow search algorithm(MSSA)was proposed.Firstly,the Golden Sine algorithm and a nonlinear weight factor optimization strategy were added in the discoverer position update stage of the SSA algorithm.Secondly,the Cauchy-Gaussian perturbation was applied to the optimal position of the SSA algorithm to improve its ability to jump out of local optima.Finally,the local search mechanism based on the mountain climbing method was incorporated into the local search stage of the SSA algorithm,improving its local search ability.To evaluate the effectiveness of the proposed algorithm,the Whale Algorithm,Gray Wolf Algorithm,Improved Gray Wolf Algorithm,Sparrow Search Algorithm,and MSSA Algorithm were employed to solve various test functions.The accuracy and convergence speed of each algorithm were then compared and analyzed.The results indicate that the MSSA algorithm has superior solving ability and stability compared to other algorithms.To further validate the enhanced algorithm’s capabilities for path planning,evacuation experiments were conducted using different maps featuring various obstacle types.Additionally,a multi-exit evacuation scenario was constructed according to the actual building environment of a teaching building.Both the sparrow search algorithm and MSSA algorithm were employed in the simulation experiment for multiexit evacuation path planning.The findings demonstrate that the MSSA algorithm outperforms the comparison algorithm,showcasing its greater advantages and higher application potential.

Spatio-temporal distribution of gaseous pollutants from multiple sources in industrial buildings with different flow patterns

Energy consumption of industrial buildings has remained continuously high,and the environmental quality requirements are also constantly improving.Only by improving industrial environmental control technology based on the transport mechanism of the pollution,can the energy consumption of industrial building environmental control be further reduced,and the environmental quality of industrial buildings can be improved as well.Therefore,after verifying the numerical simulation by experiments,this study uses a self-label method to investigate the spatio-temporal distribution of gaseous pollutants from multiple time-series sources in industrial plants with different length-span ratios.The results show that,the polluted flow in plants with different aspect ratios have different flow patterns:(i)the,,Back-mixingw flow pattern occurs when the ratio of ventilation rate 6 and polluted flow rate at the exhaust height b is less than 1,i.e.,G/L_(p)<1,and(ii)the"One-way"flow pattern occurs when G/L_(p)>1.For plants with the"Back-mixing"pattern,the following source pollutants enter a density stratified environment induced by the retained pre-source pollutants.The flow of following source pollutants released at the same intensity as the precursor source can reach the roof,while those with low velocity and density difference may be blocked during the ascending process.The maximum height zm of the flow of the following source is related to both the initial Froude number Fr_(o)of the following source and the unsteady vertical density gradient of the fluid in the indoor environment dpa/dz.For plants with the,,One-way,/pattern,the flow from the following source enters into an environment with approximately uniform density.Under the condition of positive buoyancy,design parameters of ventilation corresponding to the vicinity of G/L_(p)=1 may be the optimal solution for safety and energy conservation.

Adaptive Wall-Based Attachment Ventilation:A Comparative Study on Its Effectiveness in Airborne Infection Isolation Rooms with Negative Pressure

The transmission of coronavirus disease 2019(COVID-19)has presented challenges for the control of the indoor environment of isolation wards.Scientific air distribution design and operation management are crucial to ensure the environmental safety of medical staff.This paper proposes the application of adaptive wall-based attachment ventilation and evaluates this air supply mode based on contaminants dispersion,removal efficiency,thermal comfort,and operating expense.Adaptive wall-based attachment ventilation provides a direct supply of fresh air to the occupied zone.In comparison with a ceiling air supply or upper sidewall air supply,adaptive wall-based attachment ventilation results in a 15%–47%lower average concentration of contaminants,for a continual release of contaminants at the same air changes per hour(ACH;10 h^(-1)).The contaminant removal efficiency of complete mixing ventilation cannot exceed 1.For adaptive wall-based attachment ventilation,the contaminant removal efficiency is an exponential function of the ACH.Compared with the ceiling air supply mode or upper sidewall air supply mode,adaptive wall-based attachment ventilation achieves a similar thermal comfort level(predicted mean vote(PMV)of0.1–0.4;draught rate of 2.5%–6.7%)and a similar performance in removing contaminants,but has a lower ACH and uses less energy.

Can hypobaric hypoxia affect human thermal comfort?An experimental study in Tibet,China

Hypobaric hypoxia is the main environmental feature of the Tibetan plateau which would influence the efficiency of human metabolic heat production and the ability of thermal regulation.In order to understand the influence of the hypoxic environment on the plateau on the thermal comfort of short-term sojourners in Tibet,China,oxygen generators were used to create oxygen-enriched environments,and physiological and psychological reactions of subjects were compared under different oxygen partial pressures(p_(O_(2)))and air temperatures(t_(a)).The results showed that subjects’thermal sensation,thermal comfort and mean skin temperature decreased with a decrease in the oxygen partial pressure.When t_(a)=17℃,the influence of oxygen partial pressure was more pronounced,compared to p_(O_(2))=16.4 kPa,the thermal sensation of subjects under p_(O_(2))=13.7 kPa decreased by 33%.The rate of subjects feeling comfortable decreased by 25%,and the mean skin temperature decreased by 0.7℃.The hypoxic environment of the plateau exacerbates human discomfort.Therefore,it is necessary to fully understand the actual thermal requirements of sojourners in Tibet,China.The results of this study would have implications for a better understanding of thermal comfort characteristics in the hypoxia environment in plateau.