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The spatial resolution of seepage monitoring methods based on fiber Bragg grating (FBG) temperature sensing technology is limited by the distance between measurement points. Improving the spatial resolution for a given number of measurement points is a prerequisite for popularizing this technology in the seepage monitoring of rockfill dams. The purpose of this paper is to address this problem.

This paper proposes a mobile-distributed seepage monitoring method based on the FBG-hydrothermal cycling seepage monitoring system. In this method, the positions of the measurement points are changed by freely dragging the FBG sensing cluster within the inner tube of a dual-tube structure, consisting of an inner polytetrafluoroethylene tube and outer polyethylene of raised temperature resistance heating tube.

A seepage velocity calibration test was carried out using the improved monitoring system. The results showed that under a constant seepage velocity, the use of the dual-tube structure enables faster cooling, and the cooling rate accelerates with an increase in the diameter of the inner tube. The use of the dual-tube structure can improve the sensitivity of the seepage evaluation index ζ_v to the seepage velocity. When the inner diameter increases, ζ_v becomes more sensitive to the seepage velocity.

A mobile-distributed seepage monitoring method based on FBG sensing technology is proposed in which the FBG sensors are not fixed. Instead, the positions of the measurement points are changed to improve the spatial resolution. Meanwhile, the use of the dual-tube structure in the presented monitoring system can improve its sensitivity.

Accurate and timely cost prediction is critical to the success of construction projects which is still facing challenges especially at the early stage. In the context of rapid development of machine learning technology and the massive cost data from historical projects, this paper aims to propose a novel cost prediction model based on historical data with improved performance when only limited information about the new project is available.

The proposed approach combines regression analysis (RA) and artificial neural network (ANN) to build a novel hybrid cost prediction model with the former as front-end prediction and the latter as back-end correction. Firstly, the main factors influencing the cost of building projects are identified through literature research and subsequently screened by principal component analysis (PCA). Secondly the optimal RA model is determined through multi-model comparison and used for front-end prediction. Finally, ANN is applied to construct the error correction model. The hybrid RA-ANN model was trained and tested with cost data from 128 completed construction projects in China.

The results show that the hybrid cost prediction model has the advantages of both RA and ANN whose prediction accuracy is higher than that of RA and ANN only with the information such as total floor area, height and number of floors.

(1) The most critical influencing factors of the buildings’ cost are found out by means of PCA on the historical data. (2) A novel hybrid RA-ANN model is proposed which proved to have the advantages of both RA and ANN with higher accuracy. (3) The comparison among different models has been carried out which is helpful to future model selection.

Although various concepts and techniques are introduced to the built environment to achieve a substantially efficient building production, the effective application of these methods in projects is of immense significance to the field of building construction. Among these initiatives, lean construction and building information modelling (BIM) are mainstream endeavours that share many common principles to improve the productivity of the built environment. This study aims to explore and explain how BIM-based integrated data management (IDM) facilitates the achievement of leanness in a built environment project.

This research is conducted through an ethnographic-action research that relies on the design-science approach and case study through a collaborative research project. As participants of the project, the researchers of this study cooperate with the practitioners to design the project approach and production workflows. Research data and evidence are obtained via participative observation, including direct observation, results of activities, unstructured meetings and self-analysis.

In this study, the project and production perspectives clarify the building design and production process, as well as analyse how BIM facilitates the achievement of leanness in building design and construction. BIM-based frameworks for IDM have been developed to handle miscellaneous information and data, as well as enhance multidisciplinary collaboration throughout the project life cycle. The role of the integrated BIM model as an information hub between the building design and building construction has been identified.

The project and production views of building and construction are used in this study because the research purpose is to link the BIM-based IDM to lean construction. Although this mixed approach can slightly undermine the theoretical foundation of this study, a substantially comprehensive understanding can be gained as well.

This study provides a new perspective to understand how BIM-based IDM contributes to lean construction.

This study provides new insights into IDM in a built environment project with project and production views and presents BIM-based frameworks for IDM to achieve lean construction through the BIM process.

Some papers have investigated the complex factors impacting building information modeling (BIM) application in prefabricated buildings (PBs), but few paid attention to their interaction relationships. Ignoring the fact that different factors are not isolated may lead to some key factors being overlooked without appropriate improvement strategies being proposed. This paper aims to analyze those factors and their inter-relationships, with the view to identify the critical factors and their interaction relationships so as to derive constructive strategies that would effectively facilitate BIM adoption in Chinese prefabrication.

First, factors influencing BIM application in prefabrication are extracted and collated by literature review, expert interview and analysis of PBs characteristics. Thereafter, an evaluation laboratory (decision-making trial and evaluation laboratory) and interpretive structural modeling are used to explore the relationships and hierarchy among the factors. Based on the degree of cause and centrality, critical factors are extracted and the interaction relationship are investigated.

The results show that BIM policies and standards for PBs are the main causal factors. The maturity of BIM software and BIM data interface for PBs, willingness to share data, the strategic goals of the enterprise, BIM law and BIM input and benefit are the main transitional factors while BIM staff and workflow, enterprise attitude, distribution of BIM liability and cooperation of participants are the main direct factors.

Based on the above findings, corresponding improvement strategies are proposed so as to promote BIM application in prefabrication and the rapid development of China’s PBs efficiently.

Building information modeling (BIM) is recognized as one of the technologies to upgrade the informatization level of the architecture engineering and construction (AEC) industry. However, the level of BIM implementation in the construction phase lags behind other phases of the project. Assessing the level of BIM implementation in the construction phase from a system dynamics (SD) perspective can comprehensively understand the interrelationship of factors in the BIM implementation system, thereby developing effective strategies to enhance BIM implementation during the construction phase. This study aims to develop a model to investigate the level of BIM implementation in the construction phase.

An SD model which covered technical subsystem, organizational subsystem, economic subsystem and environmental subsystem was developed based on questionnaire survey data and literature review. Data from China were used for model validation and simulation.

The simulation results highlight that, in China, from 2021 to 2035, the ratio of BIM implementation in the construction phase will rise from 48.8% to 83.8%, BIM model quality will be improved from 27.6% to 77.2%. The values for variables “BIM platform”, “organizational structure of BIM” and “workflow of BIM” at 2035 will reach 65.6%, 72.9% and 72.8%, respectively. And the total benefits will reach 336.5 billion yuan in 2035. Furthermore, the findings reveal five factors to effectively promote the level of BIM implementation in the construction phase, including: policy support, number of BIM standards, owners demand for BIM, investment in BIM and strategic support for BIM.

This study provides beneficial insights to effectively enhance the implementation level of BIM in the construction phase. Meanwhile, the model developed in this study can be used to dynamically and quantitatively assess the changes in the level of BIM implementation caused by a measure.

Prefabricated construction (PC) will play a vital role in the transformation and upgrading of the construction industry in the future. However, high capital cost is currently one of the biggest obstacles to the application and promotion of PC in China. Clarifying the factors that affect the PC cost from the perspectives of stakeholders and exploring key cost control paths help to achieve effective cost management, but few studies have paid enough attention to this. Therefore, this research aims to explore the critical cost influencing factors (CIFs) and critical stakeholders of PC based on stakeholder theories and propose corresponding strategies for different stakeholders to reduce the cost of PC.

Based on the stakeholder theory and social network theory, literature review and two rounds of expert interviews were used to obtain the stakeholder-associated CIFs and their mutual effects, then the consistency of the data was tested. After that, social network analysis was applied to identify the critical CIFs, critical interaction and key stakeholders in PC cost control and mine the influence conduction paths between CIFs.

The results reveal that the cognition and attitude of developer and relevant standards and codes are the most critical CIFs while the government, developer and contractor are crucial to the cost control of PC. The findings further suggest that measures should be taken to reduce the transaction costs of the developer, and the contractor ought to efficiently apply information technology. Moreover, the collaborative work between designer and manufacturer can avoid unnecessary cost consumption.

This research combines stakeholder management and cost management in PC for the first time and explores the effective cost control paths. The research results can contribute to clarifying the key points of cost management for different stakeholders and improving the cost performance of PC projects.

Seepage of the dam is an important safety problem, which may cause internal erosion of the structure. In the field of seepage monitoring in civil engineering, the distributed optical fiber sensing technology based on the temperature tracing method has been paid more attention due to its unique advantages of high sensitivity, good stability and high resolution. The purpose of this paper is to make a review of the existing related research, so as to facilitate the later scholars to understand and further study more systematically.

In this paper, three kinds of commonly used distributed fiber temperature measurement technologies are introduced. Based on the working principle, monitoring system, theoretical analysis, experimental research and engineering application of the fiber seepage monitoring technology, the present situation of dam seepage monitoring based on distributed fiber is reviewed in detail and their advantages and disadvantages are compared.

The thermal monitoring technology of seepage measurement depends on the accuracy of optical fiber temperature measurement (including the accuracy of the system and the rationality of the discrimination method), the correct installation of optical fiber and the quantitative analysis of temperature data. The accuracy of the current monitoring system can basically meet the existing measurement requirements, but the correct installation of optical fiber and the calibration of temperature data need to be further studied for different discrimination methods, and this field has great research value.

At present, there are many applications and research studies of optical fiber sensing in the field of structural health monitoring, and there are also reviews of related aspects. However, there is little or no review only in the field of seepage monitoring. This paper summarizes the research and application of optical fiber sensing in the field of seepage monitoring. The possibility of the gradient method to find its new prospect with the development of monitoring systems and the improvement of temperature resolution is discussed. The idea of extending the seepage monitoring method based on distributed optical fiber thermal monitoring technology to other monitoring fields is also given in the paper.

WO₃ particles were prepared by the sol-gel method. Tetraethyl silicate (TEOS) was used to obtain a SiO₂-coated WO₃ nanoparticle. Quantum chemical parameters of oleic acid, triethanolamine, glycerol and methyl pentane as dispersants were theoretically calculated. Tribological properties of SiO₂/WO₃ nanocomposite lubricant were carried out on an MRS-10A four-ball friction and wear tester.

The purpose of this study is to investigate the preparation and tribological properties of SiO₂/WO₃ nanocomposite lubricant.

The obtained SiO₂-coated WO₃ nanoparticle (nano-SiO₂/WO₃) with a particle size of about 70 nm. The calculated adsorption energy of triethanolamine on the surface of the steel ball is 554.6 eV, and triethanolamine is selected as the dispersant. The dispersion effect of SiO₂/WO₃ nanocomposite lubricant is good, which shows that triethanolamine oleate plays a good dispersion role in the preparation of lubricant, which is consistent with the calculation results of the adsorption capacity of dispersant. As a good auxiliary lubricant, SiO₂ can improve the tribological properties and wear resistance of WO₃.

Nanocomposite lubricants have been the focus of research in recent years, which could greatly reduce energy consumption. And the SiO₂/WO₃ exhibited excellent lubrication performance as a lubricant additive. The lubrication mechanism of SiO₂/WO₃ nanocomposite lubricant is the synergistic lubrication mechanism of friction film lubrication and antifriction bearing. This study could provide a certain reference for the practical application of nanocomposite lubricants.

The aims of this study are to conduct a systematic review of public–private partnership (PPP) studies published from 2009 to 2019, to compare the results with Ke et al. (2009) who reviewed the PPP literature published from 1998 to 2008, and to trace the evolution of the PPP knowledge in the past two decades. This study also presents the possible directions that the PPP research may go towards in the future, arguably.

This study carried out a top journal-based search to identify the quality PPP articles published from 2009 to 2019. A total of 12 top-tier construction journals were systematically searched in the database of web of science (WOS), from which 279 PPP articles were identified for review.

The number of the identified articles, the titles of the journals, institutions, the most cited papers, and prevalent research methods were analyzed and compared. The existing PPP studies in construction journals were classified into seven streams. Through analysis of the PPP research status and gaps, five future research directions were revealed.

This study contributes to the current body of knowledge by revealing the research trend of PPP from 2009 to 2019. It presents the change of PPP development trend in the past decade through comparison with Ke et al. (2009). It also reveals the major research streams and points out the directions that the PPP research may go towards in the future. Moreover, this study is helpful to the practice as well. It can enhance the practitioners' understanding of the PPP development in the past decade. In addition, it identified the research institutions contributing the most in the area of PPP, which may serve as valuable reference for practitioners to locate the best institutions for consultancy or collaboration.

The purpose of this paper is to propose a methodology to determine the designing parameters for solar powered high‐altitude, long‐endurance (HALE) unmanned aerial vehicles (UAV).

By depicting solar power distribution on earth, along with the efficiencies analysis of photo‐voltaic cells (P‐cell) and lithium‐sulfur battery (LS‐battery), the influence of energy to concept design parameters is analyzed first. Second, the lift efficiency is determined from ground to 20 km for HALE UAV. Third, the methodology to determine design parameters for HALE UAV is generalized by analyzing the carrying ability of some famous HALE UAVs, such as Zephyr, Helios, and so on.

Energy is the key constraint on design of HALE UAV. The questions about where HALE UAVs are capable of operating and how long they could work can be answered according to power density distribution on earth. The total mass of HALE UAV can be divided into two parts: one is the constant mass, the other is the mass increasing with area of wing. The total mass can be estimated by the former one; the later one plays an important role in estimating wing load in the designing process.

The only way to enhance carrying ability of HALE UAVs is to redistribute their wing load: lighter structure materials and a better method to fix P‐cell with lighter fundus are the key technologies to enhance HALE UAVs’ carrying ability. At current technological levels, it is not easy to design a UAV to achieve the aim of high‐altitude long‐endurance.

This paper presents a very efficient and convenient method to determine the designing parameters of HALE UAV.