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Informal learning networks are critical to response to calls for practitioners to reskill and upskill in off-site construction projects. With the transition to the coronavirus disease 2019 (COVID-19) pandemic, social media-enabled online knowledge communities play an increasingly important role in acquiring and disseminating off-site construction knowledge. Proximity has been identified as a key factor in facilitating interactive learning, yet which type of proximity is effective in promoting online and offline knowledge exchange remains unclear. This study takes a relational view to explore the proximity-related antecedents of online and offline learning networks in off-site construction projects, while also examining the subtle differences in the networks' structural patterns.

Five types of proximity (physical, organizational, social, cognitive and personal) between projects members are conceptualized in the theoretical model. Drawing on social foci theory and homophily theory, the research hypotheses are proposed. To test these hypotheses, empirical case studies were conducted on two off-site construction projects during the COVID-19 pandemic. Valid relational data provided by 99 and 145 project members were collected using semi-structured interviews and sociometric questionnaires. Subsequently, multivariate exponential random graph models were developed.

The results show a discrepancy arise in the structural patterns between online and offline learning networks. Offline learning is found to be more strongly influenced by proximity factors than online learning. Specifically, physical, organizational and social proximity are found to be significant predictors of offline knowledge exchange. Cognitive proximity has a negative relationship with offline knowledge exchange but is positively related to online knowledge exchange. Regarding personal proximity, the study found that the homophily effect of hierarchical status merely emerges in offline learning networks. Online knowledge communities amplify the receiver effect of tenure. Furthermore, there appears to be a complementary relationship between online and offline learning networks.

Proximity offers a novel relational perspective for understanding the formation of knowledge exchange connections. This study enriches the literature on informal learning within project teams by revealing how different types of proximity shape learning networks across different channels in off-site construction projects.

The engineering construction standards in China play an important role in protecting the safety of the construction projects. They are the basic principles that standardize the construction activities and guarantee the quality of projects. However, there are many barriers that affect the adoption of the engineering construction standards. Therefore, the purpose of this paper is to investigate the barriers that challenge the adoption of the engineering construction standards in China.

The research reveals the barriers that affect the implementation of the engineering construction standards in China through a literature review. Then this study uses factor analysis to analyze 12 indices which we get from a questionnaire to build explanations from the results.

According to this paper, four main brands of uncorrelated variables are derived which are the main challenges in implementing the engineering construction standards in China: management barriers, policy barriers, knowledge barriers and market barriers. This paper gives a clear classification of the barriers that the enterprises face while adopting the engineering construction standards in China.

This paper makes a contribution to the understanding of the barriers that affect the adoption of the engineering construction standards in China.

This paper aims to introduce the weighted squared Euclidean distance between points in signal space, to improve the performance of the Wi-Fi indoor positioning. Nowadays, the received signal strength-based Wi-Fi indoor positioning, a low-cost indoor positioning approach, has attracted a significant attention from both academia and industry.

The local principal gradient direction is introduced and used to define the weighting function and an average algorithm based on k-means algorithm is used to estimate the local principal gradient direction of each access point. Then, correlation distance is used in the new method to find the k nearest calibration points. The weighted squared Euclidean distance between the nearest calibration point and target point is calculated and used to estimate the position of target point.

Experiments are conducted and the results indicate that the proposed Wi-Fi indoor positioning approach considerably outperforms the weighted k nearest neighbor method. The new method also outperforms support vector regression and extreme learning machine algorithms in the absence of sufficient fingerprints.

Weighted k nearest neighbor approach, support vector regression algorithm and extreme learning machine algorithm are the three classic strategies for location determination using Wi-Fi fingerprinting. However, weighted k nearest neighbor suffers from dramatic performance degradation in the presence of multipath signal attenuation and environmental changes. More fingerprints are required for support vector regression algorithm to ensure the desirable performance; and labeling Wi-Fi fingerprints is labor-intensive. The performance of extreme learning machine algorithm may not be stable.

The new weighted squared Euclidean distance-based Wi-Fi indoor positioning strategy can improve the performance of Wi-Fi indoor positioning system.

The received signal strength-based effective Wi-Fi indoor positioning system can substitute for global positioning system that does not work indoors. This effective and low-cost positioning approach would be promising for many indoor-based location services.

A novel Wi-Fi indoor positioning strategy based on the weighted squared Euclidean distance is proposed in this paper to improve the performance of the Wi-Fi indoor positioning, and the local principal gradient direction is introduced and used to define the weighting function.

Green specifications are some of the most important strategies for energy saving and describe the best practice in the field of sustainable construction. They have great effects on resource saving and environmental protection. The demand of sustainable construction has spurred the emerging and development of green specifications. However, there are many factors that affect the adoption of green specifications in China. Therefore, the purpose of this paper is to investigate the factors that affect the adoption of green specifications in China.

Based on the comprehensive literature review, a questionnaire survey has been conducted to with major stakeholders in construction area to identify issues concerning the adoption of green specifications in China. In total, 18 variables that affect the adoption of green specifications in were summarized. Then this study uses factor analysis and mean score method to analyze 18 variables which the authors get from the questionnaire.

Using the rank analysis and factor analysis, the variables have been ranked, analyzed and categorized into five independent factors. They are summarized as: green technology and techniques; awareness and attitude; policies and regulations; market; and economics. This study provides a variable reference for policy makers to put forward focused policies and incentives for green specifications implementation and industry practitioners to better understand of green specifications adoption in China.

This paper makes a contribution to the understanding of the factors that affect the adoption of the green specifications in China. The results can also contribute to better adoption of green specifications in other developing countries.

Job stressors have a considerable influence on workplace safety behaviors. However, the findings from previous studies regarding the effect of different types of job stressors have been contradictory. This is attributable to, among other factors, the effectiveness of job stressors varying with occupations and contexts. This study examines the effects of challenge and hindrance stressors on construction workers' informal safety communication at different levels of coworker relationships.

A three-dimensional framework of informal safety communication is adopted, including self-needed, citizenship and participatory safety communication. Stepwise regression analysis is then performed using questionnaire survey data collected from 293 construction workers in the Chinese construction industry.

The results demonstrate that both challenge and hindrance stressors are negatively associated with self-needed and citizenship safety communication, whereas their relationships with participatory safety communication are not significant. Meanwhile, the mitigation effects of the coworker relationship (represented by trustworthiness and accessibility) on the above negative impacts vary with the communication forms. Higher trustworthiness and accessibility enable workers faced with challenge stressors to actively manage these challenges and engage in self-needed safety communication. Similarly, trustworthiness promotes workers' involvement in self-needed and citizenship safety communication in the face of hindrance stressors, but accessibility is only effective in facilitating self-needed safety communication.

By introducing the job demands-resources theory and distinguishing informal safety communication into three categories, this study explains the negative effects of challenge and hindrance job stressors in complex and variable construction contexts and provides additional clues to the current inconsistent findings regarding this framework. The diverse roles of challenge and hindrance job stressors also present strong evidence for the need to differentiate between the types of informal safe communication.

The complexity of the construction standards affects the relevance between the system internal elements. Therefore, research on the systematic effect can make the construction activities get the optimum benefit. The purpose of this paper is to discuss these issues.

The research reveals the complex adaptive characteristic of the standard system by using system science theory, analyzes the emergent property mechanism of construction standard system, and provides the mathematical form of the system.

Finally, according to the complex characteristic of standard system, the structure modeling method of complex system is given. This paper provides a new method and theory bases for the construction standard system establishment.

Dynamic, open and non-linear can be considered as the core characteristics of construction standard system in structure, environment and behavior aspects, and that means the standard system is a typical complex system.