Abstract. Off-site construction (OSC) methods have been widely adopted in the construction industry around the world. However, in a lot of developing countries, the application of OSC still lags behind. Although a number of research efforts have focused on identifying the OSC barriers, they are limited to qualitative descriptions, which lacks the understanding of the interrelationships among the barriers. To address this gap, this paper proposed a methodology for identifying the OSC barriers and their cause-effect relationships. The proposed methodology is composed of three phases: (1) a comprehensive literature review and in-depth interview with the OSC industry experts, (2) questionnaire survey and focus group discussion, and (3) grey DEMATEL analysis. The proposed methodology was applied in the context of China's construction industry. The results of the grey DEMATEL analysis provided the cause-effect relationships of the 35 identified OSC barriers, which indicated six important aspects be taken into deeper consideration, such as governmental regulations and incentives, OSC practices and experiences, as well as traditional construction method transformation. The outcomes of this study will support policymakers and OSC participants to identify the influencing OSC barriers and their interrelationships, as well as propose appropriate strategies for overcoming the barriers and broadening the OSC application. Keywords: off-site construction (OSC), barriers, relationship identification, grey DEMATEL analysis, developing countries, case of China. Conventional on-site construction methods have long been criticized for low productivity, poor quality and safety control, long construction time, and large amount of construction waste. Off-site construction (OSC) methods, as alternatives to the conventional on-site construction methods, have been widely adopted to move the work from construction sites to factories. Compared with the traditional construction methods, numerous benefits of using OSC have been recognized internationally. For example, OSC can utilize resources more effectively, reduce waste generation, improve health and safety performance, provide a controlled environment to maximize construction quality, better integrate supply chain, and enlarge economies of scale (Arif, Egbu 2010). OSC techniques have been progressively adopted in the construction industry around the world (Jaillon, Poon 2009). For example, the average share of precast concrete systems in the construction industry across the European Union is 20-25%, and the share is even higher in the northern European countries, which goes up to 40-50% (Polat 2010). However, despite the well-documented advantages of OSC, the development and popularization degree of OSC in developing countries is still at a low level. For example, the proportion of OSC projects accounted for only 2-3% in China's newly built buildings (Han et al. 2017) . There is, thus, a strong need to identify the obstacles for promoting the implementation of OSC in developing countries. A number of research efforts have been conducted to explore the barriers inhibiting the development and implementation of OSC (e.g. Arif, Egbu 2010; Mao et al. 2015; Mohamad Kamar et al. 2009; Zhang, Skitmore 2012) . However, despite the importance of the existing efforts, they have mostly focused on the experience and summary of pilot projects. Such research efforts are limited to qualitative descriptions without in-depth analyses, Engineering and Management, 2018, 24(5): 364-377 365 which are lack of sufficient accuracy and pertinence. Further studies are thus needed to not only identify the barriers hindering the use of OSC in construction, but also figure out the interrelationships and importance rankings of the barriers for providing better decision-making support to policymakers. Therefore, to address this gap, this paper proposed a methodology for identifying the OSC barriers and understanding their cause-effect interrelationships. The proposed methodology is based on the integration of three phases: (1) comprehensive literature review and in-depth interview with OSC industry experts, (2) questionnaire survey and focus group discussion, and (3) grey DEMA-TEL (Decision Making Trial and Evaluation Laboratory) analysis. The first two phases aim to identify a potential set of barriers and determine the relations among these barriers. The grey DEMATEL method aims to mathematically determine the degree of impacts of each barrier and their interrelationships, and to provide insights to policymakers for better improving the development of the OSC industry. This study applied the proposed methodology in the context of China's OSC industry. China is the world's largest construction market. Revealing the major barriers and their cause-effect relationships in China is especially important and relevant for the popularization of OSC in developing countries, and will add to the body of knowledge and provides more effective management strategies for stakeholders and decision makers.
REF applied grey DEMATEL in identifying barriers in off-site construction.
IDENTIFYING BARRIERS TO OFF-SITE CONSTRUCTION USING GREY DEMATEL APPROACH: CASE OF CHINA
Journal of Civil Engineering and Management
Engineering