Construction Schedule Risk Analysis

Project schedule has always been one of the major concerns in construction project management. The complexity of construction project is contributed by the substantial numbers of human and nonhuman factors. The interaction between factors leads to risks and finally causes delay, which reduce the economic and social value of projects dramatically. Therefore, how to propose effective measures to minimize the losses caused by schedule risks is the focus of current and future period of time. Existing researches have made some progress, but they are lack of dynamics, systematical and uncertainty analysis, making the results far from reality.Based on literature review and interview, this paper conducts a systematical and comprehensive risk analysis using complex system theory. Firstly, 79 schedule risks related to different stakeholders are identified for the development of social network, and 14 critical schedule risks are found by calculation. Secondly, a hybrid model combining system dynamics and discrete event system is built according to complex system theory. In addition, the effectiveness of the hybrid model is tested. Thirdly, 14 critical schedule risks and their combination are put into the hybrid model using AnyLogic and finally the change of schedule under different risks is attained.The research results show that:(1)social network analysis considers the interaction between schedule risks, which provides a evidence for identifying high-impact schedule risks;(2)the hybrid model comtaining both macro and mocro levels is more in line with the actual situation. Simulation results show that:(1)clients' slow decision making, tight project schedule, cash flow problem, accidents, approval problem, conflict, quality problems, inefficient communication, policy changes, planning and scheduling problems, variation, design changes, design errors and inclement weather have high impacts among risks;(2)risks may have a different degree of influence ranking when happen at different time;(3)the later the risk happens, the higher impact the risk would have;(4) the occurrence of accidents, cash flow problem, planning and scheduling problems, policy changes, approval problem, conflict, inefficient communication would lead to schedule delay, which would not be affacted by critical lines and non-critical lines;(5)the impacts of design errors, clients' variation order, variation, clients' slow decision making and quality problems on schedule are associated with the placement and the characteristic of the task at the placement;(6)the comprehensive impact of risks is greater than the sum of individual impact of risks. This paper would help project managers to have a better understanding of the uncertainty and interaction of schedule risks and lay a solid foundation for risk response.