Propagation Characteristic Of Progress Payment Risk For Large Hydropower Project

A large hydropower project has a long construction period and a large amount of capital.The whole life cycle of the project construction is closely related to the progress payment.The progress payment is the essential step in the implementation of the construction contract and plays an important role in the construction.However,in the large hydropower project construction,great uncertainty,wide profession range,high construction difficulty,multi-stakeholder participants bring great difficulties to the progress payment management.More importantly,when the payment risk occurs and starts to propagate,it will affect many stakeholders and cause high schedule risk.Risk uncertainty includes two aspects: the uncertainty of risk itself and the uncertainty of risk propagation.This study focuses on the progress payment risk and its propagation characteristics of large hydropower project.The study includes four important research contents: the calculation of the progress payment risk,the research of the risk propagation within a project contractor,the research of the risk propagation among multi-stakeholder and project schedule risk caused by the risk propagation.The purpose of the study is to provide an important theoretical basis for cost risk control of the large project.The specific contents are presented as follows:(1)For the capital outflow and inflow,the uncertain factors that affect these two aspects are comprehensively analyzed.The uncertainty of capital outflow is considered from the fluctuation of unit price and the change of engineering quantity.The uncertainty of capital inflow is calculated by analyzing the subjective behavior of payment.Combined with uncertain capital outflow and inflow,a model of calculating the progress payment risk in the large hydropower project is established by using Monte Carlo simulation.The proposed model is applied to an actual hydropower project,and the feasibility of the model is verified.Then,the payment risk propagation and its impact are preliminarily analyzed,aiming at providing a foundation for in-depth exploration of the propagation characteristics of the payment risk.(2)The contractor is taken as the research object.A large number of historical cases of contractor cost management in hydropower project are collected and analyzed.The risk factors and risk propagation paths are extracted,and a project risk propagation network is constructed.Through analyzing the network structure,the characteristics of the heterogeneity and small world are found,and the reasons why the risk occurs quickly and is difficult to control are revealed.As the progress payment belongs to the project cost management,the project risk propagation network includes the risk factors and risk propagation relationships related to the contractor’s cost.Based on this network,we construct a payment risk propagation network that can adapt to the change of situation.The payment risk propagation network is transformed into a Bayesian network.Combined with the fuzzy set theory,an impact assessment model of payment risk on the contractor is established.The proposed model is applied to an actual contractor,the feasibility of the model is verified.The result shows that the risk probabilities of damaging the contractor’s image,cost overrun and construction accident are respectively 9.99%,42.70% and 16.40% under the influence of payment risk propagation.(3)The propagation characteristics of payment risk among multi-stakeholder are further explored.The payment risk occurs only if the stakeholders have the transaction relationships.We collect the project stakeholders and their transaction amounts.A transaction relationship network among stakeholders is built,which the stakeholders are regarded as the nodes of the network and the transaction relationships are regarded as the edges of the network.We analyze the risk propagation behavior,economic state and mutual influence of stakeholders,quantify the process of payment risk propagation among multiple parties,and construct a payment risk propagation model based on the transaction relationship network.Combined with an actual project,it is found that the propagation process of the payment risk includes three stages and the risk may exponentially break out;stakeholders’ risk-resisting ability has a great impact on the risk propagation result;the impact of the project organization structure on the risk propagation is explored.Although EPC contract has a high management concentration,the project organization network structure presents typical scale-free characteristic and the ability of resisting the risk propagation is weak.(4)The corresponding relationship between stakeholder and construction activity is analyzed.A coupling network of organization and construction activity is constructed based on the transaction relationship network,the project risk propagation network and the project schedule network.We analyze the multiple uncertainties in which the payment risk propagates from the organization network to the schedule network,establish a payment risk impact model based on the coupling network,and evaluate the impact of payment risk on project schedule risk.The model provides a novel method for exploring the risk propagation mechanism in the heterogeneous network.Combined with an actual project,the results show that the completion probability under the influence of payment risk propagation is only 38.3%,and the more construction activities are affected,the greater uncertainty of completing the project on schedule is.