Network Planning And Completion Risk Research Based On Mixed Random Work Time

In increasingly complex engineering construction projects,the scope of influence of uncertainties on engineering projects is becoming wider and wider,and the degree of influence is increasing.The network plan based on mixed random working hours is more suitable for engineering projects.The calculation of random time parameters and random time periods is the scientific basis for project project optimization and progress management during implementation.By calculating the completion risk of each process and the completion risk of the project construction period,the project completion risk research is carried out to deal with and supervise the risk of completion of the project.The paper uses normal distribution,two-point distribution,triangular distribution,uniform distribution and Beta distribution to represent the process time in the network plan,and then calculates the time parameters of the mixed random network plan and conducts the completion risk research.Firstly,the average value of the probability distribution is determined according to the quota method.The distribution type and the upper and lower limits of the interval are determined by the experience of experts and construction personnel.The probability distribution of rain and snow weather is estimated according to the weather data of the past years,and a mixed random network plan is constructed accordingly;Secondly,based on the principle of small probability,the most probable time parameter model and the most probable period model of the mixed random network plan are established.The Monte Carlo method is used to calculate the most probable construction period,optimistic construction period and completion probability.The comparison of the cumulative completion probability curves is used to compare the randomized routes.The size of the construction period,in order to determine the critical lines and key processes;Then,through the dynamic analysis of the completion risk,calculate the possibility that each route becomes a key route and the possibility that each process becomes a key process,and then determine the process of key control and prevention;Finally,a case study of the overall construction proiect of the experimental building project is carried out to verify the calculation model based on the hybrid random network plan and the validity of the analysis of the completed risk model.Through the above research on the mixed random network plan,it provides a scientific basis for the optimization of the construction period of the project and the progress management during the implementation process,which is beneficial to reduce the completion risk in the construction and has good guidance and reference for the engineering practice application.