Research On Construction Period-Cost Optimization Of Railway Bridge Engineering Based On System Dynamics

With the improvement of China’s railway network,especially in the central and western regions,the construction of railways has entered a peak period.How to prevent the delays and cost overruns of railway projects is an important research direction of railway construction project management.The bridge is an important part of the railway.Its construction affects the construction period and cost of the entire railway construction project.This paper applies the system dynamics method to the construction period-cost optimization research of the railway bridge project,and carries out a lot of theoretical research,literature reading.Based on case analysis and on-site investigation,a system dynamics model with time-cost optimization is established.It will be provide an theoretical reference when project manger,from the perspective of overall cost and time issues,need to make time-cost optimization.The main research contents of this paper are as follows:First,the relevant theory will be described in detail.This paper introduces the main construction process and system dynamics concept of railway bridge construction,and expounds the superiority of applying system dynamics to the construction period-cost optimization research of railway bridge project and the modeling procedure based on system dynamics software VENSIM,which lays the foundation for the model establishment.Secondly,the main variables affecting the construction period and cost and the mechanism of their interaction are considered systematicly,according to the characteristics of construction period and cost,the system considers the main variables affecting the construction period and cost and the mechanism of their interaction.By combining the main factors affecting the construction technology level and construction management level of bridge construction technology,three subsystems are established: Duration subsystem,cost subsystem and construction process subsystem.The causal relationship graph and the stock flow graph are drawn and the equations of the relevant variables are written by analysis detailedly the relevant variables of the three subsystems.The related factors which affect the construction technology level and construction management are assigned and empowered by Delphi method and G1 method,to obtain the comprehensive influence coefficient of the relevant construction technology level and construction management level.According to the mutual relationship between the subsystems,the system dynamics model of the total railway bridge construction project duration-cost simulation is established.Finally,taking the construction project of the control project Lingwuxi Bridge in the Yinwu Passenger Project as an example,the simulation study of the railway bridge project duration-cost simulation model is carried out to verify the validity and rationality of the model.Based on the original construction organization design(cantilever casting),the construction period and cost curve of the cantilever pouring construction are simulated,which provides a reference for the manager to estimate the construction period and cost.On this basis,the construction period and cost optimization strategies were simulated。 Compared increaseing the construction time strategy with changing the construction process strategy,we can reached the following conclusions:(1)The overtime strategy can effectively shorten the construction time in the early stage of the project,but it will increase the construction.cost.(2)Before commencement of work,the construction unit can select the way of the combination of the cast-in-place process and the prefabricated simple-supported beam to design construction organization according to the construction period and cost requirements,so as to achieve the purpose of time-cost optimizationThe system dynamics model of the construction period-cost simulation of the railway bridge project established in this paper can provide reference for the construction period-cost simulation analysis of similar railway bridge projects,and has certain reference value for the railway bridge construction period cost management.