Project Delivery System Selection Model For Prefabricated Building

China's construction industry faces low labor productivity,increased labor costs,and engineering quality,safety,and environmental issues.Prefabricated buildings have the characteristics of improving labor productivity,saving energy,reducing pollution,etc.,and are a way for the construction industry to achieve transformation and upgrading.However,compared with traditional buildings,the construction process is more complicated,and more parties are involved.It is easy to have problems,such as disjoint design and construction,disordered organization and management,and many design changes.Therefore,it is critical to select the appropriate Project Delivery System for the project.The state advocates the use of general contracting mode for prefabricated buildings.Some scholars also believe that the general contracting mode of prefabricated buildings has many advantages,but it is not ideal in prefabricated buildings projects,and the proportion of projects adopting EPC mode is less.The main reasons are the immature development of the prefabricated building market,the lack of owner management experience and the imperfection of relevant policies.Therefore,selecting the most suitable Project Delivery System for prefabricated buildings should not only take into account the realization of the project objectives,but also the factors such as the level of regional prefabricated building development,the conditions of the owners and contractors,and the actual conditions of the project.This paper analyzes the contractual relationship,participation subject and characteristics of the DBB,DB and EPC models of the prefabricated building.In the DBB mode,the owner will subcontract the design and construction.The participation of the owners is high and the coordination relationship between the parties is more complicated.In the DB mode,after the owner completes part of the design work,the remaining design and construction tasks are handed over to the contractor,and the contractual relationship is relatively simple.In the EPC mode,the contractor undertakes the main design and construction tasks,and the participation of the owners is low.Different contracting modes apply differently and the problems are different.Based on literature review and expert interviews,this paper sorts out the factors affecting the selection of Project Delivery System of prefabricated building.Through questionnaire survey and correlation analysis,the indicators are screened.Finally,there are 6 major categories of 21 key influencing factors to establish the Project Delivery System decision-making indicator of prefabricated building.In this study,the entropy-weighted TOPSIS method is used to establish a decision model for the prefabricated building project delivery system.First,the indicators are divided into benefit indicators,cost indicators and objective indicators,and a database of established projects is established.Based on the expected value of the new project,the entropy weight method is used to calculate the index weight.Finally,the TOPSIS method is used to calculate the fit degree(matching degree)of each built project.The higher the degree,the better the overall performance of the existing projects,and the closer to the new projects.Finally,empirical analysis carried out.The demonstration projects of the DBB mode,DB mode,EPC mode,and a new project case are selected.The project related data is collected and some indicators are expertly scored.After calculation and analysis by the model,the results show that the project with DB mode has the highest degree,and it is recommended that the new project adopt DB mode.The analysis process and results of the case show that the model method is effective,and the calculation result of the model is useful for the decision of the contract model of the new project.