Research On Rework Risk Of Prefabricated Construction Process

China is promoting the development of prefabricated construction to save labors,to improve quality,to develop construction sustainability and finally to achieve construction transformation.Prefabricated construction(PC)is a complex production system owing to its processes and the interactions between the internal and external system.The current researches and practices reflect that traditional cast-in-site construction management methods are not appropriate for PC and the development of PC is affected by many undefined factors.Effective planning and control methods to prefabricated housing still need to be improved,and many rework risks still exist.In order to accelerate the development of prefabricated housing,it is necessary to develop process optimization methods and rework risk management system which are suitable for PC.The study defined the rework risk,and the whole PC process was sort out in three aspects: supply chain,stakeholders and procedures which are very important to PC management.Based on literature review,expert interview and project records,PC rework risk were identified and classified at three stages: design,manufacturing and construction and an identification report was formed.There are 41 PC rework risk factors and they are classified into labor,material and equipment,workmanship,and environment.Based on rework risk identification,the PC rework risk impacts were analyzed in three dimensions,i.e.rework frequency,rework cost and rework time.Design has the largest rework risk in PC stages,and the manufacturing stage has significant impacts on costs.An expectation impact function was built to identify core tasks,which established foundation to build rework risk process optimization models and rework risk management system.13 core tasks are identified by the expectation impact function,including all the processes of design stage,20% processes of manufacturing stage,and 23.1% processes of construction stage.According to concurrent engineering and the character of PC,a DSM model was built to analyze the relationships of the whole PC process.Coupling tasks were identified and optimized to reduce coupling and iteration.A process optimization model based on rework risk was built according to rework risk communication.The model took minimized rework coordination cost and rework coordination time as optimization targets and optimize the procedures through DSM and adaptive genetic algorithm.A management system for PC rework risk were built by improving the lean project delivery system.The PC rework risk management system confirmed the management goals,environment,and stakeholders.The system also assessed the rework risk and the corresponding strategies including prevention,retention,reduction,transfer,etc.and monitoring measures are proposed according to the rework risk levels in order to guide the managers to standardize the PC management.A prefabricated project is taken as a case to demonstrate the aforementioned models and system.The basic information and rework problems were combed.Then the study optimized the construction process to reduce the impacts of rework costs and time.The rework risk and monitoring measures were analyzed to propose the corresponding strategies and management solutions.The results of the rework risk process optimization model and rework risk management system are verified to a certain extent.This study built a rework risk management system from the perspective of PC construction processes and improved PC management.This study introduced a new idea and perspective for PC management.The study also enriched the PC management system through applying intelligent optimization methods into PC management.The models and system can improve construction efficiency and establish foundation to predict PC rework risk.The rework risk of PC and the rework process optimization model proposed in this study can deepen the application of intelligent optimization methods in the construction process and expands the theories and methods of engineering risk management.the rework risk management system proposed in this study is valuable to guide the risk prediction of PC rework scientifically,improve the management efficiency of project construction,and enrich the management system of PC.