Production Scheduling Optimization Of Precast Concrete Components Under Disturbances And Uncertainties In Prefabricated Housing Projects

The precast construction has achieved the large-scale development nowadays owing to the high environmental requirements,increased labor costs and strong policy supports from the governments.The research on precast construction primarily focused on technical problems in the architectural structures and on-site assembly,while gave limited consideration for the management improvement of precast supply chain.This results in the inherent advantages of precast construction in efficiency,quality and costs did not show in China.Further,multiple disturbances and uncertainties are ubiquitous and frequently happen in the precast supply chain.The original production scheduling will be invalid and hence impedes the on-time delivery,potentially resulting in operation chaos,double handling,prolonged durations,and increased supply chain costs.The essence of precast construction is the “intelligent manufacturing” in construction industry,and the systematic design of precast supply chain from the management view is strongly needed to promote the industrial development.Therefore,this research targets the production scheduling optimization of PCs in the precast housing construction considering the real production environment subject to multiple disturbances.This research hopes to reap the full benefits of off-site construction,and promote the theoretical and practical development of project logistics.This dissertation first conducts the literature review in the research areas of precast construction management,precast supply chain management,disturbance management,and production scheduling optimization.Some preliminary conclusions could be summarized that the past research was mainly focused on static scheduling using the mathematical optimization methods with simple assumptions.However,few of them have considered the real precast production environment and the prevention,evaluation & response to the disturbances derived from the production and the entire precast supply chain.Hence,this dissertation will target the aforementioned research gaps and conduct the following research:1.This dissertation modifies the traditional flow shop scheduling methods from the perspective of the entire supply chain,and proposes the advanced scheduling optimization model for precast production.In this model,the processes before production(i.e.molds manufacturing)and the storing,transportation activities after production are all considered apart from the direct production-related operations.Further,this model classifies the production processes into four categories based on the operation characteristics,including the interruptible & sequential activities,interruptible & parallel activities,uninterruptible & sequential activities without labor involvement,and uninterruptible & parallel activities with labor involvement.On this basis,the traditional calculation model for the completion time is modified according to operation classifications from the entire supply chain perspective.Finally,the real case study is conducted to verify the proposed model.Three scenarios of daytime transportation,night transportation,and all day transportation are designed to represent the real delivery situations.The results indicate that the proposed model enables 81.6% cost savings compared with the traditional scheduling methods,which suggests the superior and validity of the proposed model.2.The production scheduling subject to demand variability is conducted on the basis of the aforementioned static scheduling.The demand uncertainty frequently occurs owing to the construction schedule changes at construction sites in practice.This dissertation proposes a two-level rescheduling optimization model for precast production,and considers multiple practical production factors such as the multiple production lines,particular and shared mold usage.In this model,the rescheduling planning under the demand uncertainty is optimized from three steps: the selection of production lines,the priority evaluation of PCs,and the PCs rescheduling.The proposed rescheduling method is validated to induce smaller production adjustment costs in comparison with the traditional heuristic response methods.3.This dissertation integrates the optimization algorithms with the discrete simulation methods to develop a two-hierarchy optimization and simulation hybrid model,considering the uncertainty of operation durations in the practical production of PCs.This dissertation is one of the first to consider the operation uncertainties,and simulates the waiting-in-queue situations,the mold and labor resources constraints in the real-world production.These considerations ensure the applicability of the production scheduling optimization methods in practice,and achieve the trade-off of the two confliction goals of on-time delivery and minimum production costs.Finally,the real case study is conducted to verify the performance of the proposed model.The findings reveal that the proposed model facilitates the on-time delivery and minimizes the production costs simultaneously.This method will also provide the support for the decision makings on the configurations of mold and labor resources.4.This dissertation engages in the analysis of the multiple disturbances from the entire precast supply chain.The disturbances derived from the material suppliers,manufacturers,logistics,and customers are first summarized considering their possible causes.The knowledge-based precautions are also proposed in this part.This dissertation establishes the systematic disturbance evaluation model for the precast supply chain as one of the pioneers to consider multiple disturbances in precast construction.This model simulates the practical operations of the precast supply chain,and prioritizes the above four disturbance types at the early stage of disturbance management from the two perspectives of operational performance and economic profits.This can support the decision makings on disturbance precaution configurations in pursuit of full profits with the minimum investment.Additionally,the model can determine the upper bound of implementation costs for each prevention activity.The economic analysis prior to precaution implementations can facilitate the disturbance prevention management.To summarize,this dissertation conducts the study on the optimization of precast production scheduling.Four aspects are considered including the entire supply chain,demand variability,operation uncertainty,and the multiple disturbances from the precast supply chain,to achieve the production rescheduling,production simulation,and disturbances evaluations.The innovations include the whole supply chain view instead single consideration,the dynamic scheduling instead static scheduling,compensating for single assumptions considering practical environment,prior and systematic disturbance management,etc.The results could promote to fill the research gaps in the precast production scheduling.Moreover,the methodology of this study may facilitate the decision makings of researchers,practitioners,and managers on the precast production,precast supply chain and disturbance prevention management.