New Model to Minimize Cost and Time of Rework Due to Prefabricated Construction Errors

The problem of minimizing the cost and time of rework due to fabrication and assembly errors in prefabricated construction considering the spatial relationship between elements was revisited. The time required to remedy the element’s error was used as the basis to find optimal crew sizing and scheduling to minimize rework. Using the modeled time, two formulations, namely, a mixed integer linear programming (MILP) and mixed integer quadratically constrained programming (MIQCP) were derived. The latter formulation captured the impact of crew occupied space on the available space for adjacent crews. Furthermore, the impact of uncertainty in the estimated time demand for each zone was incorporated through robust optimization. Finally, a new objective function term was included to balance work demand in each zone to approach takt time scheduling. The formulations were applied on a typical building construction project to correct the locations of reinforced concrete columns with assembly errors. While the formulations provide direct crew sizing and scheduling results, the methodology can benefit from: (i) incorporating flow continuity within zones; (ii) including multiple objectives to capture aspects, such as sustainability; and (iii) estimating the terms of the time demand model from real data.