Two-stage profit optimization model for linear scheduling problems considering cash flow

Linear projects with repetitive activity in units are considered for investigation, and a two-stage profit optimization model for linear scheduling problems using constraint programming (CP) is proposed. To maintain work continuity for repetitive activities, interruption time and crew availability are addressed, and the optimization process is presented as follows: (1) optimizing the primary objective (project profit); (2) minimizing total interruption time, given the optimized value of the primary objective. Repetitive activities incur batches of budget expenditure according to activity implementation time. Cash flow and financial elements are therefore integrated into the optimization model. Owing to flexible CP techniques, contractors' requirements, such as credit limit and payment conditions, can be integrated simply into the model formulation for practical use. Lastly, a bridge example is adopted, with various constraints such as duration limitation, for scenario analysis. Consequently, the two-stage optimization process optimizes project profit, and also maximizes work continuity for linear scheduling problems.