Optimization of Vertical Elevator Movements and Material Storage Locations for High-Rise Building Construction with Overtime Cost Effects

Abstract

In high-rise building construction in urban areas, completed floors used as material storage provide usable spaces to support construction activities. A binary mixed-integer linear programming (BMILP) problem has been formulated to optimize material storage cell use in lower completed floors by minimizing total material-handling and transportation costs, taking both horizontal and vertical movement paths into consideration. Frequent vertical material movements via elevator cause delay. Work overtime may induce extra site operation and other labor-related costs if storage is not well managed to exploit a elevator. To integrate overtime costs into an objective function for optimization, a compatible time dimension has been modeled so that actual material movement times and relevant time costs triggered by overtime can be optimized. A delivery work sequence is modeled and optimized for scheduling user requests. A numerical example for managing 10 material types in a 30-story building is given for illustration. The BMILP problem is solved by a standard branch-and-bound technique for global optimum solution.