SIMULATION MODELING OF MULTIPLE PREEMPTIONS OF BARGES AND CRANES UNLOADING FILL FOR LAND RECLAMATION

Abstract

In construction simulation modeling, preemption is the interruption of activities in progress and the reallocation of their resources to other activities when triggering events occur, such as when geologic conditions change, or equipment fails. Modeling activity preemption correctly, however, is not trivial and requires specialized modeling elements such as those added to the STROBOSCOPE simulation system. These new preemption STROBOSCOPE functions and statements are first described and then applied to an example project where barges bring fill material for land reclamation to a harbor that has two berths and two cranes. When two barges are at the berths, each barge is unloaded by one crane. When only one barge is available, it is unloaded by both cranes working together and the remainder of its unloading time is halved. When a new barge arrives at the empty berth, the two cranes switch back to unloading one barge each, and the remaining unloading time for the first barge is doubled. The unloading of each barge can switch between using one and two cranes multiple times, with its remaining time to finish unloading either cut in half or doubled each time. The multiple activity preemptions caused by the changes in the number of cranes unloading each barge and the required adjustments in the barge’s remaining time to unload illustrate the challenging nature of activity preemption and the new STROBOSCOPE modeling capabilities.