Determination of float time for individual construction tasks using constraint-based discrete-event simulation

In this paper we propose a methodology which combines Forward and Backward Simulation in order to extend discrete-event simulation by the ability to calculate float times. In the case of Backward Simulation, the simulation starts at the virtual completion date of the construction project and runs backwards in time until the start date. To determine float times it is important that the task execution sequence is in the same order for forward and backward simulation. Consequently we present an extension to the simulation concept that controls the execution order of the tasks within the backward simulation. By combining the results of the forward and backward simulation, it is possible to determine float times for each task while taking into account resources. A comprehensive case study illustrates the application of this new approach. One result of this is the determination of detailed float times for each task using discrete-event simulation.