Simulation is a powerful tool for construction process design and optimization. The results of a simulation provide detailed process information, such as resource utilization and idleness, operation bottlenecks, production rates and costs. To model and simulate construction operations, the attributes and characteristics of resources play a vital role in creating realistic simulation models. Many of the resource-dependent strategies and characteristics, however, are difficult, if not impossible, to model using existing simulation systems. COOPS-R is a new discrete-event simulation system for construction process modeling that focuses on resource flows of construction operations. Resources are modeled as objects (software entities that mimic the behavior of their real world counterparts) that flow through sub-tasks and interact with each other. This modeling paradigm provides the flexibility of modeling resource-dependent processing strategies. Due to the object-oriented modeling concept, COOPS-R is designed to provide an animated environment where the resource flows are explicitly and graphically represented.