This paper describes computational models of situated work in complex, heterogeneous dynamic systems that include humans, physical systems, computer agents and regulatory requirements, using aviation as the domain being examined but highlighting modeling principles generalizable to other domains. Work is defined formally here as purposeful activity acting on, and responding to, the environment as required by the situation. This work is performed by a team of automated and human agents, and involves both cognitive and physical activity. At its most atomic, work may be represented as actions that evaluate the current situation, and then act on the environment, as well as 'teamwork' actions and 'decision actions' whereby agents evaluate the situation to select the appropriate sets of actions (i.e. strategies). Work is thus a response to the situation, with strategies chosen in response to the physical environment, the allocation of responsibility within the team; and agent status including expertise, the demands on the agent, and resources available to the agent such as time and information. In addition, a description of the structures inherent to work is also used to organize the actions into an abstraction hierarchy: at the bottom are the resources and actions, but at higher levels of abstraction more aggregate functions provide descriptions that relate the detailed actions to the specific goals of the work. Historically, such models have been used qualitatively, but had a disconnect from computational modeling of situated behavior. Therefore, this paper details how they may be dynamically simulated to examine how work can be studied dynamically as situated within a dynamic environment driving, and responding to, agent activity.