No abstract

Traditional time-cost trade-off analysis assumes that the time and cost of an option within an activity are deterministic. However, in reality the time and cost are uncertain. Therefore, in analyzing the timecost trade-off problem, uncertainties should be considered when minimizing project duration or cost. Simulation techniques are useful for analyzing stochastic effects, but a general strategy/algorithm is needed to guide the analysis to obtain optimal solutions. This paper presents a hybrid approach that combines simulation techniques and genetic algorithms to solve the time-cost trade-off problem under uncertainty. The results show that genetic algorithms can be integrated with simulation techniques to provide an efficient and practical means of obtaining optimal project schedules while assessing the associated risks in terms of time and cost of a construction project. This new approach provides construction engineers with a new way of analyzing construction time/cost decisions in a more realistic manner. Historical time/cost data and available options to complete a project can be modeled, so that construction engineers can identify the best strategies to take to complete the project at minimum time and cost. Also, what-if scenarios can be explored to decide the desired/optimal time and/or cost in planning and executing project activities. FIG. 1. Typical Discrete Relationship between Time and Cost of Activity

Construction claims are considered by many project participants to be one of the most disruptive and unpleasant events of a project. Construction claims occur for various reasons. There is a need to understand the dynamic nature between construction claims and opportunistic bidding. An analytical model, the Claims Decision Model ͑CDM͒, based on ''game theory,'' was developed to study opportunistic bidding and construction claims. This model explains ͑1͒ how people behave during a potential or existing claiming situation, ͑2͒ how different claiming situations are related to opportunistic bidding behavior, and ͑3͒ what situations encourage or discourage opportunistic behavior. The results of this pilot study indicate that the equilibrium solution of a construction claim is to negotiate and settle, which concurs with most of the claim cases in the industry. The possible range of a negotiation settlement is obtained in this paper. The model provides the rationale for recent innovations to manage disputes. The model can also help project owners identify the possibility of opportunistic bidding, and can assist the project participants in analyzing construction claims.