Construction time-cost trade-off analysis using LP/IP hybrid method

Construction planners must select appropriate resources, including crew size, equipment, methods, and technologies, to perform the tasks of a construction project. In general, there is a trade-off between time and cost to complete a task-the less expensive the resources, the longer it takes. Using critical-pathmethod techniques, the overall project cost can be reduced by using less expensive resources for noncritical activities without impacting the duration. Furthermore planners usually need to adjust the selection of resources in order to shorten or lengthen the project duration. Finding optimal decisions is difficult and time-consuming considering the numbers of permutations involved. For example, a critical-path-method network with only eight activities, each with two options, will have 256 (28) alternatives. Exhaustive enumeration is not economically feasible even with very fast computers. This paper presents a new algorithm using linear and integer programming to efficiently obtain optimal resource selections that optimize time and cost of a construction project.