HEURISTIC SOLUTION FOR RESOURCE SCHEDULING FOR REPETITIVE CONSTRUCTION PROJECTS

misbe2011 Tracking Number 202

Construction project planning and control are core processes for building project management. In practice project time management is achieved by computer based techniques like Precedence Diagramming Method (PDM). PDM is a network-based planning instrument where building processes are represented topologically by means of an activity network. This is called Activity-Based Scheduling: activities, set of working operations performed by resources i.e. crews, are linked with each other by logical dependencies. Activity network is a time oriented building process model that provides construction planning. Time flow is modeled through the network by performing critical path calculation. Resource flow through project activities is not modeled in a direct way, i.e. resources are simply loaded to corresponding activities as an attribute or a label. Networking techniques represent the state of the art of construction project planning and scheduling in real life projects, but many researchers and practitioners claims that these techniques do not provide a suitable model for construction process, especially in repetitive projects. This is mainly because activity network is discrete while construction process is basically a continuous flow of working operation performed by specialized resources. A repetitive project is a multi–unit project where resources move through the various similar location of the project (e.g. multi – storey building, housing projects, highway projects), while a non-repetitive project is a building project that has a complex location breakdown structure and is mostly a set of one-off activities. Construction process modeling, for repetitive projects in particular, needs a more accurate model for resource flow through project activities. Location Based Scheduling is a resource oriented construction process model. In Location Based Scheduling working tasks, set of repetitive activities, are plotted on time / space chart using general principles of the Line of Balance (LOB). The essence of location based resource scheduling is the view of the movement of construction resources through the various project locations as a key to improve project performance. With the aim of improving resource scheduling in repetitive construction projects with Precedence Diagramming Method, an heuristic algorithm for repetitive activity scheduling process is presented (REPNET), based on a precedence network plotted on a resource–space chart. In repetitive-unit projects it is important that repetitive activities are planned in such a way as to enable timely movement of crews from one repetitive unit to the next, avoiding crew idle time. This is known as the “work continuity constraint” and its application during project planning can provide an effective resource utilization strategy that can lead to: maximization of the benefits from the learning curve effect for each crew; minimization of idle time of each crew; minimization of the off-on movement of crews on a project once work as begun. The heuristics of REPNET carry out resource timing in two phases: in the first phase as soon as possible project schedule is performed; in the second phase the REPNET algorithm search for resource scheduling optimization by minimization of resource idle time in repetitive activity performance. The work continuity constraint is relaxed in order to maintain the PDM minimum project duration. In this way, besides the classic time critical path, a resource critical path is detected. Space critical path can be highlighted if useful. The REPNET optimization algorithm is performed for a case study, the Galli Theatre refurbishment project, and flow-line view on a time – space chart is also plotted to verify project feasibility. Optimized project schedule is compared with original network scheduling and discussed.