NEW ZEALAND BUILT ENVIRONMENT RESEARCH SYMPOSIUM Shaping future directions for collaborative built environment research and practice in New Zealand REDUCING WASTE IN CONSTRUCTION THROUGH HIERARCHICAL CONTROL CONCEPTUAL MODELLING FRAMEWORK

Discrete-Event Simulation is an event-driven simulation in which a real dynamic process is imitated as it progresses over time. It has been recognized as a powerful technique for the quantitative analysis of complex construction operations. The two main DES strategies for modelling construction operations are Process Interaction (PI) and Activity Scanning (AS). Although each strategy has its own advantages and disadvantages, some researchers illustrated that AS is a more natural and effective strategy than PI for simulation modelling of construction operations. Nevertheless, neither PI nor AS are able to accurately represent a real system in terms of dispatching and resource allocation. This potentially avoids accurate assessment of waste from construction operations. Recently, a hybrid strategy combining features of both AS and PI, called Hierarchical Control Conceptual Modelling (HCCM) has been presented that uses hierarchical control structures as a more general, flexible and powerful tool to define DES models. On the other hand, dynamic Three Dimensional (3D) visualisation adds significant credibility to DES models by facilitating verification and validation. This is especially true in construction, where decision makers in the field are typically experts in their domain but are not generally proficient in simulation itself. In this regard, some research has integrated DES modelling and 3D visualisation so that (1) simulation and animation run concurrently and in a manner that allows interaction with the animation to affect the course of events in the simulation; and (2) simulation and animation run in the same virtual environment avoiding errors and misconception between the model and the animation. However, the potential of this technology to be applied into specific production problems such as reduction of production waste has received little attention. In this research, 3D visualisation is utilised for verification and validation purposes. The aim of this research is to introduce the HCCM framework for DES modelling in construction. Applying the HCCM framework to a DES model is visually demonstrated through a case study of waste reduction from construction operations. FlexSim, a powerful DES modelling package based on both PI and AS is utilised to model the construction operations as it enables visualizing and handling highly dynamic, complex systems. The control policies of the HCCM framework allows development of what if scenarios for very specific production problems in construction, enabling precise modelling of dispatching systems and resource allocations in a user friendly environment. 3D visualisation, mainly achieved by the use of dispatchers and transporters, enables decision makers to unambiguously understand production logic and so, better plan and control construction operations. Preliminary results demonstrate waste reduction from a construction case study.