ORSONI and KARADIMAS: MODELLING AND SIMULATION IN DESING-BUILD PROJECTS I.J. of SIMULATION Vol.7 No. 9 ISSN 1473-804x online, 1473-8031 print 1 MODELLING AND SIMULATION IN DESIGN-BUILD PROJECTS: CURRENT ISSUES AND CHALLENGES ALESSANDRA ORSONI NIKOLAOS V. KARADIMAS School of Business Information Management National Technical University of Athens Kingston University, Kingston Hill Multimedia Technology Laboratory Kingston upon Thames, Surrey, KT2 7LB Heroon Polytechneiou 9, United Kingdom Zografou Campus, 157 80 Athens, Greece A.Orsoni@kingston.ac.uk NKaradim@central.ntua.gr Abstract: The paper discusses the role of modelling and simulation techniques in large scale construction projects focusing on the opportunities and on the modelling challenges that are specific to this context of application. The paper argues that a methodology based on dynamic multi-process simulation models provides powerful decision support when assessing the performance implications of changes in the design and/or in the technology, as well as the impact of alternative courses of action during project execution. Dynamic multi- process simulation provides quantitative grounds for the understanding, analysis, and discussion among the project stakeholders, and creates the conditions for a concurrent engineering approach throughout the project’s lifecycle, starting from the early stages of conceptual design. A simulation-based study, based on actual data from a construction project, is presented in the paper to illustrate these benefits. Keywords: Construction, design-build projects, multi-process simulation, inter-dependent production processes INTRODUCTION The analysis of change in large-scale construction projects, and especially the assessment of its impact on performance, requires a great deal of shared process understanding and communication among the project stakeholders. Large-scale construction projects involve the interests of several parties, such as the owner, the general contractor, and the different specialty contractors. Each party, depending on the type of contract, has different objectives within the project. This diversification and fragmentation of tasks and goals makes it quite difficult to establish an absolute “optimum” for the project and makes it even more difficult to express it in terms of a single performance measure. Depending on the particular project and party of perspective, one aspect of performance may become critical to the success of the project, but in general the level of success achieved in a project can only be measured across multiple dimensions of performance (O’Connor and Miller, 1994). When dealing with complex applications, the introduction of design and technological changes impacts project performance at three levels: the system, the inter- system, and the whole project level. Specifically, the system level observes the effects of change within the system of introduction. The inter-system level tracks the effects as they ripple out to systems other than the one of first introduction. The whole project level captures the impact on the performance of the overall project. Prior research, based on extensive simulated scenario testing, has demonstrated that the impact of change can be accurately tracked at all three levels, across multiple dimensions of performance (Orsoni, 2000; Orsoni, 2001a; Orsoni 2001b; Slaughter and Orsoni, 2000). ASSESSING PROJECT PERFORMANCE IN THE PRESENCE OF CHANGE The complexity of large construction projects, and the multiplicity of parties and objectives involved, indicate that project performance is multi-attribute (O’Connor and Miller, 1994). While a number of different measures can be considered when analyzing the effects of project changes, for the purposes of this study a selection has been made to capture the performance impact of changes at the system, at the inter-system and at the whole project level. These measures include project duration, duration-based cost, cost of utilized resources, percentage resource utilization, and an index of workers’ exposure to dangerous conditions (or danger index). Specifically, the duration-based cost represents the total cost of the project, assuming that all of the resources are present on the construction site for the entire duration of their scope of activity within the project. The cost of utilized resources is the bare cost of performing all of the project activities and tasks, excluding the resources costs of delays and wait times introduced by process interdependencies (both at the system level and at the inter-system level). The percentage of resource