Managing risk in modular construction using dimensional and geometric tolerance strategies

The accumulating effects of dimensional and geometric variability in modular construction have traditionally been managed using trial and error strategies and use of standardized tolerance values for similar stick-built construction scenarios. This approach often leads to site-fit rework and increase in project risk, since dimensional and geometric variability is more problematic in modular construction than stick-built construction due to module interfacing and erection on site. To address this persistent challenge within modular construction, this article presents a framework for an optimal design of dimensional and geometric variability through the use of comprehensive tolerance strategies by minimizing both fabrication costs and project risks. A methodology for developing tolerance strategies in modular construction is introduced and demonstrated using a case study on an industrial pipe chassis module. The proposed methodology links a structural analysis framework which aims to predict the performance of various assembly configurations to construction costs and various types of project risks. While structural analysis techniques mainly aim to predict failure modes and mechanisms of assemblies, this research aims to further enhance such models by adding risk and cost measures to the structural analysis models. This methodology aims to manage dimensional and geometric variability by the goal of reducing rework and decreasing project costs by providing a set of Pareto-optimal design solutions ranging from strict to lose tolerance control with respect to an amalgamated cost for module production and project risk. This allows the stakeholders, engineers and construction managers to better understand the trade-offs between fabrication costs and alignment, rework, safety, and transportation risks (in terms of cost) of modules, and therefore enhance the planning and design phases of modular construction. (C) 2017 Elsevier B.V. All rights reserved.