Multi-objective optimisation of the level of prefabrication in construction projects

Off-site manufacturing (OSM) in construction projects is associated with significant advantages, including increased construction quality, productivity and efficiency. Even though off-site construction has been gaining increased attention from researchers and stakeholders in the construction industry, its adoption rate is still low. Unfortunately, such an approach has not been effectively examined to optimise the level of prefabrication adopted on projects. This research study aims to develop a framework for a multi-objective binary particle swarm optimisation (MOBPSO) tool to optimise the level of OSM adopted in a project. The construction systems and elements involved in a project are optimised for OSM to meet three objectives – namely, time, cost and embodied carbon dioxide. The proposed MOBPSO model is then applied to a case study in Brazil. The case study building is a social housing project that has the potential to utilise prefabricated concrete elements. The results indicate that a 20% improvement in time, a 30% improvement in cost and a 25% improvement in embodied carbon dioxide assessments can be realised when an optimisation approach is implemented.